linux-kernel - Re: [PATCH] kernel, add panic_on

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Message-ID: <54527443.6030007@zytor.com>
Date:	Thu, 30 Oct 2014 10:24:19 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Prarit Bhargava <prarit@...hat.com>, linux-kernel@...r.kernel.org
CC:	Jonathan Corbet <corbet@....net>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>,
	Andi Kleen <ak@...ux.intel.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Fabian Frederick <fabf@...net.be>, vgoyal@...hat.com,
	isimatu.yasuaki@...fujitsu.com, jbaron@...mai.com,
	linux-doc@...r.kernel.org, kexec@...ts.infradead.org,
	linux-api@...r.kernel.org
Subject: Re: [PATCH] kernel, add panic_on_warn

On 10/30/2014 10:03 AM, Prarit Bhargava wrote:
> There have been several times where I have had to rebuild a kernel to
> cause a panic when hitting a WARN() in the code in order to get a crash
> dump from a system.  Sometimes this is easy to do, other times (such as
> in the case of a remote admin) it is not trivial to send new images to the
> user.
> 
> A much easier method would be a switch to change the WARN() over to a
> panic.  This makes debugging easier in that I can now test the actual
> image the WARN() was seen on and I do not have to engage in remote
> debugging.
> 
> This patch adds a panic_on_warn kernel parameter and
> /proc/sys/kernel/panic_on_warn calls panic() in the warn_slowpath_common()
> path.  The function will still print out the location of the warning.
> 
> An example of the panic_on_warn output:
> 
> The first line below is from the WARN_ON() to output the WARN_ON()'s location.
> After that the panic() output is displayed.
> 

There is another very valid use for this: many operators would rather a
machine shuts down than being potentially compromised either
functionally or security-wise.

	-hpa


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