Re: [PATCH v4] ARM: Use generic BUG() handler

From: Stephen Boyd
Date: Thu Apr 14 2011 - 22:10:40 EST

On 04/14/2011 04:00 PM, Simon Glass wrote:
> From: Simon Glass <sjg@xxxxxxxxxx>
> 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@xxxxxxxxxx>)
> 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@xxxxxxxxxxxxxx> (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@xxxxxxxxxxxxxx> for suggesting that.)
> Remove __bug() as this is no longer needed.
> Signed-off-by: Simon Glass <sjg@xxxxxxxxxxxx>

Reviewed-by: Stephen Boyd <sboyd@xxxxxxxxxxxxxx>

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