Messages in this thread | | | Date | Fri, 24 Apr 2009 19:41:40 +0200 | From | Oleg Nesterov <> | Subject | Re: Q: ptrace_signal() && PTRACE_SETSIGINFO (Was: SIGSTOP && ptrace) |
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On 04/23, Roland McGrath wrote: > > > Yes. PTRACE_SETSIGINFO can change *info if debugger wants something > > special. But then we do: > > > > if (signr != info->si_signo) { > > info->si_signo = signr; > [...] > > Why? If the tracer changes ->exit_code it should know what it does. > > If it uses PTRACE_SETSIGINFO it should know what it does, and update > the siginfo_t to match the signal it passes to PTRACE_CONT et al. > > > Why do we reset *info? > > PTRACE_SETSIGINFO did not always exist, and even now might not be used by a > simple-minded application. If the user is sophisticated, it calls > PTRACE_SETSIGINFO and then passes the signal number to match. If not, it > never calls PTRACE_SETSIGINFO at all, but expects the signal number it > chose to pass in PTRACE_CONT to behave "normally" in the tracee.
OK, understand.
> > But the real question, how can PTRACE_SETSIGINFO change ->si_signo > > (for example, for do_signal_stop(si_signo)) if this in fact is not > > allowed? > > It's allowed. You just have to pass the same value you set in si_signo as > the argument to PTRACE_CONT after you do PTRACE_SETSIGINFO.
Yes, yes, I see. I meant "the tracer can not use signr != ->si_signo", but now I don't see the reason it should.
Oleg.
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