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//===-- scudo_allocator.cpp -------------------------------------*- C++ -*-===//
// The LLVM Compiler Infrastructure
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
/// Scudo Hardened Allocator implementation.
/// It uses the sanitizer_common allocator as a base and aims at mitigating
/// heap corruption vulnerabilities. It provides a checksum-guarded chunk
/// header, a delayed free list, and additional sanity checks.
#include "scudo_allocator.h"
#include "scudo_crc32.h"
#include "scudo_errors.h"
#include "scudo_flags.h"
#include "scudo_interface_internal.h"
#include "scudo_tsd.h"
#include "scudo_utils.h"
#include "sanitizer_common/sanitizer_allocator_checks.h"
#include "sanitizer_common/sanitizer_allocator_interface.h"
#include "sanitizer_common/sanitizer_quarantine.h"
#include <errno.h>
#include <string.h>
namespace __scudo {
// Global static cookie, initialized at start-up.
static u32 Cookie;
// We default to software CRC32 if the alternatives are not supported, either
// at compilation or at runtime.
static atomic_uint8_t HashAlgorithm = { CRC32Software };
INLINE u32 computeCRC32(u32 Crc, uptr Value, uptr *Array, uptr ArraySize) {
// If the hardware CRC32 feature is defined here, it was enabled everywhere,
// as opposed to only for scudo_crc32.cpp. This means that other hardware
// specific instructions were likely emitted at other places, and as a
// result there is no reason to not use it here.
#if defined(__SSE4_2__) || defined(__ARM_FEATURE_CRC32)
Crc = CRC32_INTRINSIC(Crc, Value);
for (uptr i = 0; i < ArraySize; i++)
Crc = CRC32_INTRINSIC(Crc, Array[i]);
return Crc;
if (atomic_load_relaxed(&HashAlgorithm) == CRC32Hardware) {
Crc = computeHardwareCRC32(Crc, Value);
for (uptr i = 0; i < ArraySize; i++)
Crc = computeHardwareCRC32(Crc, Array[i]);
return Crc;
Crc = computeSoftwareCRC32(Crc, Value);
for (uptr i = 0; i < ArraySize; i++)
Crc = computeSoftwareCRC32(Crc, Array[i]);
return Crc;
#endif // defined(__SSE4_2__) || defined(__ARM_FEATURE_CRC32)
static BackendT &getBackend();
namespace Chunk {
static INLINE AtomicPackedHeader *getAtomicHeader(void *Ptr) {
return reinterpret_cast<AtomicPackedHeader *>(reinterpret_cast<uptr>(Ptr) -
static INLINE
const AtomicPackedHeader *getConstAtomicHeader(const void *Ptr) {
return reinterpret_cast<const AtomicPackedHeader *>(
reinterpret_cast<uptr>(Ptr) - getHeaderSize());
static INLINE bool isAligned(const void *Ptr) {
return IsAligned(reinterpret_cast<uptr>(Ptr), MinAlignment);
// We can't use the offset member of the chunk itself, as we would double
// fetch it without any warranty that it wouldn't have been tampered. To
// prevent this, we work with a local copy of the header.
static INLINE void *getBackendPtr(const void *Ptr, UnpackedHeader *Header) {
return reinterpret_cast<void *>(reinterpret_cast<uptr>(Ptr) -
getHeaderSize() - (Header->Offset << MinAlignmentLog));
// Returns the usable size for a chunk, meaning the amount of bytes from the
// beginning of the user data to the end of the backend allocated chunk.
static INLINE uptr getUsableSize(const void *Ptr, UnpackedHeader *Header) {
const uptr ClassId = Header->ClassId;
if (ClassId)
return PrimaryT::ClassIdToSize(ClassId) - getHeaderSize() -
(Header->Offset << MinAlignmentLog);
return SecondaryT::GetActuallyAllocatedSize(
getBackendPtr(Ptr, Header)) - getHeaderSize();
// Returns the size the user requested when allocating the chunk.
static INLINE uptr getSize(const void *Ptr, UnpackedHeader *Header) {
const uptr SizeOrUnusedBytes = Header->SizeOrUnusedBytes;
if (Header->ClassId)
return SizeOrUnusedBytes;
return SecondaryT::GetActuallyAllocatedSize(
getBackendPtr(Ptr, Header)) - getHeaderSize() - SizeOrUnusedBytes;
// Compute the checksum of the chunk pointer and its header.
