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
63