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+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package proc
+
+// TODO(rsc): Imports here after to be in proc.go too in order
+// for deps.bash to get the right answer.
+import (
+ "container/vector"
+ "fmt"
+ "io/ioutil"
+ "os"
+ "runtime"
+ "strconv"
+ "strings"
+ "sync"
+ "syscall"
+)
+
+// This is an implementation of the process tracing interface using
+// Linux's ptrace(2) interface. The implementation is multi-threaded.
+// Each attached process has an associated monitor thread, and each
+// running attached thread has an associated "wait" thread. The wait
+// thread calls wait4 on the thread's TID and reports any wait events
+// or errors via "debug events". The monitor thread consumes these
+// wait events and updates the internally maintained state of each
+// thread. All ptrace calls must run in the monitor thread, so the
+// monitor executes closures received on the debugReq channel.
+//
+// As ptrace's documentation is somewhat light, this is heavily based
+// on information gleaned from the implementation of ptrace found at
+// http://lxr.linux.no/linux+v2.6.30/kernel/ptrace.c
+// http://lxr.linux.no/linux+v2.6.30/arch/x86/kernel/ptrace.c#L854
+// as well as experimentation and examination of gdb's behavior.
+
+const (
+ trace = false
+ traceIP = false
+ traceMem = false
+)
+
+/*
+ * Thread state
+ */
+
+// Each thread can be in one of the following set of states.
+// Each state satisfies
+// isRunning() || isStopped() || isZombie() || isTerminal().
+//
+// Running threads can be sent signals and must be waited on, but they
+// cannot be inspected using ptrace.
+//
+// Stopped threads can be inspected and continued, but cannot be
+// meaningfully waited on. They can be sent signals, but the signals
+// will be queued until they are running again.
+//
+// Zombie threads cannot be inspected, continued, or sent signals (and
+// therefore they cannot be stopped), but they must be waited on.
+//
+// Terminal threads no longer exist in the OS and thus you can't do
+// anything with them.
+type threadState string
+
+const (
+ running threadState = "Running"
+ singleStepping threadState = "SingleStepping" // Transient
+ stopping threadState = "Stopping" // Transient
+ stopped threadState = "Stopped"
+ stoppedBreakpoint threadState = "StoppedBreakpoint"
+ stoppedSignal threadState = "StoppedSignal"
+ stoppedThreadCreate threadState = "StoppedThreadCreate"
+ stoppedExiting threadState = "StoppedExiting"
+ exiting threadState = "Exiting" // Transient (except main thread)
+ exited threadState = "Exited"
+ detached threadState = "Detached"
+)
+
+func (ts threadState) isRunning() bool {
+ return ts == running || ts == singleStepping || ts == stopping
+}
+
+func (ts threadState) isStopped() bool {
+ return ts == stopped || ts == stoppedBreakpoint || ts == stoppedSignal || ts == stoppedThreadCreate || ts == stoppedExiting
+}
+
+func (ts threadState) isZombie() bool { return ts == exiting }
+
+func (ts threadState) isTerminal() bool { return ts == exited || ts == detached }
+
+func (ts threadState) String() string { return string(ts) }
+
+/*
+ * Basic types
+ */
+
+// A breakpoint stores information about a single breakpoint,
+// including its program counter, the overwritten text if the
+// breakpoint is installed.
+type breakpoint struct {
+ pc uintptr
+ olddata []byte
+}
+
+func (bp *breakpoint) String() string {
+ if bp == nil {
+ return "<nil>"
+ }
+ return fmt.Sprintf("%#x", bp.pc)
+}
+
+// bpinst386 is the breakpoint instruction used on 386 and amd64.
+var bpinst386 = []byte{0xcc}
+
+// A debugEvent represents a reason a thread stopped or a wait error.
+type debugEvent struct {
+ *os.Waitmsg
+ t *thread
+ err os.Error
+}
+
+// A debugReq is a request to execute a closure in the monitor thread.
+type debugReq struct {
+ f func() os.Error
+ res chan os.Error
+}
+
+// A transitionHandler specifies a function to be called when a thread
+// changes state and a function to be called when an error occurs in
+// the monitor. Both run in the monitor thread. Before the monitor
+// invokes a handler, it removes the handler from the handler queue.
+// The handler should re-add itself if needed.
+type transitionHandler struct {
+ handle func(*thread, threadState, threadState)
+ onErr func(os.Error)
+}
+
+// A process is a Linux process, which consists of a set of threads.
+// Each running process has one monitor thread, which processes
+// messages from the debugEvents, debugReqs, and stopReq channels and
+// calls transition handlers.
+//
+// To send a message to the monitor thread, first receive from the
+// ready channel. If the ready channel returns true, the monitor is
+// still running and will accept a message. If the ready channel
+// returns false, the monitor is not running (the ready channel has
+// been closed), and the reason it is not running will be stored in err.
+type process struct {
+ pid int
+ threads map[int]*thread
+ breakpoints map[uintptr]*breakpoint
+ ready chan bool
+ debugEvents chan *debugEvent
+ debugReqs chan *debugReq
+ stopReq chan os.Error
+ transitionHandlers vector.Vector
+ err os.Error
+}
+
+// A thread represents a Linux thread in another process that is being
+// debugged. Each running thread has an associated goroutine that
+// waits for thread updates and sends them to the process monitor.
+type thread struct {
+ tid int
+ proc *process
+ // Whether to ignore the next SIGSTOP received by wait.
+ ignoreNextSigstop bool
+
+ // Thread state. Only modified via setState.
+ state threadState
+ // If state == StoppedBreakpoint
+ breakpoint *breakpoint
+ // If state == StoppedSignal or state == Exited
+ signal int
+ // If state == StoppedThreadCreate
+ newThread *thread
+ // If state == Exited
+ exitStatus int
+}
+
+/*
+ * Errors
+ */
+
+type badState struct {
+ thread *thread
+ message string
+ state threadState
+}
+
+func (e *badState) String() string {
+ return fmt.Sprintf("Thread %d %s from state %v", e.thread.tid, e.message, e.state)
+}
+
+type breakpointExistsError Word
+
+func (e breakpointExistsError) String() string {
+ return fmt.Sprintf("breakpoint already exists at PC %#x", e)
+}
+
+type noBreakpointError Word
+
+func (e noBreakpointError) String() string { return fmt.Sprintf("no breakpoint at PC %#x", e) }
+
+type newThreadError struct {
+ *os.Waitmsg
+ wantPid int
+ wantSig int
+}
+
+func (e *newThreadError) String() string {
+ return fmt.Sprintf("newThread wait wanted pid %v and signal %v, got %v and %v", e.Pid, e.StopSignal(), e.wantPid, e.wantSig)
+}
+
+type ProcessExited struct{}
+
+func (p ProcessExited) String() string { return "process exited" }
+
+/*
+ * Ptrace wrappers
+ */
+
+func (t *thread) ptracePeekText(addr uintptr, out []byte) (int, os.Error) {
+ c, err := syscall.PtracePeekText(t.tid, addr, out)
+ if traceMem {
+ fmt.Printf("peek(%#x) => %v, %v\n", addr, out, err)
+ }
+ return c, os.NewSyscallError("ptrace(PEEKTEXT)", err)
+}
+
+func (t *thread) ptracePokeText(addr uintptr, out []byte) (int, os.Error) {
+ c, err := syscall.PtracePokeText(t.tid, addr, out)
+ if traceMem {
+ fmt.Printf("poke(%#x, %v) => %v\n", addr, out, err)
+ }
+ return c, os.NewSyscallError("ptrace(POKETEXT)", err)
+}
+
+func (t *thread) ptraceGetRegs(regs *syscall.PtraceRegs) os.Error {
+ err := syscall.PtraceGetRegs(t.tid, regs)
+ return os.NewSyscallError("ptrace(GETREGS)", err)
+}
+
+func (t *thread) ptraceSetRegs(regs *syscall.PtraceRegs) os.Error {
+ err := syscall.PtraceSetRegs(t.tid, regs)
+ return os.NewSyscallError("ptrace(SETREGS)", err)
+}
+
+func (t *thread) ptraceSetOptions(options int) os.Error {
+ err := syscall.PtraceSetOptions(t.tid, options)
+ return os.NewSyscallError("ptrace(SETOPTIONS)", err)
+}
+
+func (t *thread) ptraceGetEventMsg() (uint, os.Error) {
+ msg, err := syscall.PtraceGetEventMsg(t.tid)
+ return msg, os.NewSyscallError("ptrace(GETEVENTMSG)", err)
+}
+
+func (t *thread) ptraceCont() os.Error {
+ err := syscall.PtraceCont(t.tid, 0)
+ return os.NewSyscallError("ptrace(CONT)", err)
+}
+
+func (t *thread) ptraceContWithSignal(sig int) os.Error {
+ err := syscall.PtraceCont(t.tid, sig)
+ return os.NewSyscallError("ptrace(CONT)", err)
+}
+
+func (t *thread) ptraceStep() os.Error {
+ err := syscall.PtraceSingleStep(t.tid)
+ return os.NewSyscallError("ptrace(SINGLESTEP)", err)
+}
+
+func (t *thread) ptraceDetach() os.Error {
+ err := syscall.PtraceDetach(t.tid)
+ return os.NewSyscallError("ptrace(DETACH)", err)
+}
+
+/*
+ * Logging utilties
+ */
+
+var logLock sync.Mutex
+
+func (t *thread) logTrace(format string, args ...interface{}) {
+ if !trace {
+ return
+ }
+ logLock.Lock()
+ defer logLock.Unlock()
+ fmt.Fprintf(os.Stderr, "Thread %d", t.tid)
+ if traceIP {
+ var regs syscall.PtraceRegs
+ err := t.ptraceGetRegs(&regs)
+ if err == nil {
+ fmt.Fprintf(os.Stderr, "@%x", regs.PC())
+ }
+ }
+ fmt.Fprint(os.Stderr, ": ")
+ fmt.Fprintf(os.Stderr, format, args...)
