perf tools: Avoid unaligned pointer operations

The sample data is 64-bit aligned basically but raw data starts with
32-bit length field and data follows. In perf_event__synthesize_sample
it treats the sample data as a 64-bit array. And it needs some trick
to update the raw data properly.

But it seems some compilers are not happy with this and the program dies
siliently. I found the sample parsing test failed without any messages
on affected systems.

Let's update the code to use a 32-bit pointer directly and make sure the
result is 64-bit aligned again. No functional changes intended.

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

tools/perf/util/synthetic-events.c

···
 	}
 
 	if (type & PERF_SAMPLE_RAW) {
-		u.val32[0] = sample->raw_size;
-		*array = u.val64;
-		array = (void *)array + sizeof(u32);
+		u32 *array32 = (void *)array;
 
-		memcpy(array, sample->raw_data, sample->raw_size);
-		array = (void *)array + sample->raw_size;
+		*array32 = sample->raw_size;
+		array32++;
+
+		memcpy(array32, sample->raw_data, sample->raw_size);
+		array = (void *)(array32 + (sample->raw_size / sizeof(u32)));
+
+		/* make sure the array is 64-bit aligned */
+		BUG_ON(((long)array) % sizeof(u64));
 	}
 
 	if (type & PERF_SAMPLE_BRANCH_STACK) {