linux-kernel - [PATCH v2 0/6] perf-probe: Improbe non-C language support

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Message-ID:  <173099112488.2431889.1181692857521683304.stgit@mhiramat.roam.corp.google.com>
Date: Thu,  7 Nov 2024 23:52:05 +0900
From: "Masami Hiramatsu (Google)" <mhiramat@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Dima Kogan <dima@...retsauce.net>,
	Alexander Lobakin <aleksander.lobakin@...el.com>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2 0/6] perf-probe: Improbe non-C language support

Hi,

Here is the 2nd version of patches for perf probe to improve non-C language
(e.g. Rust, Go) support. The previous version is here;

https://lore.kernel.org/all/173073702882.2098439.13342508872190995896.stgit@mhiramat.roam.corp.google.com/

In this version, Add a new error message [1/6], introduced `@*`
support[3/6], split str*_esq()[4/6], and use dwarf srclang to identify
the source code language[6/6].

The non-C symbols are demangled style in debuginfo, e.g. golang stores

----
$ ./perf probe -x /work/go/example/outyet/main -F main*
main.(*Server).ServeHTTP
main.(*Server).ServeHTTP.Print.func1
main.(*Server).poll
...
-----

And Rust stores
-----
$ ./perf probe -x /work/cro3/target/x86_64-unknown-linux-gnu/debug/cro3 -F cro3::cmd::servo*
cro3::cmd::servo::run
cro3::cmd::servo::run::CALLSITE
cro3::cmd::servo::run::CALLSITE::META
cro3::cmd::servo::run_control
-----

These symbols are not parsed correctly because it looks like a file name or
including line numbers (`:` caused it.) So, I decided to introduce the changes

 - filename MUST start from '@'. (so it is able to distinguish the filename
   and the function name)
 - Fix to allow backslash to escape to --lines option.
 - Introduce quotation mark support.
 - Replace non-alnum character to '_' for event name (for non-C symbols).

With these changes, we can run -L (--lines) on golang;

------
$ perf probe -x goexample/hello/hello -L \"main.main\"
<main.main@...rk/goexample/hello/hello.go:0>
      0  func main() {
                // Configure logging for a command-line program.
      2         log.SetFlags(0)
      3         log.SetPrefix("hello: ")

                // Parse flags.
      6         flag.Usage = usage
      7         flag.Parse()
------

And Rust
------
$ perf probe -x cro3 -L \"cro3::cmd::servo::run_show\"
<run_show@...rk/cro3/src/cmd/servo.rs:0>
      0  fn run_show(args: &ArgsShow) -> Result<()> {
      1      let list = ServoList::discover()?;
      2      let s = list.find_by_serial(&args.servo)?;
      3      if args.json {
      4          println!("{s}");
------

And event name are created automatically like below;

$ ./perf probe -x /work/go/example/outyet/main -D 'main.(*Server).poll'
p:probe_main/main_Server_poll /work/go/example/outyet/main:0x353040

$ ./perf probe -x cro3 -D \"cro3::cmd::servo::run_show\"
p:probe_cro3/cro3_cmd_servo_run_show /work/cro3/target/x86_64-unknown-linux-gnu/debug/cro3:0x197530

We still need some more work, but these shows how perf-probe can work
with other languages.

Thank you,

---

Masami Hiramatsu (Google) (6):
      perf-probe: Fix error message for failing to find line range
      perf-probe: Fix to ignore escaped characters in --lines option
      perf-probe: Accept FUNC@* to specify function name explicitly
      perf: Add strpbrk_esq() and strdup_esq() for escape and quote
      perf-probe: Introduce quotation marks support
      perf-probe: Replace unacceptable characters when generating event name


 tools/perf/util/probe-event.c  |  135 ++++++++++++++++++++++++++++------------
 tools/perf/util/probe-event.h  |    3 +
 tools/perf/util/probe-finder.c |   15 ++++
 tools/perf/util/probe-finder.h |    6 +-
 tools/perf/util/string.c       |  100 ++++++++++++++++++++++++++++++
 tools/perf/util/string2.h      |    2 +
 6 files changed, 217 insertions(+), 44 deletions(-)

--
Masami Hiramatsu (Google) <mhiramat@...nel.org>