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Fix boundschecking for signal/sigaction/fork

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The BOUNDS_CHECKING_ON/BOUNDS_CHECKING_OFF is not working for
signal/sigaction/fork. The reason is that the code stops bound checking
for the whole application. This result in wrong handling of
__bound_local_new/__bound_local_delete and malloc/calloc/realloc/free.
Consider the following code:

void tst(int n) {
  int i, arr[n];
  for (i = 0; i < n; i++) arr[i] = 0;
}

void *some_thread(void *dummy) {
  while (running) { tst(10); tst(20); }
}

void signal_handler(int sig) { ... }

When the signal handler is called the some_thread code can be interrupted when
is just registered the arr[10] data. When the signal handler is leaved the
arr[10] is still registered and did not see the call to deregister arr[10] and
then register arr[20]. The code resumes when tst(20) is running. This results
in a bound checking error when i >= 10.

To solve the above problem I changed the bound checking code to use
tls (thread local storage) for the no_checking variable.
This also makes it now possible to redirect signal/sigaction/fork code
through the bound checking library and disable checking when a signal is
running and to correct the bounds_sem for the fork child process.
The BOUNDS_CHECKING_ON/BOUNDS_CHECKING_OFF is not needed any more for
signal/sigaction/fork. In fact I could remove them from all my applications.

The use of the tls function code slows down the code by about 10%.
So if the slowdown due to bound checking was 5. It is now 5.5 times slower.

For x86_64/i386 I also allowed to use __thread variable in bcheck.c when
compiled with gcc with:
make x86_64-libtcc1-usegcc=yes
make i386-libtcc1-usegcc=yes
This makes code run faster due to use of gcc and __thread variable.
With the __thread variable there is no 10% slowdown.
For other targets this does not work because stabs is not supported.

Changes:

lib/bcheck.c:
- Add TRY_SEM
- Add HAVE_SIGNAL/HAVE_SIGACTION/HAVE_FORK/HAVE_TLS_FUNC/HAVE_TLS_VAR
  - HAVE_SIGNAL: redirect signal() call if set.
  - HAVE_SIGACTION: redirect sigaction() call if set.
  - HAVE_FORK: redirect fork() call if set.
  - HAVE_TLS_FUNC: If target has tls function calls.
  - HAVE_TLS_VAR: If target has __thread tls support.
- Replace all no_checking refecrences to NO_CHECKING_SET/NO_CHECKING_GET macros

tcc-doc.texi:
- Remove examples for signal/sigaction/fork code.
- Add some explanation for signal/sigaction/fork code.
- Add documentaion for __bounds_checking().

tccelf.c:
- Add support for SHF_TLS

tests/tests2/114_bound_signal.c:
- Remove BOUNDS_CHECKING_ON/BOUNDS_CHECKING_OFF
- Add code to trigger failure when tls is not working.

x86_64-link.c:
- Add support for R_X86_64_TLSGD/R_X86_64_TLSLD/R_X86_64_DTPOFF32/R_X86_64_TPOFF32

i386-link.c:
- Add support for R_386_TLS_GD/R_386_TLS_LDM/R_386_TLS_LDO_32/R_386_TLS_LE
This commit is contained in:
herman ten brugge 2020-09-08 14:31:58 +02:00
parent 53d815b8a0
commit 853a498f2c
6 changed files with 529 additions and 122 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

75
i386-link.c
View File

@ -37,6 +37,10 @@ int code_reloc (int reloc_type)
case R_386_GOT32X:
case R_386_GLOB_DAT:
case R_386_COPY:
case R_386_TLS_GD:
case R_386_TLS_LDM:
case R_386_TLS_LDO_32:
case R_386_TLS_LE:
return 0;
case R_386_PC16:
@ -78,6 +82,10 @@ int gotplt_entry_type (int reloc_type)
case R_386_GOT32:
case R_386_GOT32X:
case R_386_PLT32:
case R_386_TLS_GD:
case R_386_TLS_LDM:
case R_386_TLS_LDO_32:
case R_386_TLS_LE:
return ALWAYS_GOTPLT_ENTRY;
}
return -1;
@ -228,6 +236,73 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t
(to remove noise of default case). Is this true?
*/
return;
case R_386_TLS_GD:
{
static const unsigned char expect[] = {
/* lea 0(,%ebx,1),%eax */
0x8d, 0x04, 0x1d, 0x00, 0x00, 0x00, 0x00,
/* call __tls_get_addr@PLT */
0xe8, 0xfc, 0xff, 0xff, 0xff };
static const unsigned char replace[] = {
/* mov %gs:0,%eax */
0x65, 0xa1, 0x00, 0x00, 0x00, 0x00,
/* sub 0,%eax */
0x81, 0xe8, 0x00, 0x00, 0x00, 0x00 };
if (memcmp (ptr-3, expect, sizeof(expect)) == 0) {
ElfW(Sym) *sym;
Section *sec;
int32_t x;
memcpy(ptr-3, replace, sizeof(replace));
rel[1].r_info = ELFW(R_INFO)(0, R_386_NONE);
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = sym->st_value - sec->sh_addr - sec->data_offset;
add32le(ptr + 5, -x);
}
else
tcc_error("unexpected R_386_TLS_GD pattern");
}
return;
case R_386_TLS_LDM:
{
static const unsigned char expect[] = {
/* lea 0(%ebx),%eax */
0x8d, 0x83, 0x00, 0x00, 0x00, 0x00,
/* call __tls_get_addr@PLT */
0xe8, 0xfc, 0xff, 0xff, 0xff };
static const unsigned char replace[] = {
/* mov %gs:0,%eax */
0x65, 0xa1, 0x00, 0x00, 0x00, 0x00,
/* nop */
0x90,
/* lea 0(%esi,%eiz,1),%esi */
0x8d, 0x74, 0x26, 0x00 };
if (memcmp (ptr-2, expect, sizeof(expect)) == 0) {
memcpy(ptr-2, replace, sizeof(replace));
rel[1].r_info = ELFW(R_INFO)(0, R_386_NONE);
}
else
tcc_error("unexpected R_386_TLS_LDM pattern");
}
return;
case R_386_TLS_LDO_32:
case R_386_TLS_LE:
{
ElfW(Sym) *sym;
Section *sec;
int32_t x;
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = val - sec->sh_addr - sec->data_offset;
add32le(ptr, x);
}
return;
case R_386_NONE:
return;
default:
fprintf(stderr,"FIXME: handle reloc type %d at %x [%p] to %x\n",
type, (unsigned)addr, ptr, (unsigned)val);

