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
20 namespace __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:
25 struct TlsGetAddrParam {
26 uptr dso_id;
27 uptr offset;
28 };
29
30 // This must be static TLS
31 __attribute__((tls_model("initial-exec")))
32 static __thread DTLS dtls;
33
34 // Make sure we properly destroy the DTLS objects:
35 // this counter should never get too large.
36 static atomic_uintptr_t number_of_live_dtls;
37
38 static const uptr kDestroyedThread = -1;
39
DTLS_Deallocate(DTLS::DTVBlock * block)40 static void DTLS_Deallocate(DTLS::DTVBlock *block) {
41 VReport(2, "__tls_get_addr: DTLS_Deallocate %p\n", (void *)block);
42 UnmapOrDie(block, sizeof(DTLS::DTVBlock));
43 atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);
44 }
45
DTLS_NextBlock(atomic_uintptr_t * cur)46 static DTLS::DTVBlock *DTLS_NextBlock(atomic_uintptr_t *cur) {
47 uptr v = atomic_load(cur, 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(sizeof(DTLS::DTVBlock), "DTLS_NextBlock");
55 uptr prev = 0;
56 if (!atomic_compare_exchange_strong(cur, &prev, (uptr)new_dtv,
57 memory_order_seq_cst)) {
58 UnmapOrDie(new_dtv, sizeof(DTLS::DTVBlock));
59 return (DTLS::DTVBlock *)prev;
60 }
61 uptr num_live_dtls =
62 atomic_fetch_add(&number_of_live_dtls, 1, 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
DTLS_Find(uptr id)68 static 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(&dtls.dtv_block);
72 if (!cur)
73 return nullptr;
74 for (; id >= kPerBlock; id -= kPerBlock) cur = DTLS_NextBlock(&cur->next);
75 return cur->dtvs + id;
76 }
77
DTLS_Destroy()78 void 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 &dtls.dtv_block, kDestroyedThread, memory_order_release);
83 while (block) {
84 DTLS::DTVBlock *next =
85 (DTLS::DTVBlock *)atomic_load(&block->next, 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)
95 static 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)
100 static const uptr kDtvOffset = 0x800;
101 #else
102 static const uptr kDtvOffset = 0;
103 #endif
104
105 extern "C" {
106 SANITIZER_WEAK_ATTRIBUTE
107 uptr __sanitizer_get_allocated_size(const void *p);
108
109 SANITIZER_WEAK_ATTRIBUTE
110 const void *__sanitizer_get_allocated_begin(const void *p);
111 }
112
DTLS_on_tls_get_addr(void * arg_void,void * res,uptr static_tls_begin,uptr static_tls_end)113 DTLS::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(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: %p; sp: %p "
125 "num_live_dtls %zd\n",
126 (void *)arg, arg->dso_id, arg->offset, res, (void *)tls_beg,
127 (void *)&tls_beg,
128 atomic_load(&number_of_live_dtls, memory_order_relaxed));
129 if (dtls.last_memalign_ptr == tls_beg) {
130 tls_size = dtls.last_memalign_size;
131 VReport(2, "__tls_get_addr: glibc <=2.24 suspected; tls={%p,0x%zx}\n",
132 (void *)tls_beg, tls_size);
133 } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {
134 // This is the static TLS block which was initialized / unpoisoned at thread
135 // creation.
136 VReport(2, "__tls_get_addr: static tls: %p\n", (void *)tls_beg);
137 tls_size = 0;
138 } else if (const void *start =
139 __sanitizer_get_allocated_begin((void *)tls_beg)) {
140 tls_beg = (uptr)start;
141 tls_size = __sanitizer_get_allocated_size(start);
142 VReport(2, "__tls_get_addr: glibc >=2.25 suspected; tls={%p,0x%zx}\n",
143 (void *)tls_beg, tls_size);
144 } else {
145 VReport(2, "__tls_get_addr: Can't guess glibc version\n");
146 // This may happen inside the DTOR of main thread, so just ignore it.
147 tls_size = 0;
148 }
149 dtv->beg = tls_beg;
150 dtv->size = tls_size;
151 return dtv;
152 }
153
DTLS_on_libc_memalign(void * ptr,uptr size)154 void DTLS_on_libc_memalign(void *ptr, uptr size) {
155 if (!common_flags()->intercept_tls_get_addr) return;
156 VReport(2, "DTLS_on_libc_memalign: %p 0x%zx\n", ptr, size);
157 dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
158 dtls.last_memalign_size = size;
159 }
160
DTLS_Get()161 DTLS *DTLS_Get() { return &dtls; }
162
DTLSInDestruction(DTLS * dtls)163 bool DTLSInDestruction(DTLS *dtls) {
164 return atomic_load(&dtls->dtv_block, memory_order_relaxed) ==
165 kDestroyedThread;
166 }
167
168 #else
169 void DTLS_on_libc_memalign(void *ptr, uptr size) {}
170 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res,
171 unsigned long, unsigned long) { return 0; }
172 DTLS *DTLS_Get() { return 0; }
173 void DTLS_Destroy() {}
174 bool DTLSInDestruction(DTLS *dtls) {
175 UNREACHABLE("dtls is unsupported on this platform!");
176 }
177
178 #endif // SANITIZER_INTERCEPT_TLS_GET_ADDR
179
180 } // namespace __sanitizer
181