/*
 *  linux/fs/open.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

#include <linux/string.h>
#include <linux/mm.h>
#include <linux/utime.h>
#include <linux/file.h>
#include <linux/smp_lock.h>
#include <linux/quotaops.h>
#include <linux/dnotify.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/iobuf.h>
#include <linux/namei.h>
#include <linux/backing-dev.h>
#include <linux/security.h>

#include <asm/uaccess.h>

#define special_file(m) (S_ISCHR(m)||S_ISBLK(m)||S_ISFIFO(m)||S_ISSOCK(m))

int vfs_statfs(struct super_block *sb, struct statfs *buf)
{
        int retval = -ENODEV;

        if (sb) {
                retval = -ENOSYS;
                if (sb->s_op && sb->s_op->statfs) {
                        memset(buf, 0, sizeof(struct statfs));
                        retval = security_ops->sb_statfs(sb);
                        if (retval)
                                return retval;
                        retval = sb->s_op->statfs(sb, buf);
                }
        }
        return retval;
}


asmlinkage long sys_statfs(const char * path, struct statfs * buf)
{
        struct nameidata nd;
        int error;

        error = user_path_walk(path, &nd);
        if (!error) {
                struct statfs tmp;
                error = vfs_statfs(nd.dentry->d_inode->i_sb, &tmp);
                if (!error && copy_to_user(buf, &tmp, sizeof(struct statfs)))
                        error = -EFAULT;
                path_release(&nd);
        }
        return error;
}

asmlinkage long sys_fstatfs(unsigned int fd, struct statfs * buf)
{
        struct file * file;
        struct statfs tmp;
        int error;

        error = -EBADF;
        file = fget(fd);
        if (!file)
                goto out;
        error = vfs_statfs(file->f_dentry->d_inode->i_sb, &tmp);
        if (!error && copy_to_user(buf, &tmp, sizeof(struct statfs)))
                error = -EFAULT;
        fput(file);
out:
        return error;
}

int do_truncate(struct dentry *dentry, loff_t length)
{
        int err;
        struct iattr newattrs;

        /* Not pretty: "inode->i_size" shouldn't really be signed. But it is. */
        if (length < 0)
                return -EINVAL;

        newattrs.ia_size = length;
        newattrs.ia_valid = ATTR_SIZE | ATTR_CTIME;
        down(&dentry->d_inode->i_sem);
        err = notify_change(dentry, &newattrs);
        up(&dentry->d_inode->i_sem);
        return err;
}

static inline long do_sys_truncate(const char * path, loff_t length)
{
        struct nameidata nd;
        struct inode * inode;
        int error;

        error = -EINVAL;
        if (length < 0) /* sorry, but loff_t says... */
                goto out;

        error = user_path_walk(path, &nd);
        if (error)
                goto out;
        inode = nd.dentry->d_inode;

        /* For directories it's -EISDIR, for other non-regulars - -EINVAL */
        error = -EISDIR;
        if (S_ISDIR(inode->i_mode))
                goto dput_and_out;

        error = -EINVAL;
        if (!S_ISREG(inode->i_mode))
                goto dput_and_out;

        error = permission(inode,MAY_WRITE);
        if (error)
                goto dput_and_out;

        error = -EROFS;
        if (IS_RDONLY(inode))
                goto dput_and_out;

        error = -EPERM;
        if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
                goto dput_and_out;

        /*
         * Make sure that there are no leases.
         */
        error = get_lease(inode, FMODE_WRITE);
        if (error)
                goto dput_and_out;

        error = get_write_access(inode);
        if (error)
                goto dput_and_out;

        error = locks_verify_truncate(inode, NULL, length);
        if (!error) {
                DQUOT_INIT(inode);
                error = do_truncate(nd.dentry, length);
        }
        put_write_access(inode);

dput_and_out:
        path_release(&nd);
out:
        return error;
}

asmlinkage long sys_truncate(const char * path, unsigned long length)
{
        /* on 32-bit boxen it will cut the range 2^31--2^32-1 off */
        return do_sys_truncate(path, (long)length);
}

static inline long do_sys_ftruncate(unsigned int fd, loff_t length, int small)
{
        struct inode * inode;
        struct dentry *dentry;
        struct file * file;
        int error;

        error = -EINVAL;
        if (length < 0)
                goto out;
        error = -EBADF;
        file = fget(fd);
        if (!file)
                goto out;

