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      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_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 DoStopTheWorldCallback(struct dl_phdr_info *info, size_t size,
    119                                   void *data) {
    120   DoStopTheWorldParam *param = reinterpret_cast<DoStopTheWorldParam *>(data);
    121   StopTheWorld(param->callback, param->argument);
    122   return 1;
    123 }
    124 
    125 // LSan calls dl_iterate_phdr() from the tracer task. This may deadlock: if one
    126 // of the threads is frozen while holding the libdl lock, the tracer will hang
    127 // in dl_iterate_phdr() forever.
    128 // Luckily, (a) the lock is reentrant and (b) libc can't distinguish between the
    129 // tracer task and the thread that spawned it. Thus, if we run the tracer task
    130 // while holding the libdl lock in the parent thread, we can safely reenter it
    131 // in the tracer. The solution is to run stoptheworld from a dl_iterate_phdr()
    132 // callback in the parent thread.
    133 void DoStopTheWorld(StopTheWorldCallback callback, void *argument) {
    134   DoStopTheWorldParam param = {callback, argument};
    135   dl_iterate_phdr(DoStopTheWorldCallback, &param);
    136 }
    137 
    138 } // namespace __lsan
    139 
    140 #endif // CAN_SANITIZE_LEAKS && SANITIZER_LINUX
    141