From 80d11d997c3bd78d470e01f47dc9ae4f56de1b61 Mon Sep 17 00:00:00 2001 From: belitex Date: Mon, 15 Oct 2018 20:44:24 +0800 Subject: [PATCH 01/44] translating by belitex: A sysadmin-s guide to containers --- sources/tech/20180827 A sysadmin-s guide to containers.md | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sources/tech/20180827 A sysadmin-s guide to containers.md b/sources/tech/20180827 A sysadmin-s guide to containers.md index a6529d8842..6acf9c2a45 100644 --- a/sources/tech/20180827 A sysadmin-s guide to containers.md +++ b/sources/tech/20180827 A sysadmin-s guide to containers.md @@ -1,3 +1,5 @@ +translating by belitex + A sysadmin's guide to containers ====== From 1a297c4363ad9d7de97b2c42610e079b26b09753 Mon Sep 17 00:00:00 2001 From: thecyanbird <2534930703@qq.com> Date: Mon, 15 Oct 2018 20:55:03 +0800 Subject: [PATCH 02/44] Create 20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md --- ...nduct and Not Everyone is Happy With it.md | 166 ++++++++++++++++++ 1 file changed, 166 insertions(+) create mode 100644 translated/talk/20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md diff --git a/translated/talk/20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md b/translated/talk/20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md new file mode 100644 index 0000000000..32a839ed81 --- /dev/null +++ b/translated/talk/20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md @@ -0,0 +1,166 @@ +Linux 拥有了新的行为准则，但是许多人都对此表示不满 +===== + +**Linux 内核有了新的行为准则Code of Conduct(CoC)。但在这条行为准则被签署以及发布仅仅 30 分钟之后，Linus Torvalds 就暂时离开了 Linux 内核的开发工作。因为新行为准则的作者那富有争议的过去，现在这件事成为了热点话题。许多人都对这新的行为准则表示不满。** + +如果你还不了解这件事，请参阅 [Linus Torvalds 对于自己之前的不良态度致歉并开始休假，以改善自己的行为态度][1] + +### Linux 内核开发遵守的新行为准则 + +Linux 内核开发者并不是以前没有需要遵守的行为准则，但是之前的[冲突准则code of conflict][2]现在被替换成了以“给内核开发社区营造更加热情，更方便他人参与的氛围”为目的的行为准则。 + +>“为营造一个开放并且热情的社区环境，我们，贡献者与维护者，许诺让每一个参与进我们项目和社区的人享受一个没有骚扰的体验。无关于他们的年纪，体型，身体残疾，种族，性别，性别认知与表达，社会经验，教育水平，社会或者经济地位，国籍，外表，人种，信仰，性认同和性取向。 + +你可以在这里阅读整篇行为准则 + +[Linux 行为准则][33] + +### Linus Torvalds 是被迫道歉并且休假的吗？ + +![Linus Torvalds 的道歉][3] + +这个新的行为准则由 Linus Torvalds 和 Greg Kroah-Hartman (仅次于 Torvalds 的二把手）签发。来自 Intel 的 Dan Williams 和来自 Facebook 的 Chris Mason 也是该准则的签署者。 + +如果我正确地解读了时间线，在签署这个行为准则的半小时之后，Torvalds [发送了一封邮件，对自己之前的不良态度致歉][4]。他同时宣布会进行休假，以改善自己的行为态度。 + +不过有些人开始阅读这封邮件的话外之音，并对如下文字报以特别关注： + +>**在这周，许多社区成员批评了我之前种种不解人意的行为。我以前在邮件里进行的，对他人轻率的批评是非专业以及不必要的**。这种情况在我将事情放在私人渠道处理的时候尤为严重。我理解这件事情的严重性，这是不好的行为，我对此感到十分抱歉。 + +他是否是因为新的行为准则被强迫做出道歉，并且决定休假，可以通过这几行来判断。这也可以让我们采取一些措施，避免 Torvalds 被新的行为准则伤害。 + +### 有关贡献者盟约作者 Coraline Ada Ehmke 的争议 + +Linux 的行为准则基于[贡献者盟约Contributor Convenant1.4 版本][5]。贡献者盟约[被上百个开源项目所接纳][6]，包括 Eclipse, Angular, Ruby, Kubernetes等项目。 + +贡献者盟约由 [Coraline Ada Ehmke][7] 创作，她是一个软件工程师，开源支持者，以及 [LGBT][8] 活动家。她对于促进开源世界的多样性做了显著的贡献。 + +Coraline 对于唯才是用的反对立场同样十分鲜明。[唯才是用meritocracy][9]这个词语源自拉丁文，本意为个人在系统内部的进步取决于他的“功绩”，例如智力水平，取得的证书以及教育程度。但[类似 Coraline 的活动家们认为][10]唯才是用是个糟糕的体系，因为他们只是通过人的智力产出来度量一个人，而并不重视他们的人性。 + +[![croraline meritocracy][11]][12] +图片来源：推特用户@nickmon1112 + +[Linus Torvalds 不止一次地说到，他在意的只是代码而并非写代码的人][13]。所以很明显，这忤逆了 Coraline 有关唯才是用体系的观点。 + +具体来说，Coraline 那被人关注饱受争议的过去，是一个关于 [Opal 项目][14]的事件。那是一个发生[在推特上的讨论][15]，Elia，来自意大利的 Opal 项目核心开发者说“（那些变性人）不接受现实才是问题所在。” + +Coraline 并没有参加讨论，也不是 Opal 项目的贡献者。不过作为 LGBT 活动家，她以 Elia 发表“冒犯变性人群体的发言”为由，[要求他退出 Opal 项目][16]。 Coraline 和她的支持者——他们给这个项目做过贡献，通过在 GitHub 仓库平台上冗长且激烈的争论，试图将 Elia——此项目的核心开发者移出项目。 + +虽然 Elia 并没有离开这个项目，不过 Opal 项目的维护者同意实行一个行为准则。这个行为准则就是 Coraline 不停向维护者们宣扬的，她那著名的贡献者盟约。 + +不过故事到这里并没有结束。贡献者盟约稍后被更改，[加入了一些针对 Elia 的新条款][17]。这些新条款将行为准则的管束范围扩展到公共领域。不过这些更改稍后[被维护者们标记为恶意篡改][18]。最后 Opal 项目摆脱了贡献者盟约，并用自己的行为准则取而代之。 + +这个例子非常好的说明了，某些被冒犯的少数人群——他们并没有给这个项目哪怕一点贡献，是怎样试图去驱逐这个项目的核心开发者的。 + +### 人们对于 Linux 新的行为准则的以及 Torvalds 道歉的反映。 + +Linux 行为准则以及 Torvalds 的道歉一发布，社交媒体与论坛上就开始盛传种种谣言与[推测][19]。虽然很多人对新的行为准则感到满意，但仍有些人认为这是 [SJW 尝试渗透 Linux 社区][20]的阴谋。 + +Caroline 发布的一个富有嘲讽意味的推特让争论愈发激烈。 + +>我迫不及待期待看到大批的人离开 Linux 社区的场景了。现在它以及被 SJW 的成员渗透了。哈哈哈哈。 +[pic.twitter.com/eFeY6r4ENv][21] +> +>— Coraline Ada Ehmke (@CoralineAda) [9 月 16 日, 2018][22] + +随着对于 Linux 行为准则的争论持续发酵，Carolaine 公开宣称贡献者盟约是一份政治文件。这并不能被那些试图将政治因素排除在开源项目之外的人所接收。 + +>有些人说贡献者盟约是一份政治文件，他们说的没错。 +> +>— Coraline Ada Ehmke (@CoralineAda) [9 月 16 日, 2018][23] + +Nick Monroe，一位自由记者，宣称 Linux 行为准则远没有表面上看上去那么简单。为了证明自己的观点，他挖掘出了 Coraline 的过去。如果您愿意，可以阅读以下材料。 + +>好啦，你们已经看到过几千次了。这是一个行为准则。 +> +>它包含了社会认同的正义行为。 +> +>不过它或许没有看上去来的那么简单。[pic.twitter.com/8NUL2K1gu2][24] +> +>— Nick Monroe (@nickmon1112) [9 月 17 日, 2018][25] + +Nick 并不是唯一一个反对 Linux 新的行为准则的人。[SJW][26] 的参与引发了更多的阴谋论猜测。 + +>我猜今天关于 Linux 的大新闻就是现在，Linux 内核被一个post meritocracy世界观下的行为准则给掌控了。 +> +>这个行为准则的宗旨看起来不错。不过在实际操作中，它们通常被当作 SJW 分子攻击他们不喜之人的工具。况且，很多人都被 SJW 分子所厌恶。 +> +> — Mark Kern (@Grummz) [September 17, 2018][27] + +虽然很多人对于 Torvalds 的道歉感到欣慰，仍有一些人在责备 Torvalds 的态度。 + +>我是不是唯一一个认为 Linus Torvalds 这十几年来的态度恰好就是 Linux 和开源“社区”特有的那种，居高临下，粗鲁，鄙视一切新人的行为作风？反正作为一个新用户，我从来没有在 Linux 社区里感受到自己是受欢迎的。 +> +>— Jonathan Frappier (@jfrappier) [9 月 17 日, 2018][28] + +还有些人并不能接受 Torvalds 的道歉。 + +>哦快看啊，一个喜欢辱骂他人的开源软件维护者，在十几年的恶行之后，终于承认了他的行为**可能**是不正确的。 +> +>我关注的那些人因为这件事都惊讶到平地摔，并且决定给他（Linus Torvalds）寄饼干来庆祝。 🙄🙄🙄 +> +>— Kelly Ellis (@justkelly_ok) [9 月 17 日, 2018][29] + +Torvalds 的道歉引起了广泛关注 ;) + +>我现在要在我的个人档案里写上”我不知是否该原谅 Linus Torvalds“ 吗？ +> +>— Verónica. (@maria_fibonacci) [9 月 17 日, 2018][30] + +不继续开玩笑了。有关 Linus 道歉的关注是由 Sharp 挑起的。他因为“恶劣的社区环境”于 2015 年退出了 Linux 内核的开发。 + +>现在我们要面对的问题是，这个成就 Linus，给予他肆意辱骂特权的社区能否迎来改变。不仅仅是 Linus 个人，Linux 内核开发社区也急需改变。 +> +>— Sage Sharp (@sagesharp) 9 月 17 日, 2018 + +### 你对于 Linux 行为准则怎么看？ + +如果你问我的观点，我认为目前社区的确是需要一个行为准则。它能指导人们尊重他人，不因为他人的种族，宗教信仰，国籍，政治观点（左派或者右派）而歧视，营造出一个积极向上的社区氛围。 + +对于这个事件，你怎么看？你认为这个行为准则能够帮助 Linux 内核的开发，或者说因为 SJW 成员们的加入，情况会变得更糟？ + +在 FOSS 里我们没有行为准则，不过我们都会持着文明友好的态度讨论问题。 + + via: https://itsfoss.com/linux-code-of-conduct/ + + 作者：[Abhishek Prakash][a] + 选题：[lujun9972](https://github.com/lujun9972) + 译者：[thecyanbird](https://github.com/thecyanbird) + 校对：[校对者ID](https://github.com/校对者ID) + + 本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + + [a]: https://itsfoss.com/author/abhishek/ + [1]: https://itsfoss.com/torvalds-takes-a-break-from-linux/ + [2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/CodeOfConflict?id=ddbd2b7ad99a418c60397901a0f3c997d030c65e + [3]: https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/09/linus-torvalds-apologizes.jpeg + [4]: https://lkml.org/lkml/2018/9/16/167 + [5]: https://www.contributor-covenant.org/version/1/4/code-of-conduct.html + [6]: https://www.contributor-covenant.org/adopters + [7]: https://en.wikipedia.org/wiki/Coraline_Ada_Ehmke + [8]: https://en.wikipedia.org/wiki/LGBT + [9]: https://en.wikipedia.org/wiki/Meritocracy + [10]: https://modelviewculture.com/pieces/the-dehumanizing-myth-of-the-meritocracy + [11]: https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/09/croraline-meritocracy.jpg + [12]: https://pbs.twimg.com/media/DnTTfi7XoAAdk08.jpg + [13]: https://arstechnica.com/information-technology/2015/01/linus-torvalds-on-why-he-isnt-nice-i-dont-care-about-you/ + [14]: https://opalrb.com/ + [15]: https://twitter.com/krainboltgreene/status/611569515315507200 + [16]: https://github.com/opal/opal/issues/941 + [17]: https://github.com/opal/opal/pull/948/commits/817321e27eccfffb3841f663815c17eecb8ef061#diff-a1ee87dafebc22cbd96979f1b2b7e837R11 + [18]: https://github.com/opal/opal/pull/948#issuecomment-113486020 + [19]: https://www.reddit.com/r/linux/comments/9go8cp/linus_torvalds_daughter_has_signed_the/ + [20]: https://snew.github.io/r/linux/comments/9ghrrj/linuxs_new_coc_is_a_piece_of_shit/ + [21]: https://t.co/eFeY6r4ENv + [22]: https://twitter.com/CoralineAda/status/1041441155874009093?ref_src=twsrc%5Etfw + [23]: https://twitter.com/CoralineAda/status/1041465346656530432?ref_src=twsrc%5Etfw + [24]: https://t.co/8NUL2K1gu2 + [25]: https://twitter.com/nickmon1112/status/1041668315947708416?ref_src=twsrc%5Etfw + [26]: https://www.urbandictionary.com/define.php?term=SJW + [27]: https://twitter.com/Grummz/status/1041524170331287552?ref_src=twsrc%5Etfw + [28]: https://twitter.com/jfrappier/status/1041486055038492674?ref_src=twsrc%5Etfw + [29]: https://twitter.com/justkelly_ok/status/1041522269002985473?ref_src=twsrc%5Etfw + [30]: https://twitter.com/maria_fibonacci/status/1041538148121997313?ref_src=twsrc%5Etfw + [31]: https://www.networkworld.com/article/2988850/opensource-subnet/linux-kernel-dev-sarah-sharp-quits-citing-brutal-communications-style.html + [32]: https://twitter.com/_sagesharp_/status/1041480963287539712?ref_src=twsrc%5Etfw +[33]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8a104f8b5867c682d994ffa7a74093c54469c11f From c709a3bbb70507682b573f99729b79c40617c9d4 Mon Sep 17 00:00:00 2001 From: thecyanbird <2534930703@qq.com> Date: Mon, 15 Oct 2018 21:00:13 +0800 Subject: [PATCH 03/44] Delete 20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md --- ...nduct and Not Everyone is Happy With it.md | 169 ------------------ 1 file changed, 169 deletions(-) delete mode 100644 sources/talk/20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md diff --git a/sources/talk/20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md b/sources/talk/20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md deleted file mode 100644 index 971a91f94f..0000000000 --- a/sources/talk/20180919 Linux Has a Code of Conduct and Not Everyone is Happy With it.md +++ /dev/null @@ -1,169 +0,0 @@ -thecyanbird translating - -Linux Has a Code of Conduct and Not Everyone is Happy With it -====== -**Linux kernel has a new code of conduct (CoC). Linus Torvalds took a break from Linux kernel development just 30 minutes after signing this code of conduct. And since **the writer of this code of conduct has had a controversial past,** it has now become a point of heated discussion. With all the politics involved, not many people are happy with this new CoC.** - -If you do not know already, [Linux creator Linus Torvalds has apologized for his past behavior and has taken a temporary break from Linux kernel development to improve his behavior][1]. - -### The new code of conduct for Linux kernel development - -Linux kernel developers have a code of conduct. It’s not like they didn’t have a code before, but the previous [code of conflict][2] is now replaced by this new code of conduct to “help make the kernel community a welcoming environment to participate in.” - -> “In the interest of fostering an open and welcoming environment, we as contributors and maintainers pledge to making participation in our project and our community a harassment-free experience for everyone, regardless of age, body size, disability, ethnicity, sex characteristics, gender identity and expression, level of experience, education, socio-economic status, nationality, personal appearance, race, religion, or sexual identity and orientation.” - -You can read the entire code of conduct on this commit page. - -[Linux Code of Conduct][33] - - -### Was Linus Torvalds forced to apologize and take a break? - -![Linus Torvalds Apologizes][3] - -The code of conduct was signed off by Linus Torvalds and Greg Kroah-Hartman (kind of second-in-command after Torvalds). Dan Williams of Intel and Chris Mason from Facebook were some of the other signees. - -If I have read through the timeline correctly, half an hour after signing this code of conduct, Torvalds sent a [mail apologizing for his past behavior][4]. He also announced taking a temporary break to improve upon his behavior. - -But at this point some people started reading between the lines, with a special attention to this line from his mail: - -> **This week people in our community confronted me about my lifetime of not understanding emotions**. My flippant attacks in emails have been both unprofessional and uncalled for. Especially at times when I made it personal. In my quest for a better patch, this made sense to me. I know now this was not OK and I am truly sorry. - -This particular line could be read as if he was coerced into apologizing and taking a break because of the new code of conduct. Though it could also be a precautionary measure to prevent Torvalds from violating the newly created code of conduct. - -### The controversy around Contributor Convent creator Coraline Ada Ehmke - -The Linux code of conduct is based on the [Contributor Covenant, version 1.4][5]. Contributor Convent has been adopted by hundreds of open source projects. Eclipse, Angular, Ruby, Kubernetes are some of the [many adopters of Contributor Convent][6]. - -Contributor Covenant has been created by [Coraline Ada Ehmke][7], a software developer, an open-source advocate, and an [LGBT][8] activist. She has been instrumental in promoting diversity in the open source world. - -Coraline has also been vocal about her stance against [meritocracy][9]. The Latin word meritocracy originally refers to a “system under which advancement within the system turns on “merits”, like intelligence, credentials, and education.” But activists like [Coraline believe][10] that meritocracy is a negative system where the worth of an individual is measured not by their humanity, but solely by their intellectual output. - -[![croraline meritocracy][11]][12] -Image credit: Twitter user @nickmon1112 - -Remember that [Linus Torvalds has repeatedly said that he cares about the code, not the person who writes it][13]. Clearly, this goes against Coraline’s view on meritocracy. - -Coraline has had a troubled incident in the past with a contributor of [Opal project][14]. There was a [discussion taking place on Twitter][15] where Elia, a core contributor to Opal project from Italy, said “(trans people) not accepting reality is the problem here”. - -Coraline was neither in the discussion nor was she a contributor to the Opal project. But as an LGBT activist, she took it to herself and [demanded that Elia be removed from the Opal Project][16] for his ‘views against trans people’. A lengthy and heated discussion took place on Opal’s GitHub repository. Coraline and her supporters, who never contributed to Opal, tried to coerce the moderators into removing Elia, a core contributor of the project. - -While Elia wasn’t removed from the project, Opal project maintainers agreed to put up a code of conduct in place. And this code of conduct was nothing else but Coraline’s famed Contributor Covenant that she had pitched to the maintainers herself. - -But the story didn’t end here. The Contributor Covenant was then modified and a [new clause added in order to get to Elia][17]. The new clause widened the scope of conduct in public spaces. This malicious change was [spotted by the maintainers][18] and they edited the clause. Opal eventually got rid of the Contributor Covenant and put in place its own guideline. - -This is a classic example of how a few offended people, who never contributed a single line of code to the project, tried to oust its core contributor. - -### People’s reaction on Linux Code of Conduct and Torvalds’ apology - -As soon as Linux code of conduct and Torvalds’ apology went public, Social Media and forums were rife with rumors and [speculations][19]. While many people appreciated this new development, there were some who saw a conspiracy by [SJW infiltrating Linux][20]. - -A sarcastic tweet by Caroline only fueled the fire. - -> I can’t wait for the mass exodus from Linux now that it’s been infiltrated by SJWs. Hahahah [pic.twitter.com/eFeY6r4ENv][21] -> -> — Coraline Ada Ehmke (@CoralineAda) [September 16, 2018][22] - -In the wake of the Linux CoC controversy, Coraline openly said that the Contributor Convent code of conduct is a political document. This did not go down well with the people who want the political stuff out of the open source projects. - -> Some people are saying that the Contributor Covenant is a political document, and they’re right. -> -> — Coraline Ada Ehmke (@CoralineAda) [September 16, 2018][23] - -Nick Monroe, a freelance journalist, dig up the past of Coraline in order to validate his claim that there is more to Linux CoC than meets the eye. You can go by the entire thread if you want. - -> Alright. You've seen this a million times before. It's a code of conduct blah blah blah -> -> that has social justice baked right into it. blah blah blah. -> -> But something is different about this. [pic.twitter.com/8NUL2K1gu2][24] -> -> — Nick Monroe (@nickmon1112) [September 17, 2018][25] - -Nick wasn’t the only one to disapprove of the new Linux CoC. The [SJW][26] involvement led to more skepticism. - -> I guess the big news in Linux today is that the Linux kernel is now governed by a Code of Conduct and a “post meritocracy” world view. -> -> In principle these CoCs look great. In practice they are abused tools to hunt people SJWs don’t like. And they don’t like a lot of people. -> -> — Mark Kern (@Grummz) [September 17, 2018][27] - -While there were many who appreciated Torvalds’ apology, there were a few who blamed Torvalds’ attitude: - -> Am I the only one who thinks Linus Torvalds attitude for decades was a prime contributors to how many of the condescending, rudes, jerks in Linux and open source "communities" behaved? I've never once felt welcomed into the Linux community as a new user. -> -> — Jonathan Frappier (@jfrappier) [September 17, 2018][28] - -And some were simply not amused with his apology: - -> Oh look, an abusive OSS maintainer finally admitted, after *decades* of abusive and toxic behavior, that his behavior *might* be an issue. -> -> And a bunch of people I follow are tripping all over themselves to give him cookies for that. 