// Copyright 2017 The Abseil Authors.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "absl/base/attributes.h"
#include "absl/base/config.h"
#if ABSL_HAVE_MMAP
// Disable the glibc prototype of mremap(), as older versions of the
// system headers define this function with only four arguments,
// whereas newer versions allow an optional fifth argument:
#define mremap glibc_mremap
#include <sys/mman.h>
#undef mremap
#endif
#include "absl/base/internal/malloc_hook.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include "absl/base/call_once.h"
#include "absl/base/internal/malloc_hook_invoke.h"
#include "absl/base/internal/raw_logging.h"
#include "absl/base/internal/spinlock.h"
#include "absl/base/macros.h"
// __THROW is defined in glibc systems. It means, counter-intuitively,
// "This function will never throw an exception." It's an optional
// optimization tool, but we may need to use it to match glibc prototypes.
#ifndef __THROW // I guess we're not on a glibc system
# define __THROW // __THROW is just an optimization, so ok to make it ""
#endif
namespace absl {
namespace base_internal {
namespace {
void RemoveInitialHooksAndCallInitializers(); // below.
absl::once_flag once;
// These hooks are installed in MallocHook as the only initial hooks. The first
// hook that is called will run RemoveInitialHooksAndCallInitializers (see the
// definition below) and then redispatch to any malloc hooks installed by
// RemoveInitialHooksAndCallInitializers.
//
// Note(llib): there is a possibility of a race in the event that there are
// multiple threads running before the first allocation. This is pretty
// difficult to achieve, but if it is then multiple threads may concurrently do
// allocations. The first caller will call
// RemoveInitialHooksAndCallInitializers via one of the initial hooks. A
// concurrent allocation may, depending on timing either:
// * still have its initial malloc hook installed, run that and block on waiting
// for the first caller to finish its call to
// RemoveInitialHooksAndCallInitializers, and proceed normally.
// * occur some time during the RemoveInitialHooksAndCallInitializers call, at
// which point there could be no initial hooks and the subsequent hooks that
// are about to be set up by RemoveInitialHooksAndCallInitializers haven't
// been installed yet. I think the worst we can get is that some allocations
// will not get reported to some hooks set by the initializers called from
// RemoveInitialHooksAndCallInitializers.
void InitialNewHook(const void* ptr, size_t size) {
absl::call_once(once, RemoveInitialHooksAndCallInitializers);
MallocHook::InvokeNewHook(ptr, size);
}
void InitialPreMMapHook(const void* start,
size_t size,
int protection,
int flags,
int fd,
off_t offset) {
absl::call_once(once, RemoveInitialHooksAndCallInitializers);
MallocHook::InvokePreMmapHook(start, size, protection, flags, fd, offset);
}
void InitialPreSbrkHook(ptrdiff_t increment) {
absl::call_once(once, RemoveInitialHooksAndCallInitializers);
MallocHook::InvokePreSbrkHook(increment);
}
// This function is called at most once by one of the above initial malloc
// hooks. It removes all initial hooks and initializes all other clients that
// want to get control at the very first memory allocation. The initializers
// may assume that the initial malloc hooks have been removed. The initializers
// may set up malloc hooks and allocate memory.
void RemoveInitialHooksAndCallInitializers() {
ABSL_RAW_CHECK(MallocHook::RemoveNewHook(&InitialNewHook), "");
ABSL_RAW_CHECK(MallocHook::RemovePreMmapHook(&InitialPreMMapHook), "");
ABSL_RAW_CHECK(MallocHook::RemovePreSbrkHook(&InitialPreSbrkHook), "");
}
} // namespace
} // namespace base_internal
} // namespace absl
namespace absl {
namespace base_internal {
// This lock is shared between all implementations of HookList::Add & Remove.
