libsanitizer/sanitizer_common/sanitizer_tls_get_addr.h

   1 //===-- sanitizer_tls_get_addr.h --------------------------------*- C++ -*-===//
   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 // All this magic is specific to glibc and is required to workaround
  12 // the lack of interface that would tell us about the Dynamic TLS (DTLS).
  13 // https://sourceware.org/bugzilla/show_bug.cgi?id=16291
  14 //
  15 // The matters get worse because the glibc implementation changed between
  16 // 2.18 and 2.19:
  17 // https://groups.google.com/forum/#!topic/address-sanitizer/BfwYD8HMxTM
  18 //
  19 // Before 2.19, every DTLS chunk is allocated with __libc_memalign,
  20 // which we intercept and thus know where is the DTLS.
  21 // Since 2.19, DTLS chunks are allocated with __signal_safe_memalign,
  22 // which is an internal function that wraps a mmap call, neither of which
  23 // we can intercept. Luckily, __signal_safe_memalign has a simple parseable
  24 // header which we can use.
  25 //
  26 //===----------------------------------------------------------------------===//
  27
  28 #ifndef SANITIZER_TLS_GET_ADDR_H
  29 #define SANITIZER_TLS_GET_ADDR_H
  30
  31 #include "sanitizer_atomic.h"
  32 #include "sanitizer_common.h"
  33
  34 namespace __sanitizer {
  35
  36 struct DTLS {
  37   // Array of DTLS chunks for the current Thread.
  38   // If beg == 0, the chunk is unused.
  39   struct DTV {
  40     uptr beg, size;
  41   };
  42   struct DTVBlock {
  43     atomic_uintptr_t next;
  44     DTV dtvs[(4096UL - sizeof(next)) / sizeof(DTLS::DTV)];
  45   };
  46
  47   static_assert(sizeof(DTVBlock) <= 4096UL, "Unexpected block size");
  48
  49   atomic_uintptr_t dtv_block;
  50
  51   // Auxiliary fields, don't access them outside sanitizer_tls_get_addr.cpp
  52   uptr last_memalign_size;
  53   uptr last_memalign_ptr;
  54 };
  55
  56 template <typename Fn>
  57 void ForEachDVT(DTLS *dtls, const Fn &fn) {
  58   DTLS::DTVBlock *block =
  59       (DTLS::DTVBlock *)atomic_load(&dtls->dtv_block, memory_order_acquire);
  60   while (block) {
  61     int id = 0;
  62     for (auto &d : block->dtvs) fn(d, id++);
  63     block = (DTLS::DTVBlock *)atomic_load(&block->next, memory_order_acquire);
  64   }
  65 }
  66
  67 // Returns pointer and size of a linker-allocated TLS block.
  68 // Each block is returned exactly once.
  69 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res, uptr static_tls_begin,
  70                                 uptr static_tls_end);
  71 void DTLS_on_libc_memalign(void *ptr, uptr size);
  72 DTLS *DTLS_Get();
  73 void DTLS_Destroy();  // Make sure to call this before the thread is destroyed.
  74 // Returns true if DTLS of suspended thread is in destruction process.
  75 bool DTLSInDestruction(DTLS *dtls);
  76
  77 }  // namespace __sanitizer
  78
  79 #endif  // SANITIZER_TLS_GET_ADDR_H