path: root/fs/hostfs/hostfs_kern.c

/*
 * Copyright (C) 2000 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
 * Licensed under the GPL
 *
 * Ported the filesystem routines to 2.5.
 * 2003-02-10 Petr Baudis <pasky@ucw.cz>
 */

#include <linux/fs.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/statfs.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/mount.h>
#include <linux/namei.h>
#include "hostfs.h"
#include "init.h"
#include "kern.h"

struct hostfs_inode_info {
	int fd;
	fmode_t mode;
	struct inode vfs_inode;
};

static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
{
	return list_entry(inode, struct hostfs_inode_info, vfs_inode);
}

#define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_path.dentry->d_inode)

static int hostfs_d_delete(const struct dentry *dentry)
{
	return 1;
}

static const struct dentry_operations hostfs_dentry_ops = {
	.d_delete		= hostfs_d_delete,
};

/* Changed in hostfs_args before the kernel starts running */
static char *root_ino = "";
static int append = 0;

#define HOSTFS_SUPER_MAGIC 0x00c0ffee

static const struct inode_operations hostfs_iops;
static const struct inode_operations hostfs_dir_iops;
static const struct inode_operations hostfs_link_iops;

#ifndef MODULE
static int __init hostfs_args(char *options, int *add)
{
	char *ptr;

	ptr = strchr(options, ',');
	if (ptr != NULL)
		*ptr++ = '\0';
	if (*options != '\0')
		root_ino = options;

	options = ptr;
	while (options) {
		ptr = strchr(options, ',');
		if (ptr != NULL)
			*ptr++ = '\0';
		if (*options != '\0') {
			if (!strcmp(options, "append"))
				append = 1;
			else printf("hostfs_args - unsupported option - %s\n",
				    options);
		}
		options = ptr;
	}
	return 0;
}

__uml_setup("hostfs=", hostfs_args,
"hostfs=<root dir>,<flags>,...\n"
"    This is used to set hostfs parameters.  The root directory argument\n"
"    is used to confine all hostfs mounts to within the specified directory\n"
"    tree on the host.  If this isn't specified, then a user inside UML can\n"
"    mount anything on the host that's accessible to the user that's running\n"
"    it.\n"
"    The only flag currently supported is 'append', which specifies that all\n"
"    files opened by hostfs will be opened in append mode.\n\n"
);
#endif

static char *__dentry_name(struct dentry *dentry, char *name)
{
	char *p = dentry_path_raw(dentry, name, PATH_MAX);
	char *root;
	size_t len;

	root = dentry->d_sb->s_fs_info;
	len = strlen(root);
	if (IS_ERR(p)) {
		__putname(name);
		return NULL;
	}
	strlcpy(name, root, PATH_MAX);
	if (len > p - name) {
		__putname(name);
		return NULL;
	}
	if (p > name + len) {
		char *s = name + len;
		while ((*s++ = *p++) != '\0')
			;
	}
	return name;
}

static char *dentry_name(struct dentry *dentry)
{
	char *name = __getname();
	if (!name)
		return NULL;

	return __dentry_name(dentry, name); /* will unlock */
}

static char *inode_name(struct inode *ino)
{
	struct dentry *dentry;
	char *name;

	dentry = d_find_alias(ino);
	if (!dentry)
		return NULL;

	name = dentry_name(dentry);

	dput(dentry);

	return name;
}

static char *follow_link(char *link)
{
	int len, n;
	char *name, *resolved, *end;

	len = 64;
	while (1) {
		n = -ENOMEM;
		name = kmalloc(len, GFP_KERNEL);
		if (name == NULL)
			goto out;

		n = hostfs_do_readlink(link, name, len);