libsanitizer/sanitizer_common/sanitizer_tls_get_addr.h

   1 //===-- sanitizer_tls_get_addr.h --------------------------------*- C++ -*-===//
   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 // All this magic is specific to glibc and is required to workaround
  11 // the lack of interface that would tell us about the Dynamic TLS (DTLS).
  12 // https://sourceware.org/bugzilla/show_bug.cgi?id=16291
  13 //
  14 // The matters get worse because the glibc implementation changed between
  15 // 2.18 and 2.19:
  16 // https://groups.google.com/forum/#!topic/address-sanitizer/BfwYD8HMxTM
  17 //
  18 // Before 2.19, every DTLS chunk is allocated with __libc_memalign,
  19 // which we intercept and thus know where is the DTLS.
  20 // Since 2.19, DTLS chunks are allocated with __signal_safe_memalign,
  21 // which is an internal function that wraps a mmap call, neither of which
  22 // we can intercept. Luckily, __signal_safe_memalign has a simple parseable
  23 // header which we can use.
  24 //
  25 //===----------------------------------------------------------------------===//
  26
  27 #ifndef SANITIZER_TLS_GET_ADDR_H
  28 #define SANITIZER_TLS_GET_ADDR_H
  29
  30 #include "sanitizer_common.h"
  31
  32 namespace __sanitizer {
  33
  34 struct DTLS {
  35   // Array of DTLS chunks for the current Thread.
  36   // If beg == 0, the chunk is unused.
  37   struct DTV {
  38     uptr beg, size;
  39   };
  40
  41   uptr dtv_size;
  42   DTV *dtv;  // dtv_size elements, allocated by MmapOrDie.
  43
  44   // Auxiliary fields, don't access them outside sanitizer_tls_get_addr.cc
  45   uptr last_memalign_size;
  46   uptr last_memalign_ptr;
  47 };
  48
  49 // Returns pointer and size of a linker-allocated TLS block.
  50 // Each block is returned exactly once.
  51 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res);
  52 void DTLS_on_libc_memalign(void *ptr, uptr size);
  53 DTLS *DTLS_Get();
  54 void DTLS_Destroy();  // Make sure to call this before the thread is destroyed.
  55
  56 }  // namespace __sanitizer
  57
  58 #endif  // SANITIZER_TLS_GET_ADDR_H