perf unwind: Check the target platform before assigning unwind methods

Currently, 'perf script' uses host unwind methods to parse perf.data
callchain info without taking the target architecture into account, i.e.
assuming the perf.data file was generated on the same machine where the
analysis is being performed. So we get wrong result without any warnings
when unwinding callchains of x86(32-bit) on x86(64-bit) machine.

This patch adds an extra step that checks the target platform before
assigning unwind methods. In later patches in this series, we can use
this info to assign the right unwind methods for supported platforms.

Committer note:

After fixing it to register the local unwinder for live mode tools
('perf trace', 'perf top'), i.e. tools that don't use a perf.data file,
it works as intended and passes the 'perf test unwind' test:

  # perf trace -e nanosleep --call dwarf usleep 1
     0.328 ( 0.058 ms): usleep/11115 nanosleep(rqtp: 0x7fff083fa480) = 0
                                       __nanosleep_nocancel+0x7 (/usr/lib64/libc-2.22.so)
                                       usleep+0x34 (/usr/lib64/libc-2.22.so)
                                       main+0x1eb (/usr/bin/usleep)
                                       __libc_start_main+0xf0 (/usr/lib64/libc-2.22.so)
                                       _start+0x29 (/usr/bin/usleep)
  # perf test 48
  48: Test dwarf unwind         : Ok
  #

Signed-off-by: He Kuang <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Ekaterina Tumanova <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
Cc: Kan Liang <[email protected]>
Cc: Masami Hiramatsu <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Pekka Enberg <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Stephane Eranian <[email protected]>
Cc: Sukadev Bhattiprolu <[email protected]>
Cc: Wang Nan <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
[ Fixed exit path for 'live' mode tools, where we need to default to local unwinding ]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

0 files changed, 0 insertions, 0 deletions