Hello up there. On the list Grischka made a point that we can't recommend using
-b as long as tcc -b tcc.c doesn't produce anything useful. Now it does, so
please don't treat -b mode as second class citizen anymore.
Thanks,
Kirill
* bcheck2:
tests: Add tests for compile/run tcc.c with `tcc -b` then compile tcc.c again, then run tcctest.c
lib/bcheck: Fix code typo in __bound_delete_region()
lib/bcheck: Don't assume heap goes right after bss
Make tcc work after self-compiling with bounds-check enabled
Just like with test[123] add their test[123]b variants. After previous 3
patchs all test pass here on Debian GNU/Linux on i385 with gcc-4.7 with
or without memory randomization turned on.
We were calling get_page() with t2 index which is not correct, since
get_page() operate on t1 indices. The bug is here from day-1, from
60f781c4 (first version of bounds checker) and show as a crash in
__bound_delete_region() at program exit:
$ ./tcc -B. -DTCC_TARGET_I386 -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" -b -run -DONE_SOURCE \
./tcc.c -B. -DTCC_TARGET_I386 -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" -run -DONE_SOURCE \
./tcc.c -B. -run tests/tcctest.c
(lot's of correct output from tcctest)
Runtime error: dereferencing invalid pointer
at 0xa7c21cc4 __bound_delete_region()
by (nil) ???
Segmentation fault
The fix is simple - last page should be get through t1_end, like it is
done in __bound_new_region().
After this patch, tcc is being able to compile itself with -b, then
compile itself again and run tcctest with correct output. Tests follow.
At startup __bound_init() wants to mark malloc zone as invalid memory,
so that any access to memory on heap, not allocated through malloc be
invalid. Other pages are initialized as empty regions, access to which
is not treated as invalid by bounds-checking.
The problem is code incorrectly assumed that heap goes right after bss,
and that is not correct for two cases:
1) if we are running from `tcc -b -run`, program text data and bss
will be already in malloced memory, possibly in mmaped region
insead of heap, and marking memory as invalid from _end
will not cover heap and probably wrongly mark correct regions.
2) if address space randomization is turned on, again heap does not
start from _end, and we'll mark as invalid something else instead
of malloc area.
For example with the following diagnostic patch ...
diff --git a/tcc.c b/tcc.c
index 5dd5725..31c46e8 100644
--- a/tcc.c
+++ b/tcc.c
@@ -479,6 +479,8 @@ static int parse_args(TCCState *s, int argc, char **argv)
return optind;
}
+extern int _etext, _edata, _end;
+
int main(int argc, char **argv)
{
int i;
@@ -487,6 +489,18 @@ int main(int argc, char **argv)
int64_t start_time = 0;
const char *default_file = NULL;
+ void *brk;
+
+ brk = sbrk(0);
+
+ fprintf(stderr, "\n>>> TCC\n\n");
+ fprintf(stderr, "etext:\t%10p\n", &_etext);
+ fprintf(stderr, "edata:\t%10p\n", &_edata);
+ fprintf(stderr, "end:\t%10p\n", &_end);
+ fprintf(stderr, "brk:\t%10p\n", brk);
+ fprintf(stderr, "stack:\t%10p\n", &brk);
+
+ fprintf(stderr, "&errno: %p\n", &errno);
s = tcc_new();
output_type = TCC_OUTPUT_EXE;
diff --git a/tccrun.c b/tccrun.c
index 531f46a..25ed30a 100644
--- a/tccrun.c
+++ b/tccrun.c
@@ -91,6 +91,8 @@ LIBTCCAPI int tcc_run(TCCState *s1, int argc, char **argv)
int (*prog_main)(int, char **);
int ret;
+ fprintf(stderr, "\n\ntcc_run() ...\n\n");
+
if (tcc_relocate(s1, TCC_RELOCATE_AUTO) < 0)
return -1;
diff --git a/lib/bcheck.c b/lib/bcheck.c
index ea5b233..8b26a5f 100644
--- a/lib/bcheck.c
+++ b/lib/bcheck.c
@@ -296,6 +326,8 @@ static void mark_invalid(unsigned long addr, unsigned long size)
start = addr;
end = addr + size;
+ fprintf(stderr, "mark_invalid %10p - %10p\n", (void *)addr, (void *)end);
+
t2_start = (start + BOUND_T3_SIZE - 1) >> BOUND_T3_BITS;
if (end != 0)
t2_end = end >> BOUND_T3_BITS;
... Look how memory is laid out for `tcc -b -run ...`:
$ ./tcc -B. -b -DTCC_TARGET_I386 -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" -run \
-DONE_SOURCE ./tcc.c -B. -c x.c
>>> TCC
etext: 0x8065477
edata: 0x8070220
end: 0x807a95c
brk: 0x807b000
stack: 0xaffff0f0
&errno: 0xa7e25688
tcc_run() ...