// The potential for contention is very small. This needs to be a SpinLock and
// not a Mutex since it's possible for Mutex locking to allocate memory (e.g.,
// per-thread allocation in debug builds), which could cause infinite recursion.
static absl::base_internal::SpinLock hooklist_spinlock(
absl::base_internal::kLinkerInitialized);
template <typename T>
bool HookList<T>::Add(T value_as_t) {
if (value_as_t == T()) {
return false;
}
absl::base_internal::SpinLockHolder l(&hooklist_spinlock);
// Find the first slot in data that is 0.
int index = 0;
while ((index < kHookListMaxValues) &&
(priv_data[index].load(std::memory_order_relaxed) != 0)) {
++index;
}
if (index == kHookListMaxValues) {
return false;
}
int prev_num_hooks = priv_end.load(std::memory_order_acquire);
priv_data[index].store(reinterpret_cast<intptr_t>(value_as_t),
std::memory_order_release);
if (prev_num_hooks <= index) {
priv_end.store(index + 1, std::memory_order_release);
}
return true;
}
template <typename T>
bool HookList<T>::Remove(T value_as_t) {
if (value_as_t == T()) {
return false;
}
absl::base_internal::SpinLockHolder l(&hooklist_spinlock);
int hooks_end = priv_end.load(std::memory_order_acquire);
int index = 0;
while (index < hooks_end &&
value_as_t != reinterpret_cast<T>(
priv_data[index].load(std::memory_order_acquire))) {
++index;
}
if (index == hooks_end) {
return false;
}
priv_data[index].store(0, std::memory_order_release);
if (hooks_end == index + 1) {
// Adjust hooks_end down to the lowest possible value.
hooks_end = index;
while ((hooks_end > 0) &&
(priv_data[hooks_end - 1].load(std::memory_order_acquire) == 0)) {
--hooks_end;
}
priv_end.store(hooks_end, std::memory_order_release);
}
return true;
}
template <typename T>
int HookList<T>::Traverse(T* output_array, int n) const {
int hooks_end = priv_end.load(std::memory_order_acquire);
int actual_hooks_end = 0;
for (int i = 0; i < hooks_end && n > 0; ++i) {
T data = reinterpret_cast<T>(priv_data[i].load(std::memory_order_acquire));
if (data != T()) {
*output_array++ = data;
++actual_hooks_end;
--n;
}
}
return actual_hooks_end;
}
// Initialize a HookList (optionally with the given initial_value in index 0).
#define INIT_HOOK_LIST { {0}, {{}} }
#define INIT_HOOK_LIST_WITH_VALUE(initial_value) \
{ {1}, { {reinterpret_cast<intptr_t>(initial_value)} } }
// Explicit instantiation for malloc_hook_test.cc. This ensures all the methods
// are instantiated.
template struct HookList<MallocHook::NewHook>;
HookList<MallocHook::NewHook> new_hooks_ =
INIT_HOOK_LIST_WITH_VALUE(&InitialNewHook);
HookList<MallocHook::DeleteHook> delete_hooks_ = INIT_HOOK_LIST;
HookList<MallocHook::SampledNewHook> sampled_new_hooks_ = INIT_HOOK_LIST;
HookList<MallocHook::SampledDeleteHook> sampled_delete_hooks_ = INIT_HOOK_LIST;
HookList<MallocHook::PreMmapHook> premmap_hooks_ =
INIT_HOOK_LIST_WITH_VALUE(&InitialPreMMapHook);
HookList<MallocHook::MmapHook> mmap_hooks_ = INIT_HOOK_LIST;
HookList<MallocHook::MunmapHook> munmap_hooks_ = INIT_HOOK_LIST;
HookList<MallocHook::MremapHook> mremap_hooks_ = INIT_HOOK_LIST;
HookList<MallocHook::PreSbrkHook> presbrk_hooks_ =
INIT_HOOK_LIST_WITH_VALUE(InitialPreSbrkHook);
HookList<MallocHook::SbrkHook> sbrk_hooks_ = INIT_HOOK_LIST;
// These lists contain either 0 or 1 hooks.
