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Xdr.cpp
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Xdr.cpp
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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/. */
#include "vm/Xdr.h"
#include "mozilla/ArrayUtils.h"
#include "mozilla/ScopeExit.h"
#include "mozilla/Utf8.h"
#include <algorithm> // std::transform
#include <string.h>
#include <type_traits> // std::is_same
#include <utility> // std::move
#include "jsapi.h"
#include "debugger/DebugAPI.h"
#include "js/BuildId.h" // JS::BuildIdCharVector
#include "vm/EnvironmentObject.h"
#include "vm/JSContext.h"
#include "vm/JSScript.h"
#include "vm/TraceLogging.h"
using namespace js;
using mozilla::ArrayEqual;
using mozilla::Utf8Unit;
#ifdef DEBUG
bool XDRCoderBase::validateResultCode(JSContext* cx,
JS::TranscodeResult code) const {
// NOTE: This function is called to verify that we do not have a pending
// exception on the JSContext at the same time as a TranscodeResult failure.
if (cx->isHelperThreadContext()) {
return true;
}
return cx->isExceptionPending() == bool(code == JS::TranscodeResult_Throw);
}
#endif
template <XDRMode mode>
XDRResult XDRState<mode>::codeChars(char* chars, size_t nchars) {
return codeBytes(chars, nchars);
}
template <XDRMode mode>
XDRResult XDRState<mode>::codeChars(Latin1Char* chars, size_t nchars) {
static_assert(sizeof(Latin1Char) == 1,
"Latin1Char must be 1 byte for nchars below to be the "
"proper count of bytes");
static_assert(std::is_same<Latin1Char, unsigned char>::value,
"Latin1Char must be unsigned char to C++-safely reinterpret "
"the bytes generically copied below as Latin1Char");
return codeBytes(chars, nchars);
}
template <XDRMode mode>
XDRResult XDRState<mode>::codeChars(Utf8Unit* units, size_t count) {
if (count == 0) {
return Ok();
}
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf->write(count);
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
std::transform(units, units + count, ptr,
[](const Utf8Unit& unit) { return unit.toUint8(); });
} else {
const uint8_t* ptr = buf->read(count);
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
std::transform(ptr, ptr + count, units,
[](const uint8_t& value) { return Utf8Unit(value); });
}
return Ok();
}
template <XDRMode mode>
XDRResult XDRState<mode>::codeChars(char16_t* chars, size_t nchars) {
if (nchars == 0) {
return Ok();
}
size_t nbytes = nchars * sizeof(char16_t);
if (mode == XDR_ENCODE) {
uint8_t* ptr = buf->write(nbytes);
if (!ptr) {
return fail(JS::TranscodeResult_Throw);
}
// |mozilla::NativeEndian| correctly handles writing into unaligned |ptr|.
mozilla::NativeEndian::copyAndSwapToLittleEndian(ptr, chars, nchars);
} else {
const uint8_t* ptr = buf->read(nbytes);
if (!ptr) {
return fail(JS::TranscodeResult_Failure_BadDecode);
}
// |mozilla::NativeEndian| correctly handles reading from unaligned |ptr|.
mozilla::NativeEndian::copyAndSwapFromLittleEndian(chars, ptr, nchars);
}
return Ok();
}
template <XDRMode mode, typename CharT>
static XDRResult XDRCodeCharsZ(XDRState<mode>* xdr,
XDRTranscodeString<CharT>& buffer) {
MOZ_ASSERT_IF(mode == XDR_ENCODE, !buffer.empty());
MOZ_ASSERT_IF(mode == XDR_DECODE, buffer.empty());
using OwnedString = js::UniquePtr<CharT[], JS::FreePolicy>;
OwnedString owned;
static_assert(JSString::MAX_LENGTH <= INT32_MAX,
"String length must fit in int32_t");
uint32_t length = 0;
CharT* chars = nullptr;
if (mode == XDR_ENCODE) {
chars = const_cast<CharT*>(buffer.template ref<const CharT*>());
// Set a reasonable limit on string length.
size_t lengthSizeT = std::char_traits<CharT>::length(chars);
if (lengthSizeT > JSString::MAX_LENGTH) {
ReportAllocationOverflow(xdr->cx());
return xdr->fail(JS::TranscodeResult_Throw);
}
length = static_cast<uint32_t>(lengthSizeT);
}
MOZ_TRY(xdr->codeUint32(&length));
if (mode == XDR_DECODE) {
owned = xdr->cx()->template make_pod_array<CharT>(length + 1);
if (!owned) {
return xdr->fail(JS::TranscodeResult_Throw);
}
chars = owned.get();
}
MOZ_TRY(xdr->codeChars(chars, length));
if (mode == XDR_DECODE) {
// Null-terminate and transfer ownership to caller.
