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976 lines (830 loc) · 39.4 KB
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/*
* Copyright (C) 2025 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.
*
* THIS SOFTWARE IS PROVIDED BY APPLE INC. ``AS IS'' 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
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#include "config.h"
#include "WasmExecutionHandler.h"
#if ENABLE(WEBASSEMBLY_DEBUGGER)
WTF_ALLOW_UNSAFE_BUFFER_USAGE_BEGIN
#include "JSWebAssemblyInstance.h"
#include "JSWebAssemblyModule.h"
#include "Options.h"
#include "SubspaceInlines.h"
#include "VM.h"
#include "VMManager.h"
#include "WasmBreakpointManager.h"
#include "WasmCallee.h"
#include "WasmDebugServer.h"
#include "WasmDebugServerUtilities.h"
#include "WasmExceptionType.h"
#include "WasmIPIntGenerator.h"
#include "WasmIPIntSlowPaths.h"
#include "WasmModuleManager.h"
#include "WasmOps.h"
#include "WasmVirtualAddress.h"
#include <cstdlib>
#include <cstring>
#if OS(WINDOWS)
#include <winsock2.h>
#else
#include <sys/socket.h>
#endif
#include <wtf/Assertions.h>
#include <wtf/DataLog.h>
#include <wtf/HexNumber.h>
#include <wtf/TZoneMallocInlines.h>
#include <wtf/text/StringBuilder.h>
#include <wtf/text/WTFString.h>
namespace JSC {
namespace Wasm {
WTF_MAKE_TZONE_ALLOCATED_IMPL(ExecutionHandler);
struct StopReasonInfo {
String reasonString;
StringView reasonSuffix;
};
// GDB RSP stop reply: T<AA> where AA is the POSIX signal number in two-digit hex.
// "reason:<suffix>" is an LLDB extension (not in the GDB RSP spec).
// Reference: https://sourceware.org/gdb/current/onlinedocs/gdb/Stop-Reply-Packets.html
static String signalStopString(int signo)
{
return makeString('T', hex(signo, 2, WTF::Uppercase));
}
// Maps DebugState::Reason to GDB RSP T-packet signal and reason suffix.
// Reference: https://sourceware.org/gdb/current/onlinedocs/gdb/Stop-Reply-Packets.html
static inline StopReasonInfo stopReasonToInfo(const DebugState& state)
{
RELEASE_ASSERT(state.stopReason.has_value());
switch (*state.stopReason) {
case DebugState::Reason::Interrupted:
return { signalStopString(SIGSTOP), "signal"_s };
case DebugState::Reason::Breakpoint:
return { signalStopString(SIGTRAP), "breakpoint"_s };
case DebugState::Reason::Step:
return { signalStopString(SIGTRAP), "trace"_s };
case DebugState::Reason::WasmTrap:
return { signalStopString(SIGTRAP), "exception"_s };
}
RELEASE_ASSERT_NOT_REACHED();
}
ExecutionHandler::ExecutionHandler(DebugServer& debugServer, ModuleManager& instanceManager)
: m_debugServer(debugServer)
, m_moduleManager(instanceManager)
, m_breakpointManager(makeUnique<BreakpointManager>())
{
}
void ExecutionHandler::stopTheWorld(VM& debuggee, StopTheWorldEvent event)
{
auto info = VMManager::info();
dataLogLnIf(Options::verboseWasmDebugger(), "[stopTheWorld] debuggee:", RawPointer(&debuggee), " event:", event, " ", info);
{
Locker locker { m_lock };
switch (event) {
case StopTheWorldEvent::WasmStepIntoSiteReached:
RELEASE_ASSERT(m_debuggee == info.targetVM && info.targetVM == info.servingVM && info.worldMode == VMManager::Mode::RunOne);
break;
case StopTheWorldEvent::WasmProgramStop:
RELEASE_ASSERT(info.worldMode != VMManager::Mode::Stopped);
break;
default:
RELEASE_ASSERT_NOT_REACHED();
break;
}
// Wait for previous resume all to prevent reenter notifyVMStop.
while (m_awaitingResumeNotification)
m_debuggeeContinue.wait(m_lock);
m_debuggee = &debuggee;
}
VMManager::requestStopAll(VMManager::StopReason::WasmDebugger);
VMManager::singleton().notifyVMStop(debuggee, event);
}
DebuggerTrapStatus ExecutionHandler::handleDebuggerTrapIfNeeded(CallFrame* callFrame, JSWebAssemblyInstance* instance, IPIntCallee* callee, uint8_t* pc, uint8_t* mc, IPInt::IPIntStackEntry* stack, Wasm::ExceptionType exceptionType)
{
VM& debuggee = instance->vm();
if (exceptionType == Wasm::ExceptionType::Unreachable && hasBreakpoints()) {
VirtualAddress address = VirtualAddress::toVirtual(instance, callee->functionIndex(), pc);
if (RefPtr breakpoint = m_breakpointManager->findBreakpoint(address)) {
debuggee.debugState()->setBreakpointStopData(breakpoint->type, address, breakpoint->originalBytecode, pc, mc, stack, callee, instance, callFrame);
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][handleDebuggerTrapIfNeeded] Breakpoint at ", *breakpoint, " with ", *debuggee.debugState()->stopData);
stopTheWorld(debuggee, StopTheWorldEvent::WasmProgramStop);
return DebuggerTrapStatus::ResolvedByDebugger; // Don't throw; resume execution at this breakpoint
}
}
if (!m_debugServer.isDebuggerReady())
return DebuggerTrapStatus::NotResolvedByDebugger; // Throw; no debugger connected
if (exceptionType == Wasm::ExceptionType::StackOverflow || exceptionType == Wasm::ExceptionType::Termination) {
// Prologue trap: pc/mc/stack are caller's, not the overflowing function's.