        /* explicitly opened as large or we are on 64-bit box */
        if (file->f_flags & O_LARGEFILE)
                small = 0;

        dentry = file->f_dentry;
        inode = dentry->d_inode;
        error = -EINVAL;
        if (!S_ISREG(inode->i_mode) || !(file->f_mode & FMODE_WRITE))
                goto out_putf;

        error = -EINVAL;
        /* Cannot ftruncate over 2^31 bytes without large file support */
        if (small && length > MAX_NON_LFS)
                goto out_putf;

        error = -EPERM;
        if (IS_APPEND(inode))
                goto out_putf;

        error = locks_verify_truncate(inode, file, length);
        if (!error)
                error = do_truncate(dentry, length);
out_putf:
        fput(file);
out:
        return error;
}

asmlinkage long sys_ftruncate(unsigned int fd, unsigned long length)
{
        return do_sys_ftruncate(fd, length, 1);
}

/* LFS versions of truncate are only needed on 32 bit machines */
#if BITS_PER_LONG == 32
asmlinkage long sys_truncate64(const char * path, loff_t length)
{
        return do_sys_truncate(path, length);
}

asmlinkage long sys_ftruncate64(unsigned int fd, loff_t length)
{
        return do_sys_ftruncate(fd, length, 0);
}
#endif

#if !(defined(__alpha__) || defined(__ia64__))

/*
 * sys_utime() can be implemented in user-level using sys_utimes().
 * Is this for backwards compatibility?  If so, why not move it
 * into the appropriate arch directory (for those architectures that
 * need it).
 */

/* If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
asmlinkage long sys_utime(char * filename, struct utimbuf * times)
{
        int error;
        struct nameidata nd;
        struct inode * inode;
        struct iattr newattrs;

        error = user_path_walk(filename, &nd);
        if (error)
                goto out;
        inode = nd.dentry->d_inode;

        error = -EROFS;
        if (IS_RDONLY(inode))
                goto dput_and_out;

        /* Don't worry, the checks are done in inode_change_ok() */
        newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
        if (times) {
                error = get_user(newattrs.ia_atime, &times->actime);
                if (!error) 
                        error = get_user(newattrs.ia_mtime, &times->modtime);
                if (error)
                        goto dput_and_out;

                newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
        } else {
                if (current->fsuid != inode->i_uid &&
                    (error = permission(inode,MAY_WRITE)) != 0)
                        goto dput_and_out;
        }
        down(&inode->i_sem);
        error = notify_change(nd.dentry, &newattrs);
        up(&inode->i_sem);
dput_and_out:
        path_release(&nd);
out:
        return error;
}

#endif

/* If times==NULL, set access and modification to current time,
 * must be owner or have write permission.
 * Else, update from *times, must be owner or super user.
 */
asmlinkage long sys_utimes(char * filename, struct timeval * utimes)
{
        int error;
        struct nameidata nd;
        struct inode * inode;
        struct iattr newattrs;

        error = user_path_walk(filename, &nd);

        if (error)
                goto out;
        inode = nd.dentry->d_inode;

        error = -EROFS;
        if (IS_RDONLY(inode))
                goto dput_and_out;

        /* Don't worry, the checks are done in inode_change_ok() */
        newattrs.ia_valid = ATTR_CTIME | ATTR_MTIME | ATTR_ATIME;
        if (utimes) {
                struct timeval times[2];
                error = -EFAULT;
                if (copy_from_user(&times, utimes, sizeof(times)))
                        goto dput_and_out;
                newattrs.ia_atime = times[0].tv_sec;
                newattrs.ia_mtime = times[1].tv_sec;
                newattrs.ia_valid |= ATTR_ATIME_SET | ATTR_MTIME_SET;
        } else {
                if (current->fsuid != inode->i_uid &&
                    (error = permission(inode,MAY_WRITE)) != 0)
                        goto dput_and_out;
        }
        down(&inode->i_sem);
        error = notify_change(nd.dentry, &newattrs);
        up(&inode->i_sem);
dput_and_out:
        path_release(&nd);
out:
        return error;
}

