[POWERPC] 40x/Book-E: Save/restore volatile exception registers

On machines with more than one exception level any system register that
might be modified by the "normal" exception level needs to be saved and
restored on taking a higher level exception.  We already are saving
and restoring ESR and DEAR.

For critical level add SRR0/1.
For debug level add CSRR0/1 and SRR0/1.
For machine check level add DSRR0/1, CSRR0/1, and SRR0/1.

On FSL Book-E parts we always save/restore the MAS registers for critical,
debug, and machine check level exceptions.  On 44x we always save/restore
the MMUCR.

Additionally, we save and restore the ksp_limit since we have to adjust it
for each exception level.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
Acked-by: Paul Mackerras <paulus@samba.org>

1 files changed, 22 insertions, 1 deletions

diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index b0874d228ea..f277fade193 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -72,7 +72,7 @@
 #define DEBUG_STACK_BASE        dbgirq_ctx
 #define DEBUG_SPRG              SPRN_SPRG6W
 
-#define EXC_LVL_FRAME_OVERHEAD  (THREAD_SIZE - INT_FRAME_SIZE)
+#define EXC_LVL_FRAME_OVERHEAD  (THREAD_SIZE - INT_FRAME_SIZE - EXC_LVL_SIZE)
 
 #ifdef CONFIG_SMP
 #define BOOKE_LOAD_EXC_LEVEL_STACK(level)               \
@@ -376,4 +376,25 @@ label:
         addi    r3,r1,STACK_FRAME_OVERHEAD;                                   \
         EXC_XFER_EE_LITE(0x800, kernel_fp_unavailable_exception)
 
+#ifndef __ASSEMBLY__
+struct exception_regs {
+        unsigned long mas0;
+        unsigned long mas1;
+        unsigned long mas2;
+        unsigned long mas3;
+        unsigned long mas6;
+        unsigned long mas7;
+        unsigned long srr0;
+        unsigned long srr1;
+        unsigned long csrr0;
+        unsigned long csrr1;
+        unsigned long dsrr0;
+        unsigned long dsrr1;
+        unsigned long saved_ksp_limit;
+};
+
+/* ensure this structure is always sized to a multiple of the stack alignment */
+#define STACK_EXC_LVL_FRAME_SIZE        _ALIGN_UP(sizeof (struct exception_regs), 16)
+
+#endif /* __ASSEMBLY__ */
 #endif /* __HEAD_BOOKE_H__ */