3rd-party/linux-kernel-module-cheat
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fops read returns some data, busybox config frag for stat, bibliography start

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Ciro Santilli
2017-05-13 10:53:26 +01:00
parent 8616f6009b
commit bf3bb0cb18
6 changed files with 54 additions and 14 deletions
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28
kernel_module/fops.c
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@@ -5,6 +5,9 @@ Usage:
/fops.sh
No, there ain't no official docs:
http://stackoverflow.com/questions/15213932/what-are-the-struct-file-operations-arguments
fops define what the kernel will do on filesystem system calls on all of
/dev, /proc, /sys, and consistute the main method of userland communication
in drivers (syscalls being the other one).
@@ -13,9 +16,12 @@ Here we use debugfs.
*/
#include <linux/debugfs.h>
#include <linux/errno.h> /* EFAULT */
#include <linux/fs.h>
#include <linux/kernel.h>
#include <linux/kernel.h> /* min */
#include <linux/module.h>
#include <linux/printk.h> /* printk */
#include <asm/uaccess.h> /* copy_from_user, copy_to_user */
MODULE_LICENSE("GPL");
@@ -27,13 +33,26 @@ int fop_open(struct inode *inode, struct file *file)
return 0;
}
/**/
ssize_t fop_read(struct file *file, char __user *buf, size_t len, loff_t *off)
{
ssize_t ret;
char s[] = "abcd";
printk(KERN_INFO "read\n");
printk(KERN_INFO "len = %zu\n", len);
/* TODO. */
/*copy_to_user(arg, &msg, size);*/
return 0;
printk(KERN_INFO "off = %lld\n", (long long)*off);
if (sizeof(s) <= *off) {
ret = 0;
} else {
ret = min(len, sizeof(s) - (size_t)*off);
if (copy_to_user(buf, s, ret)) {
ret = -EFAULT;
} else {
*off += ret;
}
}
printk(KERN_INFO "ret = %lld\n", (long long)ret);
return ret;
}
ssize_t fop_write(struct file *file, const char __user *buf, size_t len, loff_t *off)
@@ -41,6 +60,7 @@ ssize_t fop_write(struct file *file, const char __user *buf, size_t len, loff_t
printk(KERN_INFO "write\n");
printk(KERN_INFO "buf = %.*s\n", (int)len, buf);
printk(KERN_INFO "len = %zu\n", len);
printk(KERN_INFO "off = %lld\n", (long long)*off);
return len;
}