[S390] add missing .set function for NT_S390_LAST_BREAK regset

The last breaking event address is a read-only value, the regset misses the
.set function. If a PTRACE_SETREGSET is done for NT_S390_LAST_BREAK we
get an oops due to a branch to zero:

Kernel BUG at 0000000000000002 verbose debug info unavailable
illegal operation: 0001 #1 SMP
...
Call Trace:
(<0000000000158294> ptrace_regset+0x184/0x188)
 <00000000001595b6> ptrace_request+0x37a/0x4fc
 <0000000000109a78> arch_ptrace+0x108/0x1fc
 <00000000001590d6> SyS_ptrace+0xaa/0x12c
 <00000000005c7a42> sysc_noemu+0x16/0x1c
 <000003fffd5ec10c> 0x3fffd5ec10c
Last Breaking-Event-Address:
 <0000000000158242> ptrace_regset+0x132/0x188

Add a nop .set function to prevent the branch to zero.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: stable@kernel.org

1 files changed, 18 insertions, 0 deletions

diff --git a/arch/s390/kernel/ptrace.c b/arch/s390/kernel/ptrace.c
index 450931a45b68..f05649fd0547 100644
--- a/arch/s390/kernel/ptrace.c
+++ b/arch/s390/kernel/ptrace.c
@@ -905,6 +905,14 @@ static int s390_last_break_get(struct task_struct *target,
         return 0;
 }
 
+static int s390_last_break_set(struct task_struct *target,
+                               const struct user_regset *regset,
+                               unsigned int pos, unsigned int count,
+                               const void *kbuf, const void __user *ubuf)
+{
+        return 0;
+}
+
 #endif
 
 static int s390_system_call_get(struct task_struct *target,
@@ -951,6 +959,7 @@ static const struct user_regset s390_regsets[] = {
                 .size = sizeof(long),
                 .align = sizeof(long),
                 .get = s390_last_break_get,
+                .set = s390_last_break_set,
         },
 #endif
         [REGSET_SYSTEM_CALL] = {
@@ -1116,6 +1125,14 @@ static int s390_compat_last_break_get(struct task_struct *target,
         return 0;
 }
 
+static int s390_compat_last_break_set(struct task_struct *target,
+                                      const struct user_regset *regset,
+                                      unsigned int pos, unsigned int count,
+                                      const void *kbuf, const void __user *ubuf)
+{
+        return 0;
+}
+
 static const struct user_regset s390_compat_regsets[] = {
         [REGSET_GENERAL] = {
                 .core_note_type = NT_PRSTATUS,
@@ -1139,6 +1156,7 @@ static const struct user_regset s390_compat_regsets[] = {
                 .size = sizeof(long),
                 .align = sizeof(long),
                 .get = s390_compat_last_break_get,
+                .set = s390_compat_last_break_set,
         },
         [REGSET_SYSTEM_CALL] = {
                 .core_note_type = NT_S390_SYSTEM_CALL,