/*
 * access() needs to use the real uid/gid, not the effective uid/gid.
 * We do this by temporarily clearing all FS-related capabilities and
 * switching the fsuid/fsgid around to the real ones.
 */
asmlinkage long sys_access(const char * filename, int mode)
{
        struct nameidata nd;
        int old_fsuid, old_fsgid;
        kernel_cap_t old_cap;
        int res;

        if (mode & ~S_IRWXO)    /* where's F_OK, X_OK, W_OK, R_OK? */
                return -EINVAL;

        old_fsuid = current->fsuid;
        old_fsgid = current->fsgid;
        old_cap = current->cap_effective;

        current->fsuid = current->uid;
        current->fsgid = current->gid;

        /*
         * Clear the capabilities if we switch to a non-root user
         *
         * FIXME: There is a race here against sys_capset.  The
         * capabilities can change yet we will restore the old
         * value below.  We should hold task_capabilities_lock,
         * but we cannot because user_path_walk can sleep.
         */
        if (current->uid)
                cap_clear(current->cap_effective);
        else
                current->cap_effective = current->cap_permitted;

        res = user_path_walk(filename, &nd);
        if (!res) {
                res = permission(nd.dentry->d_inode, mode);
                /* SuS v2 requires we report a read only fs too */
                if(!res && (mode & S_IWOTH) && IS_RDONLY(nd.dentry->d_inode)
                   && !special_file(nd.dentry->d_inode->i_mode))
                        res = -EROFS;
                path_release(&nd);
        }

        current->fsuid = old_fsuid;
        current->fsgid = old_fsgid;
        current->cap_effective = old_cap;

        return res;
}

asmlinkage long sys_chdir(const char * filename)
{
        struct nameidata nd;
        int error;

        error = __user_walk(filename, LOOKUP_FOLLOW|LOOKUP_DIRECTORY, &nd);
        if (error)
                goto out;

        error = permission(nd.dentry->d_inode,MAY_EXEC);
        if (error)
                goto dput_and_out;

        set_fs_pwd(current->fs, nd.mnt, nd.dentry);

dput_and_out:
        path_release(&nd);
out:
        return error;
}

asmlinkage long sys_fchdir(unsigned int fd)
{
        struct file *file;
        struct dentry *dentry;
        struct inode *inode;
        struct vfsmount *mnt;
        int error;

        error = -EBADF;
        file = fget(fd);
        if (!file)
                goto out;

        dentry = file->f_dentry;
        mnt = file->f_vfsmnt;
        inode = dentry->d_inode;

        error = -ENOTDIR;
        if (!S_ISDIR(inode->i_mode))
                goto out_putf;

        error = permission(inode, MAY_EXEC);
        if (!error)
                set_fs_pwd(current->fs, mnt, dentry);
out_putf:
        fput(file);
out:
        return error;
}

asmlinkage long sys_chroot(const char * filename)
{
        struct nameidata nd;
        int error;

        error = __user_walk(filename, LOOKUP_FOLLOW | LOOKUP_DIRECTORY | LOOKUP_NOALT, &nd);
        if (error)
                goto out;

        error = permission(nd.dentry->d_inode,MAY_EXEC);
        if (error)
                goto dput_and_out;

        error = -EPERM;
        if (!capable(CAP_SYS_CHROOT))
                goto dput_and_out;

        set_fs_root(current->fs, nd.mnt, nd.dentry);
        set_fs_altroot();
        error = 0;
dput_and_out:
        path_release(&nd);
out:
        return error;
}

asmlinkage long sys_fchmod(unsigned int fd, mode_t mode)
{
        struct inode * inode;
        struct dentry * dentry;
        struct file * file;
        int err = -EBADF;
        struct iattr newattrs;

        file = fget(fd);
        if (!file)
                goto out;

        dentry = file->f_dentry;
        inode = dentry->d_inode;

