mirror of
https://github.com/cirosantilli/linux-kernel-module-cheat.git
synced 2026-01-23 02:05:57 +01:00
104 lines
2.3 KiB
C
104 lines
2.3 KiB
C
/*
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dmesg stuff when fops happen.
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Usage:
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/fops.sh
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No, there ain't no official docs:
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http://stackoverflow.com/questions/15213932/what-are-the-struct-file-operations-arguments
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fops define what the kernel will do on filesystem system calls on all of
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/dev, /proc, /sys, and consistute the main method of userland communication
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in drivers (syscalls being the other one).
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Here we use debugfs.
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*/
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#include <linux/debugfs.h>
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#include <linux/errno.h> /* EFAULT */
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#include <linux/fs.h>
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#include <linux/kernel.h> /* min */
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#include <linux/module.h>
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#include <linux/printk.h> /* printk */
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#include <asm/uaccess.h> /* copy_from_user, copy_to_user */
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MODULE_LICENSE("GPL");
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static struct dentry *dir = 0;
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int fop_open(struct inode *inode, struct file *file)
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{
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printk(KERN_INFO "open\n");
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return 0;
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}
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/**/
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ssize_t fop_read(struct file *file, char __user *buf, size_t len, loff_t *off)
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{
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ssize_t ret;
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char s[] = "abcd";
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printk(KERN_INFO "read\n");
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printk(KERN_INFO "len = %zu\n", len);
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printk(KERN_INFO "off = %lld\n", (long long)*off);
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if (sizeof(s) <= *off) {
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ret = 0;
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} else {
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ret = min(len, sizeof(s) - (size_t)*off);
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if (copy_to_user(buf, s, ret)) {
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ret = -EFAULT;
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} else {
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*off += ret;
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}
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}
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printk(KERN_INFO "ret = %lld\n", (long long)ret);
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return ret;
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}
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ssize_t fop_write(struct file *file, const char __user *buf, size_t len, loff_t *off)
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{
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printk(KERN_INFO "write\n");
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printk(KERN_INFO "buf = %.*s\n", (int)len, buf);
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printk(KERN_INFO "len = %zu\n", len);
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printk(KERN_INFO "off = %lld\n", (long long)*off);
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return len;
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}
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/*
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Called on the last close:
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http://stackoverflow.com/questions/11393674/why-is-the-close-function-is-called-release-in-struct-file-operations-in-the-l
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*/
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int fop_release (struct inode *inode, struct file *file)
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{
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printk(KERN_INFO "release\n");
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return 0;
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}
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const struct file_operations fops = {
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.open = fop_open,
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.read = fop_read,
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.release = fop_release,
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.write = fop_write,
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};
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int init_module(void)
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{
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struct dentry *file;
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dir = debugfs_create_dir("kernel_module_cheat", 0);
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if (!dir) {
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printk(KERN_ALERT "debugfs_create_dir failed");
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return -1;
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}
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file = debugfs_create_file("fops", 0666, dir, NULL, &fops);
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if (!file) {
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printk(KERN_ALERT "debugfs_create_file failed");
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return -1;
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}
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return 0;
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}
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void cleanup_module(void)
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{
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debugfs_remove_recursive(dir);
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}
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