xtensa: fix get_wchan

Stack unwinding is implemented incorrectly in xtensa get_wchan: instead
of extracting a0 and a1 registers from the spill location under the
stack pointer it extracts a word pointed to by the stack pointer and
subtracts 4 or 3 from it.

Cc: stable@vger.kernel.org
Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>

diff --git a/arch/xtensa/kernel/process.c b/arch/xtensa/kernel/process.c
index 74969a4..2e73395 100644 (file)
--- a/arch/xtensa/kernel/process.c
+++ b/arch/xtensa/kernel/process.c
@@ -321,8 +321,8 @@ unsigned long get_wchan(struct task_struct *p)
 
                /* Stack layout: sp-4: ra, sp-3: sp' */
 
-               pc = MAKE_PC_FROM_RA(*(unsigned long*)sp - 4, sp);
-               sp = *(unsigned long *)sp - 3;
+               pc = MAKE_PC_FROM_RA(SPILL_SLOT(sp, 0), sp);
+               sp = SPILL_SLOT(sp, 1);
        } while (count++ < 16);
        return 0;
 }