// handleTrapsIfNeeded() may have already processed a NeedStopTheWorld trap,
// serving a debugger stop and clearing stopData via clearStop(); re-establish
// prologue context if needed.
if (!debuggee.debugState()->stopData)
debuggee.debugState()->setPrologueStopData(instance, callee, callFrame);
debuggee.debugState()->stopReason = DebugState::Reason::WasmTrap;
debuggee.debugState()->stopData->wasmTrapType = exceptionType;
} else
debuggee.debugState()->setTrapStopData(callee, instance, callFrame, pc, mc, stack, exceptionType);
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][handleDebuggerTrapIfNeeded] Wasm trap at ", *debuggee.debugState()->stopData);
stopTheWorld(debuggee, StopTheWorldEvent::WasmProgramStop);
return DebuggerTrapStatus::NotResolvedByDebugger; // Throw; trap was reported, now propagate it
}
ExecutionHandler::ResumeMode ExecutionHandler::stopCode(Locker<Lock>& locker, StopTheWorldEvent event)
{
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][Stop] Start with event:", event);
auto notifyDebuggerOfStop = [&]() WTF_REQUIRES_LOCK(m_lock) {
if (m_debuggerState == DebuggerState::ContinueRequested) {
sendStopReply(locker);
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][Stop] Sent a stop reply and waiting...");
} else {
RELEASE_ASSERT(requiresStopConfirmation());
m_debuggerContinue.notifyOne(); // Notify debugger that code stopped.
}
};
// Handle stop event and notify debugger
switch (event) {
case StopTheWorldEvent::VMStopped:
case StopTheWorldEvent::VMCreated:
case StopTheWorldEvent::VMActivated:
case StopTheWorldEvent::AtomicsWaitBlocked:
RELEASE_ASSERT(m_debuggerState == DebuggerState::InterruptRequested || m_debuggerState == DebuggerState::SwitchRequested);
m_breakpointManager->clearAllOneTimeBreakpoints();
notifyDebuggerOfStop();
break;
case StopTheWorldEvent::WasmProgramStop:
RELEASE_ASSERT(m_debuggerState == DebuggerState::StepRequested || m_debuggerState == DebuggerState::ContinueRequested || m_debuggerState == DebuggerState::SwitchRequested);
// FIXME: For module-load stops (isNewModuleLoad), step breakpoints should be preserved
// so the in-progress step can complete after LLDB resumes. Clearing them here silently
// cancels any active step. This also affects future LLDB expression evaluation, which can
// trigger module loads internally and should not interrupt a step.
m_breakpointManager->clearAllOneTimeBreakpoints();
notifyDebuggerOfStop();
break;
case StopTheWorldEvent::WasmStepIntoSiteReached:
RELEASE_ASSERT(m_debuggerState == DebuggerState::StepRequested);
m_debuggerContinue.notifyOne(); // Notify that breakpoint is set.
break;
default:
RELEASE_ASSERT_NOT_REACHED();
}
// Wait for debugger command
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][Stop] Waiting for debugger command...");
m_debuggeeContinue.wait(locker); // Wait for resume mode to be set.
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][Stop] Unblocked and running...");
// Determine resume mode
if (m_debuggerState == DebuggerState::SwitchRequested)
return ResumeMode::Switch;
// Defer debugger notification until after VMs resume to prevent interrupt() race.
if (m_debuggerState == DebuggerState::ContinueRequested)
m_awaitingResumeNotification = true;
return (m_debuggerState == DebuggerState::StepRequested) ? ResumeMode::One : ResumeMode::All;
}
StopTheWorldStatus ExecutionHandler::handleStopTheWorld(VM& debuggee, StopTheWorldEvent event)
{
dataLogLnIf(Options::verboseWasmDebugger(), "[STW] handleStopTheWorld() begin with event:", event, " debuggee:", RawPointer(&debuggee));
Locker locker { m_lock };
selectDebuggeeIfNeeded(debuggee);
RELEASE_ASSERT(m_debuggee);
// If debuggee differs from candidate, switch to debuggee.
if (m_debuggee != &debuggee) {
dataLogLnIf(Options::verboseWasmDebugger(), "[STW] Context switch to debuggee VM");
return STW_CONTEXT_SWITCH(m_debuggee);
}
// Stop the code and let debugger decide resume mode.
