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_atomic.h"
  16 #include "sanitizer_flags.h"
  17 #include "sanitizer_platform_interceptors.h"
  18
  19 namespace __sanitizer {
  20 #if SANITIZER_INTERCEPT_TLS_GET_ADDR
  21
  22 // The actual parameter that comes to __tls_get_addr
  23 // is a pointer to a struct with two words in it:
  24 struct TlsGetAddrParam {
  25   uptr dso_id;
  26   uptr offset;
  27 };
  28
  29 // Glibc starting from 2.19 allocates tls using __signal_safe_memalign,
  30 // which has such header.
  31 struct Glibc_2_19_tls_header {
  32   uptr size;
  33   uptr start;
  34 };
  35
  36 // This must be static TLS
  37 __attribute__((tls_model("initial-exec")))
  38 static __thread DTLS dtls;
  39
  40 // Make sure we properly destroy the DTLS objects:
  41 // this counter should never get too large.
  42 static atomic_uintptr_t number_of_live_dtls;
  43
  44 static const uptr kDestroyedThread = -1;
  45
  46 static void DTLS_Deallocate(DTLS::DTVBlock *block) {
  47   VReport(2, "__tls_get_addr: DTLS_Deallocate %p\n", (void *)block);
  48   UnmapOrDie(block, sizeof(DTLS::DTVBlock));
  49   atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);
  50 }
  51
  52 static DTLS::DTVBlock *DTLS_NextBlock(atomic_uintptr_t *cur) {
  53   uptr v = atomic_load(cur, memory_order_acquire);
  54   if (v == kDestroyedThread)
  55     return nullptr;
  56   DTLS::DTVBlock *next = (DTLS::DTVBlock *)v;
  57   if (next)
  58     return next;
  59   DTLS::DTVBlock *new_dtv =
  60       (DTLS::DTVBlock *)MmapOrDie(sizeof(DTLS::DTVBlock), "DTLS_NextBlock");
  61   uptr prev = 0;
  62   if (!atomic_compare_exchange_strong(cur, &prev, (uptr)new_dtv,
  63                                       memory_order_seq_cst)) {
  64     UnmapOrDie(new_dtv, sizeof(DTLS::DTVBlock));
  65     return (DTLS::DTVBlock *)prev;
  66   }
  67   uptr num_live_dtls =
  68       atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed);
  69   VReport(2, "__tls_get_addr: DTLS_NextBlock %p %zd\n", (void *)&dtls,
  70           num_live_dtls);
  71   return new_dtv;
  72 }
  73
  74 static DTLS::DTV *DTLS_Find(uptr id) {
  75   VReport(2, "__tls_get_addr: DTLS_Find %p %zd\n", (void *)&dtls, id);
  76   static constexpr uptr kPerBlock = ARRAY_SIZE(DTLS::DTVBlock::dtvs);
  77   DTLS::DTVBlock *cur = DTLS_NextBlock(&dtls.dtv_block);
  78   if (!cur)
  79     return nullptr;
  80   for (; id >= kPerBlock; id -= kPerBlock) cur = DTLS_NextBlock(&cur->next);
  81   return cur->dtvs + id;
  82 }
  83
  84 void DTLS_Destroy() {
  85   if (!common_flags()->intercept_tls_get_addr) return;
  86   VReport(2, "__tls_get_addr: DTLS_Destroy %p\n", (void *)&dtls);
  87   DTLS::DTVBlock *block = (DTLS::DTVBlock *)atomic_exchange(
  88       &dtls.dtv_block, kDestroyedThread, memory_order_release);
  89   while (block) {
  90     DTLS::DTVBlock *next =
  91         (DTLS::DTVBlock *)atomic_load(&block->next, memory_order_acquire);
  92     DTLS_Deallocate(block);
  93     block = next;
  94   }
  95 }
  96
  97 #if defined(__powerpc64__) || defined(__mips__)
  98 // This is glibc's TLS_DTV_OFFSET:
  99 // "Dynamic thread vector pointers point 0x8000 past the start of each
 100 //  TLS block." (sysdeps/<arch>/dl-tls.h)
