s390/ptrace: add last_break member to pt_regs

Instead of using args[0] for the value of the last breaking event
address register, add a member to make things more obvious.
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>

arch/s390/include/asm/ptrace.h

@@ -96,6 +96,7 @@ struct pt_regs {
 	};
 	unsigned long flags;
 	unsigned long cr1;
+	unsigned long last_break;
 };
 
 /*

arch/s390/kernel/dumpstack.c

@@ -152,7 +152,7 @@ void show_stack(struct task_struct *task, unsigned long *stack,
 static void show_last_breaking_event(struct pt_regs *regs)
 {
 	printk("Last Breaking-Event-Address:\n");
-	printk(" [<%016lx>] %pSR\n", regs->args[0], (void *)regs->args[0]);
+	printk(" [<%016lx>] %pSR\n", regs->last_break, (void *)regs->last_break);
 }
 
 void show_registers(struct pt_regs *regs)

arch/s390/kernel/traps.c

@@ -314,7 +314,7 @@ void noinstr __do_pgm_check(struct pt_regs *regs)
 		if (last_break < 4096)
 			last_break = 1;
 		current->thread.last_break = last_break;
-		regs->args[0] = last_break;
+		regs->last_break = last_break;
 	}
 
 	if (S390_lowcore.pgm_code & 0x0200) {