ExecutionHandler::ResumeMode mode = stopCode(locker, event);
switch (mode) {
case ExecutionHandler::ResumeMode::One:
return STW_RESUME_ONE(m_debuggee);
case ExecutionHandler::ResumeMode::All:
m_debuggee = nullptr;
return STW_RESUME_ALL();
case ExecutionHandler::ResumeMode::Switch:
RELEASE_ASSERT(m_debuggee != &debuggee);
RELEASE_ASSERT(debuggee.debugState()->isStopped);
RELEASE_ASSERT(m_debuggee->debugState()->isStopped);
return STW_CONTEXT_SWITCH(m_debuggee);
}
RELEASE_ASSERT_NOT_REACHED();
return STW_RESUME_ALL();
}
void ExecutionHandler::selectDebuggeeIfNeeded(VM& fallbackVM) WTF_REQUIRES_LOCK(m_lock)
{
if (m_debuggee) {
dataLogLnIf(Options::verboseWasmDebugger(), "[STW] Already have debuggee VM:", RawPointer(m_debuggee));
return;
}
// Prefer any non-system call.
// FIXME: We should prioritize with WASM traps > non-system calls > system calls.
VM* selectedVM = nullptr;
VMManager::forEachVM([&](VM& vm) {
auto* debugState = vm.debugState();
if (vm.debugState()->isStopped && !debugState->isStoppedAtSystemCall()) {
selectedVM = &vm;
return IterationStatus::Done;
}
return IterationStatus::Continue;
});
m_debuggee = selectedVM ? selectedVM : &fallbackVM;
dataLogLnIf(Options::verboseWasmDebugger(), "[STW] Selected debuggee VM:", RawPointer(m_debuggee));
}
// Called by VMManager when ALL VMs are stopped at safe points.
// Returns resume mode (ResumeOne/ResumeAll/ContextSwitch) to coordinate execution.
StopTheWorldStatus wasmDebuggerOnStopCallback(VM& debuggee, StopTheWorldEvent event)
{
dataLogLnIf(Options::verboseWasmDebugger(), "[STW] Callback invoked with event:", event);
auto& server = DebugServer::singleton();
if (!server.hasDebugger()) {
dataLogLnIf(Options::verboseWasmDebugger(), "[STW] Not connected, resuming all");
return STW_RESUME_ALL();
}
return server.execution().handleStopTheWorld(debuggee, event);
}
void ExecutionHandler::handlePostResume()
{
Locker locker { m_lock };
if (takeAwaitingResumeNotification()) {
dataLogLnIf(Options::verboseWasmDebugger(), "[PostResume] Notify debugger to continue");
m_debuggerContinue.notifyOne(); // Notify that resume is complete.
m_debuggeeContinue.notifyAll(); // Release resume barrier for VMs blocked in stopTheWorld().
}
}
// Called by VMManager after ALL VMs have resumed (when m_numberOfStoppedVMs reaches 0).
// This is the safe point to notify debugger that resume is complete and release barriers in stopTheWorld().
void wasmDebuggerOnResumeCallback()
{
auto& server = DebugServer::singleton();
if (!server.hasDebugger()) {
dataLogLnIf(Options::verboseWasmDebugger(), "[STW][PostResume] Not connected, resuming all");
return;
}
server.execution().handlePostResume();
}
void ExecutionHandler::resume()
{
Locker locker { m_lock };
resumeImpl(locker);
}
void ExecutionHandler::resumeImpl(Locker<Lock>& locker)
{
RELEASE_ASSERT(Thread::currentSingleton().uid() == debugServerThreadId());
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Continue] Start");
RELEASE_ASSERT(debuggeeState()->isStopped);
m_debuggerState = DebuggerState::ContinueRequested;
m_debuggeeContinue.notifyOne(); // Notify debuggee VM with resume all command.
// Wait for resume to complete to prevent interrupt() from acquiring lock before VMs resume.
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Continue] Notified code to continue and waiting...");
m_debuggerContinue.wait(locker); // Wait for resume to complete.
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Continue] Confirmed that code is running...");
}
void ExecutionHandler::notifyDebuggerOfNewModule(VM& vm)
{
vm.debugState()->isNewModuleLoad = true;
stopTheWorld(vm, StopTheWorldEvent::WasmProgramStop);
}
static inline VM* findVM(uint64_t vmId)
{
VM* result = nullptr;
VMManager::forEachVM([&](VM& vm) {
if (vm.debugState()->isStopped && vmId == vm.identifier().toUInt64()) {
result = &vm;
return IterationStatus::Done;
}
return IterationStatus::Continue;
});
return result;
}
void ExecutionHandler::switchTarget(uint64_t vmId)
{
RELEASE_ASSERT(Thread::currentSingleton().uid() == debugServerThreadId());
Locker locker { m_lock };
VM* newDebuggee = findVM(vmId);
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][SwitchVM] current debuggee=", RawPointer(m_debuggee), " new debuggee=", RawPointer(newDebuggee));
if (m_debuggee == newDebuggee)
return;
RELEASE_ASSERT(debuggeeState()->isStopped);
m_debuggee = newDebuggee;
m_debuggerState = DebuggerState::SwitchRequested;
m_debuggeeContinue.notifyOne(); // Notify to switch VM context.