owned[length] = '\0';
buffer.template construct<OwnedString>(std::move(owned));
}
return Ok();
}
template <XDRMode mode>
XDRResult XDRState<mode>::codeCharsZ(XDRTranscodeString<char>& buffer) {
return XDRCodeCharsZ(this, buffer);
}
template <XDRMode mode>
XDRResult XDRState<mode>::codeCharsZ(XDRTranscodeString<char16_t>& buffer) {
return XDRCodeCharsZ(this, buffer);
}
template <XDRMode mode>
static XDRResult VersionCheck(XDRState<mode>* xdr) {
JS::BuildIdCharVector buildId;
uint8_t profileSize = 0;
MOZ_ASSERT(GetBuildId);
if (!GetBuildId(&buildId)) {
ReportOutOfMemory(xdr->cx());
return xdr->fail(JS::TranscodeResult_Throw);
}
MOZ_ASSERT(!buildId.empty());
uint32_t buildIdLength;
if (mode == XDR_ENCODE) {
buildIdLength = buildId.length();
profileSize = sizeof(uintptr_t);
}
MOZ_TRY(xdr->codeUint32(&buildIdLength));
MOZ_TRY(xdr->codeUint8(&profileSize));
if (mode == XDR_DECODE && buildIdLength != buildId.length()) {
return xdr->fail(JS::TranscodeResult_Failure_BadBuildId);
}
if (mode == XDR_ENCODE) {
MOZ_TRY(xdr->codeBytes(buildId.begin(), buildIdLength));
} else {
JS::BuildIdCharVector decodedBuildId;
// Checks to make sure we are not decoding profiles of a
// different size than what was encoded.
if (profileSize != sizeof(uintptr_t)) {
return xdr->fail(JS::TranscodeResult_Failure_BadDecode);
}
// buildIdLength is already checked against the length of current
// buildId.
if (!decodedBuildId.resize(buildIdLength)) {
ReportOutOfMemory(xdr->cx());
return xdr->fail(JS::TranscodeResult_Throw);
}
MOZ_TRY(xdr->codeBytes(decodedBuildId.begin(), buildIdLength));
// We do not provide binary compatibility with older scripts.
if (!ArrayEqual(decodedBuildId.begin(), buildId.begin(), buildIdLength)) {
return xdr->fail(JS::TranscodeResult_Failure_BadBuildId);
}
}
return Ok();
}
template <XDRMode mode>
XDRResult XDRState<mode>::codeModuleObject(MutableHandleModuleObject modp) {
#ifdef DEBUG
auto sanityCheck = mozilla::MakeScopeExit(
[&] { MOZ_ASSERT(validateResultCode(cx(), resultCode())); });
#endif
if (mode == XDR_DECODE) {
modp.set(nullptr);
} else {
MOZ_ASSERT(modp->status() < MODULE_STATUS_INSTANTIATING);
}
MOZ_TRY(XDRModuleObject(this, modp));
return Ok();
}
template <XDRMode mode>
static XDRResult XDRAtomCount(XDRState<mode>* xdr, uint32_t* atomCount) {
return xdr->codeUint32(atomCount);
}
template <XDRMode mode>
static XDRResult AtomTable(XDRState<mode>* xdr) {
uint8_t atomHeader = false;
if (mode == XDR_ENCODE) {
if (xdr->hasAtomMap()) {
atomHeader = true;
}
}
MOZ_TRY(xdr->codeUint8(&atomHeader));
// If we are incrementally encoding, the atom table will be built up over the
// course of the encoding. In XDRIncrementalEncoder::linearize, we will write
// the number of atoms into the header, then append the completed atom table.
// If we are decoding, then we read the length and decode the atom table now.
