[PATCH] ARM: BUG() dies silently

[sjg@chromium.org (Simon Glass)]

You might try the generic bug patch and see if it also fixes this
problem - Simon

On Thu, Mar 31, 2011 at 1:15 PM, Omar Ramirez Luna <omar.ramirez@ti.com> wrote:
> There are some cases where the code generated for BUG() results
> into an infinite while loop without causing a null dereference,
> this ends on a kernel being stuck on a loop and the user without
> a clue of what happened.
>
> E.g.: lib/scatterlist.c : __sg_alloc_table
>
> ? ? ? ?BUG_ON(nents > max_ents);
> ?438: ? 9a000000 ? ? ? ?bls ? ? 440 <__sg_alloc_table+0x20>
> ?43c: ? eafffffe ? ? ? ?b ? ? ? 43c <__sg_alloc_table+0x1c>
>
> Adding volatile makes the compiler to avoid optimizations on this
> code, which makes the panic to occur:
>
> ? ? ? ?BUG_ON(nents > max_ents);
> ?438: ? 9a000002 ? ? ? ?bls ? ? 448 <__sg_alloc_table+0x28>
> ?43c: ? e3a03000 ? ? ? ?mov ? ? r3, #0
> ?440: ? e5833000 ? ? ? ?str ? ? r3, [r3]
> ?444: ? eafffffc ? ? ? ?b ? ? ? 43c <__sg_alloc_table+0x1c>
>
> Seen with gnu/linux cs arm-2010q1-202 and arm2010.09-50.
>
> Signed-off-by: Omar Ramirez Luna <omar.ramirez@ti.com>
> ---
>
> If needed I can change:
> ./arch/arm/mach-clps711x/include/mach/io.h:
> ? ? ? ?#define __raw_readsb(p,d,l) ?do { *(int *)0 = 0; } while (0)
> ./arch/arm/mach-clps711x/include/mach/io.h:
> ? ? ? ?#define __raw_readsl(p,d,l) ?do { *(int *)0 = 0; } while (0)
> ./arch/arm/mach-clps711x/include/mach/io.h:
> ? ? ? ?#define __raw_writesb(p,d,l) do { *(int *)0 = 0; } while (0)
> ./arch/arm/mach-clps711x/include/mach/io.h:
> ? ? ? ?#define __raw_writesl(p,d,l) do { *(int *)0 = 0; } while (0)
> ./arch/arm/kernel/traps.c: ? ? ?*(int *)0 = 0;
>
>
> ?arch/arm/include/asm/bug.h | ? ?2 +-
> ?1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/arch/arm/include/asm/bug.h b/arch/arm/include/asm/bug.h
> index 4d88425..a58d863 100644
> --- a/arch/arm/include/asm/bug.h
> +++ b/arch/arm/include/asm/bug.h
> @@ -12,7 +12,7 @@ extern void __bug(const char *file, int line) __attribute__((noreturn));
> ?#else
>
> ?/* this just causes an oops */
> -#define BUG() ? ? ? ? ?do { *(int *)0 = 0; } while (1)
> +#define BUG() ? ? ? ? ?do { *(volatile int *)0 = 0; } while(1)
>
> ?#endif
>
> --
> 1.7.1
>
> --
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