Source/WebKit/Platform/IPC/Encoder.cpp

/*
 * Copyright (C) 2010-2020 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.
 *
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 * 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 ITS CONTRIBUTORS
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#include "config.h"
#include "Encoder.h"

#include "ArgumentCoders.h"
#include "DataReference.h"
#include "MessageFlags.h"
#include <algorithm>
#include <wtf/OptionSet.h>
#include <wtf/UniqueRef.h>

#if OS(DARWIN)
#include <sys/mman.h>
#endif

namespace IPC {

static const uint8_t defaultMessageFlags = 0;

template <typename T>
static inline bool allocBuffer(T*& buffer, size_t size)
{
#if OS(DARWIN)
    buffer = static_cast<T*>(mmap(0, size, PROT_READ | PROT_WRITE, MAP_ANON | MAP_PRIVATE, -1, 0));
    return buffer != MAP_FAILED;
#else
    buffer = static_cast<T*>(fastMalloc(size));
    return !!buffer;
#endif
}

static inline void freeBuffer(void* addr, size_t size)
{
#if OS(DARWIN)
    munmap(addr, size);
#else
    UNUSED_PARAM(size);
    fastFree(addr);
#endif
}

Encoder::Encoder(MessageName messageName, uint64_t destinationID)
    : m_messageName(messageName)
    , m_destinationID(destinationID)
{
    encodeHeader();
}

Encoder::~Encoder()
{
    if (m_buffer != m_inlineBuffer)
        freeBuffer(m_buffer, m_bufferCapacity);
    // FIXME: We need to dispose of the attachments in cases of failure.
}

ShouldDispatchWhenWaitingForSyncReply Encoder::shouldDispatchMessageWhenWaitingForSyncReply() const
{
    if (messageFlags().contains(MessageFlags::DispatchMessageWhenWaitingForSyncReply))
        return ShouldDispatchWhenWaitingForSyncReply::Yes;
    if (messageFlags().contains(MessageFlags::DispatchMessageWhenWaitingForUnboundedSyncReply))
        return ShouldDispatchWhenWaitingForSyncReply::YesDuringUnboundedIPC;
    return ShouldDispatchWhenWaitingForSyncReply::No;
}

void Encoder::setShouldDispatchMessageWhenWaitingForSyncReply(ShouldDispatchWhenWaitingForSyncReply shouldDispatchWhenWaitingForSyncReply)
{
    switch (shouldDispatchWhenWaitingForSyncReply) {
    case ShouldDispatchWhenWaitingForSyncReply::No:
        messageFlags().remove(MessageFlags::DispatchMessageWhenWaitingForSyncReply);
        messageFlags().remove(MessageFlags::DispatchMessageWhenWaitingForUnboundedSyncReply);
        break;
    case ShouldDispatchWhenWaitingForSyncReply::Yes:
        messageFlags().add(MessageFlags::DispatchMessageWhenWaitingForSyncReply);
        messageFlags().remove(MessageFlags::DispatchMessageWhenWaitingForUnboundedSyncReply);
        break;
    case ShouldDispatchWhenWaitingForSyncReply::YesDuringUnboundedIPC:
        messageFlags().remove(MessageFlags::DispatchMessageWhenWaitingForSyncReply);
        messageFlags().add(MessageFlags::DispatchMessageWhenWaitingForUnboundedSyncReply);
        break;
    }
}

void Encoder::setFullySynchronousModeForTesting()
{
    messageFlags().add(MessageFlags::UseFullySynchronousModeForTesting);
}

void Encoder::setShouldMaintainOrderingWithAsyncMessages()
{
    messageFlags().add(MessageFlags::MaintainOrderingWithAsyncMessages);
}

void Encoder::wrapForTesting(UniqueRef<Encoder>&& original)
{
    ASSERT(isSyncMessage());
    ASSERT(!original->isSyncMessage());

    original->setShouldDispatchMessageWhenWaitingForSyncReply(ShouldDispatchWhenWaitingForSyncReply::Yes);

    *this << DataReference(original->buffer(), original->bufferSize());

    Vector<Attachment> attachments = original->releaseAttachments();
    reserve(attachments.size());
    for (Attachment& attachment : attachments)
        addAttachment(WTFMove(attachment));
}

static inline size_t roundUpToAlignment(size_t value, size_t alignment)
{
    return ((value + alignment - 1) / alignment) * alignment;
}

void Encoder::reserve(size_t size)
{
    if (size <= m_bufferCapacity)
        return;

    size_t newCapacity = roundUpToAlignment(m_bufferCapacity * 2, 4096);
    while (newCapacity < size)
        newCapacity *= 2;

    uint8_t* newBuffer;
    if (!allocBuffer(newBuffer, newCapacity))
        CRASH();

    memcpy(newBuffer, m_buffer, m_bufferSize);

    if (m_buffer != m_inlineBuffer)
        freeBuffer(m_buffer, m_bufferCapacity);

    m_buffer = newBuffer;
    m_bufferCapacity = newCapacity;
}

void Encoder::encodeHeader()
{
    *this << defaultMessageFlags;
    *this << m_messageName;
    *this << m_destinationID;
}

OptionSet<MessageFlags>& Encoder::messageFlags()
{
    // FIXME: We should probably pass an OptionSet<MessageFlags> into the Encoder constructor instead of encoding defaultMessageFlags then using this to change it later.
    static_assert(sizeof(OptionSet<MessageFlags>::StorageType) == 1, "Encoder uses the first byte of the buffer for message flags.");
    return *reinterpret_cast<OptionSet<MessageFlags>*>(buffer());
}

const OptionSet<MessageFlags>& Encoder::messageFlags() const
{
    return *reinterpret_cast<OptionSet<MessageFlags>*>(buffer());
}

uint8_t* Encoder::grow(size_t alignment, size_t size)
{
    size_t alignedSize = roundUpToAlignment(m_bufferSize, alignment);
    reserve(alignedSize + size);

    std::memset(m_buffer + m_bufferSize, 0, alignedSize - m_bufferSize);

    m_bufferSize = alignedSize + size;
    m_bufferPointer = m_buffer + alignedSize + size;

    return m_buffer + alignedSize;
}

void Encoder::encodeFixedLengthData(const uint8_t* data, size_t size, size_t alignment)
{
    ASSERT(!(reinterpret_cast<uintptr_t>(data) % alignment));

    uint8_t* buffer = grow(alignment, size);
    memcpy(buffer, data, size);
}

void Encoder::addAttachment(Attachment&& attachment)
{
    m_attachments.append(WTFMove(attachment));
}

Vector<Attachment> Encoder::releaseAttachments()
{
    return std::exchange(m_attachments, { });
}

bool Encoder::hasAttachments() const
{
    return !m_attachments.isEmpty();
}

} // namespace IPC