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, uptr static_tls_begin,
52                                 uptr static_tls_end);
53 void DTLS_on_libc_memalign(void *ptr, uptr size);
54 DTLS *DTLS_Get();
55 void DTLS_Destroy();  // Make sure to call this before the thread is destroyed.
56 // Returns true if DTLS of suspended thread is in destruction process.
57 bool DTLSInDestruction(DTLS *dtls);
58 
59 }  // namespace __sanitizer
60 
61 #endif  // SANITIZER_TLS_GET_ADDR_H
62