tracing/probes: Have kprobes and uprobes use $COMM too

Both $comm and $COMM can be used to get current->comm in eprobes and the
filtering and histogram logic. Make kprobes and uprobes consistent in this
regard and allow both $comm and $COMM as well. Currently kprobes and
uprobes only handle $comm, which is inconsistent with the other utilities,
and can be confusing to users.

Link: https://lkml.kernel.org/r/20220820134401.317014913@goodmis.org
Link: https://lore.kernel.org/all/20220820220442.776e1ddaf8836e82edb34d01@kernel.org/

Cc: stable@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Tzvetomir Stoyanov <tz.stoyanov@gmail.com>
Cc: Tom Zanussi <zanussi@kernel.org>
Fixes: 5330592 ("tracing: probeevent: Introduce new argument fetching code")
Suggested-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

kernel/trace/trace_probe.c

@@ -314,7 +314,7 @@ static int parse_probe_vars(char *arg, const struct fetch_type *t,
  }
  } else
  goto inval_var;
- } else if (strcmp(arg, "comm") == 0) {
+ } else if (strcmp(arg, "comm") == 0 || strcmp(arg, "COMM") == 0) {
  code->op = FETCH_OP_COMM;
 #ifdef CONFIG_HAVE_FUNCTION_ARG_ACCESS_API
  } else if (((flags & TPARG_FL_MASK) ==
@@ -625,7 +625,8 @@ static int traceprobe_parse_probe_arg_body(const char *argv, ssize_t *size,
  * we can find those by strcmp. But ignore for eprobes.
  */
  if (!(flags & TPARG_FL_TPOINT) &&
- (strcmp(arg, "$comm") == 0 || strncmp(arg, "\\\"", 2) == 0)) {
+ (strcmp(arg, "$comm") == 0 || 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;