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_common.h"
  32
  33 namespace __sanitizer {
  34
  35 struct DTLS {
  36   // Array of DTLS chunks for the current Thread.
  37   // If beg == 0, the chunk is unused.
  38   struct DTV {
  39     uptr beg, size;
  40   };
  41
  42   uptr dtv_size;
  43   DTV *dtv;  // dtv_size elements, allocated by MmapOrDie.
  44
  45   // Auxiliary fields, don't access them outside sanitizer_tls_get_addr.cpp
  46   uptr last_memalign_size;
  47   uptr last_memalign_ptr;
  48 };
  49
  50 // Returns pointer and size of a linker-allocated TLS block.
  51 // Each block is returned exactly once.
  52 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res, uptr static_tls_begin,
  53                                 uptr static_tls_end);
  54 void DTLS_on_libc_memalign(void *ptr, uptr size);
  55 DTLS *DTLS_Get();
  56 void DTLS_Destroy();  // Make sure to call this before the thread is destroyed.
  57 // Returns true if DTLS of suspended thread is in destruction process.
  58 bool DTLSInDestruction(DTLS *dtls);
  59
  60 }  // namespace __sanitizer
  61
  62 #endif  // SANITIZER_TLS_GET_ADDR_H