🙄🙄🙄 -> -> — Kelly Ellis (@justkelly_ok) [September 17, 2018][29] - -The entire Torvalds apology episode has raised a genuine concern ;) - -> Do we have to put "I don't/do forgive Linus Torvalds" in our bio now? -> -> — Verónica. (@maria_fibonacci) [September 17, 2018][30] - -Jokes apart, the genuine concern was raised by Sharp, who had [quit Linux Kernel development][31] in 2015 due to the ‘toxic community’. - -> The real test here is whether the community that built Linus up and protected his right to be verbally abusive will change. Linus not only needs to change himself, but the Linux kernel community needs to change as well. -> -> — Sage Sharp (@_sagesharp_) [September 17, 2018][32] - -### What do you think of Linux Code of Conduct? - -If you ask my opinion, I do think that a Code of Conduct is the need of the time. It guides people in behaving in a respectable way and helps create a positive environment for all kind of people irrespective of their race, ethnicity, religion, nationality and political views (both left and right). - -What are your views on the entire episode? Do you think the CoC will help Linux kernel development? Or will it deteriorate with the involvement of anti-meritocracy SJWs? - -We don’t have a code of conduct at It’s FOSS but let’s keep the discussion civil :) - --------------------------------------------------------------------------------- - -via: https://itsfoss.com/linux-code-of-conduct/ - -作者：[Abhishek Prakash][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://itsfoss.com/author/abhishek/ -[1]: https://itsfoss.com/torvalds-takes-a-break-from-linux/ -[2]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/CodeOfConflict?id=ddbd2b7ad99a418c60397901a0f3c997d030c65e -[3]: https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/09/linus-torvalds-apologizes.jpeg -[4]: https://lkml.org/lkml/2018/9/16/167 -[5]: https://www.contributor-covenant.org/version/1/4/code-of-conduct.html -[6]: https://www.contributor-covenant.org/adopters -[7]: https://en.wikipedia.org/wiki/Coraline_Ada_Ehmke -[8]: https://en.wikipedia.org/wiki/LGBT -[9]: https://en.wikipedia.org/wiki/Meritocracy -[10]: https://modelviewculture.com/pieces/the-dehumanizing-myth-of-the-meritocracy -[11]: https://4bds6hergc-flywheel.netdna-ssl.com/wp-content/uploads/2018/09/croraline-meritocracy.jpg -[12]: https://pbs.twimg.com/media/DnTTfi7XoAAdk08.jpg -[13]: https://arstechnica.com/information-technology/2015/01/linus-torvalds-on-why-he-isnt-nice-i-dont-care-about-you/ -[14]: https://opalrb.com/ -[15]: https://twitter.com/krainboltgreene/status/611569515315507200 -[16]: https://github.com/opal/opal/issues/941 -[17]: https://github.com/opal/opal/pull/948/commits/817321e27eccfffb3841f663815c17eecb8ef061#diff-a1ee87dafebc22cbd96979f1b2b7e837R11 -[18]: https://github.com/opal/opal/pull/948#issuecomment-113486020 -[19]: https://www.reddit.com/r/linux/comments/9go8cp/linus_torvalds_daughter_has_signed_the/ -[20]: https://snew.github.io/r/linux/comments/9ghrrj/linuxs_new_coc_is_a_piece_of_shit/ -[21]: https://t.co/eFeY6r4ENv -[22]: https://twitter.com/CoralineAda/status/1041441155874009093?ref_src=twsrc%5Etfw -[23]: https://twitter.com/CoralineAda/status/1041465346656530432?ref_src=twsrc%5Etfw -[24]: https://t.co/8NUL2K1gu2 -[25]: https://twitter.com/nickmon1112/status/1041668315947708416?ref_src=twsrc%5Etfw -[26]: https://www.urbandictionary.com/define.php?term=SJW -[27]: https://twitter.com/Grummz/status/1041524170331287552?ref_src=twsrc%5Etfw -[28]: https://twitter.com/jfrappier/status/1041486055038492674?ref_src=twsrc%5Etfw -[29]: https://twitter.com/justkelly_ok/status/1041522269002985473?ref_src=twsrc%5Etfw -[30]: https://twitter.com/maria_fibonacci/status/1041538148121997313?ref_src=twsrc%5Etfw -[31]: https://www.networkworld.com/article/2988850/opensource-subnet/linux-kernel-dev-sarah-sharp-quits-citing-brutal-communications-style.html -[32]: https://twitter.com/_sagesharp_/status/1041480963287539712?ref_src=twsrc%5Etfw -[33]: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8a104f8b5867c682d994ffa7a74093c54469c11f From cafcbaa0523e00d37d2883abcb121b46154ea741 Mon Sep 17 00:00:00 2001 From: thecyanbird <2534930703@qq.com> Date: Mon, 15 Oct 2018 21:09:54 +0800 Subject: [PATCH 04/44] thecyanbird translating --- ... To Record Your Terminal And Generate Animated Gif Images.md | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sources/tech/20181005 Terminalizer - A Tool To Record Your Terminal And Generate Animated Gif Images.md b/sources/tech/20181005 Terminalizer - A Tool To Record Your Terminal And Generate Animated Gif Images.md index 26d1941cc1..7b77a9cf73 100644 --- a/sources/tech/20181005 Terminalizer - A Tool To Record Your Terminal And Generate Animated Gif Images.md +++ b/sources/tech/20181005 Terminalizer - A Tool To Record Your Terminal And Generate Animated Gif Images.md @@ -1,3 +1,5 @@ +thecyanbird translating + Terminalizer – A Tool To Record Your Terminal And Generate Animated Gif Images ====== This is know topic for most of us and i don’t want to give you the detailed information about this flow. Also, we had written many article under this topics. From c7e00f9d275eb807a131975d27064a61d1477c50 Mon Sep 17 00:00:00 2001 From: "Xingyu.Wang" Date: Mon, 15 Oct 2018 23:00:39 +0800 Subject: [PATCH 05/44] PRF:20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md @FSSlc --- ... And Mouse, But Not The Screen In Linux.md | 55 +++++++++++++------ 1 file changed, 37 insertions(+), 18 deletions(-) diff --git a/translated/tech/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md b/translated/tech/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md index 3a0a0592cc..9b0c6608dd 100644 --- a/translated/tech/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md +++ b/translated/tech/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md @@ -3,33 +3,38 @@ ![](https://www.ostechnix.com/wp-content/uploads/2017/09/Lock-The-Keyboard-And-Mouse-720x340.jpg) -我四岁的侄女是个好奇的孩子，她非常喜爱“阿凡达”电影，当阿凡达电影在播放时，她是如此的专注，好似眼睛粘在了屏幕上。但问题是当她观看电影时，她经常会碰到键盘上的某个键或者移动了鼠标，又或者是点击了鼠标的按钮。有时她非常意外地按了键盘上的某个键，从而将电影关闭或者暂停了。所以我就想找个方法来将键盘和鼠标都锁住，但屏幕不会被锁住。幸运的是，我在 Ubuntu 论坛上找到了一个完美的解决方法。假如在你正看着屏幕上的某些重要的事情时，你不想让你的小猫或者小狗在你的键盘上行走，或者让你的孩子在键盘上瞎搞一气，那我建议你试试 **xtrlock** 这个工具。它很简单但非常实用，你可以锁定屏幕的显示直到用户在键盘上输入自己设定的密码（译者注：就是用户自己的密码，例如用来打开屏保的那个密码，不需要单独设定）。在这篇简单的教程中，我将为你展示如何在 Linux 下锁住键盘和鼠标，而不锁掉屏幕。这个技巧几乎可以在所有的 Linux 操作系统中生效。 +我四岁的侄女是个好奇的孩子，她非常喜爱“阿凡达”电影，当阿凡达电影在播放时，她是如此的专注，好似眼睛粘在了屏幕上。但问题是当她观看电影时，她经常会碰到键盘上的某个键或者移动了鼠标，又或者是点击了鼠标的按钮。有时她非常意外地按了键盘上的某个键，从而将电影关闭或者暂停了。所以我就想找个方法来将键盘和鼠标都锁住，但屏幕不会被锁住。幸运的是，我在 Ubuntu 论坛上找到了一个完美的解决方法。假如在你正看着屏幕上的某些重要的事情时，你不想让你的小猫或者小狗在你的键盘上行走，或者让你的孩子在键盘上瞎搞一气，那我建议你试试 **xtrlock** 这个工具。它很简单但非常实用，你可以锁定屏幕的显示直到用户在键盘上输入自己设定的密码（LCTT 译注：就是用户自己的密码，例如用来打开屏保的那个密码，不需要单独设定）。在这篇简单的教程中，我将为你展示如何在 Linux 下锁住键盘和鼠标，而不锁掉屏幕。这个技巧几乎可以在所有的 Linux 操作系统中生效。 ### 安装 xtrlock xtrlock 软件包在大多数 Linux 操作系统的默认软件仓库中都可以获取到。所以你可以使用你安装的发行版的包管理器来安装它。 在 **Arch Linux** 及其衍生发行版中，运行下面的命令来安装它： + ``` $ sudo pacman -S xtrlock ``` 在 **Fedora** 上使用： + ``` $ sudo dnf install xtrlock ``` -在 **RHEL, CentOS** 上使用： +在 **RHEL、CentOS** 上使用： + ``` $ sudo yum install xtrlock ``` 在 **SUSE/openSUSE** 上使用： + ``` $ sudo zypper install xtrlock ``` -在 **Debian, Ubuntu, Linux Mint** 上使用： +在 **Debian、Ubuntu、Linux Mint** 上使用： + ``` $ sudo apt-get install xtrlock ``` @@ -38,41 +43,50 @@ $ sudo apt-get install xtrlock 安装好 xtrlock 后，你需要根据你的选择来创建一个快捷键，通过这个快捷键来锁住键盘和鼠标。 -在 **/usr/local/bin** 目录下创建一个名为 **lockkbmouse** 的新文件： +（LCTT 译注：译者在自己的系统（Arch + Deepin）中发现这里的到下面创建快捷键的部分可以不必做，依然生效。） + +在 `/usr/local/bin` 目录下创建一个名为 `lockkbmouse` 的新文件： + ``` $ sudo vi /usr/local/bin/lockkbmouse ``` 然后将下面的命令添加到这个文件中： + ``` #!/bin/bash sleep 1 && xtrlock ``` + 保存并关闭这个文件。 然后使用下面的命令来使得它可以被执行： + ``` $ sudo chmod a+x /usr/local/bin/lockkbmouse ``` 接着，我们就需要创建快捷键了。 +#### 创建快捷键 + **在 Arch Linux MATE 桌面中** -依次点击 **System -> Preferences -> Hardware -> keyboard Shortcuts** +依次点击 “System -> Preferences -> Hardware -> keyboard Shortcuts” -然后点击 **Add** 来创建快捷键。 +然后点击 “Add” 来创建快捷键。 ![][2] -首先键入你的这个快捷键的名称，然后将下面的命令填入命令框中，最后点击 **Apply** 按钮。 +首先键入你的这个快捷键的名称，然后将下面的命令填入命令框中，最后点击 “Apply” 按钮。 + ``` bash -c "sleep 1 && xtrlock" ``` ![][3] -为了能够给这个快捷键赋予快捷方式，需要选中它或者双击它然后输入你选定的快捷键组合，例如我使用 **Alt+k** 这组快捷键。 +为了能够给这个快捷键赋予快捷方式，需要选中它或者双击它然后输入你选定的快捷键组合，例如我使用 `Alt+k` 这组快捷键。 ![][4] @@ -80,16 +94,17 @@ bash -c "sleep 1 && xtrlock" **在 Ubuntu GNOME 桌面中** -依次进入 **System Settings -> Devices -> Keyboard**，然后点击 **+** 这个符号。 +依次进入 “System Settings -> Devices -> Keyboard”，然后点击 “+” 这个符号。 + +键入你快捷键的名称并将下面的命令加到命令框里面，然后点击 “Add” 按钮。 -键入你快捷键的名称并将下面的命令加到命令框里面，然后点击 **Add** 按钮。 ``` bash -c "sleep 1 && xtrlock" ``` ![][5] -接下来为这个新建的快捷键赋予快捷方式。我们只需要选择或者双击 **“Set shortcut”** 这个按钮就可以了。 +接下来为这个新建的快捷键赋予快捷方式。我们只需要选择或者双击 “Set shortcut” 这个按钮就可以了。 ![][6] @@ -97,7 +112,7 @@ bash -c "sleep 1 && xtrlock" ![][7] -输入你选定的快捷键组合，例如我使用 **Alt+k**。 +输入你选定的快捷键组合，例如我使用 `Alt+k`。 ![][8] @@ -113,23 +128,26 @@ bash -c "sleep 1 && xtrlock" ### 将键盘和鼠标解锁 -要将键盘和鼠标解锁，只需要输入你的密码然后敲击“Enter”键就可以了，在输入的过程中你将看不到密码。只需要输入然后敲 `ENTER` 键就可以了。在你输入了正确的密码后，鼠标和键盘就可以再工作了。假如你输入了一个错误的密码，你将听到警告声。按 **ESC** 来清除输入的错误密码，然后重新输入正确的密码。要去掉未完全输入完的密码中的一个字符，只需要按 **BACKSPACE** 或者 **DELETE** 键就可以了。 +要将键盘和鼠标解锁，只需要输入你的密码然后敲击回车键就可以了，在输入的过程中你将看不到密码。只需要输入然后敲回车键就可以了。在你输入了正确的密码后，鼠标和键盘就可以再工作了。假如你输入了一个错误的密码，你将听到警告声。按 `ESC` 来清除输入的错误密码，然后重新输入正确的密码。要去掉未完全输入完的密码中的一个字符，只需要按 `BACKSPACE` 或者 `DELETE` 键就可以了。 ### 要是我被永久地锁住了怎么办？ -以防你被永久地锁定了屏幕，切换至一个 TTY（例如 CTRL+ALT+F2）然后运行： +以防你被永久地锁定了屏幕，切换至一个 TTY（例如 `CTRL+ALT+F2`）然后运行： + ``` $ sudo killall xtrlock ``` -或者你还可以使用 **chvt** 命令来在 TTY 和 X 会话之间切换。 +或者你还可以使用 `chvt` 命令来在 TTY 和 X 会话之间切换。 例如，如果要切换到 TTY1，则运行： + ``` $ sudo chvt 1 ``` 要切换回 X 会话，则键入： + ``` $ sudo chvt 7 ``` @@ -137,6 +155,7 @@ $ sudo chvt 7 不同的发行版使用了不同的快捷键组合来在不同的 TTY 间切换。请参考你安装的对应发行版的官方网站了解更多详情。 如果想知道更多 xtrlock 的信息，请参考 man 页： + ``` $ man xtrlock ``` @@ -145,7 +164,7 @@ $ man xtrlock **资源：** - * [**Ubuntu 论坛**][10] +* [**Ubuntu 论坛**][10] -------------------------------------------------------------------------------- @@ -154,7 +173,7 @@ via: https://www.ostechnix.com/lock-keyboard-mouse-not-screen-linux/ 作者：[SK][a] 选题：[lujun9972](https://github.com/lujun9972) 译者：[FSSlc](https://github.com/FSSlc) -校对：[校对者ID](https://github.com/校对者ID) +校对：[wxy](https://github.com/wxy) 本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 @@ -167,5 +186,5 @@ via: https://www.ostechnix.com/lock-keyboard-mouse-not-screen-linux/ [6]:http://www.ostechnix.com/wp-content/uploads/2018/01/set-shortcut-key-1.png [7]:http://www.ostechnix.com/wp-content/uploads/2018/01/set-shortcut-key-2.png [8]:http://www.ostechnix.com/wp-content/uploads/2018/01/set-shortcut-key-3.png -[9]:http://www.ostechnix.com/wp-content/uploads/2018/01/xtrlock-1.png +[9]:http://www.ostechnix.com/wp-content/uploads/2018/01/xtrclock-1.png [10]:https://ubuntuforums.org/showthread.php?t=993800 From e497745c703489f326dd3ff8df548c1c2c9e58a7 Mon Sep 17 00:00:00 2001 From: "Xingyu.Wang" Date: Mon, 15 Oct 2018 23:00:57 +0800 Subject: [PATCH 06/44] PUB:20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md @FSSlc https://linux.cn/article-10119-1.html --- ...To Lock The Keyboard And Mouse, But Not The Screen In Linux.md | 0 1 file changed, 0 insertions(+), 0 deletions(-) rename {translated/tech => published}/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md (100%) diff --git a/translated/tech/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md b/published/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md similarity index 100% rename from translated/tech/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md rename to published/20180817 How To Lock The Keyboard And Mouse, But Not The Screen In Linux.md From d67b663d79cadcf8294d6cbcf512ceb1e6495f5a Mon Sep 17 00:00:00 2001 From: lctt-bot Date: Mon, 15 Oct 2018 17:00:22 +0000 Subject: [PATCH 07/44] Revert "[Translating] Know Your Storage- Block, File - Object" This reverts commit 8ab0b6ccd7fb6da546290ec9a663ee23f4ac8a84. --- sources/tech/20180911 Know Your Storage- Block, File - Object.md | 1 - 1 file changed, 1 deletion(-) diff --git a/sources/tech/20180911 Know Your Storage- Block, File - Object.md b/sources/tech/20180911 Know Your Storage- Block, File - Object.md index 186b41d41a..24f179d9d5 100644 --- a/sources/tech/20180911 Know Your Storage- Block, File - Object.md +++ b/sources/tech/20180911 Know Your Storage- Block, File - Object.md @@ -1,4 +1,3 @@ -translating by name1e5s Know Your Storage: Block, File & Object ====== From e1ebeb8486560ec920a217bb5488f084f18729c5 Mon Sep 17 00:00:00 2001 From: darksun Date: Tue, 16 Oct 2018 08:50:21 +0800 Subject: [PATCH 08/44] =?UTF-8?q?=E9=80=89=E9=A2=98:=20How=20To=20Browse?= =?UTF-8?q?=20And=20Read=20Entire=20Arch=20Wiki=20As=20Linux=20Man=20Pages?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...ead Entire Arch Wiki As Linux Man Pages.md | 151 ++++++++++++++++++ 1 file changed, 151 insertions(+) create mode 100644 sources/tech/20181015 How To Browse And Read Entire Arch Wiki As Linux Man Pages.md diff --git a/sources/tech/20181015 How To Browse And Read Entire Arch Wiki As Linux Man Pages.md b/sources/tech/20181015 How To Browse And Read Entire Arch Wiki As Linux Man Pages.md new file mode 100644 index 0000000000..fe61f32dda --- /dev/null +++ b/sources/tech/20181015 How To Browse And Read Entire Arch Wiki As Linux Man Pages.md @@ -0,0 +1,151 @@ +How To Browse And Read Entire Arch Wiki As Linux Man Pages +====== +![](https://www.ostechnix.com/wp-content/uploads/2018/10/arch-wiki-720x340.jpg) + +A while ago, I wrote a guide that described how to browse the Arch Wiki from your Terminal using a command line script named [**arch-wiki-cli**][1]. Using this script, anyone can easily navigate through entire Arch Wiki website and read it with a text browser of your choice. Obviously, an active Internet connection is required to use this script. Today, I stumbled upon a similar utility named **“Arch-wiki-man”**. As the name says, it is also used to read the Arch Wiki from command line, but it doesn’t require Internet connection. Arch-wiki-man program helps you to browse and read entire Arch Wiki as Linux man pages. It will display any article from Arch Wiki in man pages format. Also, you need not to be online to browse Arch Wiki. The entire Arch Wiki will be downloaded locally and the updates are pushed automatically every two days. So, you always have an up-to-date, local copy of the Arch Wiki on your system. + +### Installing Arch-wiki-man + +Arch-wiki-man is available in [**AUR**][2], so you can install it using any AUR helper programs, for example [**Yay**][3]. + +``` + $ yay -S arch-wiki-man +``` + +Alternatively, it can be installed using NPM package manager like below. Make sure you have [**installed NodeJS**][4] and run the following command to install it: + +``` + $ npm install -g arch-wiki-man +``` + +### Browse And Read Entire Arch Wiki As Linux Man Pages + +The typical syntax of Arch-wiki-man is: + +``` + $ awman +``` + +Let me show you some examples. + +**Search with one or more matches** + +Let us search for a [**Arch Linux installation guide**][5]. To do so, simply run: + +``` + $ awman Installation guide +``` + +The above command will search for the matches that contains the search term “Installation guide” in the Arch Wiki. If there are multiple matches for the given search term, a selection menu will appear. Choose the guide you want to