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Copy pathSecureARM64EHashPins.cpp
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SecureARM64EHashPins.cpp
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292 lines (232 loc) · 9.06 KB
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/*
* Copyright (C) 2022 Apple Inc. All rights reserved.
*
* 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/Condition.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
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