qv4executableallocator.cpp

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// Copyright (C) 2016 The Qt Company Ltd.

// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only

// Qt-Security score:significant

#include "qv4executableallocator_p.h"

#include <QtQml/private/qv4functiontable_p.h>

#include <wtf/StdLibExtras.h>

#include <wtf/PageAllocation.h>

using namespace QV4;

void *ExecutableAllocator::Allocation::exceptionHandlerStart() const

    return reinterpret_cast<void*>(addr);

size_t ExecutableAllocator::Allocation::exceptionHandlerSize() const

    return QV4::exceptionHandlerSize();

void *ExecutableAllocator::Allocation::memoryStart() const

    return reinterpret_cast<void*>(addr);

void *ExecutableAllocator::Allocation::codeStart() const

    return reinterpret_cast<void*>(addr + exceptionHandlerSize());

void ExecutableAllocator::Allocation::deallocate(ExecutableAllocator *allocator)

    if (isValid())

        allocator->free(this);

    else

        delete this;

ExecutableAllocator::Allocation *ExecutableAllocator::Allocation::split(size_t dividingSize)

    Allocation *remainder = new Allocation;

    if (next)

        next->prev = remainder;

    remainder->next = next;

    next = remainder;

    remainder->prev = this;

    remainder->size = size - dividingSize;

    remainder->free = free;

    remainder->addr = addr + dividingSize;

    size = dividingSize;

    return remainder;

bool ExecutableAllocator::Allocation::mergeNext(ExecutableAllocator *allocator)

    Q_ASSERT(free);

    if (!next || !next->free)

        return false;

    allocator->freeAllocations.remove(size, this);

    allocator->freeAllocations.remove(next->size, next);

    size += next->size;

    Allocation *newNext = next->next;

    delete next;

    next = newNext;

    if (next)

        next->prev = this;

    allocator->freeAllocations.insert(size, this);

    return true;

bool ExecutableAllocator::Allocation::mergePrevious(ExecutableAllocator *allocator)

    Q_ASSERT(free);

    if (!prev || !prev->free)

        return false;

    allocator->freeAllocations.remove(size, this);

    allocator->freeAllocations.remove(prev->size, prev);

    prev->size += size;

    if (next)

        next->prev = prev;

    prev->next = next;

    allocator->freeAllocations.insert(prev->size, prev);

    delete this;

    return true;

ExecutableAllocator::ChunkOfPages::~ChunkOfPages()

    Allocation *alloc = firstAllocation;

    while (alloc) {

        Allocation *next = alloc->next;

        if (alloc->isValid())

            delete alloc;

        alloc = next;

    pages->deallocate();

    delete pages;

bool ExecutableAllocator::ChunkOfPages::contains(Allocation *alloc) const

    Allocation *it = firstAllocation;

    while (it) {

        if (it == alloc)

            return true;

        it = it->next;

    return false;

ExecutableAllocator::ExecutableAllocator()

    = default;

ExecutableAllocator::~ExecutableAllocator()

    for (ChunkOfPages *chunk : std::as_const(chunks)) {

        for (Allocation *allocation = chunk->firstAllocation; allocation; allocation = allocation->next)

            if (!allocation->free)

                allocation->invalidate();

    qDeleteAll(chunks);

ExecutableAllocator::Allocation *ExecutableAllocator::allocate(size_t size)

    QMutexLocker locker(&mutex);

    Allocation *allocation = nullptr;

    // Code is best aligned to 16-byte boundaries.

    size = WTF::roundUpToMultipleOf(16, size + exceptionHandlerSize());

    QMultiMap<size_t, Allocation*>::Iterator it = freeAllocations.lowerBound(size);

    if (it != freeAllocations.end()) {

        allocation = *it;

        freeAllocations.erase(it);

    if (!allocation) {

        ChunkOfPages *chunk = new ChunkOfPages;

        size_t allocSize = WTF::roundUpToMultipleOf(WTF::pageSize(), size);

        chunk->pages = new WTF::PageAllocation(WTF::PageAllocation::allocate(allocSize, OSAllocator::JSJITCodePages));

        chunks.insert(reinterpret_cast<quintptr>(chunk->pages->base()) - 1, chunk);

        allocation = new Allocation;

        allocation->addr = reinterpret_cast<quintptr>(chunk->pages->base());

        allocation->size = allocSize;

        allocation->free = true;

        chunk->firstAllocation = allocation;

    Q_ASSERT(allocation);

    Q_ASSERT(allocation->free);

    allocation->free = false;

    if (allocation->size > size) {

        Allocation *remainder = allocation->split(size);

        remainder->free = true;

        if (!remainder->mergeNext(this))

            freeAllocations.insert(remainder->size, remainder);

    return allocation;

void ExecutableAllocator::free(Allocation *allocation)

    QMutexLocker locker(&mutex);

    Q_ASSERT(allocation);

    allocation->free = true;

    QMap<quintptr, ChunkOfPages*>::Iterator it = chunks.lowerBound(allocation->addr);

    if (it != chunks.begin())

        --it;

    Q_ASSERT(it != chunks.end());

    ChunkOfPages *chunk = *it;

    Q_ASSERT(chunk->contains(allocation));

    bool merged = allocation->mergeNext(this);

    merged |= allocation->mergePrevious(this);

    if (!merged)

        freeAllocations.insert(allocation->size, allocation);

    allocation = nullptr;

    if (!chunk->firstAllocation->next) {

        freeAllocations.remove(chunk->firstAllocation->size, chunk->firstAllocation);

        chunks.erase(it);

        delete chunk;

        return;

ExecutableAllocator::ChunkOfPages *ExecutableAllocator::chunkForAllocation(Allocation *allocation) const

    QMutexLocker locker(&mutex);

    QMap<quintptr, ChunkOfPages*>::ConstIterator it = chunks.lowerBound(allocation->addr);

    if (it != chunks.begin())

        --it;

    if (it == chunks.end())

        return nullptr;

    return *it;