197 lines · cpp
1//===-- sanitizer_tls_get_addr.cpp ----------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// Handle the __tls_get_addr call.10//11//===----------------------------------------------------------------------===//12 13#include "sanitizer_tls_get_addr.h"14 15#include "sanitizer_allocator_interface.h"16#include "sanitizer_atomic.h"17#include "sanitizer_common/sanitizer_common.h"18#include "sanitizer_common/sanitizer_internal_defs.h"19#include "sanitizer_flags.h"20#include "sanitizer_platform_interceptors.h"21 22namespace __sanitizer {23#if SANITIZER_INTERCEPT_TLS_GET_ADDR24 25// The actual parameter that comes to __tls_get_addr26// is a pointer to a struct with two words in it:27struct TlsGetAddrParam {28 uptr dso_id;29 uptr offset;30};31 32// This must be static TLS33__attribute__((tls_model("initial-exec")))34static __thread DTLS dtls;35 36// Make sure we properly destroy the DTLS objects:37// this counter should never get too large.38static atomic_uintptr_t number_of_live_dtls;39 40static const uptr kDestroyedThread = -1;41 42static void DTLS_Deallocate(DTLS::DTVBlock *block) {43 VReport(2, "__tls_get_addr: DTLS_Deallocate %p\n", (void *)block);44 UnmapOrDie(block, sizeof(DTLS::DTVBlock));45 atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);46}47 48static DTLS::DTVBlock *DTLS_NextBlock(atomic_uintptr_t *cur) {49 uptr v = atomic_load(cur, memory_order_acquire);50 if (v == kDestroyedThread)51 return nullptr;52 DTLS::DTVBlock *next = (DTLS::DTVBlock *)v;53 if (next)54 return next;55 DTLS::DTVBlock *new_dtv =56 (DTLS::DTVBlock *)MmapOrDie(sizeof(DTLS::DTVBlock), "DTLS_NextBlock");57 uptr prev = 0;58 if (!atomic_compare_exchange_strong(cur, &prev, (uptr)new_dtv,59 memory_order_seq_cst)) {60 UnmapOrDie(new_dtv, sizeof(DTLS::DTVBlock));61 return (DTLS::DTVBlock *)prev;62 }63 uptr num_live_dtls =64 atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed);65 VReport(2, "__tls_get_addr: DTLS_NextBlock %p %zd\n", (void *)&dtls,66 num_live_dtls);67 return new_dtv;68}69 70static DTLS::DTV *DTLS_Find(uptr id) {71 VReport(3, "__tls_get_addr: DTLS_Find %p %zd\n", (void *)&dtls, id);72 static constexpr uptr kPerBlock = ARRAY_SIZE(DTLS::DTVBlock::dtvs);73 DTLS::DTVBlock *cur = DTLS_NextBlock(&dtls.dtv_block);74 if (!cur)75 return nullptr;76 for (; id >= kPerBlock; id -= kPerBlock) cur = DTLS_NextBlock(&cur->next);77 return cur->dtvs + id;78}79 80void DTLS_Destroy() {81 if (!common_flags()->intercept_tls_get_addr) return;82 VReport(2, "__tls_get_addr: DTLS_Destroy %p\n", (void *)&dtls);83 DTLS::DTVBlock *block = (DTLS::DTVBlock *)atomic_exchange(84 &dtls.dtv_block, kDestroyedThread, memory_order_release);85 while (block) {86 DTLS::DTVBlock *next =87 (DTLS::DTVBlock *)atomic_load(&block->next, memory_order_acquire);88 DTLS_Deallocate(block);89 block = next;90 }91}92 93#if defined(__powerpc64__) || defined(__mips__)94// This is glibc's TLS_DTV_OFFSET:95// "Dynamic thread vector pointers point 0x8000 past the start of each96// TLS block." (sysdeps/<arch>/dl-tls.h)97static const uptr kDtvOffset = 0x8000;98#elif defined(__riscv)99// This is glibc's TLS_DTV_OFFSET:100// "Dynamic thread vector pointers point 0x800 past the start of each101// TLS