linux-kernel - [PATCH] tracing/eprobe: Fix eprobe filter to make a filter correctly

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Message-Id: <166823166395.1385292.8931770640212414483.stgit@devnote3>
Date:   Sat, 12 Nov 2022 14:41:04 +0900
From:   "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To:     Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>
Cc:     Rafael Mendonca <rafaelmendsr@...il.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>
Subject: [PATCH] tracing/eprobe: Fix eprobe filter to make a filter correctly

From: Masami Hiramatsu (Google) <mhiramat@...nel.org>

Since the eprobe filter was defined based on the eprobe's trace event
itself, it doesn't work correctly. Use the original trace event of
the eprobe when making the filter so that the filter works correctly.

Without this fix:

 # echo 'e syscalls/sys_enter_openat \
	flags_rename=$flags:u32 if flags < 1000' >> dynamic_events
 # echo 1 > events/eprobes/sys_enter_openat/enable
[  114.551550] event trace: Could not enable event sys_enter_openat
-bash: echo: write error: Invalid argument

With this fix:
 # echo 'e syscalls/sys_enter_openat \
	flags_rename=$flags:u32 if flags < 1000' >> dynamic_events
 # echo 1 > events/eprobes/sys_enter_openat/enable
 # tail trace
cat-241     [000] ...1.   266.498449: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0
cat-242     [000] ...1.   266.977640: sys_enter_openat: (syscalls.sys_enter_openat) flags_rename=0

Fixes: 752be5c5c910 ("tracing/eprobe: Add eprobe filter support")
Reported-by: Rafael Mendonca <rafaelmendsr@...il.com>
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@...nel.org>
---
 kernel/trace/trace_eprobe.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/trace/trace_eprobe.c b/kernel/trace/trace_eprobe.c
index fe4833a7b7b3..1c3096ab2fe7 100644
--- a/kernel/trace/trace_eprobe.c
+++ b/kernel/trace/trace_eprobe.c
@@ -643,7 +643,7 @@ new_eprobe_trigger(struct trace_eprobe *ep, struct trace_event_file *file)
 	INIT_LIST_HEAD(&trigger->list);
 
 	if (ep->filter_str) {
-		ret = create_event_filter(file->tr, file->event_call,
+		ret = create_event_filter(file->tr, ep->event,
 					ep->filter_str, false, &filter);
 		if (ret)
 			goto error;