406
lib/bcheck.c
View File

@ -69,25 +69,38 @@
#define EXIT_SEM()
#define WAIT_SEM()
#define POST_SEM()
#define TRY_SEM()
#define HAVE_MEMALIGN (0)
#define MALLOC_REDIR (0)
#define HAVE_PTHREAD_CREATE (0)
#define HAVE_CTYPE (0)
#define HAVE_ERRNO (0)
#define HAVE_SIGNAL (0)
#define HAVE_SIGACTION (0)
#define HAVE_FORK (0)
#define HAVE_TLS_FUNC (0)
#define HAVE_TLS_VAR (0)
#elif defined(_WIN32)
#include <windows.h>
#include <signal.h>
static CRITICAL_SECTION bounds_sem;
#define INIT_SEM() InitializeCriticalSection(&bounds_sem)
#define EXIT_SEM() DeleteCriticalSection(&bounds_sem)
#define WAIT_SEM() EnterCriticalSection(&bounds_sem)
#define POST_SEM() LeaveCriticalSection(&bounds_sem)
#define TRY_SEM() TryEnterCriticalSection(&bounds_sem)
#define HAVE_MEMALIGN (0)
#define MALLOC_REDIR (0)
#define HAVE_PTHREAD_CREATE (0)
#define HAVE_CTYPE (0)
#define HAVE_ERRNO (0)
#define HAVE_SIGNAL (1)
#define HAVE_SIGACTION (0)
#define HAVE_FORK (0)
#define HAVE_TLS_FUNC (1)
#define HAVE_TLS_VAR (0)
#else
@ -97,6 +110,7 @@ static CRITICAL_SECTION bounds_sem;
#include <pthread.h>
#include <dlfcn.h>
#include <errno.h>
#include <signal.h>
#ifdef __APPLE__
#include <dispatch/dispatch.h>
static dispatch_semaphore_t bounds_sem;
@ -104,6 +118,7 @@ static dispatch_semaphore_t bounds_sem;
#define EXIT_SEM() dispatch_release(*(dispatch_object_t*)&bounds_sem)
#define WAIT_SEM() if (use_sem) dispatch_semaphore_wait(bounds_sem, DISPATCH_TIME_FOREVER)
#define POST_SEM() if (use_sem) dispatch_semaphore_signal(bounds_sem)
#define TRY_SEM() if (use_sem) dispatch_semaphore_wait(bounds_sem, DISPATCH_TIME_NOW)
#elif 0
#include <semaphore.h>
static sem_t bounds_sem;
@ -112,12 +127,15 @@ static sem_t bounds_sem;
#define WAIT_SEM() if (use_sem) while (sem_wait (&bounds_sem) < 0 \
&& errno == EINTR)
#define POST_SEM() if (use_sem) sem_post (&bounds_sem)
#define TRY_SEM() if (use_sem) while (sem_trywait (&bounds_sem) < 0 \
&& errno == EINTR)
#elif 0
static pthread_mutex_t bounds_mtx;
#define INIT_SEM() pthread_mutex_init (&bounds_mtx, NULL)
#define EXIT_SEM() pthread_mutex_destroy (&bounds_mtx)
#define WAIT_SEM() if (use_sem) pthread_mutex_lock (&bounds_mtx)
#define POST_SEM() if (use_sem) pthread_mutex_unlock (&bounds_mtx)
#define TRY_SEM() if (use_sem) pthread_mutex_trylock (&bounds_mtx)
#else
static pthread_spinlock_t bounds_spin;
/* about 25% faster then semaphore. */
@ -125,25 +143,52 @@ static pthread_spinlock_t bounds_spin;
#define EXIT_SEM() pthread_spin_destroy (&bounds_spin)
#define WAIT_SEM() if (use_sem) pthread_spin_lock (&bounds_spin)
#define POST_SEM() if (use_sem) pthread_spin_unlock (&bounds_spin)
#define TRY_SEM() if (use_sem) pthread_spin_trylock (&bounds_spin)
#endif
#define HAVE_MEMALIGN (1)
#define MALLOC_REDIR (1)
#define HAVE_PTHREAD_CREATE (1)
#define HAVE_CTYPE (1)
#define HAVE_ERRNO (1)
#define HAVE_SIGNAL (1)
#define HAVE_SIGACTION (1)
#define HAVE_FORK (1)
#if !defined(__APPLE__) && defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
#define HAVE_TLS_FUNC (0)
#define HAVE_TLS_VAR (1)
#else
#define HAVE_TLS_FUNC (1)
#define HAVE_TLS_VAR (0)
#endif
#endif
#if MALLOC_REDIR
static void *(*malloc_redir) (size_t);
static void *(*calloc_redir) (size_t, size_t);
static void (*free_redir) (void *);
static void *(*realloc_redir) (void *, size_t);
static void *(*memalign_redir) (size_t, size_t);
static int (*pthread_create_redir) (pthread_t *thread,
const pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg);
static unsigned int pool_index;
static unsigned char __attribute__((aligned(16))) initial_pool[256];
static unsigned char use_sem;
#endif
#if HAVE_MEMALIGN
static void *(*memalign_redir) (size_t, size_t);
#endif
#if HAVE_PTHREAD_CREATE
static int (*pthread_create_redir) (pthread_t *thread,
