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tracing/eprobes: Fix reading of string fields

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commit f04dec9346 upstream.

Currently when an event probe (eprobe) hooks to a string field, it does
not display it as a string, but instead as a number. This makes the field
rather useless. Handle the different kinds of strings, dynamic, static,
relational/dynamic etc.

Now when a string field is used, the ":string" type can be used to display
it:

  echo "e:sw sched/sched_switch comm=$next_comm:string" > dynamic_events

Link: https://lkml.kernel.org/r/20220820134400.959640191@goodmis.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: 7491e2c442 ("tracing: Add a probe that attaches to trace events")
Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Steven Rostedt (Google) 2022-08-20 09:43:19 -04:00 • committed by Justin Hammond
parent 9216041046
commit 6e022539b5
1 changed files with 18 additions and 0 deletions
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18
kernel/trace/trace_eprobe.c
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@ -320,6 +320,24 @@ static unsigned long get_event_field(struct fetch_insn *code, void *rec)
addr = rec + field->offset;
if (is_string_field(field)) {
switch (field->filter_type) {
case FILTER_DYN_STRING:
val = (unsigned long)(rec + (*(unsigned int *)addr & 0xffff));
break;
case FILTER_STATIC_STRING:
val = (unsigned long)addr;
break;
case FILTER_PTR_STRING:
val = (unsigned long)(*(char *)addr);
break;
default:
WARN_ON_ONCE(1);
return 0;
}
return val;
}
switch (field->size) {
case 1:
if (field->is_signed)