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| //===-- release.h -----------------------------------------------*- 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
//
//===----------------------------------------------------------------------===//
#ifndef SCUDO_RELEASE_H_
#define SCUDO_RELEASE_H_
#include "common.h"
#include "list.h"
namespace scudo {
class ReleaseRecorder {
public:
ReleaseRecorder(uptr BaseAddress, MapPlatformData *Data = nullptr)
: BaseAddress(BaseAddress), Data(Data) {}
uptr getReleasedRangesCount() const { return ReleasedRangesCount; }
uptr getReleasedBytes() const { return ReleasedBytes; }
// Releases [From, To) range of pages back to OS.
void releasePageRangeToOS(uptr From, uptr To) {
const uptr Size = To - From;
releasePagesToOS(BaseAddress, From, Size, Data);
ReleasedRangesCount++;
ReleasedBytes += Size;
}
private:
uptr ReleasedRangesCount = 0;
uptr ReleasedBytes = 0;
uptr BaseAddress = 0;
MapPlatformData *Data = nullptr;
};
// A packed array of Counters. Each counter occupies 2^N bits, enough to store
// counter's MaxValue. Ctor will try to allocate the required Buffer via map()
// and the caller is expected to check whether the initialization was successful
// by checking isAllocated() result. For the performance sake, none of the
// accessors check the validity of the arguments, It is assumed that Index is
// always in [0, N) range and the value is not incremented past MaxValue.
class PackedCounterArray {
public:
PackedCounterArray(uptr NumCounters, uptr MaxValue) : N(NumCounters) {
CHECK_GT(NumCounters, 0);
CHECK_GT(MaxValue, 0);
constexpr uptr MaxCounterBits = sizeof(*Buffer) * 8UL;
// Rounding counter storage size up to the power of two allows for using
// bit shifts calculating particular counter's Index and offset.
const uptr CounterSizeBits =
roundUpToPowerOfTwo(getMostSignificantSetBitIndex(MaxValue) + 1);
CHECK_LE(CounterSizeBits, MaxCounterBits);
CounterSizeBitsLog = getLog2(CounterSizeBits);
CounterMask = ~(static_cast<uptr>(0)) >> (MaxCounterBits - CounterSizeBits);
const uptr PackingRatio = MaxCounterBits >> CounterSizeBitsLog;
CHECK_GT(PackingRatio, 0);
PackingRatioLog = getLog2(PackingRatio);
BitOffsetMask = PackingRatio - 1;
BufferSize = (roundUpTo(N, static_cast<uptr>(1U) << PackingRatioLog) >>
PackingRatioLog) *
sizeof(*Buffer);
Buffer = reinterpret_cast<uptr *>(
map(nullptr, BufferSize, "scudo:counters", MAP_ALLOWNOMEM));
}
~PackedCounterArray() {
if (isAllocated())
unmap(reinterpret_cast<void *>(Buffer), BufferSize);
}
bool isAllocated() const { return !!Buffer; }
uptr getCount() const { return N; }
uptr get(uptr I) const {
DCHECK_LT(I, N);
const uptr Index = I >> PackingRatioLog;
const uptr BitOffset = (I & BitOffsetMask) << CounterSizeBitsLog;
return (Buffer[Index] >> BitOffset) & CounterMask;
}
void inc(uptr I) const {
DCHECK_LT(get(I), CounterMask);
const uptr Index = I >> PackingRatioLog;
const uptr BitOffset = (I & BitOffsetMask) << CounterSizeBitsLog;
DCHECK_LT(BitOffset, SCUDO_WORDSIZE);
Buffer[Index] += static_cast<uptr>(1U) << BitOffset;
}
void incRange(uptr From, uptr To) const {
DCHECK_LE(From, To);
for (uptr I = From; I <= To; I++)
inc(I);
}
uptr getBufferSize() const { return BufferSize; }
private:
const uptr N;
uptr CounterSizeBitsLog;
uptr CounterMask;
uptr PackingRatioLog;
uptr BitOffsetMask;
uptr BufferSize;
uptr *Buffer;
};
template <class ReleaseRecorderT> class FreePagesRangeTracker {
public:
explicit FreePagesRangeTracker(ReleaseRecorderT *Recorder)
: Recorder(Recorder), PageSizeLog(getLog2(getPageSizeCached())) {}
void processNextPage(bool Freed) {
if (Freed) {
if (!InRange) {
CurrentRangeStatePage = CurrentPage;
InRange = true;
}
} else {
closeOpenedRange();
}
CurrentPage++;
}
void finish() { closeOpenedRange(); }
private:
void closeOpenedRange() {
if (InRange) {
Recorder->releasePageRangeToOS((CurrentRangeStatePage << PageSizeLog),
(CurrentPage << PageSizeLog));
InRange = false;
}
}
ReleaseRecorderT *const Recorder;
const uptr PageSizeLog;
bool InRange = false;
uptr CurrentPage = 0;
uptr CurrentRangeStatePage = 0;
};
template <class TransferBatchT, class ReleaseRecorderT>
NOINLINE void
releaseFreeMemoryToOS(const IntrusiveList<TransferBatchT> &FreeList, uptr Base,
uptr AllocatedPagesCount, uptr BlockSize,
ReleaseRecorderT *Recorder) {
const uptr PageSize = getPageSizeCached();
// Figure out the number of chunks per page and whether we can take a fast
// path (the number of chunks per page is the same for all pages).
