From: David S. Miller <davem@davemloft.net>
Date: Tue, 12 Aug 2008 09:03:49 +0000 (-0700)
Subject: sparc64: Fix recursion in stack overflow detection handling.
X-Git-Tag: v2.6.27-rc4~104^2~3
X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c7498081a6f5d96c9f3243b6b5e020352903bfd2;p=linux-2.6

sparc64: Fix recursion in stack overflow detection handling.

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@davemloft.net>
---

diff --git a/arch/sparc64/lib/mcount.S b/arch/sparc64/lib/mcount.S
index 7735a7a605..734caf0cec 100644
--- a/arch/sparc64/lib/mcount.S
+++ b/arch/sparc64/lib/mcount.S
@@ -48,12 +48,23 @@ 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