Home | History | Annotate | Download | only in lsan 
      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 
     26 namespace __lsan {
     27 
     28 static const char kLinkerName[] = "ld";
     29 
     30 static char linker_placeholder[sizeof(LoadedModule)] ALIGNED(64);
     31 static LoadedModule *linker = nullptr;
     32 
     33 static bool IsLinker(const char* full_name) {
     34   return LibraryNameIs(full_name, kLinkerName);
     35 }
     36 
     37 void 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 
     58 static 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.
     89 void ProcessGlobalRegions(Frontier *frontier) {
     90   if (!flags()->use_globals) return;
     91   dl_iterate_phdr(ProcessGlobalRegionsCallback, frontier);
     92 }
     93 
     94 static 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 
    103 struct 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.
    111 static 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).
    149 void 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 
    159 struct DoStopTheWorldParam {
    160   StopTheWorldCallback callback;
    161   void *argument;
    162 };
    163 
    164 static 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.
    179 void DoStopTheWorld(StopTheWorldCallback callback, void *argument) {
    180   DoStopTheWorldParam param = {callback, argument};
    181   dl_iterate_phdr(DoStopTheWorldCallback, &param);
    182 }
    183 
    184 } // namespace __lsan
    185 
    186 #endif // CAN_SANITIZE_LEAKS && SANITIZER_LINUX
    187