const pthread_attr_t *attr,
void *(*start_routine)(void *), void *arg);
#endif
#if HAVE_SIGNAL
typedef void (*bound_sig)(int);
static bound_sig (*signal_redir) (int signum, bound_sig handler);
#endif
#if HAVE_SIGACTION
static int (*sigaction_redir) (int signum, const struct sigaction *act,
struct sigaction *oldact);
#endif
#if HAVE_FORK
static int (*fork_redir) (void);
#endif
#define TCC_TYPE_NONE (0)
@ -285,7 +330,51 @@ static unsigned char print_heap;
static unsigned char print_statistic;
static unsigned char no_strdup;
static int never_fatal;
static int no_checking = 1;
#if HAVE_TLS_FUNC
#if defined(_WIN32)
static int no_checking = 0;
static DWORD no_checking_key;
#define NO_CHECKING_CHECK() if (!p) { \
p = (int *) LocalAlloc(LPTR, sizeof(int)); \
if (!p) bound_alloc_error("tls malloc"); \
*p = 0; \
TlsSetValue(no_checking_key, p); \
}
#define NO_CHECKING_GET() ({ int *p = TlsGetValue(no_checking_key); \
NO_CHECKING_CHECK(); \
*p; \
})
#define NO_CHECKING_SET(v) { int *p = TlsGetValue(no_checking_key); \
NO_CHECKING_CHECK(); \
*p = v; \
}
#else
static int no_checking = 0;
static pthread_key_t no_checking_key;
#define NO_CHECKING_CHECK() if (!p) { \
p = (int *) BOUND_MALLOC(sizeof(int)); \
if (!p) bound_alloc_error("tls malloc"); \
*p = 0; \
pthread_setspecific(no_checking_key, p); \
}
#define NO_CHECKING_GET() ({ int *p = pthread_getspecific(no_checking_key); \
NO_CHECKING_CHECK(); \
*p; \
})
#define NO_CHECKING_SET(v) { int *p = pthread_getspecific(no_checking_key); \
NO_CHECKING_CHECK(); \
*p = v; \
}
#endif
#elif HAVE_TLS_VAR
static __thread int no_checking = 0;
#define NO_CHECKING_GET() no_checking
#define NO_CHECKING_SET(v) no_checking = v
#else
static int no_checking = 0;
#define NO_CHECKING_GET() no_checking
#define NO_CHECKING_SET(v) no_checking = v
#endif
static char exec[100];
#if BOUND_STATISTIC
@ -335,41 +424,6 @@ static unsigned long long bound_splay_delete;
#define INCR_COUNT_SPLAY(x)
#endif
/* currently only i386/x86_64 supported. Change for other platforms */
static void fetch_and_add(int* variable, int value)
{
#if defined __i386__ || defined __x86_64__
__asm__ volatile("lock; addl %0, %1"
: "+r" (value), "+m" (*variable) // input+output
: // No input-only
: "memory"
);
#elif defined __arm__
extern void fetch_and_add_arm(int* variable, int value);
fetch_and_add_arm(variable, value);
#elif defined __aarch64__
extern void fetch_and_add_arm64(int* variable, int value);
fetch_and_add_arm64(variable, value);
#elif defined __riscv
extern void fetch_and_add_riscv64(int* variable, int value);
fetch_and_add_riscv64(variable, value);
#else
*variable += value;
#endif
}
/* enable/disable checking. This can be used in signal handlers. */
void __bounds_checking (int no_check)
{
fetch_and_add (&no_checking, no_check);
}
/* enable/disable checking. This can be used in signal handlers. */
void __bound_never_fatal (int neverfatal)
{
fetch_and_add (&never_fatal, neverfatal);
}
int tcc_backtrace(const char *fmt, ...);
/* print a bound error message */
@ -395,13 +449,51 @@ static void bound_not_found_warning(const char *file, const char *function,
dprintf(stderr, "%s%s, %s(): Not found %p\n", exec, file, function, ptr);
}
static void fetch_and_add(int* variable, int value)
{
#if defined __i386__ || defined __x86_64__
__asm__ volatile("lock; addl %0, %1"
: "+r" (value), "+m" (*variable) // input+output
: // No input-only
: "memory"
);
#elif defined __arm__
extern void fetch_and_add_arm(int* variable, int value);
fetch_and_add_arm(variable, value);
#elif defined __aarch64__
extern void fetch_and_add_arm64(int* variable, int value);
fetch_and_add_arm64(variable, value);
#elif defined __riscv
extern void fetch_and_add_riscv64(int* variable, int value);
fetch_and_add_riscv64(variable, value);
#else