static INLINE u16 computeChecksum(const void *Ptr, UnpackedHeader *Header) {
UnpackedHeader ZeroChecksumHeader = *Header;
ZeroChecksumHeader.Checksum = 0;
uptr HeaderHolder[sizeof(UnpackedHeader) / sizeof(uptr)];
memcpy(&HeaderHolder, &ZeroChecksumHeader, sizeof(HeaderHolder));
const u32 Crc = computeCRC32(Cookie, reinterpret_cast<uptr>(Ptr),
HeaderHolder, ARRAY_SIZE(HeaderHolder));
return static_cast<u16>(Crc);
// Checks the validity of a chunk by verifying its checksum. It doesn't
// incur termination in the event of an invalid chunk.
static INLINE bool isValid(const void *Ptr) {
PackedHeader NewPackedHeader =
UnpackedHeader NewUnpackedHeader =
return (NewUnpackedHeader.Checksum ==
computeChecksum(Ptr, &NewUnpackedHeader));
// Nulls out a chunk header. When returning the chunk to the backend, there
// is no need to store a valid ChunkAvailable header, as this would be
// computationally expensive. Zeroing out serves the same purpose by making
// the header invalid. In the extremely rare event where 0 would be a valid
// checksum for the chunk, the state of the chunk is ChunkAvailable anyway.
COMPILER_CHECK(ChunkAvailable == 0);
static INLINE void eraseHeader(void *Ptr) {
const PackedHeader NullPackedHeader = 0;
atomic_store_relaxed(getAtomicHeader(Ptr), NullPackedHeader);
// Loads and unpacks the header, verifying the checksum in the process.
static INLINE
void loadHeader(const void *Ptr, UnpackedHeader *NewUnpackedHeader) {
PackedHeader NewPackedHeader =
*NewUnpackedHeader = bit_cast<UnpackedHeader>(NewPackedHeader);
if (UNLIKELY(NewUnpackedHeader->Checksum !=
computeChecksum(Ptr, NewUnpackedHeader)))
dieWithMessage("corrupted chunk header at address %p\n", Ptr);
// Packs and stores the header, computing the checksum in the process.
static INLINE void storeHeader(void *Ptr, UnpackedHeader *NewUnpackedHeader) {
NewUnpackedHeader->Checksum = computeChecksum(Ptr, NewUnpackedHeader);
PackedHeader NewPackedHeader = bit_cast<PackedHeader>(*NewUnpackedHeader);
atomic_store_relaxed(getAtomicHeader(Ptr), NewPackedHeader);
// Packs and stores the header, computing the checksum in the process. We
// compare the current header with the expected provided one to ensure that
// we are not being raced by a corruption occurring in another thread.
static INLINE void compareExchangeHeader(void *Ptr,
UnpackedHeader *NewUnpackedHeader,
UnpackedHeader *OldUnpackedHeader) {
NewUnpackedHeader->Checksum = computeChecksum(Ptr, NewUnpackedHeader);
PackedHeader NewPackedHeader = bit_cast<PackedHeader>(*NewUnpackedHeader);
PackedHeader OldPackedHeader = bit_cast<PackedHeader>(*OldUnpackedHeader);
if (UNLIKELY(!atomic_compare_exchange_strong(
getAtomicHeader(Ptr), &OldPackedHeader, NewPackedHeader,
dieWithMessage("race on chunk header at address %p\n", Ptr);
} // namespace Chunk
struct QuarantineCallback {
explicit QuarantineCallback(AllocatorCacheT *Cache)
: Cache_(Cache) {}
// Chunk recycling function, returns a quarantined chunk to the backend,
// first making sure it hasn't been tampered with.
void Recycle(void *Ptr) {
UnpackedHeader Header;
Chunk::loadHeader(Ptr, &Header);
if (UNLIKELY(Header.State != ChunkQuarantine))
dieWithMessage("invalid chunk state when recycling address %p\n", Ptr);
void *BackendPtr = Chunk::getBackendPtr(Ptr, &Header);
if (Header.ClassId)
getBackend().deallocatePrimary(Cache_, BackendPtr, Header.ClassId);
// Internal quarantine allocation and deallocation functions. We first check
// that the batches are indeed serviced by the Primary.
