Add get_unaligned_le16(), get_unaligned_le32 and get_unaligned_le64, same
as include/asm-generic/unaligned.h. And add include/asm-generic/unaligned.h
to check-headers.sh bringing tools/include/asm-generic/unaligned.h up to
date so that the kernel and tools versions match.

Use diagnostic pragmas to ignore -Wpacked used by perf build.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20231005190451.175568-2-adrian.hunter@intel.com
Link: https://lore.kernel.org/r/20231010142234.20061-1-adrian.hunter@intel.com
[ squashed check-header.sh addition ]
Signed-off-by: Namhyung Kim <namhyung@kernel.org>

Use get_unaligned() instead of memcpy() to access potentially unaligned
memory, which, when accessed through a pointer, leads to undefined
behavior. get_unaligned() describes much better what is happening there
anyway even if memcpy() does the job.

In addition, since perf tool builds with -Werror, it would fire with:

  util/intel-pt-decoder/../../../arch/x86/lib/insn.c: In function '__insn_get_emulate_prefix':
  tools/include/../include/asm-generic/unaligned.h:10:15: error: packed attribute is unnecessary [-Werror=packed]
     10 |  const struct { type x; } __packed *__pptr = (typeof(__pptr))(ptr); \

because -Werror=packed would complain if the packed attribute would have
no effect on the layout of the structure.

In this case, that is intentional so disable the warning only for that
compilation unit.

That part is Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>

No functional changes.

Fixes: 5ba1071f7554 ("x86/insn, tools/x86: Fix undefined behavior due to potential unaligned accesses")
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Masami Hiramatsu <mhiramat@kernel.org>
Tested-by: Stephen Rothwell <sfr@canb.auug.org.au>
Link: https://lkml.kernel.org/r/YVSsIkj9Z29TyUjE@zn.tnic