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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_linux.h"
     23 #include "sanitizer_common/sanitizer_stackdepot.h"
     24 
     25 namespace __lsan {
     26 
     27 static const char kLinkerName[] = "ld";
     28 // We request 2 modules matching "ld", so we can print a warning if there's more
     29 // than one match. But only the first one is actually used.
     30 static char linker_placeholder[2 * sizeof(LoadedModule)] ALIGNED(64);
     31 static LoadedModule *linker = 0;
     32 
     33 static bool IsLinker(const char* full_name) {
     34   return LibraryNameIs(full_name, kLinkerName);
     35 }
     36 
     37 void InitializePlatformSpecificModules() {
     38   internal_memset(linker_placeholder, 0, sizeof(linker_placeholder));
     39   uptr num_matches = GetListOfModules(
     40       reinterpret_cast<LoadedModule *>(linker_placeholder), 2, IsLinker);
     41   if (num_matches == 1) {
     42     linker = reinterpret_cast<LoadedModule *>(linker_placeholder);
     43     return;
     44   }
     45   if (num_matches == 0)
     46     Report("LeakSanitizer: Dynamic linker not found. "
     47            "TLS will not be handled correctly.\n");
     48   else if (num_matches > 1)
     49     Report("LeakSanitizer: Multiple modules match \"%s\". "
     50            "TLS will not be handled correctly.\n", kLinkerName);
     51   linker = 0;
     52 }
     53 
     54 static int ProcessGlobalRegionsCallback(struct dl_phdr_info *info, size_t size,
     55                                         void *data) {
     56   Frontier *frontier = reinterpret_cast<Frontier *>(data);
     57   for (uptr j = 0; j < info->dlpi_phnum; j++) {
     58     const ElfW(Phdr) *phdr = &(info->dlpi_phdr[j]);
     59     // We're looking for .data and .bss sections, which reside in writeable,
     60     // loadable segments.
     61     if (!(phdr->p_flags & PF_W) || (phdr->p_type != PT_LOAD) ||
     62         (phdr->p_memsz == 0))
     63       continue;
     64     uptr begin = info->dlpi_addr + phdr->p_vaddr;
     65     uptr end = begin + phdr->p_memsz;
     66     uptr allocator_begin = 0, allocator_end = 0;
     67     GetAllocatorGlobalRange(&allocator_begin, &allocator_end);
     68     if (begin <= allocator_begin && allocator_begin < end) {
     69       CHECK_LE(allocator_begin, allocator_end);
     70       CHECK_LT(allocator_end, end);
     71       if (begin < allocator_begin)
     72         ScanRangeForPointers(begin, allocator_begin, frontier, "GLOBAL",
     73                              kReachable);
     74       if (allocator_end < end)
     75         ScanRangeForPointers(allocator_end, end, frontier, "GLOBAL",
     76                              kReachable);
     77     } else {
     78       ScanRangeForPointers(begin, end, frontier, "GLOBAL", kReachable);
     79     }
     80   }
     81   return 0;
     82 }
     83 
     84 // Scans global variables for heap pointers.
     85 void ProcessGlobalRegions(Frontier *frontier) {
     86   // FIXME: dl_iterate_phdr acquires a linker lock, so we run a risk of
     87   // deadlocking by running this under StopTheWorld. However, the lock is
     88   // reentrant, so we should be able to fix this by acquiring the lock before
     89   // suspending threads.
     90   dl_iterate_phdr(ProcessGlobalRegionsCallback, frontier);
     91 }
     92 
     93 static uptr GetCallerPC(u32 stack_id) {
     94   CHECK(stack_id);
     95   uptr size = 0;
     96   const uptr *trace = StackDepotGet(stack_id, &size);
     97   // The top frame is our malloc/calloc/etc. The next frame is the caller.
     98   if (size >= 2)
     99     return trace[1];
    100   return 0;
    101 }
    102 
    103 // ForEachChunk callback. Identifies unreachable chunks which must be treated as
    104 // reachable. Marks them as reachable and adds them to the frontier.
    105 static void ProcessPlatformSpecificAllocationsCb(uptr chunk, void *arg) {
    106   CHECK(arg);
    107   chunk = GetUserBegin(chunk);
    108   LsanMetadata m(chunk);
    109   if (m.allocated() && m.tag() != kReachable) {
    110     if (linker->containsAddress(GetCallerPC(m.stack_trace_id()))) {
    111       m.set_tag(kReachable);
    112       reinterpret_cast<Frontier *>(arg)->push_back(chunk);
    113     }
    114   }
    115 }
    116 
    117 // Handles dynamically allocated TLS blocks by treating all chunks allocated
    118 // from ld-linux.so as reachable.
    119 void ProcessPlatformSpecificAllocations(Frontier *frontier) {
    120   if (!flags()->use_tls) return;
    121   if (!linker) return;
    122   ForEachChunk(ProcessPlatformSpecificAllocationsCb, frontier);
    123 }
    124 
    125 }  // namespace __lsan
    126 #endif  // CAN_SANITIZE_LEAKS && SANITIZER_LINUX
    127