sanitizer_tls_get_addr.cc revision 5d71de26cedae3dafc17449fe0182045c0bd20e8 
1//===-- sanitizer_tls_get_addr.cc -----------------------------------------===//
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//===----------------------------------------------------------------------===//
13
14#include "sanitizer_tls_get_addr.h"
15
16#include "sanitizer_flags.h"
17#include "sanitizer_platform_interceptors.h"
18
19namespace __sanitizer {
20#if SANITIZER_INTERCEPT_TLS_GET_ADDR
21
22// The actual parameter that comes to __tls_get_addr
23// is a pointer to a struct with two words in it:
24struct TlsGetAddrParam {
25  uptr dso_id;
26  uptr offset;
27};
28
29// Glibc starting from 2.19 allocates tls using __signal_safe_memalign,
30// which has such header.
31struct Glibc_2_19_tls_header {
32  uptr size;
33  uptr start;
34};
35
36// This must be static TLS
37__attribute__((tls_model("initial-exec")))
38static __thread DTLS dtls;
39
40// Make sure we properly destroy the DTLS objects:
41// this counter should never get too large.
42static atomic_uintptr_t number_of_live_dtls;
43
44static const uptr kDestroyedThread = -1;
45
46static inline void DTLS_Deallocate(DTLS::DTV *dtv, uptr size) {
47  if (!size) return;
48  VPrintf(2, "__tls_get_addr: DTLS_Deallocate %p %zd\n", dtv, size);
49  UnmapOrDie(dtv, size * sizeof(DTLS::DTV));
50  atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);
51}
52
53static inline void DTLS_Resize(uptr new_size) {
54  if (dtls.dtv_size >= new_size) return;
55  new_size = RoundUpToPowerOfTwo(new_size);
56  new_size = Max(new_size, 4096UL / sizeof(DTLS::DTV));
57  DTLS::DTV *new_dtv =
58      (DTLS::DTV *)MmapOrDie(new_size * sizeof(DTLS::DTV), "DTLS_Resize");
59  uptr num_live_dtls =
60      atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed);
61  VPrintf(2, "__tls_get_addr: DTLS_Resize %p %zd\n", &dtls, num_live_dtls);
62  CHECK_LT(num_live_dtls, 1 << 20);
63  uptr old_dtv_size = dtls.dtv_size;
64  DTLS::DTV *old_dtv = dtls.dtv;
65  if (old_dtv_size)
66    internal_memcpy(new_dtv, dtls.dtv, dtls.dtv_size * sizeof(DTLS::DTV));
67  dtls.dtv = new_dtv;
68  dtls.dtv_size = new_size;
69  if (old_dtv_size)
70    DTLS_Deallocate(old_dtv, old_dtv_size);
71}
72
73void DTLS_Destroy() {
74  if (!common_flags()->intercept_tls_get_addr) return;
75  VPrintf(2, "__tls_get_addr: DTLS_Destroy %p %zd\n", &dtls, dtls.dtv_size);
76  uptr s = dtls.dtv_size;
77  dtls.dtv_size = kDestroyedThread;  // Do this before unmap for AS-safety.
78  DTLS_Deallocate(dtls.dtv, s);
79}
80
81DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res) {
82  if (!common_flags()->intercept_tls_get_addr) return 0;
83  TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);
84  uptr dso_id = arg->dso_id;
85  if (dtls.dtv_size == kDestroyedThread) return 0;
86  DTLS_Resize(dso_id + 1);
87  if (dtls.dtv[dso_id].beg) return 0;
88  uptr tls_size = 0;
89  uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset;
90  VPrintf(2, "__tls_get_addr: %p {%p,%p} => %p; tls_beg: %p; sp: %p "
91             "num_live_dtls %zd\n",
92          arg, arg->dso_id, arg->offset, res, tls_beg, &tls_beg,
93          atomic_load(&number_of_live_dtls, memory_order_relaxed));
94  if (dtls.last_memalign_ptr == tls_beg) {
95    tls_size = dtls.last_memalign_size;
96    VPrintf(2, "__tls_get_addr: glibc <=2.18 suspected; tls={%p,%p}\n",
97        tls_beg, tls_size);
98  } else if ((tls_beg % 4096) == sizeof(Glibc_2_19_tls_header)) {
99    // We may want to check gnu_get_libc_version().
100    Glibc_2_19_tls_header *header = (Glibc_2_19_tls_header *)tls_beg - 1;
101    tls_size = header->size;
102    tls_beg = header->start;
103    VPrintf(2, "__tls_get_addr: glibc >=2.19 suspected; tls={%p %p}\n",
104        tls_beg, tls_size);
105  } else {
106    VPrintf(2, "__tls_get_addr: Can't guess glibc version\n");
107    // This may happen inside the DTOR of main thread, so just ignore it.
108    tls_size = 0;
109  }
110  dtls.dtv[dso_id].beg = tls_beg;
111  dtls.dtv[dso_id].size = tls_size;
112  return dtls.dtv + dso_id;
113}
114
115void DTLS_on_libc_memalign(void *ptr, uptr size) {
116  if (!common_flags()->intercept_tls_get_addr) return;
117  VPrintf(2, "DTLS_on_libc_memalign: %p %p\n", ptr, size);
118  dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
119  dtls.last_memalign_size = size;
120}
121
122DTLS *DTLS_Get() { return &dtls; }
123
124#else
125void DTLS_on_libc_memalign(void *ptr, uptr size) {}
126DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res) { return 0; }
127DTLS *DTLS_Get() { return 0; }
128void DTLS_Destroy() {}
129#endif  // SANITIZER_INTERCEPT_TLS_GET_ADDR
130
131}  // namespace __sanitizer
132