[patch 48/60] sparc64: Fix recursion in stack overflow detectionhandling.

[Greg KH]

2.6.26-stable review patch.  If anyone has any objections, please let us know.

------------------
[ Upstream commit c7498081a6f5d96c9f3243b6b5e020352903bfd2 ]

The calls down into prom_printf() when we detect an overflowed stack
can recurse again since the overflow stack will be "below" the current
kernel stack limit.

Prevent this by just returning straight if we are on the stack
overflow safe stack already.

Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxx>

---
 arch/sparc64/lib/mcount.S |   17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

--- a/arch/sparc64/lib/mcount.S
+++ b/arch/sparc64/lib/mcount.S
@@ -45,12 +45,23 @@ _mcount:
 	sub		%g3, STACK_BIAS, %g3
 	cmp		%sp, %g3
 	bg,pt		%xcc, 1f
-	 sethi		%hi(panicstring), %g3
+	 nop
+	/* If we are already on ovstack, don't hop onto it
+	 * again, we are already trying to output the stack overflow
+	 * message.
+	 */
 	sethi		%hi(ovstack), %g7		! cant move to panic stack fast enough
 	 or		%g7, %lo(ovstack), %g7
-	add		%g7, OVSTACKSIZE, %g7
+	add		%g7, OVSTACKSIZE, %g3
+	sub		%g3, STACK_BIAS + 192, %g3
 	sub		%g7, STACK_BIAS, %g7
-	mov		%g7, %sp
+	cmp		%sp, %g7
+	blu,pn		%xcc, 2f
+	 cmp		%sp, %g3
+	bleu,pn		%xcc, 1f
+	 nop
+2:	mov		%g3, %sp
+	sethi		%hi(panicstring), %g3
 	call		prom_printf
 	 or		%g3, %lo(panicstring), %o0
 	call		prom_halt

-- 
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