From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Masami Hiramatsu <mhiramat@redhat.com>
Cc: kosaki.motohiro@jp.fujitsu.com, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
lkml <linux-kernel@vger.kernel.org>,
systemtap <systemtap@sources.redhat.com>,
DLE <dle-develop@lists.sourceforge.net>,
Oleg Nesterov <oleg@redhat.com>,
Roland McGrath <roland@redhat.com>,
Jason Baron <jbaron@redhat.com>
Subject: Re: [PATCH v2] [RFC] tracepoint: Add signal coredump tracepoint
Date: Tue, 08 Dec 2009 01:51:00 -0000 [thread overview]
Message-ID: <20091208104324.B589.A69D9226@jp.fujitsu.com> (raw)
In-Reply-To: <4B1D1E7C.8000806@redhat.com>
> KOSAKI Motohiro wrote:
> > 2009/12/3 Masami Hiramatsu<mhiramat@redhat.com>:
> >> Add signal coredump tracepoint which shows signal number,
> >> mm->flags, limits, pointer to file structure and core
> >> file name.
> >>
> >> This tracepoint requirement comes mainly from the viewpoint of
> >> administrators. Since now we have introduced many coredump
> >> configurations (e.g. dumpable, coredump_filter, core_pattern,
> >> etc) and some of them can be modified by users, it will be hard
> >> to know what was actually dumped (or not dumped) after some
> >> problem happened on the system. For example, a process didn't
> >> generated core, coredump doesn't have some sections, etc.
> >> In those cases, the coredump tracepoint can help us to know
> >> why the core file is so big or small, or not generated, by
> >> recording all configurations for all processes on the system.
> >> That will reduce system-administration cost.
> >
> > AFAIK, not-dumped case is important than dump successful case.
> > IOW, admin need to know why the crashed process was not dumped.
>
> Certainly, failure cases are important, but also, the cases
> that dumped-core doesn't or does include some sections
> are also important.
correct.
> > This tracepoint doesn't cover all failure case. especially
> > binfmt->core_dump() et.al.
> > IOW, this tracepoint seems too specialized piped-coredump feature.
>
> Hmm, so would you mean that after calling binfmt->core_dump()
> is better place?
I think your following use-case desired so. if you have unwritten reason, please correct me.
For example, a process didn't generated core, coredump doesn't have
some sections, etc.
> > What do you think this tracepoint's use case?
>
> Frankly to say, our first attempt was tracing mm->flags because
> it can be changed by users without asking, and they sometimes
> ask why core is not perfect or why core file is so big.
>
> Perhaps, covering all of those failure cases and succeed cases,
> gives better information for them. In that case, we might better
> tweak execution(goto) path to leave some error code on retval.
This is enough acceptable to me.
>
> e.g.
> if (IS_ERR(file))
> goto fail_dropcount;
> + retval = -EBADF;
> inode = file->f_path.dentry->d_inode;
> if (inode->i_nlink > 1)
> goto close_fail; /* multiple links - don't dump */
> if (!ispipe && d_unhashed(file->f_path.dentry))
> goto close_fail;
>
> /* AK: actually i see no reason to not allow this for named pipes etc.,
> but keep the previous behaviour for now. */
> if (!ispipe && !S_ISREG(inode->i_mode))
> goto close_fail;
> /*
> * Dont allow local users get cute and trick others to coredump
> * into their pre-created files:
> */
> + retval = -EPERM;
> if (inode->i_uid != current_fsuid())
> goto close_fail;
> + retval = -EINVAL;
> if (!file->f_op)
> goto close_fail;
> if (!file->f_op->write)
> goto close_fail;
> + retval = -EEXIST;
> if (!ispipe && do_truncate(file->f_path.dentry, 0, 0, file) != 0)
> goto close_fail;
>
>
> Thank you,
>
> --
> Masami Hiramatsu
>
> Software Engineer
> Hitachi Computer Products (America), Inc.
> Software Solutions Division
>
> e-mail: mhiramat@redhat.com
>
next prev parent reply other threads:[~2009-12-08 1:51 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <4B128ECF.9020906@redhat.com>
2009-12-02 20:42 ` Masami Hiramatsu
2009-12-03 10:40 ` Ingo Molnar
2009-12-03 11:30 ` Masami Hiramatsu
2009-12-05 7:17 ` Ingo Molnar
2009-12-07 17:19 ` Masami Hiramatsu
2009-12-05 7:18 ` KOSAKI Motohiro
2009-12-07 15:25 ` Masami Hiramatsu
2009-12-08 1:51 ` KOSAKI Motohiro [this message]
2009-12-08 20:35 ` [PATCH v3] " Masami Hiramatsu
2009-12-09 5:34 ` KOSAKI Motohiro
2009-12-09 16:07 ` Masami Hiramatsu
2009-12-09 16:16 ` Masami Hiramatsu
2009-12-09 20:34 ` [PATCH v4] " Masami Hiramatsu
2009-12-10 0:09 ` KOSAKI Motohiro
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