microblaze: ftrace: Add dynamic function graph tracer

This patch add support for dynamic function graph tracer.

There is one my expactation that I can do flush_icache after
all code modification. On microblaze is this safer than do
flush for every entry. For icache is used name flush but
correct should be invalidation - this will be fix in upcomming
new cache implementaion and WB support.
Signed-off-by: Michal Simek <monstr@monstr.eu>

arch/microblaze/kernel/ftrace.c

@@ -206,4 +206,32 @@ int ftrace_update_ftrace_func(ftrace_func_t func)
 	return ret;
 }
 
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+unsigned int old_jump; /* saving place for jump instruction */
+
+int ftrace_enable_ftrace_graph_caller(void)
+{
+	unsigned int ret;
+	unsigned long ip = (unsigned long)(&ftrace_call_graph);
+
+	old_jump = *(unsigned int *)ip; /* save jump over instruction */
+	ret = ftrace_modify_code(ip, MICROBLAZE_NOP);
+	flush_icache();
+
+	pr_debug("%s: Replace instruction: 0x%x\n", __func__, old_jump);
+	return ret;
+}
+
+int ftrace_disable_ftrace_graph_caller(void)
+{
+	unsigned int ret;
+	unsigned long ip = (unsigned long)(&ftrace_call_graph);
+
+	ret = ftrace_modify_code(ip, old_jump);
+	flush_icache();
+
+	pr_debug("%s\n", __func__);
+	return ret;
+}
+#endif /* CONFIG_FUNCTION_GRAPH_TRACER */
 #endif /* CONFIG_DYNAMIC_FTRACE */

arch/microblaze/kernel/mcount.S

@@ -97,6 +97,7 @@ ENTRY(ftrace_caller)
 	nop;
 	/* MS: HAVE_FUNCTION_TRACE_MCOUNT_TEST end of checking */
 #ifdef CONFIG_FUNCTION_GRAPH_TRACER
+#ifndef CONFIG_DYNAMIC_FTRACE
 	lwi	r5, r0, ftrace_graph_return;
 	addik	r6, r0, ftrace_stub; /* asm implementation */
 	cmpu	r5, r5, r6; /* ftrace_graph_return != ftrace_stub */
@@ -108,6 +109,11 @@ ENTRY(ftrace_caller)
 	cmpu	r5, r5, r6; /* ftrace_graph_entry != ftrace_graph_entry_stub */
 	beqid	r5, end_graph_tracer;
 	nop;
+#else /* CONFIG_DYNAMIC_FTRACE */
+NOALIGN_ENTRY(ftrace_call_graph)
+	/* MS: jump over graph function - replaced from C code */
+	bri	end_graph_tracer
+#endif /* CONFIG_DYNAMIC_FTRACE */
 	addik	r5, r1, 120; /* MS: load parent addr */
 	addik	r6, r15, 0; /* MS: load current function addr */
 	bralid	r15, prepare_ftrace_return;