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_flags.h" 16#include "sanitizer_platform_interceptors.h" 17 18namespace __sanitizer { 19#if SANITIZER_INTERCEPT_TLS_GET_ADDR 20 21// The actual parameter that comes to __tls_get_addr 22// is a pointer to a struct with two words in it: 23struct TlsGetAddrParam { 24 uptr dso_id; 25 uptr offset; 26}; 27 28// Glibc starting from 2.19 allocates tls using __signal_safe_memalign, 29// which has such header. 30struct Glibc_2_19_tls_header { 31 uptr size; 32 uptr start; 33}; 34 35// This must be static TLS 36__attribute__((tls_model("initial-exec"))) 37static __thread DTLS dtls; 38 39// Make sure we properly destroy the DTLS objects: 40// this counter should never get too large. 41static atomic_uintptr_t number_of_live_dtls; 42 43static const uptr kDestroyedThread = -1; 44 45static inline void DTLS_Deallocate(DTLS::DTV *dtv, uptr size) { 46 if (!size) return; 47 VReport(2, "__tls_get_addr: DTLS_Deallocate %p %zd\n", dtv, size); 48 UnmapOrDie(dtv, size * sizeof(DTLS::DTV)); 49 atomic_fetch_sub(&number_of_live_dtls, 1, memory_order_relaxed); 50} 51 52static inline void DTLS_Resize(uptr new_size) { 53 if (dtls.dtv_size >= new_size) return; 54 new_size = RoundUpToPowerOfTwo(new_size); 55 new_size = Max(new_size, 4096UL / sizeof(DTLS::DTV)); 56 DTLS::DTV *new_dtv = 57 (DTLS::DTV *)MmapOrDie(new_size * sizeof(DTLS::DTV), "DTLS_Resize"); 58 uptr num_live_dtls = 59 atomic_fetch_add(&number_of_live_dtls, 1, memory_order_relaxed); 60 VReport(2, "__tls_get_addr: DTLS_Resize %p %zd\n", &dtls, num_live_dtls); 61 CHECK_LT(num_live_dtls, 1 << 20); 62 uptr old_dtv_size = dtls.dtv_size; 63 DTLS::DTV *old_dtv = dtls.dtv; 64 if (old_dtv_size) 65 internal_memcpy(new_dtv, dtls.dtv, dtls.dtv_size * sizeof(DTLS::DTV)); 66 dtls.dtv = new_dtv; 67 dtls.dtv_size = new_size; 68 if (old_dtv_size) 69 DTLS_Deallocate(old_dtv, old_dtv_size); 70} 71 72void DTLS_Destroy() { 73 if (!common_flags()->intercept_tls_get_addr) return; 74 VReport(2, "__tls_get_addr: DTLS_Destroy %p %zd\n", &dtls, dtls.dtv_size); 75 uptr s = dtls.dtv_size; 76 dtls.dtv_size = kDestroyedThread; // Do this before unmap for AS-safety. 77 DTLS_Deallocate(dtls.dtv, s); 78} 79 80#if defined(__powerpc64__) || defined(__mips__) 81// This is glibc's TLS_DTV_OFFSET: 82// "Dynamic thread vector pointers point 0x8000 past the start of each 83// TLS block." 84static const uptr kDtvOffset = 0x8000; 85#else 86static const uptr kDtvOffset = 0; 87#endif 88 89DTLS::DTV *DTLS_on_tls_get_addr(void *arg_void, void *res, 90 uptr static_tls_begin, uptr static_tls_end) { 91 if (!common_flags()->intercept_tls_get_addr) return 0; 92 TlsGetAddrParam *arg = reinterpret_cast<TlsGetAddrParam *>(arg_void); 93 uptr dso_id = arg->dso_id; 94 if (dtls.dtv_size == kDestroyedThread) return 0; 95 DTLS_Resize(dso_id + 1); 96 if (dtls.dtv[dso_id].beg) return 0; 97 uptr tls_size = 0; 98 uptr tls_beg = reinterpret_cast<uptr>(res) - arg->offset - kDtvOffset; 99 VReport(2, "__tls_get_addr: %p {%p,%p} => %p; tls_beg: %p; sp: %p " 100 "num_live_dtls %zd\n", 101 arg, arg->dso_id, arg->offset, res, tls_beg, &tls_beg, 102 atomic_load(&number_of_live_dtls, memory_order_relaxed)); 103 if (dtls.last_memalign_ptr == tls_beg) { 104 tls_size = dtls.last_memalign_size; 105 VReport(2, "__tls_get_addr: glibc <=2.18 suspected; tls={%p,%p}\n", 106 tls_beg, tls_size); 107 } else if (tls_beg >= static_tls_begin && tls_beg < static_tls_end) { 108 // This is the static TLS block which was initialized / unpoisoned at thread 109 // creation. 110 VReport(2, "__tls_get_addr: static tls: %p\n", tls_beg); 111 tls_size = 0; 112 } else if ((tls_beg % 4096) == sizeof(Glibc_2_19_tls_header)) { 113 // We may want to check gnu_get_libc_version(). 114 Glibc_2_19_tls_header *header = (Glibc_2_19_tls_header *)tls_beg - 1; 115 tls_size = header->size; 116 tls_beg = header->start; 117 VReport(2, "__tls_get_addr: glibc >=2.19 suspected; tls={%p %p}\n", 118 tls_beg, tls_size); 119 } else { 120 VReport(2, "__tls_get_addr: Can't guess glibc version\n"); 121 // This may happen inside the DTOR of main thread, so just ignore it. 122 tls_size = 0; 123 } 124 dtls.dtv[dso_id].beg = tls_beg; 125 dtls.dtv[dso_id].size = tls_size; 126 return dtls.dtv + dso_id; 127} 128 129void DTLS_on_libc_memalign(void *ptr, uptr size) { 130 if (!common_flags()->intercept_tls_get_addr) return; 131 VReport(2, "DTLS_on_libc_memalign: %p %p\n", ptr, size); 132 dtls.last_memalign_ptr = reinterpret_cast<uptr>(ptr); 133 dtls.last_memalign_size = size; 134} 135 136DTLS *DTLS_Get() { return &dtls; } 137 138bool DTLSInDestruction(DTLS *dtls) { 139 return dtls->dtv_size == kDestroyedThread; 140} 141 142#else 143void DTLS_on_libc_memalign(void *ptr, uptr size) {} 144DTLS::DTV *DTLS_on_tls_get_addr(void *arg, void *res, 145 unsigned long, unsigned long) { return 0; } 146DTLS *DTLS_Get() { return 0; } 147void DTLS_Destroy() {} 148bool DTLSInDestruction(DTLS *dtls) { 149 UNREACHABLE("dtls is unsupported on this platform!"); 150} 151 152#endif // SANITIZER_INTERCEPT_TLS_GET_ADDR 153 154} // namespace __sanitizer 155