linux-kernel - Re: [PATCH v2] printk: Add a short description string to kmsg

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Message-ID: <10ea2ea1-e692-443e-8b48-ce9884e8b942@redhat.com>
Date: Wed, 3 Jul 2024 09:57:26 +0200
From: Jocelyn Falempe <jfalempe@...hat.com>
To: Kees Cook <kees@...nel.org>
Cc: Michael Ellerman <mpe@...erman.id.au>, Nicholas Piggin
 <npiggin@...il.com>, Christophe Leroy <christophe.leroy@...roup.eu>,
 "Naveen N. Rao" <naveen.n.rao@...ux.ibm.com>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
 "K. Y. Srinivasan" <kys@...rosoft.com>,
 Haiyang Zhang <haiyangz@...rosoft.com>, Wei Liu <wei.liu@...nel.org>,
 Dexuan Cui <decui@...rosoft.com>, Miquel Raynal <miquel.raynal@...tlin.com>,
 Richard Weinberger <richard@....at>, Vignesh Raghavendra <vigneshr@...com>,
 Tony Luck <tony.luck@...el.com>, "Guilherme G. Piccoli"
 <gpiccoli@...lia.com>, Petr Mladek <pmladek@...e.com>,
 Steven Rostedt <rostedt@...dmis.org>, John Ogness
 <john.ogness@...utronix.de>, Sergey Senozhatsky <senozhatsky@...omium.org>,
 Andrew Morton <akpm@...ux-foundation.org>,
 Jani Nikula <jani.nikula@...el.com>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Kefeng Wang <wangkefeng.wang@...wei.com>,
 Thomas Gleixner <tglx@...utronix.de>, Uros Bizjak <ubizjak@...il.com>,
 linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, linux-hyperv@...r.kernel.org,
 linux-mtd@...ts.infradead.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2] printk: Add a short description string to kmsg_dump()

On 02/07/2024 22:29, Kees Cook wrote:
> On Tue, Jul 02, 2024 at 02:26:04PM +0200, Jocelyn Falempe wrote:
>> kmsg_dump doesn't forward the panic reason string to the kmsg_dumper
>> callback.
>> This patch adds a new struct kmsg_dump_detail, that will hold the
>> reason and description, and pass it to the dump() callback.
> 
> Thanks! I like this much better. :)
> 
>>
>> To avoid updating all kmsg_dump() call, it adds a kmsg_dump_desc()
>> function and a macro for backward compatibility.
>>
>> I've written this for drm_panic, but it can be useful for other
>> kmsg_dumper.
>> It allows to see the panic reason, like "sysrq triggered crash"
>> or "VFS: Unable to mount root fs on xxxx" on the drm panic screen.
>>
>> v2:
>>   * Use a struct kmsg_dump_detail to hold the reason and description
>>     pointer, for more flexibility if we want to add other parameters.
>>     (Kees Cook)
>>   * Fix powerpc/nvram_64 build, as I didn't update the forward
>>     declaration of oops_to_nvram()
> 
> The versioning history commonly goes after the "---".

ok, I was not aware of this.
> 
>> [...]
>> diff --git a/include/linux/kmsg_dump.h b/include/linux/kmsg_dump.h
>> index 906521c2329c..65f5a47727bc 100644
>> --- a/include/linux/kmsg_dump.h
>> +++ b/include/linux/kmsg_dump.h
>> @@ -39,6 +39,17 @@ struct kmsg_dump_iter {
>>   	u64	next_seq;
>>   };
>>   
>> +/**
>> + *struct kmsg_dump_detail - kernel crash detail
> 
> Is kern-doc happy with this? I think there is supposed to be a space
> between the "*" and the first word:
> 
>   /**
>    * struct kmsg...
> 
> 
Good catch, yes there is a space missing.

I just checked with "make htmldocs", and in fact 
include/linux/kmsg_dump.h is not indexed for kernel documentation.
And you can't find the definition of struct kmsg_dumper in the online doc.
https://www.kernel.org/doc/html/latest/search.html?q=kmsg_dumper

> Otherwise looks good to me!
> 

Thanks.

As this patch touches different subsystems, do you know on which tree it 
should land ?

-- 

Jocelyn