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TLS (GNU/C11 thread-local storage) support for static-linked programs

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the design for TLS in dynamic-linked programs is mostly complete too,
but I have not yet implemented it. cost is nonzero but still low for
programs which do not use TLS and/or do not use threads (a few hundred
bytes of new code, plus dependency on memcpy). i believe it can be
made smaller at some point by merging __init_tls and __init_security
into __libc_start_main and avoiding duplicate auxv-parsing code.

at the same time, I've also slightly changed the logic pthread_create
uses to allocate guard pages to ensure that guard pages are not
counted towards commit charge.
This commit is contained in:
Rich Felker
2012-10-04 16:35:46 -04:00
parent adefe830dd
commit 8431d7972f
6 changed files with 117 additions and 14 deletions
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src/thread/pthread_create.c
+18 -5
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@@ -84,6 +84,8 @@ static void init_file_lock(FILE *f)
if (f && f->lock<0) f->lock = 0;
}
void *__copy_tls(unsigned char *, size_t);
int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr, void *(*entry)(void *), void *restrict arg)
{
int ret;
@@ -92,6 +94,8 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
struct pthread *self = pthread_self(), *new;
unsigned char *map, *stack, *tsd;
unsigned flags = 0x7d8f00;
size_t tls_cnt = libc.tls_cnt;
size_t tls_size = libc.tls_size;
if (!self) return ENOSYS;
if (!libc.threaded) {
@@ -109,15 +113,24 @@ int pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict attr,
} else {
if (attr) {
guard = ROUND(attr->_a_guardsize + DEFAULT_GUARD_SIZE);
size = guard + ROUND(attr->_a_stacksize + DEFAULT_STACK_SIZE);
size = guard + ROUND(attr->_a_stacksize
+ DEFAULT_STACK_SIZE + tls_size);
}
size += __pthread_tsd_size;
map = mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
if (map == MAP_FAILED) return EAGAIN;
if (guard) mprotect(map, guard, PROT_NONE);
if (guard) {
map = mmap(0, size, PROT_NONE, MAP_PRIVATE|MAP_ANON, -1, 0);
if (map == MAP_FAILED) return EAGAIN;
if (mprotect(map+guard, size-guard, PROT_READ|PROT_WRITE)) {
munmap(map, size);
return EAGAIN;
}
} else {
map = mmap(0, size, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANON, -1, 0);
if (map == MAP_FAILED) return EAGAIN;
}
tsd = map + size - __pthread_tsd_size;
}
new = (void *)(tsd - sizeof *new - PAGE_SIZE%sizeof *new);
new = __copy_tls(tsd - tls_size, tls_cnt);
new->map_base = map;
new->map_size = size;
new->pid = self->pid;