read using **UP/DOWN arrows** or Vim-style keybindings ( **j/k** ) and hit ENTER to open it. The resulting guide will open in man pages format like below. + +![][6] + +Here, awman refers **a** rch **w** iki **m** an. + +All man command options are supported, so you can navigate through guide as the way you do when reading a man page. To view the help section, press **h**. + +![][7] + +To exit the selection menu without entering **man** , simply press **Ctrl+c**. + +To go back and/or quit man, type **q**. + +**Search matches in titles and descriptions** + +By default, Awman will search for the matches in titles only. You can, however, direct it to search for the matches in both the titles and descriptions as well. + +``` + $ awman -d vim +``` + +Or, + +``` + $ awman --desc-search vim +``` + +**Search for matches in contents** + +Apart from searching for matches in titles and descriptions, it is also possible to scan the contents for a match as well. Please note that this will significantly slower the search process. + +``` + $ awman -k emacs +``` + +Or, + +``` + $ awman --apropos emacs +``` + +**Open the search results in web browser** + +If you don’t want to view the arch wiki guides in man page format, you can open it in a web browser. To do so, run: + +``` + $ awman -w pacman +``` + +Or, + +``` + $ awman --web pacman +``` + +This command will open the resulting match in the default web browser rather than with **man** command. Please note that you need Internet connection to use this option. + +**Search in other languages** + +By default, Awman will open the Arch wiki pages in English. If you want to view the results in other languages, for example **Spanish** , simply do: + +``` + $ awman -l spanish codecs +``` + +![][8] + +To view the list of available language options, run: + +``` + + $ awman --list-languages + +``` + +**Update the local copy of Arch Wiki** + +Like I already said, the updates are pushed automatically every two days. If you want to update it manually, simply run: + +``` +$ awman-update +arch-wiki-man@1.3.0 /usr/lib/node_modules/arch-wiki-man +└── arch-wiki-md-repo@0.10.84 + +arch-wiki-md-repo has been successfully updated or reinstalled. +``` + +Cheers! + + + +-------------------------------------------------------------------------------- + +via: https://www.ostechnix.com/how-to-browse-and-read-entire-arch-wiki-as-linux-man-pages/ + +作者：[SK][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://www.ostechnix.com/author/sk/ +[b]: https://github.com/lujun9972 +[1]: https://www.ostechnix.com/search-arch-wiki-website-commandline/ +[2]: https://aur.archlinux.org/packages/arch-wiki-man/ +[3]: https://www.ostechnix.com/yay-found-yet-another-reliable-aur-helper/ +[4]: https://www.ostechnix.com/install-node-js-linux/ +[5]: https://www.ostechnix.com/install-arch-linux-latest-version/ +[6]: http://www.ostechnix.com/wp-content/uploads/2018/10/awman-1.gif +[7]: http://www.ostechnix.com/wp-content/uploads/2018/10/awman-2.png +[8]: https://www.ostechnix.com/wp-content/uploads/2018/10/awman-3-1.png From 8e336162c7618734bed4ff5e5667db5db64f45ca Mon Sep 17 00:00:00 2001 From: darksun Date: Tue, 16 Oct 2018 09:01:59 +0800 Subject: [PATCH 09/44] =?UTF-8?q?=E9=80=89=E9=A2=98:=20Lab=204:=20Preempti?= =?UTF-8?q?ve=20Multitasking?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...20181016 Lab 4- Preemptive Multitasking.md | 595 ++++++++++++++++++ 1 file changed, 595 insertions(+) create mode 100644 sources/tech/20181016 Lab 4- Preemptive Multitasking.md diff --git a/sources/tech/20181016 Lab 4- Preemptive Multitasking.md b/sources/tech/20181016 Lab 4- Preemptive Multitasking.md new file mode 100644 index 0000000000..9e510ed7c6 --- /dev/null +++ b/sources/tech/20181016 Lab 4- Preemptive Multitasking.md @@ -0,0 +1,595 @@ +Lab 4: Preemptive Multitasking +====== +### Lab 4: Preemptive Multitasking + +**Part A due Thursday, October 18, 2018 +Part B due Thursday, October 25, 2018 +Part C due Thursday, November 1, 2018** + +#### Introduction + +In this lab you will implement preemptive multitasking among multiple simultaneously active user-mode environments. + +In part A you will add multiprocessor support to JOS, implement round-robin scheduling, and add basic environment management system calls (calls that create and destroy environments, and allocate/map memory). + +In part B, you will implement a Unix-like `fork()`, which allows a user-mode environment to create copies of itself. + +Finally, in part C you will add support for inter-process communication (IPC), allowing different user-mode environments to communicate and synchronize with each other explicitly. You will also add support for hardware clock interrupts and preemption. + +##### Getting Started + +Use Git to commit your Lab 3 source, fetch the latest version of the course repository, and then create a local branch called `lab4` based on our lab4 branch, `origin/lab4`: + +``` + athena% cd ~/6.828/lab + athena% add git + athena% git pull + Already up-to-date. + athena% git checkout -b lab4 origin/lab4 + Branch lab4 set up to track remote branch refs/remotes/origin/lab4. + Switched to a new branch "lab4" + athena% git merge lab3 + Merge made by recursive. + ... + athena% +``` + +Lab 4 contains a number of new source files, some of which you should browse before you start: +| kern/cpu.h | Kernel-private definitions for multiprocessor support | +| kern/mpconfig.c | Code to read the multiprocessor configuration | +| kern/lapic.c | Kernel code driving the local APIC unit in each processor | +| kern/mpentry.S | Assembly-language entry code for non-boot CPUs | +| kern/spinlock.h | Kernel-private definitions for spin locks, including the big kernel lock | +| kern/spinlock.c | Kernel code implementing spin locks | +| kern/sched.c | Code skeleton of the scheduler that you are about to implement | + +##### Lab Requirements + +This lab is divided into three parts, A, B, and C. We have allocated one week in the schedule for each part. + +As before, you will need to do all of the regular exercises described in the lab and _at least one_ challenge problem. (You do not need to do one challenge problem per part, just one for the whole lab.) Additionally, you will need to write up a brief description of the challenge problem that you implemented. If you implement more than one challenge problem, you only need to describe one of them in the write-up, though of course you are welcome to do more. Place the write-up in a file called `answers-lab4.txt` in the top level of your `lab` directory before handing in your work. + +#### Part A: Multiprocessor Support and Cooperative Multitasking + +In the first part of this lab, you will first extend JOS to run on a multiprocessor system, and then implement some new JOS kernel system calls to allow user-level environments to create additional new environments. You will also implement _cooperative_ round-robin scheduling, allowing the kernel to switch from one environment to another when the current environment voluntarily relinquishes the CPU (or exits). Later in part C you will implement _preemptive_ scheduling, which allows the kernel to re-take control of the CPU from an environment after a certain time has passed even if the environment does not cooperate. + +##### Multiprocessor Support + +We are going to make JOS support "symmetric multiprocessing" (SMP), a multiprocessor model in which all CPUs have equivalent access to system resources such as memory and I/O buses. While all CPUs are functionally identical in SMP, during the boot process they can be classified into two types: the bootstrap processor (BSP) is responsible for initializing the system and for booting the operating system; and the application processors (APs) are activated by the BSP only after the operating system is up and running. Which processor is the BSP is determined by the hardware and the BIOS. Up to this point, all your existing JOS code has been running on the BSP. + +In an SMP system, each CPU has an accompanying local APIC (LAPIC) unit. The LAPIC units are responsible for delivering interrupts throughout the system. The LAPIC also provides its connected CPU with a unique identifier. In this lab, we make use of the following basic functionality of the LAPIC unit (in `kern/lapic.c`): + + * Reading the LAPIC identifier (APIC ID) to tell which CPU our code is currently running on (see `cpunum()`). + * Sending the `STARTUP` interprocessor interrupt (IPI) from the BSP to the APs to bring up other CPUs (see `lapic_startap()`). + * In part C, we program LAPIC's built-in timer to trigger clock interrupts to support preemptive multitasking (see `apic_init()`). + + + +A processor accesses its LAPIC using memory-mapped I/O (MMIO). In MMIO, a portion of _physical_ memory is hardwired to the registers of some I/O devices, so the same load/store instructions typically used to access memory can be used to access device registers. You've already seen one IO hole at physical address `0xA0000` (we use this to write to the VGA display buffer). The LAPIC lives in a hole starting at physical address `0xFE000000` (32MB short of 4GB), so it's too high for us to access using our usual direct map at KERNBASE. The JOS virtual memory map leaves a 4MB gap at `MMIOBASE` so we have a place to map devices like this. Since later labs introduce more MMIO regions, you'll write a simple function to allocate space from this region and map device memory to it. + +``` +Exercise 1. Implement `mmio_map_region` in `kern/pmap.c`. To see how this is used, look at the beginning of `lapic_init` in `kern/lapic.c`. You'll have to do the next exercise, too, before the tests for `mmio_map_region` will run. +``` + +###### Application Processor Bootstrap + +Before booting up APs, the BSP should first collect information about the multiprocessor system, such as the total number of CPUs, their APIC IDs and the MMIO address of the LAPIC unit. The `mp_init()` function in `kern/mpconfig.c` retrieves this information by reading the MP configuration table that resides in the BIOS's region of memory. + +The `boot_aps()` function (in `kern/init.c`) drives the AP bootstrap process. APs start in real mode, much like how the bootloader started in `boot/boot.S`, so `boot_aps()` copies the AP entry code (`kern/mpentry.S`) to a memory location that is addressable in the real mode. Unlike with the bootloader, we have some control over where the AP will start executing code; we copy the entry code to `0x7000` (`MPENTRY_PADDR`), but any unused, page-aligned physical address below 640KB would work. + +After that, `boot_aps()` activates APs one after another, by sending `STARTUP` IPIs to the LAPIC unit of the corresponding AP, along with an initial `CS:IP` address at which the AP should start running its entry code (`MPENTRY_PADDR` in our case). The entry code in `kern/mpentry.S` is quite similar to that of `boot/boot.S`. After some brief setup, it puts the AP into protected mode with paging enabled, and then calls the C setup routine `mp_main()` (also in `kern/init.c`). `boot_aps()` waits for the AP to signal a `CPU_STARTED` flag in `cpu_status` field of its `struct CpuInfo` before going on to wake up the next one. + +``` +Exercise 2. Read `boot_aps()` and `mp_main()` in `kern/init.c`, and the assembly code in `kern/mpentry.S`. Make sure you understand the control flow transfer during the bootstrap of APs. Then modify your implementation of `page_init()` in `kern/pmap.c` to avoid adding the page at `MPENTRY_PADDR` to the free list, so that we can safely copy and run AP bootstrap code at that physical address. Your code should pass the updated `check_page_free_list()` test (but might fail the updated `check_kern_pgdir()` test, which we will fix soon). +``` + +``` +Question + + 1. Compare `kern/mpentry.S` side by side with `boot/boot.S`. Bearing in mind that `kern/mpentry.S` is compiled and linked to run above `KERNBASE` just like everything else in the kernel, what is the purpose of macro `MPBOOTPHYS`? Why is it necessary in `kern/mpentry.S` but not in `boot/boot.S`? In other words, what could go wrong if it were omitted in `kern/mpentry.S`? +Hint: recall the differences between the link address and the load address that we have discussed in Lab 1. +``` + + +###### Per-CPU State and Initialization + +When writing a multiprocessor OS, it is important to distinguish between per-CPU state that is private to each processor, and global state that the whole system shares. `kern/cpu.h` defines most of the per-CPU state, including `struct CpuInfo`, which stores per-CPU variables. `cpunum()` always returns the ID of the CPU that calls it, which can be used as an index into arrays like `cpus`. Alternatively, the macro `thiscpu` is shorthand for the current CPU's `struct CpuInfo`. + +Here is the per-CPU state you should be aware of: + + * **Per-CPU kernel stack**. +Because multiple CPUs can trap into the kernel simultaneously, we need a separate kernel stack for each processor to prevent them from interfering with each other's execution. The array `percpu_kstacks[NCPU][KSTKSIZE]` reserves space for NCPU's worth of kernel stacks. + +In Lab 2, you mapped the physical memory that `bootstack` refers to as the BSP's kernel stack just below `KSTACKTOP`. Similarly, in this lab, you will map each CPU's kernel stack into this region with guard pages acting as a buffer between them. CPU 0's stack will still grow down from `KSTACKTOP`; CPU 1's stack will start `KSTKGAP` bytes below the bottom of CPU 0's stack, and so on. `inc/memlayout.h` shows the mapping layout. + + * **Per-CPU TSS and TSS descriptor**. +A per-CPU task state segment (TSS) is also needed in order to specify where each CPU's kernel stack lives. The TSS for CPU _i_ is stored in `cpus[i].cpu_ts`, and the corresponding TSS descriptor is defined in the GDT entry `gdt[(GD_TSS0 >> 3) + i]`. The global `ts` variable defined in `kern/trap.c` will no longer be useful. + + * **Per-CPU current environment pointer**. +Since each CPU can run different user process simultaneously, we redefined the symbol `curenv` to refer to `cpus[cpunum()].cpu_env` (or `thiscpu->cpu_env`), which points to the environment _currently_ executing on the _current_ CPU (the CPU on which the code is running). + + * **Per-CPU system registers**. +All registers, including system registers, are private to a CPU. Therefore, instructions that initialize these registers, such as `lcr3()`, `ltr()`, `lgdt()`, `lidt()`, etc., must be executed once on each CPU. Functions `env_init_percpu()` and `trap_init_percpu()` are defined for this purpose. + + + +``` +Exercise 3. Modify `mem_init_mp()` (in `kern/pmap.c`) to map per-CPU stacks starting at `KSTACKTOP`, as shown in `inc/memlayout.h`. The size of each stack is `KSTKSIZE` bytes plus `KSTKGAP` bytes of unmapped guard pages. Your code should pass the new check in `check_kern_pgdir()`. +``` + +``` +Exercise 4. The code in `trap_init_percpu()` (`kern/trap.c`) initializes the TSS and TSS descriptor for the BSP. It worked in Lab 3, but is incorrect when running on other CPUs. Change the code so that it can work on all CPUs. (Note: your new code should not use the global `ts` variable any more.) +``` + +When you finish the above exercises, run JOS in QEMU with 4 CPUs using make qemu CPUS=4 (or make qemu-nox CPUS=4), you should see output like this: + +``` + ... + Physical memory: 66556K available, base = 640K, extended = 65532K + check_page_alloc() succeeded! + check_page() succeeded! + check_kern_pgdir() succeeded! + check_page_installed_pgdir() succeeded! + SMP: CPU 0 found 4 CPU(s) + enabled interrupts: 1 2 + SMP: CPU 1 starting + SMP: CPU 2 starting + SMP: CPU 3 starting +``` + +###### Locking + +Our current code spins after initializing the AP in `mp_main()`. Before letting the AP get any further, we need to first address race conditions when multiple CPUs run kernel code simultaneously. The simplest way to achieve this is to use a _big kernel lock_. The big kernel lock is a single global lock that is held whenever an environment enters kernel mode, and is released when the environment returns to user mode. In this model, environments in user mode can run concurrently on any available CPUs, but no more than one environment can run in kernel mode; any other environments that try to enter kernel mode are forced to wait. + +`kern/spinlock.h` declares the big kernel