*variable += value;
#endif
}
/* enable/disable checking. This can be used in signal handlers. */
void __bounds_checking (int no_check)
{
#if HAVE_TLS_FUNC || HAVE_TLS_VAR
NO_CHECKING_SET(NO_CHECKING_GET() + no_check);
#else
fetch_and_add (&no_checking, no_check);
#endif
}
/* enable/disable checking. This can be used in signal handlers. */
void __bound_never_fatal (int neverfatal)
{
fetch_and_add (&never_fatal, neverfatal);
}
/* return '(p + offset)' for pointer arithmetic (a pointer can reach
the end of a region in this case */
void * __bound_ptr_add(void *p, size_t offset)
{
size_t addr = (size_t)p;
if (no_checking)
if (NO_CHECKING_GET())
return p + offset;
dprintf(stderr, "%s, %s(): %p 0x%lx\n",
@ -449,7 +541,7 @@ void * __bound_ptr_indir ## dsize (void *p, size_t offset) \
{ \
size_t addr = (size_t)p; \
\
if (no_checking) \
if (NO_CHECKING_GET()) \
return p + offset; \
\
dprintf(stderr, "%s, %s(): %p 0x%lx\n", \
@ -515,7 +607,7 @@ void FASTCALL __bound_local_new(void *p1)
{
size_t addr, fp, *p = p1;
if (no_checking)
if (NO_CHECKING_GET())
return;
GET_CALLER_FP(fp);
dprintf(stderr, "%s, %s(): p1=%p fp=%p\n",
@ -545,7 +637,7 @@ void FASTCALL __bound_local_delete(void *p1)
{
size_t addr, fp, *p = p1;
if (no_checking)
if (NO_CHECKING_GET())
return;
GET_CALLER_FP(fp);
dprintf(stderr, "%s, %s(): p1=%p fp=%p\n",
@ -624,7 +716,7 @@ void __bound_new_region(void *p, size_t size)
alloca_list_type *cur;
alloca_list_type *new;
if (no_checking)
if (NO_CHECKING_GET())
return;
dprintf(stderr, "%s, %s(): %p, 0x%lx\n",
@ -667,7 +759,7 @@ void __bound_setjmp(jmp_buf env)
jmp_list_type *jl;
void *e = (void *) env;
if (no_checking == 0) {
if (NO_CHECKING_GET() == 0) {
dprintf(stderr, "%s, %s(): %p\n", __FILE__, __FUNCTION__, e);
WAIT_SEM ();
INCR_COUNT(bound_setjmp_count);
@ -703,7 +795,7 @@ static void __bound_long_jump(jmp_buf env, int val, int sig, const char *func)
void *e;
BOUND_TID_TYPE tid;
if (no_checking == 0) {
if (NO_CHECKING_GET() == 0) {
e = (void *)env;
tid = BOUND_GET_TID;
dprintf(stderr, "%s, %s(): %p\n", __FILE__, func, e);
@ -804,6 +896,17 @@ void __bound_init(size_t *p, int mode)
}
inited = 1;
#if HAVE_TLS_FUNC
#if defined(_WIN32)
no_checking_key = TlsAlloc();
TlsSetValue(no_checking_key, &no_checking);
#else
pthread_key_create(&no_checking_key, NULL);
pthread_setspecific(no_checking_key, &no_checking);
#endif
#endif
NO_CHECKING_SET(1);
print_warn_ptr_add = getenv ("TCC_BOUNDS_WARN_POINTER_ADD") != NULL;
print_calls = getenv ("TCC_BOUNDS_PRINT_CALLS") != NULL;
print_heap = getenv ("TCC_BOUNDS_PRINT_HEAP") != NULL;
@ -845,6 +948,29 @@ void __bound_init(size_t *p, int mode)
*(void **) (&pthread_create_redir) = dlsym (addr, "pthread_create");
dprintf(stderr, "%s, %s(): pthread_create_redir %p\n",
__FILE__, __FUNCTION__, pthread_create_redir);
if (pthread_create_redir == NULL)
bound_alloc_error ("Cannot redirect pthread_create");
#endif
#if HAVE_SIGNAL
*(void **) (&signal_redir) = dlsym (addr, "signal");
dprintf(stderr, "%s, %s(): signal_redir %p\n",
__FILE__, __FUNCTION__, signal_redir);
if (signal_redir == NULL)
bound_alloc_error ("Cannot redirect signal");
#endif
#if HAVE_SIGACTION
*(void **) (&sigaction_redir) = dlsym (addr, "sigaction");
dprintf(stderr, "%s, %s(): sigaction_redir %p\n",
__FILE__, __FUNCTION__, sigaction_redir);
if (sigaction_redir == NULL)
bound_alloc_error ("Cannot sigaction signal");
#endif
#if HAVE_FORK
*(void **) (&fork_redir) = dlsym (addr, "fork");
dprintf(stderr, "%s, %s(): fork_redir %p\n",
__FILE__, __FUNCTION__, fork_redir);
if (fork_redir == NULL)
bound_alloc_error ("Cannot sigaction fork");
#endif
}
#endif
@ -936,7 +1062,7 @@ add_bounds:
no_bounds:
POST_SEM ();
no_checking = 0;
NO_CHECKING_SET(0);
dprintf(stderr, "%s, %s(): end\n\n", __FILE__, __FUNCTION__);
}
