PassRefPtr<ScriptCallStack> createScriptCallStack(JSC::ExecState* exec, size_t maxStackSize)
{
Vector<ScriptCallFrame> frames;
CallFrame* callFrame = exec;
while (true) {
ASSERT(callFrame);
int signedLineNumber;
intptr_t sourceID;
String urlString;
JSValue function;
exec->interpreter()->retrieveLastCaller(callFrame, signedLineNumber, sourceID, urlString, function);
String functionName;
if (function)
functionName = jsCast<JSFunction*>(function)->name(exec);
else {
// Caller is unknown, but if frames is empty we should still add the frame, because
// something called us, and gave us arguments.
if (!frames.isEmpty())
break;
}
unsigned lineNumber = signedLineNumber >= 0 ? signedLineNumber : 0;
frames.append(ScriptCallFrame(functionName, urlString, lineNumber));
if (!function || frames.size() == maxStackSize)
break;
callFrame = callFrame->callerFrame();
}
return ScriptCallStack::create(frames);
}
StackVisitor::StackVisitor(CallFrame* startFrame, VM* vm)
{
m_frame.m_index = 0;
m_frame.m_isWasmFrame = false;
CallFrame* topFrame;
if (startFrame) {
ASSERT(vm);
ASSERT(!vm->topCallFrame || reinterpret_cast<void*>(vm->topCallFrame) != vm->topEntryFrame);
m_frame.m_entryFrame = vm->topEntryFrame;
topFrame = vm->topCallFrame;
if (topFrame && topFrame->isStackOverflowFrame()) {
topFrame = topFrame->callerFrame(m_frame.m_entryFrame);
m_topEntryFrameIsEmpty = (m_frame.m_entryFrame != vm->topEntryFrame);
if (startFrame == vm->topCallFrame)
startFrame = topFrame;
}
} else {
m_frame.m_entryFrame = 0;
topFrame = 0;
}
m_frame.m_callerIsEntryFrame = false;
readFrame(topFrame);
// Find the frame the caller wants to start unwinding from.
while (m_frame.callFrame() && m_frame.callFrame() != startFrame)
gotoNextFrame();
}
JSStringRef JSContextCreateBacktrace(JSContextRef ctx, unsigned maxStackSize)
{
ExecState* exec = toJS(ctx);
JSLock lock(exec);
unsigned count = 0;
UStringBuilder builder;
CallFrame* callFrame = exec;
UString functionName;
if (exec->callee()) {
if (asObject(exec->callee())->inherits(&InternalFunction::s_info)) {
functionName = asInternalFunction(exec->callee())->name(exec);
builder.append("#0 ");
builder.append(functionName);
builder.append("() ");
count++;
}
}
while (true) {
ASSERT(callFrame);
int signedLineNumber;
intptr_t sourceID;
UString urlString;
JSValue function;
UString levelStr = UString::number(count);
exec->interpreter()->retrieveLastCaller(callFrame, signedLineNumber, sourceID, urlString, function);
if (function)
functionName = asFunction(function)->name(exec);
else {
// Caller is unknown, but if frame is empty we should still add the frame, because
// something called us, and gave us arguments.
