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/*
* debug.c
*
* utilize debufs
* FIXME: R/W from /sys/kernel/debug/hello/magic doesn't work
*
*/
#include <linux/debugfs.h>
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/uaccess.h>
#include <debug.h>
#include <main.h>
#define BUFF_LEN 256
char kernel_buff[BUFF_LEN] = {'f','o','o','b','a','r','\0'};
/* debugfs_create_file's 4th param
* @data: a pointer to something that the caller will want to get to later
* on. The inode.i_private pointer will point to this value on
* the open() call.
*/
int fileprv = 1; /* hmm */
/* struct file, an abstract open file, not on disk, which would be a an inode */
static ssize_t hello_hello_debugfs_read(struct file *fp, char __user /* userspace */ *ubuff, size_t c, loff_t *pos)
{
/**
* simple_read_from_buffer - copy data from the buffer to user space
* @to: the user space buffer to read to
* @count: the maximum number of bytes to read
* @ppos: the current position in the buffer
* @from: the buffer to read from
* @available: the size of the buffer
*
* The simple_read_from_buffer() function reads up to @count bytes from the
* buffer @from at offset @ppos into the user space address starting at @to.
*
* On success, the number of bytes read is returned and the offset @ppos is
* advanced by this number, or negative value is returned on error.
**/
return simple_read_from_buffer(ubuff, c, pos, kernel_buff, BUFF_LEN);
}
static ssize_t hello_debugfs_write(struct file *fp, const char __user *ubuff, size_t c, loff_t *pos)
{
/**
* simple_write_to_buffer - copy data from user space to the buffer
* @to: the buffer to write to
* @available: the size of the buffer
* @ppos: the current position in the buffer
* @from: the user space buffer to read from
* @count: the maximum number of bytes to read
*
* The simple_write_to_buffer() function reads up to @count bytes from the user
* space address starting at @from into the buffer @to at offset @ppos.
*
* On success, the number of bytes written is returned and the offset @ppos is
* advanced by this number, or negative value is returned on error.
**/
if (c > BUFF_LEN)
return (-EINVAL);
return simple_write_to_buffer(kernel_buff, BUFF_LEN, pos, ubuff, c);
#if 0
printk(KERN_INFO "count %lu, offset %u", c, *pos);
copy_from_user(kernel_buff + *pos, ubuff, c);
return c;
#endif
}
int hello_debugfs_init(struct dentry **dir, struct dentry **file)
{
/* func ptrs that perform various operations on the device, in this case char device, well not even */
struct file_operations fops = {
.read = hello_hello_debugfs_read,
.write = hello_debugfs_write
};
/* omitted fields are initialized to NULL */
*dir = debugfs_create_dir("hello", NULL);
if (!*dir)
return (-ENODEV);
/* regular file, read by user/group/other, write by user */
*file = debugfs_create_file("magic", S_IFREG | S_IRUGO | S_IWUSR, *dir, &fileprv, &fops);
if (!*file)
printk(KERN_WARNING "[hello] debugfs: error creating file\n");
return 0;
}
int hello_debugfs_destroy(struct dentry *dir, struct dentry *file)
{
if (file)
debugfs_remove(file);
if (dir)
debugfs_remove(dir);
return 0;
}
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