@ -961,8 +1087,9 @@ __bound_main_arg(int argc, char **argv, char **envp)
dprintf(stderr, "%s, %s(): arg %p 0x%lx\n",
__FILE__, __FUNCTION__,
argv[i], (unsigned long)(strlen (argv[i]) + 1));
dprintf(stderr, "%s, %s(): argv %p 0x%lx\n",
__FILE__, __FUNCTION__, argv, (argc + 1) * sizeof(char *));
dprintf(stderr, "%s, %s(): argv %p %d\n",
__FILE__, __FUNCTION__, argv,
(int)((argc + 1) * sizeof(char *)));
}
#endif
}
@ -986,8 +1113,9 @@ __bound_main_arg(int argc, char **argv, char **envp)
*p, (unsigned long)(strlen (*p) + 1));
++p;
}
dprintf(stderr, "%s, %s(): environ %p 0x%lx\n",
__FILE__, __FUNCTION__, envp, (++p - envp) * sizeof(char *));
dprintf(stderr, "%s, %s(): environ %p %d\n",
__FILE__, __FUNCTION__, envp,
(int)((++p - envp) * sizeof(char *)));
}
#endif
}
@ -1010,9 +1138,9 @@ void __attribute__((destructor)) __bound_exit(void)
}
#endif
no_checking = 1;
NO_CHECKING_SET(1);
WAIT_SEM ();
TRY_SEM ();
while (alloca_list) {
alloca_list_type *next = alloca_list->next;
@ -1048,6 +1176,13 @@ void __attribute__((destructor)) __bound_exit(void)
#endif
POST_SEM ();
EXIT_SEM ();
#if HAVE_TLS_FUNC
#if defined(_WIN32)
TlsFree(no_checking_key);
#else
pthread_key_delete(no_checking_key);
#endif
#endif
inited = 0;
if (print_statistic) {
#if BOUND_STATISTIC
@ -1095,12 +1230,155 @@ void __attribute__((destructor)) __bound_exit(void)
}
#if HAVE_PTHREAD_CREATE
#if HAVE_TLS_FUNC
typedef struct {
void *(*start_routine) (void *);
void *arg;
} bound_thread_create_type;
static void *bound_thread_create(void *bdata)
{
bound_thread_create_type *data = (bound_thread_create_type *) bdata;
void *retval;
int *p = (int *) BOUND_MALLOC(sizeof(int));
if (!p) bound_alloc_error("bound_thread_create malloc");
*p = 0;
pthread_setspecific(no_checking_key, p);
retval = data->start_routine(data->arg);
pthread_setspecific(no_checking_key, NULL);
BOUND_FREE (p);
BOUND_FREE (data);
return retval;
}
#endif
int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
void *(*start_routine) (void *), void *arg)
{
use_sem = 1;
dprintf (stderr, "%s, %s()\n", __FILE__, __FUNCTION__);
#if HAVE_TLS_FUNC
{
bound_thread_create_type *data;
data = (bound_thread_create_type *) BOUND_MALLOC(sizeof(bound_thread_create_type));
data->start_routine = start_routine;
data->arg = arg;
return pthread_create_redir(thread, attr, bound_thread_create, data);
}
#else
return pthread_create_redir(thread, attr, start_routine, arg);
#endif
}
#endif
#if HAVE_SIGNAL || HAVE_SIGACTION
typedef union {
#if HAVE_SIGNAL
bound_sig signal_handler;
#endif
#if HAVE_SIGACTION
void (*sig_handler)(int);
void (*sig_sigaction)(int, siginfo_t *, void *);
#endif
} bound_sig_type;
static unsigned char bound_sig_used[NSIG];
static bound_sig_type bound_sig_data[NSIG];
#endif
#if HAVE_SIGNAL
static void signal_handler(int sig)
{
__bounds_checking(1);
bound_sig_data[sig].signal_handler(sig);
__bounds_checking(-1);
}
bound_sig signal(int signum, bound_sig handler)
{
bound_sig retval;
dprintf (stderr, "%s, %s() %d %p\n", __FILE__, __FUNCTION__,
signum, handler);
retval = signal_redir(signum, handler ? signal_handler : handler);
if (retval != SIG_ERR) {
if (bound_sig_used[signum])
retval = bound_sig_data[signum].signal_handler;
if (handler) {
bound_sig_used[signum] = 1;
bound_sig_data[signum].signal_handler = handler;
}
}
return retval;
}
#endif
#if HAVE_SIGACTION
static void sig_handler(int sig)
{
__bounds_checking(1);
bound_sig_data[sig].sig_handler(sig);
__bounds_checking(-1);
}
static void sig_sigaction(int sig, siginfo_t *info, void *ucontext)
{
__bounds_checking(1);
bound_sig_data[sig].sig_sigaction(sig, info, ucontext);
__bounds_checking(-1);
}
int sigaction(int signum, const struct sigaction *act, struct sigaction *oldact)
{
int retval;
struct sigaction nact, oact;
