From: Sascha Ortmann sascha.ortmann@stud.uni-hannover.de

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 consistent.

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

Link: https://lkml.kernel.org/r/20200618163301.25854-1-sascha.ortmann@stud.uni-han...

Cc: stable@vger.kernel.org Cc: linux-kernel@i4.cs.fau.de Co-developed-by: Maximilian Werner maximilian.werner96@gmail.com Fixes: da0f1f4167e3 ("tracing/boottime: Fix kprobe event API usage") Acked-by: Masami Hiramatsu mhiramat@kernel.org Signed-off-by: Maximilian Werner maximilian.werner96@gmail.com Signed-off-by: Sascha Ortmann sascha.ortmann@stud.uni-hannover.de Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org --- 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 8b5490cb02bb..fa0fc08c6ef8 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); break; + }

ret = kprobe_event_gen_cmd_end(&cmd); - if (ret) + if (ret) { pr_err("Failed to add probe: %s\n", buf); + break; + } }

return ret;