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 7735a7a60533fa225256ad0bd2d94a00be26033a..734caf0cec09a02e77d7cd432ab74631e106cef9 100644 (file)
--- 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