block." (sysdeps/riscv/dl-tls.h)102static const uptr kDtvOffset = 0x800;103#else104static const uptr kDtvOffset = 0;105#endif106 107extern "C" {108SANITIZER_WEAK_ATTRIBUTE109uptr __sanitizer_get_allocated_size(const void *p);110 111SANITIZER_WEAK_ATTRIBUTE112const void *__sanitizer_get_allocated_begin(const void *p);113}114 115SANITIZER_INTERFACE_WEAK_DEF(uptr, __sanitizer_get_dtls_size,116 const void *tls_begin) {117 const void *start = __sanitizer_get_allocated_begin(tls_begin);118 if (!start)119 return 0;120 CHECK_LE(start, tls_begin);121 uptr tls_size = __sanitizer_get_allocated_size(start);122 VReport(2, "__tls_get_addr: glibc DTLS suspected; tls={%p,0x%zx}\n",123 tls_begin, tls_size);124 uptr offset =125 (reinterpret_cast<uptr>(tls_begin) - reinterpret_cast<uptr>(start));126 CHECK_LE(offset, tls_size);127 return tls_size - offset;128}129 130DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res,131 uptr static_tls_begin, uptr static_tls_end) {132 if (!common_flags()->intercept_tls_get_addr) return 0;133 TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);134 uptr dso_id = arg->dso_id;135 DTLS::DTV *dtv = DTLS_Find(dso_id);136 if (!dtv || dtv->beg)137 return nullptr;138 CHECK_LE(static_tls_begin, static_tls_end);139 uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset;140 VReport(2,141 "__tls_get_addr: %p {0x%zx,0x%zx} => %p; tls_beg: %p; sp: %p "142 "num_live_dtls %zd\n",143 (void *)arg, arg->dso_id, arg->offset, res, (void *)tls_beg,144 (void *)&tls_beg,145 atomic_load(&number_of_live_dtls, memory_order_relaxed));146 if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {147 // This is the static TLS block which was initialized / unpoisoned at thread148 // creation.149 VReport(2, "__tls_get_addr: static tls: %p\n", (void *)tls_beg);150 dtv->beg = tls_beg;151 dtv->size = 0;152 return nullptr;153 }154 if (uptr tls_size =155 __sanitizer_get_dtls_size(reinterpret_cast<void *>(tls_beg))) {156 dtv->beg = tls_beg;157 dtv->size = tls_size;158 return dtv;159 }160 VReport(2, "__tls_get_addr: Can't guess glibc version\n");161 // This may happen inside the DTOR a thread, or async signal handlers before162 // thread initialization, so just ignore it.163 //164 // If the unknown block is dynamic TLS, unlikely we will be able to recognize165 // it in future, mark it as done with '{tls_beg, 0}'.166 //167 // If the block is static TLS, possible reason of failed detection is nullptr168 // in `static_tls_begin`. Regardless of reasons, the future handling of static169 // TLS is still '{tls_beg, 0}'.170 dtv->beg = tls_beg;171 dtv->size = 0;172 return nullptr;173}174 175DTLS *DTLS_Get() { return &dtls; }176 177bool DTLSInDestruction(DTLS *dtls) {178 return atomic_load(&dtls->dtv_block, memory_order_relaxed) ==179 kDestroyedThread;180}181 182#else183SANITIZER_INTERFACE_WEAK_DEF(uptr, __sanitizer_get_dtls_size, const void *) {184 return 0;185}186DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res,187 unsigned long, unsigned long) { return 0; }188DTLS *DTLS_Get() { return 0; }189void DTLS_Destroy() {}190bool DTLSInDestruction(DTLS *dtls) {191 UNREACHABLE("dtls is unsupported on this platform!");192}193 194#endif // SANITIZER_INTERCEPT_TLS_GET_ADDR195 196} // namespace __sanitizer197