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 19 namespace __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: 24 struct 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. 31 struct 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"))) 38 static __thread DTLS dtls; 39 40 // Make sure we properly destroy the DTLS objects: 41 // this counter should never get too large. 42 static atomic_uintptr_t number_of_live_dtls; 43 44 static const uptr kDestroyedThread = -1; 45 46 static 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 53 static 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 73 void 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 81 #if defined(__powerpc64__) || defined(__mips__) 82 // This is glibc's TLS_DTV_OFFSET: 83 // "Dynamic thread vector pointers point 0x8000 past the start of each 84 // TLS block." 85 static const uptr kDtvOffset = 0x8000; 86 #else 87 static const uptr kDtvOffset = 0; 88 #endif 89 90 DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res, 91 uptr static_tls_begin, uptr static_tls_end) { 92 if (!common_flags()->intercept_tls_get_addr) return 0; 93 TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void); 94 uptr dso_id = arg->dso_id; 95 if (dtls.dtv_size == kDestroyedThread) return 0; 96 DTLS_Resize(dso_id + 1); 97 if (dtls.dtv[dso_id].beg) return 0; 98 uptr tls_size = 0; 99 uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset; 100 VPrintf(2, "__tls_get_addr: %p {%p,%p} => %p; tls_beg: %p; sp: %p " 101 "num_live_dtls %zd\n", 102 arg, arg->dso_id, arg->offset, res, tls_beg, &tls_beg, 103 atomic_load(&number_of_live_dtls, memory_order_relaxed)); 104 if (dtls.last_memalign_ptr == tls_beg) { 105 tls_size = dtls.last_memalign_size; 106 VPrintf(2, "__tls_get_addr: glibc <=2.18 suspected; tls={%p,%p}\n", 107 tls_beg, tls_size); 108 } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) { 109 // This is the static TLS block which was initialized / unpoisoned at thread 110 // creation. 111 VPrintf(2, "__tls_get_addr: static tls: %p\n", tls_beg); 112 tls_size = 0; 113 } else if ((tls_beg % 4096) == sizeof(Glibc_2_19_tls_header)) { 114 // We may want to check gnu_get_libc_version(). 115 Glibc_2_19_tls_header *header = (Glibc_2_19_tls_header *)tls_beg - 1; 116 tls_size = header->size; 117 tls_beg = header->start; 118 VPrintf(2, "__tls_get_addr: glibc >=2.19 suspected; tls={%p %p}\n", 119 tls_beg, tls_size); 120 } else { 121 VPrintf(2, "__tls_get_addr: Can't guess glibc version\n"); 122 // This may happen inside the DTOR of main thread, so just ignore it. 123 tls_size = 0; 124 } 125 dtls.dtv[dso_id].beg = tls_beg; 126 dtls.dtv[dso_id].size = tls_size; 127 return dtls.dtv + dso_id; 128 } 129 130 void DTLS_on_libc_memalign(void *ptr, uptr size) { 131 if (!common_flags()->intercept_tls_get_addr) return; 132 VPrintf(2, "DTLS_on_libc_memalign: %p %p\n", ptr, size); 133 dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr); 134 dtls.last_memalign_size = size; 135 } 136 137 DTLS *DTLS_Get() { return &dtls; } 138 139 #else 140 void DTLS_on_libc_memalign(void *ptr, uptr size) {} 141 DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res) { return 0; } 142 DTLS *DTLS_Get() { return 0; } 143 void DTLS_Destroy() {} 144 #endif // SANITIZER_INTERCEPT_TLS_GET_ADDR 145 146 } // namespace __sanitizer 147
