[PATCH] x86: push old stack address on irqstack for unwinder

[Martin Hicks <mort@sgi.com>]

Hi,

KDB was using this information.  Could this be pushed towards 2.6.29 please?

This re-adds the old stack pointer to the top of the irqstack to help
with unwinding.  It was removed in commit d99015b1abbad743aa049b439c1e1dede6d0fa49
as part of the save_args out-of-line work.

Signed-off-by: Martin Hicks <mort@sgi.com>
---
 arch/x86/kernel/entry_64.S |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/arch/x86/kernel/entry_64.S b/arch/x86/kernel/entry_64.S
index e28c7a9..a134621 100644
--- a/arch/x86/kernel/entry_64.S
+++ b/arch/x86/kernel/entry_64.S
@@ -346,6 +346,7 @@ ENTRY(save_args)
 	popq_cfi %rax			/* move return address... */
 	mov %gs:pda_irqstackptr,%rsp
 	EMPTY_FRAME 0
+	pushq_cfi %rbp			/* backlink for unwinder */
 	pushq_cfi %rax			/* ... to the new stack */
 	/*
 	 * We entered an interrupt context - irqs are off: