perf trace: Allow printing syscall return values in hex

event_format->flags has a FIELD_IS_POINTER, but it is not set for
the sys_exit 'ret' field in syscalls like mmap, so we need a way to
ask for hex printing for pointer returns and keep things like 'read'
returns printing in decimal.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-lfuveegw4od1t08n7bsmonrm@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/builtin-trace.c

@@ -22,13 +22,18 @@ static struct syscall_fmt {
 	const char *alias;
 	bool	   errmsg;
 	bool	   timeout;
+	bool	   hexret;
 } syscall_fmts[] = {
 	{ .name	    = "access",	    .errmsg = true, },
 	{ .name	    = "arch_prctl", .errmsg = true, .alias = "prctl", },
+	{ .name	    = "brk",	    .hexret = true, },
+	{ .name	    = "mmap",	    .hexret = true, },
 	{ .name	    = "connect",    .errmsg = true, },
 	{ .name	    = "fstat",	    .errmsg = true, .alias = "newfstat", },
 	{ .name	    = "fstatat",    .errmsg = true, .alias = "newfstatat", },
 	{ .name	    = "futex",	    .errmsg = true, },
+	{ .name	    = "mmap",	    .hexret = true, },
+	{ .name	    = "mremap",	    .hexret = true, },
 	{ .name	    = "open",	    .errmsg = true, },
 	{ .name	    = "poll",	    .errmsg = true, .timeout = true, },
 	{ .name	    = "ppoll",	    .errmsg = true, .timeout = true, },
@@ -475,6 +480,8 @@ static int trace__sys_exit(struct trace *trace, struct perf_evsel *evsel,
 		fprintf(trace->output, ") = -1 %s %s", e, emsg);
 	} else if (ret == 0 && sc->fmt->timeout)
 		fprintf(trace->output, ") = 0 Timeout");
+	else if (sc->fmt->hexret)
+		fprintf(trace->output, ") = %#x", ret);
 	else
 		goto signed_print;