if (count)
break;
}
unsigned lineNumber = signedLineNumber >= 0 ? signedLineNumber : 0;
if (!builder.isEmpty())
builder.append("\n");
builder.append("#");
builder.append(levelStr);
builder.append(" ");
builder.append(functionName);
builder.append("() at ");
builder.append(urlString);
builder.append(":");
builder.append(UString::number(lineNumber));
if (!function || ++count == maxStackSize)
break;
callFrame = callFrame->callerFrame();
}
return OpaqueJSString::create(builder.toUString()).leakRef();
}
JSObject* addErrorInfo(ExecState* exec, JSObject* error, int line, const SourceCode& source)
{
JSGlobalData* globalData = &exec->globalData();
addErrorInfo(globalData, error, line, source);
JSArray* stack = constructEmptyArray(exec);
CallFrame* frame = exec;
JSObject* stackFrame;
CodeBlock* codeBlock;
UString sourceURL;
UString functionName;
ReturnAddressPtr pc;
while (!frame->hasHostCallFrameFlag()) {
stackFrame = constructEmptyObject(exec);
codeBlock = frame->codeBlock();
// sourceURL
sourceURL = codeBlock->ownerExecutable()->sourceURL();
stackFrame->putWithAttributes(
globalData, Identifier(globalData, sourceURLPropertyName),
jsString(globalData, sourceURL), ReadOnly | DontDelete
);
// line
if (frame != exec) {
line = codeBlock->lineNumberForBytecodeOffset(codeBlock->bytecodeOffset(pc));
}
stackFrame->putWithAttributes(
globalData, Identifier(globalData, linePropertyName),
jsNumber(line), ReadOnly | DontDelete
);
// function
JSObject* function = frame->callee();
if (function && function->inherits(&JSFunction::s_info)) {
functionName = asFunction(function)->calculatedDisplayName(exec);
stackFrame->putWithAttributes(
globalData, Identifier(globalData, functionPropertyName),
jsString(globalData, functionName), ReadOnly | DontDelete
);
}
stack->push(exec, JSValue(stackFrame));
pc = frame->returnPC();
frame = frame->callerFrame();
}
error->putWithAttributes(globalData, Identifier(globalData, stackPropertyName), stack, ReadOnly | DontDelete);
return error;
}
JSValue VM::throwException(ExecState* exec, JSValue error)
{
ASSERT(exec == topCallFrame || exec == exec->lexicalGlobalObject()->globalExec() || exec == exec->dynamicGlobalObject()->globalExec());
Vector<StackFrame> stackTrace;
interpreter->getStackTrace(stackTrace);
m_exceptionStack = RefCountedArray<StackFrame>(stackTrace);
m_exception = error;
if (stackTrace.isEmpty() || !error.isObject())
return error;
JSObject* exception = asObject(error);
StackFrame stackFrame;
for (unsigned i = 0 ; i < stackTrace.size(); ++i) {
stackFrame = stackTrace.at(i);
if (stackFrame.bytecodeOffset)
break;
}
unsigned bytecodeOffset = stackFrame.bytecodeOffset;
if (!hasErrorInfo(exec, exception)) {
// FIXME: We should only really be adding these properties to VM generated exceptions,
// but the inspector currently requires these for all thrown objects.
unsigned line;
unsigned column;
stackFrame.computeLineAndColumn(line, column);
exception->putDirect(*this, Identifier(this, "line"), jsNumber(line), ReadOnly | DontDelete);
exception->putDirect(*this, Identifier(this, "column"), jsNumber(column), ReadOnly | DontDelete);
if (!stackFrame.sourceURL.isEmpty())
exception->putDirect(*this, Identifier(this, "sourceURL"), jsString(this, stackFrame.sourceURL), ReadOnly | DontDelete);
}
if (exception->isErrorInstance() && static_cast<ErrorInstance*>(exception)->appendSourceToMessage()) {
unsigned stackIndex = 0;
CallFrame* callFrame;
for (callFrame = exec; callFrame && !callFrame->codeBlock(); callFrame = callFrame->callerFrame()->removeHostCallFrameFlag())
stackIndex++;
if (callFrame && callFrame->codeBlock()) {
stackFrame = stackTrace.at(stackIndex);
bytecodeOffset = stackFrame.bytecodeOffset;
appendSourceToError(callFrame, static_cast<ErrorInstance*>(exception), bytecodeOffset);
}
}
if (exception->hasProperty(exec, this->propertyNames->stack))
return error;
exception->putDirect(*this, propertyNames->stack, interpreter->stackTraceAsString(topCallFrame, stackTrace), DontEnum);
return error;
}
void ScriptCallStack::fillFrames()
{
if (m_filled || !m_caller)
return;
/*
AJValue function = m_exec->interpreter()->retrieveCaller(m_exec, m_caller);
while (!function.isNull()) {
InternalFunction* internal = asInternalFunction(function);
m_frames.append(ScriptCallFrame(internal->name(m_exec), UString(), 0, ArgList(), 0));
function = m_exec->interpreter()->retrieveCaller(m_exec, internal);
}*/
CallFrame* callFrame = m_exec->callerFrame();
while(callFrame) {
UString functionName;
int tmpLineNO;
intptr_t sourceID;
UString urlString;
AJValue function;
m_exec->interpreter()->retrieveLastCaller(callFrame, tmpLineNO, sourceID, urlString, function);
if (function) {
functionName = asInternalFunction(function)->name(m_exec);
} else {
if (!m_frames.isEmpty())
break;
}
unsigned lineNO = tmpLineNO >= 0 ? tmpLineNO : 0;
m_frames.append(ScriptCallFrame(functionName, urlString, lineNO, ArgList(), 0));
if (!function)
break;
callFrame = callFrame->callerFrame();
}
m_filled = true;
}
void ScriptCallStack::initialize()
{
if (!m_caller || m_initialized)
return;
int signedLineNumber;
intptr_t sourceID;
UString urlString;
JSValue function;
// callFrame must exist if m_caller is not null.
