libsanitizer/lsan/lsan_common_linux.cc

   1 //=-- lsan_common_linux.cc ------------------------------------------------===//
   2 //
   3 // This file is distributed under the University of Illinois Open Source
   4 // License. See LICENSE.TXT for details.
   5 //
   6 //===----------------------------------------------------------------------===//
   7 //
   8 // This file is a part of LeakSanitizer.
   9 // Implementation of common leak checking functionality. Linux-specific code.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "sanitizer_common/sanitizer_platform.h"
  14 #include "lsan_common.h"
  15
  16 #if CAN_SANITIZE_LEAKS && SANITIZER_LINUX
  17 #include <link.h>
  18
  19 #include "sanitizer_common/sanitizer_common.h"
  20 #include "sanitizer_common/sanitizer_flags.h"
  21 #include "sanitizer_common/sanitizer_linux.h"
  22 #include "sanitizer_common/sanitizer_stackdepot.h"
  23
  24 namespace __lsan {
  25
  26 static const char kLinkerName[] = "ld";
  27
  28 static char linker_placeholder[sizeof(LoadedModule)] ALIGNED(64);
  29 static LoadedModule *linker = nullptr;
  30
  31 static bool IsLinker(const char* full_name) {
  32   return LibraryNameIs(full_name, kLinkerName);
  33 }
  34
  35 void InitializePlatformSpecificModules() {
  36   ListOfModules modules;
  37   modules.init();
  38   for (LoadedModule &module : modules) {
  39     if (!IsLinker(module.full_name())) continue;
  40     if (linker == nullptr) {
  41       linker = reinterpret_cast<LoadedModule *>(linker_placeholder);
  42       *linker = module;
  43       module = LoadedModule();
  44     } else {
  45       VReport(1, "LeakSanitizer: Multiple modules match \"%s\". "
  46               "TLS will not be handled correctly.\n", kLinkerName);
  47       linker->clear();
  48       linker = nullptr;
  49       return;
  50     }
  51   }
  52   VReport(1, "LeakSanitizer: Dynamic linker not found. "
  53              "TLS will not be handled correctly.\n");
  54 }
  55
  56 static int ProcessGlobalRegionsCallback(struct dl_phdr_info *info, size_t size,
  57                                         void *data) {
  58   Frontier *frontier = reinterpret_cast<Frontier *>(data);
  59   for (uptr j = 0; j < info->dlpi_phnum; j++) {
  60     const ElfW(Phdr) *phdr = &(info->dlpi_phdr[j]);
  61     // We're looking for .data and .bss sections, which reside in writeable,
  62     // loadable segments.
  63     if (!(phdr->p_flags & PF_W) || (phdr->p_type != PT_LOAD) ||
  64         (phdr->p_memsz == 0))
  65       continue;
  66     uptr begin = info->dlpi_addr + phdr->p_vaddr;
  67     uptr end = begin + phdr->p_memsz;
  68     uptr allocator_begin = 0, allocator_end = 0;
  69     GetAllocatorGlobalRange(&allocator_begin, &allocator_end);
  70     if (begin <= allocator_begin && allocator_begin < end) {
  71       CHECK_LE(allocator_begin, allocator_end);
  72       CHECK_LE(allocator_end, end);
  73       if (begin < allocator_begin)
  74         ScanRangeForPointers(begin, allocator_begin, frontier, "GLOBAL",
  75                              kReachable);
  76       if (allocator_end < end)
  77         ScanRangeForPointers(allocator_end, end, frontier, "GLOBAL",
  78                              kReachable);
  79     } else {
  80       ScanRangeForPointers(begin, end, frontier, "GLOBAL", kReachable);
  81     }
  82   }
  83   return 0;
  84 }
  85
  86 // Scans global variables for heap pointers.
  87 void ProcessGlobalRegions(Frontier *frontier) {
  88   if (!flags()->use_globals) return;
  89   dl_iterate_phdr(ProcessGlobalRegionsCallback, frontier);
  90 }
  91
  92 static uptr GetCallerPC(u32 stack_id, StackDepotReverseMap *map) {
  93   CHECK(stack_id);
  94   StackTrace stack = map->Get(stack_id);
  95   // The top frame is our malloc/calloc/etc. The next frame is the caller.
  96   if (stack.size >= 2)
  97     return stack.trace[1];
  98   return 0;
  99 }
 100
 101 struct ProcessPlatformAllocParam {
 102   Frontier *frontier;
 103   StackDepotReverseMap *stack_depot_reverse_map;
 104   bool skip_linker_allocations;
 105 };
 106
 107 // ForEachChunk callback. Identifies unreachable chunks which must be treated as
 108 // reachable. Marks them as reachable and adds them to the frontier.