        err = -EROFS;
        if (IS_RDONLY(inode))
                goto out_putf;
        err = -EPERM;
        if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
                goto out_putf;
        down(&inode->i_sem);
        if (mode == (mode_t) -1)
                mode = inode->i_mode;
        newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
        newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
        err = notify_change(dentry, &newattrs);
        up(&inode->i_sem);

out_putf:
        fput(file);
out:
        return err;
}

asmlinkage long sys_chmod(const char * filename, mode_t mode)
{
        struct nameidata nd;
        struct inode * inode;
        int error;
        struct iattr newattrs;

        error = user_path_walk(filename, &nd);
        if (error)
                goto out;
        inode = nd.dentry->d_inode;

        error = -EROFS;
        if (IS_RDONLY(inode))
                goto dput_and_out;

        error = -EPERM;
        if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
                goto dput_and_out;

        down(&inode->i_sem);
        if (mode == (mode_t) -1)
                mode = inode->i_mode;
        newattrs.ia_mode = (mode & S_IALLUGO) | (inode->i_mode & ~S_IALLUGO);
        newattrs.ia_valid = ATTR_MODE | ATTR_CTIME;
        error = notify_change(nd.dentry, &newattrs);
        up(&inode->i_sem);

dput_and_out:
        path_release(&nd);
out:
        return error;
}

static int chown_common(struct dentry * dentry, uid_t user, gid_t group)
{
        struct inode * inode;
        int error;
        struct iattr newattrs;

        error = -ENOENT;
        if (!(inode = dentry->d_inode)) {
                printk(KERN_ERR "chown_common: NULL inode\n");
                goto out;
        }
        error = -EROFS;
        if (IS_RDONLY(inode))
                goto out;
        error = -EPERM;
        if (IS_IMMUTABLE(inode) || IS_APPEND(inode))
                goto out;
        newattrs.ia_valid =  ATTR_CTIME;
        if (user != (uid_t) -1) {
                newattrs.ia_valid |= ATTR_UID;
                newattrs.ia_uid = user;
        }
        if (group != (gid_t) -1) {
                newattrs.ia_valid |= ATTR_GID;
                newattrs.ia_gid = group;
        }
        if (!S_ISDIR(inode->i_mode))
                newattrs.ia_valid |= ATTR_KILL_SUID|ATTR_KILL_SGID;
        down(&inode->i_sem);
        error = notify_change(dentry, &newattrs);
        up(&inode->i_sem);
out:
        return error;
}

asmlinkage long sys_chown(const char * filename, uid_t user, gid_t group)
{
        struct nameidata nd;
        int error;

        error = user_path_walk(filename, &nd);
        if (!error) {
                error = chown_common(nd.dentry, user, group);
                path_release(&nd);
        }
        return error;
}

asmlinkage long sys_lchown(const char * filename, uid_t user, gid_t group)
{
        struct nameidata nd;
        int error;

        error = user_path_walk_link(filename, &nd);
        if (!error) {
                error = chown_common(nd.dentry, user, group);
                path_release(&nd);
        }
        return error;
}


asmlinkage long sys_fchown(unsigned int fd, uid_t user, gid_t group)
{
        struct file * file;
        int error = -EBADF;

        file = fget(fd);
        if (file) {
                error = chown_common(file->f_dentry, user, group);
                fput(file);
        }
        return error;
}

/*
 * Note that while the flag value (low two bits) for sys_open means:
 *      00 - read-only
 *      01 - write-only
 *      10 - read-write
 *      11 - special
 * it is changed into
 *      00 - no permissions needed
 *      01 - read-permission
 *      10 - write-permission
 *      11 - read-write
 * for the internal routines (ie open_namei()/follow_link() etc). 00 is
 * used by symlinks.
 */
struct file *filp_open(const char * filename, int flags, int mode)
{
        int namei_flags, error;
        struct nameidata nd;

        namei_flags = flags;
        if ((namei_flags+1) & O_ACCMODE)
                namei_flags++;
        if (namei_flags & O_TRUNC)
                namei_flags |= 2;

        error = open_namei(filename, namei_flags, mode, &nd);
        if (!error)
                return dentry_open(nd.dentry, nd.mnt, flags);