// TODO(kostyak): figure out the best way to protect the batches.
void *Allocate(uptr Size) {
const uptr BatchClassId = SizeClassMap::ClassID(sizeof(QuarantineBatch));
return getBackend().allocatePrimary(Cache_, BatchClassId);
void Deallocate(void *Ptr) {
const uptr BatchClassId = SizeClassMap::ClassID(sizeof(QuarantineBatch));
getBackend().deallocatePrimary(Cache_, Ptr, BatchClassId);
AllocatorCacheT *Cache_;
COMPILER_CHECK(sizeof(QuarantineBatch) < SizeClassMap::kMaxSize);
typedef Quarantine<QuarantineCallback, void> QuarantineT;
typedef QuarantineT::Cache QuarantineCacheT;
COMPILER_CHECK(sizeof(QuarantineCacheT) <=
QuarantineCacheT *getQuarantineCache(ScudoTSD *TSD) {
return reinterpret_cast<QuarantineCacheT *>(TSD->QuarantineCachePlaceHolder);
struct Allocator {
static const uptr MaxAllowedMallocSize =
FIRST_32_SECOND_64(2UL << 30, 1ULL << 40);
BackendT Backend;
QuarantineT Quarantine;
u32 QuarantineChunksUpToSize;
bool DeallocationTypeMismatch;
bool ZeroContents;
bool DeleteSizeMismatch;
bool CheckRssLimit;
uptr HardRssLimitMb;
uptr SoftRssLimitMb;
atomic_uint8_t RssLimitExceeded;
atomic_uint64_t RssLastCheckedAtNS;
explicit Allocator(LinkerInitialized)
NOINLINE void performSanityChecks();
void init() {
SanitizerToolName = "Scudo";
PrimaryAllocatorName = "ScudoPrimary";
SecondaryAllocatorName = "ScudoSecondary";
// Check if hardware CRC32 is supported in the binary and by the platform,
// if so, opt for the CRC32 hardware version of the checksum.
if (&computeHardwareCRC32 && hasHardwareCRC32())
atomic_store_relaxed(&HashAlgorithm, CRC32Hardware);
HardRssLimitMb = common_flags()->hard_rss_limit_mb;
SoftRssLimitMb = common_flags()->soft_rss_limit_mb;
static_cast<uptr>(getFlags()->QuarantineSizeKb) << 10,
static_cast<uptr>(getFlags()->ThreadLocalQuarantineSizeKb) << 10);
QuarantineChunksUpToSize = getFlags()->QuarantineChunksUpToSize;
DeallocationTypeMismatch = getFlags()->DeallocationTypeMismatch;
DeleteSizeMismatch = getFlags()->DeleteSizeMismatch;
ZeroContents = getFlags()->ZeroContents;
if (UNLIKELY(!GetRandom(reinterpret_cast<void *>(&Cookie), sizeof(Cookie),
/*blocking=*/false))) {
Cookie = static_cast<u32>((NanoTime() >> 12) ^
(reinterpret_cast<uptr>(this) >> 4));
CheckRssLimit = HardRssLimitMb || SoftRssLimitMb;
if (CheckRssLimit)
atomic_store_relaxed(&RssLastCheckedAtNS, MonotonicNanoTime());
// Helper function that checks for a valid Scudo chunk. nullptr isn't.
bool isValidPointer(const void *Ptr) {
if (UNLIKELY(!Ptr))
return false;
if (!Chunk::isAligned(Ptr))
return false;
return Chunk::isValid(Ptr);
NOINLINE bool isRssLimitExceeded();
// Allocates a chunk.
void *allocate(uptr Size, uptr Alignment, AllocType Type,
bool ForceZeroContents = false) {
if (UNLIKELY(Alignment > MaxAlignment)) {
if (AllocatorMayReturnNull())
return nullptr;
reportAllocationAlignmentTooBig(Alignment, MaxAlignment);
if (UNLIKELY(Alignment < MinAlignment))
Alignment = MinAlignment;
const uptr NeededSize = RoundUpTo(Size ? Size : 1, MinAlignment) +
const uptr AlignedSize = (Alignment > MinAlignment) ?