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][SwitchVM] Notified code to continue and switch VM, waiting...");
m_debuggerContinue.wait(locker); // Wait for new debuggee VM to stop.
RELEASE_ASSERT(debuggeeState()->isStopped);
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][SwitchVM] Code is stopped");
}
void ExecutionHandler::interrupt()
{
RELEASE_ASSERT(Thread::currentSingleton().uid() == debugServerThreadId());
Locker locker { m_lock };
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Interrupt] Start");
// LLDB implements interrupt flood prevention: once LLDB sends the first interrupt packet,
// no matter how many Ctrl+C the user types, LLDB will not send additional interrupt packets
// until it receives a stop reply. This prevents packet flooding and ensures clean protocol behavior.
// Our WebKit implementation handles each interrupt request by activating StopWorld via VM traps.
{
RELEASE_ASSERT(!m_debuggee || !debuggeeState()->isStopped);
m_debuggerState = DebuggerState::InterruptRequested;
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Interrupt] Calling VMManager::requestStopAll()...");
VMManager::singleton().requestStopAll(VMManager::StopReason::WasmDebugger);
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Interrupt] VMManager::requestStopAll() returned");
}
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Interrupt] Notified code to stop, waiting...");
m_debuggerContinue.wait(locker); // Wait for debuggee VM to stop.
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Interrupt] Wait completed, sending stop reply...");
sendStopReply(locker);
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Interrupt] Code is stopped and debugger replied");
}
void ExecutionHandler::step()
{
RELEASE_ASSERT(Thread::currentSingleton().uid() == debugServerThreadId());
Locker locker { m_lock };
auto* state = debuggeeState();
RELEASE_ASSERT(m_debuggerState == DebuggerState::Replied && state->isStopped);
bool resumeAll = false;
if (state->isStoppedAtSystemCall() || state->isStoppedDueToWasmTrap()) {
// There is no valid next WASM instruction to step to in either case.
// For traps (including StackOverflow at prologue), execution unwinds back to JS —
// resuming all is the right behavior.
resumeAll = true;
} else if (state->isStoppedAtBytecode())
resumeAll = stepAtBytecode(locker, state);
else {
RELEASE_ASSERT(state->isStoppedAtPrologue());
setBreakpointAtEntry(state->stopData->instance, state->stopData->callee.get(), Breakpoint::Type::Step);
}
if (resumeAll) {
resumeImpl(locker);
return;
}
RELEASE_ASSERT(m_breakpointManager->hasOneTimeBreakpoints());
m_debuggerState = DebuggerState::StepRequested;
m_debuggeeContinue.notifyOne(); // Notify to resume until next breakpoint.
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Step] Notified code to continue and expected a stop, waiting...");
m_debuggerContinue.wait(locker); // Wait for one-time breakpoint hit.
sendStopReply(locker);
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Step] Code is stopped and debugger replied");
}
bool ExecutionHandler::stepAtBytecode(Locker<Lock>& locker, DebugState* state)
{
RELEASE_ASSERT(state->isStoppedAtBytecode());
auto& stopData = *state->stopData;
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Step] Start with ", stopData);
uint8_t* currentPC = stopData.pc;
auto setStepBreakpoint = [&](const uint8_t* nextPC) WTF_REQUIRES_LOCK(m_lock) {
VirtualAddress nextAddress = VirtualAddress(stopData.address.value() + (nextPC - currentPC));
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][Step][SetOneTimeBreakpoint] current PC=", RawPointer(currentPC), "(", stopData.address, "), next PC=", RawPointer(nextPC), "(", nextAddress, ")");
if (m_breakpointManager->findBreakpoint(nextAddress))
return;
m_breakpointManager->setBreakpoint(nextAddress, Breakpoint::create(const_cast<uint8_t*>(nextPC), Breakpoint::Type::Step));
};
auto setStepBreakpointAtCaller = [&]() WTF_REQUIRES_LOCK(m_lock) {
uint8_t* returnPC = nullptr;
VirtualAddress virtualReturnPC;
if (getWasmReturnPC(stopData.callFrame, returnPC, virtualReturnPC))
m_breakpointManager->setBreakpoint(virtualReturnPC, Breakpoint::create(const_cast<uint8_t*>(returnPC), Breakpoint::Type::Step));
};
auto setStepBreakpointsFromDebugInfo = [&]() WTF_REQUIRES_LOCK(m_lock) {
const auto& moduleInfo = stopData.instance->moduleInformation();
auto functionIndex = stopData.callee->functionIndex();
uint32_t offset = stopData.address.offset();
const auto* nextInstructions = moduleInfo.debugInfo->ensureFunctionDebugInfo(functionIndex).findNextInstructions(offset);
RELEASE_ASSERT(nextInstructions, "Didn't find nextInstructions");
uint8_t* const basePC = stopData.pc - offset;
for (uint32_t nextOffset : *nextInstructions)
setStepBreakpoint(basePC + nextOffset);
};
switch (stopData.originalBytecode) {
case Nop:
case Drop:
case Select:
setStepBreakpoint(currentPC + 1);
break;
case End:
if (currentPC != stopData.callee->bytecodeEnd()) {
setStepBreakpoint(currentPC + 1);
break;
}
[[fallthrough]];
case Return:
setStepBreakpointAtCaller();
break;
// Step-into design: Set event flag and let runtime resolve callee/handler naturally to avoid duplicating
// complex resolution logic. Runtime calls setStepIntoBreakpointForCall/Throw() with resolved target.