CallFrame* callFrame = m_exec->callerFrame();
while (true) {
ASSERT(callFrame);
m_exec->interpreter()->retrieveLastCaller(callFrame, signedLineNumber, sourceID, urlString, function);
if (!function)
break;
JSFunction* jsFunction = asFunction(function);
unsigned lineNumber = signedLineNumber >= 0 ? signedLineNumber : 0;
m_frames.append(ScriptCallFrame(jsFunction->name(m_exec), urlString, lineNumber, m_exec, 0));
callFrame = callFrame->callerFrame();
}
m_initialized = true;
}
void ShadowChicken::update(VM&, ExecState* exec)
{
if (verbose) {
dataLog("Running update on: ", *this, "\n");
WTFReportBacktrace();
}
const unsigned logCursorIndex = m_logCursor - m_log;
// We need to figure out how to reconcile the current machine stack with our shadow stack. We do
// that by figuring out how much of the shadow stack to pop. We apply three different rules. The
// precise rule relies on the log. The log contains caller frames, which means that we know
// where we bottomed out after making any call. If we bottomed out but made no calls then 'exec'
// will tell us. That's why "highestPointSinceLastTime" will go no lower than exec. The third
// rule, based on comparing to the current real stack, is executed in a later loop.
CallFrame* highestPointSinceLastTime = exec;
for (unsigned i = logCursorIndex; i--;) {
Packet packet = m_log[i];
if (packet.isPrologue()) {
CallFrame* watermark;
if (i && m_log[i - 1].isTail())
watermark = packet.frame;
else
watermark = packet.callerFrame;
highestPointSinceLastTime = std::max(highestPointSinceLastTime, watermark);
}
}
if (verbose)
dataLog(" Highest point since last time: ", RawPointer(highestPointSinceLastTime), "\n");
while (!m_stack.isEmpty() && m_stack.last().frame < highestPointSinceLastTime)
m_stack.removeLast();
if (verbose)
dataLog(" Revised stack: ", listDump(m_stack), "\n");
// It's possible that the top of stack is now tail-deleted. The stack no longer contains any
// frames below the log's high watermark. That means that we just need to look for the first
// occurence of a tail packet for the current stack top.
if (!m_stack.isEmpty()) {
ASSERT(!m_stack.last().isTailDeleted);
for (unsigned i = 0; i < logCursorIndex; ++i) {
Packet& packet = m_log[i];
if (packet.isTail() && packet.frame == m_stack.last().frame) {
m_stack.last().isTailDeleted = true;
break;
}
}
}
if (verbose)
dataLog(" Revised stack: ", listDump(m_stack), "\n");
// The log-based and exec-based rules require that ShadowChicken was enabled. The point of
// ShadowChicken is to give sensible-looking results even if we had not logged. This means that
// we need to reconcile the shadow stack and the real stack by actually looking at the real
// stack. This reconciliation allows the shadow stack to have extra tail-deleted frames, but it
// forbids it from diverging from the real stack on normal frames.
if (!m_stack.isEmpty()) {
Vector<Frame> stackRightNow;
StackVisitor::visit(
exec, [&] (StackVisitor& visitor) -> StackVisitor::Status {
if (visitor->isInlinedFrame())
return StackVisitor::Continue;
bool isTailDeleted = false;
stackRightNow.append(Frame(visitor->callee(), visitor->callFrame(), isTailDeleted));
return StackVisitor::Continue;
});
stackRightNow.reverse();
if (verbose)
dataLog(" Stack right now: ", listDump(stackRightNow), "\n");
unsigned shadowIndex = 0;
unsigned rightNowIndex = 0;
while (shadowIndex < m_stack.size() && rightNowIndex < stackRightNow.size()) {
if (m_stack[shadowIndex].isTailDeleted) {
shadowIndex++;
continue;
}
if (m_stack[shadowIndex] == stackRightNow[rightNowIndex]) {
shadowIndex++;
rightNowIndex++;
continue;
}
break;
}
m_stack.resize(shadowIndex);
if (verbose)
dataLog(" Revised stack: ", listDump(m_stack), "\n");
}
// It's possible that the top stack frame is actually lower than highestPointSinceLastTime.