HookList<MallocHook::MmapReplacement> mmap_replacement_ = INIT_HOOK_LIST;
HookList<MallocHook::MunmapReplacement> munmap_replacement_ = INIT_HOOK_LIST;
#undef INIT_HOOK_LIST_WITH_VALUE
#undef INIT_HOOK_LIST
} // namespace base_internal
} // namespace absl
// These are available as C bindings as well as C++, hence their
// definition outside the MallocHook class.
extern "C"
int MallocHook_AddNewHook(MallocHook_NewHook hook) {
return absl::base_internal::new_hooks_.Add(hook);
}
extern "C"
int MallocHook_RemoveNewHook(MallocHook_NewHook hook) {
return absl::base_internal::new_hooks_.Remove(hook);
}
extern "C"
int MallocHook_AddDeleteHook(MallocHook_DeleteHook hook) {
return absl::base_internal::delete_hooks_.Add(hook);
}
extern "C"
int MallocHook_RemoveDeleteHook(MallocHook_DeleteHook hook) {
return absl::base_internal::delete_hooks_.Remove(hook);
}
extern "C" int MallocHook_AddSampledNewHook(MallocHook_SampledNewHook hook) {
return absl::base_internal::sampled_new_hooks_.Add(hook);
}
extern "C" int MallocHook_RemoveSampledNewHook(MallocHook_SampledNewHook hook) {
return absl::base_internal::sampled_new_hooks_.Remove(hook);
}
extern "C" int MallocHook_AddSampledDeleteHook(
MallocHook_SampledDeleteHook hook) {
return absl::base_internal::sampled_delete_hooks_.Add(hook);
}
extern "C" int MallocHook_RemoveSampledDeleteHook(
MallocHook_SampledDeleteHook hook) {
return absl::base_internal::sampled_delete_hooks_.Remove(hook);
}
extern "C"
int MallocHook_AddPreMmapHook(MallocHook_PreMmapHook hook) {
return absl::base_internal::premmap_hooks_.Add(hook);
}
extern "C"
int MallocHook_RemovePreMmapHook(MallocHook_PreMmapHook hook) {
return absl::base_internal::premmap_hooks_.Remove(hook);
}
extern "C"
int MallocHook_SetMmapReplacement(MallocHook_MmapReplacement hook) {
// NOTE this is a best effort CHECK. Concurrent sets could succeed since
// this test is outside of the Add spin lock.
ABSL_RAW_CHECK(absl::base_internal::mmap_replacement_.empty(),
"Only one MMapReplacement is allowed.");
return absl::base_internal::mmap_replacement_.Add(hook);
}
extern "C"
int MallocHook_RemoveMmapReplacement(MallocHook_MmapReplacement hook) {
return absl::base_internal::mmap_replacement_.Remove(hook);
}
extern "C"
int MallocHook_AddMmapHook(MallocHook_MmapHook hook) {
return absl::base_internal::mmap_hooks_.Add(hook);
}
extern "C"
int MallocHook_RemoveMmapHook(MallocHook_MmapHook hook) {
return absl::base_internal::mmap_hooks_.Remove(hook);
}
extern "C"
int MallocHook_AddMunmapHook(MallocHook_MunmapHook hook) {
return absl::base_internal::munmap_hooks_.Add(hook);
}
extern "C"
int MallocHook_RemoveMunmapHook(MallocHook_MunmapHook hook) {
return absl::base_internal::munmap_hooks_.Remove(hook);
}
extern "C"
int MallocHook_SetMunmapReplacement(MallocHook_MunmapReplacement hook) {
// NOTE this is a best effort CHECK. Concurrent sets could succeed since
// this test is outside of the Add spin lock.
