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/*
* Copyright (C) 2017-2020 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 "WasmFaultSignalHandler.h"
#if ENABLE(WEBASSEMBLY)
#include "ExecutableAllocator.h"
#include "JSCellInlines.h"
#include "JSWebAssemblyInstance.h"
#include "LLIntData.h"
#include "MachineContext.h"
#include "NativeCalleeRegistry.h"
#include "WasmCallee.h"
#include "WasmCapabilities.h"
#include "WasmContext.h"
#include "WasmExceptionType.h"
#include "WasmMemory.h"
#include "WasmThunks.h"
#include <wtf/CodePtr.h>
#include <wtf/HashSet.h>
#include <wtf/Lock.h>
#include <wtf/threads/Signals.h>
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
namespace JSC { namespace Wasm {
using WTF::CodePtr;
#if CPU(ARM64E) && HAVE(HARDENED_MACH_EXCEPTIONS)
void* presignedTrampoline { nullptr };
#endif
namespace {
namespace WasmFaultSignalHandlerInternal {
static constexpr bool verbose = false;
}
}
static SignalAction trapHandler(Signal signal, SigInfo& sigInfo, PlatformRegisters& context)
{
RELEASE_ASSERT(signal == Signal::AccessFault);
auto instructionPointer = MachineContext::instructionPointer(context);
if (!instructionPointer)
return SignalAction::NotHandled;
void* faultingInstruction = instructionPointer->untaggedPtr();
dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "starting handler for fault at: ", RawPointer(faultingInstruction));
#if ENABLE(JIT)
dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "JIT memory start: ", RawPointer(startOfFixedExecutableMemoryPool()), " end: ", RawPointer(endOfFixedExecutableMemoryPool()));
#endif
dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "WasmIPInt memory start: ", RawPointer(untagCodePtr<void*, CFunctionPtrTag>(LLInt::wasmIPIntPCRangeStart)), " end: ", RawPointer(untagCodePtr<void*, CFunctionPtrTag>(LLInt::wasmIPIntPCRangeEnd)));
// First we need to make sure we are in JIT code or Wasm IPInt code before we can aquire any locks. Otherwise,
// we might have crashed in code that is already holding one of the locks we want to aquire.
assertIsNotTagged(faultingInstruction);
if (isJITPC(faultingInstruction) || LLInt::isWasmIPIntPC(faultingInstruction)) {
std::optional<Wasm::ExceptionType> exception;
{
void* faultingAddress = sigInfo.faultingAddress;
dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "checking faulting address: ", RawPointer(faultingAddress), " is in an active fast memory");
// Trapping null access for WasmGC Array / Struct.
if (std::bit_cast<uintptr_t>(faultingAddress) < lowestAccessibleAddress())
exception = ExceptionType::NullAccess;
else if (Wasm::Memory::addressIsInGrowableOrFastMemory(faultingAddress))
exception = ExceptionType::OutOfBoundsMemoryAccess;
}
if (exception) {
dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "found active fast memory for faulting address");
auto didFaultInWasm = [](void* faultingInstruction) -> std::tuple<bool, Wasm::Callee*> {
if (LLInt::isWasmIPIntPC(faultingInstruction))
return { true, nullptr };
auto& calleeRegistry = NativeCalleeRegistry::singleton();
Locker locker { calleeRegistry.getLock() };
for (auto* callee : calleeRegistry.allCallees()) {
if (callee->category() != NativeCallee::Category::Wasm)
continue;
auto* wasmCallee = uncheckedDowncast<Wasm::Callee>(callee);
auto [start, end] = wasmCallee->range();
dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "function start: ", RawPointer(start), " end: ", RawPointer(end));
if (start <= faultingInstruction && faultingInstruction < end) {
dataLogLnIf(WasmFaultSignalHandlerInternal::verbose, "found match");
return { true, wasmCallee };
}
}
return { false, nullptr };
};
auto [isWasm, callee] = didFaultInWasm(faultingInstruction);
if (isWasm) {
auto* instance = jsSecureCast<JSWebAssemblyInstance*>(static_cast<JSCell*>(MachineContext::wasmInstancePointer(context)));
instance->setFaultPC(exception.value(), faultingInstruction);
#if CPU(ARM64E) && HAVE(HARDENED_MACH_EXCEPTIONS)
if (g_wtfConfig.signalHandlers.useHardenedHandler) {
MachineContext::setInstructionPointer(context, presignedTrampoline);
return SignalAction::Handled;
}
#endif
MachineContext::setInstructionPointer(context, LLInt::getCodePtr<CFunctionPtrTag>(wasm_throw_from_fault_handler_trampoline_reg_instance));
return SignalAction::Handled;
}
}
}
return SignalAction::NotHandled;
}
void activateSignalingMemory()
{
static std::once_flag once;
std::call_once(once, [] {
if (!Wasm::isSupported())
return;
if (!Options::useWasmFaultSignalHandler())
return;
activateSignalHandlersFor(Signal::AccessFault);
});
}
void prepareSignalingMemory()
{
static std::once_flag once;
std::call_once(once, [] {
if (!Wasm::isSupported())
return;
if (!Options::useWasmFaultSignalHandler())
return;
#if CPU(ARM64E) && HAVE(HARDENED_MACH_EXCEPTIONS)
presignedTrampoline = g_wtfConfig.signalHandlers.presignReturnPCForHandler(LLInt::getCodePtr<NoPtrTag>(wasm_throw_from_fault_handler_trampoline_reg_instance));
#endif
addSignalHandler(Signal::AccessFault, [] (Signal signal, SigInfo& sigInfo, PlatformRegisters& ucontext) {
return trapHandler(signal, sigInfo, ucontext);
});
});
}
ptrdiff_t maxAcceptableOffsetForNullReference()
{
#if CPU(ADDRESS64)
if (!Options::useWasmFaultSignalHandler())
return 0;
ptrdiff_t address = lowestAccessibleAddress();
ptrdiff_t nullValue =JSValue::encode(jsNull());
ptrdiff_t accessed = sizeof(v128_t) * 2; // Paired v128_t access.
if (address < (nullValue + accessed))
return 0;
return address - nullValue - accessed;
#else
return 0;
#endif
}
} } // namespace JSC::Wasm
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
#endif // ENABLE(WEBASSEMBLY)
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