Decoding an Intel PT trace of the kernel requires an accurate kernel
object image.  This is provided by making a copy of kcore.  However the
copy needs to be made under the same conditions as the original
recording, and then it needs to be associated with the perf.data file.
The perf-with-kcore script does that.

The script also checks the permissions on the buildid cache and can be
used to fix them.  That is needed for distributions where root does not
have a home directory and consequently writes to the same buildid cache
as the user, resulting in cached files that the user does not have
access to.

Example:

$ ./perf-with-kcore
Usage: perf-with-kcore <perf sub-command> <perf.data directory> [<sub-command options> [ -- <workload>]]
       <perf sub-command> can be record, script, report or inject
   or: perf-with-kcore fix_buildid_cache_permissions
$ ./perf-with-kcore record pt_uname -e intel_pt// -- uname
Recording
Using /home/ahunter/bin/perf
perf version 3.15.rc3.g4549ba
/home/ahunter/bin/perf record -o pt_uname/perf.data -e intel_pt//  -- uname
Linux
[ perf record: Woken up 3 times to write data ]
[ perf record: Captured and wrote 0.023 MB pt_uname/perf.data ]
Copying kcore
[sudo] password for ahunter:
Done
$ tools/perf/perf-with-kcore.sh script pt_uname | head
Using /home/ahunter/bin/perf
perf version 3.15.rc3.g4549ba
/home/ahunter/bin/perf script -i pt_uname/perf.data --kallsyms=pt_uname/kcore_dir/kallsyms
         swapper     0 [002] 161533.969666: sched:sched_switch: swapper/2:0 [120] R ==> perf:11316 [120]
          :11315 11315 [003] 161533.969704: sched:sched_switch: perf:11315 [120] S ==> swapper/3:0 [120]
          :11316 11316 [002] 161533.969783: sched:sched_switch: perf:11316 [120] R ==> migration/2:33 [0]
             :33    33 [002] 161533.969791: sched:sched_switch: migration/2:33 [0] S ==> swapper/2:0 [120]
         swapper     0 [003] 161533.969792: sched:sched_switch: swapper/3:0 [120] R ==> perf:11316 [120]
          :11316 11316 [003] 161533.970062: branches:                 0 [unknown] ([unknown]) => ffffffff810532fa native_write_msr_safe ([kernel.kallsyms])
          :11316 11316 [003] 161533.970062: branches:  ffffffff810532fd native_write_msr_safe ([kernel.kallsyms]) => ffffffff81035b31 pt_config_start ([kernel.kallsyms])
Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1406786474-9306-30-git-send-email-adrian.hunter@intel.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>