Messages in this thread | | | From | Michael Kerrisk <> | Date | Wed, 21 Sep 2011 07:10:44 +0200 | Subject | Re: [PATCH] man ptrace: add extended description of various ptrace quirks |
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Denys,
On Thu, Jul 21, 2011 at 6:51 PM, Oleg Nesterov <oleg@redhat.com> wrote: > On 07/21, Denys Vlasenko wrote: >> >> Deleted several outright false statements: >> - pid 1 can be traced >> - tracer is not shown as parent in ps output >> - PTRACE_ATTACH is not "the same behavior as if tracee had done >> a PTRACE_TRACEME": PTRACE_ATTACH delivers a SIGSTOP. >> - SIGSTOP _can_ be injected. > > Yes, this is correct, thanks. > >> +Tracer can not assume that tracee ALWAYS ends its life by reporting >> +WIFEXITED(status) or WIFSIGNALED(status). >> +.LP >> +.\" or can it? Do we include such a promise into ptrace API? > > IIRC, we already discussed this... The traced group leader can > disappear during mt-exec, otherwise the tracee can never go away > silently. > >> +Tracer can kill a tracee with ptrace(PTRACE_KILL, pid, 0, 0). This >> +operation is deprecated, use kill(SIGKILL) or tgkill(SIGKILL) instead. >> +The problem with this operation is that it requires tracee to be in >> +signal-delivery-stop, otherwise it may not work (may complete >> +successfully but won't kill the tracee), > > In short, ptrace(PTRACE_KILL) is more or less ptrace(PTRACE_CONT, SIGKILL), > but it always returns 0. IOW, it never worked as decribed in the man > page. And I guess today nobody can explain why PTRACE_KILL exists. > > Oleg.
Does your patch need any revision in the light of Oleg's comments?
Thanks,
Michael
-- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Author of "The Linux Programming Interface"; http://man7.org/tlpi/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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