// Account for that here.
highestPointSinceLastTime = nullptr;
for (unsigned i = m_stack.size(); i--;) {
if (!m_stack[i].isTailDeleted) {
highestPointSinceLastTime = m_stack[i].frame;
break;
}
}
if (verbose)
dataLog(" Highest point since last time: ", RawPointer(highestPointSinceLastTime), "\n");
// Set everything up so that we know where the top frame is in the log.
unsigned indexInLog = logCursorIndex;
auto advanceIndexInLogTo =
[&] (CallFrame* frame, JSObject* callee, CallFrame* callerFrame) -> bool {
if (verbose)
dataLog(" Advancing to frame = ", RawPointer(frame), " from indexInLog = ", indexInLog, "\n");
if (indexInLog > logCursorIndex) {
if (verbose)
dataLog(" Bailing.\n");
return false;
}
unsigned oldIndexInLog = indexInLog;
while (indexInLog--) {
Packet packet = m_log[indexInLog];
// If all callees opt into ShadowChicken, then this search will rapidly terminate when
// we find our frame. But if our frame's callee didn't emit a prologue packet because it
// didn't opt in, then we will keep looking backwards until we *might* find a different
// frame. If we've been given the callee and callerFrame as a filter, then it's unlikely
// that we will hit the wrong frame. But we don't always have that information.
//
// This means it's worth adding other filters. For example, we could track changes in
// stack size. Once we've seen a frame at some height, we're no longer interested in
// frames below that height. Also, we can break as soon as we see a frame higher than
// the one we're looking for.
// FIXME: Add more filters.
// https://bugs.webkit.org/show_bug.cgi?id=155685
if (packet.isPrologue() && packet.frame == frame
&& (!callee || packet.callee == callee)
&& (!callerFrame || packet.callerFrame == callerFrame)) {
if (verbose)
dataLog(" Found at indexInLog = ", indexInLog, "\n");
return true;
}
}
// This is an interesting eventuality. We will see this if ShadowChicken was not
// consistently enabled. We have a choice between:
//
// - Leaving the log index at -1, which will prevent the log from being considered. This is
// the most conservative. It means that we will not be able to recover tail-deleted frames
// from anything that sits above a frame that didn't log a prologue packet. This means
// that everyone who creates prologues must log prologue packets.
//
// - Restoring the log index to what it was before. This prevents us from considering
// whether this frame has tail-deleted frames behind it, but that's about it. The problem
// with this approach is that it might recover tail-deleted frames that aren't relevant.
// I haven't thought about this too deeply, though.
//
// It seems like the latter option is less harmful, so that's what we do.
indexInLog = oldIndexInLog;
if (verbose)
dataLog(" Didn't find it.\n");
return false;
};
Vector<Frame> toPush;
StackVisitor::visit(
exec, [&] (StackVisitor& visitor) -> StackVisitor::Status {
if (visitor->isInlinedFrame()) {
// FIXME: Handle inlining.
// https://bugs.webkit.org/show_bug.cgi?id=155686
return StackVisitor::Continue;
}
CallFrame* callFrame = visitor->callFrame();
if (verbose)
dataLog(" Examining ", RawPointer(callFrame), "\n");
if (!toPush.isEmpty() && indexInLog < logCursorIndex
// This condition protects us from the case where advanceIndexInLogTo didn't find
// anything.
&& m_log[indexInLog].frame == toPush.last().frame) {
if (verbose)
dataLog(" Going to loop through things with indexInLog = ", indexInLog, " and push-stack top = ", toPush.last(), "\n");
for (;;) {
ASSERT(m_log[indexInLog].frame == toPush.last().frame);
// Right now the index is pointing at a prologue packet of the last frame that
// we pushed. Peek behind that packet to see if there is a tail packet. If there
// is one then we know that there is a corresponding prologue packet that will
// tell us about a tail-deleted frame.
if (!indexInLog)
break;
Packet lastPacket = m_log[indexInLog - 1];
if (!lastPacket.isTail()) {
// Last frame that we recorded was not the outcome of a tail call. So, there
// will not be any more deleted frames.
// FIXME: We might want to have a filter here. Consider that this was a tail
// marker for a tail call to something that didn't log anything. It should
// be sufficient to give the tail marker a copy of the caller frame.
