compiler-rt/lib/sanitizer_common/sanitizer_tls_get_addr.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-exception
   6 //
   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
  22 namespace __sanitizer {
  23 #if SANITIZER_INTERCEPT_TLS_GET_ADDR
  24
  25 // The actual parameter that comes to __tls_get_addr
  26 // is a pointer to a struct with two words in it:
  27 struct TlsGetAddrParam {
  28   uptr dso_id;
  29   uptr offset;
  30 };
  31
  32 // This must be static TLS
  33 __attribute__((tls_model("initial-exec")))
  34 static __thread DTLS dtls;
  35
  36 // Make sure we properly destroy the DTLS objects:
  37 // this counter should never get too large.
  38 static atomic_uintptr_t number_of_live_dtls;
  39
  40 static const uptr kDestroyedThread = -1;
  41
  42 static 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
  48 static 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
  70 static 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
  80 void 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 each
  96 //  TLS block." (sysdeps/<arch>/dl-tls.h)
  97 static 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 each
 101 // TLS block." (sysdeps/riscv/dl-tls.h)
 102 static const uptr kDtvOffset = 0x800;
 103 #else
 104 static const uptr kDtvOffset = 0;
 105 #endif
 106
 107 extern "C" {
 108 SANITIZER_WEAK_ATTRIBUTE
 109 uptr __sanitizer_get_allocated_size(const void *p);
 110
 111 SANITIZER_WEAK_ATTRIBUTE
 112 const void *__sanitizer_get_allocated_begin(const void *p);
 113 }
 114
 115 SANITIZER_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
 130 DTLS::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 thread
 148     // 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 before
 162   // thread initialization, so just ignore it.
 163   //
 164   // If the unknown block is dynamic TLS, unlikely we will be able to recognize
 165   // 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 nullptr
 168   // in `static_tls_begin`. Regardless of reasons, the future handling of static
 169   // TLS is still '{tls_beg, 0}'.
 170   dtv->beg = tls_beg;
 171   dtv->size = 0;
 172   return nullptr;
 173 }
 174
 175 DTLS *DTLS_Get() { return &dtls; }
 176
 177 bool DTLSInDestruction(DTLS *dtls) {
 178   return atomic_load(&dtls->dtv_block, memory_order_relaxed) ==
 179          kDestroyedThread;
 180 }
 181
 182 #else
 183 SANITIZER_INTERFACE_WEAK_DEF(uptr, __sanitizer_get_dtls_size, const void *) {
 184   return 0;
 185 }
 186 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res,
 187   unsigned long, unsigned long) { return 0; }
 188 DTLS *DTLS_Get() { return 0; }
 189 void DTLS_Destroy() {}
 190 bool DTLSInDestruction(DTLS *dtls) {
 191   UNREACHABLE("dtls is unsupported on this platform!");
 192 }
 193
 194 #endif  // SANITIZER_INTERCEPT_TLS_GET_ADDR
 195
 196 }  // namespace __sanitizer