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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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77
libc/thread/mktls.c
View file

@ -25,6 +25,7 @@
#include "libc/mem/mem.h"
#include "libc/runtime/internal.h"
#include "libc/runtime/runtime.h"
#include "libc/stdio/sysparam.h"
#include "libc/str/locale.h"
#include "libc/str/str.h"
#include "libc/thread/tls.h"
@ -54,6 +55,19 @@ static char *_mktls_below(struct CosmoTib **out_tib) {
char *mem, *tls;
struct CosmoTib *tib;
// Here's the TLS memory layout on x86_64
//
// __get_tls()
// │
// %fs OpenBSD/NetBSD
// _Thread_local │
// ┌───┬──────────┬──────────┼───┐
// │pad│ .tdata │ .tbss │tib│
// └───┴──────────┴──────────┼───┘
// │
// Linux/FreeBSD/Windows/Mac %gs
//
siz = ROUNDUP(I(_tls_size) + sizeof(*tib), _Alignof(struct CosmoTib));
siz = ROUNDUP(siz, _Alignof(struct CosmoTib));
mem = memalign(_Alignof(struct CosmoTib), siz);
@ -77,53 +91,58 @@ static char *_mktls_below(struct CosmoTib **out_tib) {
}
// clear .tbss
bzero(tls + I(_tbss_offset), I(_tbss_size));
if (I(_tbss_size))
bzero(tls + I(_tbss_offset), I(_tbss_size));
// set up thread information block
return _mktls_finish(out_tib, mem, tib);
}
static char *_mktls_above(struct CosmoTib **out_tib) {
size_t hiz, siz;
struct CosmoTib *tib;
char *mem, *dtv, *tls;
// allocate memory for tdata, tbss, and tib
hiz = ROUNDUP(sizeof(*tib) + 2 * sizeof(void *), I(_tls_align));
siz = hiz + I(_tls_size);
mem = memalign(TLS_ALIGNMENT, siz);
// Here's the TLS memory layout on aarch64
//
// x28
// %tpidr_el0
// │
// │ _Thread_local
// ┌───┼───┬──────────┬──────────┐
// │tib│dtv│ .tdata │ .tbss │
// ├───┴───┴──────────┴──────────┘
// │
// __get_tls()
//
size_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 = memalign(I(_tls_align), size);
if (!mem)
return 0;
// poison memory between tdata and tbss
if (IsAsan()) {
__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;
dtv = mem + sizeof(*tib);
tls = mem + hiz;
uintptr_t *dtv = (uintptr_t *)(tib + 1);
size_t dtv_size = sizeof(uintptr_t) * 2;
// set dtv
((uintptr_t *)dtv)[0] = 1;
((void **)dtv)[1] = tls;
// initialize .tdata
char *tdata = (char *)dtv + ROUNDUP(dtv_size, I(_tdata_align));
if (I(_tdata_size)) {
if (IsAsan()) {
__asan_memcpy(tls, _tdata_start, I(_tdata_size));
} else {
memmove(tls, _tdata_start, I(_tdata_size));
}
memmove(tdata, _tdata_start, I(_tdata_size));
}
// clear .tbss
char *tbss = tdata + ROUNDUP(I(_tdata_size), I(_tbss_align));
if (I(_tbss_size)) {
bzero(tls + I(_tbss_offset), I(_tbss_size));
bzero(tbss, I(_tbss_size));
}
// set up thread information block
dtv[0] = 1;
dtv[1] = (uintptr_t)tdata;
return _mktls_finish(out_tib, mem, tib);
}