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Xdr.h
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Xdr.h
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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
* vim: set ts=8 sts=2 et sw=2 tw=80:
* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#ifndef vm_Xdr_h
#define vm_Xdr_h
#include "mozilla/EndianUtils.h"
#include "mozilla/TypeTraits.h"
#include "mozilla/Utf8.h"
#include "jsapi.h"
#include "jsfriendapi.h"
#include "NamespaceImports.h"
#include "js/CompileOptions.h"
#include "js/Transcoding.h"
#include "js/TypeDecls.h"
#include "vm/JSAtom.h"
namespace js {
class LifoAlloc;
enum XDRMode { XDR_ENCODE, XDR_DECODE };
using XDRResult = mozilla::Result<mozilla::Ok, JS::TranscodeResult>;
class XDRBufferBase {
public:
explicit XDRBufferBase(JSContext* cx, size_t cursor = 0)
: context_(cx),
cursor_(cursor)
#ifdef DEBUG
// Note, when decoding the buffer can be set to a range, which does not
// have any alignment requirement as opposed to allocations.
,
aligned_(false)
#endif
{
}
JSContext* cx() const { return context_; }
size_t cursor() const { return cursor_; }
#ifdef DEBUG
// This function records if the cursor got changed by codeAlign or by any
// other read/write of data. This is used for AutoXDRTree assertions, as a
// way to ensure that the last thing done is properly setting the alignment
// with codeAlign function.
void setAligned(bool aligned) { aligned_ = aligned; }
bool isAligned() const { return aligned_; }
#else
void setAligned(bool) const {}
bool isAligned() const { return true; }
#endif
protected:
JSContext* const context_;
size_t cursor_;
#ifdef DEBUG
bool aligned_;
#endif
};
template <XDRMode mode>
class XDRBuffer;
template <>
class XDRBuffer<XDR_ENCODE> : public XDRBufferBase {
public:
XDRBuffer(JSContext* cx, JS::TranscodeBuffer& buffer, size_t cursor = 0)
: XDRBufferBase(cx, cursor), buffer_(buffer) {}
uint8_t* write(size_t n) {
MOZ_ASSERT(n != 0);
setAligned(false);
if (!buffer_.growByUninitialized(n)) {
ReportOutOfMemory(cx());
return nullptr;
}
uint8_t* ptr = &buffer_[cursor_];
cursor_ += n;
return ptr;
}
const uint8_t* read(size_t n) {
MOZ_CRASH("Should never read in encode mode");
return nullptr;
}
uintptr_t uptr() const {
// Note: Avoid bounds check assertion if the buffer is not yet allocated.
return reinterpret_cast<uintptr_t>(buffer_.begin() + cursor_);
}
private:
JS::TranscodeBuffer& buffer_;
};
template <>
class XDRBuffer<XDR_DECODE> : public XDRBufferBase {
public:
XDRBuffer(JSContext* cx, const JS::TranscodeRange& range)
: XDRBufferBase(cx), buffer_(range) {}
XDRBuffer(JSContext* cx, JS::TranscodeBuffer& buffer, size_t cursor = 0)
: XDRBufferBase(cx, cursor), buffer_(buffer.begin(), buffer.length()) {}
const uint8_t* read(size_t n) {
MOZ_ASSERT(cursor_ < buffer_.length());
setAligned(false);
uint8_t* ptr = &buffer_[cursor_];
cursor_ += n;
// Don't let buggy code read past our buffer
if (cursor_ > buffer_.length()) {
return nullptr;
}
return ptr;
}
uint8_t* write(size_t n) {
MOZ_CRASH("Should never write in decode mode");
return nullptr;
}
uintptr_t uptr() const {
// Note: Avoid bounds check assertion at the end of the buffer.
return reinterpret_cast<uintptr_t>(buffer_.begin().get() + cursor_);
}
private:
const JS::TranscodeRange buffer_;
};
class XDRCoderBase;
class XDRIncrementalEncoder;
using XDRAlignment = char16_t;
static const uint8_t AlignPadding[sizeof(XDRAlignment)] = {0, 0};
// An AutoXDRTree is used to identify section encoded by an
// XDRIncrementalEncoder.
//
// Its primary goal is to identify functions, such that we can first encode them
// as LazyScript, and later replaced by them by their corresponding bytecode
// once delazified.
