Add UID scanner functionality and related infrastructure

- Introduced a new module `uid_scanner` in userspace for managing UID scanning.
- Created a new GitHub Actions workflow for building the `user_scanner`.
- Implemented kernel communication in `throne_comm.c` and `throne_comm.h` to handle user space updates and rescan requests.
- Developed the `uid_scanner` daemon in C to scan user directories and manage UID whitelists.
- Added configuration management for the UID scanner with support for multiple users and auto-scanning.
- Implemented logging and error handling throughout the UID scanning process.
- Created necessary build files for the `user_scanner` JNI integration.
- Added a `.gitignore` file to exclude build artifacts.

kernel/throne_comm.c

@@ -0,0 +1,125 @@
+#include <linux/fs.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/uaccess.h>
+#include <linux/workqueue.h>
+#include <linux/version.h>
+
+#include "klog.h"
+#include "throne_comm.h"
+
+#define PROC_UID_SCANNER "ksu_uid_scanner"
+
+static struct proc_dir_entry *proc_entry = NULL;
+static struct workqueue_struct *scanner_wq = NULL;
+static struct work_struct scan_work;
+
+// Signal userspace to rescan
+static bool need_rescan = false;
+
+static void rescan_work_fn(struct work_struct *work)
+{
+	// Signal userspace through proc interface
+	need_rescan = true;
+	pr_info("requested userspace uid rescan\n");
+}
+
+void ksu_request_userspace_scan(void)
+{
+	if (scanner_wq) {
+		queue_work(scanner_wq, &scan_work);
+	}
+}
+
+void ksu_handle_userspace_update(void)
+{
+	// Called when userspace notifies update complete
+	need_rescan = false;
+	pr_info("userspace uid list updated\n");
+}
+
+static int uid_scanner_show(struct seq_file *m, void *v)
+{
+	if (need_rescan) {
+		seq_puts(m, "RESCAN\n");
+	} else {
+		seq_puts(m, "OK\n");
+	}
+	return 0;
+}
+
+static int uid_scanner_open(struct inode *inode, struct file *file)
+{
+	return single_open(file, uid_scanner_show, NULL);
+}
+
+static ssize_t uid_scanner_write(struct file *file, const char __user *buffer, 
+                                 size_t count, loff_t *pos)
+{
+	char cmd[16];
+	
+	if (count >= sizeof(cmd))
+		return -EINVAL;
+		
+	if (copy_from_user(cmd, buffer, count))
+		return -EFAULT;
+		
+	cmd[count] = '\0';
+	
+	// Remove newline if present
+	if (count > 0 && cmd[count-1] == '\n')
+		cmd[count-1] = '\0';
+	
+	if (strcmp(cmd, "UPDATED") == 0) {
+		ksu_handle_userspace_update();
+		pr_info("received userspace update notification\n");
+	}
+	
+	return count;
+}
+
+static const struct proc_ops uid_scanner_proc_ops = {
+    .proc_open = uid_scanner_open,
+    .proc_read = seq_read,
+	.proc_write = uid_scanner_write,
+    .proc_lseek = seq_lseek,
+    .proc_release = single_release,
+};
+
+int ksu_throne_comm_init(void)
+{
+	// Create workqueue
+	scanner_wq = alloc_workqueue("ksu_scanner", WQ_UNBOUND, 1);
+	if (!scanner_wq) {
+		pr_err("failed to create scanner workqueue\n");
+		return -ENOMEM;
+	}
+	
+	INIT_WORK(&scan_work, rescan_work_fn);
+	
+	// Create proc entry
+	proc_entry = proc_create(PROC_UID_SCANNER, 0600, NULL, &uid_scanner_proc_ops);
+	if (!proc_entry) {
+		pr_err("failed to create proc entry\n");
+		destroy_workqueue(scanner_wq);
+		return -ENOMEM;
+	}
+	
+	pr_info("throne communication initialized\n");
+	return 0;
+}
+
+void ksu_throne_comm_exit(void)
+{
+	if (proc_entry) {
+		proc_remove(proc_entry);
+		proc_entry = NULL;
+	}
+	
+	if (scanner_wq) {
+		destroy_workqueue(scanner_wq);
+		scanner_wq = NULL;
+	}
+	
+	pr_info("throne communication cleaned up\n");
+}