NeededSize + (Alignment - Chunk::getHeaderSize()) : NeededSize;
if (UNLIKELY(Size >= MaxAllowedMallocSize) ||
UNLIKELY(AlignedSize >= MaxAllowedMallocSize)) {
if (AllocatorMayReturnNull())
return nullptr;
reportAllocationSizeTooBig(Size, AlignedSize, MaxAllowedMallocSize);
if (CheckRssLimit && UNLIKELY(isRssLimitExceeded())) {
if (AllocatorMayReturnNull())
return nullptr;
// Primary and Secondary backed allocations have a different treatment. We
// deal with alignment requirements of Primary serviced allocations here,
// but the Secondary will take care of its own alignment needs.
void *BackendPtr;
uptr BackendSize;
u8 ClassId;
if (PrimaryT::CanAllocate(AlignedSize, MinAlignment)) {
BackendSize = AlignedSize;
ClassId = SizeClassMap::ClassID(BackendSize);
bool UnlockRequired;
ScudoTSD *TSD = getTSDAndLock(&UnlockRequired);
BackendPtr = Backend.allocatePrimary(&TSD->Cache, ClassId);
if (UnlockRequired)
} else {
BackendSize = NeededSize;
ClassId = 0;
BackendPtr = Backend.allocateSecondary(BackendSize, Alignment);
if (UNLIKELY(!BackendPtr)) {
if (AllocatorMayReturnNull())
return nullptr;
// If requested, we will zero out the entire contents of the returned chunk.
if ((ForceZeroContents || ZeroContents) && ClassId)
memset(BackendPtr, 0, PrimaryT::ClassIdToSize(ClassId));
UnpackedHeader Header = {};
uptr UserPtr = reinterpret_cast<uptr>(BackendPtr) + Chunk::getHeaderSize();
if (UNLIKELY(!IsAligned(UserPtr, Alignment))) {
// Since the Secondary takes care of alignment, a non-aligned pointer
// means it is from the Primary. It is also the only case where the offset
// field of the header would be non-zero.
const uptr AlignedUserPtr = RoundUpTo(UserPtr, Alignment);
Header.Offset = (AlignedUserPtr - UserPtr) >> MinAlignmentLog;
UserPtr = AlignedUserPtr;
DCHECK_LE(UserPtr + Size, reinterpret_cast<uptr>(BackendPtr) + BackendSize);
Header.State = ChunkAllocated;
Header.AllocType = Type;
if (ClassId) {
Header.ClassId = ClassId;
Header.SizeOrUnusedBytes = Size;
} else {
// The secondary fits the allocations to a page, so the amount of unused
// bytes is the difference between the end of the user allocation and the
// next page boundary.
const uptr PageSize = GetPageSizeCached();
const uptr TrailingBytes = (UserPtr + Size) & (PageSize - 1);
if (TrailingBytes)
Header.SizeOrUnusedBytes = PageSize - TrailingBytes;
void *Ptr = reinterpret_cast<void *>(UserPtr);
Chunk::storeHeader(Ptr, &Header);
if (SCUDO_CAN_USE_HOOKS && &__sanitizer_malloc_hook)
__sanitizer_malloc_hook(Ptr, Size);
return Ptr;
// Place a chunk in the quarantine or directly deallocate it in the event of
// a zero-sized quarantine, or if the size of the chunk is greater than the
// quarantine chunk size threshold.
void quarantineOrDeallocateChunk(void *Ptr, UnpackedHeader *Header,
uptr Size) {
const bool BypassQuarantine = (Quarantine.GetCacheSize() == 0) ||
(Size > QuarantineChunksUpToSize);
if (BypassQuarantine) {
void *BackendPtr = Chunk::getBackendPtr(Ptr, Header);
if (Header->ClassId) {
bool UnlockRequired;
ScudoTSD *TSD = getTSDAndLock(&UnlockRequired);
getBackend().deallocatePrimary(&TSD->Cache, BackendPtr,
if (UnlockRequired)
} else {
} else {
// If a small memory amount was allocated with a larger alignment, we want
// to take that into account. Otherwise the Quarantine would be filled
// with tiny chunks, taking a lot of VA memory. This is an approximation
// of the usable size, that allows us to not call
// GetActuallyAllocatedSize.