// FIXME: Resolve target once in step() and cache for runtime reuse to eliminate two-phase protocol.
case Throw:
case Rethrow:
case ThrowRef:
case Delegate:
state->setStepIntoThrow();
break;
case TailCall:
case TailCallIndirect:
case TailCallRef:
// Tail calls: Set step-into event for Wasm callees, then set breakpoint at caller
// (for non-Wasm callees or as fallback, since tail calls don't return to next instruction).
state->setStepIntoCall();
setStepBreakpointAtCaller();
break;
case Call:
case CallIndirect:
case CallRef:
// Regular calls: Set step-into event for Wasm callees, then fallthrough to
// set step-over breakpoint at next instruction (for non-Wasm callees or as fallback).
state->setStepIntoCall();
[[fallthrough]];
default: {
setStepBreakpointsFromDebugInfo();
break;
}
}
if (state->hasStepIntoEvent()) {
m_debuggerState = DebuggerState::StepRequested;
m_debuggeeContinue.notifyOne(); // Notify to run and set breakpoints if possible.
m_debuggerContinue.wait(locker); // Wait for call/throw one-time breakpoint to be registered.
}
// If no one-time breakpoints registered, or stopped at memory.atomic.wait (must resumeAll
// so notifier threads can run), then resume all VMs instead of using RunOne.
return !m_breakpointManager->hasOneTimeBreakpoints() || state->isAtomicsWaitStop();
}
void ExecutionHandler::setStepIntoBreakpointForCall(VM& callerVM, CalleeBits boxedCallee, JSWebAssemblyInstance* calleeInstance)
{
if (!callerVM.debugState()->takeStepIntoCall())
return;
[&]() {
Locker locker { m_lock };
RELEASE_ASSERT(m_debuggee == &callerVM);
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][StepIntoEvent] Start for call");
RELEASE_ASSERT(m_debuggerState == DebuggerState::StepRequested);
RELEASE_ASSERT(calleeInstance);
if (!boxedCallee.isNativeCallee())
return;
RefPtr wasmCallee = downcast<Wasm::Callee>(boxedCallee.asNativeCallee());
if (wasmCallee->compilationMode() != Wasm::CompilationMode::IPIntMode)
return;
// Set breakpoint at the callee's entry point.
// Use calleeInstance (not caller's instance) because callee may be in a different Wasm module instance.
RELEASE_ASSERT(&calleeInstance->vm() == &callerVM);
setBreakpointAtEntry(calleeInstance, downcast<IPIntCallee>(wasmCallee.get()), Breakpoint::Type::Step);
}();
stopTheWorld(callerVM, StopTheWorldEvent::WasmStepIntoSiteReached);
}
void ExecutionHandler::setStepIntoBreakpointForThrow(VM& throwVM)
{
if (!throwVM.debugState()->takeStepIntoThrow())
return;
[&]() {
Locker locker { m_lock };
RELEASE_ASSERT(m_debuggee == &throwVM);
dataLogLnIf(Options::verboseWasmDebugger(), "[Code][StepIntoEvent] Start for throw");
RELEASE_ASSERT(m_debuggerState == DebuggerState::StepRequested);
if (!throwVM.callFrameForCatch)
return;
if (!throwVM.callFrameForCatch->callee().isNativeCallee())
return;
RefPtr wasmCallee = downcast<Wasm::Callee>(throwVM.callFrameForCatch->callee().asNativeCallee());
if (wasmCallee->compilationMode() != Wasm::CompilationMode::IPIntMode)
return;
RefPtr catchCallee = downcast<IPIntCallee>(wasmCallee.get());
ASSERT(std::holds_alternative<uintptr_t>(throwVM.targetInterpreterPCForThrow));
uintptr_t handlerOffset = std::get<uintptr_t>(throwVM.targetInterpreterPCForThrow);
const uint8_t* handlerPC = catchCallee->bytecode() + handlerOffset;
if (*handlerPC == static_cast<uint8_t>(Wasm::OpType::TryTable) && throwVM.targetInterpreterMetadataPCForThrow) {
const uint8_t* metadataPtr = catchCallee->metadata() + throwVM.targetInterpreterMetadataPCForThrow;
metadataPtr += sizeof(IPInt::CatchMetadata);
const IPInt::BlockMetadata* blockMetadata = reinterpret_cast<const IPInt::BlockMetadata*>(metadataPtr);
handlerPC = handlerPC + blockMetadata->deltaPC;
}
// Set breakpoint at the exception handler.