lock, namely `kernel_lock`. It also provides `lock_kernel()` and `unlock_kernel()`, shortcuts to acquire and release the lock. You should apply the big kernel lock at four locations: + + * In `i386_init()`, acquire the lock before the BSP wakes up the other CPUs. + * In `mp_main()`, acquire the lock after initializing the AP, and then call `sched_yield()` to start running environments on this AP. + * In `trap()`, acquire the lock when trapped from user mode. To determine whether a trap happened in user mode or in kernel mode, check the low bits of the `tf_cs`. + * In `env_run()`, release the lock _right before_ switching to user mode. Do not do that too early or too late, otherwise you will experience races or deadlocks. + + +``` +Exercise 5. Apply the big kernel lock as described above, by calling `lock_kernel()` and `unlock_kernel()` at the proper locations. +``` + +How to test if your locking is correct? You can't at this moment! But you will be able to after you implement the scheduler in the next exercise. + +``` +Question + + 2. It seems that using the big kernel lock guarantees that only one CPU can run the kernel code at a time. Why do we still need separate kernel stacks for each CPU? Describe a scenario in which using a shared kernel stack will go wrong, even with the protection of the big kernel lock. +``` + +``` +Challenge! The big kernel lock is simple and easy to use. Nevertheless, it eliminates all concurrency in kernel mode. Most modern operating systems use different locks to protect different parts of their shared state, an approach called _fine-grained locking_. Fine-grained locking can increase performance significantly, but is more difficult to implement and error-prone. If you are brave enough, drop the big kernel lock and embrace concurrency in JOS! + +It is up to you to decide the locking granularity (the amount of data that a lock protects). As a hint, you may consider using spin locks to ensure exclusive access to these shared components in the JOS kernel: + + * The page allocator. + * The console driver. + * The scheduler. + * The inter-process communication (IPC) state that you will implement in the part C. +``` + + +##### Round-Robin Scheduling + +Your next task in this lab is to change the JOS kernel so that it can alternate between multiple environments in "round-robin" fashion. Round-robin scheduling in JOS works as follows: + + * The function `sched_yield()` in the new `kern/sched.c` is responsible for selecting a new environment to run. It searches sequentially through the `envs[]` array in circular fashion, starting just after the previously running environment (or at the beginning of the array if there was no previously running environment), picks the first environment it finds with a status of `ENV_RUNNABLE` (see `inc/env.h`), and calls `env_run()` to jump into that environment. + * `sched_yield()` must never run the same environment on two CPUs at the same time. It can tell that an environment is currently running on some CPU (possibly the current CPU) because that environment's status will be `ENV_RUNNING`. + * We have implemented a new system call for you, `sys_yield()`, which user environments can call to invoke the kernel's `sched_yield()` function and thereby voluntarily give up the CPU to a different environment. + + + +``` +Exercise 6. Implement round-robin scheduling in `sched_yield()` as described above. Don't forget to modify `syscall()` to dispatch `sys_yield()`. + +Make sure to invoke `sched_yield()` in `mp_main`. + +Modify `kern/init.c` to create three (or more!) environments that all run the program `user/yield.c`. + +Run make qemu. You should see the environments switch back and forth between each other five times before terminating, like below. + +Test also with several CPUS: make qemu CPUS=2. + + ... + Hello, I am environment 00001000. + Hello, I am environment 00001001. + Hello, I am environment 00001002. + Back in environment 00001000, iteration 0. + Back in environment 00001001, iteration 0. + Back in environment 00001002, iteration 0. + Back in environment 00001000, iteration 1. + Back in environment 00001001, iteration 1. + Back in environment 00001002, iteration 1. + ... + +After the `yield` programs exit, there will be no runnable environment in the system, the scheduler should invoke the JOS kernel monitor. If any of this does not happen, then fix your code before proceeding. +``` + +``` +Question + + 3. In your implementation of `env_run()` you should have called `lcr3()`. Before and after the call to `lcr3()`, your code makes references (at least it should) to the variable `e`, the argument to `env_run`. Upon loading the `%cr3` register, the addressing context used by the MMU is instantly changed. But a virtual address (namely `e`) has meaning relative to a given address context--the address context specifies the physical address to which the virtual address maps. Why can the pointer `e` be dereferenced both before and after the addressing switch? + 4. Whenever the kernel switches from one environment to another, it must ensure the old environment's registers are saved so they can be restored properly later. Why? Where does this happen? +``` + +``` +Challenge! Add a less trivial scheduling policy to the kernel, such as a fixed-priority scheduler that allows each environment to be assigned a priority and ensures that higher-priority environments are always chosen in preference to lower-priority environments. If you're feeling really adventurous, try implementing a Unix-style adjustable-priority scheduler or even a lottery or stride scheduler. (Look up "lottery scheduling" and "stride scheduling" in Google.) + +Write a test program or two that verifies that your scheduling algorithm is working correctly (i.e., the right environments get run in the right order). It may be easier to write these test programs once you have implemented `fork()` and IPC in parts B and C of this lab. +``` + +``` +Challenge! The JOS kernel currently does not allow applications to use the x86 processor's x87 floating-point unit (FPU), MMX instructions, or Streaming SIMD Extensions (SSE). Extend the `Env` structure to provide a save area for the processor's floating point state, and extend the context switching code to save and restore this state properly when switching from one environment to another. The `FXSAVE` and `FXRSTOR` instructions may be useful, but note that these are not in the old i386 user's manual because they were introduced in more recent processors. Write a user-level test program that does something cool with floating-point. +``` + +##### System Calls for Environment Creation + +Although your kernel is now capable of running and switching between multiple user-level environments, it is still limited to running environments that the _kernel_ initially set up. You will now implement the necessary JOS system calls to allow _user_ environments to create and start other new user environments. + +Unix provides the `fork()` system call as its process creation primitive. Unix `fork()` copies the entire address space of calling process (the parent) to create a new process (the child). The only differences between the two observable from user space are their process IDs and parent process IDs (as returned by `getpid` and `getppid`). In the parent, `fork()` returns the child's process ID, while in the child, `fork()` returns 0. By default, each process gets its own private address space, and neither process's modifications to memory are visible to the other. + +You will provide a different, more primitive set of JOS system calls for creating new user-mode environments. With these system calls you will be able to implement a Unix-like `fork()` entirely in user space, in addition to other styles of environment creation. The new system calls you will write for JOS are as follows: + + * `sys_exofork`: +This system call creates a new environment with an almost blank slate: nothing is mapped in the user portion of its address space, and it is not runnable. The new environment will have the same register state as the parent environment at the time of the `sys_exofork` call. In the parent, `sys_exofork` will return the `envid_t` of the newly created environment (or a negative error code if the environment allocation failed). In the child, however, it will return 0. (Since the child starts out marked as not runnable, `sys_exofork` will not actually return in the child until the parent has explicitly allowed this by marking the child runnable using....) + * `sys_env_set_status`: +Sets the status of a specified environment to `ENV_RUNNABLE` or `ENV_NOT_RUNNABLE`. This system call is typically used to mark a new environment ready to run, once its address space and register state has been fully initialized. + * `sys_page_alloc`: +Allocates a page of physical memory and maps it at a given virtual address in a given environment's address space. + * `sys_page_map`: +Copy a page mapping ( _not_ the contents of a page!) from one environment's address space to another, leaving a memory sharing arrangement in place so that the new and the old mappings both refer to the same page of physical memory. + * `sys_page_unmap`: +Unmap a page mapped at a given virtual address in a given environment. + + + +For all of the system calls above that accept environment IDs, the JOS kernel supports the convention that a value of 0 means "the current environment." This convention is implemented by `envid2env()` in `kern/env.c`. + +We have provided a very primitive implementation of a Unix-like `fork()` in the test program `user/dumbfork.c`. This test program uses the above system calls to create and run a child environment with a copy of its own address space. The two environments then switch back and forth using `sys_yield` as in the previous exercise. The parent exits after 10 iterations, whereas the child exits after 20. + +``` +Exercise 7. Implement the system calls described above in `kern/syscall.c` and make sure `syscall()` calls them. You will need to use various functions in `kern/pmap.c` and `kern/env.c`, particularly `envid2env()`. For now, whenever you call `envid2env()`, pass 1 in the `checkperm` parameter. Be sure you check for any invalid system call arguments, returning `-E_INVAL` in that case. Test your JOS kernel with `user/dumbfork` and make sure it works before proceeding. +``` + +``` +Challenge! Add the additional system calls necessary to _read_ all of the vital state of an existing environment as well as set it up. Then implement a user mode program that forks off a child environment, runs it for a while (e.g., a few iterations of `sys_yield()`), then takes a complete snapshot or _checkpoint_ of the child environment, runs the child for a while longer, and finally restores the child environment to the state it was in at the checkpoint and continues it from there. Thus, you are effectively "replaying" the execution of the child environment from an intermediate state. Make the child environment perform some interaction with the user using `sys_cgetc()` or `readline()` so that the user can view and mutate its internal state, and verify that with your checkpoint/restart you can give the child environment a case of selective amnesia, making it "forget" everything that happened beyond a certain point. +``` + +This completes Part A of the lab; make sure it passes all of the Part A tests when you run make grade, and hand it in using make handin as usual. If you are trying to figure out why a particular test case is failing, run ./grade-lab4 -v, which will show you the output of the kernel builds and QEMU runs for each test, until a test fails. When a test fails, the script will stop, and then you can inspect `jos.out` to see what the kernel actually printed. + +#### Part B: Copy-on-Write Fork + +As mentioned earlier, Unix provides the `fork()` system call as its primary process creation primitive. The `fork()` system call copies the address space of the calling process (the parent) to create a new process (the child). + +xv6 Unix implements `fork()` by copying all data from the parent's pages into new pages allocated for the child. This is essentially the same approach that `dumbfork()` takes. The copying of the parent's address space into the child is the most expensive part of the `fork()` operation. + +However, a call to `fork()` is frequently followed almost immediately by a call to `exec()` in the child process, which replaces the child's memory with a new program. This is what the the shell typically does, for example. In this case, the time spent copying the parent's address space is largely wasted, because the child process will use very little of its memory before calling `exec()`. + +For this reason, later versions of Unix took advantage of virtual memory hardware to allow the parent and child to _share_ the memory mapped into their respective address spaces until one of the processes actually modifies it. This technique is known as _copy-on-write_. To do this, on `fork()` the kernel would copy the address space _mappings_ from the parent to the child instead of the contents of the mapped pages, and at the same time mark the now-shared pages read-only. When one of the two processes tries to write to one of these shared pages, the process takes a page fault. At this point, the Unix kernel realizes that the page was really a "virtual" or "copy-on-write" copy, and so it makes a new, private, writable copy of the page for the faulting process. In this way, the contents of individual pages aren't actually copied until they are actually written to. This optimization makes a `fork()` followed by an `exec()` in the child much cheaper: the child will probably only need to copy one page (the current page of its stack) before it calls `exec()`. + +In the next piece of this lab, you will implement a "proper" Unix-like `fork()` with copy-on-write, as a user space library routine. Implementing `fork()` and copy-on-write support in user space has the benefit that the kernel remains much simpler and thus more likely to be correct. It also lets individual user-mode programs define their own semantics for `fork()`. A program that wants a slightly different implementation (for example, the expensive always-copy version like `dumbfork()`, or one in which the parent and child actually share memory afterward) can easily provide its own. + +##### User-level page fault handling + +A user-level copy-on-write `fork()` needs to know about page faults on write-protected pages, so that's what you'll implement first. Copy-on-write is only one of many possible uses for user-level page fault handling. + +It's common to set up an address space so that page faults indicate when some action needs to take place. For example, most Unix kernels initially map only a single page in a new process's stack region, and allocate and map additional stack pages later "on demand" as the process's stack consumption increases and causes page faults on stack addresses that are not yet mapped. A typical Unix kernel must keep track of what action to take when a page fault occurs in each region of a process's space. For example, a fault in the stack region will typically allocate and map new page of physical memory. A fault in the program's BSS region will typically allocate a new page, fill it with zeroes, and map it. In systems with demand-paged executables, a fault in the text region will read the corresponding page of the binary off of disk and then map it. + +This is a lot of information for the kernel to keep track of. Instead of taking the traditional Unix approach, you will decide what to do about each page fault in user space, where bugs are less damaging. This design has the added benefit of allowing programs great flexibility in defining their memory regions; you'll use user-level page fault handling later for mapping and accessing files on a disk-based file system. + +###### Setting the Page Fault Handler + +In order to handle its own page faults, a user environment will need to register a _page fault handler entrypoint_ with the JOS kernel. The user environment registers its page fault entrypoint via the new `sys_env_set_pgfault_upcall` system call. We have added a new member to the `Env` structure, `env_pgfault_upcall`, to record this information. + +``` +Exercise 8. Implement the `sys_env_set_pgfault_upcall` system