if (atomHeader && mode == XDR_DECODE) {
uint32_t atomCount;
MOZ_TRY(XDRAtomCount(xdr, &atomCount));
MOZ_ASSERT(!xdr->hasAtomTable());
for (uint32_t i = 0; i < atomCount; i++) {
RootedAtom atom(xdr->cx());
MOZ_TRY(XDRAtom(xdr, &atom));
if (!xdr->atomTable().append(atom)) {
return xdr->fail(JS::TranscodeResult_Throw);
}
}
xdr->finishAtomTable();
}
return Ok();
}
template <XDRMode mode>
XDRResult XDRState<mode>::codeFunction(MutableHandleFunction funp,
HandleScriptSourceObject sourceObject) {
TraceLoggerThread* logger = TraceLoggerForCurrentThread(cx());
TraceLoggerTextId event = mode == XDR_DECODE ? TraceLogger_DecodeFunction
: TraceLogger_EncodeFunction;
AutoTraceLog tl(logger, event);
#ifdef DEBUG
auto sanityCheck = mozilla::MakeScopeExit(
[&] { MOZ_ASSERT(validateResultCode(cx(), resultCode())); });
#endif
auto guard = mozilla::MakeScopeExit([&] { funp.set(nullptr); });
RootedScope scope(cx(), &cx()->global()->emptyGlobalScope());
if (mode == XDR_DECODE) {
MOZ_ASSERT(!sourceObject);
funp.set(nullptr);
} else if (getTreeKey(funp) != AutoXDRTree::noKey) {
MOZ_ASSERT(sourceObject);
scope = funp->enclosingScope();
} else {
MOZ_ASSERT(!sourceObject);
MOZ_ASSERT(funp->enclosingScope()->is<GlobalScope>());
}
MOZ_TRY(VersionCheck(this));
MOZ_TRY(XDRInterpretedFunction(this, scope, sourceObject, funp));
guard.release();
return Ok();
}
template <XDRMode mode>
XDRResult XDRState<mode>::codeScript(MutableHandleScript scriptp) {
TraceLoggerThread* logger = TraceLoggerForCurrentThread(cx());
TraceLoggerTextId event =
mode == XDR_DECODE ? TraceLogger_DecodeScript : TraceLogger_EncodeScript;
AutoTraceLog tl(logger, event);
#ifdef DEBUG
auto sanityCheck = mozilla::MakeScopeExit(
[&] { MOZ_ASSERT(validateResultCode(cx(), resultCode())); });
#endif
auto guard = mozilla::MakeScopeExit([&] { scriptp.set(nullptr); });
AutoXDRTree scriptTree(this, getTopLevelTreeKey());
if (mode == XDR_DECODE) {
scriptp.set(nullptr);
} else {
MOZ_ASSERT(!scriptp->enclosingScope());
}
// Only write to separate header buffer if we are incrementally encoding.
bool useHeader = this->hasAtomMap();
if (useHeader) {
switchToHeaderBuf();
}
MOZ_TRY(VersionCheck(this));
MOZ_TRY(AtomTable(this));
if (useHeader) {
switchToMainBuf();
}
MOZ_ASSERT(isMainBuf());
MOZ_TRY(XDRScript(this, nullptr, nullptr, nullptr, scriptp));
guard.release();
return Ok();
}
template class js::XDRState<XDR_ENCODE>;
template class js::XDRState<XDR_DECODE>;
AutoXDRTree::AutoXDRTree(XDRCoderBase* xdr, AutoXDRTree::Key key)
: key_(key), parent_(this), xdr_(xdr) {
if (key_ != AutoXDRTree::noKey) {
xdr->createOrReplaceSubTree(this);
}
}
AutoXDRTree::~AutoXDRTree() {
if (key_ != AutoXDRTree::noKey) {
xdr_->endSubTree();
}
}
constexpr AutoXDRTree::Key AutoXDRTree::noKey;
constexpr AutoXDRTree::Key AutoXDRTree::noSubTree;
constexpr AutoXDRTree::Key AutoXDRTree::topLevel;
class XDRIncrementalEncoder::DepthFirstSliceIterator {
public:
DepthFirstSliceIterator(JSContext* cx, const SlicesTree& tree)
: stack_(cx), tree_(tree) {}
template <typename SliceFun>
bool iterate(SliceFun&& f) {
MOZ_ASSERT(stack_.empty());
if (!appendChildrenForKey(AutoXDRTree::topLevel)) {
return false;
}
while (!done()) {
SlicesNode::ConstRange& iter = next();
Slice slice = iter.popCopyFront();
// These fields have different meaning, but they should be
// correlated if the tree is well formatted.
MOZ_ASSERT_IF(slice.child == AutoXDRTree::noSubTree, iter.empty());
if (iter.empty()) {
pop();
}
if (!f(slice)) {
return false;
}
// If we are at the end, go back to the parent script.
if (slice.child == AutoXDRTree::noSubTree) {
continue;
}
if (!appendChildrenForKey(slice.child)) {
return false;
}
}
return true;
}
private:
bool done() const { return stack_.empty(); }
SlicesNode::ConstRange& next() { return stack_.back(); }
void pop() { stack_.popBack(); }
MOZ_MUST_USE bool appendChildrenForKey(AutoXDRTree::Key key) {
MOZ_ASSERT(key != AutoXDRTree::noSubTree);
SlicesTree::Ptr p = tree_.lookup(key);
MOZ_ASSERT(p);
return stack_.append(((const SlicesNode&)p->value()).all());
}
Vector<SlicesNode::ConstRange> stack_;
const SlicesTree& tree_;
};
AutoXDRTree::Key XDRIncrementalEncoder::getTopLevelTreeKey() const {
return AutoXDRTree::topLevel;
}
AutoXDRTree::Key XDRIncrementalEncoder::getTreeKey(JSFunction* fun) const {
if (fun->hasBaseScript()) {
static_assert(sizeof(fun->baseScript()->sourceStart()) == 4 &&
sizeof(fun->baseScript()->sourceEnd()) == 4,
"AutoXDRTree key requires BaseScript positions to be uint32");
return uint64_t(fun->baseScript()->sourceStart()) << 32 |
fun->baseScript()->sourceEnd();
}
return AutoXDRTree::noKey;
}
void XDRIncrementalEncoder::createOrReplaceSubTree(AutoXDRTree* child) {
AutoXDRTree* parent = scope_;
child->parent_ = parent;
scope_ = child;
if (oom_) {
return;
}
size_t cursor = buf->cursor();
// End the parent slice here, set the key to the child.
