Use nice file permission constants, fix readme paths

kernel_module/anonymous_inode.c

@@ -4,7 +4,7 @@ https://stackoverflow.com/questions/4508998/what-is-anonymous-inode
 anon_inode_getfd example:
 
 - get an anonymous inode via ioctl from a debugfs entry
-- read from that inode
+- read jiffies from that inode
 
 This method allows getting multiple file descriptors from a single filesystem,
 which reduces namespace pollution.

kernel_module/debugfs.c

@@ -11,6 +11,7 @@ Requires `CONFIG_DEBUG_FS=y`.
 #include <linux/debugfs.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
+#include <uapi/linux/stat.h> /* S_IRUSR */
 
 MODULE_LICENSE("GPL");
 
@@ -25,7 +26,7 @@ static int myinit(void)
 		printk(KERN_ALERT "debugfs_create_dir failed");
 		return -1;
 	}
-	file = debugfs_create_u32("myfile", 0666, dir, &value);
+	file = debugfs_create_u32("myfile", S_IRUSR, dir, &value);
 	if (!file) {
 		printk(KERN_ALERT "debugfs_create_u32 failed");
 		return -1;

kernel_module/fops.c

@@ -24,6 +24,7 @@ Here we use debugfs.
 #include <linux/kernel.h> /* min */
 #include <linux/module.h>
 #include <linux/printk.h> /* printk */
+#include <uapi/linux/stat.h> /* S_IRUSR */
 
 MODULE_LICENSE("GPL");
 
@@ -138,7 +139,7 @@ static const struct file_operations fops = {
 static int myinit(void)
 {
 	dir = debugfs_create_dir("lkmc_fops", 0);
-	debugfs_create_file("f", 0666, dir, NULL, &fops);
+	debugfs_create_file("f", S_IRUSR | S_IWUSR, dir, NULL, &fops);
 	return 0;
 }
 

kernel_module/poll.c

@@ -16,6 +16,7 @@ Outcome: user echoes jiffies every second.
 #include <linux/poll.h>
 #include <linux/printk.h> /* printk */
 #include <linux/wait.h> /* wait_queue_head_t, wait_event_interruptible, wake_up_interruptible  */
+#include <uapi/linux/stat.h> /* S_IRUSR */
 
 MODULE_LICENSE("GPL");
 
@@ -71,7 +72,7 @@ static const struct file_operations fops = {
 static int myinit(void)
 {
 	dir = debugfs_create_dir("lkmc_poll", 0);
-	debugfs_create_file("f", 0666, dir, NULL, &fops);
+	debugfs_create_file("f", S_IRUSR | S_IWUSR, dir, NULL, &fops);
 	init_waitqueue_head(&waitqueue);
 	kthread = kthread_create(kthread_func, NULL, "mykthread");
 	wake_up_process(kthread);