 101 static const uptr kDtvOffset = 0x8000;
 102 #elif defined(__riscv)
 103 // This is glibc's TLS_DTV_OFFSET:
 104 // "Dynamic thread vector pointers point 0x800 past the start of each
 105 // TLS block." (sysdeps/riscv/dl-tls.h)
 106 static const uptr kDtvOffset = 0x800;
 107 #else
 108 static const uptr kDtvOffset = 0;
 109 #endif
 110
 111 DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res,
 112                                 uptr static_tls_begin, uptr static_tls_end) {
 113   if (!common_flags()->intercept_tls_get_addr) return 0;
 114   TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);
 115   uptr dso_id = arg->dso_id;
 116   DTLS::DTV *dtv = DTLS_Find(dso_id);
 117   if (!dtv || dtv->beg)
 118     return 0;
 119   uptr tls_size = 0;
 120   uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset;
 121   VReport(2,
 122           "__tls_get_addr: %p {0x%zx,0x%zx} => %p; tls_beg: 0x%zx; sp: %p "
 123           "num_live_dtls %zd\n",
 124           (void *)arg, arg->dso_id, arg->offset, res, tls_beg, (void *)&tls_beg,
 125           atomic_load(&number_of_live_dtls, memory_order_relaxed));
 126   if (dtls.last_memalign_ptr == tls_beg) {
 127     tls_size = dtls.last_memalign_size;
 128     VReport(2, "__tls_get_addr: glibc <=2.18 suspected; tls={0x%zx,0x%zx}\n",
 129             tls_beg, tls_size);
 130   } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {
 131     // This is the static TLS block which was initialized / unpoisoned at thread
 132     // creation.
 133     VReport(2, "__tls_get_addr: static tls: 0x%zx\n", tls_beg);
 134     tls_size = 0;
 135   } else if ((tls_beg % 4096) == sizeof(Glibc_2_19_tls_header)) {
 136     // We may want to check gnu_get_libc_version().
 137     Glibc_2_19_tls_header *header = (Glibc_2_19_tls_header *)tls_beg - 1;
 138     tls_size = header->size;
 139     tls_beg = header->start;
 140     VReport(2, "__tls_get_addr: glibc >=2.19 suspected; tls={0x%zx 0x%zx}\n",
 141             tls_beg, tls_size);
 142   } else {
 143     VReport(2, "__tls_get_addr: Can't guess glibc version\n");
 144     // This may happen inside the DTOR of main thread, so just ignore it.
 145     tls_size = 0;
 146   }
 147   dtv->beg = tls_beg;
 148   dtv->size = tls_size;
 149   return dtv;
 150 }
 151
 152 void DTLS_on_libc_memalign(void *ptr, uptr size) {
 153   if (!common_flags()->intercept_tls_get_addr) return;
 154   VReport(2, "DTLS_on_libc_memalign: %p 0x%zx\n", ptr, size);
 155   dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
 156   dtls.last_memalign_size = size;
 157 }
 158
 159 DTLS *DTLS_Get() { return &dtls; }
 160
 161 bool DTLSInDestruction(DTLS *dtls) {
 162   return atomic_load(&dtls->dtv_block, memory_order_relaxed) ==
 163          kDestroyedThread;
 164 }
 165
 166 #else
 167 void DTLS_on_libc_memalign(void *ptr, uptr size) {}
 168 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res,
 169   unsigned long, unsigned long) { return 0; }
 170 DTLS *DTLS_Get() { return 0; }
 171 void DTLS_Destroy() {}
 172 bool DTLSInDestruction(DTLS *dtls) {
 173   UNREACHABLE("dtls is unsupported on this platform!");
 174 }
 175
 176 #endif  // SANITIZER_INTERCEPT_TLS_GET_ADDR
 177
 178 }  // namespace __sanitizer