libsanitizer/sanitizer_common/sanitizer_tls_get_addr.cc

   1 //===-- sanitizer_tls_get_addr.cc -----------------------------------------===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // Handle the __tls_get_addr call.
   9 //
  10 //===----------------------------------------------------------------------===//
  11
  12 #include "sanitizer_tls_get_addr.h"
  13
  14 #include "sanitizer_flags.h"
  15 #include "sanitizer_platform_interceptors.h"
  16
  17 namespace __sanitizer {
  18 #if SANITIZER_INTERCEPT_TLS_GET_ADDR
  19
  20 // The actual parameter that comes to __tls_get_addr
  21 // is a pointer to a struct with two words in it:
  22 struct TlsGetAddrParam {
  23   uptr dso_id;
  24   uptr offset;
  25 };
  26
  27 // Glibc starting from 2.19 allocates tls using __signal_safe_memalign,
  28 // which has such header.
  29 struct Glibc_2_19_tls_header {
  30   uptr size;
  31   uptr start;
  32 };
  33
  34 // This must be static TLS
  35 __attribute__((tls_model("initial-exec")))
  36 static __thread DTLS dtls;
  37
  38 // Make sure we properly destroy the DTLS objects:
  39 // this counter should never get too large.
  40 static atomic_uintptr_t number_of_live_dtls;
  41
  42 static const uptr kDestroyedThread = -1;
  43
  44 static inline void DTLS_Deallocate(DTLS::DTV *dtv, uptr size) {
  45   if (!size) return;
  46   VPrintf(2, "__tls_get_addr: DTLS_Deallocate %p %zd\n", dtv, size);
  47   UnmapOrDie(dtv, size * sizeof(DTLS::DTV));
  48   atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);
  49 }
  50
  51 static inline void DTLS_Resize(uptr new_size) {
  52   if (dtls.dtv_size >= new_size) return;
  53   new_size = RoundUpToPowerOfTwo(new_size);
  54   new_size = Max(new_size, 4096UL / sizeof(DTLS::DTV));
  55   DTLS::DTV *new_dtv =
  56       (DTLS::DTV *)MmapOrDie(new_size * sizeof(DTLS::DTV), "DTLS_Resize");
  57   uptr num_live_dtls =
  58       atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed);
  59   VPrintf(2, "__tls_get_addr: DTLS_Resize %p %zd\n", &dtls, num_live_dtls);
  60   CHECK_LT(num_live_dtls, 1 << 20);
  61   uptr old_dtv_size = dtls.dtv_size;
  62   DTLS::DTV *old_dtv = dtls.dtv;
  63   if (old_dtv_size)
  64     internal_memcpy(new_dtv, dtls.dtv, dtls.dtv_size * sizeof(DTLS::DTV));
  65   dtls.dtv = new_dtv;
  66   dtls.dtv_size = new_size;
  67   if (old_dtv_size)
  68     DTLS_Deallocate(old_dtv, old_dtv_size);
  69 }
  70
  71 void DTLS_Destroy() {
  72   if (!common_flags()->intercept_tls_get_addr) return;
  73   VPrintf(2, "__tls_get_addr: DTLS_Destroy %p %zd\n", &dtls, dtls.dtv_size);
  74   uptr s = dtls.dtv_size;
  75   dtls.dtv_size = kDestroyedThread;  // Do this before unmap for AS-safety.
  76   DTLS_Deallocate(dtls.dtv, s);
  77 }
  78
  79 #if defined(__powerpc64__) || defined(__mips__)
  80 // This is glibc's TLS_DTV_OFFSET:
  81 // "Dynamic thread vector pointers point 0x8000 past the start of each
  82 //  TLS block."
  83 static const uptr kDtvOffset = 0x8000;
  84 #else
  85 static const uptr kDtvOffset = 0;
  86 #endif
  87
  88 DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res,
  89                                 uptr static_tls_begin, uptr static_tls_end) {
  90   if (!common_flags()->intercept_tls_get_addr) return 0;
  91   TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);
  92   uptr dso_id = arg->dso_id;
  93   if (dtls.dtv_size == kDestroyedThread) return 0;
  94   DTLS_Resize(dso_id + 1);
  95   if (dtls.dtv[dso_id].beg) return 0;
  96   uptr tls_size = 0;
  97   uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset;
  98   VPrintf(2, "__tls_get_addr: %p {%p,%p} => %p; tls_beg: %p; sp: %p "
  99              "num_live_dtls %zd\n",
 100           arg, arg->dso_id, arg->offset, res, tls_beg, &tls_beg,
 101           atomic_load(&number_of_live_dtls, memory_order_relaxed));
 102   if (dtls.last_memalign_ptr == tls_beg) {
 103     tls_size = dtls.last_memalign_size;
 104     VPrintf(2, "__tls_get_addr: glibc <=2.18 suspected; tls={%p,%p}\n",
 105         tls_beg, tls_size);
 106   } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {
 107     // This is the static TLS block which was initialized / unpoisoned at thread
 108     // creation.
 109     VPrintf(2, "__tls_get_addr: static tls: %p\n", tls_beg);
 110     tls_size = 0;
 111   } else if ((tls_beg % 4096) == sizeof(Glibc_2_19_tls_header)) {
 112     // We may want to check gnu_get_libc_version().
 113     Glibc_2_19_tls_header *header = (Glibc_2_19_tls_header *)tls_beg - 1;
 114     tls_size = header->size;
 115     tls_beg = header->start;
 116     VPrintf(2, "__tls_get_addr: glibc >=2.19 suspected; tls={%p %p}\n",
 117         tls_beg, tls_size);
 118   } else {
 119     VPrintf(2, "__tls_get_addr: Can't guess glibc version\n");
 120     // This may happen inside the DTOR of main thread, so just ignore it.
 121     tls_size = 0;
 122   }
 123   dtls.dtv[dso_id].beg = tls_beg;
 124   dtls.dtv[dso_id].size = tls_size;
 125   return dtls.dtv + dso_id;
 126 }
 127
 128 void DTLS_on_libc_memalign(void *ptr, uptr size) {
 129   if (!common_flags()->intercept_tls_get_addr) return;
 130   VPrintf(2, "DTLS_on_libc_memalign: %p %p\n", ptr, size);
 131   dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
 132   dtls.last_memalign_size = size;
 133 }
 134
 135 DTLS *DTLS_Get() { return &dtls; }
 136
 137 #else
 138 void DTLS_on_libc_memalign(void *ptr, uptr size) {}
 139 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res) { return 0; }
 140 DTLS *DTLS_Get() { return 0; }
 141 void DTLS_Destroy() {}
 142 #endif  // SANITIZER_INTERCEPT_TLS_GET_ADDR
 143
 144 }  // namespace __sanitizer