libsanitizer/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_flags.h"
  18 #include "sanitizer_platform_interceptors.h"
  19
  20 namespace __sanitizer {
  21 #if SANITIZER_INTERCEPT_TLS_GET_ADDR
  22
  23 // The actual parameter that comes to __tls_get_addr
  24 // is a pointer to a struct with two words in it:
  25 struct TlsGetAddrParam {
  26   uptr dso_id;
  27   uptr offset;
  28 };
  29
  30 // This must be static TLS
  31 __attribute__((tls_model("initial-exec")))
  32 static __thread DTLS dtls;
  33
  34 // Make sure we properly destroy the DTLS objects:
  35 // this counter should never get too large.
  36 static atomic_uintptr_t number_of_live_dtls;
  37
  38 static const uptr kDestroyedThread = -1;
  39
  40 static void DTLS_Deallocate(DTLS::DTVBlock *block) {
  41   VReport(2, "__tls_get_addr: DTLS_Deallocate %p\n", (void *)block);
  42   UnmapOrDie(block, sizeof(DTLS::DTVBlock));
  43   atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);
  44 }
  45
  46 static DTLS::DTVBlock *DTLS_NextBlock(atomic_uintptr_t *cur) {
  47   uptr v = atomic_load(cur, memory_order_acquire);
  48   if (v == kDestroyedThread)
  49     return nullptr;
  50   DTLS::DTVBlock *next = (DTLS::DTVBlock *)v;
  51   if (next)
  52     return next;
  53   DTLS::DTVBlock *new_dtv =
  54       (DTLS::DTVBlock *)MmapOrDie(sizeof(DTLS::DTVBlock), "DTLS_NextBlock");
  55   uptr prev = 0;
  56   if (!atomic_compare_exchange_strong(cur, &prev, (uptr)new_dtv,
  57                                       memory_order_seq_cst)) {
  58     UnmapOrDie(new_dtv, sizeof(DTLS::DTVBlock));
  59     return (DTLS::DTVBlock *)prev;
  60   }
  61   uptr num_live_dtls =
  62       atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed);
  63   VReport(2, "__tls_get_addr: DTLS_NextBlock %p %zd\n", (void *)&dtls,
  64           num_live_dtls);
  65   return new_dtv;
  66 }
  67
  68 static DTLS::DTV *DTLS_Find(uptr id) {
  69   VReport(2, "__tls_get_addr: DTLS_Find %p %zd\n", (void *)&dtls, id);
  70   static constexpr uptr kPerBlock = ARRAY_SIZE(DTLS::DTVBlock::dtvs);
  71   DTLS::DTVBlock *cur = DTLS_NextBlock(&dtls.dtv_block);
  72   if (!cur)
  73     return nullptr;
  74   for (; id >= kPerBlock; id -= kPerBlock) cur = DTLS_NextBlock(&cur->next);
  75   return cur->dtvs + id;
  76 }
  77
  78 void DTLS_Destroy() {
  79   if (!common_flags()->intercept_tls_get_addr) return;
  80   VReport(2, "__tls_get_addr: DTLS_Destroy %p\n", (void *)&dtls);
  81   DTLS::DTVBlock *block = (DTLS::DTVBlock *)atomic_exchange(
  82       &dtls.dtv_block, kDestroyedThread, memory_order_release);
  83   while (block) {
  84     DTLS::DTVBlock *next =
  85         (DTLS::DTVBlock *)atomic_load(&block->next, memory_order_acquire);
  86     DTLS_Deallocate(block);
  87     block = next;
  88   }
  89 }
  90
  91 #if defined(__powerpc64__) || defined(__mips__)
  92 // This is glibc's TLS_DTV_OFFSET:
  93 // "Dynamic thread vector pointers point 0x8000 past the start of each
  94 //  TLS block." (sysdeps/<arch>/dl-tls.h)
  95 static const uptr kDtvOffset = 0x8000;
  96 #elif defined(__riscv)
  97 // This is glibc's TLS_DTV_OFFSET:
  98 // "Dynamic thread vector pointers point 0x800 past the start of each
