Faulty first implementation of echo module

1 files changed, 162 insertions, 0 deletions

diff --git a/mod_add.c b/mod_add.c
new file mode 100644
index 0000000..cfabc50
--- /dev/null
+++ b/mod_add.c
@@ -0,0 +1,162 @@
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+MODULE_LICENSE("GPL");
+
+#include "assoc_buf.h"
+
+#define DEV_NAME "mod_add"
+#define OP_INVALID "Operation invalid\n"
+
+static int device_open(struct inode *, struct file *);
+static int device_release(struct inode *, struct file *);
+static ssize_t device_read(struct file *, char *, size_t, loff_t *);
+static ssize_t device_write(struct file *, const char *, size_t, loff_t *);
+
+static int major_num;
+static int device_open_count = 0;
+
+static struct buf_list {
+    struct asbuf *buf;
+    struct buf_list *next;
+} *buffers;
+
+struct asbuf *find_by_inode(unsigned long ino) {
+    struct buf_list *iter = buffers->next;
+    while (iter) {
+        if (iter->buf->ino == ino)
+            return iter->buf;
+        iter = iter->next;
+    }
+    return NULL;
+}
+
+ssize_t add_buf(struct asbuf *buf) {
+    struct buf_list *iter;
+
+    if (!buffers) {
+        buffers = kmalloc(sizeof(struct buf_list), GFP_KERNEL);
+        if (!buffers)
+            return -ENOMEM;
+        buffers->buf = buf;
+        buffers->next = NULL;
+        return 0;
+    }
+
+    iter = buffers;
+    while (iter->next)
+        iter = iter->next;
+
+    iter->next = kmalloc(sizeof(struct buf_list), GFP_KERNEL);
+    if (!iter->next)
+        return -ENOMEM;
+    iter->buf = buf;
+    iter->next = NULL;
+    return 0;
+}
+
+void free_buf_list(void) {
+    struct buf_list *iter = buffers, *next;
+
+    while (iter) {
+        next = iter->next;
+        asbuf_free(iter->buf);
+        kfree(iter->buf);
+        kfree(iter);
+        iter = next;
+    }
+}
+
+ssize_t rm_by_inode(unsigned long ino) {
+    struct buf_list *iter = buffers;
+    struct buf_list *save_prev;
+
+    if (!buffers)
+        return 0;
+
+    while (iter->next) {
+        save_prev = iter;
+        iter = iter->next;
+        if (iter->buf->ino == ino) {
+            save_prev->next = iter->next;
+            asbuf_free(iter->buf);
+            kfree(iter->buf);
+            kfree(iter);
+            return 0;
+        }
+    }
+    return -EINVAL;
+}
+
+static struct file_operations file_ops = {
+    .read = device_read,
+    .write = device_write,
+    .open = device_open,
+    .release = device_release
+};
+
+
+static ssize_t device_read(struct file *flip, char *buffer, size_t len, loff_t *offset) {
+    struct asbuf *buf = find_by_inode(flip->f_inode->i_ino);
+    printk(KERN_INFO "req inode %lu\n", flip->f_inode->i_ino);
+    if (!buf)
+        return -EINVAL;
+    return asbuf_to_user(buf, buffer, len, offset);
+}
+
+static ssize_t device_write(struct file *flip, const char *buffer, size_t len, loff_t *offset) {
+    if (len == 0)
+        return 0;
+
+    return asbuf_from_user(find_by_inode(flip->f_inode->i_ino), buffer, len, offset);
+}
+
+static int device_open(struct inode *inode, struct file *file) {
+    struct asbuf *newbuf;
+
+    if (device_open_count)
+        return -EBUSY;
+
+    newbuf = kzalloc(sizeof(*newbuf), GFP_KERNEL);
+    if (!newbuf)
+        return -ENOMEM;
+
+    printk(KERN_INFO "opened for inode %lu", inode->i_ino);
+    newbuf->ino = inode->i_ino;
+    add_buf (newbuf);
+    device_open_count++;
+    try_module_get(THIS_MODULE);
+    return 0;
+}
+
+static int device_release(struct inode *inode, struct file *file) {
+    rm_by_inode(inode->i_ino);
+    device_open_count--;
+    module_put(THIS_MODULE);
+    return 0;
+}
+
+static int __init mod_add_init(void) {
+    buffers = kzalloc(sizeof(*buffers), GFP_KERNEL);
+
+    major_num = register_chrdev(0, DEV_NAME, &file_ops);
+    if (major_num < 0) {
+        printk(KERN_ALERT "Could not register device: %d\n", major_num);
+        return major_num;
+    } else {
+        printk(KERN_INFO "mod_add loaded. dev maj = %d\n", major_num);
+        return 0;
+    }
+}
+static void __exit mod_add_exit(void) {
+    unregister_chrdev(major_num, DEV_NAME);
+    free_buf_list();
+    printk(KERN_INFO "okay, bye\n");
+}
+
+module_init(mod_add_init);
+module_exit(mod_add_exit);