WebKit/Source/JavaScriptCore/assembler/SecureARM64EHashPins.cpp at main · WebKit/WebKit · GitHub

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* Redistribution and use in source and binary forms, with or without

* modification, are permitted provided that the following conditions

* are met:

* 1. Redistributions of source code must retain the above copyright

* notice, this list of conditions and the following disclaimer.

* 2. Redistributions in binary form must reproduce the above copyright

* notice, this list of conditions and the following disclaimer in the

* documentation and/or other materials provided with the distribution.

* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY

* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE

* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR

* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR

* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,

* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR

* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY

* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT

* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE

* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

#include "config.h"

#include "SecureARM64EHashPins.h"

#include "ExecutableAllocator.h"

#include "FastJITPermissions.h"

#include "SecureARM64EHashPinsInlines.h"

#include <wtf/Lock.h>

namespace JSC {

#if CPU(ARM64E) && ENABLE(JIT)

struct WriteToJITRegionScope {

ALWAYS_INLINE WriteToJITRegionScope()

{

threadSelfRestrict<MemoryRestriction::kRwxToRw>();

}

ALWAYS_INLINE ~WriteToJITRegionScope()

{

threadSelfRestrict<MemoryRestriction::kRwxToRx>();

}

};

struct ValidateNonReentrancyScope {

ALWAYS_INLINE ValidateNonReentrancyScope(SecureARM64EHashPins::Metadata* metadata)

: m_metadata(metadata)

{

uint32_t validateNonReentrancy = m_metadata->assertNotReentrant.exchange(1, std::memory_order_seq_cst);

RELEASE_ASSERT(!validateNonReentrancy);

}

ALWAYS_INLINE ~ValidateNonReentrancyScope()

{

uint32_t validateNonReentrancy = m_metadata->assertNotReentrant.exchange(0, std::memory_order_seq_cst);

RELEASE_ASSERT(validateNonReentrancy == 1);

}

SecureARM64EHashPins::Metadata* m_metadata;

};

// This class is allocated once per process, so static lock is ok.

static Lock hashPinsLock;

WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN

ALWAYS_INLINE static ExecutableMemoryHandle::MemoryPtr allocateInExecutableMemory(size_t size)

{

ExecutableMemoryHandle* handle = ExecutableAllocator::singleton().allocate(size, JITCompilationMustSucceed).leakRef();

RELEASE_ASSERT(handle);

void* memory = handle->start().untaggedPtr<char*>();

RELEASE_ASSERT(isJITPC(memory) && isJITPC(std::bit_cast<char*>(memory) + size - 1));

return handle->start();

}

WTF_ALLOW_UNSAFE_BUFFER_USAGE_END

ALWAYS_INLINE SecureARM64EHashPins::Page::Page()

{

for (unsigned i = 0; i < numEntriesPerPage; ++i) {

auto& entry = this->entry(i);

entry.pin = 0;

entry.key = 0;

}

static ALWAYS_INLINE void initializePage(const WriteToJITRegionScope&, SecureARM64EHashPins::Page* page)

{

new (page) SecureARM64EHashPins::Page;

}

#define VALIDATE_THIS_VALUE() RELEASE_ASSERT(this == &g_jscConfig.arm64eHashPins)

WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN

ALWAYS_INLINE auto SecureARM64EHashPins::metadata() -> Metadata*

{

VALIDATE_THIS_VALUE();

return std::bit_cast<Metadata*>(m_memory) - 1;

}

void SecureARM64EHashPins::initializeAtStartup()

{

if (!g_jscConfig.useFastJITPermissions)

return;

VALIDATE_THIS_VALUE();

RELEASE_ASSERT(!m_memory);

m_memory = allocateInExecutableMemory(sizeof(Metadata) + Page::allocationSize()).untaggedPtr<char*>() + sizeof(Metadata);

{

WriteToJITRegionScope writeScope;

new (metadata()) Metadata;

initializePage(writeScope, firstPage());

}

WTF_ALLOW_UNSAFE_BUFFER_USAGE_END

bool SecureARM64EHashPins::allocatePinForCurrentThreadImpl(const AbstractLocker&)

{

VALIDATE_THIS_VALUE();

size_t newEntryIndex;

Page* newEntryPage;

bool found = false;

size_t baseIndex = 0;

forEachPage([&] (Page& page) {

size_t bit = page.findClearBit();

if (bit < numEntriesPerPage) {

found = true;

newEntryIndex = baseIndex + bit;

newEntryPage = &page;

return IterationStatus::Done;