dprintf (stderr, "%s, %s() %d %p %p\n", __FILE__, __FUNCTION__,
signum, act, oldact);
if (act) {
nact = *act;
if (nact.sa_flags & SA_SIGINFO)
nact.sa_sigaction = sig_sigaction;
else
nact.sa_handler = sig_handler;
retval = sigaction_redir(signum, &nact, &oact);
}
else
retval = sigaction_redir(signum, act, &oact);
if (retval >= 0) {
if (bound_sig_used[signum]) {
if (oact.sa_flags & SA_SIGINFO)
oact.sa_sigaction = bound_sig_data[signum].sig_sigaction;
else
oact.sa_handler = bound_sig_data[signum].sig_handler;
}
if (oldact) {
*oldact = oact;
}
if (act) {
bound_sig_used[signum] = 1;
if (act->sa_flags & SA_SIGINFO)
bound_sig_data[signum].sig_sigaction = act->sa_sigaction;
else
bound_sig_data[signum].sig_handler = act->sa_handler;
}
}
return retval;
}
#endif
#if HAVE_FORK
pid_t fork(void)
{
pid_t retval = (*fork_redir)();
if (retval == 0) {
TRY_SEM();
POST_SEM();
}
return retval;
}
#endif
@ -1134,7 +1412,7 @@ void *__bound_malloc(size_t size, const void *caller)
dprintf(stderr, "%s, %s(): %p, 0x%lx\n",
__FILE__, __FUNCTION__, ptr, (unsigned long)size);
if (no_checking == 0) {
if (NO_CHECKING_GET() == 0) {
WAIT_SEM ();
INCR_COUNT(bound_malloc_count);
@ -1173,7 +1451,7 @@ void *__bound_memalign(size_t size, size_t align, const void *caller)
dprintf(stderr, "%s, %s(): %p, 0x%lx\n",
__FILE__, __FUNCTION__, ptr, (unsigned long)size);
if (no_checking == 0) {
if (NO_CHECKING_GET() == 0) {
WAIT_SEM ();
INCR_COUNT(bound_memalign_count);
@ -1206,7 +1484,7 @@ void __bound_free(void *ptr, const void *caller)
dprintf(stderr, "%s, %s(): %p\n", __FILE__, __FUNCTION__, ptr);
if (no_checking == 0) {
if (NO_CHECKING_GET() == 0) {
WAIT_SEM ();
INCR_COUNT(bound_free_count);
tree = splay (addr, tree);
@ -1251,7 +1529,7 @@ void *__bound_realloc(void *ptr, size_t size, const void *caller)
dprintf(stderr, "%s, %s(): %p, 0x%lx\n",
__FILE__, __FUNCTION__, new_ptr, (unsigned long)size);
if (no_checking == 0) {
if (NO_CHECKING_GET() == 0) {
WAIT_SEM ();
INCR_COUNT(bound_realloc_count);
@ -1298,7 +1576,7 @@ void *__bound_calloc(size_t nmemb, size_t size)
if (ptr) {
memset (ptr, 0, size);
if (no_checking == 0) {
if (NO_CHECKING_GET() == 0) {
WAIT_SEM ();
INCR_COUNT(bound_calloc_count);
tree = splay_insert ((size_t) ptr, size ? size : size + 1, tree);
@ -1319,7 +1597,7 @@ void *__bound_mmap (void *start, size_t size, int prot,
dprintf(stderr, "%s, %s(): %p, 0x%lx\n",
__FILE__, __FUNCTION__, start, (unsigned long)size);
result = mmap (start, size, prot, flags, fd, offset);
if (result && no_checking == 0) {
if (result && NO_CHECKING_GET() == 0) {
WAIT_SEM ();
INCR_COUNT(bound_mmap_count);
tree = splay_insert((size_t)result, size, tree);
@ -1334,7 +1612,7 @@ int __bound_munmap (void *start, size_t size)
dprintf(stderr, "%s, %s(): %p, 0x%lx\n",
__FILE__, __FUNCTION__, start, (unsigned long)size);
if (start && no_checking == 0) {
if (start && NO_CHECKING_GET() == 0) {
WAIT_SEM ();
INCR_COUNT(bound_munmap_count);
tree = splay_delete ((size_t) start, tree);
@ -1363,7 +1641,7 @@ static int check_overlap (const void *p1, size_t n1,
const void *p1e = (const void *) ((const char *) p1 + n1);
const void *p2e = (const void *) ((const char *) p2 + n2);
if (no_checking == 0 && n1 != 0 && n2 !=0 &&
if (NO_CHECKING_GET() == 0 && n1 != 0 && n2 !=0 &&
((p1 <= p2 && p1e > p2) || /* p1----p2====p1e----p2e */
(p2 <= p1 && p2e > p1))) { /* p2----p1====p2e----p1e */
bound_error("overlapping regions %p(0x%lx), %p(0x%lx) in %s",
@ -1613,7 +1891,7 @@ char *__bound_strdup(const char *s)
dprintf(stderr, "%s, %s(): %p, 0x%lx\n",
__FILE__, __FUNCTION__, new, (unsigned long)(p -s));
if (new) {
if (no_checking == 0 && no_strdup == 0) {
if (NO_CHECKING_GET() == 0 && no_strdup == 0) {
WAIT_SEM ();
tree = splay_insert((size_t)new, p - s, tree);
if (tree && tree->start == (size_t) new)