// Use catchInstance (not thrower's instance) because exception may be caught in a different Wasm module instance.
JSWebAssemblyInstance* catchInstance = throwVM.callFrameForCatch->wasmInstance();
RELEASE_ASSERT(&catchInstance->vm() == &throwVM);
setBreakpointAtPC(catchInstance, catchCallee->functionIndex(), Breakpoint::Type::Step, handlerPC);
}();
stopTheWorld(throwVM, StopTheWorldEvent::WasmStepIntoSiteReached);
}
void ExecutionHandler::setBreakpointAtEntry(JSWebAssemblyInstance* instance, IPIntCallee* callee, Breakpoint::Type type)
{
setBreakpointAtPC(instance, callee->functionIndex(), type, callee->bytecode());
}
void ExecutionHandler::setBreakpointAtPC(JSWebAssemblyInstance* instance, FunctionCodeIndex functionIndex, Breakpoint::Type type, const uint8_t* pc)
{
RELEASE_ASSERT(pc);
VirtualAddress address = VirtualAddress::toVirtual(instance, functionIndex, pc);
if (m_breakpointManager->findBreakpoint(address))
return;
m_breakpointManager->setBreakpoint(address, Breakpoint::create(const_cast<uint8_t*>(pc), type));
}
void ExecutionHandler::setBreakpoint(StringView packet)
{
if (packet.isEmpty())
return;
// Parse packet format: Z0,<address>,<length>
if (packet.isEmpty() || packet[0] != 'Z') {
sendErrorReply(ProtocolError::InvalidPacket);
return;
}
StringView params = packet.substring(1);
auto parts = splitWithDelimiters(params, ",,"_s);
if (parts.size() != 3) {
sendErrorReply(ProtocolError::InvalidPacket);
return;
}
uint32_t type = parseDecimal(parts[0]);
VirtualAddress address = VirtualAddress(parseHex(parts[1]));
uint32_t length = parseDecimal(parts[2]);
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][SetBreakpoint] Setting breakpoint: type=", static_cast<int>(type), ", address=", address, ", length=", length);
// Only support type 0 (software breakpoint)
if (type) {
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][SetBreakpoint] Unsupported breakpoint type: ", static_cast<int>(type));
sendErrorReply(ProtocolError::UnknownCommand);
return;
}
VirtualAddress::Type addressType = address.type();
if (addressType != VirtualAddress::Type::Module) {
dataLogLnIf(Options::verboseWasmDebugger(), "[ExecutionHandler] Breakpoint must be in module code region, got type: ", (int)addressType);
sendErrorReply(ProtocolError::InvalidAddress);
return;
}
if (m_breakpointManager->findBreakpoint(address)) {
dataLogLnIf(Options::verboseWasmDebugger(), "[ExecutionHandler] Breakpoint already exists at address: ", address);
sendErrorReply(ProtocolError::InvalidAddress);
return;
}
uint8_t* pc = address.toPhysicalPC(m_moduleManager);
if (!pc) {
dataLogLnIf(Options::verboseWasmDebugger(), "[ExecutionHandler] Failed to convert virtual address to physical: ", address);
sendErrorReply(ProtocolError::InvalidAddress);
return;
}
m_breakpointManager->setBreakpoint(address, Breakpoint::create(pc, Breakpoint::Type::Regular));
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger][SetBreakpoint] Successfully set breakpoint at ", address, " (physical: ", RawPointer(pc), ", original: 0x", hex(*pc, 2, Lowercase), ")");
sendReplyOK();
}
void ExecutionHandler::removeBreakpoint(StringView packet)
{
if (packet.isEmpty())
return;
// Format: z0,<address>,<length>
if (packet.isEmpty() || packet[0] != 'z') {
sendErrorReply(ProtocolError::InvalidPacket);
return;
}
StringView params = packet.substring(1);
auto parts = splitWithDelimiters(params, ",,"_s);
if (parts.size() != 3) {
sendErrorReply(ProtocolError::InvalidPacket);
return;
}
uint32_t type = parseDecimal(parts[0]);
VirtualAddress address = VirtualAddress(parseHex(parts[1]));
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Removing breakpoint: type=", static_cast<int>(type), ", address=", address);
// Only support type 0 (software breakpoint)
if (type) {
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Unsupported breakpoint type for removal: ", static_cast<int>(type));
sendErrorReply(ProtocolError::UnknownCommand);
return;
}
// Delegate to breakpoint manager
if (m_breakpointManager->removeBreakpoint(address)) {
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Breakpoint removed successfully from ", address);
sendReplyOK();
} else {
