s390: fix machine check panic stack switch

For system damage machine checks or machine checks due to invalid PSW
fields the system will be stopped. In order to get an oops message out
before killing the system the machine check handler branches to
.Lmcck_panic, switches to the panic stack and then does the usual
machine check handling.

The switch to the panic stack is incomplete, the stack pointer in %r15
is replaced, but the pt_regs pointer in %r11 is not. The result is
a program check which will kill the system in a slightly different way.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index 161f4e66f67d758b9d083cc0125817641ee4f666..1a450d220f566592b48688ea4ed6aaf15744a47b 100644 (file)
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -958,7 +958,7 @@ ENTRY(mcck_int_handler)
 
 .Lmcck_panic:
        lg      %r15,__LC_PANIC_STACK
-       aghi    %r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)
+       la      %r11,STACK_FRAME_OVERHEAD(%r15)
        j       .Lmcck_skip
 
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