From a1303af5d79eb13a658633a9fb0ce3aed0f7decf Mon Sep 17 00:00:00 2001
From: Masami Hiramatsu <mhiramat@kernel.org>
Date: Wed, 25 Apr 2018 21:21:26 +0900
Subject: tracing: probeevent: Add $argN for accessing function args

Add $argN special fetch variable for accessing function
arguments. This allows user to trace the Nth argument easily
at the function entry.

Note that this returns most probably assignment of registers
and stacks. In some case, it may not work well. If you need
to access correct registers or stacks you should use perf-probe.

Link: http://lkml.kernel.org/r/152465888632.26224.3412465701570253696.stgit@devbox

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
 kernel/trace/trace.c | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'kernel/trace/trace.c')

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index e7f99f513959..ec5b21778806 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4625,7 +4625,11 @@ static const char readme_msg[] =
 #endif
 	"\t     args: <name>=fetcharg[:type]\n"
 	"\t fetcharg: %<register>, @<address>, @<symbol>[+|-<offset>],\n"
+#ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
+	"\t           $stack<index>, $stack, $retval, $comm, $arg<N>\n"
+#else
 	"\t           $stack<index>, $stack, $retval, $comm\n"
+#endif
 	"\t     type: s8/16/32/64, u8/16/32/64, x8/16/32/64, string, symbol,\n"
 	"\t           b<bit-width>@<bit-offset>/<container-size>,\n"
 	"\t           <type>\\[<array-size>\\]\n"
-- 
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