mark_invalid 0xfff80000 - (nil)
mark_invalid 0xa7c31d98 - 0xafc31d98
>>> TCC
etext: 0xa7c22767
edata: 0xa7c2759c
end: 0xa7c31d98
brk: 0x8211000
stack: 0xafffeff0
&errno: 0xa7e25688
Runtime error: dereferencing invalid pointer
./tccpp.c:1953: at 0xa7beebdf parse_number() (included from ./libtcc.c, ./tcc.c)
./tccpp.c:3003: by 0xa7bf0708 next() (included from ./libtcc.c, ./tcc.c)
./tccgen.c:4465: by 0xa7bfe348 block() (included from ./libtcc.c, ./tcc.c)
./tccgen.c:4440: by 0xa7bfe212 block() (included from ./libtcc.c, ./tcc.c)
./tccgen.c:5529: by 0xa7c01929 gen_function() (included from ./libtcc.c, ./tcc.c)
./tccgen.c:5767: by 0xa7c02602 decl0() (included from ./libtcc.c, ./tcc.c)
The second mark_invalid goes right after in-memory-compiled program's
_end, and oops, that's not where malloc zone is (starts from brk), and oops
again, mark_invalid covers e.g. errno. Then compiled tcc is crasshing by
bcheck on errno access:
1776 static void parse_number(const char *p)
1777 {
1778 int b, t, shift, frac_bits, s, exp_val, ch;
...
1951 *q = '\0';
1952 t = toup(ch);
1953 errno = 0;
The solution here is to use sbrk(0) as approximation for the program
break start instead of &_end:
- if we are a separately compiled program, __bound_init() runs early,
and sbrk(0) should be equal or very near to start_brk (in case other
constructors malloc something), or
- if we are running from under `tcc -b -run`, sbrk(0) will return
start of heap portion which is under this program control, and not
mark as invalid earlier allocated memory.
With this patch `tcc -b -run tcc.c ...` succeeds compiling above
small-test program (diagnostic patch is still applied too):
$ ./tcc -B. -b -DTCC_TARGET_I386 -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" -run \
-DONE_SOURCE ./tcc.c -B. -c x.c
>>> TCC
etext: 0x8065477
edata: 0x8070220
end: 0x807a95c
brk: 0x807b000
stack: 0xaffff0f0
&errno: 0xa7e25688
tcc_run() ...
mark_invalid 0xfff80000 - (nil)
mark_invalid 0x8211000 - 0x10211000
>>> TCC
etext: 0xa7c22777
edata: 0xa7c275ac
end: 0xa7c31da8
brk: 0x8211000
stack: 0xafffeff0
&errno: 0xa7e25688
(completes ok)
but running `tcc -b -run tcc.c -run tests/tcctest.c` sigsegv's - that's
the plot for the next patch.
For vstack Fabrice used the trick to initialize vtop to &vstack[-1], so
that on first push, vtop becomes &vstack[0] and a value is also stored
there - everything works.
Except that when tcc is compiled with bounds-checking enabled, vstack - 1
returns INVALID_POINTER and oops...
Let's workaround it with artificial 1 vstack slot which will not be
used, but only serve as an indicator that pointing to &vstack[-1] is ok.
