// 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(®s)
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(®s)
if err != nil {
return stopped, err
}
return stoppedBreakpoint, nil
}
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(®s)
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 (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(®s)
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
}