+core_initcall(init_ftrace_syscalls);
+
+#ifdef CONFIG_PERF_EVENTS
+
+static DECLARE_BITMAP(enabled_perf_enter_syscalls, NR_syscalls);
+static DECLARE_BITMAP(enabled_perf_exit_syscalls, NR_syscalls);
+static int sys_perf_refcount_enter;
+static int sys_perf_refcount_exit;
+
+static void perf_syscall_enter(struct pt_regs *regs, long id)
+{
+ struct syscall_metadata *sys_data;
+ struct syscall_trace_enter *rec;
+ unsigned long flags;
+ int syscall_nr;
+ int rctx;
+ int size;
+
+ syscall_nr = syscall_get_nr(current, regs);
+ if (!test_bit(syscall_nr, enabled_perf_enter_syscalls))
+ return;
+
+ sys_data = syscall_nr_to_meta(syscall_nr);
+ if (!sys_data)
+ return;
+
+ /* get the size after alignment with the u32 buffer size field */
+ size = sizeof(unsigned long) * sys_data->nb_args + sizeof(*rec);
+ size = ALIGN(size + sizeof(u32), sizeof(u64));
+ size -= sizeof(u32);
+
+ if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
+ "perf buffer not large enough"))
+ return;
+
+ rec = (struct syscall_trace_enter *)perf_trace_buf_prepare(size,
+ sys_data->enter_event->id, &rctx, &flags);
+ if (!rec)
+ return;
+
+ rec->nr = syscall_nr;
+ syscall_get_arguments(current, regs, 0, sys_data->nb_args,
+ (unsigned long *)&rec->args);
+ perf_trace_buf_submit(rec, size, rctx, 0, 1, flags, regs);
+}
+
+int perf_sysenter_enable(struct ftrace_event_call *call)
+{
+ int ret = 0;
+ int num;
+
+ num = ((struct syscall_metadata *)call->data)->syscall_nr;
+
+ mutex_lock(&syscall_trace_lock);
+ if (!sys_perf_refcount_enter)
+ ret = register_trace_sys_enter(perf_syscall_enter);
+ if (ret) {
+ pr_info("event trace: Could not activate"
+ "syscall entry trace point");
+ } else {
+ set_bit(num, enabled_perf_enter_syscalls);
+ sys_perf_refcount_enter++;
+ }
+ mutex_unlock(&syscall_trace_lock);
+ return ret;
+}
+
+void perf_sysenter_disable(struct ftrace_event_call *call)
+{
+ int num;
+
+ num = ((struct syscall_metadata *)call->data)->syscall_nr;
+
+ mutex_lock(&syscall_trace_lock);
+ sys_perf_refcount_enter--;
+ clear_bit(num, enabled_perf_enter_syscalls);
+ if (!sys_perf_refcount_enter)
+ unregister_trace_sys_enter(perf_syscall_enter);
+ mutex_unlock(&syscall_trace_lock);
+}
+
+static void perf_syscall_exit(struct pt_regs *regs, long ret)
+{
+ struct syscall_metadata *sys_data;
+ struct syscall_trace_exit *rec;
+ unsigned long flags;
+ int syscall_nr;
+ int rctx;
+ int size;
+
+ syscall_nr = syscall_get_nr(current, regs);
+ if (!test_bit(syscall_nr, enabled_perf_exit_syscalls))
+ return;
+
+ sys_data = syscall_nr_to_meta(syscall_nr);
+ if (!sys_data)
+ return;
+
+ /* We can probably do that at build time */
+ size = ALIGN(sizeof(*rec) + sizeof(u32), sizeof(u64));
+ size -= sizeof(u32);
+
+ /*
+ * Impossible, but be paranoid with the future
+ * How to put this check outside runtime?
+ */
+ if (WARN_ONCE(size > PERF_MAX_TRACE_SIZE,
+ "exit event has grown above perf buffer size"))
+ return;
+
+ rec = (struct syscall_trace_exit *)perf_trace_buf_prepare(size,
+ sys_data->exit_event->id, &rctx, &flags);
+ if (!rec)
+ return;
+
+ rec->nr = syscall_nr;
+ rec->ret = syscall_get_return_value(current, regs);
+
+ perf_trace_buf_submit(rec, size, rctx, 0, 1, flags, regs);
+}
+
+int perf_sysexit_enable(struct ftrace_event_call *call)
+{
+ int ret = 0;
+ int num;
+
+ num = ((struct syscall_metadata *)call->data)->syscall_nr;
+
+ mutex_lock(&syscall_trace_lock);
+ if (!sys_perf_refcount_exit)
+ ret = register_trace_sys_exit(perf_syscall_exit);
+ if (ret) {
+ pr_info("event trace: Could not activate"
+ "syscall exit trace point");
+ } else {
+ set_bit(num, enabled_perf_exit_syscalls);
+ sys_perf_refcount_exit++;
+ }
+ mutex_unlock(&syscall_trace_lock);
+ return ret;
+}
+
+void perf_sysexit_disable(struct ftrace_event_call *call)
+{
+ int num;
+
+ num = ((struct syscall_metadata *)call->data)->syscall_nr;
+
+ mutex_lock(&syscall_trace_lock);
+ sys_perf_refcount_exit--;
+ clear_bit(num, enabled_perf_exit_syscalls);
+ if (!sys_perf_refcount_exit)
+ unregister_trace_sys_exit(perf_syscall_exit);
+ mutex_unlock(&syscall_trace_lock);
+}
+
+#endif /* CONFIG_PERF_EVENTS */
+