1//===-- sanitizer_tls_get_addr.cpp ----------------------------------------===//
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//===----------------------------------------------------------------------===//
12
13#include "sanitizer_tls_get_addr.h"
14
15#include "sanitizer_allocator_interface.h"
16#include "sanitizer_atomic.h"
17#include "sanitizer_flags.h"
18#include "sanitizer_platform_interceptors.h"
19
20namespace __sanitizer {
21#if SANITIZER_INTERCEPT_TLS_GET_ADDR
22
23// The actual parameter that comes to __tls_get_addr
24// is a pointer to a struct with two words in it:
25struct TlsGetAddrParam {
26 uptr dso_id;
27 uptr offset;
28};
29
30// This must be static TLS
31__attribute__((tls_model("initial-exec")))
32static __thread DTLS dtls;
33
34// Make sure we properly destroy the DTLS objects:
35// this counter should never get too large.
36static atomic_uintptr_t number_of_live_dtls;
37
38static const uptr kDestroyedThread = -1;
39
40static void DTLS_Deallocate(DTLS::DTVBlock *block) {
41 VReport(2, "__tls_get_addr: DTLS_Deallocate %p\n", (void *)block);
42 UnmapOrDie(addr: block, size: sizeof(DTLS::DTVBlock));
43 atomic_fetch_sub(a: &number_of_live_dtls, v: 1, mo: memory_order_relaxed);
44}
45
46static DTLS::DTVBlock *DTLS_NextBlock(atomic_uintptr_t *cur) {
47 uptr v = atomic_load(a: cur, mo: memory_order_acquire);
48 if (v == kDestroyedThread)
49 return nullptr;
50 DTLS::DTVBlock *next = (DTLS::DTVBlock *)v;
51 if (next)
52 return next;
53 DTLS::DTVBlock *new_dtv =
54 (DTLS::DTVBlock *)MmapOrDie(size: sizeof(DTLS::DTVBlock), mem_type: "DTLS_NextBlock");
55 uptr prev = 0;
56 if (!atomic_compare_exchange_strong(a: cur, cmp: &prev, xchg: (uptr)new_dtv,
57 mo: memory_order_seq_cst)) {
58 UnmapOrDie(addr: new_dtv, size: sizeof(DTLS::DTVBlock));
59 return (DTLS::DTVBlock *)prev;
60 }
61 uptr num_live_dtls =
62 atomic_fetch_add(a: &number_of_live_dtls, v: 1, mo: memory_order_relaxed);
63 VReport(2, "__tls_get_addr: DTLS_NextBlock %p %zd\n", (void *)&dtls,
64 num_live_dtls);
65 return new_dtv;
66}
67
68static DTLS::DTV *DTLS_Find(uptr id) {
69 VReport(2, "__tls_get_addr: DTLS_Find %p %zd\n", (void *)&dtls, id);
70 static constexpr uptr kPerBlock = ARRAY_SIZE(DTLS::DTVBlock::dtvs);
71 DTLS::DTVBlock *cur = DTLS_NextBlock(cur: &dtls.dtv_block);
72 if (!cur)
73 return nullptr;
74 for (; id >= kPerBlock; id -= kPerBlock) cur = DTLS_NextBlock(cur: &cur->next);
75 return cur->dtvs + id;
76}
77
78void DTLS_Destroy() {
79 if (!common_flags()->intercept_tls_get_addr) return;
80 VReport(2, "__tls_get_addr: DTLS_Destroy %p\n", (void *)&dtls);
81 DTLS::DTVBlock *block = (DTLS::DTVBlock *)atomic_exchange(
82 a: &dtls.dtv_block, v: kDestroyedThread, mo: memory_order_release);
83 while (block) {
84 DTLS::DTVBlock *next =
85 (DTLS::DTVBlock *)atomic_load(a: &block->next, mo: memory_order_acquire);
86 DTLS_Deallocate(block);
87 block = next;
88 }
89}
90
91#if defined(__powerpc64__) || defined(__mips__)
92// This is glibc's TLS_DTV_OFFSET:
93// "Dynamic thread vector pointers point 0x8000 past the start of each
94// TLS block." (sysdeps/<arch>/dl-tls.h)
