Linux-Trace-Devel Archive on
 help / color / Atom feed
From: Sascha Ortmann <>
Subject: [PATCH v2] tracing/boottime: Fix kprobe multiple events
Date: Thu, 18 Jun 2020 18:33:01 +0200
Message-ID: <> (raw)
In-Reply-To: <>

Fix boottime kprobe events to report and abort after each failure when
adding probes.

As an example, when we try to set multiprobe kprobe events in
bootconfig like this:

ftrace.event.kprobes.vfsevents {
        probes = "vfs_read $arg1 $arg2,,
                 !error! not reported;?", // leads to error
                 "vfs_write $arg1 $arg2"

This will not work as expected. After 
commit da0f1f4167e3af69e ("tracing/boottime: Fix kprobe event API usage"), 
the function trace_boot_add_kprobe_event will not produce any error 
message when adding a probe fails at kprobe_event_gen_cmd_start. 
Furthermore, we continue to add probes when kprobe_event_gen_cmd_end fails
(and kprobe_event_gen_cmd_start did not fail). In this case the function 
even returns successfully when the last call to kprobe_event_gen_cmd_end
is successful.

The behaviour of reporting and aborting after failures is not

The function trace_boot_add_kprobe_event now reports each failure and
stops adding probes immediately.

Co-developed-by: Maximilian Werner <>
Signed-off-by: Maximilian Werner <>
Signed-off-by: Sascha Ortmann <>
 kernel/trace/trace_boot.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 9de29bb45a27..be893eb22071 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -101,12 +101,16 @@ trace_boot_add_kprobe_event(struct xbc_node *node, const char *event)
 		kprobe_event_cmd_init(&cmd, buf, MAX_BUF_LEN);
 		ret = kprobe_event_gen_cmd_start(&cmd, event, val);
-		if (ret)
+		if (ret) {
+			pr_err("Failed to generate probe: %s\n", buf);
+		}
 		ret = kprobe_event_gen_cmd_end(&cmd);
-		if (ret)
+		if (ret) {
 			pr_err("Failed to add probe: %s\n", buf);
+			break;
+		}
 	return ret;

  reply index

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-17 14:08 [PATCH] " Sascha Ortmann
2020-06-17 15:05 ` Steven Rostedt
2020-06-17 15:06   ` Steven Rostedt
2020-06-17 15:57     ` Maximilian Werner
2020-06-17 16:06       ` Steven Rostedt
2020-06-18  1:50 ` Masami Hiramatsu
2020-06-18 16:33   ` Sascha Ortmann [this message]
2020-06-19  1:58     ` [PATCH v2] " Masami Hiramatsu

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \ \ \ \ \ \ \ \ \ \

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

Linux-Trace-Devel Archive on

Archives are clonable:
	git clone --mirror linux-trace-devel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-trace-devel linux-trace-devel/ \
	public-inbox-index linux-trace-devel

Example config snippet for mirrors

Newsgroup available over NNTP:

AGPL code for this site: git clone