 109 static void ProcessPlatformSpecificAllocationsCb(uptr chunk, void *arg) {
 110   CHECK(arg);
 111   ProcessPlatformAllocParam *param =
 112       reinterpret_cast<ProcessPlatformAllocParam *>(arg);
 113   chunk = GetUserBegin(chunk);
 114   LsanMetadata m(chunk);
 115   if (m.allocated() && m.tag() != kReachable && m.tag() != kIgnored) {
 116     u32 stack_id = m.stack_trace_id();
 117     uptr caller_pc = 0;
 118     if (stack_id > 0)
 119       caller_pc = GetCallerPC(stack_id, param->stack_depot_reverse_map);
 120     // If caller_pc is unknown, this chunk may be allocated in a coroutine. Mark
 121     // it as reachable, as we can't properly report its allocation stack anyway.
 122     if (caller_pc == 0 || (param->skip_linker_allocations &&
 123                            linker->containsAddress(caller_pc))) {
 124       m.set_tag(kReachable);
 125       param->frontier->push_back(chunk);
 126     }
 127   }
 128 }
 129
 130 // Handles dynamically allocated TLS blocks by treating all chunks allocated
 131 // from ld-linux.so as reachable.
 132 // Dynamic TLS blocks contain the TLS variables of dynamically loaded modules.
 133 // They are allocated with a __libc_memalign() call in allocate_and_init()
 134 // (elf/dl-tls.c). Glibc won't tell us the address ranges occupied by those
 135 // blocks, but we can make sure they come from our own allocator by intercepting
 136 // __libc_memalign(). On top of that, there is no easy way to reach them. Their
 137 // addresses are stored in a dynamically allocated array (the DTV) which is
 138 // referenced from the static TLS. Unfortunately, we can't just rely on the DTV
 139 // being reachable from the static TLS, and the dynamic TLS being reachable from
 140 // the DTV. This is because the initial DTV is allocated before our interception
 141 // mechanism kicks in, and thus we don't recognize it as allocated memory. We
 142 // can't special-case it either, since we don't know its size.
 143 // Our solution is to include in the root set all allocations made from
 144 // ld-linux.so (which is where allocate_and_init() is implemented). This is
 145 // guaranteed to include all dynamic TLS blocks (and possibly other allocations
 146 // which we don't care about).
 147 void ProcessPlatformSpecificAllocations(Frontier *frontier) {
 148   StackDepotReverseMap stack_depot_reverse_map;
 149   ProcessPlatformAllocParam arg;
 150   arg.frontier = frontier;
 151   arg.stack_depot_reverse_map = &stack_depot_reverse_map;
 152   arg.skip_linker_allocations =
 153       flags()->use_tls && flags()->use_ld_allocations && linker != nullptr;
 154   ForEachChunk(ProcessPlatformSpecificAllocationsCb, &arg);
 155 }
 156
 157 struct DoStopTheWorldParam {
 158   StopTheWorldCallback callback;
 159   void *argument;
 160 };
 161
 162 static int DoStopTheWorldCallback(struct dl_phdr_info *info, size_t size,
 163                                   void *data) {
 164   DoStopTheWorldParam *param = reinterpret_cast<DoStopTheWorldParam *>(data);
 165   StopTheWorld(param->callback, param->argument);
 166   return 1;
 167 }
 168
 169 // LSan calls dl_iterate_phdr() from the tracer task. This may deadlock: if one
 170 // of the threads is frozen while holding the libdl lock, the tracer will hang
 171 // in dl_iterate_phdr() forever.
 172 // Luckily, (a) the lock is reentrant and (b) libc can't distinguish between the
 173 // tracer task and the thread that spawned it. Thus, if we run the tracer task
 174 // while holding the libdl lock in the parent thread, we can safely reenter it
 175 // in the tracer. The solution is to run stoptheworld from a dl_iterate_phdr()
 176 // callback in the parent thread.
 177 void DoStopTheWorld(StopTheWorldCallback callback, void *argument) {
 178   DoStopTheWorldParam param = {callback, argument};
 179   dl_iterate_phdr(DoStopTheWorldCallback, &param);
 180 }
 181
 182 } // namespace __lsan
 183
 184 #endif // CAN_SANITIZE_LEAKS && SANITIZER_LINUX