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Breakpoint not found at address: ", address);
sendErrorReply(ProtocolError::InvalidAddress);
}
}
void ExecutionHandler::handleThreadStopInfo(StringView packet)
{
// Format: qThreadStopInfo<thread-id-in-hex>
// Parse the thread ID
StringView threadIdStr = packet.substring(strlen("qThreadStopInfo"));
uint64_t vmId = parseHex(threadIdStr);
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Handling qThreadStopInfo for thread: ", vmId);
Locker locker { m_lock };
sendStopReplyForThread(locker, vmId);
}
static uint64_t NODELETE getStopPC(const DebugState& state)
{
if (state.isStoppedAtSystemCall())
return VirtualAddress(VirtualAddress::INVALID_BASE).value();
RELEASE_ASSERT(state.stopData);
return state.stopData->address;
}
static String getThreadName(const DebugState& state, uint64_t vmId)
{
StringView stateName;
if (state.isStoppedAtPrologue())
stateName = "wasm-prologue"_s;
else if (state.isStoppedAtBytecode())
stateName = "wasm-call"_s;
else {
RELEASE_ASSERT(state.isStoppedAtSystemCall());
stateName = "system-call"_s;
}
return makeString(stateName, " tid:0x"_s, hex(vmId, Lowercase));
}
struct ThreadInfo {
uint64_t vmId;
uint64_t pc;
String name;
StringView stopReason;
};
void ExecutionHandler::sendStopReply(AbstractLocker& locker) WTF_REQUIRES_LOCK(m_lock)
{
sendStopReplyForThread(locker, m_debuggee->identifier().toUInt64());
}
void ExecutionHandler::sendStopReplyForThread(AbstractLocker& locker, uint64_t vmId) WTF_REQUIRES_LOCK(m_lock)
{
VM* vm = findVM(vmId);
if (!vm) {
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] sendStopReplyForThread: thread ", vmId, " not found");
sendErrorReply(ProtocolError::InvalidAddress);
return;
}
DebugState* state = vm->debugState();
if (!state) {
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] sendStopReplyForThread: thread ", vmId, " not found");
sendErrorReply(ProtocolError::InvalidAddress);
return;
}
RELEASE_ASSERT(state->isStopped);
// Collect all stopped threads; swap event thread to index 0 so thread-pcs[i] aligns with threads[i].
Vector<ThreadInfo> allThreads;
VMManager::forEachVM([&](VM& vm) {
auto* state = vm.debugState();
if (!state->isStopped)
return IterationStatus::Continue;
uint64_t tid = vm.identifier().toUInt64();
allThreads.append({ tid, getStopPC(*state), getThreadName(*state, tid), stopReasonToInfo(*state).reasonSuffix });
if (tid == vmId)
std::swap(allThreads[0], allThreads.last());
return IterationStatus::Continue;
});
// A "passive thread" is a VM that was collaterally stopped when the world was halted (its
// stopReason set to Interrupted by setStopped()), as opposed to the debuggee thread that
// actually triggered the stop event (breakpoint/step/trap/interrupt/new-module-load).
// Passive threads get signal 0 so LLDB's ShouldSelect() returns false for them, allowing
// the event thread to win thread selection in HandleProcessStateChangedEvent.
bool isPassiveThread = state->stopReason == DebugState::Reason::Interrupted && m_debuggee && vmId != m_debuggee->identifier().toUInt64();
auto stopInfo = isPassiveThread
? StopReasonInfo { signalStopString(0), "signal"_s }
: stopReasonToInfo(*state);
// Build packet with target thread
StringBuilder reply;
reply.append(stopInfo.reasonString);
reply.append("thread:"_s, hex(vmId, Lowercase), ';');
reply.append("name:"_s, getThreadName(*state, vmId), ';');
// All thread IDs
reply.append("threads:"_s);
for (size_t i = 0; i < allThreads.size(); ++i) {
if (i > 0)
reply.append(',');
reply.append(hex(allThreads[i].vmId, Lowercase));
}
reply.append(';');
// All thread PCs
reply.append("thread-pcs:"_s);
for (size_t i = 0; i < allThreads.size(); ++i) {
if (i > 0)
reply.append(',');
reply.append(hex(allThreads[i].pc, 16, Lowercase));
}
reply.append(';');
reply.append("00:"_s, toNativeEndianHex(getStopPC(*state)), ';');
reply.append("reason:"_s, stopInfo.reasonSuffix, ';');
// Append library:; to prompt LLDB to re-query qXfer:libraries:read when there are pending
// library changes: (1) new-module-load stop, (2) piggybacked on any natural stop when a module
// was loaded but no dedicated stop fired yet, (3) module removal via unregisterModule().