+ fmt.Fprint(os.Stderr, "\n")
+}
+
+func (t *thread) warn(format string, args ...interface{}) {
+ logLock.Lock()
+ defer logLock.Unlock()
+ fmt.Fprintf(os.Stderr, "Thread %d: WARNING ", t.tid)
+ fmt.Fprintf(os.Stderr, format, args...)
+ fmt.Fprint(os.Stderr, "\n")
+}
+
+func (p *process) logTrace(format string, args ...interface{}) {
+ if !trace {
+ return
+ }
+ logLock.Lock()
+ defer logLock.Unlock()
+ fmt.Fprintf(os.Stderr, "Process %d: ", p.pid)
+ fmt.Fprintf(os.Stderr, format, args...)
+ fmt.Fprint(os.Stderr, "\n")
+}
+
+/*
+ * State utilities
+ */
+
+// someStoppedThread returns a stopped thread from the process.
+// Returns nil if no threads are stopped.
+//
+// Must be called from the monitor thread.
+func (p *process) someStoppedThread() *thread {
+ for _, t := range p.threads {
+ if t.state.isStopped() {
+ return t
+ }
+ }
+ return nil
+}
+
+// someRunningThread returns a running thread from the process.
+// Returns nil if no threads are running.
+//
+// Must be called from the monitor thread.
+func (p *process) someRunningThread() *thread {
+ for _, t := range p.threads {
+ if t.state.isRunning() {
+ return t
+ }
+ }
+ return nil
+}
+
+/*
+ * Breakpoint utilities
+ */
+
+// installBreakpoints adds breakpoints to the attached process.
+//
+// Must be called from the monitor thread.
+func (p *process) installBreakpoints() os.Error {
+ n := 0
+ main := p.someStoppedThread()
+ for _, b := range p.breakpoints {
+ if b.olddata != nil {
+ continue
+ }
+
+ b.olddata = make([]byte, len(bpinst386))
+ _, err := main.ptracePeekText(uintptr(b.pc), b.olddata)
+ if err != nil {
+ b.olddata = nil
+ return err
+ }
+
+ _, err = main.ptracePokeText(uintptr(b.pc), bpinst386)
+ if err != nil {
+ b.olddata = nil
+ return err
+ }
+ n++
+ }
+ if n > 0 {
+ p.logTrace("installed %d/%d breakpoints", n, len(p.breakpoints))
+ }
+
+ return nil
+}
+
+// uninstallBreakpoints removes the installed breakpoints from p.
+//
+// Must be called from the monitor thread.
+func (p *process) uninstallBreakpoints() os.Error {
+ if len(p.threads) == 0 {
+ return nil
+ }
+ n := 0
+ main := p.someStoppedThread()
+ for _, b := range p.breakpoints {
+ if b.olddata == nil {
+ continue
+ }
+
+ _, err := main.ptracePokeText(uintptr(b.pc), b.olddata)
+ if err != nil {
+ return err
+ }
+ b.olddata = nil
+ n++
+ }
+ if n > 0 {
+ p.logTrace("uninstalled %d/%d breakpoints", n, len(p.breakpoints))
+ }
+
+ return nil
+}
+
+/*
+ * Debug event handling
+ */
+
+// wait waits for a wait event from this thread and sends it on the
+// debug events channel for this thread's process. This should be
+// started in its own goroutine when the attached thread enters a
+// running state. The goroutine will exit as soon as it sends a debug
+// event.
+func (t *thread) wait() {
+ for {
+ var ev debugEvent
+ ev.t = t
+ t.logTrace("beginning wait")
+ ev.Waitmsg, ev.err = os.Wait(t.tid, syscall.WALL)
+ if ev.err == nil && ev.Pid != t.tid {
+ panic(fmt.Sprint("Wait returned pid ", ev.Pid, " wanted ", t.tid))
+ }
+ if ev.StopSignal() == syscall.SIGSTOP && t.ignoreNextSigstop {
+ // Spurious SIGSTOP. See Thread.Stop().
+ t.ignoreNextSigstop = false
+ err := t.ptraceCont()
+ if err == nil {
+ continue
+ }
+ // If we failed to continue, just let
+ // the stop go through so we can
+ // update the thread's state.
+ }
+ if !<-t.proc.ready {
+ // The monitor exited
+ break
+ }
+ t.proc.debugEvents <- &ev
+ break
+ }
+}
+
+// setState sets this thread's state, starts a wait thread if
+// necessary, and invokes state transition handlers.
+//
+// Must be called from the monitor thread.
+func (t *thread) setState(newState threadState) {
+ oldState := t.state
+ t.state = newState
+ t.logTrace("state %v -> %v", oldState, newState)
+
+ if !oldState.isRunning() && (newState.isRunning() || newState.isZombie()) {
+ // Start waiting on this thread
+ go t.wait()
+ }
+
+ // Invoke state change handlers
+ handlers := t.proc.transitionHandlers
+ if handlers.Len() == 0 {
+ return
+ }
+
+ t.proc.transitionHandlers = nil
+ for _, h := range handlers {
+ h := h.(*transitionHandler)
+ h.handle(t, oldState, newState)
+ }
+}
+
+// sendSigstop sends a SIGSTOP to this thread.
