tracing: Call arch_init_ftrace_syscalls at boot

Call arch_init_ftrace_syscalls at boot, so we can determine early the
set of syscalls for the syscall trace events.

Signed-off-by: Jason Baron <jbaron@redhat.com>
Cc: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: Jiaying Zhang <jiayingz@google.com>
Cc: Martin Bligh <mbligh@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Masami Hiramatsu <mhiramat@redhat.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>

arch/x86/kernel/ftrace.c

@@ -516,31 +516,24 @@ int syscall_name_to_nr(char *name)
 	return -1;
 }
 
-void arch_init_ftrace_syscalls(void)
+static int __init arch_init_ftrace_syscalls(void)
 {
 	int i;
 	struct syscall_metadata *meta;
 	unsigned long **psys_syscall_table = &sys_call_table;
-	static atomic_t refs;
-
-	if (atomic_inc_return(&refs) != 1)
-		goto end;
 
 	syscalls_metadata = kzalloc(sizeof(*syscalls_metadata) *
 					FTRACE_SYSCALL_MAX, GFP_KERNEL);
 	if (!syscalls_metadata) {
 		WARN_ON(1);
-		return;
+		return -ENOMEM;
 	}
 
 	for (i = 0; i < FTRACE_SYSCALL_MAX; i++) {
 		meta = find_syscall_meta(psys_syscall_table[i]);
 		syscalls_metadata[i] = meta;
 	}
-	return;
-
-	/* Paranoid: avoid overflow */
-end:
-	atomic_dec(&refs);
+	return 0;
 }
+arch_initcall(arch_init_ftrace_syscalls);
 #endif

include/trace/syscall.h

@@ -19,7 +19,6 @@ struct syscall_metadata {
 };
 
 #ifdef CONFIG_FTRACE_SYSCALLS
-extern void arch_init_ftrace_syscalls(void);
 extern struct syscall_metadata *syscall_nr_to_meta(int nr);
 extern void start_ftrace_syscalls(void);
 extern void stop_ftrace_syscalls(void);

kernel/trace/trace_syscalls.c

@@ -106,7 +106,6 @@ void start_ftrace_syscalls(void)
 	if (++refcount != 1)
 		goto unlock;
 
-	arch_init_ftrace_syscalls();
 	read_lock_irqsave(&tasklist_lock, flags);
 
 	do_each_thread(g, t) {