[for-linus][PATCH 3/9] tracing/boottime: Fix kprobe event API usage

Steven Rostedt
2020-05-07T17:39:37Z

From: Masami Hiramatsu <mhiramat@kernel.org>

Fix boottime kprobe events to use API correctly for
multiple events.

For example, when we set a multiprobe kprobe events in
bootconfig like below,

ftrace.event.kprobes.myevent {
probes = "vfs_read $arg1 $arg2", "vfs_write $arg1 $arg2"
}

This cause an error;

trace_boot: Failed to add probe: p:kprobes/myevent (null) vfs_read $arg1 $arg2 vfs_write $arg1 $arg2

This shows the 1st argument becomes NULL and multiprobes
are merged to 1 probe.

Link: http://lkml.kernel.org/r/158779375766.6082.201939936008972838.stgit@devnote2

Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 29a154810546 ("tracing: Change trace_boot to use kprobe_event interface")
Reviewed-by: Tom Zanussi <zanussi@kernel.org>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
---
kernel/trace/trace_boot.c | 20 ++++++++------------
1 file changed, 8 insertions(+), 12 deletions(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 06d7feb5255f..9de29bb45a27 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -95,24 +95,20 @@ trace_boot_add_kprobe_event(struct xbc_node *node, const char *event)
struct xbc_node *anode;
char buf[MAX_BUF_LEN];
const char *val;
- int ret;
+ int ret = 0;

- kprobe_event_cmd_init(&cmd, buf, MAX_BUF_LEN);
+ xbc_node_for_each_array_value(node, "probes", anode, val) {
+ kprobe_event_cmd_init(&cmd, buf, MAX_BUF_LEN);

- ret = kprobe_event_gen_cmd_start(&cmd, event, NULL);
- if (ret)
- return ret;
+ ret = kprobe_event_gen_cmd_start(&cmd, event, val);
+ if (ret)
+ break;

- xbc_node_for_each_array_value(node, "probes", anode, val) {
- ret = kprobe_event_add_field(&cmd, val);
+ ret = kprobe_event_gen_cmd_end(&cmd);
if (ret)
- return ret;
+ pr_err("Failed to add probe: %s\n", buf);
}

- ret = kprobe_event_gen_cmd_end(&cmd);
- if (ret)
- pr_err("Failed to add probe: %s\n", buf);
-
return ret;
}
#else
--
2.26.2