const uptr EstimatedSize = Size + (Header->Offset << MinAlignmentLog);
UnpackedHeader NewHeader = *Header;
NewHeader.State = ChunkQuarantine;
Chunk::compareExchangeHeader(Ptr, &NewHeader, Header);
bool UnlockRequired;
ScudoTSD *TSD = getTSDAndLock(&UnlockRequired);
Quarantine.Put(getQuarantineCache(TSD), QuarantineCallback(&TSD->Cache),
Ptr, EstimatedSize);
if (UnlockRequired)
// Deallocates a Chunk, which means either adding it to the quarantine or
// directly returning it to the backend if criteria are met.
void deallocate(void *Ptr, uptr DeleteSize, uptr DeleteAlignment,
AllocType Type) {
// For a deallocation, we only ensure minimal initialization, meaning thread
// local data will be left uninitialized for now (when using ELF TLS). The
// fallback cache will be used instead. This is a workaround for a situation
// where the only heap operation performed in a thread would be a free past
// the TLS destructors, ending up in initialized thread specific data never
// being destroyed properly. Any other heap operation will do a full init.
if (SCUDO_CAN_USE_HOOKS && &__sanitizer_free_hook)
if (UNLIKELY(!Ptr))
if (UNLIKELY(!Chunk::isAligned(Ptr)))
dieWithMessage("misaligned pointer when deallocating address %p\n", Ptr);
UnpackedHeader Header;
Chunk::loadHeader(Ptr, &Header);
if (UNLIKELY(Header.State != ChunkAllocated))
dieWithMessage("invalid chunk state when deallocating address %p\n", Ptr);
if (DeallocationTypeMismatch) {
// The deallocation type has to match the allocation one.
if (Header.AllocType != Type) {
// With the exception of memalign'd Chunks, that can be still be free'd.
if (Header.AllocType != FromMemalign || Type != FromMalloc)
dieWithMessage("allocation type mismatch when deallocating address "
"%p\n", Ptr);
const uptr Size = Chunk::getSize(Ptr, &Header);
if (DeleteSizeMismatch) {
if (DeleteSize && DeleteSize != Size)
dieWithMessage("invalid sized delete when deallocating address %p\n",
(void)DeleteAlignment; // TODO(kostyak): verify that the alignment matches.
quarantineOrDeallocateChunk(Ptr, &Header, Size);
// Reallocates a chunk. We can save on a new allocation if the new requested
// size still fits in the chunk.
void *reallocate(void *OldPtr, uptr NewSize) {
if (UNLIKELY(!Chunk::isAligned(OldPtr)))
dieWithMessage("misaligned address when reallocating address %p\n",
UnpackedHeader OldHeader;
Chunk::loadHeader(OldPtr, &OldHeader);
if (UNLIKELY(OldHeader.State != ChunkAllocated))
dieWithMessage("invalid chunk state when reallocating address %p\n",
if (DeallocationTypeMismatch) {
if (UNLIKELY(OldHeader.AllocType != FromMalloc))
dieWithMessage("allocation type mismatch when reallocating address "
"%p\n", OldPtr);
const uptr UsableSize = Chunk::getUsableSize(OldPtr, &OldHeader);
// The new size still fits in the current chunk, and the size difference
// is reasonable.
if (NewSize <= UsableSize &&
(UsableSize - NewSize) < (SizeClassMap::kMaxSize / 2)) {
UnpackedHeader NewHeader = OldHeader;
NewHeader.SizeOrUnusedBytes =
OldHeader.ClassId ? NewSize : UsableSize - NewSize;
Chunk::compareExchangeHeader(OldPtr, &NewHeader, &OldHeader);
return OldPtr;
// Otherwise, we have to allocate a new chunk and copy the contents of the
// old one.
void *NewPtr = allocate(NewSize, MinAlignment, FromMalloc);
if (NewPtr) {
const uptr OldSize = OldHeader.ClassId ? OldHeader.SizeOrUnusedBytes :
UsableSize - OldHeader.SizeOrUnusedBytes;
memcpy(NewPtr, OldPtr, Min(NewSize, UsableSize));
quarantineOrDeallocateChunk(OldPtr, &OldHeader, OldSize);
return NewPtr;
// Helper function that returns the actual usable size of a chunk.
uptr getUsableSize(const void *Ptr) {
if (UNLIKELY(!Ptr))
return 0;
UnpackedHeader Header;
Chunk::loadHeader(Ptr, &Header);
// Getting the usable size of a chunk only makes sense if it's allocated.
