On Fri, 19 Aug 2022 21:40:37 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx>
>
> The variable $comm is hard coded as a string, which is true for both
> kprobes and uprobes, but for event probes (eprobes) it is a field name. In
> most cases the "comm" field would be a string, but there's no guarantee of
> that fact.
>
> Do not assume that comm is a string. Not to mention, it currently forces
> comm fields to fault, as string processing for event probes is currently
> broken.
Indeed. There should be an event argument which names "comm".
Eprobe might refer it. BTW, does eprobe use any special common fields?
I originally introduced "$" variable for such special variables.
Thank you,
>
> Cc: stable@xxxxxxxxxxxxxxx
> Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events")
> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
> ---
> kernel/trace/trace_probe.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/trace/trace_probe.c b/kernel/trace/trace_probe.c
> index dec657af363c..23dcd52ad45c 100644
> --- a/kernel/trace/trace_probe.c
> +++ b/kernel/trace/trace_probe.c
> @@ -622,9 +622,10 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
>
> /*
> * Since $comm and immediate string can not be dereferenced,
> - * we can find those by strcmp.
> + * we can find those by strcmp. But ignore for eprobes.
> */
> - if (strcmp(arg, "$comm") == 0 || strncmp(arg, "\\\"", 2) == 0) {
> + if (!(flags & TPARG_FL_TPOINT) &&
> + strcmp(arg, "$comm") == 0 || strncmp(arg, "\\\"", 2) == 0) {
> /* The type of $comm must be "string", and not an array. */
> if (parg->count || (t && strcmp(t, "string")))
> goto out;
> --
> 2.35.1
--
Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
