s390/kprobes: remove KPROBE_SWAP_INST state

For an unknown reason the s390 kprobes instruction replacement
function modifies the kprobe_status of the current CPU to
KPROBE_SWAP_INST. This was supposed to catch traps that happened
during instruction patching. Such a fault is not supposed to happen,
and silently discarding such a fault is certainly also not what we
want. In fact s390 is the only architecture which has this odd piece
of code.

Just remove this and behave like all other architectures. This was
pointed out by Jens Remus.
Reported-by: NJens Remus <jremus@linux.vnet.ibm.com>
Signed-off-by: NHeiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: NMartin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/include/asm/kprobes.h

@@ -63,8 +63,6 @@ typedef u16 kprobe_opcode_t;
 
 #define kretprobe_blacklist_size 0
 
-#define KPROBE_SWAP_INST	0x10
-
 /* Architecture specific copy of original instruction */
 struct arch_specific_insn {
 	/* copy of original instruction */

arch/s390/kernel/kprobes.c

@@ -161,8 +161,6 @@ struct swap_insn_args {
 
 static int swap_instruction(void *data)
 {
-	struct kprobe_ctlblk *kcb = get_kprobe_ctlblk();
-	unsigned long status = kcb->kprobe_status;
 	struct swap_insn_args *args = data;
 	struct ftrace_insn new_insn, *insn;
 	struct kprobe *p = args->p;
@@ -185,9 +183,7 @@ static int swap_instruction(void *data)
 			ftrace_generate_nop_insn(&new_insn);
 	}
 skip_ftrace:
-	kcb->kprobe_status = KPROBE_SWAP_INST;
 	s390_kernel_write(p->addr, &new_insn, len);
-	kcb->kprobe_status = status;
 	return 0;
 }
 NOKPROBE_SYMBOL(swap_instruction);
@@ -574,9 +570,6 @@ static int kprobe_trap_handler(struct pt_regs *regs, int trapnr)
 	const struct exception_table_entry *entry;
 
 	switch(kcb->kprobe_status) {
-	case KPROBE_SWAP_INST:
-		/* We are here because the instruction replacement failed */
-		return 0;
 	case KPROBE_HIT_SS:
 	case KPROBE_REENTER:
 		/*