}

baseIndex += numEntriesPerPage;

return IterationStatus::Continue;

});

if (!found)

return false;

auto findResult = findFirstEntry();

Entry* preexistingEntry = findResult.entry;

size_t preexistingEntryIndex = findResult.index;

Page* preexistingEntryPage = findResult.page;

{

auto* metadata = this->metadata();

WriteToJITRegionScope writeScope;

ValidateNonReentrancyScope validateNonReentrancy(metadata);

RELEASE_ASSERT(isJITPC(metadata));

uint64_t nextPin = metadata->nextPin.exchangeAdd(1, std::memory_order_seq_cst);

RELEASE_ASSERT(nextPin);

newEntryPage->setIsInUse(newEntryIndex);

if (preexistingEntry && preexistingEntryIndex < newEntryIndex) {

RELEASE_ASSERT(preexistingEntryPage->isInUse(preexistingEntryIndex));

newEntryPage->entry(newEntryIndex) = *preexistingEntry;

newEntryIndex = preexistingEntryIndex;

newEntryPage = preexistingEntryPage;

}

auto& entry = newEntryPage->entry(newEntryIndex);

entry.pin = nextPin;

entry.key = keyForCurrentThread();

}

return true;

}

void SecureARM64EHashPins::allocatePinForCurrentThread()

{

if (!g_jscConfig.useFastJITPermissions)

return;

VALIDATE_THIS_VALUE();

Locker locker { hashPinsLock };

if (allocatePinForCurrentThreadImpl(locker))

return;

// Allocate a new page

{

Page* lastPage = firstPage();

while (lastPage->next)

lastPage = lastPage->next;

RELEASE_ASSERT(!lastPage->next);

auto newPage = allocateInExecutableMemory(Page::allocationSize());

{

WriteToJITRegionScope writeScope;

ValidateNonReentrancyScope validateNonReentrancy(metadata());

initializePage(writeScope, newPage.untaggedPtr<Page*>());

// This can be read from concurrently. Make sure it's in a good state for that to happen.

WTF::storeStoreFence();

lastPage->next = newPage.untaggedPtr<Page*>();

}

bool success = allocatePinForCurrentThreadImpl(locker);

RELEASE_ASSERT(success);

}

void SecureARM64EHashPins::deallocatePinForCurrentThread()

{

if (!g_jscConfig.useFastJITPermissions)

return;

VALIDATE_THIS_VALUE();

Locker locker { hashPinsLock };

auto clear = [] (Entry& entry) {

entry.pin = 0;

entry.key = 0;

};

Page* removalPage;

size_t removalIndex;

{

auto findResult = findFirstEntry();

Entry& entry = *findResult.entry;

removalIndex = findResult.index;

removalPage = findResult.page;

WriteToJITRegionScope writeScope;

ValidateNonReentrancyScope validateNonReentrancy(metadata());

clear(entry);

removalPage->clearIsInUse(removalIndex);

}

// This implementation allows recursive uses of the MacroAssembler, forming a stack

// like data structure. The in use pin (top of the stack) will always be at the lowest

// page and lowest index in the bit vector. So when we deallocate the current top of the

// stack, we need to find the next entry in the stack, and ensure it's at the lowest index.

// So if there are other entries for this current thread, we find the one with the highest

// pin (next top of stack value), and replace it at the index we were using before.

// Allocation also maintains this invariant by always placing the newest entry for

// the current thread at the lowest index.

{

uint64_t key = keyForCurrentThread();

bool found = false;

uint64_t maxPin = 0;

size_t maxIndex = std::numeric_limits<size_t>::max();

Page* maxPage = nullptr;

forEachEntry([&] (Page& page, Entry& entry, size_t index) {

RELEASE_ASSERT(entry.pin);

if (entry.key == key && entry.pin > maxPin) {

found = true;

maxPin = entry.pin;

maxIndex = index;

maxPage = &page;

}

return IterationStatus::Continue;

});

if (found) {

RELEASE_ASSERT(removalIndex < maxIndex);

WriteToJITRegionScope writeScope;

ValidateNonReentrancyScope validateNonReentrancy(metadata());

removalPage->entry(removalIndex) = maxPage->entry(maxIndex);

clear(maxPage->entry(maxIndex));

maxPage->clearIsInUse(maxIndex);

removalPage->setIsInUse(removalIndex);

}

#endif // CPU(ARM64E) && ENABLE(JIT)

} // namespace JSC

WebKit/Source/JavaScriptCore/assembler/SecureARM64EHashPins.cpp at main · WebKit/WebKit · GitHub

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