linux-kernel - Re: RFD: Non-Disruptive Core Dump Infrastructure

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Fri, 13 Sep 2013 22:47:32 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	suzuki@...ibm.com
CC:	kosaki.motohiro@...il.com, jananive@...ux.vnet.ibm.com,
	linux-kernel@...r.kernel.org, jeremy.fitzhardinge@...rix.com,
	d.hatayama@...fujitsu.com, andi@...stfloor.org,
	roland@...k.frob.com, amwang@...hat.com, hch@....de,
	torvalds@...ux-foundation.org, kosaki.motohiro@...fujitsu.com,
	mhiramat@...hat.com, akpm@...ux-foundation.org,
	adobriyan@...il.com, xemul@...allels.com, oleg@...hat.com,
	tj@...nel.org, avagin@...nvz.org, gorcunov@...nvz.org,
	james.hogan@...tec.com, vapier@...too.org, rdunlap@...otime.net,
	eparis@...hat.com, ananth@...ibm.com, aravinda@...ux.vnet.ibm.com,
	tarundeep.singh@...ibm.com
Subject: Re: RFD: Non-Disruptive Core Dump Infrastructure

On 9/12/2013 12:45 AM, Suzuki K. Poulose wrote:
> On 09/12/2013 12:57 AM, KOSAKI Motohiro wrote:
>> (9/3/13 4:39 AM), Janani Venkataraman wrote:
>>> Hello,
>>>
>>> We are working on an infrastructure to create a system core file of a
>>> specific
>>> process at run-time, non-disruptively. It can also be extended to a
>>> case where
>>> a process is able to take a self-core dump.
>>>
>>> gcore, an existing utility creates a core image of the specified
>>> process. It
>>> attaches to the process using gdb and runs the gdb gcore command and then
>>> detaches. In gcore the dump cannot be issued from a signal handler
>>> context as
>>> fork() is not signal safe and moreover it is disruptive in nature as
>>> the gdb
>>> attaches using ptrace which sends a SIGSTOP signal. Hence the gcore
>>> method
>>> cannot be used if the process wants to initiate a self dump.
>>
>> Maybe I'm missing something. But why gcore uses c-level fork()? gcore
>> need to
>> call pthread-at-fork handler? No. gcore need to flush stdio buffer? No.
>>
> Let me clarify. If an application wants to dump itself, it has to do a
> fork() and then exec the gcore with the pid of the appication to
> generate the dump.

Oh, I did think the fork() is used for no application stop dump. But it is
incorrect.

Hmm. However, if an application _itself_ want to dump itself. They can avoid
to use signal handler properly. I'm missing the point of this discussion
completely.

So, I'd keep silence while.

> 
> So, if the application wants to initiate the dump from a signal handler
> context, it may lead to trouble.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/