+func (t *thread) sendSigstop() os.Error {
+ t.logTrace("sending SIGSTOP")
+ err := syscall.Tgkill(t.proc.pid, t.tid, syscall.SIGSTOP)
+ return os.NewSyscallError("tgkill", err)
+}
+
+// stopAsync sends SIGSTOP to all threads in state 'running'.
+//
+// Must be called from the monitor thread.
+func (p *process) stopAsync() os.Error {
+ for _, t := range p.threads {
+ if t.state == running {
+ err := t.sendSigstop()
+ if err != nil {
+ return err
+ }
+ t.setState(stopping)
+ }
+ }
+ return nil
+}
+
+// doTrap handles SIGTRAP debug events with a cause of 0. These can
+// be caused either by an installed breakpoint, a breakpoint in the
+// program text, or by single stepping.
+//
+// TODO(austin) I think we also get this on an execve syscall.
+func (ev *debugEvent) doTrap() (threadState, os.Error) {
+ t := ev.t
+
+ if t.state == singleStepping {
+ return stopped, nil
+ }
+
+ // Hit a breakpoint. Linux leaves the program counter after
+ // the breakpoint. If this is an installed breakpoint, we
+ // need to back the PC up to the breakpoint PC.
+ var regs syscall.PtraceRegs
+ err := t.ptraceGetRegs(&regs)
+ if err != nil {
+ return stopped, err
+ }
+
+ b, ok := t.proc.breakpoints[uintptr(regs.PC())-uintptr(len(bpinst386))]
+ if !ok {
+ // We must have hit a breakpoint that was actually in
+ // the program. Leave the IP where it is so we don't
+ // re-execute the breakpoint instruction. Expose the
+ // fact that we stopped with a SIGTRAP.
+ return stoppedSignal, nil
+ }
+
+ t.breakpoint = b
+ t.logTrace("at breakpoint %v, backing up PC from %#x", b, regs.PC())
+
+ regs.SetPC(uint64(b.pc))
+ err = t.ptraceSetRegs(&regs)
+ if err != nil {
+ return stopped, err
+ }
+ return stoppedBreakpoint, nil
+}
+
+// doPtraceClone handles SIGTRAP debug events with a PTRACE_EVENT_CLONE
+// cause. It initializes the new thread, adds it to the process, and
+// returns the appropriate thread state for the existing thread.
+func (ev *debugEvent) doPtraceClone() (threadState, os.Error) {
+ t := ev.t
+
+ // Get the TID of the new thread
+ tid, err := t.ptraceGetEventMsg()
+ if err != nil {
+ return stopped, err
+ }
+
+ nt, err := t.proc.newThread(int(tid), syscall.SIGSTOP, true)
+ if err != nil {
+ return stopped, err
+ }
+
+ // Remember the thread
+ t.newThread = nt
+
+ return stoppedThreadCreate, nil
+}
+
+// doPtraceExit handles SIGTRAP debug events with a PTRACE_EVENT_EXIT
+// cause. It sets up the thread's state, but does not remove it from
+// the process. A later WIFEXITED debug event will remove it from the
+// process.
+func (ev *debugEvent) doPtraceExit() (threadState, os.Error) {
+ t := ev.t
+
+ // Get exit status
+ exitStatus, err := t.ptraceGetEventMsg()
+ if err != nil {
+ return stopped, err
+ }
+ ws := syscall.WaitStatus(exitStatus)
+ t.logTrace("exited with %v", ws)
+ switch {
+ case ws.Exited():
+ t.exitStatus = ws.ExitStatus()
+ case ws.Signaled():
+ t.signal = ws.Signal()
+ }
+
+ // We still need to continue this thread and wait on this
+ // thread's WIFEXITED event. We'll delete it then.
+ return stoppedExiting, nil
+}
+
+// process handles a debug event. It modifies any thread or process
+// state as necessary, uninstalls breakpoints if necessary, and stops
+// any running threads.
+func (ev *debugEvent) process() os.Error {
+ if ev.err != nil {
+ return ev.err
+ }
+
+ t := ev.t
+ t.exitStatus = -1
+ t.signal = -1
+
+ // Decode wait status.
+ var state threadState
+ switch {
+ case ev.Stopped():
+ state = stoppedSignal
+ t.signal = ev.StopSignal()
+ t.logTrace("stopped with %v", ev)
+ if ev.StopSignal() == syscall.SIGTRAP {
+ // What caused the debug trap?