Now, tcc, after being self-compiled with -b works:
$ ./tcc -B. -o tccb -DONE_SOURCE -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" tcc.c -ldl
$ cd tests
$ ../tcc -B.. -run tcctest.c >1
$ ../tccb -B.. -run tcctest.c >2
$ diff -u 1 2
and note, tcc's compilation speed is not affected:
$ ./tcc -B. -bench -DONE_SOURCE -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" -c tcc.c
before: 8270 idents, 47221 lines, 1527730 bytes, 0.152 s, 309800 lines/s, 10.0 MB/s
after: 8271 idents, 47221 lines, 1527733 bytes, 0.152 s, 310107 lines/s, 10.0 MB/s
But note, that `tcc -b -run tcc` is still broken - for example it crashes
on
$ cat x.c
double get100 () { return 100.0; }
$ ./tcc -B. -b -DTCC_TARGET_I386 -DCONFIG_MULTIARCHDIR=\"i386-linux-gnu\" -run \
-DONE_SOURCE ./tcc.c -B. -c x.c
Runtime error: dereferencing invalid pointer
./tccpp.c:1953: at 0xa7beebdf parse_number() (included from ./libtcc.c, ./tcc.c)
./tccpp.c:3003: by 0xa7bf0708 next() (included from ./libtcc.c, ./tcc.c)
./tccgen.c:4465: by 0xa7bfe348 block() (included from ./libtcc.c, ./tcc.c)
./tccgen.c:4440: by 0xa7bfe212 block() (included from ./libtcc.c, ./tcc.c)
./tccgen.c:5529: by 0xa7c01929 gen_function() (included from ./libtcc.c, ./tcc.c)
./tccgen.c:5767: by 0xa7c02602 decl0() (included from ./libtcc.c, ./tcc.c)
that's because lib/bcheck.c runtime needs more fixes -- see next
patches.
After 40a54c43 (Repair bounds-checking runtime), and in particular
5d648485 (Now btest pass!) `make test` was broken on ARCH != i386,
because I've changed btest to unconditionally run on all arches.
But bounds-checking itsels is only supported on i386 and oops...
Fix it.
Reported-by: Thomas Preud'homme <robotux@celest.fr>
The following files were not ignored (produced by build on i386 with
--enable-cross):
arm-eabi-tcc
arm-fpa-ld-tcc
arm-fpa-tcc
arm-vfp-tcc
c67-tcc
i386-win32-tcc
lib/i386-win32/
lib/x86_64-win32/
x86_64-tcc
x86_64-win32-tcc
A line in gfunc_call in arm-gen.c is referencing vfpr unconditionally.
Yet, this function is only available when TCC_ARM_VFP is set. While this
code is only triggered when TCC_ARM_VFP, it fails at compile time. This
commit fix the problem.
TCC_ARM_EABI should be defined when compiling with hardfloat calling
convention. This commit rework the Makefile to distinguish between
calling convention and multiarch and define TCC_ARM_EABI when hardfloat
calling convention is used. The result is to first guess the calling
convention and then add the multiarch triplet if necessary.
Continuing d6072d37 (Add __builtin_frame_address(0)) implement
__builtin_frame_address for levels greater than zero, in order for
tinycc to be able to compile its own lib/bcheck.c after
cffb7af9 (lib/bcheck: Prevent __bound_local_new / __bound_local_delete
from being miscompiled).
I'm new to the internals, and used the most simple way to do it.
Generated code is not very good for levels >= 2, compare
gcc tcc
level=0 mov %ebp,%eax lea 0x0(%ebp),%eax
level=1 mov 0x0(%ebp),%eax mov 0x0(%ebp),%eax
level=2 mov 0x0(%ebp),%eax mov 0x0(%ebp),%eax
mov (%eax),%eax mov %eax,-0x10(%ebp)
mov -0x10(%ebp),%eax
mov (%eax),%eax
level=3 mov 0x0(%ebp),%eax mov 0x0(%ebp),%eax
mov (%eax),%eax mov (%eax),%ecx
mov (%eax),%eax mov (%ecx),%eax
But this is still an improvement and for bcheck we need level=1 for
which the code is good.
For the tests I had to force gcc use -O0 to not inline the functions.
And -fno-omit-frame-pointer just in case.
If someone knows how to improve the generated code - help is
appreciated.
