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From:   Masami Hiramatsu <mhiramat@kernel.org>
To:     Steven Rostedt <rostedt@goodmis.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Shuah Khan <skhan@linuxfoundation.org>
Cc:     mhiramat@kernel.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org, Randy Dunlap <rdunlap@infradead.org>,
        Ingo Molnar <mingo@kernel.org>, linux-kselftest@vger.kernel.org
Subject: [PATCH v3 5/8] tracing/uprobes: Support perf-style return probe
Date:   Thu, 10 Sep 2020 17:55:46 +0900
Message-Id: <159972814601.428528.7641183316212425445.stgit@devnote2>
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Support perf-style return probe ("SYMBOL%return") for uprobe events
as same as kprobe events does.

Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
---
 kernel/trace/trace.c        |    2 +-
 kernel/trace/trace_uprobe.c |   15 ++++++++++++++-
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 2c8c8f7ddef7..faf55f5dd99d 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5125,7 +5125,7 @@ static const char readme_msg[] =
   "place (kretprobe): [<module>:]<symbol>[+<offset>]%return|<memaddr>\n"
 #endif
 #ifdef CONFIG_UPROBE_EVENTS
-  "   place (uprobe): <path>:<offset>[(ref_ctr_offset)]\n"
+  "   place (uprobe): <path>:<offset>[%return][(ref_ctr_offset)]\n"
 #endif
 	"\t     args: <name>=fetcharg[:type]\n"
 	"\t fetcharg: %<register>, @<address>, @<symbol>[+|-<offset>],\n"
diff --git a/kernel/trace/trace_uprobe.c b/kernel/trace/trace_uprobe.c
index f4286c9bdeb4..fb5ec4e55484 100644
--- a/kernel/trace/trace_uprobe.c
+++ b/kernel/trace/trace_uprobe.c
@@ -528,7 +528,7 @@ static int register_trace_uprobe(struct trace_uprobe *tu)
 
 /*
  * Argument syntax:
- *  - Add uprobe: p|r[:[GRP/]EVENT] PATH:OFFSET [FETCHARGS]
+ *  - Add uprobe: p|r[:[GRP/]EVENT] PATH:OFFSET[%return][(REF)] [FETCHARGS]
  */
 static int trace_uprobe_create(int argc, const char **argv)
 {
@@ -617,6 +617,19 @@ static int trace_uprobe_create(int argc, const char **argv)
 		}
 	}
 
+	/* Check if there is %return suffix */
+	tmp = strchr(arg, '%');
+	if (tmp) {
+		if (!strcmp(tmp, "%return")) {
+			*tmp = '\0';
+			is_return = true;
+		} else {
+			trace_probe_log_err(tmp - filename, BAD_ADDR_SUFFIX);
+			ret = -EINVAL;
+			goto fail_address_parse;
+		}
+	}
+
 	/* Parse uprobe offset. */
 	ret = kstrtoul(arg, 0, &offset);
 	if (ret) {