//
// As a convenience, this is also used to identify the top-level of the content
// encoded by an XDRIncrementalEncoder.
//
// Sections can be encoded any number of times in an XDRIncrementalEncoder, and
// the latest encoded version would replace all the previous one.
class MOZ_RAII AutoXDRTree {
public:
// For a JSFunction, a tree key is defined as being:
// script()->begin << 32 | script()->end
//
// Based on the invariant that |begin <= end|, we can make special
// keys, such as the top-level script.
using Key = uint64_t;
AutoXDRTree(XDRCoderBase* xdr, Key key);
~AutoXDRTree();
// Indicate the lack of a key for the current tree.
static constexpr Key noKey = 0;
// Used to end the slices when there is no children.
static constexpr Key noSubTree = Key(1) << 32;
// Used as the root key of the tree in the hash map.
static constexpr Key topLevel = Key(2) << 32;
private:
friend class XDRIncrementalEncoder;
Key key_;
AutoXDRTree* parent_;
XDRCoderBase* xdr_;
};
class XDRCoderBase {
private:
#ifdef DEBUG
JS::TranscodeResult resultCode_;
#endif
protected:
XDRCoderBase()
#ifdef DEBUG
: resultCode_(JS::TranscodeResult_Ok)
#endif
{
}
public:
virtual AutoXDRTree::Key getTopLevelTreeKey() const {
return AutoXDRTree::noKey;
}
virtual AutoXDRTree::Key getTreeKey(JSFunction* fun) const {
return AutoXDRTree::noKey;
}
virtual void createOrReplaceSubTree(AutoXDRTree* child){};
virtual void endSubTree(){};
virtual bool isAligned(size_t n) = 0;
#ifdef DEBUG
// Record logical failures of XDR.
JS::TranscodeResult resultCode() const { return resultCode_; }
void setResultCode(JS::TranscodeResult code) {
MOZ_ASSERT(resultCode() == JS::TranscodeResult_Ok);
resultCode_ = code;
}
bool validateResultCode(JSContext* cx, JS::TranscodeResult code) const;
#endif
};
/*
* XDR serialization state. All data is encoded in little endian.
*/
template <XDRMode mode>
class XDRState : public XDRCoderBase {
protected:
XDRBuffer<mode> buf;
public:
XDRState(JSContext* cx, JS::TranscodeBuffer& buffer, size_t cursor = 0)
: buf(cx, buffer, cursor) {}
template <typename RangeType>
XDRState(JSContext* cx, const RangeType& range) : buf(cx, range) {}
virtual ~XDRState(){};
JSContext* cx() const { return buf.cx(); }
virtual bool hasOptions() const { return false; }
virtual const JS::ReadOnlyCompileOptions& options() {
MOZ_CRASH("does not have options");
}
virtual bool hasScriptSourceObjectOut() const { return false; }
virtual ScriptSourceObject** scriptSourceObjectOut() {
MOZ_CRASH("does not have scriptSourceObjectOut.");
}
XDRResult fail(JS::TranscodeResult code) {
#ifdef DEBUG
MOZ_ASSERT(code != JS::TranscodeResult_Ok);
MOZ_ASSERT(validateResultCode(cx(), code));
setResultCode(code);
#endif
return mozilla::Err(code);
}
XDRResult peekData(const uint8_t** pptr, size_t length) {
const uint8_t* ptr = buf.read(length);
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
*pptr = ptr;
return Ok();
}
// Alignment is required when doing memcpy of data which contains element
// largers than 1 byte.
bool isAligned(size_t n) override {
MOZ_ASSERT(mozilla::IsPowerOfTwo(n));
size_t mask = n - 1;
size_t offset = buf.uptr() & mask;
// In debug build, we not only check if the cursor is aligned, but also
// if the last cursor manipulation was made by the codeAlign function.