Thanks,
Kirill
Cc: Michael Matz <matz@suse.de>
Cc: Shinichiro Hamaji <shinichiro.hamaji@gmail.com>
This option does not exist in gcc 4.3 and earlier, and it breaks the build on
systems with older compilers. The makefile has been enhanced to test for the
version and adds it only if a newer compiler is detected.
On this weekend a thought came to me again that tinycc could be used for
scripting. Only its bounds-checking mode turned out to be broken, which
is a pity because bounds-checking is sometimes handy especially for
quickly written scripts.
Since tinycc is one of those small beautiful things, seldomly happening
in our times, I couldn't resist trying to fix it.
Thanks,
Kirill
* bcheck:
Now btest pass!
lib/bcheck: Prevent __bound_local_new / __bound_local_delete from being miscompiled
lib/bcheck: Prevent libc_malloc/libc_free etc from being miscompiled
On i386 and gcc-4.7 I found that __bound_local_new was miscompiled -
look:
#ifdef __i386__
/* return the frame pointer of the caller */
#define GET_CALLER_FP(fp)\
{\
unsigned long *fp1;\
__asm__ __volatile__ ("movl %%ebp,%0" :"=g" (fp1));\
fp = fp1[0];\
}
#endif
/* called when entering a function to add all the local regions */
void FASTCALL __bound_local_new(void *p1)
{
unsigned long addr, size, fp, *p = p1;
GET_CALLER_FP(fp);
for(;;) {
addr = p[0];
if (addr == 0)
break;
addr += fp;
size = p[1];
p += 2;
__bound_new_region((void *)addr, size);
}
}
__bound_local_new:
.LFB40:
.cfi_startproc
pushl %esi
.cfi_def_cfa_offset 8
.cfi_offset 6, -8
pushl %ebx
.cfi_def_cfa_offset 12
.cfi_offset 3, -12
subl $8, %esp // NOTE prologue does not touch %ebp
.cfi_def_cfa_offset 20
#APP
# 235 "lib/bcheck.c" 1
movl %ebp,%edx // %ebp -> fp1
# 0 "" 2
#NO_APP
movl (%edx), %esi // fp1[0] -> fp
movl (%eax), %edx
movl %eax, %ebx
testl %edx, %edx
je .L167
.p2align 2,,3
.L173:
movl 4(%ebx), %eax
addl $8, %ebx
movl %eax, 4(%esp)
addl %esi, %edx
movl %edx, (%esp)
call __bound_new_region
movl (%ebx), %edx
testl %edx, %edx
jne .L173
.L167:
addl $8, %esp
.cfi_def_cfa_offset 12
popl %ebx
.cfi_restore 3
.cfi_def_cfa_offset 8
popl %esi
.cfi_restore 6
.cfi_def_cfa_offset 4
ret
here GET_CALLER_FP() assumed that its using function setups it's stack
frame, i.e. first save, then set %ebp to stack frame start, and then it
has to do perform two lookups: 1) to get current stack frame through
%ebp, and 2) get caller stack frame through (%ebp).
And here is the problem: gcc decided not to setup %ebp for
__bound_local_new and in such case GET_CALLER_FP actually becomes
GET_CALLER_CALLER_FP and oops, wrong regions are registered in bcheck
tables...
The solution is to stop using hand written assembly and rely on gcc's
__builtin_frame_address(1) to get callers frame stack(*). I think for the
builtin gcc should generate correct code, independent of whether it
decides or not to omit frame pointer in using function - it knows it.
(*) judging by gcc history, __builtin_frame_address was there almost
from the beginning - at least it is present in 1992 as seen from the
following commit:
http://gcc.gnu.org/git/?p=gcc.git;a=commit;h=be07f7bdbac76d87d3006c89855491504d5d6202
so we can rely on it being supported by all versions of gcc.
In my environment the assembly of __bound_local_new changes as follows:
diff --git a/bcheck0.s b/bcheck1.s
index 4c02a5f..ef68918 100644
--- a/bcheck0.s
+++ b/bcheck1.s
@@ -1409,20 +1409,17 @@ __bound_init:
__bound_local_new:
.LFB40:
.cfi_startproc
- pushl %esi
+ pushl %ebp // NOTE prologue saves %ebp ...
