debugfs_compat.c

ocfs1.2.7 源码

#include <linux/module.h>
#include <linux/pagemap.h>
#include <linux/mount.h>
#include <linux/vfs.h>
#include <asm/uaccess.h>

#include "debugfs_compat.h"

/*
 * "nonseekable_open is so trivial, it's not worth putting in the kapi
 * compat stuff just for the one use in this file.
 * This code ripped from fs/open.c in the 2.6.14 kernel
 */

/* And of course, these FMODE_* may not be defined in older
 * kernels. */
#ifndef FMODE_LSEEK
#define FMODE_LSEEK	4
#endif
#ifndef FMODE_PREAD
#define FMODE_PREAD	8
#endif
#ifndef FMODE_PWRITE
#define FMODE_PWRITE	FMODE_PREAD	/* These go hand in hand */
#endif

/*
 * This is used by subsystems that don't want seekable
 * file descriptors
 */
static int compat_nonseekable_open(struct inode *inode, struct file *filp)
{
	filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE);
	return 0;
}

/* 
 * Ripped from fs/libfs.c in the 2.6.14 kernel.
 */

ssize_t compat_simple_read_from_buffer(void __user *to, size_t count,
				       loff_t *ppos, const void *from,
				       size_t available)
{
	loff_t pos = *ppos;
	if (pos < 0)
		return -EINVAL;
	if (pos >= available)
		return 0;
	if (count > available - pos)
		count = available - pos;
	if (copy_to_user(to, from + pos, count))
		return -EFAULT;
	*ppos = pos + count;
	return count;
}

/* Simple attribute files */

struct simple_attr {
	u64 (*get)(void *);
	void (*set)(void *, u64);
	char get_buf[24];	/* enough to store a u64 and "\n\0" */
	char set_buf[24];
	void *data;
	const char *fmt;	/* format for read operation */
	struct semaphore sem;	/* protects access to these buffers */
};

/* simple_attr_open is called by an actual attribute open file operation
 * to set the attribute specific access operations. */
int simple_attr_open(struct inode *inode, struct file *file,
		     u64 (*get)(void *), void (*set)(void *, u64),
		     const char *fmt)
{
	struct simple_attr *attr;

	attr = kmalloc(sizeof(*attr), GFP_KERNEL);
	if (!attr)
		return -ENOMEM;

	attr->get = get;
	attr->set = set;
	attr->data = inode->u.generic_ip;
	attr->fmt = fmt;
	init_MUTEX(&attr->sem);

	file->private_data = attr;

	return compat_nonseekable_open(inode, file);
}

int simple_attr_close(struct inode *inode, struct file *file)
{
	kfree(file->private_data);
	return 0;
}

/* read from the buffer that is filled with the get function */
ssize_t simple_attr_read(struct file *file, char __user *buf,
			 size_t len, loff_t *ppos)
{
	struct simple_attr *attr;
	size_t size;
	ssize_t ret;

	attr = file->private_data;

	if (!attr->get)
		return -EACCES;

	down(&attr->sem);
	if (*ppos) /* continued read */
		size = strlen(attr->get_buf);
	else	  /* first read */
		size = scnprintf(attr->get_buf, sizeof(attr->get_buf),
				 attr->fmt,
				 (unsigned long long)attr->get(attr->data));

	ret = compat_simple_read_from_buffer(buf, len, ppos, attr->get_buf, size);
	up(&attr->sem);
	return ret;
}

/* interpret the buffer as a number to call the set function with */
ssize_t simple_attr_write(struct file *file, const char __user *buf,
			  size_t len, loff_t *ppos)
{
	struct simple_attr *attr;
	u64 val;
	size_t size;
	ssize_t ret;

	attr = file->private_data;

	if (!attr->set)
		return -EACCES;

	down(&attr->sem);
	ret = -EFAULT;
	size = min(sizeof(attr->set_buf) - 1, len);
	if (copy_from_user(attr->set_buf, buf, size))
		goto out;

	ret = len; /* claim we got the whole input */
	attr->set_buf[size] = '\0';
	val = simple_strtol(attr->set_buf, NULL, 0);
	attr->set(attr->data, val);
out:
	up(&attr->sem);
	return ret;
}