return offset == 0 && buf.isAligned();
}
XDRResult codeAlign(size_t n) {
MOZ_ASSERT(mozilla::IsPowerOfTwo(n));
size_t mask = n - 1;
MOZ_ASSERT_IF(mode == XDR_ENCODE,
(buf.uptr() & mask) == (buf.cursor() & mask));
size_t offset = buf.uptr() & mask;
if (offset) {
size_t padding = n - offset;
MOZ_ASSERT(padding < sizeof(AlignPadding));
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf.write(padding);
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
memcpy(ptr, AlignPadding, padding);
} else {
const uint8_t* ptr = buf.read(padding);
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
if (memcmp(ptr, AlignPadding, padding) != 0) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
}
}
buf.setAligned(true);
MOZ_ASSERT(isAligned(n));
return Ok();
}
XDRResult codeUint8(uint8_t* n) {
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf.write(sizeof(*n));
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
*ptr = *n;
} else {
const uint8_t* ptr = buf.read(sizeof(*n));
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
*n = *ptr;
}
return Ok();
}
XDRResult codeUint16(uint16_t* n) {
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf.write(sizeof(*n));
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
mozilla::LittleEndian::writeUint16(ptr, *n);
} else {
const uint8_t* ptr = buf.read(sizeof(*n));
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
*n = mozilla::LittleEndian::readUint16(ptr);
}
return Ok();
}
XDRResult codeUint32(uint32_t* n) {
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf.write(sizeof(*n));
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
mozilla::LittleEndian::writeUint32(ptr, *n);
} else {
const uint8_t* ptr = buf.read(sizeof(*n));
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
*n = mozilla::LittleEndian::readUint32(ptr);
}
return Ok();
}
XDRResult codeUint64(uint64_t* n) {
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf.write(sizeof(*n));
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
mozilla::LittleEndian::writeUint64(ptr, *n);
} else {
const uint8_t* ptr = buf.read(sizeof(*n));
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
*n = mozilla::LittleEndian::readUint64(ptr);
}
return Ok();
}
/*
* Use SFINAE to refuse any specialization which is not an enum. Uses of
* this function do not have to specialize the type of the enumerated field
* as C++ will extract the parameterized from the argument list.
*/
template <typename T>
XDRResult codeEnum32(
T* val,
typename mozilla::EnableIf<mozilla::IsEnum<T>::value, T>::Type* = NULL) {
// Mix the enumeration value with a random magic number, such that a
// corruption with a low-ranged value (like 0) is less likely to cause a
// miss-interpretation of the XDR content and instead cause a failure.
const uint32_t MAGIC = 0x21AB218C;
uint32_t tmp;
if (mode == XDR_ENCODE) {
tmp = uint32_t(*val) ^ MAGIC;
}
MOZ_TRY(codeUint32(&tmp));
if (mode == XDR_DECODE) {
*val = T(tmp ^ MAGIC);
}
return Ok();
}
XDRResult codeDouble(double* dp) {
union DoublePun {
double d;
uint64_t u;
} pun;
if (mode == XDR_ENCODE) {
pun.d = *dp;
}
MOZ_TRY(codeUint64(&pun.u));
if (mode == XDR_DECODE) {
*dp = pun.d;
}
return Ok();
}
XDRResult codeMarker(uint32_t magic) {
uint32_t actual = magic;
MOZ_TRY(codeUint32(&actual));
if (actual != magic) {
// Fail in debug, but only soft-fail in release
MOZ_ASSERT(false, "Bad XDR marker");
return fail(JS::TranscodeResult_Failure_BadDecode);
}
return Ok();
}
XDRResult codeBytes(void* bytes, size_t len) {
if (len == 0) {
return Ok();
}
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf.write(len);
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
memcpy(ptr, bytes, len);
} else {
const uint8_t* ptr = buf.read(len);
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
memcpy(bytes, ptr, len);
}
return Ok();
}
/*
* During encoding the string is written into the buffer together with its
* terminating '\0'. During decoding the method returns a pointer into the
* decoding buffer and the caller must copy the string if it will outlive
* the decoding buffer.
*/
XDRResult codeCString(const char** sp) {
uint64_t len64;
if (mode == XDR_ENCODE) {
len64 = (uint64_t)(strlen(*sp) + 1);
}
MOZ_TRY(codeUint64(&len64));
size_t len = (size_t)len64;
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf.write(len);
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
memcpy(ptr, *sp, len);
} else {
const uint8_t* ptr = buf.read(len);
if (!ptr || ptr[len] != '\0') {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
*sp = reinterpret_cast<const char*>(ptr);
}
return Ok();
}
XDRResult codeChars(JS::Latin1Char* chars, size_t nchars);
XDRResult codeChars(mozilla::Utf8Unit* units, size_t nchars);
// If |nchars > 0|, this calls |codeAlign(sizeof(char16_t))| so callers
// don't have to.