call. Be sure to enable permission checking when looking up the environment ID of the target environment, since this is a "dangerous" system call. +``` + +###### Normal and Exception Stacks in User Environments + +During normal execution, a user environment in JOS will run on the _normal_ user stack: its `ESP` register starts out pointing at `USTACKTOP`, and the stack data it pushes resides on the page between `USTACKTOP-PGSIZE` and `USTACKTOP-1` inclusive. When a page fault occurs in user mode, however, the kernel will restart the user environment running a designated user-level page fault handler on a different stack, namely the _user exception_ stack. In essence, we will make the JOS kernel implement automatic "stack switching" on behalf of the user environment, in much the same way that the x86 _processor_ already implements stack switching on behalf of JOS when transferring from user mode to kernel mode! + +The JOS user exception stack is also one page in size, and its top is defined to be at virtual address `UXSTACKTOP`, so the valid bytes of the user exception stack are from `UXSTACKTOP-PGSIZE` through `UXSTACKTOP-1` inclusive. While running on this exception stack, the user-level page fault handler can use JOS's regular system calls to map new pages or adjust mappings so as to fix whatever problem originally caused the page fault. Then the user-level page fault handler returns, via an assembly language stub, to the faulting code on the original stack. + +Each user environment that wants to support user-level page fault handling will need to allocate memory for its own exception stack, using the `sys_page_alloc()` system call introduced in part A. + +###### Invoking the User Page Fault Handler + +You will now need to change the page fault handling code in `kern/trap.c` to handle page faults from user mode as follows. We will call the state of the user environment at the time of the fault the _trap-time_ state. + +If there is no page fault handler registered, the JOS kernel destroys the user environment with a message as before. Otherwise, the kernel sets up a trap frame on the exception stack that looks like a `struct UTrapframe` from `inc/trap.h`: + +``` + <-- UXSTACKTOP + trap-time esp + trap-time eflags + trap-time eip + trap-time eax start of struct PushRegs + trap-time ecx + trap-time edx + trap-time ebx + trap-time esp + trap-time ebp + trap-time esi + trap-time edi end of struct PushRegs + tf_err (error code) + fault_va <-- %esp when handler is run + +``` + +The kernel then arranges for the user environment to resume execution with the page fault handler running on the exception stack with this stack frame; you must figure out how to make this happen. The `fault_va` is the virtual address that caused the page fault. + +If the user environment is _already_ running on the user exception stack when an exception occurs, then the page fault handler itself has faulted. In this case, you should start the new stack frame just under the current `tf->tf_esp` rather than at `UXSTACKTOP`. You should first push an empty 32-bit word, then a `struct UTrapframe`. + +To test whether `tf->tf_esp` is already on the user exception stack, check whether it is in the range between `UXSTACKTOP-PGSIZE` and `UXSTACKTOP-1`, inclusive. + +``` +Exercise 9. Implement the code in `page_fault_handler` in `kern/trap.c` required to dispatch page faults to the user-mode handler. Be sure to take appropriate precautions when writing into the exception stack. (What happens if the user environment runs out of space on the exception stack?) +``` + +###### User-mode Page Fault Entrypoint + +Next, you need to implement the assembly routine that will take care of calling the C page fault handler and resume execution at the original faulting instruction. This assembly routine is the handler that will be registered with the kernel using `sys_env_set_pgfault_upcall()`. + +``` +Exercise 10. Implement the `_pgfault_upcall` routine in `lib/pfentry.S`. The interesting part is returning to the original point in the user code that caused the page fault. You'll return directly there, without going back through the kernel. The hard part is simultaneously switching stacks and re-loading the EIP. +``` + +Finally, you need to implement the C user library side of the user-level page fault handling mechanism. + +``` +Exercise 11. Finish `set_pgfault_handler()` in `lib/pgfault.c`. +``` + +###### Testing + +Run `user/faultread` (make run-faultread). You should see: + +``` + ... + [00000000] new env 00001000 + [00001000] user fault va 00000000 ip 0080003a + TRAP frame ... + [00001000] free env 00001000 +``` + +Run `user/faultdie`. You should see: + +``` + ... + [00000000] new env 00001000 + i faulted at va deadbeef, err 6 + [00001000] exiting gracefully + [00001000] free env 00001000 +``` + +Run `user/faultalloc`. You should see: + +``` + ... + [00000000] new env 00001000 + fault deadbeef + this string was faulted in at deadbeef + fault cafebffe + fault cafec000 + this string was faulted in at cafebffe + [00001000] exiting gracefully + [00001000] free env 00001000 +``` + +If you see only the first "this string" line, it means you are not handling recursive page faults properly. + +Run `user/faultallocbad`. You should see: + +``` + ... + [00000000] new env 00001000 + [00001000] user_mem_check assertion failure for va deadbeef + [00001000] free env 00001000 +``` + +Make sure you understand why `user/faultalloc` and `user/faultallocbad` behave differently. + +``` +Challenge! Extend your kernel so that not only page faults, but _all_ types of processor exceptions that code running in user space can generate, can be redirected to a user-mode exception handler. Write user-mode test programs to test user-mode handling of various exceptions such as divide-by-zero, general protection fault, and illegal opcode. +``` + +##### Implementing Copy-on-Write Fork + +You now have the kernel facilities to implement copy-on-write `fork()` entirely in user space. + +We have provided a skeleton for your `fork()` in `lib/fork.c`. Like `dumbfork()`, `fork()` should create a new environment, then scan through the parent environment's entire address space and set up corresponding page mappings in the child. The key difference is that, while `dumbfork()` copied _pages_ , `fork()` will initially only copy page _mappings_. `fork()` will copy each page only when one of the environments tries to write it. + +The basic control flow for `fork()` is as follows: + + 1. The parent installs `pgfault()` as the C-level page fault handler, using the `set_pgfault_handler()` function you implemented above. + + 2. The parent calls `sys_exofork()` to create a child environment. + + 3. For each writable or copy-on-write page in its address space below UTOP, the parent calls `duppage`, which should map the page copy-on-write into the address space of the child and then _remap_ the page copy-on-write in its own address space. [ Note: The ordering here (i.e., marking a page as COW in the child before marking it in the parent) actually matters! Can you see why? Try to think of a specific case where reversing the order could cause trouble. ] `duppage` sets both PTEs so that the page is not writeable, and to contain `PTE_COW` in the "avail" field to distinguish copy-on-write pages from genuine read-only pages. + +The exception stack is _not_ remapped this way, however. Instead you need to allocate a fresh page in the child for the exception stack. Since the page fault handler will be doing the actual copying and the page fault handler runs on the exception stack, the exception stack cannot be made copy-on-write: who would copy it? + +`fork()` also needs to handle pages that are present, but not writable or copy-on-write. + + 4. The parent sets the user page fault entrypoint for the child to look like its own. + + 5. The child is now ready to run, so the parent marks it runnable. + + + + +Each time one of the environments writes a copy-on-write page that it hasn't yet written, it will take a page fault. Here's the control flow for the user page fault handler: + + 1. The kernel propagates the page fault to `_pgfault_upcall`, which calls `fork()`'s `pgfault()` handler. + 2. `pgfault()` checks that the fault is a write (check for `FEC_WR` in the error code) and that the PTE for the page is marked `PTE_COW`. If not, panic. + 3. `pgfault()` allocates a new page mapped at a temporary location and copies the contents of the faulting page into it. Then the fault handler maps the new page at the appropriate address with read/write permissions, in place of the old read-only mapping. + + + +The user-level `lib/fork.c` code must consult the environment's page tables for several of the operations above (e.g., that the PTE for a page is marked `PTE_COW`). The kernel maps the environment's page tables at `UVPT` exactly for this purpose. It uses a [clever mapping trick][1] to make it to make it easy to lookup PTEs for user code. `lib/entry.S` sets up `uvpt` and `uvpd` so that you can easily lookup page-table information in `lib/fork.c`. + +`````` +Exercise 12. Implement `fork`, `duppage` and `pgfault` in `lib/fork.c`. + +Test your code with the `forktree` program. It should produce the following messages, with interspersed 'new env', 'free env', and 'exiting gracefully' messages. The messages may not appear in this order, and the environment IDs may be different. + + 1000: I am '' + 1001: I am '0' + 2000: I am '00' + 2001: I am '000' + 1002: I am '1' + 3000: I am '11' + 3001: I am '10' + 4000: I am '100' + 1003: I am '01' + 5000: I am '010' + 4001: I am '011' + 2002: I am '110' + 1004: I am '001' + 1005: I am '111' + 1006: I am '101' +``` + +``` +Challenge! Implement a shared-memory `fork()` called `sfork()`. This version should have the parent and child _share_ all their memory pages (so writes in one environment appear in the other) except for pages in the stack area, which should be treated in the usual copy-on-write manner. Modify `user/forktree.c` to use `sfork()` instead of regular `fork()`. Also, once you have finished implementing IPC in part C, use your `sfork()` to run `user/pingpongs`. You will have to find a new way to provide the functionality of the global `thisenv` pointer. +``` + +``` +Challenge! Your implementation of `fork` makes a huge number of system calls. On the x86, switching into the kernel using interrupts has non-trivial cost. Augment the system call interface so that it is possible to send a batch of system calls at once. Then change `fork` to use this interface. + +How much faster is your new `fork`? + +You can answer this (roughly) by using analytical arguments to estimate how much of an improvement batching system calls will make to the performance of your `fork`: How expensive is an `int 0x30` instruction? How many times do you execute `int 0x30` in your `fork`? Is accessing the `TSS` stack switch also expensive? And so on... + +Alternatively, you can boot your kernel on real hardware and _really_ benchmark your code. See the `RDTSC` (read time-stamp counter) instruction, defined in the IA32 manual, which counts the number of clock cycles that have elapsed since the last processor reset. QEMU doesn't emulate this instruction faithfully (it can either count the number of virtual instructions executed or use the host TSC, neither of which reflects the number of cycles a real CPU would require). +``` + +This ends part B. Make sure you pass all of the Part B tests when you run make grade. As usual, you can hand in your submission with make handin. + +#### Part C: Preemptive Multitasking and Inter-Process communication (IPC) + +In the final part of lab 4 you will modify the kernel to preempt uncooperative environments and to allow environments to pass messages to each other explicitly. + +##### Clock Interrupts and Preemption + +Run the `user/spin` test program. This test program forks off a child environment, which simply spins forever in a tight loop once it receives control of the CPU. Neither the parent environment nor the kernel ever regains the CPU. This is obviously not an ideal situation in terms of protecting the system from bugs or malicious code in user-mode environments, because any user-mode environment can bring the whole system to a halt simply by getting into an infinite loop and never giving back the CPU. In order to allow the kernel to _preempt_ a running environment, forcefully retaking control of the CPU from it, we must extend the JOS kernel to support external hardware interrupts from the clock hardware. + +###### Interrupt discipline + +External interrupts (i.e., device interrupts) are referred to as IRQs. There are 16 possible IRQs, numbered 0 through 15. The mapping from IRQ number to IDT entry is not fixed. `pic_init` in `picirq.c` maps IRQs 0-15 to IDT entries `IRQ_OFFSET` through `IRQ_OFFSET+15`. + +In `inc/trap.h`, `IRQ_OFFSET` is defined to be decimal 32. Thus the IDT entries 32-47 correspond to the IRQs 0-15. For example, the clock interrupt is IRQ 0. Thus, IDT[IRQ_OFFSET+0] (i.e., IDT[32]) contains the address of the clock's interrupt handler routine in the kernel. This `IRQ_OFFSET` is chosen so that the device interrupts do not overlap with the processor exceptions, which could obviously cause confusion. (In fact, in the early days of PCs running MS-DOS, the `IRQ_OFFSET` effectively _was_ zero, which indeed caused massive confusion between handling hardware interrupts and handling processor exceptions!) + +In JOS, we make a key simplification compared to xv6 Unix. External device interrupts are _always_ disabled when in the kernel (and, like xv6, enabled when in user space). External interrupts are controlled by the `FL_IF` flag bit of the `%eflags` register (see `inc/mmu.h`). When this bit is set, external interrupts are enabled. While the bit can be modified in several ways, because of our simplification, we will handle it solely through the process of saving and restoring `%eflags` register as we enter and leave user mode. + +You will have to ensure that the `FL_IF` flag is set in user environments when they run so that when an interrupt arrives, it gets passed through to the processor and handled by your interrupt code. Otherwise, interrupts are _masked_ , or ignored until interrupts are re-enabled. We masked interrupts with the very first instruction of the bootloader, and so far we have never gotten around to re-enabling them. + +``` +Exercise 13. Modify `kern/trapentry.S` and `kern/trap.c` to initialize the appropriate entries in the IDT and provide handlers for IRQs 0 through 15. Then modify the code in `env_alloc()` in `kern/env.c` to ensure that user environments are always run with interrupts enabled. + +Also uncomment the `sti` instruction in `sched_halt()` so that idle CPUs unmask interrupts. + +The processor never pushes an error code when invoking a hardware interrupt handler. You might want to re-read section 9.2 of the [80386 Reference Manual][2], or section 5.8 of the [IA-32 Intel Architecture Software Developer's Manual, Volume 3][3], at this time. + +After doing this exercise, if you run your kernel with any test program that runs for a non-trivial length of time (e.g., `spin`), you should see the kernel print trap frames for hardware interrupts. While interrupts are now enabled in the processor, JOS isn't yet handling them, so you should see it misattribute each interrupt to the currently running user environment and destroy it. Eventually it should run out of environments to destroy and drop into the monitor. +``` + +###### Handling Clock Interrupts + +In the `user/spin` program, after the child environment was first run, it just spun in a loop, and the kernel never got control back. We need to program the hardware to generate clock interrupts periodically, which will force control back to the kernel where we can switch control to a different user environment. + +The calls to `lapic_init` and `pic_init` (from `i386_init` in `init.c`), which we have written for you, set up the clock and the interrupt controller to generate interrupts. You now need to write the code to handle these interrupts. + +``` +Exercise 14. Modify the kernel's `trap_dispatch()` function so that it calls `sched_yield()` to find and run a different environment whenever a clock interrupt takes place. + +You should now be able to get the `user/spin` test to