1 //===-- sanitizer_tls_get_addr.cc -----------------------------------------===//
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 //===----------------------------------------------------------------------===//
11
12 #include "sanitizer_tls_get_addr.h"
13
14 #include "sanitizer_flags.h"
15 #include "sanitizer_platform_interceptors.h"
16
17 namespace __sanitizer {
18 #if SANITIZER_INTERCEPT_TLS_GET_ADDR
19
20 // The actual parameter that comes to __tls_get_addr
21 // is a pointer to a struct with two words in it:
22 struct TlsGetAddrParam {
23 uptr dso_id;
24 uptr offset;
25 };
26
27 // Glibc starting from 2.19 allocates tls using __signal_safe_memalign,
28 // which has such header.
29 struct Glibc_2_19_tls_header {
30 uptr size;
31 uptr start;
32 };
33
34 // This must be static TLS
35 __attribute__((tls_model("initial-exec")))
36 static __thread DTLS dtls;
37
38 // Make sure we properly destroy the DTLS objects:
39 // this counter should never get too large.
40 static atomic_uintptr_t number_of_live_dtls;
41
42 static const uptr kDestroyedThread = -1;
43
DTLS_Deallocate(DTLS::DTV * dtv,uptr size)44 static inline void DTLS_Deallocate(DTLS::DTV *dtv, uptr size) {
45 if (!size) return;
46 VReport(2, "__tls_get_addr: DTLS_Deallocate %p %zd\n", dtv, size);
47 UnmapOrDie(dtv, size * sizeof(DTLS::DTV));
48 atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed);
49 }
50
DTLS_Resize(uptr new_size)51 static inline void DTLS_Resize(uptr new_size) {
52 if (dtls.dtv_size >= new_size) return;
53 new_size = RoundUpToPowerOfTwo(new_size);
54 new_size = Max(new_size, 4096UL / sizeof(DTLS::DTV));
55 DTLS::DTV *new_dtv =
56 (DTLS::DTV *)MmapOrDie(new_size * sizeof(DTLS::DTV), "DTLS_Resize");
57 uptr num_live_dtls =
58 atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed);
59 VReport(2, "__tls_get_addr: DTLS_Resize %p %zd\n", &dtls, num_live_dtls);
60 CHECK_LT(num_live_dtls, 1 << 20);
61 uptr old_dtv_size = dtls.dtv_size;
62 DTLS::DTV *old_dtv = dtls.dtv;
63 if (old_dtv_size)
64 internal_memcpy(new_dtv, dtls.dtv, dtls.dtv_size * sizeof(DTLS::DTV));
65 dtls.dtv = new_dtv;
66 dtls.dtv_size = new_size;
67 if (old_dtv_size)
68 DTLS_Deallocate(old_dtv, old_dtv_size);
69 }
70
DTLS_Destroy()71 void DTLS_Destroy() {
72 if (!common_flags()->intercept_tls_get_addr) return;
73 VReport(2, "__tls_get_addr: DTLS_Destroy %p %zd\n", &dtls, dtls.dtv_size);
74 uptr s = dtls.dtv_size;
75 dtls.dtv_size = kDestroyedThread; // Do this before unmap for AS-safety.
76 DTLS_Deallocate(dtls.dtv, s);
77 }
78
79 #if defined(__powerpc64__) || defined(__mips__)
80 // This is glibc's TLS_DTV_OFFSET:
81 // "Dynamic thread vector pointers point 0x8000 past the start of each
82 // TLS block."
83 static const uptr kDtvOffset = 0x8000;
84 #else
85 static const uptr kDtvOffset = 0;
86 #endif
87
DTLS_on_tls_get_addr(void * arg_void,void * res,uptr static_tls_begin,uptr static_tls_end)88 DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res,
89 uptr static_tls_begin, uptr static_tls_end) {
90 if (!common_flags()->intercept_tls_get_addr) return 0;
91 TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void);
92 uptr dso_id = arg->dso_id;
93 if (dtls.dtv_size == kDestroyedThread) return 0;
94 DTLS_Resize(dso_id + 1);
95 if (dtls.dtv[dso_id].beg) return 0;
96 uptr tls_size = 0;
97 uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset;
98 VReport(2, "__tls_get_addr: %p {%p,%p} => %p; tls_beg: %p; sp: %p "
99 "num_live_dtls %zd\n",
100 arg, arg->dso_id, arg->offset, res, tls_beg, &tls_beg,
101 atomic_load(&number_of_live_dtls, memory_order_relaxed));
102 if (dtls.last_memalign_ptr == tls_beg) {
103 tls_size = dtls.last_memalign_size;
104 VReport(2, "__tls_get_addr: glibc <=2.18 suspected; tls={%p,%p}\n",
105 tls_beg, tls_size);
106 } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) {
107 // This is the static TLS block which was initialized / unpoisoned at thread
108 // creation.
109 VReport(2, "__tls_get_addr: static tls: %p\n", tls_beg);
110 tls_size = 0;
111 } else if ((tls_beg % 4096) == sizeof(Glibc_2_19_tls_header)) {
112 // We may want to check gnu_get_libc_version().
113 Glibc_2_19_tls_header *header = (Glibc_2_19_tls_header *)tls_beg - 1;
114 tls_size = header->size;
115 tls_beg = header->start;
116 VReport(2, "__tls_get_addr: glibc >=2.19 suspected; tls={%p %p}\n",
117 tls_beg, tls_size);
118 } else {
119 VReport(2, "__tls_get_addr: Can't guess glibc version\n");
120 // This may happen inside the DTOR of main thread, so just ignore it.
121 tls_size = 0;
122 }
123 dtls.dtv[dso_id].beg = tls_beg;
124 dtls.dtv[dso_id].size = tls_size;
125 return dtls.dtv + dso_id;
126 }
127
DTLS_on_libc_memalign(void * ptr,uptr size)128 void DTLS_on_libc_memalign(void *ptr, uptr size) {
129 if (!common_flags()->intercept_tls_get_addr) return;
130 VReport(2, "DTLS_on_libc_memalign: %p %p\n", ptr, size);
131 dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr);
132 dtls.last_memalign_size = size;
133 }
134
DTLS_Get()135 DTLS *DTLS_Get() { return &dtls; }
136
DTLSInDestruction(DTLS * dtls)137 bool DTLSInDestruction(DTLS *dtls) {
138 return dtls->dtv_size == kDestroyedThread;
139 }
140
141 #else
142 void DTLS_on_libc_memalign(void *ptr, uptr size) {}
143 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res) { return 0; }
144 DTLS *DTLS_Get() { return 0; }
145 void DTLS_Destroy() {}
146 bool DTLSInDestruction(DTLS *dtls) {
147 UNREACHABLE("dtls is unsupported on this platform!");
148 }
149
150 #endif // SANITIZER_INTERCEPT_TLS_GET_ADDR
151
152 } // namespace __sanitizer
153