[S390] ftrace: function tracer backend for s390

This implements just the basic function tracer (_mcount) backend for s390.
The dynamic variant will come later.

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

arch/s390/kernel/mcount.S

@@ -0,0 +1,56 @@
+/*
+ * Copyright IBM Corp. 2008
+ *
+ *   Author(s): Heiko Carstens <heiko.carstens@de.ibm.com>,
+ *
+ */
+
+#ifndef CONFIG_64BIT
+.globl _mcount
+_mcount:
+	stm	%r0,%r5,8(%r15)
+	st	%r14,56(%r15)
+	lr	%r1,%r15
+	ahi	%r15,-96
+	l	%r3,100(%r15)
+	la	%r2,0(%r14)
+	st	%r1,0(%r15)
+	la	%r3,0(%r3)
+	bras	%r14,0f
+	.long	ftrace_trace_function
+0:	l	%r14,0(%r14)
+	l	%r14,0(%r14)
+	basr	%r14,%r14
+	ahi	%r15,96
+	lm	%r0,%r5,8(%r15)
+	l	%r14,56(%r15)
+	br	%r14
+
+.globl ftrace_stub
+ftrace_stub:
+	br	%r14
+
+#else /* CONFIG_64BIT */
+
+.globl _mcount
+_mcount:
+	stmg	%r0,%r5,16(%r15)
+	stg	%r14,112(%r15)
+	lgr	%r1,%r15
+	aghi	%r15,-160
+	stg	%r1,0(%r15)
+	lgr	%r2,%r14
+	lg	%r3,168(%r15)
+	larl	%r14,ftrace_trace_function
+	lg	%r14,0(%r14)
+	basr	%r14,%r14
+	aghi	%r15,160
+	lmg	%r0,%r5,16(%r15)
+	lg	%r14,112(%r15)
+	br	%r14
+
+.globl ftrace_stub
+ftrace_stub:
+	br	%r14
+
+#endif /* CONFIG_64BIT */