We observed some crazy apps on Android set their comm to unprintable
string. For example:

  # cat /proc/10607/task/*/comm
  tencent.qqmusic
  ...
  Binder_2
  日志输出线  <-- Chinese word 'log output thread'
  WifiManager
  ...

'perf data convert' fails to convert perf.data with such string to CTF format.

For example:

  # cat << EOF > ./badguy.c
  #include <sys/prctl.h>
  int main(int argc, char *argv[])
  {
         prctl(PR_SET_NAME, "\xe6\x97\xa5\xe5\xbf\x97\xe8\xbe\x93\xe5\x87\xba\xe7\xba\xbf");
         while(1)
                 sleep(1);
         return 0;
  }
  EOF
  # gcc ./badguy.c
  # perf record -e sched:* ./a.out
  # perf data convert --to-ctf ./bad.ctf
  CTF stream 4 flush failed
  [ perf data convert: Converted 'perf.data' into CTF data './bad.ctf' ]
  [ perf data convert: Converted and wrote 0.008 MB (78 samples)  ]
  # babeltrace ./bad.ctf/
  [error] Packet size (18446744073709551615 bits) is larger than remaining file size (262144 bits).
  [error] Stream index creation error.
  [error] Open file stream error.
  [warning] [Context] Cannot open_trace of format ctf at path ./bad.ctf.
  [warning] [Context] cannot open trace "./bad.ctf" from ./bad.ctf/ for reading.
  [error] Cannot open any trace for reading.

  [error] opening trace "./bad.ctf/" for reading.

  [error] none of the specified trace paths could be opened.

This patch converts unprintable characters to hexadecimal word.

After applying this patch the above test works correctly:

  # ~/perf data convert --to-ctf ./good.ctf
  [ perf data convert: Converted 'perf.data' into CTF data './good.ctf' ]
  [ perf data convert: Converted and wrote 0.008 MB (78 samples) ]
  # babeltrace ./good.ctf
  ..
  [23:14:35.491665268] (+0.000001100) sched:sched_wakeup: { cpu_id = 4 }, { perf_ip = 0xFFFFFFFF810AEF33, perf_tid = 0, perf_pid = 0, perf_id = 5123, perf_period = 1, common_type = 270, common_flags = 45, common_preempt_count = 4, common_pid = 0, comm = "\xe6\x97\xa5\xe5\xbf\x97\xe8\xbe\x93\xe5\x87\xba\xe7\xba\xbf", pid = 1057, prio = 120, success = 1, target_cpu = 4 }
  [23:14:35.491666230] (+0.000000962) sched:sched_wakeup: { cpu_id = 4 }, { perf_ip = 0xFFFFFFFF810AEF33, perf_tid = 0, perf_pid = 0, perf_id = 5122, perf_period = 1, common_type = 270, common_flags = 45, common_preempt_count = 4, common_pid = 0, comm = "\xe6\x97\xa5\xe5\xbf\x97\xe8\xbe\x93\xe5\x87\xba\xe7\xba\xbf", pid = 1057, prio = 120, success = 1, target_cpu = 4 }
  ..

Committer note:

To build perf with libabeltrace, use:

  $ mkdir -p /tmp/build/perf
  $ make LIBBABELTRACE=1 LIBBABELTRACE_DIR=/usr/local O=/tmp/build/perf -C tools/perf install-bin

Or equivalent (no O=, fixup LIBBABELTRACE_DIR, etc).
Signed-off-by: Wang Nan <wangnan0@huawei.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: pi3orama@163.com
Link: http://lkml.kernel.org/r/1464348951-179595-1-git-send-email-wangnan0@huawei.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>