Subject: Re: [PATCH] [v2] powerpc: save trap number in bad_stack

From: Gabriel Paubert <[email-masked]>
Date: Mon, 23 Apr 2007 11:29:19 +0200

On Sun, Apr 22, 2007 at 06:38:21PM -0500, Olof Johansson wrote:
> Save the trap number in the case of getting a bad stack in an exception
> handler. It is sometimes useful to know what exception it was that caused
> this to happen. Without this, no trap is reported.
> 
> Signed-off-by: Olof Johansson <[email-masked]>
> 
> ---
> 
> Changes since last time: Reduce to a u16 and move it.
> 
> Index: powerpc/arch/powerpc/kernel/asm-offsets.c
> ===================================================================
> --- powerpc.orig/arch/powerpc/kernel/asm-offsets.c
> +++ powerpc/arch/powerpc/kernel/asm-offsets.c
> @@ -139,6 +139,7 @@ int main(void)
>  	DEFINE(PACA_SYSTEM_TIME, offsetof(struct paca_struct, system_time));
>  	DEFINE(PACA_SLBSHADOWPTR, offsetof(struct paca_struct, slb_shadow_ptr));
>  	DEFINE(PACA_DATA_OFFSET, offsetof(struct paca_struct, data_offset));
> +	DEFINE(PACA_TRAP_SAVE, offsetof(struct paca_struct, trap_save));
>  
>  	DEFINE(SLBSHADOW_STACKVSID,
>  	       offsetof(struct slb_shadow, save_area[SLB_NUM_BOLTED - 1].vsid));
> Index: powerpc/include/asm-powerpc/paca.h
> ===================================================================
> --- powerpc.orig/include/asm-powerpc/paca.h
> +++ powerpc/include/asm-powerpc/paca.h
> @@ -68,6 +68,7 @@ struct paca_struct {
>  	void *emergency_sp;		/* pointer to emergency stack */
>  	u64 data_offset;		/* per cpu data offset */
>  	s16 hw_cpu_id;			/* Physical processor number */
> +	u16 trap_save;			/* Used when bad stack is encountered */
>  	u8 cpu_start;			/* At startup, processor spins until */
>  					/* this becomes non-zero. */
>  	struct slb_shadow *slb_shadow_ptr;
> Index: powerpc/arch/powerpc/kernel/head_64.S
> ===================================================================
> --- powerpc.orig/arch/powerpc/kernel/head_64.S
> +++ powerpc/arch/powerpc/kernel/head_64.S
> @@ -278,8 +278,12 @@ exception_marker:
>  	beq-	1f;							   \
>  	ld	r1,PACAKSAVE(r13);	/* kernel stack to use		*/ \
>  1:	cmpdi	cr1,r1,0;		/* check if r1 is in userspace	*/ \
> -	bge-	cr1,bad_stack;		/* abort if it is		*/ \
> -	std	r9,_CCR(r1);		/* save CR in stackframe	*/ \
> +	bge-	cr1,2f;			/* abort if it is		*/ \
> +	b	3f;							   \
> +2:	li	r1,(n);			/* will be reloaded later	*/ \
> +	stw	r1,PACA_TRAP_SAVE(r13);					   \

stW to an u16? stH seems safer!

> +	b	bad_stack;						   \
> +3:	std	r9,_CCR(r1);		/* save CR in stackframe	*/ \
>  	std	r11,_NIP(r1);		/* save SRR0 in stackframe	*/ \
>  	std	r12,_MSR(r1);		/* save SRR1 in stackframe	*/ \
>  	std	r10,0(r1);		/* make stack chain pointer	*/ \
> @@ -940,6 +944,8 @@ bad_stack:
>  	SAVE_2GPRS(7,r1)
>  	SAVE_10GPRS(12,r1)
>  	SAVE_10GPRS(22,r1)
> +	lwz	r12,PACA_TRAP_SAVE(r13)

Same, well actually lwz->lhz.

> +	std	r12,_TRAP(r1)
>  	addi	r11,r1,INT_FRAME_SIZE
>  	std	r11,0(r1)
>  	li	r12,0

	Gabriel