43
tcc-doc.texi
View File

@ -949,13 +949,24 @@ executable should always be compiled with the @option{-b}.
@emph{fully compatible} with unchecked code. When a pointer comes from
unchecked code, it is assumed to be valid. Even very obscure C code with
casts should work correctly.
@item Signal handlers are not compatible with bounds checking. The fork()
function call in a multi threaded application is also a problem.
The code below can be used to solve this.
@item Signal handlers are not compatible with bounds checking. The
bounds checking code disables checking in signal/sigaction handlers.
The fork() function call in a multi threaded application is also a problem.
The bound checking code fixes this for the child process.
@item The reason that signals and fork have problems is that we use locking
inside the bounds checking code.
Inside a signal handler we can not use locks. Also in a multi threaded
application after a fork the child process can have the lock set
by another thread.
@item The BOUNDS_CHECKING_OFF and BOUNDS_CHECKING_ON can also be used to
disable bounds checking for some code.
@item The __bounds_checking call adds a value to a thread local value.
The value starts at 0. If the value is not 0 the code is not checked
for bounds checking errors.
@end itemize
@example
#ifdef __BOUNDS_CHECKING_ON
#if defined(__TINYC__) && __BOUNDS_CHECKING_ON
extern void __bounds_checking (int x);
# define BOUNDS_CHECKING_OFF __bounds_checking(1)
# define BOUNDS_CHECKING_ON __bounds_checking(-1)
@ -963,30 +974,6 @@ extern void __bounds_checking (int x);
# define BOUNDS_CHECKING_OFF
# define BOUNDS_CHECKING_ON
#endif
void signal_handler(int sig, void *info, void *ucontext)
@{
BOUNDS_CHECKING_OFF;
... signal handler code without generated bounds checking code.
BOUNDS_CHECKING_ON;
@}
void run(const char *cmd)
@{
switch (fork()) @{
case 0:
BOUNDS_CHECKING_OFF;
...
exec...
exit(1);
case -1:
...
break;
default:
...
break;
@}
@}
@end example
For more information about the ideas behind this method, see

24
tccelf.c
View File

@ -1876,13 +1876,13 @@ static int layout_sections(TCCState *s1, ElfW(Phdr) *phdr, int phnum,
dyninf->bss_addr = dyninf->bss_size = 0;
#endif
for(j = 0; j < 2; j++) {
ph->p_type = PT_LOAD;
for(j = 0; j < (phnum == 6 ? 3 : 2); j++) {
ph->p_type = j == 2 ? PT_TLS : PT_LOAD;
if (j == 0)
ph->p_flags = PF_R | PF_X;
else
ph->p_flags = PF_R | PF_W;
ph->p_align = s_align;
ph->p_align = j == 2 ? 4 : s_align;
/* Decide the layout of sections loaded in memory. This must
be done before program headers are filled since they contain
@ -1894,13 +1894,17 @@ static int layout_sections(TCCState *s1, ElfW(Phdr) *phdr, int phnum,
s = s1->sections[i];
/* compute if section should be included */
if (j == 0) {
if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE)) !=
if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE | SHF_TLS)) !=
SHF_ALLOC)
continue;
} else {
if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE)) !=
} else if (j == 1) {
if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE | SHF_TLS)) !=
(SHF_ALLOC | SHF_WRITE))
continue;
} else {
if ((s->sh_flags & (SHF_ALLOC | SHF_WRITE | SHF_TLS)) !=
(SHF_ALLOC | SHF_WRITE | SHF_TLS))
continue;
}
if (s == interp) {
if (k != 0)
@ -2511,8 +2515,12 @@ static int elf_output_file(TCCState *s1, const char *filename)
phnum = 3;
else if (s1->static_link)
phnum = 2;
else
phnum = 5;
else {
int i;
for (i = 1; i < s1->nb_sections &&
!(s1->sections[i]->sh_flags & SHF_TLS); i++);
phnum = i < s1->nb_sections ? 6 : 5;
}
/* allocate program segment headers */
phdr = tcc_mallocz(phnum * sizeof(ElfW(Phdr)));

