perf machine: Include data symbols in the kernel map

When 'perf record -d' is used, it needs data mmaps to symbolize global
data.  But it missed to collect kernel data maps so it cannot symbolize
them.  Instead of having a separate map, just increase the kernel map
size to include the data section.

Probably we can have a separate kernel map for data, but the current
code assumes a single kernel map.  So it'd require more changes in other
places and looks error-prone.  I decided not to go that way for now.

Also it seems the kernel module size already includes the data section.

For example, my system has the following.

  $ grep -e _stext -e _etext -e _edata /proc/kallsyms
  ffffffff99800000 T _stext
  ffffffff9a601ac8 T _etext
  ffffffff9b446a00 D _edata

Size of the text section is (0x9a601ac8 - 0x99800000 = 0xe01ac8) and
size including data section is (0x9b446a00 - 0x99800000 = 0x1c46a00).

Before:
  $ perf record -d true

  $ perf report -D | grep MMAP | head -1
  0 0 0x460 [0x60]: PERF_RECORD_MMAP -1/0: [0xffffffff99800000(0xe01ac8) @ 0xffffffff99800000]: x [kernel.kallsyms]_text
                                                               ^^^^^^^^
                                                                 here
After:
  $ perf report -D | grep MMAP | head -1
  0 0 0x460 [0x60]: PERF_RECORD_MMAP -1/0: [0xffffffff99800000(0x1c46a00) @ 0xffffffff99800000]: x [kernel.kallsyms]_text
                                                               ^^^^^^^^^

Instead of just replacing it to _edata, try _edata first and then fall
back to _etext just in case.

Signed-off-by: Namhyung Kim <[email protected]>
Acked-by: Adrian Hunter <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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