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Fix thread-local storage bugs on aarch64

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This change fixes an issue where .tbss memory might not be initialized.
This commit is contained in:
Justine Tunney 2024-05-08 04:03:51 -07:00
parent 793393a341
commit ae2a7ac844
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GPG key ID: BE714B4575D6E328
6 changed files with 93 additions and 65 deletions
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66
libc/runtime/enable_tls.c
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@ -112,10 +112,6 @@ static unsigned long ParseMask(const char *str) {
* and your `errno` variable also won't be thread safe anymore.
*/
textstartup void __enable_tls(void) {
int tid;
size_t siz;
char *mem, *tls;
struct CosmoTib *tib;
// Here's the layout we're currently using:
//
@ -138,7 +134,8 @@ textstartup void __enable_tls(void) {
#ifdef __x86_64__
siz = ROUNDUP(I(_tls_size) + sizeof(*tib), TLS_ALIGNMENT);
char *mem;
size_t siz = ROUNDUP(I(_tls_size) + sizeof(struct CosmoTib), TLS_ALIGNMENT);
if (siz <= sizeof(__static_tls)) {
// if tls requirement is small then use the static tls block
// which helps avoid a system call for appes with little tls
@ -158,28 +155,44 @@ textstartup void __enable_tls(void) {
kAsanProtected);
}
tib = (struct CosmoTib *)(mem + siz - sizeof(*tib));
tls = mem + siz - sizeof(*tib) - I(_tls_size);
struct CosmoTib *tib = (struct CosmoTib *)(mem + siz - sizeof(*tib));
char *tls = mem + siz - sizeof(*tib) - I(_tls_size);
// copy in initialized data section
if (I(_tdata_size)) {
if (IsAsan()) {
__asan_memcpy(tls, _tdata_start, I(_tdata_size));
} else {
memcpy(tls, _tdata_start, I(_tdata_size));
}
}
#elif defined(__aarch64__)
size_t hiz = ROUNDUP(sizeof(*tib) + 2 * sizeof(void *), I(_tls_align));
siz = hiz + I(_tls_size);
if (siz <= sizeof(__static_tls)) {
uintptr_t size = ROUNDUP(sizeof(struct CosmoTib), I(_tls_align)) + //
ROUNDUP(sizeof(uintptr_t) * 2, I(_tdata_align)) + //
ROUNDUP(I(_tdata_size), I(_tbss_align)) + //
I(_tbss_size);
char *mem;
if (I(_tls_align) <= TLS_ALIGNMENT && size <= sizeof(__static_tls)) {
mem = __static_tls;
} else {
mem = _weaken(_mapanon)(siz);
mem = _weaken(_mapanon)(size);
}
if (IsAsan()) {
// there's a roundup(pagesize) gap between .tdata and .tbss
// poison that empty space
__asan_poison(mem + hiz + I(_tdata_size), I(_tbss_offset) - I(_tdata_size),
kAsanProtected);
}
struct CosmoTib *tib =
(struct CosmoTib *)(mem +
ROUNDUP(sizeof(struct CosmoTib), I(_tls_align)) -
sizeof(struct CosmoTib));
tib = (struct CosmoTib *)mem;
tls = mem + hiz;
uintptr_t *dtv = (uintptr_t *)(tib + 1);
size_t dtv_size = sizeof(uintptr_t) * 2;
char *tdata = (char *)dtv + ROUNDUP(dtv_size, I(_tdata_align));
if (I(_tdata_size)) {
memmove(tdata, _tdata_start, I(_tdata_size));
}
// Set the DTV.
//
@ -189,8 +202,8 @@ textstartup void __enable_tls(void) {
//
// @see musl/src/env/__init_tls.c
// @see https://chao-tic.github.io/blog/2018/12/25/tls
((uintptr_t *)tls)[-2] = 1;
((void **)tls)[-1] = tls;
dtv[0] = 1;
dtv[1] = (uintptr_t)tdata;
#else
#error "unsupported architecture"
@ -213,6 +226,8 @@ textstartup void __enable_tls(void) {
} else if (IsXnuSilicon()) {
tib->tib_syshand = __syslib->__pthread_self();
}
int tid;
if (IsLinux() || IsXnuSilicon()) {
// gnu/systemd guarantees pid==tid for the main thread so we can
// avoid issuing a superfluous system call at startup in program
@ -237,15 +252,6 @@ textstartup void __enable_tls(void) {
_pthread_list = &_pthread_static.list;
atomic_store_explicit(&_pthread_static.ptid, tid, memory_order_relaxed);
// copy in initialized data section
if (I(_tdata_size)) {
if (IsAsan()) {
__asan_memcpy(tls, _tdata_start, I(_tdata_size));
} else {
memcpy(tls, _tdata_start, I(_tdata_size));
}
}
// ask the operating system to change the x86 segment register
__set_tls(tib);