This is the backport to 5.15. -- Steve ------------------ original commit in Linus's tree ------------------ >From f04dec93466a0481763f3b56cdadf8076e28bfbf Mon Sep 17 00:00:00 2001 From: "Steven Rostedt (Google)" <rostedt@xxxxxxxxxxx> Date: Sat, 20 Aug 2022 09:43:19 -0400 Subject: [PATCH] tracing/eprobes: Fix reading of string fields 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@xxxxxxxxxxx Cc: stable@xxxxxxxxxxxxxxx Cc: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Tzvetomir Stoyanov <tz.stoyanov@xxxxxxxxx> Cc: Tom Zanussi <zanussi@xxxxxxxxxx> Fixes: 7491e2c44278 ("tracing: Add a probe that attaches to trace events") Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Signed-off-by: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx> --- kernel/trace/trace_eprobe.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) Index: linux-test.git/kernel/trace/trace_eprobe.c =================================================================== --- linux-test.git.orig/kernel/trace/trace_eprobe.c 2022-08-22 13:36:56.320863048 -0400 +++ linux-test.git/kernel/trace/trace_eprobe.c 2022-08-22 13:36:56.316863048 -0400 @@ -320,6 +320,24 @@ static unsigned long get_event_field(str 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)
