linux-kernel - Re: [RFC PATCH -tip 00/16] in-kernel x86 disassember

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Date:	Tue, 3 Apr 2012 17:39:05 +0900
From:	Masami Hiramatsu <masami.hiramatsu@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
	Huang Ying <ying.huang@...el.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Jason Wessel <jason.wessel@...driver.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RFC PATCH -tip 00/16] in-kernel x86 disassember

2012/4/3 Ingo Molnar <mingo@...nel.org>:
>
> * H. Peter Anvin <hpa@...or.com> wrote:
>
>> On 04/01/2012 09:02 AM, Masami Hiramatsu wrote:
>> > Hi,
>> >
>> > Here is a series of patches of the in-kernel x86 disassembler
>> > for the latest tip tree.
>> > This will show you a pretty disassembled code instead of
>> > just a digital code sequence when you gets a kernel panic etc.
>> > (I know, we also have script/decodecode for the panic use)
>> >
>> > This feature is not for users, but mainly for kernel developers
>> > who can understand disassembly code of x86 ;). This is just like
>> > a joke feature in kernel. (yeah, I spend my spare time for this.
>> > It's my fun :))
>> >
>>
>> This is cool, but I have one major reservation about it: it
>> will make kernel panics take a lot more screen real estate
>> without containing more information, and we already have
>> problems with things scrolling off way too easily.
>
> Yes, I'm not sure we want to do it by default.

Agreed.

>> For that reason I would like to request that this *only*
>> enabled by an explicit command-line option or similar
>> (disasm_oops, maybe?), so that the user has to opt-in.
>
> The existing oops setup knob is an early_param() in
> kernel/panic.c, "oops=".
>
> I'd suggesting extending that in an obvious way. Currently the
> only option that exists is "oops=panic", so a comma delimited
> list of attributes would be the natural extension, allowing:
>
>        oops=panic
>        oops=panic,disasm
>        oops=disasm
>
> Detail: it should do a strncmp(5, str, "disas"), so that every
> usual variant works: oops=disasm, oops=disassemble, etc.

OK, I'll add that.

>
>> [...]  In other words, if *you* are debugging your own kernel,
>> and don't expect to ship oopses off to someone else.
>
> Probably a DEBUG .config option as well, so that distros can
> enable it. OTOH, CONFIG_CMDLINE allows the setting of such
> parameters as well.

This would be good for other parameters, so I think it
should be separately done.

Thank you,

-- 
Masami Hiramatsu
mailto:masami.hiramatsu@...il.com
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