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//===-- sanitizer_tls_get_addr.cpp ----------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// Handle the __tls_get_addr call.
//
//===----------------------------------------------------------------------===//
#include "sanitizer_tls_get_addr.h"
#include "sanitizer_atomic.h"
#include "sanitizer_flags.h"
#include "sanitizer_platform_interceptors.h"
namespace __sanitizer {
#if SANITIZER_INTERCEPT_TLS_GET_ADDR
// The actual parameter that comes to __tls_get_addr
// is a pointer to a struct with two words in it:
struct TlsGetAddrParam {
uptr dso_id;
uptr offset;
};
// Glibc starting from 2.19 allocates tls using __signal_safe_memalign,
// which has such header.
struct Glibc_2_19_tls_header {
uptr size;
uptr start;
};
// This must be static TLS
__attribute__((tls_model("initial-exec")))
static __thread DTLS dtls;
// Make sure we properly destroy the DTLS objects:
// this counter should never get too large.
static atomic_uintptr_t number_of_live_dtls;
static const uptr kDestroyedThread = -1;
static void DTLS_Deallocate(DTLS::DTVBlock *block) {
VReport(2, "__tls_get_addr: DTLS_Deallocate %p\n", (void *)block);
UnmapOrDie(block, sizeof(DTLS::DTVBlock));
atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);
}
static DTLS::DTVBlock *DTLS_NextBlock(atomic_uintptr_t *cur) {
uptr v = atomic_load(cur, memory_order_acquire);
if (v == kDestroyedThread)
return nullptr;
DTLS::DTVBlock *next = (DTLS::DTVBlock *)v;
if (next)
return next;
DTLS::DTVBlock *new_dtv =
(DTLS::DTVBlock *)MmapOrDie(sizeof(DTLS::DTVBlock), "DTLS_NextBlock");
uptr prev = 0;
if (!atomic_compare_exchange_strong(cur, &prev, (uptr)new_dtv,
memory_order_seq_cst)) {
UnmapOrDie(new_dtv, sizeof(DTLS::DTVBlock));
return (DTLS::DTVBlock *)prev;
}
uptr num_live_dtls =
atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed);
VReport(2, "__tls_get_addr: DTLS_NextBlock %p %zd\n", (void *)&dtls,
num_live_dtls);
return new_dtv;
}
static DTLS::DTV *DTLS_Find(uptr id) {
VReport(2, "__tls_get_addr: DTLS_Find %p %zd\n", (void *)&dtls, id);
static constexpr uptr kPerBlock = ARRAY_SIZE(DTLS::DTVBlock::dtvs);
DTLS::DTVBlock *cur = DTLS_NextBlock(&dtls.dtv_block);
if (!cur)
return nullptr;
for (; id >= kPerBlock; id -= kPerBlock) cur = DTLS_NextBlock(&cur->next);
return cur->dtvs + id;
}
void DTLS_Destroy() {
if (!common_flags()->intercept_tls_get_addr) return;
VReport(2, "__tls_get_addr: DTLS_Destroy %p\n", (void *)&dtls);
DTLS::DTVBlock *block = (DTLS::DTVBlock *)atomic_exchange(
&dtls.dtv_block, kDestroyedThread, memory_order_release);
while (block) {
DTLS::DTVBlock *next =
(DTLS::DTVBlock *)atomic_load(&block->next, memory_order_acquire);
DTLS_Deallocate(block);
block = next;
}
}
#if defined(__powerpc64__) || defined(__mips__)
// This is glibc's TLS_DTV_OFFSET:
// "Dynamic thread vector pointers point 0x8000 past the start of each
// TLS block." (sysdeps/<arch>/dl-tls.h)
static const uptr kDtvOffset = 0x8000;
#elif defined(__riscv)
// This is glibc's TLS_DTV_OFFSET:
// "Dynamic thread vector pointers point 0x800 past the start of each
// TLS block." (sysdeps/riscv/dl-tls.h)
static const uptr kDtvOffset = 0x800;
#else
static const uptr kDtvOffset = 0;
#endif
DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res,
uptr static_tls_begin, uptr static_tls_end) {
if (!common_flags()->intercept_tls_get_addr) return 0;
TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);
uptr dso_id = arg->dso_id;
DTLS::DTV *dtv = DTLS_Find(dso_id);
if (!dtv || dtv->beg)
return 0;
uptr tls_size = 0;
uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset;
VReport(2,
"__tls_get_addr: %p {0x%zx,0x%zx} => %p; tls_beg: 0x%zx; sp: %p "
"num_live_dtls %zd\n",
(void *)arg, arg->dso_id, arg->offset, res, tls_beg, (void *)&tls_beg,
atomic_load(&number_of_live_dtls, memory_order_relaxed));
if (dtls.last_memalign_ptr == tls_beg) {
tls_size = dtls.last_memalign_size;
VReport(2, "__tls_get_addr: glibc <=2.18 suspected; tls={0x%zx,0x%zx}\n",
tls_beg, tls_size);
} else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {
// This is the static TLS block which was initialized / unpoisoned at thread
// creation.
VReport(2, "__tls_get_addr: static tls: 0x%zx\n", tls_beg);
tls_size = 0;
} else if ((tls_beg % 4096) == sizeof(Glibc_2_19_tls_header)) {
// We may want to check gnu_get_libc_version().
Glibc_2_19_tls_header *header = (Glibc_2_19_tls_header *)tls_beg - 1;
tls_size = header->size;
tls_beg = header->start;
VReport(2, "__tls_get_addr: glibc >=2.19 suspected; tls={0x%zx 0x%zx}\n",
tls_beg, tls_size);
} else {
VReport(2, "__tls_get_addr: Can't guess glibc version\n");
// This may happen inside the DTOR of main thread, so just ignore it.
tls_size = 0;
}
dtv->beg = tls_beg;
dtv->size = tls_size;
return dtv;
}
void DTLS_on_libc_memalign(void *ptr, uptr size) {
if (!common_flags()->intercept_tls_get_addr) return;
VReport(2, "DTLS_on_libc_memalign: %p 0x%zx\n", ptr, size);
dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
dtls.last_memalign_size = size;
}
DTLS *DTLS_Get() { return &dtls; }
bool DTLSInDestruction(DTLS *dtls) {
return atomic_load(&dtls->dtv_block, memory_order_relaxed) ==
kDestroyedThread;
}
#else
void DTLS_on_libc_memalign(void *ptr, uptr size) {}
DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res,
unsigned long, unsigned long) { return 0; }
DTLS *DTLS_Get() { return 0; }
void DTLS_Destroy() {}
bool DTLSInDestruction(DTLS *dtls) {
UNREACHABLE("dtls is unsupported on this platform!");
}
#endif // SANITIZER_INTERCEPT_TLS_GET_ADDR
} // namespace __sanitizer
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