// https://bugs.webkit.org/show_bug.cgi?id=155687
break;
}
indexInLog--; // Skip over the tail packet.
if (!advanceIndexInLogTo(lastPacket.frame, nullptr, nullptr)) {
// We were unable to locate the prologue packet for this tail packet. That's
// quite suspect, so give up.
break;
}
Packet packet = m_log[indexInLog];
bool isTailDeleted = true;
toPush.append(Frame(packet.callee, packet.frame, isTailDeleted));
}
}
if (callFrame == highestPointSinceLastTime) {
if (verbose)
dataLog(" Bailing at ", RawPointer(callFrame), " because it's the highest point since last time.\n");
return StackVisitor::Done;
}
advanceIndexInLogTo(callFrame, callFrame->callee(), callFrame->callerFrame());
bool isTailDeleted = false;
toPush.append(Frame(visitor->callee(), callFrame, isTailDeleted));
return StackVisitor::Continue;
});
if (verbose)
dataLog(" Pushing: ", listDump(toPush), "\n");
for (unsigned i = toPush.size(); i--;)
m_stack.append(toPush[i]);
// We want to reset the log. There is a fun corner-case: there could be a tail marker at the end
// of this log. We could make that work by setting isTailDeleted on the top of stack, but that
// would require more corner cases in the complicated reconciliation code above. That code
// already knows how to handle a tail packet at the beginning, so we just leverage that here.
if (logCursorIndex && m_log[logCursorIndex - 1].isTail()) {
m_log[0] = m_log[logCursorIndex - 1];
m_logCursor = m_log + 1;
} else
m_logCursor = m_log;
if (verbose)
dataLog(" After pushing: ", *this, "\n");
// Remove tail frames until the stack is small enough again.
const unsigned stackSizeLimit = Options::shadowChickenStackSizeLimit();
if (m_stack.size() > stackSizeLimit) {
unsigned dstIndex = 0;
unsigned srcIndex = 0;
unsigned size = m_stack.size();
while (srcIndex < m_stack.size()) {
Frame frame = m_stack[srcIndex++];
if (size > stackSizeLimit && frame.isTailDeleted) {
size--;
continue;
}
m_stack[dstIndex++] = frame;
}
RELEASE_ASSERT(dstIndex == size);
m_stack.resize(size);
}
if (verbose)
dataLog(" After clean-up: ", *this, "\n");
}
JSObject* addErrorInfo(ExecState* exec, JSObject* error, int line, const SourceCode& source)
{
JSGlobalData* globalData = &exec->globalData();
addErrorInfo(globalData, error, line, source);
UStringBuilder stackString;
JSArray* stackArray = constructEmptyArray(exec);
CallFrame* frame = exec;
stackString.append(error->toString(exec));
bool functionKnown;
ReturnAddressPtr pc;
while (!frame->hasHostCallFrameFlag()) {
CodeBlock* codeBlock = frame->codeBlock();
JSObject* arrayItem = constructEmptyObject(exec);
stackString.append("\n at ");
JSObject* callee = frame->callee();
UString functionName;
if (callee && callee->inherits(&JSFunction::s_info)) {
functionName = asFunction(callee)->calculatedDisplayName(exec);
functionKnown = !functionName.isEmpty();
} else {
functionKnown = false;
}
if (functionKnown) {
stackString.append(functionName);
stackString.append(" (");
arrayItem->putWithAttributes(
globalData, Identifier(globalData, functionPropertyName),
jsString(globalData, functionName), ReadOnly | DontDelete
);
}
UString sourceURL = codeBlock->ownerExecutable()->sourceURL();
arrayItem->putWithAttributes(
globalData, Identifier(globalData, sourceURLPropertyName),
jsString(globalData, sourceURL), ReadOnly | DontDelete
);
stackString.append(sourceURL);
stackString.append(":");
if (frame != exec) {
line = codeBlock->lineNumberForBytecodeOffset(codeBlock->bytecodeOffset(pc));
}
arrayItem->putWithAttributes(
globalData, Identifier(globalData, linePropertyName),
jsNumber(line), ReadOnly | DontDelete
);
stackString.append(UString::number(line));
if (functionKnown) {
stackString.append(")");
}
stackArray->push(exec, JSValue(arrayItem));
pc = frame->returnPC();
frame = frame->callerFrame();
}
error->putWithAttributes(
globalData, Identifier(globalData, stackPropertyName),
jsString(globalData, stackString.toUString()), ReadOnly | DontDelete
);
error->putWithAttributes(
globalData, Identifier(globalData, "stackArray"),
stackArray, ReadOnly | DontDelete
);
return error;
}