linux-kernel - Re: [PATCH v5] ARM: Use generic BUG() handler

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Date:	Thu, 11 Aug 2011 23:36:08 -0700
From:	Simon Glass <sjg@...gle.com>
To:	Stephen Boyd <sboyd@...eaurora.org>
Cc:	linux-arm-kernel@...ts.infradead.org,
	Nicolas Pitre <nicolas.pitre@...aro.org>,
	Omar Ramirez Luna <omar.ramirez@...com>,
	Phil Carmody <ext-phil.2.carmody@...ia.com>,
	Russell King <linux@....linux.org.uk>,
	Dave Martin <dave.martin@...aro.org>,
	Tony Lindgren <tony@...mide.com>,
	Catalin Marinas <catalin.marinas@....com>,
	linux-kernel@...r.kernel.org, Rabin Vincent <rabin@....in>,
	Alexander Shishkin <virtuoso@...nd.org>,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Joe Perches <joe@...ches.com>
Subject: Re: [PATCH v5] ARM: Use generic BUG() handler

OK, yes will do, thanks.

-Simon

On Tue, Aug 9, 2011 at 3:15 PM, Stephen Boyd <sboyd@...eaurora.org> wrote:
> On 07/29/2011 12:56 AM, Simon Glass wrote:
>> From: Simon Glass <sjg@...gle.com>
>>
>> ARM uses its own BUG() handler which makes its output slightly different
>> from other archtectures.
>>
>> One of the problems is that the ARM implementation doesn't report the function
>> with the BUG() in it, but always reports the PC being in __bug(). The generic
>> implementation doesn't have this problem.
>>
>> Currently we get something like:
>>
>> kernel BUG at fs/proc/breakme.c:35!
>> Unable to handle kernel NULL pointer dereference at virtual address 00000000
>> ...
>> PC is at __bug+0x20/0x2c
>>
>> With this patch it displays:
>>
>> kernel BUG at fs/proc/breakme.c:35!
>> Internal error: Oops - undefined instruction: 0 [#1] PREEMPT SMP
>> ...
>> PC is at write_breakme+0xd0/0x1b4
>>
>> This implementation uses an undefined instruction to implement BUG, and sets up
>> a bug table containing the relevant information. Many versions of gcc do not
>> support %c properly for ARM (inserting a # when they shouldn't) so we work
>> around this using distasteful macro magic.
>>
>> v1: Initial version to replace existing ARM BUG() implementation with something
>> more similar to other architectures.
>>
>> v2: Add Thumb support, remove backtrace whitespace output changes. Change to
>> use macros instead of requiring the asm %d flag to work (thanks to
>> Dave Martin <dave.martin@...aro.org>)
>>
>> v3: Remove old BUG() implementation in favor of this one.
>> Remove the Backtrace: message (will submit this separately).
>> Use ARM_EXIT_KEEP() so that some architectures can dump exit text at link time
>> thanks to Stephen Boyd <sboyd@...eaurora.org> (although since we always
>> define GENERIC_BUG this might be academic.)
>> Rebase to linux-2.6.git master.
>>
>> v4: Allow BUGS in modules (these were not reported correctly in v3)
>> (thanks to Stephen Boyd <sboyd@...eaurora.org> for suggesting that.)
>> Remove __bug() as this is no longer needed.
>>
>> v5: Add %progbits as the section flags.
>
> Tested-by: Stephen Boyd <sboyd@...eaurora.org>
>
>> Signed-off-by: Simon Glass <sjg@...omium.org>
>> ---
>>
>
> Can you update the patch in the patch tracker? It would be great to see
> this in the next merge window.
>
> --
> Sent by an employee of the Qualcomm Innovation Center, Inc.
> The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum.
>
>
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