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//===-- scudo_allocator_secondary.h -----------------------------*- C++ -*-===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
///
/// Scudo Secondary Allocator.
/// This services allocation that are too large to be serviced by the Primary
/// Allocator. It is directly backed by the memory mapping functions of the
/// operating system.
///
//===----------------------------------------------------------------------===//
#ifndef SCUDO_ALLOCATOR_SECONDARY_H_
#define SCUDO_ALLOCATOR_SECONDARY_H_
#ifndef SCUDO_ALLOCATOR_H_
# error "This file must be included inside scudo_allocator.h."
#endif
class ScudoLargeMmapAllocator {
public:
void Init(bool AllocatorMayReturnNull) {
PageSize = GetPageSizeCached();
atomic_store(&MayReturnNull, AllocatorMayReturnNull, memory_order_relaxed);
}
void *Allocate(AllocatorStats *Stats, uptr Size, uptr Alignment) {
// The Scudo frontend prevents us from allocating more than
// MaxAllowedMallocSize, so integer overflow checks would be superfluous.
uptr HeadersSize = sizeof(SecondaryHeader) + ChunkHeaderSize;
uptr MapSize = RoundUpTo(Size + sizeof(SecondaryHeader), PageSize);
// Account for 2 guard pages, one before and one after the chunk.
MapSize += 2 * PageSize;
// Adding an extra Alignment is not required, it was done by the frontend.
uptr MapBeg = reinterpret_cast<uptr>(MmapNoAccess(MapSize));
if (MapBeg == ~static_cast<uptr>(0))
return ReturnNullOrDieOnOOM();
// A page-aligned pointer is assumed after that, so check it now.
CHECK(IsAligned(MapBeg, PageSize));
uptr MapEnd = MapBeg + MapSize;
uptr UserBeg = MapBeg + PageSize + HeadersSize;
// In the event of larger alignments, we will attempt to fit the mmap area
// better and unmap extraneous memory. This will also ensure that the
// offset field of the header stays small (it will always be 0).
if (Alignment > MinAlignment) {
if (UserBeg & (Alignment - 1))
UserBeg += Alignment - (UserBeg & (Alignment - 1));
CHECK_GE(UserBeg, MapBeg);
uptr NewMapBeg = UserBeg - HeadersSize;
NewMapBeg = (NewMapBeg & ~(PageSize - 1)) - PageSize;
CHECK_GE(NewMapBeg, MapBeg);
uptr NewMapSize = MapEnd - NewMapBeg;
uptr Diff = NewMapBeg - MapBeg;
// Unmap the extra memory if it's large enough.
if (Diff > PageSize)
UnmapOrDie(reinterpret_cast<void *>(MapBeg), Diff);
MapBeg = NewMapBeg;
MapSize = NewMapSize;
}
uptr UserEnd = UserBeg - ChunkHeaderSize + Size;
// For larger alignments, Alignment was added by the frontend to Size.
if (Alignment > MinAlignment)
UserEnd -= Alignment;
CHECK_LE(UserEnd, MapEnd - PageSize);
CHECK_EQ(MapBeg + PageSize, reinterpret_cast<uptr>(
MmapFixedOrDie(MapBeg + PageSize, MapSize - 2 * PageSize)));
uptr Ptr = UserBeg - ChunkHeaderSize;
SecondaryHeader *Header = getHeader(Ptr);
Header->MapBeg = MapBeg;
Header->MapSize = MapSize;
Stats->Add(AllocatorStatAllocated, MapSize - 2 * PageSize);
Stats->Add(AllocatorStatMapped, MapSize - 2 * PageSize);
CHECK(IsAligned(UserBeg, Alignment));
return reinterpret_cast<void *>(UserBeg);
}
void *ReturnNullOrDieOnBadRequest() {
if (atomic_load(&MayReturnNull, memory_order_acquire))
return nullptr;
ReportAllocatorCannotReturnNull(false);
}
void *ReturnNullOrDieOnOOM() {
if (atomic_load(&MayReturnNull, memory_order_acquire))
return nullptr;
ReportAllocatorCannotReturnNull(true);
}
void SetMayReturnNull(bool AllocatorMayReturnNull) {
atomic_store(&MayReturnNull, AllocatorMayReturnNull, memory_order_release);
}
void Deallocate(AllocatorStats *Stats, void *Ptr) {
SecondaryHeader *Header = getHeader(Ptr);
Stats->Sub(AllocatorStatAllocated, Header->MapSize);
Stats->Sub(AllocatorStatMapped, Header->MapSize);
UnmapOrDie(reinterpret_cast<void *>(Header->MapBeg), Header->MapSize);
}
uptr TotalMemoryUsed() {
UNIMPLEMENTED();
}
bool PointerIsMine(const void *Ptr) {
UNIMPLEMENTED();
}
uptr GetActuallyAllocatedSize(void *Ptr) {
SecondaryHeader *Header = getHeader(Ptr);
// Deduct PageSize as MapEnd includes the trailing guard page.
uptr MapEnd = Header->MapBeg + Header->MapSize - PageSize;
return MapEnd - reinterpret_cast<uptr>(Ptr);
}
void *GetMetaData(const void *Ptr) {
UNIMPLEMENTED();
}
void *GetBlockBegin(const void *Ptr) {
UNIMPLEMENTED();
}
void *GetBlockBeginFastLocked(void *Ptr) {
UNIMPLEMENTED();
}
void PrintStats() {
UNIMPLEMENTED();
}
void ForceLock() {
UNIMPLEMENTED();
}
void ForceUnlock() {
UNIMPLEMENTED();
}
void ForEachChunk(ForEachChunkCallback Callback, void *Arg) {
UNIMPLEMENTED();
}
private:
// A Secondary allocated chunk header contains the base of the mapping and
// its size. Currently, the base is always a page before the header, but
// we might want to extend that number in the future based on the size of
// the allocation.
struct SecondaryHeader {
uptr MapBeg;
uptr MapSize;
};
// Check that sizeof(SecondaryHeader) is a multiple of 16.
COMPILER_CHECK((sizeof(SecondaryHeader) & 0xf) == 0);
SecondaryHeader *getHeader(uptr Ptr) {
return reinterpret_cast<SecondaryHeader*>(Ptr - sizeof(SecondaryHeader));
}
SecondaryHeader *getHeader(const void *Ptr) {
return getHeader(reinterpret_cast<uptr>(Ptr));
}
uptr PageSize;
atomic_uint8_t MayReturnNull;
};
#endif // SCUDO_ALLOCATOR_SECONDARY_H_
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