1//=-- lsan_common_linux.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// This file is a part of LeakSanitizer. 11// Implementation of common leak checking functionality. Linux-specific code. 12// 13//===----------------------------------------------------------------------===// 14 15#include "sanitizer_common/sanitizer_platform.h" 16#include "lsan_common.h" 17 18#if CAN_SANITIZE_LEAKS && SANITIZER_LINUX 19#include <link.h> 20 21#include "sanitizer_common/sanitizer_common.h" 22#include "sanitizer_common/sanitizer_flags.h" 23#include "sanitizer_common/sanitizer_linux.h" 24#include "sanitizer_common/sanitizer_stackdepot.h" 25 26namespace __lsan { 27 28static const char kLinkerName[] = "ld"; 29 30static char linker_placeholder[sizeof(LoadedModule)] ALIGNED(64); 31static LoadedModule *linker = nullptr; 32 33static bool IsLinker(const char* full_name) { 34 return LibraryNameIs(full_name, kLinkerName); 35} 36 37void InitializePlatformSpecificModules() { 38 ListOfModules modules; 39 modules.init(); 40 for (LoadedModule &module : modules) { 41 if (!IsLinker(module.full_name())) continue; 42 if (linker == nullptr) { 43 linker = reinterpret_cast<LoadedModule *>(linker_placeholder); 44 *linker = module; 45 module = LoadedModule(); 46 } else { 47 VReport(1, "LeakSanitizer: Multiple modules match \"%s\". " 48 "TLS will not be handled correctly.\n", kLinkerName); 49 linker->clear(); 50 linker = nullptr; 51 return; 52 } 53 } 54 VReport(1, "LeakSanitizer: Dynamic linker not found. " 55 "TLS will not be handled correctly.\n"); 56} 57 58static int ProcessGlobalRegionsCallback(struct dl_phdr_info *info, size_t size, 59 void *data) { 60 Frontier *frontier = reinterpret_cast<Frontier *>(data); 61 for (uptr j = 0; j < info->dlpi_phnum; j++) { 62 const ElfW(Phdr) *phdr = &(info->dlpi_phdr[j]); 63 // We're looking for .data and .bss sections, which reside in writeable, 64 // loadable segments. 65 if (!(phdr->p_flags & PF_W) || (phdr->p_type != PT_LOAD) || 66 (phdr->p_memsz == 0)) 67 continue; 68 uptr begin = info->dlpi_addr + phdr->p_vaddr; 69 uptr end = begin + phdr->p_memsz; 70 uptr allocator_begin = 0, allocator_end = 0; 71 GetAllocatorGlobalRange(&allocator_begin, &allocator_end); 72 if (begin <= allocator_begin && allocator_begin < end) { 73 CHECK_LE(allocator_begin, allocator_end); 74 CHECK_LT(allocator_end, end); 75 if (begin < allocator_begin) 76 ScanRangeForPointers(begin, allocator_begin, frontier, "GLOBAL", 77 kReachable); 78 if (allocator_end < end) 79 ScanRangeForPointers(allocator_end, end, frontier, "GLOBAL", 80 kReachable); 81 } else { 82 ScanRangeForPointers(begin, end, frontier, "GLOBAL", kReachable); 83 } 84 } 85 return 0; 86} 87 88// Scans global variables for heap pointers. 89void ProcessGlobalRegions(Frontier *frontier) { 90 if (!flags()->use_globals) return; 91 dl_iterate_phdr(ProcessGlobalRegionsCallback, frontier); 92} 93 94static uptr GetCallerPC(u32 stack_id, StackDepotReverseMap *map) { 95 CHECK(stack_id); 96 StackTrace stack = map->Get(stack_id); 97 // The top frame is our malloc/calloc/etc. The next frame is the caller. 98 if (stack.size >= 2) 99 return stack.trace[1]; 100 return 0; 101} 102 103struct ProcessPlatformAllocParam { 104 Frontier *frontier; 105 StackDepotReverseMap *stack_depot_reverse_map; 106 bool skip_linker_allocations; 107}; 108 109// ForEachChunk callback. Identifies unreachable chunks which must be treated as 110// reachable. Marks them as reachable and adds them to the frontier. 