+ var err os.Error
+ switch cause := ev.TrapCause(); cause {
+ case 0:
+ // Breakpoint or single stepping
+ state, err = ev.doTrap()
+
+ case syscall.PTRACE_EVENT_CLONE:
+ state, err = ev.doPtraceClone()
+
+ case syscall.PTRACE_EVENT_EXIT:
+ state, err = ev.doPtraceExit()
+
+ default:
+ t.warn("Unknown trap cause %d", cause)
+ }
+
+ if err != nil {
+ t.setState(stopped)
+ t.warn("failed to handle trap %v: %v", ev, err)
+ }
+ }
+
+ case ev.Exited():
+ state = exited
+ t.proc.threads[t.tid] = nil, false
+ t.logTrace("exited %v", ev)
+ // We should have gotten the exit status in
+ // PTRACE_EVENT_EXIT, but just in case.
+ t.exitStatus = ev.ExitStatus()
+
+ case ev.Signaled():
+ state = exited
+ t.proc.threads[t.tid] = nil, false
+ t.logTrace("signaled %v", ev)
+ // Again, this should be redundant.
+ t.signal = ev.Signal()
+
+ default:
+ panic(fmt.Sprintf("Unexpected wait status %v", ev.Waitmsg))
+ }
+
+ // If we sent a SIGSTOP to the thread (indicated by state
+ // Stopping), we might have raced with a different type of
+ // stop. If we didn't get the stop we expected, then the
+ // SIGSTOP we sent is now queued up, so we should ignore the
+ // next one we get.
+ if t.state == stopping && ev.StopSignal() != syscall.SIGSTOP {
+ t.ignoreNextSigstop = true
+ }
+
+ // TODO(austin) If we're in state stopping and get a SIGSTOP,
+ // set state stopped instead of stoppedSignal.
+
+ t.setState(state)
+
+ if t.proc.someRunningThread() == nil {
+ // Nothing is running, uninstall breakpoints
+ return t.proc.uninstallBreakpoints()
+ }
+ // Stop any other running threads
+ return t.proc.stopAsync()
+}
+
+// onStop adds a handler for state transitions from running to
+// non-running states. The handler will be called from the monitor
+// thread.
+//
+// Must be called from the monitor thread.
+func (t *thread) onStop(handle func(), onErr func(os.Error)) {
+ // TODO(austin) This is rather inefficient for things like
+ // stepping all threads during a continue. Maybe move
+ // transitionHandlers to the thread, or have both per-thread
+ // and per-process transition handlers.
+ h := &transitionHandler{nil, onErr}
+ h.handle = func(st *thread, old, new threadState) {
+ if t == st && old.isRunning() && !new.isRunning() {
+ handle()
+ } else {
+ t.proc.transitionHandlers.Push(h)
+ }
+ }
+ t.proc.transitionHandlers.Push(h)
+}
+
+/*
+ * Event monitor
+ */
+
+// monitor handles debug events and debug requests for p, exiting when
+// there are no threads left in p.
+func (p *process) monitor() {
+ var err os.Error
+
+ // Linux requires that all ptrace calls come from the thread
+ // that originally attached. Prevent the Go scheduler from
+ // migrating us to other OS threads.
+ runtime.LockOSThread()
+ defer runtime.UnlockOSThread()
+
+ hadThreads := false
+ for err == nil {
+ p.ready <- true
+ select {
+ case event := <-p.debugEvents:
+ err = event.process()
+
+ case req := <-p.debugReqs:
+ req.res <- req.f()
+
+ case err = <-p.stopReq:
+ break
+ }
+
+ if len(p.threads) == 0 {
+ if err == nil && hadThreads {
+ p.logTrace("no more threads; monitor exiting")
+ err = ProcessExited{}
+ }
+ } else {
+ hadThreads = true
+ }
+ }
+
+ // Abort waiting handlers
+ // TODO(austin) How do I stop the wait threads?
+ for _, h := range p.transitionHandlers {
+ h := h.(*transitionHandler)
+ h.onErr(err)
+ }
+
+ // Indicate that the monitor cannot receive any more messages
+ p.err = err
+ close(p.ready)
+}
+
+// do executes f in the monitor thread (and, thus, atomically with
+// respect to thread state changes). f must not block.
+//
+// Must NOT be called from the monitor thread.
+func (p *process) do(f func() os.Error) os.Error {
+ if !<-p.ready {
+ return p.err
+ }
+ req := &debugReq{f, make(chan os.Error)}
+ p.debugReqs <- req
+ return <-req.res
+}
+
+// stopMonitor stops the monitor with the given error. If the monitor
+// is already stopped, does nothing.
