[POWERPC] Add IRQSTACKS support on ppc32

This makes it possible to use separate stacks for hard and soft IRQs
on 32-bit powerpc as well as on 64-bit.  The code for 32-bit is just
the 32-bit analog of the 64-bit code.

* Added allocation and initialization of the irq stacks.  We limit the
  stacks to be in lowmem for ppc32.
* Implemented ppc32 versions of call_do_softirq() and call_handle_irq()
  to switch the stack pointers
* Reworked how we do stack overflow detection.  We now keep around the
  limit of the stack in the thread_struct and compare against the limit
  to see if we've overflowed.  We can now use this on ppc64 if desired.

[ paulus@samba.org: Fixed bug on 6xx where we need to reload r9 with the
  thread_info pointer. ]

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

1 files changed, 6 insertions, 0 deletions

diff --git a/include/asm-powerpc/processor.h b/include/asm-powerpc/processor.h
index fd98ca998b4f..cf83f2d7e2a5 100644
--- a/include/asm-powerpc/processor.h
+++ b/include/asm-powerpc/processor.h
@@ -138,6 +138,8 @@ typedef struct {
 
 struct thread_struct {
         unsigned long   ksp;            /* Kernel stack pointer */
+        unsigned long   ksp_limit;      /* if ksp <= ksp_limit stack overflow */
+
 #ifdef CONFIG_PPC64
         unsigned long   ksp_vsid;
 #endif
@@ -182,11 +184,14 @@ struct thread_struct {
 #define ARCH_MIN_TASKALIGN 16
 
 #define INIT_SP         (sizeof(init_stack) + (unsigned long) &init_stack)
+#define INIT_SP_LIMIT \
+        (_ALIGN_UP(sizeof(init_thread_info), 16) + (unsigned long) &init_stack)
 
 
 #ifdef CONFIG_PPC32
 #define INIT_THREAD { \
         .ksp = INIT_SP, \
+        .ksp_limit = INIT_SP_LIMIT, \
         .fs = KERNEL_DS, \
         .pgdir = swapper_pg_dir, \
         .fpexc_mode = MSR_FE0 | MSR_FE1, \
@@ -194,6 +199,7 @@ struct thread_struct {
 #else
 #define INIT_THREAD  { \
         .ksp = INIT_SP, \
+        .ksp_limit = INIT_SP_LIMIT, \
         .regs = (struct pt_regs *)INIT_SP - 1, /* XXX bogus, I think */ \
         .fs = KERNEL_DS, \
         .fpr = {0}, \