[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, 25 insertions, 0 deletions

diff --git a/arch/powerpc/kernel/misc_32.S b/arch/powerpc/kernel/misc_32.S
index 92ccc6fcc5b0..89aaaa6f3561 100644
--- a/arch/powerpc/kernel/misc_32.S
+++ b/arch/powerpc/kernel/misc_32.S
@@ -32,6 +32,31 @@
 
         .text
 
+#ifdef CONFIG_IRQSTACKS
+_GLOBAL(call_do_softirq)
+        mflr    r0
+        stw     r0,4(r1)
+        stwu    r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r3)
+        mr      r1,r3
+        bl      __do_softirq
+        lwz     r1,0(r1)
+        lwz     r0,4(r1)
+        mtlr    r0
+        blr
+
+_GLOBAL(call_handle_irq)
+        mflr    r0
+        stw     r0,4(r1)
+        mtctr   r6
+        stwu    r1,THREAD_SIZE-STACK_FRAME_OVERHEAD(r5)
+        mr      r1,r5
+        bctrl
+        lwz     r1,0(r1)
+        lwz     r0,4(r1)
+        mtlr    r0
+        blr
+#endif /* CONFIG_IRQSTACKS */
+
 /*
  * This returns the high 64 bits of the product of two 64-bit numbers.
  */