+func (p *process) stopMonitor(err os.Error) {
+ if err == nil {
+ panic("cannot stop the monitor with no error")
+ }
+ if <-p.ready {
+ p.stopReq <- err
+ }
+}
+
+/*
+ * Public thread interface
+ */
+
+func (t *thread) Regs() (Regs, os.Error) {
+ var regs syscall.PtraceRegs
+
+ err := t.proc.do(func() os.Error {
+ if !t.state.isStopped() {
+ return &badState{t, "cannot get registers", t.state}
+ }
+ return t.ptraceGetRegs(&regs)
+ })
+ if err != nil {
+ return nil, err
+ }
+
+ setter := func(r *syscall.PtraceRegs) os.Error {
+ return t.proc.do(func() os.Error {
+ if !t.state.isStopped() {
+ return &badState{t, "cannot get registers", t.state}
+ }
+ return t.ptraceSetRegs(r)
+ })
+ }
+ return newRegs(&regs, setter), nil
+}
+
+func (t *thread) Peek(addr Word, out []byte) (int, os.Error) {
+ var c int
+
+ err := t.proc.do(func() os.Error {
+ if !t.state.isStopped() {
+ return &badState{t, "cannot peek text", t.state}
+ }
+
+ var err os.Error
+ c, err = t.ptracePeekText(uintptr(addr), out)
+ return err
+ })
+
+ return c, err
+}
+
+func (t *thread) Poke(addr Word, out []byte) (int, os.Error) {
+ var c int
+
+ err := t.proc.do(func() os.Error {
+ if !t.state.isStopped() {
+ return &badState{t, "cannot poke text", t.state}
+ }
+
+ var err os.Error
+ c, err = t.ptracePokeText(uintptr(addr), out)
+ return err
+ })
+
+ return c, err
+}
+
+// stepAsync starts this thread single stepping. When the single step
+// is complete, it will send nil on the given channel. If an error
+// occurs while setting up the single step, it returns that error. If
+// an error occurs while waiting for the single step to complete, it
+// sends that error on the channel.
+func (t *thread) stepAsync(ready chan os.Error) os.Error {
+ if err := t.ptraceStep(); err != nil {
+ return err
+ }
+ t.setState(singleStepping)
+ t.onStop(func() { ready <- nil },
+ func(err os.Error) { ready <- err })
+ return nil
+}
+
+func (t *thread) Step() os.Error {
+ t.logTrace("Step {")
+ defer t.logTrace("}")
+
+ ready := make(chan os.Error)
+
+ err := t.proc.do(func() os.Error {
+ if !t.state.isStopped() {
+ return &badState{t, "cannot single step", t.state}
+ }
+ return t.stepAsync(ready)
+ })
+ if err != nil {
+ return err
+ }
+
+ err = <-ready
+ return err
+}
+
+// TODO(austin) We should probably get this via C's strsignal.
+var sigNames = [...]string{
+ "SIGEXIT", "SIGHUP", "SIGINT", "SIGQUIT", "SIGILL",
+ "SIGTRAP", "SIGABRT", "SIGBUS", "SIGFPE", "SIGKILL",
+ "SIGUSR1", "SIGSEGV", "SIGUSR2", "SIGPIPE", "SIGALRM",
+ "SIGTERM", "SIGSTKFLT", "SIGCHLD", "SIGCONT", "SIGSTOP",
+ "SIGTSTP", "SIGTTIN", "SIGTTOU", "SIGURG", "SIGXCPU",
+ "SIGXFSZ", "SIGVTALRM", "SIGPROF", "SIGWINCH", "SIGPOLL",
+ "SIGPWR", "SIGSYS",
+}
+
+// sigName returns the symbolic name for the given signal number. If
+// the signal number is invalid, returns "<invalid>".
+func sigName(signal int) string {
+ if signal < 0 || signal >= len(sigNames) {
+ return "<invalid>"
+ }
+ return sigNames[signal]
+}
+
+func (t *thread) Stopped() (Cause, os.Error) {
+ var c Cause
+ err := t.proc.do(func() os.Error {
+ switch t.state {
+ case stopped:
+ c = Stopped{}
+
+ case stoppedBreakpoint:
+ c = Breakpoint(t.breakpoint.pc)
+
+ case stoppedSignal:
+ c = Signal(sigName(t.signal))
+
+ case stoppedThreadCreate:
+ c = &ThreadCreate{t.newThread}
+
+ case stoppedExiting, exiting, exited:
+ if t.signal == -1 {
+ c = &ThreadExit{t.exitStatus, ""}
+ } else {
+ c = &ThreadExit{t.exitStatus, sigName(t.signal)}
+ }
+
+ default:
+ return &badState{t, "cannot get stop cause", t.state}
+ }
+ return nil
+ })
+ if err != nil {
+ return nil, err
+ }
+
+ return c, nil
+}
+
+func (p *process) Threads() []Thread {
+ var res []Thread
+
+ p.do(func() os.Error {
+ res = make([]Thread, len(p.threads))
+ i := 0
+ for _, t := range p.threads {
+ // Exclude zombie threads.
+ st := t.state
+ if st == exiting || st == exited || st == detached {
+ continue
+ }
+
+ res[i] = t
+ i++
+ }
+ res = res[0:i]
+ return nil
+ })
+ return res
+}
+
+func (p *process) AddBreakpoint(pc Word) os.Error {
+ return p.do(func() os.Error {
+ if t := p.someRunningThread(); t != nil {
+ return &badState{t, "cannot add breakpoint", t.state}
+ }
+ if _, ok := p.breakpoints[uintptr(pc)]; ok {
+ return breakpointExistsError(pc)
+ }
+ p.breakpoints[uintptr(pc)] = &breakpoint{pc: uintptr(pc)}
+ return nil
+ })
+}
+
+func (p *process) RemoveBreakpoint(pc Word) os.Error {
+ return p.do(func() os.Error {
+ if t := p.someRunningThread(); t != nil {
+ return &badState{t, "cannot remove breakpoint", t.state}
+ }
+ if _, ok := p.breakpoints[uintptr(pc)]; !ok {
+ return noBreakpointError(pc)
+ }
+ p.breakpoints[uintptr(pc)] = nil, false
+ return nil
+ })
+}
+
+func (p *process) Continue() os.Error {
+ // Single step any threads that are stopped at breakpoints so
+ // we can reinstall breakpoints.
