On 05/14/2014 08:49 PM, Pedro Alves wrote: > I realized now that I responded to this. Sorry about that. > > On 01/19/2014 03:29 PM, Oleg Nesterov wrote: >> On 01/19, Sergio Durigan Junior wrote: >>> >>> On Friday, January 10 2014, Oleg Nesterov wrote: >>> >>>> So suppose that gdb does ptrace(PTRACE_SINGLESTEP) and the tracee >>>> executes the "syscall" insn. What it should report? >>> [...] >>>> But what should syscall-exit do? Should it still report SIGSEGV as >>>> it currently does, or should it report _SYSCALL_EXIT instead (if >>>> PTRACE_O_SYSCALL_EXIT of course), or should it report both? >>> >>> Both only if _SYSCALL_EXIT is set. Otherwise, stick to the current >>> behavior, I guess. >> >> OK, both. In which order? Probably _EXIT first. But this looks a bit >> strange. Suppose that the tracee reports _EXIT, then debugger does >> ptrace(PTRACE_CONT), should the tracee report SIGTRAP? > > Seems to me that this should be very much the same as fork/vfork/clone > event handling. Those are triggered by a syscall anyway. So, say: > > - ptrace(PTRACE_SINGLESTEP) > - the tracee executes the "syscall" insn, and the syscall is "clone". > - PTRACE_EVENT_FORK is reported. > - The debugger does ptrace(PTRACE_CONT). > > What should be reported? What is reported now?
Yes, PTRACE_SINGLESTEP looks ambiguous. Just like PTRACE_SYSCALL is. I think we can take it further and add PTRACE_EVENT_SINGLESTEP too, like the patches under discussing which add PTRACE_EVENT_SYSCALL_ENTER,EXIT and therefore do away with the need to use ambiguous PTRACE_SYSCALL. Such API is clearer (I hope) - as long as option is on, user wants to get single-stepping SIGTRAPs after each insn, including syscall insn (in this case, after we return to userspace). -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
