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>

1 files changed, 14 insertions, 3 deletions

diff --git a/arch/sparc64/lib/mcount.S b/arch/sparc64/lib/mcount.S
index 7735a7a60533..734caf0cec09 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