XDRResult codeChars(char16_t* chars, size_t nchars);
XDRResult codeFunction(JS::MutableHandleFunction objp,
HandleScriptSourceObject sourceObject = nullptr);
XDRResult codeScript(MutableHandleScript scriptp);
};
using XDREncoder = XDRState<XDR_ENCODE>;
using XDRDecoder = XDRState<XDR_DECODE>;
class XDROffThreadDecoder : public XDRDecoder {
const JS::ReadOnlyCompileOptions* options_;
ScriptSourceObject** sourceObjectOut_;
public:
// Note, when providing an JSContext, where isJSContext is false,
// then the initialization of the ScriptSourceObject would remain
// incomplete. Thus, the sourceObjectOut must be used to finish the
// initialization with ScriptSourceObject::initFromOptions after the
// decoding.
//
// When providing a sourceObjectOut pointer, you have to ensure that it is
// marked by the GC to avoid dangling pointers.
XDROffThreadDecoder(JSContext* cx, const JS::ReadOnlyCompileOptions* options,
ScriptSourceObject** sourceObjectOut,
const JS::TranscodeRange& range)
: XDRDecoder(cx, range),
options_(options),
sourceObjectOut_(sourceObjectOut) {
MOZ_ASSERT(options);
MOZ_ASSERT(sourceObjectOut);
MOZ_ASSERT(*sourceObjectOut == nullptr);
}
bool hasOptions() const override { return true; }
const JS::ReadOnlyCompileOptions& options() override { return *options_; }
bool hasScriptSourceObjectOut() const override { return true; }
ScriptSourceObject** scriptSourceObjectOut() override {
return sourceObjectOut_;
}
};
class XDRIncrementalEncoder : public XDREncoder {
// The incremental encoder encodes the content of scripts and functions in
// the XDRBuffer. It can be used to encode multiple times the same
// AutoXDRTree, and uses its key to identify which part to replace.
//
// Internally, this encoder keeps a tree representation of the scopes. Each
// node is composed of a vector of slices which are interleaved by child
// nodes.
//
// A slice corresponds to an index and a length within the content of the
// slices_ buffer. The index is updated when a slice is created, and the
// length is updated when the slice is ended, either by creating a new scope
// child, or by closing the scope and going back to the parent.
//
// +---+---+---+
// begin | | | |
// length | | | |
// child | . | . | . |
// +-|-+-|-+---+
// | |
// +---------+ +---------+
// | |
// v v
// +---+---+ +---+
// | | | | |
// | | | | |
// | . | . | | . |
// +-|-+---+ +---+
// |
// |
// |
// v
// +---+
// | |
// | |
// | . |
// +---+
//
//
// The tree key is used to identify the child nodes, and to make them
// easily replaceable.
//
// The tree is rooted at the |topLevel| key.
//
struct Slice {
size_t sliceBegin;
size_t sliceLength;
AutoXDRTree::Key child;
};
using SlicesNode = Vector<Slice, 1, SystemAllocPolicy>;
using SlicesTree =
HashMap<AutoXDRTree::Key, SlicesNode, DefaultHasher<AutoXDRTree::Key>,
SystemAllocPolicy>;
// Last opened XDR-tree on the stack.
AutoXDRTree* scope_;
// Node corresponding to the opened scope.
SlicesNode* node_;
// Tree of slices.
SlicesTree tree_;
JS::TranscodeBuffer slices_;
bool oom_;
class DepthFirstSliceIterator;
public:
explicit XDRIncrementalEncoder(JSContext* cx)
: XDREncoder(cx, slices_, 0),
scope_(nullptr),
node_(nullptr),
oom_(false) {}
virtual ~XDRIncrementalEncoder() {}
AutoXDRTree::Key getTopLevelTreeKey() const override;
AutoXDRTree::Key getTreeKey(JSFunction* fun) const override;
void createOrReplaceSubTree(AutoXDRTree* child) override;
void endSubTree() override;
// Append the content collected during the incremental encoding into the
// buffer given as argument.
XDRResult linearize(JS::TranscodeBuffer& buffer);
};
template <XDRMode mode>
XDRResult XDRAtom(XDRState<mode>* xdr, js::MutableHandleAtom atomp);
} /* namespace js */
#endif /* vm_Xdr_h */