work: the parent environment should fork off the child, `sys_yield()` to it a couple times but in each case regain control of the CPU after one time slice, and finally kill the child environment and terminate gracefully. +``` + +This is a great time to do some _regression testing_. Make sure that you haven't broken any earlier part of that lab that used to work (e.g. `forktree`) by enabling interrupts. Also, try running with multiple CPUs using make CPUS=2 _target_. You should also be able to pass `stresssched` now. Run make grade to see for sure. You should now get a total score of 65/80 points on this lab. + +##### Inter-Process communication (IPC) + +(Technically in JOS this is "inter-environment communication" or "IEC", but everyone else calls it IPC, so we'll use the standard term.) + +We've been focusing on the isolation aspects of the operating system, the ways it provides the illusion that each program has a machine all to itself. Another important service of an operating system is to allow programs to communicate with each other when they want to. It can be quite powerful to let programs interact with other programs. The Unix pipe model is the canonical example. + +There are many models for interprocess communication. Even today there are still debates about which models are best. We won't get into that debate. Instead, we'll implement a simple IPC mechanism and then try it out. + +###### IPC in JOS + +You will implement a few additional JOS kernel system calls that collectively provide a simple interprocess communication mechanism. You will implement two system calls, `sys_ipc_recv` and `sys_ipc_try_send`. Then you will implement two library wrappers `ipc_recv` and `ipc_send`. + +The "messages" that user environments can send to each other using JOS's IPC mechanism consist of two components: a single 32-bit value, and optionally a single page mapping. Allowing environments to pass page mappings in messages provides an efficient way to transfer more data than will fit into a single 32-bit integer, and also allows environments to set up shared memory arrangements easily. + +###### Sending and Receiving Messages + +To receive a message, an environment calls `sys_ipc_recv`. This system call de-schedules the current environment and does not run it again until a message has been received. When an environment is waiting to receive a message, _any_ other environment can send it a message - not just a particular environment, and not just environments that have a parent/child arrangement with the receiving environment. In other words, the permission checking that you implemented in Part A will not apply to IPC, because the IPC system calls are carefully designed so as to be "safe": an environment cannot cause another environment to malfunction simply by sending it messages (unless the target environment is also buggy). + +To try to send a value, an environment calls `sys_ipc_try_send` with both the receiver's environment id and the value to be sent. If the named environment is actually receiving (it has called `sys_ipc_recv` and not gotten a value yet), then the send delivers the message and returns 0. Otherwise the send returns `-E_IPC_NOT_RECV` to indicate that the target environment is not currently expecting to receive a value. + +A library function `ipc_recv` in user space will take care of calling `sys_ipc_recv` and then looking up the information about the received values in the current environment's `struct Env`. + +Similarly, a library function `ipc_send` will take care of repeatedly calling `sys_ipc_try_send` until the send succeeds. + +###### Transferring Pages + +When an environment calls `sys_ipc_recv` with a valid `dstva` parameter (below `UTOP`), the environment is stating that it is willing to receive a page mapping. If the sender sends a page, then that page should be mapped at `dstva` in the receiver's address space. If the receiver already had a page mapped at `dstva`, then that previous page is unmapped. + +When an environment calls `sys_ipc_try_send` with a valid `srcva` (below `UTOP`), it means the sender wants to send the page currently mapped at `srcva` to the receiver, with permissions `perm`. After a successful IPC, the sender keeps its original mapping for the page at `srcva` in its address space, but the receiver also obtains a mapping for this same physical page at the `dstva` originally specified by the receiver, in the receiver's address space. As a result this page becomes shared between the sender and receiver. + +If either the sender or the receiver does not indicate that a page should be transferred, then no page is transferred. After any IPC the kernel sets the new field `env_ipc_perm` in the receiver's `Env` structure to the permissions of the page received, or zero if no page was received. + +###### Implementing IPC + +``` +Exercise 15. Implement `sys_ipc_recv` and `sys_ipc_try_send` in `kern/syscall.c`. Read the comments on both before implementing them, since they have to work together. When you call `envid2env` in these routines, you should set the `checkperm` flag to 0, meaning that any environment is allowed to send IPC messages to any other environment, and the kernel does no special permission checking other than verifying that the target envid is valid. + +Then implement the `ipc_recv` and `ipc_send` functions in `lib/ipc.c`. + +Use the `user/pingpong` and `user/primes` functions to test your IPC mechanism. `user/primes` will generate for each prime number a new environment until JOS runs out of environments. You might find it interesting to read `user/primes.c` to see all the forking and IPC going on behind the scenes. +``` + +``` +Challenge! Why does `ipc_send` have to loop? Change the system call interface so it doesn't have to. Make sure you can handle multiple environments trying to send to one environment at the same time. +``` + +``` +Challenge! The prime sieve is only one neat use of message passing between a large number of concurrent programs. Read C. A. R. Hoare, ``Communicating Sequential Processes,'' _Communications of the ACM_ 21(8) (August 1978), 666-667, and implement the matrix multiplication example. +``` + +``` +Challenge! One of the most impressive examples of the power of message passing is Doug McIlroy's power series calculator, described in [M. Douglas McIlroy, ``Squinting at Power Series,'' _Software--Practice and Experience_ , 20(7) (July 1990), 661-683][4]. Implement his power series calculator and compute the power series for _sin_ ( _x_ + _x_ ^3). +``` + +``` +Challenge! Make JOS's IPC mechanism more efficient by applying some of the techniques from Liedtke's paper, [Improving IPC by Kernel Design][5], or any other tricks you may think of. Feel free to modify the kernel's system call API for this purpose, as long as your code is backwards compatible with what our grading scripts expect. +``` + +**This ends part C.** Make sure you pass all of the make grade tests and don't forget to write up your answers to the questions and a description of your challenge exercise solution in `answers-lab4.txt`. + +Before handing in, use git status and git diff to examine your changes and don't forget to git add answers-lab4.txt. When you're ready, commit your changes with git commit -am 'my solutions to lab 4', then make handin and follow the directions. + +-------------------------------------------------------------------------------- + +via: https://pdos.csail.mit.edu/6.828/2018/labs/lab4/ + +作者：[csail.mit][a] +选题：[lujun9972][b] +译者：[译者ID](https://github.com/译者ID) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://pdos.csail.mit.edu +[b]: https://github.com/lujun9972 +[1]: https://pdos.csail.mit.edu/6.828/2018/labs/lab4/uvpt.html +[2]: https://pdos.csail.mit.edu/6.828/2018/labs/readings/i386/toc.htm +[3]: https://pdos.csail.mit.edu/6.828/2018/labs/readings/ia32/IA32-3A.pdf +[4]: https://swtch.com/~rsc/thread/squint.pdf +[5]: http://dl.acm.org/citation.cfm?id=168633 From 1320bb4d156696eccf7af7c00be71afbdc9aa38e Mon Sep 17 00:00:00 2001 From: geekpi Date: Tue, 16 Oct 2018 09:03:56 +0800 Subject: [PATCH 10/44] translated --- ...files with ls at the Linux command line.md | 75 ------------------- ...files with ls at the Linux command line.md | 73 ++++++++++++++++++ 2 files changed, 73 insertions(+), 75 deletions(-) delete mode 100644 sources/tech/20181003 Tips for listing files with ls at the Linux command line.md create mode 100644 translated/tech/20181003 Tips for listing files with ls at the Linux command line.md diff --git a/sources/tech/20181003 Tips for listing files with ls at the Linux command line.md b/sources/tech/20181003 Tips for listing files with ls at the Linux command line.md deleted file mode 100644 index fda48f1622..0000000000 --- a/sources/tech/20181003 Tips for listing files with ls at the Linux command line.md +++ /dev/null @@ -1,75 +0,0 @@ -translating---geekpi - -Tips for listing files with ls at the Linux command line -====== -Learn some of the Linux 'ls' command's most useful variations. -![](https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/button_push_open_keyboard_file_organize.png?itok=KlAsk1gx) - -One of the first commands I learned in Linux was `ls`. Knowing what’s in a directory where a file on your system resides is important. Being able to see and modify not just some but all of the files is also important. - -My first LInux cheat sheet was the [One Page Linux Manual][1] , which was released in1999 and became my go-to reference. I taped it over my desk and referred to it often as I began to explore Linux. Listing files with `ls -l` is introduced on the first page, at the bottom of the first column. - -Later, I would learn other iterations of this most basic command. Through the `ls` command, I began to learn about the complexity of the Linux file permissions and what was mine and what required root or sudo permission to change. I became very comfortable on the command line over time, and while I still use `ls -l` to find files in the directory, I frequently use `ls -al` so I can see hidden files that might need to be changed, like configuration files. - -According to an article by Eric Fischer about the `ls` command in the [Linux Documentation Project][2], the command's roots go back to the `listf` command on MIT’s Compatible Time Sharing System in 1961. When CTSS was replaced by [Multics][3], the command became `list`, with switches like `list -all`. According to [Wikipedia][4], `ls` appeared in the original version of AT&T Unix. The `ls` command we use today on Linux systems comes from the [GNU Core Utilities][5]. - -Most of the time, I use only a couple of iterations of the command. Looking inside a directory with `ls` or `ls -al` is how I generally use the command, but there are many other options that you should be familiar with. - -`$ ls -l` provides a simple list of the directory: - -![](https://opensource.com/sites/default/files/uploads/linux_ls_1_0.png) - -Using the man pages of my Fedora 28 system, I find that there are many other options to `ls`, all of which provide interesting and useful information about the Linux file system. By entering `man ls` at the command prompt, we can begin to explore some of the other options: - -![](https://opensource.com/sites/default/files/uploads/linux_ls_2_0.png) - -To sort the directory by file sizes, use `ls -lS`: - -![](https://opensource.com/sites/default/files/uploads/linux_ls_3_0.png) - -To list the contents in reverse order, use `ls -lr`: - -![](https://opensource.com/sites/default/files/uploads/linux_ls_4.png) - -To list contents by columns, use `ls -c`: - -![](https://opensource.com/sites/default/files/uploads/linux_ls_5.png) - -`ls -al` provides a list of all the files in the same directory: - -![](https://opensource.com/sites/default/files/uploads/linux_ls_6.png) - -Here are some additional options that I find useful and interesting: - - * List only the .txt files in the directory: `ls *.txt` - * List by file size: `ls -s` - * Sort by time and date: `ls -d` - * Sort by extension: `ls -X` - * Sort by file size: `ls -S` - * Long format with file size: `ls -ls` - * List only the .txt files in a directory: `ls *.txt` - - - -To generate a directory list in the specified format and send it to a file for later viewing, enter `ls -al > mydirectorylist`. Finally, one of the more exotic commands I found is `ls -R`, which provides a recursive list of all the directories on your computer and their contents. - -For a complete list of the all the iterations of the `ls` command, refer to the [GNU Core Utilities][6]. - --------------------------------------------------------------------------------- - -via: https://opensource.com/article/18/10/ls-command - -作者：[Don Watkins][a] -选题：[lujun9972](https://github.com/lujun9972) -译者：[译者ID](https://github.com/译者ID) -校对：[校对者ID](https://github.com/校对者ID) - -本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 - -[a]: https://opensource.com/users/don-watkins -[1]: http://hackerspace.cs.rutgers.edu/library/General/One_Page_Linux_Manual.pdf -[2]: http://www.tldp.org/LDP/LG/issue48/fischer.html -[3]: https://en.wikipedia.org/wiki/Multics -[4]: https://en.wikipedia.org/wiki/Ls -[5]: http://www.gnu.org/s/coreutils/ -[6]: https://www.gnu.org/software/coreutils/manual/html_node/ls-invocation.html#ls-invocation diff --git a/translated/tech/20181003 Tips for listing files with ls at the Linux command line.md b/translated/tech/20181003 Tips for listing files with ls at the Linux command line.md new file mode 100644 index 0000000000..b0fe9643da --- /dev/null +++ b/translated/tech/20181003 Tips for listing files with ls at the Linux command line.md @@ -0,0 +1,73 @@ +在 Linux 命令行中使用 ls 列出文件的提示 +====== +学习一些 Linux "ls" 命令最有用的变化。 +![](https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/button_push_open_keyboard_file_organize.png?itok=KlAsk1gx) + +我在 Linux 中最先学到的命令之一就是 `ls`。了解系统中文件所在目录中的内容非常重要。能够查看和修改不仅仅是一些文件还要所有文件也很重要。 + +我的第一个 Linux 备忘录是[单页 Linux 手册][1]，它于 1999 年发布，它成为我的首选参考资料。当我开始探索 Linux 时，我把它贴在桌子上并经常参考它。它的第一页第一列的底部有使用 `ls -l` 列出文件的命令。 + +之后，我将学习这个最基本命令的其他迭代。通过 `ls` 命令，我开始了解 Linux 文件权限的复杂性以及哪些是我的文件，哪些需要 root 或者 root 权限来修改。随着时间的推移，我习惯使用命令行，虽然我仍然使用 `ls -l` 来查找目录中的文件，但我经常使用 `ls -al`，这样我就可以看到可能需要更改的隐藏文件，比如那些配置文件。 + +根据 Eric Fischer 在[Linux 文档项目][2]中关于 `ls` 命令的文章，该命令的根源可以追溯到 1961年 MIT 的相容分时系统 （CTSS +） 上的 `listf` 命令。当 CTSS 被 [Multics][3] 代替时，命令变为 `list`，并有像 `list -all` 的开关。根据[维基百科][4]，“ls” 出现在 AT&T Unix 的原始版本中。我们今天在 Linux 系统上使用的 `ls` 命令来自 [GNU Core Utilities][5]。 + +大多数时候，我只使用几个迭代的命令。使用 `ls` 或 `ls -al` 查看目录内部是我通常使用该命令的方法，但是你还应该熟悉许多其他选项。 + +`$ ls -l` 提供了一个简单的目录列表： + +![](https://opensource.com/sites/default/files/uploads/linux_ls_1_0.png) + +使用我的 Fedora 28 系统中的手册页，我发现 `ls` 还有许多其他选项，所有这些选项都提供了有关 Linux 文件系统的有趣且有用的信息。通过在命令提示符下输入 `man ls`，我们可以开始探索其他一些选项： + +![](https://opensource.com/sites/default/files/uploads/linux_ls_2_0.png) + +要按文件大小对目录进行排序，请使用 `ls -lS`： + +![](https://opensource.com/sites/default/files/uploads/linux_ls_3_0.png) + +要以相反的顺序列出内容，请使用 `ls -lr`： + +![](https://opensource.com/sites/default/files/uploads/linux_ls_4.png) + +要按列列出内容，请使用 `ls -c`： + +![](https://opensource.com/sites/default/files/uploads/linux_ls_5.png) + +`ls -al` 提供了同一目录中所有文件的列表： + +![](https://opensource.com/sites/default/files/uploads/linux_ls_6.png) + +以下是我认为有用且有趣的一些其他选项： + + * 仅列出目录中的 .txt 文件：`ls * .txt` +  * 按文件大小列出：`ls -s` +  * 按时间和日期排序：`ls -d` +  * 按扩展名排序：`ls -X` +  * 按文件大小排序：`ls -S` +  * 带有文件大小的长格式：`ls -ls` + + + +要生成指定格式的目录列表并将其定向到文件供以后查看，请输入 `ls -al> mydirectorylist`。最后，我找到的一个更奇特的命令是 `ls -R`，它提供了计算机上所有目录及其内容的递归列表。 + +有关 `ls` 命令的所有迭代的完整列表，请参阅 [GNU Core Utilities][6]。 + +-------------------------------------------------------------------------------- + +via: https://opensource.com/article/18/10/ls-command + +作者：[Don Watkins][a] +选题：[lujun9972](https://github.com/lujun9972) +译者：[geekpi](https://github.com/geekpi) +校对：[校对者ID](https://github.com/校对者ID) + +本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出 + +[a]: https://opensource.com/users/don-watkins +[1]: http://hackerspace.cs.rutgers.edu/library/General/One_Page_Linux_Manual.pdf +[2]: http://www.tldp.org/LDP/LG/issue48/fischer.html +[3]: https://en.wikipedia.org/wiki/Multics +[4]: https://en.wikipedia.org/wiki/Ls +[5]: http://www.gnu.org/s/coreutils/ +[6]: https://www.gnu.org/software/coreutils/manual/html_node/ls-invocation.html#ls-invocation From 9e3e000850e898efde26b06da0cacf868042e848 Mon Sep 17 00:00:00 2001 From: geekpi Date: Tue, 16 Oct 2018 09:07:03 +0800 Subject: [PATCH 11/44] translating --- .../tech/20181013 How to Install GRUB on Arch Linux (UEFI).md | 2 ++ 1 file changed, 2 insertions(+) diff --git a/sources/tech/20181013 How to Install GRUB on Arch Linux (UEFI).md b/sources/tech/20181013 How to Install GRUB on Arch Linux (UEFI).md index 97cb5e0362..e456c1ee0e 100644 --- a/sources/tech/20181013 How to Install GRUB on Arch Linux (UEFI).md +++ b/sources/tech/20181013 How to Install GRUB on Arch Linux (UEFI).md @@ -1,3 +1,5 @@ +translating---geekpi + How to Install GRUB on Arch Linux (UEFI) ====== From 7c430e0a34873d2f7353f5557aac57f02311dcd5 Mon Sep 17 00:00:00 2001 From: darksun Date: Tue, 16 Oct 2018 09:08:29 +0800 Subject: [PATCH 12/44] =?UTF-8?q?