  99 // TLS block." (sysdeps/riscv/dl-tls.h)
 100 static const uptr kDtvOffset = 0x800;
 101 #else
 102 static const uptr kDtvOffset = 0;
 103 #endif
 104
 105 extern "C" {
 106 SANITIZER_WEAK_ATTRIBUTE
 107 uptr __sanitizer_get_allocated_size(const void *p);
 108
 109 SANITIZER_WEAK_ATTRIBUTE
 110 const void *__sanitizer_get_allocated_begin(const void *p);
 111 }
 112
 113 DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res,
 114                                 uptr static_tls_begin, uptr static_tls_end) {
 115   if (!common_flags()->intercept_tls_get_addr) return 0;
 116   TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);
 117   uptr dso_id = arg->dso_id;
 118   DTLS::DTV *dtv = DTLS_Find(dso_id);
 119   if (!dtv || dtv->beg)
 120     return 0;
 121   uptr tls_size = 0;
 122   uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset;
 123   VReport(2,
 124           "__tls_get_addr: %p {0x%zx,0x%zx} => %p; tls_beg: 0x%zx; sp: %p "
 125           "num_live_dtls %zd\n",
 126           (void *)arg, arg->dso_id, arg->offset, res, tls_beg, (void *)&tls_beg,
 127           atomic_load(&number_of_live_dtls, memory_order_relaxed));
 128   if (dtls.last_memalign_ptr == tls_beg) {
 129     tls_size = dtls.last_memalign_size;
 130     VReport(2, "__tls_get_addr: glibc <=2.24 suspected; tls={0x%zx,0x%zx}\n",
 131             tls_beg, tls_size);
 132   } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {
 133     // This is the static TLS block which was initialized / unpoisoned at thread
 134     // creation.
 135     VReport(2, "__tls_get_addr: static tls: 0x%zx\n", tls_beg);
 136     tls_size = 0;
 137   } else if (const void *start =
 138                  __sanitizer_get_allocated_begin((void *)tls_beg)) {
 139     tls_beg = (uptr)start;
 140     tls_size = __sanitizer_get_allocated_size(start);
 141     VReport(2, "__tls_get_addr: glibc >=2.25 suspected; tls={0x%zx,0x%zx}\n",
 142             tls_beg, tls_size);
 143   } else {
 144     VReport(2, "__tls_get_addr: Can't guess glibc version\n");
 145     // This may happen inside the DTOR of main thread, so just ignore it.
 146     tls_size = 0;
 147   }
 148   dtv->beg = tls_beg;
 149   dtv->size = tls_size;
 150   return dtv;
 151 }
 152
 153 void DTLS_on_libc_memalign(void *ptr, uptr size) {
 154   if (!common_flags()->intercept_tls_get_addr) return;
 155   VReport(2, "DTLS_on_libc_memalign: %p 0x%zx\n", ptr, size);
 156   dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
 157   dtls.last_memalign_size = size;
 158 }
 159
 160 DTLS *DTLS_Get() { return &dtls; }
 161
 162 bool DTLSInDestruction(DTLS *dtls) {
 163   return atomic_load(&dtls->dtv_block, memory_order_relaxed) ==
 164          kDestroyedThread;
 165 }
 166
 167 #else
 168 void DTLS_on_libc_memalign(void *ptr, uptr size) {}
 169 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res,
 170   unsigned long, unsigned long) { return 0; }
 171 DTLS *DTLS_Get() { return 0; }
 172 void DTLS_Destroy() {}
 173 bool DTLSInDestruction(DTLS *dtls) {
 174   UNREACHABLE("dtls is unsupported on this platform!");
 175 }
 176
 177 #endif  // SANITIZER_INTERCEPT_TLS_GET_ADDR
 178
 179 }  // namespace __sanitizer