csky/ftrace: Add dynamic function tracer (include graph tracer)

Support dynamic ftrace including dynamic graph tracer. Gcc-csky with -pg
will produce call site in every function prologue and we can use these
call site to hook trace function.

gcc with -pg origin call site:
	push	lr
	jbsr	_mcount
	nop32
	nop32

If the (callee - caller)'s offset is in range of bsr instruction, we'll
modify code with:
	push	lr
	bsr	_mcount
	nop32
	nop32
Else if the (callee - caller)'s offset is out of bsr instrunction, we'll
modify code with:
	push	lr
	movih	r26, ...
	ori	r26, ...
	jsr	r26

(r26 is reserved for jsr link reg in csky abiv2 spec.)

Signed-off-by: Guo Ren <ren_guo@c-sky.com>

arch/csky/include/asm/ftrace.h

@@ -4,10 +4,26 @@
 #ifndef __ASM_CSKY_FTRACE_H
 #define __ASM_CSKY_FTRACE_H
 
-#define MCOUNT_INSN_SIZE 4
+#define MCOUNT_INSN_SIZE	14
 
 #define HAVE_FUNCTION_GRAPH_FP_TEST
 
 #define HAVE_FUNCTION_GRAPH_RET_ADDR_PTR
 
+#define MCOUNT_ADDR	((unsigned long)_mcount)
+
+#ifndef __ASSEMBLY__
+
+extern void _mcount(unsigned long);
+
+extern void ftrace_graph_call(void);
+
+static inline unsigned long ftrace_call_adjust(unsigned long addr)
+{
+	return addr;
+}
+
+struct dyn_arch_ftrace {
+};
+#endif /* !__ASSEMBLY__ */
 #endif /* __ASM_CSKY_FTRACE_H */