=E9=80=89=E9=A2=98:=20Lab=205:=20File=20s?= =?UTF-8?q?ystem,=20Spawn=20and=20Shell?= MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit --- ...016 Lab 5- File system, Spawn and Shell.md | 345 ++++++++++++++++++ 1 file changed, 345 insertions(+) create mode 100644 sources/tech/20181016 Lab 5- File system, Spawn and Shell.md diff --git a/sources/tech/20181016 Lab 5- File system, Spawn and Shell.md b/sources/tech/20181016 Lab 5- File system, Spawn and Shell.md new file mode 100644 index 0000000000..e7e623db11 --- /dev/null +++ b/sources/tech/20181016 Lab 5- File system, Spawn and Shell.md @@ -0,0 +1,345 @@ +Lab 5: File system, Spawn and Shell +====== + +**Due Thursday, November 15, 2018 +** + +### Introduction + +In this lab, you will implement `spawn`, a library call that loads and runs on-disk executables. You will then flesh out your kernel and library operating system enough to run a shell on the console. These features need a file system, and this lab introduces a simple read/write file system. + +#### Getting Started + +Use Git to fetch the latest version of the course repository, and then create a local branch called `lab5` based on our lab5 branch, `origin/lab5`: + +``` + athena% cd ~/6.828/lab + athena% add git + athena% git pull + Already up-to-date. + athena% git checkout -b lab5 origin/lab5 + Branch lab5 set up to track remote branch refs/remotes/origin/lab5. + Switched to a new branch "lab5" + athena% git merge lab4 + Merge made by recursive. + ..... + athena% +``` + +The main new component for this part of the lab is the file system environment, located in the new `fs` directory. Scan through all the files in this directory to get a feel for what all is new. Also, there are some new file system-related source files in the `user` and `lib` directories, + +| fs/fs.c | Code that mainipulates the file system's on-disk structure. | +| fs/bc.c | A simple block cache built on top of our user-level page fault handling facility. | +| fs/ide.c | Minimal PIO-based (non-interrupt-driven) IDE driver code. | +| fs/serv.c | The file system server that interacts with client environments using file system IPCs. | +| lib/fd.c | Code that implements the general UNIX-like file descriptor interface. | +| lib/file.c | The driver for on-disk file type, implemented as a file system IPC client. | +| lib/console.c | The driver for console input/output file type. | +| lib/spawn.c | Code skeleton of the spawn library call. | + +You should run the pingpong, primes, and forktree test cases from lab 4 again after merging in the new lab 5 code. You will need to comment out the `ENV_CREATE(fs_fs)` line in `kern/init.c` because `fs/fs.c` tries to do some I/O, which JOS does not allow yet. Similarly, temporarily comment out the call to `close_all()` in `lib/exit.c`; this function calls subroutines that you will implement later in the lab, and therefore will panic if called. If your lab 4 code doesn't contain any bugs, the test cases should run fine. Don't proceed until they work. Don't forget to un-comment these lines when you start Exercise 1. + +If they don't work, use git diff lab4 to review all the changes, making sure there isn't any code you wrote for lab4 (or before) missing from lab 5. Make sure that lab 4 still works. + +#### Lab Requirements + +As before, you will need to do all of the regular exercises described in the lab and _at least one_ challenge problem. Additionally, you will need to write up brief answers to the questions posed in the lab and a short (e.g., one or two paragraph) description of what you did to solve your chosen challenge problem. If you implement more than one challenge problem, you only need to describe one of them in the write-up, though of course you are welcome to do more. Place the write-up in a file called `answers-lab5.txt` in the top level of your `lab5` directory before handing in your work. + +### File system preliminaries + +The file system you will work with is much simpler than most "real" file systems including that of xv6 UNIX, but it is powerful enough to provide the basic features: creating, reading, writing, and deleting files organized in a hierarchical directory structure. + +We are (for the moment anyway) developing only a single-user operating system, which provides protection sufficient to catch bugs but not to protect multiple mutually suspicious users from each other. Our file system therefore does not support the UNIX notions of file ownership or permissions. Our file system also currently does not support hard links, symbolic links, time stamps, or special device files like most UNIX file systems do. + +### On-Disk File System Structure + +Most UNIX file systems divide available disk space into two main types of regions: _inode_ regions and _data_ regions. UNIX file systems assign one _inode_ to each file in the file system; a file's inode holds critical meta-data about the file such as its `stat` attributes and pointers to its data blocks. The data regions are divided into much larger (typically 8KB or more) _data blocks_ , within which the file system stores file data and directory meta-data. Directory entries contain file names and pointers to inodes; a file is said to be _hard-linked_ if multiple directory entries in the file system refer to that file's inode. Since our file system will not support hard links, we do not need this level of indirection and therefore can make a convenient simplification: our file system will not use inodes at all and instead will simply store all of a file's (or sub-directory's) meta-data within the (one and only) directory entry describing that file. + +Both files and directories logically consist of a series of data blocks, which may be scattered throughout the disk much like the pages of an environment's virtual address space can be scattered throughout physical memory. The file system environment hides the details of block layout, presenting interfaces for reading and writing sequences of bytes at arbitrary offsets within files. The file system environment handles all modifications to directories internally as a part of performing actions such as file creation and deletion. Our file system does allow user environments to _read_ directory meta-data directly (e.g., with `read`), which means that user environments can perform directory scanning operations themselves (e.g., to implement the `ls` program) rather than having to rely on additional special calls to the file system. The disadvantage of this approach to directory scanning, and the reason most modern UNIX variants discourage it, is that it makes application programs dependent on the format of directory meta-data, making it difficult to change the file system's internal layout without changing or at least recompiling application programs as well. + +#### Sectors and Blocks + +Most disks cannot perform reads and writes at byte granularity and instead perform reads and writes in units of _sectors_. In JOS, sectors are 512 bytes each. File systems actually allocate and use disk storage in units of _blocks_. Be wary of the distinction between the two terms: _sector size_ is a property of the disk hardware, whereas _block size_ is an aspect of the operating system using the disk. A file system's block size must be a multiple of the sector size of the underlying disk. + +The UNIX xv6 file system uses a block size of 512 bytes, the same as the sector size of the underlying disk. Most modern file systems use a larger block size, however, because storage space has gotten much cheaper and it is more efficient to manage storage at larger granularities. Our file system will use a block size of 4096 bytes, conveniently matching the processor's page size. + +#### Superblocks + +![Disk layout][1] + +File systems typically reserve certain disk blocks at "easy-to-find" locations on the disk (such as the very start or the very end) to hold meta-data describing properties of the file system as a whole, such as the block size, disk size, any meta-data required to find the root directory, the time the file system was last mounted, the time the file system was last checked for errors, and so on. These special blocks are called _superblocks_. + +Our file system will have exactly one superblock, which will always be at block 1 on the disk. Its layout is defined by `struct Super` in `inc/fs.h`. Block 0 is typically reserved to hold boot loaders and partition tables, so file systems generally do not use the very first disk block. Many "real" file systems maintain multiple superblocks, replicated throughout several widely-spaced regions of the disk, so that if one of them is corrupted or the disk develops a media error in that region, the other superblocks can still be found and used to access the file system. + +#### File Meta-data + +![File structure][2] +The layout of the meta-data describing a file in our file system is described by `struct File` in `inc/fs.h`. This meta-data includes the file's name, size, type (regular file or directory), and pointers to the blocks comprising the file. As mentioned above, we do not have inodes, so this meta-data is stored in a directory entry on disk. Unlike in most "real" file systems, for simplicity we will use this one `File` structure to represent file meta-data as it appears _both on disk and in memory_. + +The `f_direct` array in `struct File` contains space to store the block numbers of the first 10 (`NDIRECT`) blocks of the file, which we call the file's _direct_ blocks. For small files up to 10*4096 = 40KB in size, this means that the block numbers of all of the file's blocks will fit directly within the `File` structure itself. For larger files, however, we need a place to hold the rest of the file's block numbers. For any file greater than 40KB in size, therefore, we allocate an additional disk block, called the file's _indirect block_ , to hold up to 4096/4 = 1024 additional block numbers. Our file system therefore allows files to be up to 1034 blocks, or just over four megabytes, in size. To support larger files, "real" file systems typically support _double-_ and _triple-indirect blocks_ as well. + +#### Directories versus Regular Files + +A `File` structure in our file system can represent either a _regular_ file or a directory; these two types of "files" are distinguished by the `type` field in the `File` structure. The file system manages regular files and directory-files in exactly the same way, except that it does not interpret the contents of the data blocks associated with regular files at all, whereas the file system interprets the contents of a directory-file as a series of `File` structures describing the files and subdirectories within the directory. + +The superblock in our file system contains a `File` structure (the `root` field in `struct Super`) that holds the meta-data for the file system's root directory. The contents of this directory-file is a sequence of `File` structures describing the files and directories located within the root directory of the file system. Any subdirectories in the root directory may in turn contain more `File` structures representing sub-subdirectories, and so on. + +### The File System + +The goal for this lab is not to have you implement the entire file system, but for you to implement only certain key components. In particular, you will be responsible for reading blocks into the block cache and flushing them back to disk; allocating disk blocks; mapping file offsets to disk blocks; and implementing read, write, and open in the IPC interface. Because you will not be implementing all of the file system yourself, it is very important that you familiarize yourself with the provided code and the various file system interfaces. + +### Disk Access + +The file system environment in our operating system needs to be able to access the disk, but we have not yet implemented any disk access functionality in our kernel. Instead of taking the conventional "monolithic" operating system strategy of adding an IDE disk driver to the kernel along with the necessary system calls to allow the file system to access it, we instead implement the IDE disk driver as part of the user-level file system environment. We will still need to modify the kernel slightly, in order to set things up so that the file system environment has the privileges it needs to implement disk access itself. + +It is easy to implement disk access in user space this way as long as we rely on polling, "programmed I/O" (PIO)-based disk access and do not use disk interrupts. It is possible to implement interrupt-driven device drivers in user mode as well (the L3 and L4 kernels do this, for example), but it is more difficult since the kernel must field device interrupts and dispatch them to the correct user-mode environment. + +The x86 processor uses the IOPL bits in the EFLAGS register to determine whether protected-mode code is allowed to perform special device I/O instructions such as the IN and OUT instructions. Since all of the IDE disk registers we need to access are located in the x86's I/O space rather than being memory-mapped, giving "I/O privilege" to the file system environment is the only thing we need to do in order to allow the file system to access these registers. In effect, the IOPL bits in the EFLAGS register provides the kernel with a simple "all-or-nothing" method of controlling whether user-mode code can access I/O space. In our case, we want the file system environment to be able to access I/O space, but we do not want any other environments to be able to access I/O space at all. + +``` +Exercise 1. `i386_init` identifies the file system environment by passing the type `ENV_TYPE_FS` to your environment creation function, `env_create`. Modify `env_create` in `env.c`, so that it gives the file system environment I/O privilege, but never gives that privilege to any other environment. + +Make sure you can start the file environment without causing a General Protection fault. You should pass the "fs i/o" test in make grade. +``` + +``` +Question + + 1. Do you have to do anything else to ensure that this I/O privilege setting is saved and restored properly when you subsequently switch from one environment to another? Why? +``` + + +Note that the `GNUmakefile` file in this lab sets up QEMU to use the file `obj/kern/kernel.img` as the image for disk 0 (typically "Drive C" under DOS/Windows) as before, and to use the (new) file `obj/fs/fs.img` as the image for disk 1 ("Drive D"). In this lab our file system should only ever touch disk 1; disk 0 is used only to boot the kernel. If you manage to corrupt either disk image in some way, you can reset both of them to their original, "pristine" versions simply by typing: + +``` + $ rm obj/kern/kernel.img obj/fs/fs.img + $ make +``` + +or by doing: + +``` + $ make clean + $ make +``` + +Challenge! Implement interrupt-driven IDE disk access, with or without DMA. You can decide whether to move the device driver into the kernel, keep it in user space along with the file system, or even (if you really want to get into the micro-kernel spirit) move it into a separate environment of its own. + +### The Block Cache + +In our file system, we will implement a simple "buffer cache" (really just a block cache) with the help of the processor's virtual memory system. The code for the block cache is in `fs/bc.c`. + +Our file system will be limited to handling disks of size 3GB or less. We reserve a large, fixed 3GB region of the file system environment's address space, from 0x10000000 (`DISKMAP`) up to 0xD0000000 (`DISKMAP+DISKMAX`), as a "memory mapped" version of the disk. For example, disk block 0 is mapped at virtual address 0x10000000, disk block 1 is mapped at virtual address 0x10001000, and so on. The `diskaddr` function in `fs/bc.c` implements this translation from disk block numbers to virtual addresses (along with some sanity checking). + +Since our file system environment has its own virtual address space independent of the virtual address spaces of all other environments in the system, and the only thing the file system environment needs to do is to implement file access, it is reasonable to reserve most of the file system environment's address space in this way. It would be awkward for a real file system implementation on a 32-bit machine to do this since modern disks are larger than 3GB. Such a buffer cache management approach may still be reasonable on a machine with a 64-bit address space. + +Of course, it would take a long time to read the entire disk into memory, so instead we'll implement a form of _demand paging_ , wherein we only allocate pages in the disk map region and read the corresponding block from the disk in response to a page fault in this region. This way, we can pretend that the entire disk is in memory. + +``` +Exercise 2. Implement the `bc_pgfault` and `flush_block` functions in `fs/bc.c`. `bc_pgfault` is a page fault handler, just like the one your wrote in the previous lab for copy-on-write fork, except that its job is to load pages in from the disk in response to a page fault. When writing this, keep in mind that (1) `addr` may not be aligned to a block boundary and (2) `ide_read` operates in sectors, not blocks. + +The `flush_block` function should write a block out to disk _if necessary_. `flush_block` shouldn't do anything if the block isn't even in the block cache (that is, the page isn't mapped) or if it's not dirty. We will use the VM hardware to keep track of whether a disk block has been modified since it was last read from or written to disk. To see whether a block needs writing, we can just look to see if the `PTE_D` "dirty" bit is set in the `uvpt` entry. (The `PTE_D` bit is set by the processor in response to a write to that page; see 5.2.4.3 in [chapter 5][3] of the 386 reference manual.) After writing the block to disk, `flush_block` should clear the `PTE_D` bit using `sys_page_map`. + +Use make grade to test your code. Your code should pass "check_bc", "check_super", and "check_bitmap". +``` + +`fs_init` function in `fs/fs.c` is a prime example of how to use the block cache. After initializing the block cache, it simply stores pointers into the disk map region in the `super` global variable. After this point, we can simply read from the `super` structure as if they were in memory and our page fault handler will read them from disk as necessary. + +``` +Challenge! The block cache has no eviction policy. Once a block gets faulted in to it, it never gets removed and will remain in memory forevermore. Add eviction to the buffer cache. Using the `PTE_A` "accessed" bits in the page tables, which the hardware sets on any access to a page, you can track approximate usage of disk blocks without the need to modify every place in the code that accesses the disk map region. Be careful with dirty blocks. +``` + +### The Block Bitmap + +After `fs_init` sets the `bitmap` pointer, we can treat `bitmap` as a packed array of bits, one for each block on the disk. See, for example, `block_is_free`, which simply checks whether a given block is marked free in the bitmap. + +``` +Exercise 3. Use `free_block` as a model to implement `alloc_block` in `fs/fs.c`, which should find a free disk block in the bitmap, mark it used, and return the number of that block. When you allocate a block, you should immediately flush the changed bitmap block to disk with `flush_block`, to help file system consistency. + +Use make grade to test your code. Your code should now pass "alloc_block". +``` + +### File Operations + +We have provided a variety of functions in `fs/fs.c` to implement the basic facilities you will need to interpret and manage `File` structures, scan and manage the entries of directory-files, and walk the file system from the root to resolve an absolute pathname. Read through _all_ of the code in `fs/fs.c` and make sure you understand what each function does before proceeding. + +``` +Exercise 4. Implement `file_block_walk` and `file_get_block`. `file_block_walk` maps from a block offset within a file to the pointer for that block in the `struct File` or the indirect block, very much like what `pgdir_walk` did for page tables. `file_get_block` goes one step further and maps to the actual disk block, allocating a new one if necessary. + +Use make grade to test your code. Your code should pass "file_open", "file_get_block", and "file_flush/file_truncated/file rewrite", and "testfile". +``` + +`file_block_walk` and `file_get_block` are the workhorses of the file system. For example, `file_read` and `file_write` are little more than the bookkeeping atop `file_get_block` necessary to copy bytes between scattered blocks and a sequential buffer. + +``` +Challenge! The file system is likely to be corrupted if it gets interrupted in the middle of an operation (for example, by a crash or a reboot). Implement soft updates or journalling to make the file system crash-resilient and demonstrate some situation where the old file system would get corrupted, but yours doesn't. +``` + +### The file system interface + +Now that we have the necessary functionality within the file system environment itself, we must make it accessible to other environments that wish to use the file system. Since other environments can't directly call functions in the file system environment, we'll expose access to the file system environment via a _remote procedure call_ , or RPC, abstraction, built atop JOS's IPC mechanism. Graphically, here's what a call to the file system server (say, read) looks like + +``` + Regular env FS env + +---------------+ +---------------+ + | read | | file_read | + | (lib/fd.c) | | (fs/fs.c) | +...|.......|.......|...|.......^.......|............... + | v | | | | RPC mechanism + | devfile_read | | serve_read | + | (lib/file.c) | | (fs/serv.c) | + | | | | ^ | + | v | | | | + | fsipc | | serve | + | (lib/file.c) | | (fs/serv.c) | + | | | | ^ | + | v | | | | + | ipc_send | | ipc_recv | + | | | | ^ | + +-------|-------+ +-------|-------+ + | | + +-------------------+ + +``` + +Everything below the dotted line is simply the mechanics of getting a read request from the regular environment to the file system environment. Starting at the beginning, `read` (which we provide) works on any file descriptor and simply dispatches to the appropriate device read function, in this case `devfile_read` (we can have more device types, like pipes). `devfile_read` implements `read` specifically for on-disk files. This and the other `devfile_*` functions in `lib/file.c` implement the client side of the FS operations and all work in roughly the same way, bundling up arguments in a request structure, calling `fsipc` to send the IPC request, and unpacking and returning the results. The `fsipc` function simply handles the common details of sending a request to the server and receiving the reply. + +The file system server code can be found in `fs/serv.c`. It loops in the `serve` function, endlessly receiving a request over IPC, dispatching that request to the appropriate handler function, and sending the result back via IPC. In the read example, `serve` will dispatch to `serve_read`, which will take care of the IPC details specific to read requests such as unpacking the request structure and finally call `file_read` to actually perform the file read. + +Recall that JOS's IPC mechanism lets an environment send a single 32-bit number and, optionally, share a page. To send a request from the client to the server, we use the 32-bit number for the request type (the file system server RPCs are numbered, just like how syscalls were numbered) and store the arguments to the request in a `union Fsipc` on the page shared via the IPC. On the client side, we always share the page at `fsipcbuf`; on the server side, we map the incoming request page at `fsreq` (`0x0ffff000`). + +The server also sends the response back via IPC. We use the 32-bit number for the function's return code. For most RPCs, this is all they return. `FSREQ_READ` and `FSREQ_STAT` also return data, which they simply write to the page that the client sent its request on. There's no need to send this page in the response IPC, since the client shared it with the file system server in the first place. Also, in its response, `FSREQ_OPEN` shares with the client a new "Fd page". We'll return to the file descriptor page shortly. + +``` +Exercise 5. Implement `serve_read` in `fs/serv.c`. + +`serve_read`'s heavy lifting will be done by the already-implemented `file_read` in `fs/fs.c` (which, in turn, is just a bunch of calls to `file_get_block`). `serve_read` just has to provide the RPC interface for file reading. Look at the comments and code in `serve_set_size` to get a general idea of how the server functions should be structured. + +Use make grade to test your code. Your code should pass "serve_open/file_stat/file_close" and "file_read" for a score of 70/150. +``` + +``` +Exercise 6. Implement `serve_write` in `fs/serv.c` and `devfile_write` in `lib/file.c`. + +Use make grade to test your code. Your code should pass "file_write", "file_read after file_write", "open", and "large file" for a score of 90/150. +``` + +### Spawning Processes + +We have given you the code for `spawn` (see `lib/spawn.c`) which creates a new environment, loads a program image from the file system into it, and then starts the child environment running this program. The parent process then continues running independently of the child. The `spawn` function effectively acts like a `fork` in UNIX followed by an immediate `exec` in the child process. + +We implemented `spawn` rather than a UNIX-style `exec` because `spawn` is easier to implement from user space in "exokernel fashion", without special help from the kernel. Think about what you would have to do in order to implement `exec` in user space, and be sure you understand why it is harder. + +``` +Exercise 7. `spawn` relies on the new syscall `sys_env_set_trapframe` to initialize the state of the newly created environment. Implement `sys_env_set_trapframe` in `kern/syscall.c` (don't forget to dispatch the new system call in `syscall()`). + +Test your code by running the `user/spawnhello` program from `kern/init.c`, which will attempt to spawn `/hello` from the file system. + +Use make grade to test your code. +``` + +``` +Challenge! Implement Unix-style `exec`. +``` + +``` +Challenge! Implement `mmap`-style memory-mapped files and modify `spawn` to map pages directly from the ELF image when possible. +``` + +### Sharing library state across fork and spawn + +The UNIX file descriptors are a general notion that also encompasses pipes, console I/O, etc. In JOS, each of these device types has a corresponding `struct Dev`, with pointers to the functions that implement read/write/etc. for that device type. `lib/fd.c` implements the general UNIX-like file descriptor interface on top of this. Each `struct Fd` indicates its device type, and most of the functions in `lib/fd.c` simply dispatch operations to functions in the appropriate `struct Dev`. + +`lib/fd.c` also maintains the _file descriptor table_ region in each application environment's address space, starting at `FDTABLE`. This area reserves a page's worth (4KB) of address space for each of the up to `MAXFD` (currently 32) file descriptors the application can have open at once. At any given time, a particular file descriptor table page is mapped if and only if the corresponding file descriptor is in use. Each file descriptor also has an optional "data page" in the region starting at `FILEDATA`, which devices can use if they choose. + +We would like to share file descriptor state across `fork` and `spawn`, but file descriptor state is kept in user-space memory. Right now, on `fork`, the memory will be marked copy-on-write, so the state will be duplicated rather than shared. (This means environments won't be able to seek in files they didn't open themselves and that pipes won't work across a fork.) On `spawn`, the memory will be left behind, not copied at all. (Effectively, the spawned environment starts with no open file descriptors.) + +We will change `fork` to know that certain regions of memory are used by the "library operating system" and should always be shared. Rather than hard-code a list of regions somewhere, we will set an otherwise-unused bit in the page table entries (just like we did with the `PTE_COW` bit in `fork`). + +We have defined a new `PTE_SHARE` bit in `inc/lib.h`. This bit is one of the three PTE bits that are marked "available for software use" in the Intel and AMD manuals. We will establish the convention that if a page table entry has this bit set, the PTE should be copied directly from parent to child in both `fork` and `spawn`. Note that this is different from marking it copy-on-write: as described in the first paragraph, we want to make sure to _share_ updates to the page. + +``` +Exercise 8. Change `duppage` in `lib/fork.c` to follow the new convention. If the page table entry has the `PTE_SHARE` bit set, just copy the mapping directly. (You should use `PTE_SYSCALL`, not `0xfff`, to mask out the relevant bits from the page table entry. `0xfff` picks up the accessed and dirty bits as well.) + +Likewise, implement `copy_shared_pages` in `lib/spawn.c`. It should loop through all page table entries in the current process (just like `fork` did), copying any page mappings that have the `PTE_SHARE` bit set into the child process. +``` + +Use make run-testpteshare to check that your code is behaving properly. You should see lines that say "`fork handles PTE_SHARE right`" and "`spawn handles PTE_SHARE right`". + +Use make run-testfdsharing to check that file descriptors are shared properly. You should see lines that say "`read in child succeeded`" and "`read in parent succeeded`". + +### The keyboard interface + +For the shell to work, we need a way to type at it. QEMU has been displaying output we write to the CGA display and the serial port, but so far we've only taken input while in the kernel monitor. In QEMU, input typed in the graphical window appear as input from the keyboard to JOS, while input typed to the console appear as characters on the serial port. `kern/console.c` already contains the keyboard and serial drivers that have been used by the kernel monitor since lab 1, but now you need to attach these to the rest of the system. + +``` +Exercise 9. In your `kern/trap.c`, call `kbd_intr` to handle trap `IRQ_OFFSET+IRQ_KBD` and `serial_intr` to handle trap `IRQ_OFFSET+IRQ_SERIAL`. +``` + +We implemented the console input/output file type for you, in `lib/console.c`. `kbd_intr` and `serial_intr` fill a buffer with the recently read input while the console file type drains the buffer (the console file type is used for stdin/stdout by default unless the user redirects them). + +Test your code by running make run-testkbd and type a few lines. The system should echo your lines back to you as you finish them. Try typing in both the console and the graphical window, if you have both available. + +### The Shell + +Run make run-icode or make run-icode-nox. This will run your kernel and start `user/icode`. `icode` execs `init`, which will set up the console as file descriptors 0 and 1 (standard input and standard output). It will then spawn `sh`, the shell. You should be able to run the following commands: + +``` + echo hello world | cat + cat lorem |cat + cat lorem |num + cat lorem |num |num |num |num |num + lsfd +``` + +Note that the user library routine `cprintf` prints straight to the console, without using the file descriptor code. This is great for debugging but not great for piping into other programs. To print output to a particular file descriptor (for example, 1, standard output), use `fprintf(1, "...", ...)`. `printf("...", ...)` is a short-cut for printing to FD 1. See `user/lsfd.c` for examples. + +``` +Exercise 10. + +The shell doesn't support I/O redirection. It would be nice to run sh