[S390] s390: fix single stepping on svc0

On s390 there are two ways of specifying the system call number for
the svc instruction. The standard way is to use the immediate field
in the instruction (or to use EXecute for values unknown during
assemble time). This can encode 256 system calls.
The kernel ABI also allows to put the system call number in r1 and
then execute svc 0 to enable system call numbers > 255.

It turns out that single stepping svc 0 is broken, since the PER
program check handler uses r1. We have to use a different register.

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

1 files changed, 4 insertions, 4 deletions

diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S
index f43d2ee54464..48215d15762b 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -565,10 +565,10 @@ pgm_svcper:
         lh      %r7,0x8a                # get svc number from lowcore
         l       %r9,__LC_THREAD_INFO    # load pointer to thread_info struct
         TRACE_IRQS_OFF
-        l       %r1,__TI_task(%r9)
-        mvc     __THREAD_per+__PER_atmid(2,%r1),__LC_PER_ATMID
-        mvc     __THREAD_per+__PER_address(4,%r1),__LC_PER_ADDRESS
-        mvc     __THREAD_per+__PER_access_id(1,%r1),__LC_PER_ACCESS_ID
+        l       %r8,__TI_task(%r9)
+        mvc     __THREAD_per+__PER_atmid(2,%r8),__LC_PER_ATMID
+        mvc     __THREAD_per+__PER_address(4,%r8),__LC_PER_ADDRESS
+        mvc     __THREAD_per+__PER_access_id(1,%r8),__LC_PER_ACCESS_ID
         oi      __TI_flags+3(%r9),_TIF_SINGLE_STEP # set TIF_SINGLE_STEP
         TRACE_IRQS_ON
         stosm   __SF_EMPTY(%r15),0x03   # reenable interrupts