ABSL_RAW_CHECK(absl::base_internal::munmap_replacement_.empty(),
"Only one MunmapReplacement is allowed.");
return absl::base_internal::munmap_replacement_.Add(hook);
}
extern "C"
int MallocHook_RemoveMunmapReplacement(MallocHook_MunmapReplacement hook) {
return absl::base_internal::munmap_replacement_.Remove(hook);
}
extern "C"
int MallocHook_AddMremapHook(MallocHook_MremapHook hook) {
return absl::base_internal::mremap_hooks_.Add(hook);
}
extern "C"
int MallocHook_RemoveMremapHook(MallocHook_MremapHook hook) {
return absl::base_internal::mremap_hooks_.Remove(hook);
}
extern "C"
int MallocHook_AddPreSbrkHook(MallocHook_PreSbrkHook hook) {
return absl::base_internal::presbrk_hooks_.Add(hook);
}
extern "C"
int MallocHook_RemovePreSbrkHook(MallocHook_PreSbrkHook hook) {
return absl::base_internal::presbrk_hooks_.Remove(hook);
}
extern "C"
int MallocHook_AddSbrkHook(MallocHook_SbrkHook hook) {
return absl::base_internal::sbrk_hooks_.Add(hook);
}
extern "C"
int MallocHook_RemoveSbrkHook(MallocHook_SbrkHook hook) {
return absl::base_internal::sbrk_hooks_.Remove(hook);
}
namespace absl {
namespace base_internal {
// Note: embedding the function calls inside the traversal of HookList would be
// very confusing, as it is legal for a hook to remove itself and add other
// hooks. Doing traversal first, and then calling the hooks ensures we only
// call the hooks registered at the start.
#define INVOKE_HOOKS(HookType, hook_list, args) \
do { \
HookType hooks[kHookListMaxValues]; \
int num_hooks = hook_list.Traverse(hooks, kHookListMaxValues); \
for (int i = 0; i < num_hooks; ++i) { \
(*hooks[i]) args; \
} \
} while (0)
// There should only be one replacement. Return the result of the first
// one, or false if there is none.
#define INVOKE_REPLACEMENT(HookType, hook_list, args) \
do { \
HookType hooks[kHookListMaxValues]; \
int num_hooks = hook_list.Traverse(hooks, kHookListMaxValues); \
return (num_hooks > 0 && (*hooks[0])args); \
} while (0)
void MallocHook::InvokeNewHookSlow(const void* ptr, size_t size) {
INVOKE_HOOKS(NewHook, new_hooks_, (ptr, size));
}
void MallocHook::InvokeDeleteHookSlow(const void* ptr) {
INVOKE_HOOKS(DeleteHook, delete_hooks_, (ptr));
}
void MallocHook::InvokeSampledNewHookSlow(const SampledAlloc* sampled_alloc) {
INVOKE_HOOKS(SampledNewHook, sampled_new_hooks_, (sampled_alloc));
}
void MallocHook::InvokeSampledDeleteHookSlow(AllocHandle handle) {
INVOKE_HOOKS(SampledDeleteHook, sampled_delete_hooks_, (handle));
}
void MallocHook::InvokePreMmapHookSlow(const void* start,
size_t size,
int protection,
int flags,
int fd,
off_t offset) {
INVOKE_HOOKS(PreMmapHook, premmap_hooks_, (start, size, protection, flags, fd,
offset));
}
void MallocHook::InvokeMmapHookSlow(const void* result,
const void* start,
size_t size,
int protection,
int flags,
int fd,
off_t offset) {
INVOKE_HOOKS(MmapHook, mmap_hooks_, (result, start, size, protection, flags,
fd, offset));
}
bool MallocHook::InvokeMmapReplacementSlow(const void* start,
size_t size,
int protection,
int flags,
int fd,
off_t offset,
void** result) {
INVOKE_REPLACEMENT(MmapReplacement, mmap_replacement_,
(start, size, protection, flags, fd, offset, result));
}
