linux-kernel - Re: [PATCH] man ptrace: add extended description of various ptrace quirks

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Message-ID: <CAKgNAki5q-w+CkQR8iv35F5yEo6FM+0Z-W1LhhhcGJPMJBki7Q@mail.gmail.com>
Date:	Mon, 3 Oct 2011 07:35:16 +0200
From:	Michael Kerrisk <mtk.manpages@...il.com>
To:	Denys Vlasenko <vda.linux@...glemail.com>
Cc:	Oleg Nesterov <oleg@...hat.com>,
	Jan Kratochvil <jan.kratochvil@...hat.com>,
	linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
	linux-man <linux-man@...r.kernel.org>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Chuck Ebbert <76306.1226@...puserve.com>,
	Blaisorblade <blaisorblade@...oo.it>,
	Daniel Jacobowitz <dan@...ian.org>
Subject: Re: [PATCH] man ptrace: add extended description of various ptrace quirks

Hi Denys,

On Fri, Sep 30, 2011 at 4:28 PM, Denys Vlasenko
<vda.linux@...glemail.com> wrote:
> On Thu, Sep 29, 2011 at 9:08 PM, Michael Kerrisk <mtk.manpages@...il.com> wrote:
>> So, I took your patch, and then did a global edit of the page to fix
>> various pieces (in the existing text, as well as do some language
>> clean-ups for the new text). In the process, I found a number of
>> pieces that are still unclear (some in the old text, some in your new
>> text). I also made some changes to your text that I'd like you to
>> check. I've marked each of these with FIXME below. Could you please
>> take a look at the FIXMEs, and write me a comment for each of these.
>> (I appreciate that in some cases, especially for the existing text,
>> you may not have a handy answer Denys, but if you (and others) can
>> give any help, that would be great.)
>>
>> Rather than you writing a new patch to this version of the page, I
>> think it might be easiest if you just replied to the FIXMEs inline
>> below, then I can revise the page in the light of your comments.
>
>       Another group of commands makes the ptrace-stopped  tracee  run.   They
>       have the form:
>
>           ptrace(PTRACE_cmd, pid, 0, sig);
>
>       where  cmd  is  PTRACE_CONT, PTRACE_DETACH, PTRACE_SYSCALL, PTRACE_SIN-
>       GLESTEP, PTRACE_SYSEMU, or PTRACE_SYSEMU_SINGLESTEP.
>
> Cosmetics: cmd is, of course, CONT, DETACH,..., not PTRACE_CONT,
> PTRACE_DETACH...

Yes. But what I did to fix is change the ptrace call to:

      ptrace(cmd, pid, 0, sig);

(Having these constants shown without the "PTRACE_" prefix is a little
confusing.)

>       If the tracee  is
>       in  signal-delivery-stop,  sig  is  the signal to be injected (if it is
>       nonzero).  Otherwise, sig may be ignored.  (Recommended practice is  to
>       always pass 0 in these cases.)
>
> Looks like (my) text in last sentence is confusing. I meant:
> "If you are resterting thracee from a ptrace-stop other than
> signal-delivery-stop, recommended practice is  to always pass
> sig == 0".

Okay -- I made that change.

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/
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