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//===-- secondary.cpp -------------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "secondary.h"
#include "string_utils.h"
namespace scudo {
// As with the Primary, the size passed to this function includes any desired
// alignment, so that the frontend can align the user allocation. The hint
// parameter allows us to unmap spurious memory when dealing with larger
// (greater than a page) alignments on 32-bit platforms.
// Due to the sparsity of address space available on those platforms, requesting
// an allocation from the Secondary with a large alignment would end up wasting
// VA space (even though we are not committing the whole thing), hence the need
// to trim off some of the reserved space.
// For allocations requested with an alignment greater than or equal to a page,
// the committed memory will amount to something close to Size - AlignmentHint
// (pending rounding and headers).
void *MapAllocator::allocate(uptr Size, uptr AlignmentHint, uptr *BlockEnd) {
DCHECK_GT(Size, AlignmentHint);
const uptr PageSize = getPageSizeCached();
const uptr MapSize =
roundUpTo(Size + LargeBlock::getHeaderSize(), PageSize) + 2 * PageSize;
MapPlatformData Data = {};
uptr MapBase =
reinterpret_cast<uptr>(map(nullptr, MapSize, "scudo:secondary",
MAP_NOACCESS | MAP_ALLOWNOMEM, &Data));
if (UNLIKELY(!MapBase))
return nullptr;
uptr CommitBase = MapBase + PageSize;
uptr MapEnd = MapBase + MapSize;
// In the unlikely event of alignments larger than a page, adjust the amount
// of memory we want to commit, and trim the extra memory.
if (UNLIKELY(AlignmentHint >= PageSize)) {
// For alignments greater than or equal to a page, the user pointer (eg: the
// pointer that is returned by the C or C++ allocation APIs) ends up on a
// page boundary , and our headers will live in the preceding page.
CommitBase = roundUpTo(MapBase + PageSize + 1, AlignmentHint) - PageSize;
const uptr NewMapBase = CommitBase - PageSize;
DCHECK_GE(NewMapBase, MapBase);
// We only trim the extra memory on 32-bit platforms: 64-bit platforms
// are less constrained memory wise, and that saves us two syscalls.
if (SCUDO_WORDSIZE == 32U && NewMapBase != MapBase) {
unmap(reinterpret_cast<void *>(MapBase), NewMapBase - MapBase, 0, &Data);
MapBase = NewMapBase;
}
const uptr NewMapEnd = CommitBase + PageSize +
roundUpTo((Size - AlignmentHint), PageSize) +
PageSize;
DCHECK_LE(NewMapEnd, MapEnd);
if (SCUDO_WORDSIZE == 32U && NewMapEnd != MapEnd) {
unmap(reinterpret_cast<void *>(NewMapEnd), MapEnd - NewMapEnd, 0, &Data);
MapEnd = NewMapEnd;
}
}
const uptr CommitSize = MapEnd - PageSize - CommitBase;
const uptr Ptr =
reinterpret_cast<uptr>(map(reinterpret_cast<void *>(CommitBase),
CommitSize, "scudo:secondary", 0, &Data));
LargeBlock::Header *H = reinterpret_cast<LargeBlock::Header *>(Ptr);
H->MapBase = MapBase;
H->MapSize = MapEnd - MapBase;
H->BlockEnd = CommitBase + CommitSize;
H->Data = Data;
{
ScopedLock L(Mutex);
if (LIKELY(Tail)) {
Tail->Next = H;
H->Prev = Tail;
}
Tail = H;
AllocatedBytes += CommitSize;
if (LargestSize < CommitSize)
LargestSize = CommitSize;
NumberOfAllocs++;
Stats.add(StatAllocated, CommitSize);
Stats.add(StatMapped, H->MapSize);
}
if (BlockEnd)
*BlockEnd = CommitBase + CommitSize;
return reinterpret_cast<void *>(Ptr + LargeBlock::getHeaderSize());
}
void MapAllocator::deallocate(void *Ptr) {
LargeBlock::Header *H = LargeBlock::getHeader(Ptr);
{
ScopedLock L(Mutex);
LargeBlock::Header *Prev = H->Prev;
LargeBlock::Header *Next = H->Next;
if (Prev) {
CHECK_EQ(Prev->Next, H);
Prev->Next = Next;
}
if (Next) {
CHECK_EQ(Next->Prev, H);
Next->Prev = Prev;
}
if (UNLIKELY(Tail == H)) {
CHECK(!Next);
Tail = Prev;
} else {
CHECK(Next);
}
const uptr CommitSize = H->BlockEnd - reinterpret_cast<uptr>(H);
FreedBytes += CommitSize;
NumberOfFrees++;
Stats.sub(StatAllocated, CommitSize);
Stats.sub(StatMapped, H->MapSize);
}
void *Addr = reinterpret_cast<void *>(H->MapBase);
const uptr Size = H->MapSize;
MapPlatformData Data;
Data = H->Data;
unmap(Addr, Size, UNMAP_ALL, &Data);
}
void MapAllocator::printStats() const {
Printf("Stats: MapAllocator: allocated %zu times (%zuK), freed %zu times "
"(%zuK), remains %zu (%zuK) max %zuM\n",
NumberOfAllocs, AllocatedBytes >> 10, NumberOfFrees, FreedBytes >> 10,
NumberOfAllocs - NumberOfFrees, (AllocatedBytes - FreedBytes) >> 10,
LargestSize >> 20);
}
} // namespace scudo
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