95static const uptr kDtvOffset = 0x8000;
96#elif defined(__riscv)
97// This is glibc's TLS_DTV_OFFSET:
98// "Dynamic thread vector pointers point 0x800 past the start of each
99// TLS block." (sysdeps/riscv/dl-tls.h)
100static const uptr kDtvOffset = 0x800;
101#else
102static const uptr kDtvOffset = 0;
103#endif
104
105extern "C" {
106SANITIZER_WEAK_ATTRIBUTE
107uptr __sanitizer_get_allocated_size(const void *p);
108
109SANITIZER_WEAK_ATTRIBUTE
110const void *__sanitizer_get_allocated_begin(const void *p);
111}
112
113DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res,
114 uptr static_tls_begin, uptr static_tls_end) {
115 if (!common_flags()->intercept_tls_get_addr) return 0;
116 TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);
117 uptr dso_id = arg->dso_id;
118 DTLS::DTV *dtv = DTLS_Find(id: dso_id);
119 if (!dtv || dtv->beg)
120 return 0;
121 uptr tls_size = 0;
122 uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset;
123 VReport(2,
124 "__tls_get_addr: %p {0x%zx,0x%zx} => %p; tls_beg: 0x%zx; sp: %p "
125 "num_live_dtls %zd\n",
126 (void *)arg, arg->dso_id, arg->offset, res, tls_beg, (void *)&tls_beg,
127 atomic_load(&number_of_live_dtls, memory_order_relaxed));
128 if (dtls.last_memalign_ptr == tls_beg) {
129 tls_size = dtls.last_memalign_size;
130 VReport(2, "__tls_get_addr: glibc <=2.24 suspected; tls={0x%zx,0x%zx}\n",
131 tls_beg, tls_size);
132 } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {
133 // This is the static TLS block which was initialized / unpoisoned at thread
134 // creation.
135 VReport(2, "__tls_get_addr: static tls: 0x%zx\n", tls_beg);
136 tls_size = 0;
137 } else if (const void *start =
138 __sanitizer_get_allocated_begin(p: (void *)tls_beg)) {
139 tls_beg = (uptr)start;
140 tls_size = __sanitizer_get_allocated_size(p: start);
141 VReport(2, "__tls_get_addr: glibc >=2.25 suspected; tls={0x%zx,0x%zx}\n",
142 tls_beg, tls_size);
143 } else {
144 VReport(2, "__tls_get_addr: Can't guess glibc version\n");
145 // This may happen inside the DTOR of main thread, so just ignore it.
146 tls_size = 0;
147 }
148 dtv->beg = tls_beg;
149 dtv->size = tls_size;
150 return dtv;
151}
152
153void DTLS_on_libc_memalign(void *ptr, uptr size) {
154 if (!common_flags()->intercept_tls_get_addr) return;
155 VReport(2, "DTLS_on_libc_memalign: %p 0x%zx\n", ptr, size);
156 dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
157 dtls.last_memalign_size = size;
158}
159
160DTLS *DTLS_Get() { return &dtls; }
161
162bool DTLSInDestruction(DTLS *dtls) {
163 return atomic_load(a: &dtls->dtv_block, mo: memory_order_relaxed) ==
164 kDestroyedThread;
165}
166
167#else
168void DTLS_on_libc_memalign(void *ptr, uptr size) {}
169DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res,
170 unsigned long, unsigned long) { return 0; }
171DTLS *DTLS_Get() { return 0; }
172void DTLS_Destroy() {}
173bool DTLSInDestruction(DTLS *dtls) {
174 UNREACHABLE("dtls is unsupported on this platform!");
175}
176
177#endif // SANITIZER_INTERCEPT_TLS_GET_ADDR
178
179} // namespace __sanitizer
180

source code of compiler-rt/lib/sanitizer_common/sanitizer_tls_get_addr.cpp