if (parent) {
Slice& last = node_->back();
last.sliceLength = cursor - last.sliceBegin;
last.child = child->key_;
MOZ_ASSERT_IF(uint32_t(parent->key_) != 0,
uint32_t(parent->key_ >> 32) <= uint32_t(child->key_ >> 32) &&
uint32_t(child->key_) <= uint32_t(parent->key_));
}
// Create or replace the part with what is going to be encoded next.
SlicesTree::AddPtr p = tree_.lookupForAdd(child->key_);
SlicesNode tmp;
if (!p) {
// Create a new sub-tree node.
if (!tree_.add(p, child->key_, std::move(tmp))) {
oom_ = true;
return;
}
} else {
// Replace an exisiting sub-tree.
p->value() = std::move(tmp);
}
node_ = &p->value();
// Add content to the root of the new sub-tree,
// i-e an empty slice with no children.
if (!node_->append(Slice{cursor, 0, AutoXDRTree::noSubTree})) {
MOZ_CRASH("SlicesNode have a reserved space of 1.");
}
}
void XDRIncrementalEncoder::endSubTree() {
AutoXDRTree* child = scope_;
AutoXDRTree* parent = child->parent_;
scope_ = parent;
if (oom_) {
return;
}
size_t cursor = buf->cursor();
// End the child sub-tree.
Slice& last = node_->back();
last.sliceLength = cursor - last.sliceBegin;
MOZ_ASSERT(last.child == AutoXDRTree::noSubTree);
// Stop at the top-level.
if (!parent) {
node_ = nullptr;
return;
}
// Restore the parent node.
SlicesTree::Ptr p = tree_.lookup(parent->key_);
node_ = &p->value();
// Append the new slice in the parent node.
if (!node_->append(Slice{cursor, 0, AutoXDRTree::noSubTree})) {
oom_ = true;
return;
}
}
XDRResult XDRIncrementalEncoder::linearize(JS::TranscodeBuffer& buffer) {
if (oom_) {
ReportOutOfMemory(cx());
return fail(JS::TranscodeResult_Throw);
}
// Do not linearize while we are currently adding bytes.
MOZ_ASSERT(scope_ == nullptr);
// Write the size of the atom buffer to the header.
switchToHeaderBuf();
MOZ_TRY(XDRAtomCount(this, &natoms_));
switchToMainBuf();
// Visit the tree parts in a depth first order to linearize the bits.
// Calculate the total length first so we don't incur repeated copying
// and zeroing of memory for large trees.
DepthFirstSliceIterator dfs(cx(), tree_);
size_t totalLength = buffer.length() + header_.length() + atoms_.length();
auto sliceCounter = [&](const Slice& slice) -> bool {
totalLength += slice.sliceLength;
return true;
};
if (!dfs.iterate(sliceCounter)) {
ReportOutOfMemory(cx());
return fail(JS::TranscodeResult_Throw);
};
if (!buffer.reserve(totalLength)) {
ReportOutOfMemory(cx());
return fail(JS::TranscodeResult_Throw);
}
buffer.infallibleAppend(header_.begin(), header_.length());
buffer.infallibleAppend(atoms_.begin(), atoms_.length());
auto sliceCopier = [&](const Slice& slice) -> bool {
// Copy the bytes associated with the current slice to the transcode
// buffer which would be serialized.
MOZ_ASSERT(slice.sliceBegin <= slices_.length());
MOZ_ASSERT(slice.sliceBegin + slice.sliceLength <= slices_.length());
buffer.infallibleAppend(slices_.begin() + slice.sliceBegin,
slice.sliceLength);
return true;
};
if (!dfs.iterate(sliceCopier)) {
ReportOutOfMemory(cx());
return fail(JS::TranscodeResult_Throw);
}
tree_.clearAndCompact();
slices_.clearAndFree();
return Ok();
}
void XDRDecoder::trace(JSTracer* trc) { atomTable_.trace(trc); }
void XDRIncrementalEncoder::trace(JSTracer* trc) { atomMap_.trace(trc); }