if (UNLIKELY(Header.State != ChunkAllocated))
dieWithMessage("invalid chunk state when sizing address %p\n", Ptr);
return Chunk::getUsableSize(Ptr, &Header);
void *calloc(uptr NMemB, uptr Size) {
if (UNLIKELY(CheckForCallocOverflow(NMemB, Size))) {
if (AllocatorMayReturnNull())
return nullptr;
reportCallocOverflow(NMemB, Size);
return allocate(NMemB * Size, MinAlignment, FromMalloc, true);
void commitBack(ScudoTSD *TSD) {
Quarantine.Drain(getQuarantineCache(TSD), QuarantineCallback(&TSD->Cache));
uptr getStats(AllocatorStat StatType) {
uptr stats[AllocatorStatCount];
return stats[StatType];
bool canReturnNull() {
return AllocatorMayReturnNull();
void setRssLimit(uptr LimitMb, bool HardLimit) {
if (HardLimit)
HardRssLimitMb = LimitMb;
SoftRssLimitMb = LimitMb;
CheckRssLimit = HardRssLimitMb || SoftRssLimitMb;
void printStats() {
NOINLINE void Allocator::performSanityChecks() {
// Verify that the header offset field can hold the maximum offset. In the
// case of the Secondary allocator, it takes care of alignment and the
// offset will always be 0. In the case of the Primary, the worst case
// scenario happens in the last size class, when the backend allocation
// would already be aligned on the requested alignment, which would happen
// to be the maximum alignment that would fit in that size class. As a
// result, the maximum offset will be at most the maximum alignment for the
// last size class minus the header size, in multiples of MinAlignment.
UnpackedHeader Header = {};
const uptr MaxPrimaryAlignment =
1 << MostSignificantSetBitIndex(SizeClassMap::kMaxSize - MinAlignment);
const uptr MaxOffset =
(MaxPrimaryAlignment - Chunk::getHeaderSize()) >> MinAlignmentLog;
Header.Offset = MaxOffset;
if (Header.Offset != MaxOffset)
dieWithMessage("maximum possible offset doesn't fit in header\n");
// Verify that we can fit the maximum size or amount of unused bytes in the
// header. Given that the Secondary fits the allocation to a page, the worst
// case scenario happens in the Primary. It will depend on the second to
// last and last class sizes, as well as the dynamic base for the Primary.
// The following is an over-approximation that works for our needs.
const uptr MaxSizeOrUnusedBytes = SizeClassMap::kMaxSize - 1;
Header.SizeOrUnusedBytes = MaxSizeOrUnusedBytes;
if (Header.SizeOrUnusedBytes != MaxSizeOrUnusedBytes)
dieWithMessage("maximum possible unused bytes doesn't fit in header\n");
const uptr LargestClassId = SizeClassMap::kLargestClassID;
Header.ClassId = LargestClassId;
if (Header.ClassId != LargestClassId)
dieWithMessage("largest class ID doesn't fit in header\n");
// Opportunistic RSS limit check. This will update the RSS limit status, if
// it can, every 100ms, otherwise it will just return the current one.
NOINLINE bool Allocator::isRssLimitExceeded() {
u64 LastCheck = atomic_load_relaxed(&RssLastCheckedAtNS);
const u64 CurrentCheck = MonotonicNanoTime();
if (LIKELY(CurrentCheck < LastCheck + (100ULL * 1000000ULL)))
return atomic_load_relaxed(&RssLimitExceeded);
if (!atomic_compare_exchange_weak(&RssLastCheckedAtNS, &LastCheck,
CurrentCheck, memory_order_relaxed))
return atomic_load_relaxed(&RssLimitExceeded);
// TODO(kostyak): We currently use sanitizer_common's GetRSS which reads the
// RSS from /proc/self/statm by default. We might want to
// call getrusage directly, even if it's less accurate.
