[POWERPC] Save trap number in bad_stack

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 number is reported.

Signed-off-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Paul Mackerras <paulus@samba.org>

3 files changed, 10 insertions, 2 deletions

diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
index 9735e828b52d..0c5150c69175 100644
--- a/arch/powerpc/kernel/asm-offsets.c
+++ b/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));
diff --git a/arch/powerpc/kernel/head_64.S b/arch/powerpc/kernel/head_64.S
index aff5398a5f63..1111fcec7673 100644
--- a/arch/powerpc/kernel/head_64.S
+++ b/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       */ \
+        sth     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)
+        lhz     r12,PACA_TRAP_SAVE(r13)
+        std     r12,_TRAP(r1)
         addi    r11,r1,INT_FRAME_SIZE
         std     r11,0(r1)
         li      r12,0
diff --git a/include/asm-powerpc/paca.h b/include/asm-powerpc/paca.h
index 4de851d91f96..cf95274f735e 100644
--- a/include/asm-powerpc/paca.h
+++ b/include/asm-powerpc/paca.h
@@ -94,6 +94,7 @@ struct paca_struct {
         u64 stab_rr;                    /* stab/slb round-robin counter */
         u64 saved_r1;                   /* r1 save for RTAS calls */
         u64 saved_msr;                  /* MSR saved here by enter_rtas */
+        u16 trap_save;                  /* Used when bad stack is encountered */
         u8 soft_enabled;                /* irq soft-enable flag */
         u8 hard_enabled;                /* set if irqs are enabled in MSR */
         u8 io_sync;                     /* writel() needs spin_unlock sync */