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