31
tests/tests2/114_bound_signal.c
View File

@ -8,39 +8,27 @@
#include <errno.h>
#include <setjmp.h>
/* See tcc-doc.info */
#if defined(__TINYC__) && __BOUNDS_CHECKING_ON
#undef __attribute__
extern void __bounds_checking (int no_check);
#define BOUNDS_CHECKING_OFF __bounds_checking(1)
#define BOUNDS_CHECKING_ON __bounds_checking(-1)
#else
#define BOUNDS_CHECKING_OFF
#define BOUNDS_CHECKING_ON
#endif
static volatile int run = 1;
static int dummy[10];
static sem_t sem;
static void
add (void)
add (int n)
{
int i;
int arr[n];
BOUNDS_CHECKING_OFF;
for (i = 0; i < (sizeof(dummy)/sizeof(dummy[0])); i++) {
dummy[i]++;
for (i = 0; i < n; i++) {
arr[i]++;
}
memset (&dummy[0], 0, sizeof(dummy));
BOUNDS_CHECKING_ON;
memset (&arr[0], 0, n * sizeof(int));
}
static void *
high_load (void *unused)
{
while (run) {
add();
add(10);
add(20);
}
return NULL;
}
@ -57,10 +45,9 @@ do_signal (void *unused)
static void signal_handler(int sig)
{
BOUNDS_CHECKING_OFF;
add();
add(10);
add(20);
sem_post (&sem);
BOUNDS_CHECKING_ON;
}
int

72
x86_64-link.c
View File

@ -43,6 +43,10 @@ int code_reloc (int reloc_type)
case R_X86_64_COPY:
case R_X86_64_RELATIVE:
case R_X86_64_GOTOFF64:
case R_X86_64_TLSGD:
case R_X86_64_TLSLD:
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
return 0;
case R_X86_64_PC32:
@ -87,6 +91,10 @@ int gotplt_entry_type (int reloc_type)
case R_X86_64_GOTOFF64:
case R_X86_64_GOTPCREL:
case R_X86_64_GOTPCRELX:
case R_X86_64_TLSGD:
case R_X86_64_TLSLD:
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
case R_X86_64_REX_GOTPCRELX:
case R_X86_64_PLT32:
case R_X86_64_PLTOFF64:
@ -281,6 +289,70 @@ void relocate(TCCState *s1, ElfW_Rel *rel, int type, unsigned char *ptr, addr_t
case R_X86_64_GOTOFF64:
add64le(ptr, val - s1->got->sh_addr);
break;
case R_X86_64_TLSGD:
{
static const unsigned char expect[] = {
/* .byte 0x66; lea 0(%rip),%rdi */
0x66, 0x48, 0x8d, 0x3d, 0x00, 0x00, 0x00, 0x00,
/* .word 0x6666; rex64; call __tls_get_addr@PLT */
0x66, 0x66, 0x48, 0xe8, 0x00, 0x00, 0x00, 0x00 };
static const unsigned char replace[] = {
/* mov %fs:0,%rax */
0x64, 0x48, 0x8b, 0x04, 0x25, 0x00, 0x00, 0x00, 0x00,
/* lea -4(%rax),%rax */
0x48, 0x8d, 0x80, 0x00, 0x00, 0x00, 0x00 };
if (memcmp (ptr-4, expect, sizeof(expect)) == 0) {
ElfW(Sym) *sym;
Section *sec;
int32_t x;
memcpy(ptr-4, replace, sizeof(replace));
rel[1].r_info = ELFW(R_INFO)(0, R_X86_64_NONE);
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = sym->st_value - sec->sh_addr - sec->data_offset;
add32le(ptr + 8, x);
}
else
tcc_error("unexpected R_X86_64_TLSGD pattern");
}
break;
case R_X86_64_TLSLD:
{
static const unsigned char expect[] = {
/* lea 0(%rip),%rdi */
0x48, 0x8d, 0x3d, 0x00, 0x00, 0x00, 0x00,
/* call __tls_get_addr@PLT */
0xe8, 0x00, 0x00, 0x00, 0x00 };
static const unsigned char replace[] = {
/* data16 data16 data16 mov %fs:0,%rax */
0x66, 0x66, 0x66, 0x64, 0x48, 0x8b, 0x04, 0x25,
0x00, 0x00, 0x00, 0x00 };
if (memcmp (ptr-3, expect, sizeof(expect)) == 0) {
memcpy(ptr-3, replace, sizeof(replace));
rel[1].r_info = ELFW(R_INFO)(0, R_X86_64_NONE);
}
else
tcc_error("unexpected R_X86_64_TLSLD pattern");
}
break;
case R_X86_64_DTPOFF32:
case R_X86_64_TPOFF32:
{
ElfW(Sym) *sym;
Section *sec;
int32_t x;
sym = &((ElfW(Sym) *)symtab_section->data)[sym_index];
sec = s1->sections[sym->st_shndx];
x = val - sec->sh_addr - sec->data_offset;
add32le(ptr, x);
}
break;
case R_X86_64_NONE:
break;
case R_X86_64_RELATIVE:
#ifdef TCC_TARGET_PE
add32le(ptr, val - s1->pe_imagebase);