const uptr CurrentRssMb = GetRSS() >> 20;
if (HardRssLimitMb && UNLIKELY(HardRssLimitMb < CurrentRssMb))
dieWithMessage("hard RSS limit exhausted (%zdMb vs %zdMb)\n",
HardRssLimitMb, CurrentRssMb);
if (SoftRssLimitMb) {
if (atomic_load_relaxed(&RssLimitExceeded)) {
if (CurrentRssMb <= SoftRssLimitMb)
atomic_store_relaxed(&RssLimitExceeded, false);
} else {
if (CurrentRssMb > SoftRssLimitMb) {
atomic_store_relaxed(&RssLimitExceeded, true);
Printf("Scudo INFO: soft RSS limit exhausted (%zdMb vs %zdMb)\n",
SoftRssLimitMb, CurrentRssMb);
return atomic_load_relaxed(&RssLimitExceeded);
static Allocator Instance(LINKER_INITIALIZED);
static BackendT &getBackend() {
return Instance.Backend;
void initScudo() {
void ScudoTSD::init() {
memset(QuarantineCachePlaceHolder, 0, sizeof(QuarantineCachePlaceHolder));
void ScudoTSD::commitBack() {
void *scudoAllocate(uptr Size, uptr Alignment, AllocType Type) {
if (Alignment && UNLIKELY(!IsPowerOfTwo(Alignment))) {
errno = EINVAL;
if (Instance.canReturnNull())
return nullptr;
return SetErrnoOnNull(Instance.allocate(Size, Alignment, Type));
void scudoDeallocate(void *Ptr, uptr Size, uptr Alignment, AllocType Type) {
Instance.deallocate(Ptr, Size, Alignment, Type);
void *scudoRealloc(void *Ptr, uptr Size) {
if (!Ptr)
return SetErrnoOnNull(Instance.allocate(Size, MinAlignment, FromMalloc));
if (Size == 0) {
Instance.deallocate(Ptr, 0, 0, FromMalloc);
return nullptr;
return SetErrnoOnNull(Instance.reallocate(Ptr, Size));
void *scudoCalloc(uptr NMemB, uptr Size) {
return SetErrnoOnNull(Instance.calloc(NMemB, Size));
void *scudoValloc(uptr Size) {
return SetErrnoOnNull(
Instance.allocate(Size, GetPageSizeCached(), FromMemalign));
void *scudoPvalloc(uptr Size) {
uptr PageSize = GetPageSizeCached();
if (UNLIKELY(CheckForPvallocOverflow(Size, PageSize))) {
errno = ENOMEM;
if (Instance.canReturnNull())
return nullptr;
// pvalloc(0) should allocate one page.
Size = Size ? RoundUpTo(Size, PageSize) : PageSize;
return SetErrnoOnNull(Instance.allocate(Size, PageSize, FromMemalign));
int scudoPosixMemalign(void **MemPtr, uptr Alignment, uptr Size) {
if (UNLIKELY(!CheckPosixMemalignAlignment(Alignment))) {
if (!Instance.canReturnNull())
return EINVAL;
void *Ptr = Instance.allocate(Size, Alignment, FromMemalign);
if (UNLIKELY(!Ptr))
return ENOMEM;
*MemPtr = Ptr;
return 0;
void *scudoAlignedAlloc(uptr Alignment, uptr Size) {
if (UNLIKELY(!CheckAlignedAllocAlignmentAndSize(Alignment, Size))) {
errno = EINVAL;
if (Instance.canReturnNull())
return nullptr;
reportInvalidAlignedAllocAlignment(Size, Alignment);
return SetErrnoOnNull(Instance.allocate(Size, Alignment, FromMalloc));
uptr scudoMallocUsableSize(void *Ptr) {
return Instance.getUsableSize(Ptr);
} // namespace __scudo
using namespace __scudo;
// MallocExtension helper functions
uptr __sanitizer_get_current_allocated_bytes() {
return Instance.getStats(AllocatorStatAllocated);
uptr __sanitizer_get_heap_size() {
return Instance.getStats(AllocatorStatMapped);
uptr __sanitizer_get_free_bytes() {
return 1;
uptr __sanitizer_get_unmapped_bytes() {
return 1;
uptr __sanitizer_get_estimated_allocated_size(uptr Size) {
return Size;
int __sanitizer_get_ownership(const void *Ptr) {
return Instance.isValidPointer(Ptr);
uptr __sanitizer_get_allocated_size(const void *Ptr) {
return Instance.getUsableSize(Ptr);
SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_malloc_hook,
void *Ptr, uptr Size) {
SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_free_hook, void *Ptr) {
// Interface functions
void __scudo_set_rss_limit(uptr LimitMb, s32 HardLimit) {
Instance.setRssLimit(LimitMb, !!HardLimit);
void __scudo_print_stats() {