1//===-- sanitizer_tls_get_addr.h --------------------------------*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// Handle the __tls_get_addr call.
11//
12// All this magic is specific to glibc and is required to workaround
13// the lack of interface that would tell us about the Dynamic TLS (DTLS).
14// https://sourceware.org/bugzilla/show_bug.cgi?id=16291
15//
16// The matters get worse because the glibc implementation changed between
17// 2.18 and 2.19:
18// https://groups.google.com/forum/#!topic/address-sanitizer/BfwYD8HMxTM
19//
20// Before 2.19, every DTLS chunk is allocated with __libc_memalign,
21// which we intercept and thus know where is the DTLS.
22// Since 2.19, DTLS chunks are allocated with __signal_safe_memalign,
23// which is an internal function that wraps a mmap call, neither of which
24// we can intercept. Luckily, __signal_safe_memalign has a simple parseable
25// header which we can use.
26//
27//===----------------------------------------------------------------------===//
28
29#ifndef SANITIZER_TLS_GET_ADDR_H
30#define SANITIZER_TLS_GET_ADDR_H
31
32#include "sanitizer_common.h"
33
34namespace __sanitizer {
35
36struct 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
43  uptr dtv_size;
44  DTV *dtv;  // dtv_size elements, allocated by MmapOrDie.
45
46  // Auxiliary fields, don't access them outside sanitizer_tls_get_addr.cc
47  uptr last_memalign_size;
48  uptr last_memalign_ptr;
49};
50
51// Returns pointer and size of a linker-allocated TLS block.
52// Each block is returned exactly once.
53DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res);
54void DTLS_on_libc_memalign(void *ptr, uptr size);
55DTLS *DTLS_Get();
56void DTLS_Destroy();  // Make sure to call this before the thread is destroyed.
57
58}  // namespace __sanitizer
59
60#endif  // SANITIZER_TLS_GET_ADDR_H
61