perf trace: Fix SIGSEGV when processing syscall args

On powerpc, 'perf trace' is crashing with a SIGSEGV when trying to
process a perf.data file created with 'perf trace record -p':

  #0  0x00000001225b8988 in syscall_arg__scnprintf_augmented_string <snip> at builtin-trace.c:1492
  #1  syscall_arg__scnprintf_filename <snip> at builtin-trace.c:1492
  #2  syscall_arg__scnprintf_filename <snip> at builtin-trace.c:1486
  #3  0x00000001225bdd9c in syscall_arg_fmt__scnprintf_val <snip> at builtin-trace.c:1973
  #4  syscall__scnprintf_args <snip> at builtin-trace.c:2041
  #5  0x00000001225bff04 in trace__sys_enter <snip> at builtin-trace.c:2319

That points to the below code in tools/perf/builtin-trace.c:
	/*
	 * If this is raw_syscalls.sys_enter, then it always comes with the 6 possible
	 * arguments, even if the syscall being handled, say "openat", uses only 4 arguments
	 * this breaks syscall__augmented_args() check for augmented args, as we calculate
	 * syscall->args_size using each syscalls:sys_enter_NAME tracefs format file,
	 * so when handling, say the openat syscall, we end up getting 6 args for the
	 * raw_syscalls:sys_enter event, when we expected just 4, we end up mistakenly
	 * thinking that the extra 2 u64 args are the augmented filename, so just check
	 * here and avoid using augmented syscalls when the evsel is the raw_syscalls one.
	 */
	if (evsel != trace->syscalls.events.sys_enter)
		augmented_args = syscall__augmented_args(sc, sample, &augmented_args_size, trace->raw_augmented_syscalls_args_size);

As the comment points out, we should not be trying to augment the args
for raw_syscalls. However, when processing a perf.data file, we are not
initializing those properly. Fix the same.

Reported-by: Claudio Carvalho <[email protected]>
Signed-off-by: Naveen N. Rao <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Namhyung Kim <[email protected]>
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/builtin-trace.c

@@ -4280,6 +4280,7 @@ static int trace__replay(struct trace *trace)
 		goto out;
 
 	evsel = evlist__find_tracepoint_by_name(session->evlist, "raw_syscalls:sys_enter");
+	trace->syscalls.events.sys_enter = evsel;
 	/* older kernels have syscalls tp versus raw_syscalls */
 	if (evsel == NULL)
 		evsel = evlist__find_tracepoint_by_name(session->evlist, "syscalls:sys_enter");
@@ -4292,6 +4293,7 @@ static int trace__replay(struct trace *trace)
 	}
 
 	evsel = evlist__find_tracepoint_by_name(session->evlist, "raw_syscalls:sys_exit");
+	trace->syscalls.events.sys_exit = evsel;
 	if (evsel == NULL)
 		evsel = evlist__find_tracepoint_by_name(session->evlist, "syscalls:sys_exit");
 	if (evsel &&