sparc64: Fix recursion in stack overflow detection handling.

[ 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@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/arch/sparc64/lib/mcount.S b/arch/sparc64/lib/mcount.S
index 9e4534b485c7a578af04517adff245a413f7bfb9..89556aaad7c1551d912500eed6046421b64802fe 100644 (file)
--- 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