.cfi_def_cfa_offset 8
- .cfi_offset 6, -8
+ .cfi_offset 5, -8
+ movl %esp, %ebp // ... and reset it to local stack frame
+ .cfi_def_cfa_register 5
+ pushl %esi
pushl %ebx
- .cfi_def_cfa_offset 12
- .cfi_offset 3, -12
subl $8, %esp
- .cfi_def_cfa_offset 20
-#APP
-# 235 "lib/bcheck.c" 1
- movl %ebp,%edx
-# 0 "" 2
-#NO_APP
- movl (%edx), %esi
+ .cfi_offset 6, -12
+ .cfi_offset 3, -16
+ movl 0(%ebp), %esi // stkframe -> stkframe.parent -> fp
movl (%eax), %edx
movl %eax, %ebx
testl %edx, %edx
@@ -1440,13 +1437,13 @@ __bound_local_new:
jne .L173
.L167:
addl $8, %esp
- .cfi_def_cfa_offset 12
popl %ebx
.cfi_restore 3
- .cfi_def_cfa_offset 8
popl %esi
.cfi_restore 6
- .cfi_def_cfa_offset 4
+ popl %ebp
+ .cfi_restore 5
+ .cfi_def_cfa 4, 4
ret
.cfi_endproc
i.e. now it compiles correctly.
Though I do not have x86_64 to test, my guess is that
__builtin_frame_address(1) should work there too. If not - please revert
only x86_64 part of the patch. Thanks.
Cc: Michael Matz <matz@suse.de>
On i386 and gcc-4.7 I found that libc_malloc was miscompiled - look:
static void *libc_malloc(size_t size)
{
void *ptr;
restore_malloc_hooks(); // __malloc_hook = saved_malloc_hook
ptr = malloc(size);
install_malloc_hooks(); // saved_malloc_hook = __malloc_hook, __malloc_hook = __bound_malloc
return ptr;
}
.type libc_malloc, @function
libc_malloc:
.LFB56:
.cfi_startproc
pushl %edx
.cfi_def_cfa_offset 8
movl %eax, (%esp)
call malloc
movl $__bound_malloc, __malloc_hook
movl $__bound_free, __free_hook
movl $__bound_realloc, __realloc_hook
movl $__bound_memalign, __memalign_hook
popl %ecx
.cfi_def_cfa_offset 4
ret
Here gcc inlined both restore_malloc_hooks() and install_malloc_hooks()
and decided that
saved_malloc_hook -> __malloc_hook -> saved_malloc_hook
stores are not needed and could be ommitted. Only it did not know
__molloc_hook affects malloc()...
So add compiler barrier to both install and restore hooks functions and
be done with it - the code is now ok:
diff --git a/bcheck0.s b/bcheck1.s
index 5f50293..4c02a5f 100644
--- a/bcheck0.s
+++ b/bcheck1.s
@@ -42,8 +42,24 @@ libc_malloc:
.cfi_startproc
pushl %edx
.cfi_def_cfa_offset 8
+ movl saved_malloc_hook, %edx
+ movl %edx, __malloc_hook
+ movl saved_free_hook, %edx
+ movl %edx, __free_hook
+ movl saved_realloc_hook, %edx
+ movl %edx, __realloc_hook
+ movl saved_memalign_hook, %edx
+ movl %edx, __memalign_hook
movl %eax, (%esp)
call malloc
+ movl __malloc_hook, %edx
+ movl %edx, saved_malloc_hook
+ movl __free_hook, %edx
+ movl %edx, saved_free_hook
+ movl __realloc_hook, %edx
+ movl %edx, saved_realloc_hook
+ movl __memalign_hook, %edx
+ movl %edx, saved_memalign_hook
movl $__bound_malloc, __malloc_hook
movl $__bound_free, __free_hook
movl $__bound_realloc, __realloc_hook
For barrier I use
__asm__ __volatile__ ("": : : "memory")
which is used as compiler barrier by Linux kernel, and mentioned in gcc
docs and in wikipedia [1].
Without this patch any program compiled with tcc -b crashes in startup
because of infinite recursion in libc_malloc.
[1] http://en.wikipedia.org/wiki/Memory_ordering#Compiler_memory_barrier
Revert commit 891dfcdf3f since it assumes
*all* architectures supported by tcc have GOT offsets aligned on 2. A
rework of this commit is being done since without it all PLT entries
grow by 4 bytes.
Since commit c6630ef92a, Call to a veneer
when the final symbol to be reached is thumb is made through a blx
instruction. This is a mistake since veneers are ARM instructions and
should thus be called with a simple bl. This commit prevent the bl ->
blx conversion when a veneer is used.
Source fortification now works correctly : it compiles without warning
except unused result and the resulting tcc is working fine. Hence let's
stop disabling source fortification and hide unused result instead.
Generate PLT thumb stub for an ARM PLT entry only when at least one
Thumb instruction branches to that entry.
Warning: To save space, this commit reuses the bit 0 of entries of
got_offsets array. The GOT offset is thus saved in a 31 bit value.
Make sure to divide by 2 (right shift by 1) an offset before storing it
there and conversely to multiply the value by 2 (left shift by 1) before
using it.
the absence of a clean target in tests2/Makefile make the clean target
in the main Makefile fails to complete. This commit create such a target
which removes the only file created when tests pass successfully.
Add support for relocations R_ARM_THM_JUMP24 and R_ARM_THM_CALL. These
are encountered with gcc when compiling for armv6 or greater with
-mthumb flag and a call (conditional or not) is done.
Currently, VLA are not forbidden for static variable. This leads to
problems even if for fixed-size array when the size expression uses the
ternary operator (cond ? then-value : else-value) because it is parsed
as a general expression which leads to code generated in this case.
This commit solve the problem by forbidding VLA for static variables.
Although not required for the fix, avoiding code generation when the
expression is constant would be a nice addition though.
Introduce ARM version for the target architecture in order to determine
if blx instruction can be used or not. Availability of blx instruction
allows for more scenarii supported in R_ARM_CALL relocation. It should
also be useful when introducing support for the R_ARM_THM_CALL
relocation.
With R_ARM_CALL, if target function is to be entered in Thumb mode, the
relocation is supposed to transform bl in blx. This is not the case
actually so this commit is there to fix it.
Add support for relocations R_ARM_MOVW_ABS_NC and R_ARM_MOVT_ABS as well
as their Thumb2 counterpart R_ARM_THM_MOVW_ABS_NC and
R_ARM_THM_MOVT_ABS. These are encountered with gcc when compiling for
armv7-a and a data is loaded in a register, either in arm or Thumb2
mode. The first half of the data is loaded with movw ; the second half
is loaded with movt.
We are now compatible with the 0.9,25 version though. A special
value for the second (ptr) argument is used to get the simple
behavior as with the 0.9.24 version.
Arm hardfloat variant uses a different ABI than arm and uses thus a
different multiarch directory for headers and libraries. This commit
detect whether the system uses the hardfloat variant and configure the
multiarch directory accordingly.
The code for shifts is now similar to code for binary arithmetic operations,
except that only the first argument is considered, as required by the ISO C
standard.
The intent is for 'make test' to pass cleanly on each platform, and thus easier
spotting of regressions. Linux is best supported by most tests running and
passing. Mac OSX passes mosts tests that do not make/link with binary files,
due to lack of mach-o file support.
!!! I have very limited knowledge of Windows platform, and cannot comment why
all tests(1) fail. I have posted to newsgroup asking for someone to test
Windows platform.
On 2012-06-26 15:07:57 +0200, Vincent Lefevre wrote:
> ISO C99 TC3 says: [6.5.7#3] "The integer promotions are performed on
> each of the operands. The type of the result is that of the promoted
> left operand."
I've written a patch (attached). Now the shift problems no longer
occur with the testcase and with GNU MPFR's "make check".
--
Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
The tests are taken almost verbatim from the open source project PicoC. It can
be found at https://code.google.com/p/picoc/.
The tests range from very simple/trivial ones to more complicated. My view is
that the more tests the better. Without tests like this I was very reluctant to
make any changes to tcc for the fear of breaking things.
The tests pass on Win32, OSX, Linux x86 and x86_64. One or two tests fail on
each platform due to differences in the runtime library.