uptr FullPagesBlockCountMax;
bool SameBlockCountPerPage;
if (BlockSize <= PageSize) {
if (PageSize % BlockSize == 0) {
// Same number of chunks per page, no cross overs.
FullPagesBlockCountMax = PageSize / BlockSize;
SameBlockCountPerPage = true;
} else if (BlockSize % (PageSize % BlockSize) == 0) {
// Some chunks are crossing page boundaries, which means that the page
// contains one or two partial chunks, but all pages contain the same
// number of chunks.
FullPagesBlockCountMax = PageSize / BlockSize + 1;
SameBlockCountPerPage = true;
} else {
// Some chunks are crossing page boundaries, which means that the page
// contains one or two partial chunks.
FullPagesBlockCountMax = PageSize / BlockSize + 2;
SameBlockCountPerPage = false;
}
} else {
if (BlockSize % PageSize == 0) {
// One chunk covers multiple pages, no cross overs.
FullPagesBlockCountMax = 1;
SameBlockCountPerPage = true;
} else {
// One chunk covers multiple pages, Some chunks are crossing page
// boundaries. Some pages contain one chunk, some contain two.
FullPagesBlockCountMax = 2;
SameBlockCountPerPage = false;
}
}
PackedCounterArray Counters(AllocatedPagesCount, FullPagesBlockCountMax);
if (!Counters.isAllocated())
return;
const uptr PageSizeLog = getLog2(PageSize);
const uptr End = Base + AllocatedPagesCount * PageSize;
// Iterate over free chunks and count how many free chunks affect each
// allocated page.
if (BlockSize <= PageSize && PageSize % BlockSize == 0) {
// Each chunk affects one page only.
for (const auto &It : FreeList) {
for (u32 I = 0; I < It.getCount(); I++) {
const uptr P = reinterpret_cast<uptr>(It.get(I));
if (P >= Base && P < End)
Counters.inc((P - Base) >> PageSizeLog);
}
}
} else {
// In all other cases chunks might affect more than one page.
for (const auto &It : FreeList) {
for (u32 I = 0; I < It.getCount(); I++) {
const uptr P = reinterpret_cast<uptr>(It.get(I));
if (P >= Base && P < End)
Counters.incRange((P - Base) >> PageSizeLog,
(P - Base + BlockSize - 1) >> PageSizeLog);
}
}
}
// Iterate over pages detecting ranges of pages with chunk Counters equal
// to the expected number of chunks for the particular page.
FreePagesRangeTracker<ReleaseRecorderT> RangeTracker(Recorder);
if (SameBlockCountPerPage) {
// Fast path, every page has the same number of chunks affecting it.
for (uptr I = 0; I < Counters.getCount(); I++)
RangeTracker.processNextPage(Counters.get(I) == FullPagesBlockCountMax);
} else {
// Slow path, go through the pages keeping count how many chunks affect
// each page.
const uptr Pn = BlockSize < PageSize ? PageSize / BlockSize : 1;
const uptr Pnc = Pn * BlockSize;
// The idea is to increment the current page pointer by the first chunk
// size, middle portion size (the portion of the page covered by chunks
// except the first and the last one) and then the last chunk size, adding
// up the number of chunks on the current page and checking on every step
// whether the page boundary was crossed.
uptr PrevPageBoundary = 0;
uptr CurrentBoundary = 0;
for (uptr I = 0; I < Counters.getCount(); I++) {
const uptr PageBoundary = PrevPageBoundary + PageSize;
uptr BlocksPerPage = Pn;
if (CurrentBoundary < PageBoundary) {
if (CurrentBoundary > PrevPageBoundary)
BlocksPerPage++;
CurrentBoundary += Pnc;
if (CurrentBoundary < PageBoundary) {
BlocksPerPage++;
CurrentBoundary += BlockSize;
}
}
PrevPageBoundary = PageBoundary;
RangeTracker.processNextPage(Counters.get(I) == BlocksPerPage);
}
}
RangeTracker.finish();
}
} // namespace scudo
#endif // SCUDO_RELEASE_H_
|