get rid of lkmc package, move userland and kernel-modules to top

Rationale: we already had a non buildroot build system, maintaining both will be hard, and having short paths is more awesome.
2026-01-23 02:05:57 +01:00 · 2018-10-25 00:00:01 +00:00
parent 98d2c83317
commit ca231b82f6
99 changed files with 184 additions and 181 deletions
--- a/kernel_modules/fops.c
+++ b/kernel_modules/fops.c
@@ -0,0 +1,138 @@
+/* https://github.com/cirosantilli/linux-kernel-module-cheat#file-operations */
+
+#include <linux/debugfs.h>
+#include <linux/errno.h> /* EFAULT */
+#include <linux/fs.h> /* file_operations */
+#include <linux/kernel.h> /* min */
+#include <linux/module.h>
+#include <linux/printk.h> /* printk */
+#include <linux/uaccess.h> /* copy_from_user, copy_to_user */
+#include <uapi/linux/stat.h> /* S_IRUSR */
+
+static struct dentry *debugfs_file;
+static char data[] = {'a', 'b', 'c', 'd'};
+
+static int open(struct inode *inode, struct file *filp)
+{
+	pr_info("open\n");
+	return 0;
+}
+
+/* @param[in,out] off: gives the initial position into the buffer.
+ *      We must increment this by the ammount of bytes read.
+ *      Then when userland reads the same file descriptor again,
+ *      we start from that point instead.
+ */
+static ssize_t read(struct file *filp, char __user *buf, size_t len, loff_t *off)
+{
+	ssize_t ret;
+
+	pr_info("read\n");
+	pr_info("len = %zu\n", len);
+	pr_info("off = %lld\n", (long long)*off);
+	if (sizeof(data) <= *off) {
+		ret = 0;
+	} else {
+		ret = min(len, sizeof(data) - (size_t)*off);
+		if (copy_to_user(buf, data + *off, ret)) {
+			ret = -EFAULT;
+		} else {
+			*off += ret;
+		}
+	}
+	pr_info("buf = %.*s\n", (int)len, buf);
+	pr_info("ret = %lld\n", (long long)ret);
+	return ret;
+}
+
+/* Similar to read, but with one notable difference:
+ * we must return ENOSPC if the user tries to write more
+ * than the size of our buffer. Otherwise, Bash > just
+ * keeps trying to write to it infinitely.
+ */
+static ssize_t write(struct file *filp, const char __user *buf, size_t len, loff_t *off)
+{
+	ssize_t ret;
+
+	pr_info("write\n");
+	pr_info("len = %zu\n", len);
+	pr_info("off = %lld\n", (long long)*off);
+	if (sizeof(data) <= *off) {
+		ret = 0;
+	} else {
+		if (sizeof(data) - (size_t)*off < len) {
+			ret = -ENOSPC;
+		} else {
+			if (copy_from_user(data + *off, buf, len)) {
+				ret = -EFAULT;
+			} else {
+				ret = len;
+				pr_info("buf = %.*s\n", (int)len, data + *off);
+				*off += ret;
+			}
+		}
+	}
+	pr_info("ret = %lld\n", (long long)ret);
+	return ret;
+}
+
+/* Called on the last close:
+ * http://stackoverflow.com/questions/11393674/why-is-the-close-function-is-called-release-in-struct-file-operations-in-the-l
+ */
+static int release(struct inode *inode, struct file *filp)
+{
+	pr_info("release\n");
+	return 0;
+}
+
+static loff_t llseek(struct file *filp, loff_t off, int whence)
+{
+	loff_t newpos;
+
+	pr_info("llseek\n");
+	pr_info("off = %lld\n", (long long)off);
+	pr_info("whence = %lld\n", (long long)whence);
+	switch(whence) {
+		case SEEK_SET:
+			newpos = off;
+			break;
+		case SEEK_CUR:
+			newpos = filp->f_pos + off;
+			break;
+		case SEEK_END:
+			newpos = sizeof(data) + off;
+			break;
+		default:
+			return -EINVAL;
+	}
+	if (newpos < 0) return -EINVAL;
+	filp->f_pos = newpos;
+	pr_info("newpos = %lld\n", (long long)newpos);
+	return newpos;
+}
+
+static const struct file_operations fops = {
+	/* Prevents rmmod while fops are running.
+	 * Try removing this for poll, which waits a lot. */
+	.owner = THIS_MODULE,
+	.llseek = llseek,
+	.open = open,
+	.read = read,
+	.release = release,
+	.write = write,
+};
+
+static int myinit(void)
+{
+	debugfs_file = debugfs_create_file("lkmc_fops", S_IRUSR | S_IWUSR, NULL, NULL, &fops);
+	return 0;
+}
+
+static void myexit(void)
+{
+	debugfs_remove_recursive(debugfs_file);
+}
+
+module_init(myinit)
+module_exit(myexit)
+MODULE_LICENSE("GPL");