Source/JavaScriptCore/wasm/WasmThunks.cpp

/*
 * Copyright (C) 2017-2018 Apple Inc. All rights reserved.
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 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
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 * 1. Redistributions of source code must retain the above copyright
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 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' AND ANY
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 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE INC. OR
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 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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#include "config.h"
#include "WasmThunks.h"

#if ENABLE(WEBASSEMBLY)

#include "CCallHelpers.h"
#include "HeapCellInlines.h"
#include "JITExceptions.h"
#include "LinkBuffer.h"
#include "ScratchRegisterAllocator.h"
#include "WasmContext.h"
#include "WasmExceptionType.h"
#include "WasmInstance.h"
#include "WasmOperations.h"

namespace JSC { namespace Wasm {

MacroAssemblerCodeRef<JITThunkPtrTag> throwExceptionFromWasmThunkGenerator(const AbstractLocker&)
{
    CCallHelpers jit;

    // The thing that jumps here must move ExceptionType into the argumentGPR1 before jumping here.
    // We're allowed to use temp registers here. We are not allowed to use callee saves.
    jit.loadWasmContextInstance(GPRInfo::argumentGPR2);
    jit.loadPtr(CCallHelpers::Address(GPRInfo::argumentGPR2, Instance::offsetOfPointerToTopEntryFrame()), GPRInfo::argumentGPR0);
    jit.loadPtr(CCallHelpers::Address(GPRInfo::argumentGPR0), GPRInfo::argumentGPR0);
    jit.copyCalleeSavesToEntryFrameCalleeSavesBuffer(GPRInfo::argumentGPR0);
    jit.move(GPRInfo::callFrameRegister, GPRInfo::argumentGPR0);

    CCallHelpers::Call call = jit.call(OperationPtrTag);
    jit.farJump(GPRInfo::returnValueGPR, ExceptionHandlerPtrTag);
    jit.breakpoint(); // We should not reach this.

    ThrowWasmException throwWasmException = Thunks::singleton().throwWasmException();
    RELEASE_ASSERT(throwWasmException);
    LinkBuffer linkBuffer(jit, GLOBAL_THUNK_ID);
    linkBuffer.link(call, FunctionPtr<OperationPtrTag>(throwWasmException));
    return FINALIZE_WASM_CODE(linkBuffer, JITThunkPtrTag, "Throw exception from Wasm");
}

MacroAssemblerCodeRef<JITThunkPtrTag> throwStackOverflowFromWasmThunkGenerator(const AbstractLocker& locker)
{
    CCallHelpers jit;

    int32_t stackSpace = WTF::roundUpToMultipleOf(stackAlignmentBytes(), RegisterSet::calleeSaveRegisters().numberOfSetRegisters() * sizeof(Register));
    ASSERT(static_cast<unsigned>(stackSpace) < Options::softReservedZoneSize());
    jit.addPtr(CCallHelpers::TrustedImm32(-stackSpace), GPRInfo::callFrameRegister, MacroAssembler::stackPointerRegister);
    jit.move(CCallHelpers::TrustedImm32(static_cast<uint32_t>(ExceptionType::StackOverflow)), GPRInfo::argumentGPR1);
    auto jumpToExceptionHandler = jit.jump();
    LinkBuffer linkBuffer(jit, GLOBAL_THUNK_ID);
    linkBuffer.link(jumpToExceptionHandler, CodeLocationLabel<JITThunkPtrTag>(Thunks::singleton().stub(locker, throwExceptionFromWasmThunkGenerator).code()));
    return FINALIZE_WASM_CODE(linkBuffer, JITThunkPtrTag, "Throw stack overflow from Wasm");
}

MacroAssemblerCodeRef<JITThunkPtrTag> triggerOMGEntryTierUpThunkGenerator(const AbstractLocker&)
{
    // We expect that the user has already put the function index into GPRInfo::argumentGPR1
    CCallHelpers jit;

    jit.emitFunctionPrologue();

    const unsigned extraPaddingBytes = 0;
    RegisterSet registersToSpill = RegisterSet::allRegisters();
    registersToSpill.exclude(RegisterSet::registersToNotSaveForCCall());
    unsigned numberOfStackBytesUsedForRegisterPreservation = ScratchRegisterAllocator::preserveRegistersToStackForCall(jit, registersToSpill, extraPaddingBytes);

    jit.loadWasmContextInstance(GPRInfo::argumentGPR0);
    jit.move(MacroAssembler::TrustedImmPtr(tagCFunctionPtr<OperationPtrTag>(operationWasmTriggerTierUpNow)), GPRInfo::argumentGPR2);
    jit.call(GPRInfo::argumentGPR2, OperationPtrTag);

    ScratchRegisterAllocator::restoreRegistersFromStackForCall(jit, registersToSpill, RegisterSet(), numberOfStackBytesUsedForRegisterPreservation, extraPaddingBytes);

    jit.emitFunctionEpilogue();
    jit.ret();
    LinkBuffer linkBuffer(jit, GLOBAL_THUNK_ID);
    return FINALIZE_WASM_CODE(linkBuffer, JITThunkPtrTag, "Trigger OMG entry tier up");
}

static Thunks* thunks;
void Thunks::initialize()
{
    thunks = new Thunks;
}

Thunks& Thunks::singleton()
{
    ASSERT(thunks);
    return *thunks;
}

void Thunks::setThrowWasmException(ThrowWasmException throwWasmException)
{
    auto locker = holdLock(m_lock);
    // The thunks are unique for the entire process, therefore changing the throwing function changes it for all uses of WebAssembly.
    RELEASE_ASSERT(!m_throwWasmException || m_throwWasmException == throwWasmException);
    m_throwWasmException = throwWasmException;
}

ThrowWasmException Thunks::throwWasmException()
{
    return m_throwWasmException;
}

MacroAssemblerCodeRef<JITThunkPtrTag> Thunks::stub(ThunkGenerator generator)
{
    auto locker = holdLock(m_lock);
    return stub(locker, generator);
}

MacroAssemblerCodeRef<JITThunkPtrTag> Thunks::stub(const AbstractLocker& locker, ThunkGenerator generator)
{
    ASSERT(!!generator);
    {
        auto addResult = m_stubs.add(generator, MacroAssemblerCodeRef<JITThunkPtrTag>());
        if (!addResult.isNewEntry)
            return addResult.iterator->value;
    }

    MacroAssemblerCodeRef<JITThunkPtrTag> code = generator(locker);
    // We specifically don't use the iterator here to allow generator to recursively change m_stubs.
    m_stubs.set(generator, code);
    return code;
}

MacroAssemblerCodeRef<JITThunkPtrTag> Thunks::existingStub(ThunkGenerator generator)
{
    auto locker = holdLock(m_lock);

    auto iter = m_stubs.find(generator);
    if (iter != m_stubs.end())
        return iter->value;

    return MacroAssemblerCodeRef<JITThunkPtrTag>();
}

} } // namespace JSC::Wasm

#endif // ENABLE(WEBASSEMBLY)