+ var ready chan os.Error
+ count := 0
+
+ err := p.do(func() os.Error {
+ // We make the ready channel big enough to hold all
+ // ready message so we don't jam up the monitor if we
+ // stop listening (e.g., if there's an error).
+ ready = make(chan os.Error, len(p.threads))
+
+ for _, t := range p.threads {
+ if !t.state.isStopped() {
+ continue
+ }
+
+ // We use the breakpoint map directly here
+ // instead of checking the stop cause because
+ // it could have been stopped at a breakpoint
+ // for some other reason, or the breakpoint
+ // could have been added since it was stopped.
+ var regs syscall.PtraceRegs
+ err := t.ptraceGetRegs(&regs)
+ if err != nil {
+ return err
+ }
+ if b, ok := p.breakpoints[uintptr(regs.PC())]; ok {
+ t.logTrace("stepping over breakpoint %v", b)
+ if err := t.stepAsync(ready); err != nil {
+ return err
+ }
+ count++
+ }
+ }
+ return nil
+ })
+ if err != nil {
+ p.stopMonitor(err)
+ return err
+ }
+
+ // Wait for single stepping threads
+ for count > 0 {
+ err = <-ready
+ if err != nil {
+ p.stopMonitor(err)
+ return err
+ }
+ count--
+ }
+
+ // Continue all threads
+ err = p.do(func() os.Error {
+ if err := p.installBreakpoints(); err != nil {
+ return err
+ }
+
+ for _, t := range p.threads {
+ var err os.Error
+ switch {
+ case !t.state.isStopped():
+ continue
+
+ case t.state == stoppedSignal && t.signal != syscall.SIGSTOP && t.signal != syscall.SIGTRAP:
+ t.logTrace("continuing with signal %d", t.signal)
+ err = t.ptraceContWithSignal(t.signal)
+
+ default:
+ t.logTrace("continuing")
+ err = t.ptraceCont()
+ }
+ if err != nil {
+ return err
+ }
+ if t.state == stoppedExiting {
+ t.setState(exiting)
+ } else {
+ t.setState(running)
+ }
+ }
+ return nil
+ })
+ if err != nil {
+ // TODO(austin) Do we need to stop the monitor with
+ // this error atomically with the do-routine above?
+ p.stopMonitor(err)
+ return err
+ }
+
+ return nil
+}
+
+func (p *process) WaitStop() os.Error {
+ // We need a non-blocking ready channel for the case where all
+ // threads are already stopped.
+ ready := make(chan os.Error, 1)
+
+ err := p.do(func() os.Error {
+ // Are all of the threads already stopped?
+ if p.someRunningThread() == nil {
+ ready <- nil
+ return nil
+ }
+
+ // Monitor state transitions
+ h := &transitionHandler{}
+ h.handle = func(st *thread, old, new threadState) {
+ if !new.isRunning() {
+ if p.someRunningThread() == nil {
+ ready <- nil
+ return
+ }
+ }
+ p.transitionHandlers.Push(h)
+ }
+ h.onErr = func(err os.Error) { ready <- err }
+ p.transitionHandlers.Push(h)
+ return nil
+ })
+ if err != nil {
+ return err
+ }
+
+ return <-ready
+}
+
+func (p *process) Stop() os.Error {
+ err := p.do(func() os.Error { return p.stopAsync() })
+ if err != nil {
+ return err
+ }
+
+ return p.WaitStop()
+}
+
+func (p *process) Detach() os.Error {
+ if err := p.Stop(); err != nil {
+ return err
+ }
+
+ err := p.do(func() os.Error {
+ if err := p.uninstallBreakpoints(); err != nil {
+ return err
+ }
+
+ for pid, t := range p.threads {
+ if t.state.isStopped() {
+ // We can't detach from zombies.
+ if err := t.ptraceDetach(); err != nil {
+ return err
+ }
+ }
+ t.setState(detached)
+ p.threads[pid] = nil, false
+ }
+ return nil
+ })
+ // TODO(austin) Wait for monitor thread to exit?
+ return err
+}
+
+// newThread creates a new thread object and waits for its initial
+// signal. If cloned is true, this thread was cloned from a thread we
+// are already attached to.
+//
+// Must be run from the monitor thread.
+func (p *process) newThread(tid int, signal int, cloned bool) (*thread, os.Error) {
+ t := &thread{tid: tid, proc: p, state: stopped}
+
+ // Get the signal from the thread
+ // TODO(austin) Thread might already be stopped if we're attaching.
