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//=-- ------------------------------------------------===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
// This file is a part of LeakSanitizer.
// Implementation of common leak checking functionality. Linux-specific code.
#include "sanitizer_common/sanitizer_platform.h"
#include "lsan_common.h"
#include <link.h>
#include "sanitizer_common/sanitizer_common.h"
#include "sanitizer_common/sanitizer_flags.h"
#include "sanitizer_common/sanitizer_linux.h"
#include "sanitizer_common/sanitizer_stackdepot.h"
namespace __lsan {
static const char kLinkerName[] = "ld";
// We request 2 modules matching "ld", so we can print a warning if there's more
// than one match. But only the first one is actually used.
static char linker_placeholder[2 * sizeof(LoadedModule)] ALIGNED(64);
static LoadedModule *linker = 0;
static bool IsLinker(const char* full_name) {
return LibraryNameIs(full_name, kLinkerName);
void InitializePlatformSpecificModules() {
internal_memset(linker_placeholder, 0, sizeof(linker_placeholder));
uptr num_matches = GetListOfModules(
reinterpret_cast<LoadedModule *>(linker_placeholder), 2, IsLinker);
if (num_matches == 1) {
linker = reinterpret_cast<LoadedModule *>(linker_placeholder);
if (num_matches == 0)
VReport(1, "LeakSanitizer: Dynamic linker not found. "
"TLS will not be handled correctly.\n");
else if (num_matches > 1)
VReport(1, "LeakSanitizer: Multiple modules match \"%s\". "
"TLS will not be handled correctly.\n", kLinkerName);
linker = 0;
static int ProcessGlobalRegionsCallback(struct dl_phdr_info *info, size_t size,
void *data) {
Frontier *frontier = reinterpret_cast<Frontier *>(data);
for (uptr j = 0; j < info->dlpi_phnum; j++) {
const ElfW(Phdr) *phdr = &(info->dlpi_phdr[j]);
// We're looking for .data and .bss sections, which reside in writeable,
// loadable segments.
if (!(phdr->p_flags & PF_W) || (phdr->p_type != PT_LOAD) ||
(phdr->p_memsz == 0))
uptr begin = info->dlpi_addr + phdr->p_vaddr;
uptr end = begin + phdr->p_memsz;
uptr allocator_begin = 0, allocator_end = 0;
GetAllocatorGlobalRange(&allocator_begin, &allocator_end);
if (begin <= allocator_begin && allocator_begin < end) {
CHECK_LE(allocator_begin, allocator_end);
CHECK_LT(allocator_end, end);
if (begin < allocator_begin)
ScanRangeForPointers(begin, allocator_begin, frontier, "GLOBAL",
if (allocator_end < end)
ScanRangeForPointers(allocator_end, end, frontier, "GLOBAL",
} else {
ScanRangeForPointers(begin, end, frontier, "GLOBAL", kReachable);
return 0;
// Scans global variables for heap pointers.
void ProcessGlobalRegions(Frontier *frontier) {
if (!flags()->use_globals) return;
dl_iterate_phdr(ProcessGlobalRegionsCallback, frontier);
static uptr GetCallerPC(u32 stack_id, StackDepotReverseMap *map) {
StackTrace stack = map->Get(stack_id);
// The top frame is our malloc/calloc/etc. The next frame is the caller.
if (stack.size >= 2)
return stack.trace[1];
return 0;
struct ProcessPlatformAllocParam {
Frontier *frontier;
StackDepotReverseMap *stack_depot_reverse_map;
// ForEachChunk callback. Identifies unreachable chunks which must be treated as
// reachable. Marks them as reachable and adds them to the frontier.
static void ProcessPlatformSpecificAllocationsCb(uptr chunk, void *arg) {
ProcessPlatformAllocParam *param =
reinterpret_cast<ProcessPlatformAllocParam *>(arg);
chunk = GetUserBegin(chunk);
LsanMetadata m(chunk);
if (m.allocated() && m.tag() != kReachable && m.tag() != kIgnored) {
u32 stack_id = m.stack_trace_id();
uptr caller_pc = 0;
if (stack_id > 0)
caller_pc = GetCallerPC(stack_id, param->stack_depot_reverse_map);
// If caller_pc is unknown, this chunk may be allocated in a coroutine. Mark
// it as reachable, as we can't properly report its allocation stack anyway.
if (caller_pc == 0 || linker->containsAddress(caller_pc)) {
// Handles dynamically allocated TLS blocks by treating all chunks allocated
// from as reachable.
// Dynamic TLS blocks contain the TLS variables of dynamically loaded modules.
// They are allocated with a __libc_memalign() call in allocate_and_init()
// (elf/dl-tls.c). Glibc won't tell us the address ranges occupied by those
// blocks, but we can make sure they come from our own allocator by intercepting
// __libc_memalign(). On top of that, there is no easy way to reach them. Their
// addresses are stored in a dynamically allocated array (the DTV) which is
// referenced from the static TLS. Unfortunately, we can't just rely on the DTV
// being reachable from the static TLS, and the dynamic TLS being reachable from
// the DTV. This is because the initial DTV is allocated before our interception
// mechanism kicks in, and thus we don't recognize it as allocated memory. We
// can't special-case it either, since we don't know its size.
// Our solution is to include in the root set all allocations made from
// (which is where allocate_and_init() is implemented). This is
// guaranteed to include all dynamic TLS blocks (and possibly other allocations
// which we don't care about).
void ProcessPlatformSpecificAllocations(Frontier *frontier) {
if (!flags()->use_tls) return;
if (!linker) return;
StackDepotReverseMap stack_depot_reverse_map;
ProcessPlatformAllocParam arg = {frontier, &stack_depot_reverse_map};
ForEachChunk(ProcessPlatformSpecificAllocationsCb, &arg);
struct DoStopTheWorldParam {
StopTheWorldCallback callback;
void *argument;
static int DoStopTheWorldCallback(struct dl_phdr_info *info, size_t size,
void *data) {
DoStopTheWorldParam *param = reinterpret_cast<DoStopTheWorldParam *>(data);
StopTheWorld(param->callback, param->argument);
return 1;
// LSan calls dl_iterate_phdr() from the tracer task. This may deadlock: if one
// of the threads is frozen while holding the libdl lock, the tracer will hang
// in dl_iterate_phdr() forever.
// Luckily, (a) the lock is reentrant and (b) libc can't distinguish between the
// tracer task and the thread that spawned it. Thus, if we run the tracer task
// while holding the libdl lock in the parent thread, we can safely reenter it
// in the tracer. The solution is to run stoptheworld from a dl_iterate_phdr()
// callback in the parent thread.
void DoStopTheWorld(StopTheWorldCallback callback, void *argument) {
DoStopTheWorldParam param = {callback, argument};
dl_iterate_phdr(DoStopTheWorldCallback, &param);
} // namespace __lsan