perf test record_probe_libc_inet_pton: Fix failure due to extra inet_pton()...

perf test record_probe_libc_inet_pton: Fix failure due to extra inet_pton() backtrace in glibc >= 2.35

Starting with glibc 2.35 there are extra inet_pton() calls when doing a
IPv6 ping as in one of the 'perf test' entry, which makes it fail:

  # perf test inet_pton
  89: probe libc's inet_pton & backtrace it with ping   : FAILED!
  #

If we look at what this script is expecting (commenting out the removal
of the temporary files in it):

  # cat /tmp/expected.aT6
  ping[][0-9 \.:]+probe_libc:inet_pton: \([[:xdigit:]]+\)
  .*inet_pton\+0x[[:xdigit:]]+[[:space:]]\(/usr/lib64/libc.so.6|inlined\)$
  getaddrinfo\+0x[[:xdigit:]]+[[:space:]]\(/usr/lib64/libc.so.6\)$
  .*(\+0x[[:xdigit:]]+|\[unknown\])[[:space:]]\(.*/bin/ping.*\)$
  #

And looking at what we are getting out of 'perf script', to match with
the above:

  # cat /tmp/perf.script.IUC
  ping 623883 [006] 265438.471610: probe_libc:inet_pton: (7f32bcf314c0)
                    1314c0 __GI___inet_pton+0x0 (/usr/lib64/libc.so.6)
                     29510 __libc_start_call_main+0x80 (/usr/lib64/libc.so.6)

  ping 623883 [006] 265438.471664: probe_libc:inet_pton: (7f32bcf314c0)
                    1314c0 __GI___inet_pton+0x0 (/usr/lib64/libc.so.6)
                     fa6c6 getaddrinfo+0x126 (/usr/lib64/libc.so.6)
                      491e [unknown] (/usr/bin/ping)
  #

We see that its just the first call to inet_pton() that didn't came thru
getaddrinfo(), so if we ignore the first the script matches what it
expects, testing that using 'perf probe' + 'perf record' + 'perf script'
with callchains on userspace targets is producing the expected results.

Since we don't have a 'perf script --skip' to help us here, use tac +
grep to do that, resulting in a one liner that makes this script work on
both older glibc versions as well as with 2.35.

With it, on fedora 36, x86, glibc 2.35:

  # perf test inet_pton
   90: probe libc's inet_pton & backtrace it with ping                 : Ok
  # perf test -v inet_pton
   90: probe libc's inet_pton & backtrace it with ping                 :
  --- start ---
  test child forked, pid 627197
  ping 627220 1 267956.962402: probe_libc:inet_pton_1: (7f488bf314c0)
  1314c0 __GI___inet_pton+0x0 (/usr/lib64/libc.so.6)
  fa6c6 getaddrinfo+0x126 (/usr/lib64/libc.so.6)
  491e n (/usr/bin/ping)
  test child finished with 0
  ---- end ----
  probe libc's inet_pton & backtrace it with ping: Ok
  #

And on Ubuntu 22.04.1 LTS on a Libre Computer ROC-RK3399-PC arm64 system:

Before this patch it works (see that the script used has no 'tac' to
remove the first event):

  root@roc-rk3399-pc:~# dpkg -l | grep libc-bin
  ii  libc-bin                                2.35-0ubuntu3.1                         arm64        GNU C Library: Binaries
  root@roc-rk3399-pc:~# grep -w tac ~acme/libexec/perf-core/tests/shell/record+probe_libc_inet_pton.sh
  root@roc-rk3399-pc:~# perf test inet_pton
   86: probe libc's inet_pton & backtrace it with ping                 : Ok
  root@roc-rk3399-pc:~# perf test -v inet_pton
   86: probe libc's inet_pton & backtrace it with ping                 :
  --- start ---
  test child forked, pid 1375
  ping 1399 [000] 4114.417450: probe_libc:inet_pton: (ffffb3e26120)
  106120 inet_pton+0x0 (/usr/lib/aarch64-linux-gnu/libc.so.6)
  d18bc getaddrinfo+0xec (/usr/lib/aarch64-linux-gnu/libc.so.6)
  2b68 [unknown] (/usr/bin/ping)
  test child finished with 0
  ---- end ----
  probe libc's inet_pton & backtrace it with ping: Ok
  root@roc-rk3399-pc:~#

And after it continues to work:

  root@roc-rk3399-pc:~# grep -w tac ~acme/libexec/perf-core/tests/shell/record+probe_libc_inet_pton.sh
  	perf script -i $perf_data | tac | grep -m1 ^ping -B9 | tac > $perf_script
  root@roc-rk3399-pc:~# perf test inet_pton
   86: probe libc's inet_pton & backtrace it with ping                 : Ok
  root@roc-rk3399-pc:~# perf test -v inet_pton
   86: probe libc's inet_pton & backtrace it with ping                 :
  --- start ---
  test child forked, pid 6995
  ping 7019 [005] 4832.160741: probe_libc:inet_pton: (ffffa62e6120)
  106120 inet_pton+0x0 (/usr/lib/aarch64-linux-gnu/libc.so.6)
  d18bc getaddrinfo+0xec (/usr/lib/aarch64-linux-gnu/libc.so.6)
  2b68 [unknown] (/usr/bin/ping)
  test child finished with 0
  ---- end ----
  probe libc's inet_pton & backtrace it with ping: Ok
  root@roc-rk3399-pc:~#
Reported-by: Thomas Richter <tmricht@linux.ibm.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Link: http://lore.kernel.org/lkml/Y7QyPkPlDYip3cZH@kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/tests/shell/record+probe_libc_inet_pton.sh

@@ -57,7 +57,7 @@ trace_libc_inet_pton_backtrace() {
 	perf_data=`mktemp -u /tmp/perf.data.XXX`
 	perf_script=`mktemp -u /tmp/perf.script.XXX`
 	perf record -e $event_name/$eventattr/ -o $perf_data ping -6 -c 1 ::1 > /dev/null 2>&1
-	perf script -i $perf_data > $perf_script
+	perf script -i $perf_data | tac | grep -m1 ^ping -B9 | tac > $perf_script
 
 	exec 3<$perf_script
 	exec 4<$expected