[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, 4 insertions, 14 deletions

diff --git a/arch/powerpc/kernel/head_40x.S b/arch/powerpc/kernel/head_40x.S
index 8552e67e3a8b..f2cf60d38f78 100644
--- a/arch/powerpc/kernel/head_40x.S
+++ b/arch/powerpc/kernel/head_40x.S
@@ -148,14 +148,14 @@ _ENTRY(crit_r11)
         mfcr    r10;                    /* save CR in r10 for now          */\
         mfspr   r11,SPRN_SRR3;          /* check whether user or kernel    */\
         andi.   r11,r11,MSR_PR;                                              \
-        lis     r11,critical_stack_top@h;                                    \
-        ori     r11,r11,critical_stack_top@l;                                \
+        lis     r11,critirq_ctx@ha;                                          \
+        tophys(r11,r11);                                                     \
+        lwz     r11,critirq_ctx@l(r11);                                      \
         beq     1f;                                                          \
         /* COMING FROM USER MODE */                                          \
         mfspr   r11,SPRN_SPRG3;         /* if from user, start at top of   */\
         lwz     r11,THREAD_INFO-THREAD(r11); /* this thread's kernel stack */\
-        addi    r11,r11,THREAD_SIZE;                                         \
-1:      subi    r11,r11,INT_FRAME_SIZE; /* Allocate an exception frame     */\
+1:      addi    r11,r11,THREAD_SIZE-INT_FRAME_SIZE; /* Alloc an excpt frm  */\
         tophys(r11,r11);                                                     \
         stw     r10,_CCR(r11);          /* save various registers          */\
         stw     r12,GPR12(r11);                                              \
@@ -996,16 +996,6 @@ empty_zero_page:
 swapper_pg_dir:
         .space  PGD_TABLE_SIZE
 
-
-/* Stack for handling critical exceptions from kernel mode */
-        .section .bss
-        .align 12
-exception_stack_bottom:
-        .space  4096
-critical_stack_top:
-        .globl  exception_stack_top
-exception_stack_top:
-
 /* Room for two PTE pointers, usually the kernel and current user pointers
  * to their respective root page table.
  */