1 //=-- lsan_common_linux.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 // This file is a part of LeakSanitizer. 10 // Implementation of common leak checking functionality. Linux/NetBSD-specific 11 // code. 12 // 13 //===----------------------------------------------------------------------===// 14 15 #include "sanitizer_common/sanitizer_platform.h" 16 #include "lsan_common.h" 17 18 #if CAN_SANITIZE_LEAKS && (SANITIZER_LINUX || SANITIZER_NETBSD) 19 #include <link.h> 20 21 #include "sanitizer_common/sanitizer_common.h" 22 #include "sanitizer_common/sanitizer_flags.h" 23 #include "sanitizer_common/sanitizer_getauxval.h" 24 #include "sanitizer_common/sanitizer_linux.h" 25 #include "sanitizer_common/sanitizer_stackdepot.h" 26 27 namespace __lsan { 28 29 static const char kLinkerName[] = "ld"; 30 31 static char linker_placeholder[sizeof(LoadedModule)] ALIGNED(64); 32 static LoadedModule *linker = nullptr; 33 34 static bool IsLinker(const LoadedModule& module) { 35 #if SANITIZER_USE_GETAUXVAL 36 return module.base_address() == getauxval(AT_BASE); 37 #else 38 return LibraryNameIs(module.full_name(), kLinkerName); 39 #endif // SANITIZER_USE_GETAUXVAL 40 } 41 42 __attribute__((tls_model("initial-exec"))) 43 THREADLOCAL int disable_counter; 44 bool DisabledInThisThread() { return disable_counter > 0; } 45 void DisableInThisThread() { disable_counter++; } 46 void EnableInThisThread() { 47 if (disable_counter == 0) { 48 DisableCounterUnderflow(); 49 } 50 disable_counter--; 51 } 52 53 void InitializePlatformSpecificModules() { 54 ListOfModules modules; 55 modules.init(); 56 for (LoadedModule &module : modules) { 57 if (!IsLinker(module)) 58 continue; 59 if (linker == nullptr) { 60 linker = reinterpret_cast<LoadedModule *>(linker_placeholder); 61 *linker = module; 62 module = LoadedModule(); 63 } else { 64 VReport(1, "LeakSanitizer: Multiple modules match \"%s\". " 65 "TLS and other allocations originating from linker might be " 66 "falsely reported as leaks.\n", kLinkerName); 67 linker->clear(); 68 linker = nullptr; 69 return; 70 } 71 } 72 if (linker == nullptr) { 73 VReport(1, "LeakSanitizer: Dynamic linker not found. TLS and other " 74 "allocations originating from linker might be falsely reported " 75 "as leaks.\n"); 76 } 77 } 78 79 static int ProcessGlobalRegionsCallback(struct dl_phdr_info *info, size_t size, 80 void *data) { 81 Frontier *frontier = reinterpret_cast<Frontier *>(data); 82 for (uptr j = 0; j < info->dlpi_phnum; j++) { 83 const ElfW(Phdr) *phdr = &(info->dlpi_phdr[j]); 84 // We're looking for .data and .bss sections, which reside in writeable, 85 // loadable segments. 86 if (!(phdr->p_flags & PF_W) || (phdr->p_type != PT_LOAD) || 87 (phdr->p_memsz == 0)) 88 continue; 89 uptr begin = info->dlpi_addr + phdr->p_vaddr; 90 uptr end = begin + phdr->p_memsz; 91 ScanGlobalRange(begin, end, frontier); 92 } 93 return 0; 94 } 95 96 // Scans global variables for heap pointers. 97 void ProcessGlobalRegions(Frontier *frontier) { 98 if (!flags()->use_globals) return; 99 dl_iterate_phdr(ProcessGlobalRegionsCallback, frontier); 100 } 101 102 LoadedModule *GetLinker() { return linker; } 103 104 void ProcessPlatformSpecificAllocations(Frontier *frontier) {} 105 106 struct DoStopTheWorldParam { 107 StopTheWorldCallback callback; 108 void *argument; 109 }; 110 111 // While calling Die() here is undefined behavior and can potentially 112 // cause race conditions, it isn't possible to intercept exit on linux, 113 // so we have no choice but to call Die() from the atexit handler. 114 void HandleLeaks() { 115 if (common_flags()->exitcode) Die(); 116 } 117 118 static int LockStuffAndStopTheWorldCallback(struct dl_phdr_info *info, 119 size_t size, void *data) { 120 LockThreadRegistry(); 121 LockAllocator(); 122 DoStopTheWorldParam *param = reinterpret_cast<DoStopTheWorldParam *>(data); 123 StopTheWorld(param->callback, param->argument); 124 UnlockAllocator(); 125 UnlockThreadRegistry(); 126 return 1; 127 } 128 129 // LSan calls dl_iterate_phdr() from the tracer task. This may deadlock: if one 130 // of the threads is frozen while holding the libdl lock, the tracer will hang 131 // in dl_iterate_phdr() forever. 132 // Luckily, (a) the lock is reentrant and (b) libc can't distinguish between the 133 // tracer task and the thread that spawned it. Thus, if we run the tracer task 134 // while holding the libdl lock in the parent thread, we can safely reenter it 135 // in the tracer. The solution is to run stoptheworld from a dl_iterate_phdr() 136 // callback in the parent thread. 137 void LockStuffAndStopTheWorld(StopTheWorldCallback callback, 138 CheckForLeaksParam *argument) { 139 DoStopTheWorldParam param = {callback, argument}; 140 dl_iterate_phdr(LockStuffAndStopTheWorldCallback, ¶m); 141 } 142 143 } // namespace __lsan 144 145 #endif 146