perf trace: Move syscall table id <-> name routines to separate class

We're using libaudit for doing name to id and id to syscall name
translations, but that makes 'perf trace' to have to wait for newer
libaudit versions supporting recently added syscalls, such as
"userfaultfd" at the time of this changeset.

We have all the information right there, in the kernel sources, so move
this code to a separate place, wrapped behind functions that will
progressively use the kernel source files to extract the syscall table
for use in 'perf trace'.

Cc: Adrian Hunter <[e-mail]>
Cc: David Ahern <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Wang Nan <[e-mail]>
Link: http://lkml.kernel.org/n/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/builtin-trace.c

···
 #include "trace-event.h"
 #include "util/parse-events.h"
 #include "util/bpf-loader.h"
+#include "syscalltbl.h"
 
-#include <libaudit.h>
+#include <libaudit.h> /* FIXME: Still needed for audit_errno_to_name */
 #include <stdlib.h>
 #include <sys/mman.h>
 #include <linux/futex.h>
···
 
 struct trace {
 	struct perf_tool	tool;
-	struct {
-		int		machine;
-		int		open_id;
-	}			audit;
+	struct syscalltbl	*sctbl;
 	struct {
 		int		max;
 		struct syscall  *table;
···
 	bool			force;
 	bool			vfs_getname;
 	int			trace_pgfaults;
+	int			open_id;
 };
 
 struct tp_field {
···
 {
 	char tp_name[128];
 	struct syscall *sc;
-	const char *name = audit_syscall_to_name(id, trace->audit.machine);
+	const char *name = syscalltbl__name(trace->sctbl, id);
 
 	if (name == NULL)
 		return -1;
···
 
 	strlist__for_each(pos, trace->ev_qualifier) {
 		const char *sc = pos->s;
-		int id = audit_name_to_syscall(sc, trace->audit.machine);
+		int id = syscalltbl__id(trace->sctbl, sc);
 
 		if (id < 0) {
 			if (err == 0) {
···
 
 	ret = perf_evsel__sc_tp_uint(evsel, ret, sample);
 
-	if (id == trace->audit.open_id && ret >= 0 && ttrace->filename.pending_open) {
+	if (id == trace->open_id && ret >= 0 && ttrace->filename.pending_open) {
 		trace__set_fd_pathname(thread, ret, ttrace->filename.name);
 		ttrace->filename.pending_open = false;
 		++trace->stats.vfs_getname;
···
 		NULL
 	};
 	struct trace trace = {
-		.audit = {
-			.machine = audit_detect_machine(),
-			.open_id = audit_name_to_syscall("open", trace.audit.machine),
-		},
 		.syscalls = {
 			. max = -1,
 		},
···
 	signal(SIGFPE, sighandler_dump_stack);
 
 	trace.evlist = perf_evlist__new();
+	trace.sctbl = syscalltbl__new();
 
-	if (trace.evlist == NULL) {
+	if (trace.evlist == NULL || trace.sctbl == NULL) {
 		pr_err("Not enough memory to run!\n");
 		err = -ENOMEM;
 		goto out;
···
 			goto out;
 		}
 	}
+
+	trace.open_id = syscalltbl__id(trace.sctbl, "open");
 
 	if (ev_qualifier_str != NULL) {
 		const char *s = ev_qualifier_str;

tools/perf/util/Build

···
 libperf-y += map.o
 libperf-y += pstack.o
 libperf-y += session.o
+libperf-$(CONFIG_AUDIT) += syscalltbl.o
 libperf-y += ordered-events.o
 libperf-y += comm.o
 libperf-y += thread.o

tools/perf/util/syscalltbl.c

···
+/*
+ * System call table mapper
+ *
+ * (C) 2016 Arnaldo Carvalho de Melo <[e-mail]>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ */
+
+#include "syscalltbl.h"
+#include <string.h>
+#include <libaudit.h>
+
+
+struct syscalltbl *syscalltbl__new(void)
+{
+	struct syscalltbl *tbl = malloc(sizeof(*tbl));
+	if (tbl) {
+		tbl->audit_machine = audit_detect_machine();
+	}
+	return tbl;
+}
+
+void syscalltbl__delete(struct syscalltbl *tbl)
+{
+	free(tbl);
+}
+
+const char *syscalltbl__name(const struct syscalltbl *tbl, int id)
+{
+	return audit_syscall_to_name(id, tbl->audit_machine);
+}
+
+int syscalltbl__id(struct syscalltbl *tbl, const char *name)
+{
+	return audit_name_to_syscall(name, tbl->audit_machine);
+}

tools/perf/util/syscalltbl.h

···
+#ifndef __PERF_SYSCALLTBL_H
+#define __PERF_SYSCALLTBL_H
+
+struct syscalltbl {
+	union {
+		int audit_machine;
+	};
+};
+
+struct syscalltbl *syscalltbl__new(void);
+void syscalltbl__delete(struct syscalltbl *tbl);
+
+const char *syscalltbl__name(const struct syscalltbl *tbl, int id);
+int syscalltbl__id(struct syscalltbl *tbl, const char *name);
+
+#endif /* __PERF_SYSCALLTBL_H */