111static void ProcessPlatformSpecificAllocationsCb(uptr chunk, void *arg) { 112 CHECK(arg); 113 ProcessPlatformAllocParam *param = 114 reinterpret_cast<ProcessPlatformAllocParam *>(arg); 115 chunk = GetUserBegin(chunk); 116 LsanMetadata m(chunk); 117 if (m.allocated() && m.tag() != kReachable && m.tag() != kIgnored) { 118 u32 stack_id = m.stack_trace_id(); 119 uptr caller_pc = 0; 120 if (stack_id > 0) 121 caller_pc = GetCallerPC(stack_id, param->stack_depot_reverse_map); 122 // If caller_pc is unknown, this chunk may be allocated in a coroutine. Mark 123 // it as reachable, as we can't properly report its allocation stack anyway. 124 if (caller_pc == 0 || (param->skip_linker_allocations && 125 linker->containsAddress(caller_pc))) { 126 m.set_tag(kReachable); 127 param->frontier->push_back(chunk); 128 } 129 } 130} 131 132// Handles dynamically allocated TLS blocks by treating all chunks allocated 133// from ld-linux.so as reachable. 134// Dynamic TLS blocks contain the TLS variables of dynamically loaded modules. 135// They are allocated with a __libc_memalign() call in allocate_and_init() 136// (elf/dl-tls.c). Glibc won't tell us the address ranges occupied by those 137// blocks, but we can make sure they come from our own allocator by intercepting 138// __libc_memalign(). On top of that, there is no easy way to reach them. Their 139// addresses are stored in a dynamically allocated array (the DTV) which is 140// referenced from the static TLS. Unfortunately, we can't just rely on the DTV 141// being reachable from the static TLS, and the dynamic TLS being reachable from 142// the DTV. This is because the initial DTV is allocated before our interception 143// mechanism kicks in, and thus we don't recognize it as allocated memory. We 144// can't special-case it either, since we don't know its size. 145// Our solution is to include in the root set all allocations made from 146// ld-linux.so (which is where allocate_and_init() is implemented). This is 147// guaranteed to include all dynamic TLS blocks (and possibly other allocations 148// which we don't care about). 149void ProcessPlatformSpecificAllocations(Frontier *frontier) { 150 StackDepotReverseMap stack_depot_reverse_map; 151 ProcessPlatformAllocParam arg; 152 arg.frontier = frontier; 153 arg.stack_depot_reverse_map = &stack_depot_reverse_map; 154 arg.skip_linker_allocations = 155 flags()->use_tls && flags()->use_ld_allocations && linker != nullptr; 156 ForEachChunk(ProcessPlatformSpecificAllocationsCb, &arg); 157} 158 159struct DoStopTheWorldParam { 160 StopTheWorldCallback callback; 161 void *argument; 162}; 163 164static int DoStopTheWorldCallback(struct dl_phdr_info *info, size_t size, 165 void *data) { 166 DoStopTheWorldParam *param = reinterpret_cast<DoStopTheWorldParam *>(data); 167 StopTheWorld(param->callback, param->argument); 168 return 1; 169} 170 171// LSan calls dl_iterate_phdr() from the tracer task. This may deadlock: if one 172// of the threads is frozen while holding the libdl lock, the tracer will hang 173// in dl_iterate_phdr() forever. 174// Luckily, (a) the lock is reentrant and (b) libc can't distinguish between the 175// tracer task and the thread that spawned it. Thus, if we run the tracer task 176// while holding the libdl lock in the parent thread, we can safely reenter it 177// in the tracer. The solution is to run stoptheworld from a dl_iterate_phdr() 178// callback in the parent thread. 179void DoStopTheWorld(StopTheWorldCallback callback, void *argument) { 180 DoStopTheWorldParam param = {callback, argument}; 181 dl_iterate_phdr(DoStopTheWorldCallback, ¶m); 182} 183 184} // namespace __lsan 185 186#endif // CAN_SANITIZE_LEAKS && SANITIZER_LINUX 187