kernel: 1. use prctl lsm hook; 2. refine sucompat hook

kernel/lsm_hook.c

@@ -0,0 +1,33 @@
+#include "asm-generic/errno.h"
+#include "linux/kernel.h"
+#include <linux/printk.h>
+#include <linux/security.h>
+#include <linux/lsm_hooks.h>
+#include <linux/module.h>
+#include <linux/version.h>
+
+#include "klog.h"
+#include "ksu.h"
+
+static int ksu_task_prctl(int option, unsigned long arg2, unsigned long arg3,
+			  unsigned long arg4, unsigned long arg5)
+{
+	ksu_handle_prctl(option, arg2, arg3, arg4, arg5);
+	return -ENOSYS;
+}
+
+static struct security_hook_list ksu_hooks[] = {
+	LSM_HOOK_INIT(task_prctl, ksu_task_prctl),
+};
+
+void ksu_lsm_hook_init(void)
+{
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(4, 11, 0)
+	security_add_hooks(ksu_hooks, ARRAY_SIZE(ksu_hooks), "ksu");
+#else
+	// https://elixir.bootlin.com/linux/v4.10.17/source/include/linux/lsm_hooks.h#L1892
+	security_add_hooks(ksu_hooks, ARRAY_SIZE(ksu_hooks));
+#endif
+
+	pr_info("security_add_hooks\n");
+}