[PATCH] powerpc: save trap number in bad_stack

[olof@lixom.net (Olof Johansson)]

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 <olof@lixom.net>

Index: linux-2.6/arch/powerpc/kernel/asm-offsets.c
===================================================================
--- linux-2.6.orig/arch/powerpc/kernel/asm-offsets.c
+++ linux-2.6/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: linux-2.6/include/asm-powerpc/paca.h
===================================================================
--- linux-2.6.orig/include/asm-powerpc/paca.h
+++ linux-2.6/include/asm-powerpc/paca.h
@@ -81,6 +81,8 @@ struct paca_struct {
 	u64 exslb[10];		/* used for SLB/segment table misses
  				 * on the linear mapping */
 
+	u64 trap_save;			/* Used when bad stack is encountered */
+
 	mm_context_t context;
 	u16 vmalloc_sllp;
 	u16 slb_cache[SLB_CACHE_ENTRIES];
Index: linux-2.6/arch/powerpc/kernel/head_64.S
===================================================================
--- linux-2.6.orig/arch/powerpc/kernel/head_64.S
+++ linux-2.6/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	*/ \
+	std	r1,PACA_TRAP_SAVE(r13);					   \
+	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)
+	ld	r12,PACA_TRAP_SAVE(r13)
+	std	r12,_TRAP(r1)
 	addi	r11,r1,INT_FRAME_SIZE
 	std	r11,0(r1)
 	li	r12,0