microblaze: ftrace: Add dynamic trace support

With dynamic function tracer, by default, _mcount is defined as an
"empty" function, it returns directly without any more action. When
enabling it in user-space, it will jump to a real tracing
function(ftrace_caller), and do the real job for us.

Differ from the static function tracer, dynamic function tracer provides
two functions ftrace_make_call()/ftrace_make_nop() to enable/disable the
tracing of some indicated kernel functions(set_ftrace_filter).

In the kernel version, there is only one "_mcount" string for every
kernel function, so, we just need to match this one in mcount_regex of
scripts/recordmcount.pl.

For more information please look at code and Documentation/trace folder.

Steven ACK that scripts/recordmcount.pl part.

Acked-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Michal Simek <monstr@monstr.eu>

1 files changed, 13 insertions, 0 deletions

diff --git a/arch/microblaze/kernel/mcount.S b/arch/microblaze/kernel/mcount.S
index 97eef3eea944..30aaf8fb55b2 100644
--- a/arch/microblaze/kernel/mcount.S
+++ b/arch/microblaze/kernel/mcount.S
@@ -83,6 +83,12 @@ ENTRY(ftrace_stub)
         nop;
 
 ENTRY(_mcount)
+#ifdef CONFIG_DYNAMIC_FTRACE
+ENTRY(ftrace_caller)
+        /* MS: It is just barrier which is removed from C code */
+        rtsd    r15, 8
+        nop
+#endif /* CONFIG_DYNAMIC_FTRACE */
         SAVE_REGS
         swi     r15, r1, 0;
         /* MS: HAVE_FUNCTION_TRACE_MCOUNT_TEST begin of checking */
@@ -90,12 +96,19 @@ ENTRY(_mcount)
         bneid   r5, end;
         nop;
         /* MS: HAVE_FUNCTION_TRACE_MCOUNT_TEST end of checking */
+#ifndef CONFIG_DYNAMIC_FTRACE
         /* MS: test function trace if is taken or not */
         lwi     r20, r0, ftrace_trace_function;
         addik   r6, r0, ftrace_stub;
         cmpu    r5, r20, r6; /* ftrace_trace_function != ftrace_stub */
         beqid   r5, end; /* MS: not taken -> jump over */
         nop;
+#else /* CONFIG_DYNAMIC_FTRACE */
+NOALIGN_ENTRY(ftrace_call)
+/* instruction for setup imm FUNC_part1, addik r20, r0, FUNC_part2 */
+        nop
+        nop
+#endif /* CONFIG_DYNAMIC_FTRACE */
 /* static normal trace */
         lwi     r6, r1, 120; /* MS: load parent addr */
         addik   r5, r15, 0; /* MS: load current function addr */