perf trace: Add mmap alias for s390

The s390 architecture maps sys_mmap (nr 90) into sys_old_mmap.  For this
reason perf trace can't find the proper syscall event to get args format
from and displays it wrongly as 'continued'.

To fix that fill the "alias" field with "old_mmap" for trace's mmap record
to get the correct translation.

Before:
     0.042 ( 0.011 ms): vest/43052 fstat(statbuf: 0x3ffff89fd90                ) = 0
     0.042 ( 0.028 ms): vest/43052  ... [continued]: mmap()) = 0x3fffd6e2000
     0.072 ( 0.025 ms): vest/43052 read(buf: 0x3fffd6e2000, count: 4096        ) = 6

After:
     0.045 ( 0.011 ms): fstat(statbuf: 0x3ffff8a0930                           ) = 0
     0.057 ( 0.018 ms): mmap(arg: 0x3ffff8a0858                                ) = 0x3fffd14a000
     0.076 ( 0.025 ms): read(buf: 0x3fffd14a000, count: 4096                   ) = 6

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/20170531113557.19175-1-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -681,6 +681,10 @@ static struct syscall_fmt {
 	{ .name	    = "mlockall",   .errmsg = true,
 	  .arg_scnprintf = { [0] = SCA_HEX, /* addr */ }, },
 	{ .name	    = "mmap",	    .hexret = true,
+/* The standard mmap maps to old_mmap on s390x */
+#if defined(__s390x__)
+	.alias = "old_mmap",
+#endif
 	  .arg_scnprintf = { [0] = SCA_HEX,	  /* addr */
 			     [2] = SCA_MMAP_PROT, /* prot */
 			     [3] = SCA_MMAP_FLAGS, /* flags */ }, },