libsanitizer/lsan/lsan_common_linux.cpp

   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, &param);
 141 }
 142
 143 } // namespace __lsan
 144
 145 #endif