// Gated on isDebuggerReady() to avoid sending library:; in the ? reply before the initial
// qXfer:libraries:read handshake completes.
if (m_moduleManager.needsLibraryRequery() && m_debugServer.isDebuggerReady()) {
reply.append("library:;"_s);
// Include a human-readable description only for dedicated new-module-load stops.
if (state->isNewModuleLoad) {
RELEASE_ASSERT(state->isStoppedAtSystemCall());
reply.append("description:"_s);
StringBuilder description;
description.append("loaded new wasm module with ids: "_s);
auto ids = m_moduleManager.unnotifiedModuleIds();
for (size_t i = 0; i < ids.size(); ++i) {
if (i)
description.append(", "_s);
description.append(ids[i]);
}
for (UChar c : StringView(description.toString()).codeUnits())
reply.append(hex(static_cast<uint8_t>(c), 2, Lowercase));
reply.append(';');
}
}
// For trap stops, include a hex-encoded description so LLDB can display the trap reason.
if (state->isStoppedDueToWasmTrap()) {
reply.append("description:"_s);
for (UChar c : StringView(Wasm::errorMessageForExceptionType(*state->stopData->wasmTrapType)).codeUnits())
reply.append(hex(static_cast<uint8_t>(c), 2, Lowercase));
reply.append(';');
}
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Sending stop reply: target thread="_s, hex(vmId), ", total threads="_s, allThreads.size(), ", packet="_s, reply.toString());
sendReplyImpl(locker, reply.toString());
}
void ExecutionHandler::sendReply(StringView reply)
{
Locker locker { m_lock };
sendReplyImpl(locker, reply);
}
void ExecutionHandler::sendReplyImpl(AbstractLocker&, StringView reply) WTF_REQUIRES_LOCK(m_lock)
{
uint8_t checksum = 0;
for (auto character : reply.codeUnits())
checksum += character;
String packet = makeString('$', reply, '#', hex(checksum, 2, Lowercase));
#if ENABLE(REMOTE_INSPECTOR)
if (m_debugServer.isRWIMode()) {
RELEASE_ASSERT(!!m_debugServer.m_rwiResponseHandler);
if (m_debugServer.m_rwiResponseHandler(packet)) {
m_debuggerState = DebuggerState::Replied;
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Sent reply via RWI: ", packet);
} else
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Failed to send packet via RWI: ", packet);
return;
}
#endif
CString packetData = packet.utf8();
int sent = static_cast<int>(send(m_debugServer.m_clientSocket, packetData.data(), packetData.length(), 0));
if (sent < 0)
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Failed to send packet: ", packetData.data(), " sent: ", sent);
else {
m_debuggerState = DebuggerState::Replied;
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Sent reply: ", packetData.data());
}
}
void ExecutionHandler::reset()
{
Locker locker { m_lock };
dataLogLnIf(Options::verboseWasmDebugger(), "[Debugger] Handling client disconnection in ExecutionHandler");
// Clear before resuming: resumeImpl() transiently releases m_lock, and the
// VM must not re-hit a breakpoint in that window.
m_breakpointManager->clearAllBreakpoints();
if (m_debuggee && debuggeeState()->isStopped)
resumeImpl(locker);
m_debuggerState = DebuggerState::Replied;
takeAwaitingResumeNotification();
m_debuggee = nullptr;
}
void ExecutionHandler::sendReplyOK() { m_debugServer.sendReplyOK(); }
void ExecutionHandler::sendErrorReply(ProtocolError error) { m_debugServer.sendErrorReply(error); }
DebugState* ExecutionHandler::debuggeeState() const { return m_debuggee->debugState(); }
DebugState* ExecutionHandler::debuggeeStateForTest() const
{
Locker locker { m_lock };
RELEASE_ASSERT(m_debuggee);
return m_debuggee->debugState();
}
bool ExecutionHandler::hasBreakpoints() const
{
return m_breakpointManager && m_breakpointManager->hasBreakpoints();
}
String ExecutionHandler::callStackStringFor(uint64_t vmId)
{
Locker locker { m_lock };
VM* targetVM = m_debuggee;
RELEASE_ASSERT(targetVM);
if (targetVM->identifier().toUInt64() != vmId)
targetVM = findVM(vmId);
if (!targetVM) {
dataLogLnIf(Options::verboseWasmDebugger(), "[ExecutionHandler] callStackStringFor: thread ", vmId, " not found");
return String();
}
auto* state = targetVM->debugState();
RELEASE_ASSERT(state->isStopped);
if (state->stopData) {
auto& stopData = *state->stopData;
RELEASE_ASSERT(stopData.callFrame);
Vector<FrameInfo> frames = collectCallStack(stopData.address, stopData.callFrame, *targetVM);
StringBuilder result;
for (const auto& frame : frames)
result.append(toNativeEndianHex(frame.address));
dataLogLnIf(Options::verboseWasmDebugger(), "[ExecutionHandler] callStackStringFor: collected ", frames.size(), " frames");
return result.toString();
}
uint64_t pc = getStopPC(*state);
return toNativeEndianHex(pc);
}
} // namespace Wasm
} // namespace JSC
WTF_ALLOW_UNSAFE_BUFFER_USAGE_END
#endif // ENABLE(WEBASSEMBLY_DEBUGGER)