void MallocHook::InvokeMunmapHookSlow(const void* start, size_t size) {
INVOKE_HOOKS(MunmapHook, munmap_hooks_, (start, size));
}
bool MallocHook::InvokeMunmapReplacementSlow(const void* start,
size_t size,
int* result) {
INVOKE_REPLACEMENT(MunmapReplacement, munmap_replacement_,
(start, size, result));
}
void MallocHook::InvokeMremapHookSlow(const void* result,
const void* old_addr,
size_t old_size,
size_t new_size,
int flags,
const void* new_addr) {
INVOKE_HOOKS(MremapHook, mremap_hooks_, (result, old_addr, old_size, new_size,
flags, new_addr));
}
void MallocHook::InvokePreSbrkHookSlow(ptrdiff_t increment) {
INVOKE_HOOKS(PreSbrkHook, presbrk_hooks_, (increment));
}
void MallocHook::InvokeSbrkHookSlow(const void* result, ptrdiff_t increment) {
INVOKE_HOOKS(SbrkHook, sbrk_hooks_, (result, increment));
}
#undef INVOKE_HOOKS
#undef INVOKE_REPLACEMENT
} // namespace base_internal
} // namespace absl
ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(malloc_hook);
ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(malloc_hook);
// actual functions are in this file, malloc_hook.cc, and low_level_alloc.cc
ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(google_malloc);
ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(google_malloc);
ABSL_DEFINE_ATTRIBUTE_SECTION_VARS(blink_malloc);
ABSL_DECLARE_ATTRIBUTE_SECTION_VARS(blink_malloc);
#define ADDR_IN_ATTRIBUTE_SECTION(addr, name) \
(reinterpret_cast<uintptr_t>(ABSL_ATTRIBUTE_SECTION_START(name)) <= \
reinterpret_cast<uintptr_t>(addr) && \
reinterpret_cast<uintptr_t>(addr) < \
reinterpret_cast<uintptr_t>(ABSL_ATTRIBUTE_SECTION_STOP(name)))
// Return true iff 'caller' is a return address within a function
// that calls one of our hooks via MallocHook:Invoke*.
// A helper for GetCallerStackTrace.
static inline bool InHookCaller(const void* caller) {
return ADDR_IN_ATTRIBUTE_SECTION(caller, google_malloc) ||
ADDR_IN_ATTRIBUTE_SECTION(caller, malloc_hook) ||
ADDR_IN_ATTRIBUTE_SECTION(caller, blink_malloc);
// We can use one section for everything except tcmalloc_or_debug
// due to its special linkage mode, which prevents merging of the sections.
}
#undef ADDR_IN_ATTRIBUTE_SECTION
static absl::once_flag in_hook_caller_once;
static void InitializeInHookCaller() {
ABSL_INIT_ATTRIBUTE_SECTION_VARS(malloc_hook);
if (ABSL_ATTRIBUTE_SECTION_START(malloc_hook) ==
ABSL_ATTRIBUTE_SECTION_STOP(malloc_hook)) {
ABSL_RAW_LOG(ERROR,
"malloc_hook section is missing, "
"thus InHookCaller is broken!");
}
ABSL_INIT_ATTRIBUTE_SECTION_VARS(google_malloc);
if (ABSL_ATTRIBUTE_SECTION_START(google_malloc) ==
ABSL_ATTRIBUTE_SECTION_STOP(google_malloc)) {
ABSL_RAW_LOG(ERROR,
"google_malloc section is missing, "
"thus InHookCaller is broken!");
}
ABSL_INIT_ATTRIBUTE_SECTION_VARS(blink_malloc);
}
// We can improve behavior/compactness of this function
// if we pass a generic test function (with a generic arg)
// into the implementations for get_stack_trace_fn instead of the skip_count.
extern "C" int MallocHook_GetCallerStackTrace(
void** result, int max_depth, int skip_count,
MallocHook_GetStackTraceFn get_stack_trace_fn) {
if (!ABSL_HAVE_ATTRIBUTE_SECTION) {
// Fall back to get_stack_trace_fn and good old but fragile frame skip
// counts.
