perf probe: Trying to read a 'ctx' named local variable

[Arnaldo Carvalho de Melo <acme@kernel.org>]

Hi Masami,

	Trying to use perf to debug perf I stumbled on this:

[root@quaco ~]# perf probe -x ~/bin/perf -L sigtrap_handler
<sigtrap_handler@/home/acme/git/perf-tools/tools/perf/tests/sigtrap.c:0>
      0  sigtrap_handler(int signum __maybe_unused, siginfo_t *info, void *ucontext __maybe_unused)
         {
                if (!__atomic_fetch_add(&ctx.signal_count, 1, __ATOMIC_RELAXED))
      3                 ctx.first_siginfo = *info;
      4         __atomic_fetch_sub(&ctx.tids_want_signal, syscall(SYS_gettid), __ATOMIC_RELAXED);
         }

         static void *test_thread(void *arg)

[root@quaco ~]# perf probe -x ~/bin/perf sigtrap_handler:4 "ctx.signal_count"
Failed to write event: Invalid argument
Please upgrade your kernel to at least 3.14 to have access to feature @ctx
  Error: Failed to add events.
[root@quaco ~]#

[root@quaco ~]# uname -a
Linux quaco 6.3.8-100.fc37.x86_64 #1 SMP PREEMPT_DYNAMIC Thu Jun 15 01:51:54 UTC 2023 x86_64 x86_64 x86_64 GNU/Linux
[root@quaco ~]# rpm -qa | grep kernel-debuginfo
kernel-debuginfo-common-x86_64-6.3.8-100.fc37.x86_64
kernel-debuginfo-6.3.8-100.fc37.x86_64
[root@quaco ~]#

-- 

- Arnaldo