+ w, err := os.Wait(tid, syscall.WALL)
+ if err != nil {
+ return nil, err
+ }
+ if w.Pid != tid || w.StopSignal() != signal {
+ return nil, &newThreadError{w, tid, signal}
+ }
+
+ if !cloned {
+ err = t.ptraceSetOptions(syscall.PTRACE_O_TRACECLONE | syscall.PTRACE_O_TRACEEXIT)
+ if err != nil {
+ return nil, err
+ }
+ }
+
+ p.threads[tid] = t
+
+ return t, nil
+}
+
+// attachThread attaches a running thread to the process.
+//
+// Must NOT be run from the monitor thread.
+func (p *process) attachThread(tid int) (*thread, os.Error) {
+ p.logTrace("attaching to thread %d", tid)
+ var thr *thread
+ err := p.do(func() os.Error {
+ errno := syscall.PtraceAttach(tid)
+ if errno != 0 {
+ return os.NewSyscallError("ptrace(ATTACH)", errno)
+ }
+
+ var err os.Error
+ thr, err = p.newThread(tid, syscall.SIGSTOP, false)
+ return err
+ })
+ return thr, err
+}
+
+// attachAllThreads attaches to all threads in a process.
+func (p *process) attachAllThreads() os.Error {
+ taskPath := "/proc/" + strconv.Itoa(p.pid) + "/task"
+ taskDir, err := os.Open(taskPath, os.O_RDONLY, 0)
+ if err != nil {
+ return err
+ }
+ defer taskDir.Close()
+
+ // We stop threads as we attach to them; however, because new
+ // threads can appear while we're looping over all of them, we
+ // have to repeatly scan until we know we're attached to all
+ // of them.
+ for again := true; again; {
+ again = false
+
+ tids, err := taskDir.Readdirnames(-1)
+ if err != nil {
+ return err
+ }
+
+ for _, tidStr := range tids {
+ tid, err := strconv.Atoi(tidStr)
+ if err != nil {
+ return err
+ }
+ if _, ok := p.threads[tid]; ok {
+ continue
+ }
+
+ _, err = p.attachThread(tid)
+ if err != nil {
+ // There could have been a race, or
+ // this process could be a zobmie.
+ statFile, err2 := ioutil.ReadFile(taskPath + "/" + tidStr + "/stat")
+ if err2 != nil {
+ switch err2 := err2.(type) {
+ case *os.PathError:
+ if err2.Error == os.ENOENT {
+ // Raced with thread exit
+ p.logTrace("raced with thread %d exit", tid)
+ continue
+ }
+ }
+ // Return the original error
+ return err
+ }
+
+ statParts := strings.Split(string(statFile), " ", 4)
+ if len(statParts) > 2 && statParts[2] == "Z" {
+ // tid is a zombie
+ p.logTrace("thread %d is a zombie", tid)
+ continue
+ }
+
+ // Return the original error
+ return err
+ }
+ again = true
+ }
+ }
+
+ return nil
+}
+
+// newProcess creates a new process object and starts its monitor thread.
+func newProcess(pid int) *process {
+ p := &process{
+ pid: pid,
+ threads: make(map[int]*thread),
+ breakpoints: make(map[uintptr]*breakpoint),
+ ready: make(chan bool, 1),
+ debugEvents: make(chan *debugEvent),
+ debugReqs: make(chan *debugReq),
+ stopReq: make(chan os.Error),
+ }
+
+ go p.monitor()
+
+ return p
+}
+
+// Attach attaches to process pid and stops all of its threads.
+func Attach(pid int) (Process, os.Error) {
+ p := newProcess(pid)
+
+ // Attach to all threads
+ err := p.attachAllThreads()
+ if err != nil {
+ p.Detach()
+ // TODO(austin) Detach stopped the monitor already
+ //p.stopMonitor(err);
+ return nil, err
+ }
+
+ return p, nil
+}
+
+// ForkExec forks the current process and execs argv0, stopping the
+// new process after the exec syscall. See os.ForkExec for additional
+// details.
+func ForkExec(argv0 string, argv []string, envv []string, dir string, fd []*os.File) (Process, os.Error) {
+ p := newProcess(-1)
+
+ // Create array of integer (system) fds.
+ intfd := make([]int, len(fd))
+ for i, f := range fd {
+ if f == nil {
+ intfd[i] = -1
+ } else {
+ intfd[i] = f.Fd()
+ }
+ }
+
+ // Fork from the monitor thread so we get the right tracer pid.
+ err := p.do(func() os.Error {
+ pid, errno := syscall.PtraceForkExec(argv0, argv, envv, dir, intfd)
+ if errno != 0 {
+ return &os.PathError{"fork/exec", argv0, os.Errno(errno)}
+ }
+ p.pid = pid
+
+ // The process will raise SIGTRAP when it reaches execve.
+ _, err := p.newThread(pid, syscall.SIGTRAP, false)
+ return err
+ })
+ if err != nil {
+ p.stopMonitor(err)
+ return nil, err
+ }
+
+ return p, nil
+}
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