Re: [PATCH] MIPS: microMIPS: Redefine value of BRK_BUG.

[David Daney <ddaney.cavm@gmail.com>]

On 01/17/2013 09:36 AM, Steven J. Hill wrote:
> From: "Steven J. Hill" <sjhill@mips.com>
>
> The BRK_BUG value is used in the BUG and __BUG_ON inline macros. For
> standard MIPS cores the code in the 'tne' instruction is 10-bits long.
> In microMIPS, the 'tne' instruction is recoded and the code can only be
> 4-bits long. We use the value of 12 instead of 512 when building a
> microMIPS kernel.
>
> Signed-off-by: Steven J. Hill <sjhill@mips.com>
> ---
>   arch/mips/include/asm/break.h |    1 +
>   arch/mips/include/asm/bug.h   |    4 ++++
>   2 files changed, 5 insertions(+)
>
> diff --git a/arch/mips/include/asm/break.h b/arch/mips/include/asm/break.h
> index 9161e68..df9d090 100644
> --- a/arch/mips/include/asm/break.h
> +++ b/arch/mips/include/asm/break.h
> @@ -27,6 +27,7 @@
>   #define BRK_STACKOVERFLOW 9	/* For Ada stackchecking */
>   #define BRK_NORLD	10	/* No rld found - not used by Linux/MIPS */
>   #define _BRK_THREADBP	11	/* For threads, user bp (used by debuggers) */
> +#define BRK_BUG_MM	12	/* Used by BUG() in microMIPS mode */
>   #define BRK_BUG		512	/* Used by BUG() */

Can we move the CONFIG_CPU_MICROMIPS to here and just call the thing 
BRK_BUG?

Or perhaps redefining it unconditionally.  I am not sure what the 
implications of doing that would be.

That way...


>   #define BRK_KDB		513	/* Used in KDB_ENTER() */
>   #define BRK_MEMU	514	/* Used by FPU emulator */
> diff --git a/arch/mips/include/asm/bug.h b/arch/mips/include/asm/bug.h
> index 540c98a..b716fb9 100644
> --- a/arch/mips/include/asm/bug.h
> +++ b/arch/mips/include/asm/bug.h
> @@ -7,6 +7,10 @@
>   #ifdef CONFIG_BUG
>
>   #include <asm/break.h>
> +#ifdef CONFIG_CPU_MICROMIPS
> +#undef BRK_BUG
> +#define BRK_BUG		BRK_BUG_MM
> +#endif
>

...We don't need this bit.   Doing an #undef risks using different 
values for BRK_BUG depending on whether or not asm/bug.h is included.

>   static inline void __noreturn BUG(void)
>   {
>