// Note: this path is inaccurate when a hook is not called directly by an
// allocation function but is daisy-chained through another hook,
// search for MallocHook::(Get|Set|Invoke)* to find such cases.
#ifdef NDEBUG
return get_stack_trace_fn(result, max_depth, skip_count);
#else
return get_stack_trace_fn(result, max_depth, skip_count + 1);
#endif
// due to -foptimize-sibling-calls in opt mode
// there's no need for extra frame skip here then
}
absl::call_once(in_hook_caller_once, InitializeInHookCaller);
// MallocHook caller determination via InHookCaller works, use it:
static const int kMaxSkip = 32 + 6 + 3;
// Constant tuned to do just one get_stack_trace_fn call below in practice
// and not get many frames that we don't actually need:
// currently max passed max_depth is 32,
// max passed/needed skip_count is 6
// and 3 is to account for some hook daisy chaining.
static const int kStackSize = kMaxSkip + 1;
void* stack[kStackSize];
int depth =
get_stack_trace_fn(stack, kStackSize, 1); // skip this function frame
if (depth == 0)
// silently propagate cases when get_stack_trace_fn does not work
return 0;
for (int i = depth - 1; i >= 0; --i) { // stack[0] is our immediate caller
if (InHookCaller(stack[i])) {
i += 1; // skip hook caller frame
depth -= i; // correct depth
if (depth > max_depth) depth = max_depth;
std::copy(stack + i, stack + i + depth, result);
if (depth < max_depth && depth + i == kStackSize) {
// get frames for the missing depth
depth += get_stack_trace_fn(result + depth, max_depth - depth,
1 + kStackSize);
}
return depth;
}
}
ABSL_RAW_LOG(WARNING,
"Hooked allocator frame not found, returning empty trace");
// If this happens try increasing kMaxSkip
// or else something must be wrong with InHookCaller,
// e.g. for every section used in InHookCaller
// all functions in that section must be inside the same library.
return 0;
}
// On systems where we know how, we override mmap/munmap/mremap/sbrk
// to provide support for calling the related hooks (in addition,
// of course, to doing what these functions normally do).
// The ABSL_MALLOC_HOOK_MMAP_DISABLE macro disables mmap/munmap interceptors.
// Dynamic tools that intercept mmap/munmap can't be linked together with
// malloc_hook interceptors. We disable the malloc_hook interceptors for the
// widely-used dynamic tools, i.e. ThreadSanitizer and MemorySanitizer, but
// still allow users to disable this in special cases that can't be easily
// detected during compilation, via -DABSL_MALLOC_HOOK_MMAP_DISABLE or #define
// ABSL_MALLOC_HOOK_MMAP_DISABLE.
//
// TODO(absl-team): Remove MALLOC_HOOK_MMAP_DISABLE in CROSSTOOL for tsan and
// msan config; Replace MALLOC_HOOK_MMAP_DISABLE with
// ABSL_MALLOC_HOOK_MMAP_DISABLE for other special cases.
#if !defined(THREAD_SANITIZER) && !defined(MEMORY_SANITIZER) && \
!defined(ABSL_MALLOC_HOOK_MMAP_DISABLE) && defined(__linux__)
#include "absl/base/internal/malloc_hook_mmap_linux.inc"
#elif ABSL_HAVE_MMAP
namespace absl {
namespace base_internal {
// static
void* MallocHook::UnhookedMMap(void* start, size_t size, int protection,
int flags, int fd, off_t offset) {
void* result;
if (!MallocHook::InvokeMmapReplacement(
start, size, protection, flags, fd, offset, &result)) {
result = mmap(start, size, protection, flags, fd, offset);
}
return result;
}
// static
int MallocHook::UnhookedMUnmap(void* start, size_t size) {
int result;
if (!MallocHook::InvokeMunmapReplacement(start, size, &result)) {
result = munmap(start, size);
}
return result;
}
} // namespace base_internal
} // namespace absl
#endif