[POWERPC] Move to runtime allocated exception stacks

For the additonal exception levels (critical, debug, machine check) on
40x/book-e we were using "static" allocations of the stack in the
associated head.S.

Move to a runtime allocation to make the code a bit easier to read as
we mimic how we handle IRQ stacks.  Its also a bit easier to setup the
stack with a "dummy" thread_info in C code.

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

1 files changed, 11 insertions, 18 deletions

diff --git a/arch/powerpc/kernel/head_booke.h b/arch/powerpc/kernel/head_booke.h
index 721faef87095..9eacf4ca442a 100644
--- a/arch/powerpc/kernel/head_booke.h
+++ b/arch/powerpc/kernel/head_booke.h
@@ -43,9 +43,7 @@
         SAVE_2GPRS(7, r11)
 
 /* To handle the additional exception priority levels on 40x and Book-E
- * processors we allocate a 4k stack per additional priority level. The various
- * head_xxx.S files allocate space (exception_stack_top) for each priority's
- * stack times the number of CPUs
+ * processors we allocate a stack per additional priority level.
  *
  * On 40x critical is the only additional level
  * On 44x/e500 we have critical and machine check
@@ -61,36 +59,31 @@
  * going to critical or their own debug level we aren't currently
  * providing configurations that micro-optimize space usage.
  */
-#ifdef CONFIG_44x
-#define NUM_EXCEPTION_LVLS      2
-#else
-#define NUM_EXCEPTION_LVLS      3
-#endif
-#define BOOKE_EXCEPTION_STACK_SIZE      (4096 * NUM_EXCEPTION_LVLS)
 
 /* CRIT_SPRG only used in critical exception handling */
 #define CRIT_SPRG       SPRN_SPRG2
 /* MCHECK_SPRG only used in machine check exception handling */
 #define MCHECK_SPRG     SPRN_SPRG6W
 
-#define MCHECK_STACK_TOP        (exception_stack_top - 4096)
-#define CRIT_STACK_TOP          (exception_stack_top)
+#define MCHECK_STACK_BASE       mcheckirq_ctx
+#define CRIT_STACK_BASE         critirq_ctx
 
 /* only on e200 for now */
-#define DEBUG_STACK_TOP         (exception_stack_top - 8192)
+#define DEBUG_STACK_BASE        dbgirq_ctx
 #define DEBUG_SPRG              SPRN_SPRG6W
 
 #ifdef CONFIG_SMP
 #define BOOKE_LOAD_EXC_LEVEL_STACK(level)               \
         mfspr   r8,SPRN_PIR;                            \
-        mulli   r8,r8,BOOKE_EXCEPTION_STACK_SIZE;       \
-        neg     r8,r8;                                  \
-        addis   r8,r8,level##_STACK_TOP@ha;             \
-        addi    r8,r8,level##_STACK_TOP@l
+        slwi    r8,r8,2;                                \
+        addis   r8,r8,level##_STACK_BASE@ha;            \
+        lwz     r8,level##_STACK_BASE@l(r8);            \
+        addi    r8,r8,THREAD_SIZE;
 #else
 #define BOOKE_LOAD_EXC_LEVEL_STACK(level)               \
-        lis     r8,level##_STACK_TOP@h;                 \
-        ori     r8,r8,level##_STACK_TOP@l
+        lis     r8,level##_STACK_BASE@ha;               \
+        lwz     r8,level##_STACK_BASE@l(r8);            \
+        addi    r8,r8,THREAD_SIZE;
 #endif
 
 /*