        return ERR_PTR(error);
}

struct file *dentry_open(struct dentry *dentry, struct vfsmount *mnt, int flags)
{
        struct file * f;
        struct inode *inode;
        static LIST_HEAD(kill_list);
        int error;

        error = -ENFILE;
        f = get_empty_filp();
        if (!f)
                goto cleanup_dentry;
        f->f_flags = flags;
        f->f_mode = (flags+1) & O_ACCMODE;
        inode = dentry->d_inode;
        if (f->f_mode & FMODE_WRITE) {
                error = get_write_access(inode);
                if (error)
                        goto cleanup_file;
        }

        f->f_ra.ra_pages = inode->i_mapping->backing_dev_info->ra_pages;
        f->f_dentry = dentry;
        f->f_vfsmnt = mnt;
        f->f_pos = 0;
        f->f_op = fops_get(inode->i_fop);
        file_move(f, &inode->i_sb->s_files);

        if (f->f_op && f->f_op->open) {
                error = f->f_op->open(inode,f);
                if (error)
                        goto cleanup_all;
        }
        f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);

        /* NB: we're sure to have correct a_ops only after f_op->open */
        if (f->f_flags & O_DIRECT) {
                if (!inode->i_mapping || !inode->i_mapping->a_ops ||
                        !inode->i_mapping->a_ops->direct_IO) {
                                error = -EINVAL;
                                goto cleanup_all;
                }
        }

        return f;

cleanup_all:
        fops_put(f->f_op);
        if (f->f_mode & FMODE_WRITE)
                put_write_access(inode);
        file_move(f, &kill_list); /* out of the way.. */
        f->f_dentry = NULL;
        f->f_vfsmnt = NULL;
cleanup_file:
        put_filp(f);
cleanup_dentry:
        dput(dentry);
        mntput(mnt);
        return ERR_PTR(error);
}

/*
 * Find an empty file descriptor entry, and mark it busy.
 */
int get_unused_fd(void)
{
        struct files_struct * files = current->files;
        int fd, error;

        error = -EMFILE;
        write_lock(&files->file_lock);

repeat:
        fd = find_next_zero_bit(files->open_fds->fds_bits, 
                                files->max_fdset, 
                                files->next_fd);

        /*
         * N.B. For clone tasks sharing a files structure, this test
         * will limit the total number of files that can be opened.
         */
        if (fd >= current->rlim[RLIMIT_NOFILE].rlim_cur)
                goto out;

        /* Do we need to expand the fdset array? */
        if (fd >= files->max_fdset) {
                error = expand_fdset(files, fd);
                if (!error) {
                        error = -EMFILE;
                        goto repeat;
                }
                goto out;
        }
        
        /* 
         * Check whether we need to expand the fd array.
         */
        if (fd >= files->max_fds) {
                error = expand_fd_array(files, fd);
                if (!error) {
                        error = -EMFILE;
                        goto repeat;
                }
                goto out;
        }

        FD_SET(fd, files->open_fds);
        FD_CLR(fd, files->close_on_exec);
        files->next_fd = fd + 1;
#if 1
        /* Sanity check */
        if (files->fd[fd] != NULL) {
                printk(KERN_WARNING "get_unused_fd: slot %d not NULL!\n", fd);
                files->fd[fd] = NULL;
        }
#endif
        error = fd;

out:
        write_unlock(&files->file_lock);
        return error;
}

static inline void __put_unused_fd(struct files_struct *files, unsigned int fd)
{
        __FD_CLR(fd, files->open_fds);
        if (fd < files->next_fd)
                files->next_fd = fd;
}

void put_unused_fd(unsigned int fd)
{
        struct files_struct *files = current->files;
        write_lock(&files->file_lock);
        __put_unused_fd(files, fd);
        write_unlock(&files->file_lock);
}

/*
 * Install a file pointer in the fd array.  
 *
 * The VFS is full of places where we drop the files lock between
 * setting the open_fds bitmap and installing the file in the file
 * array.  At any such point, we are vulnerable to a dup2() race
 * installing a file in the array before us.  We need to detect this and
 * fput() the struct file we are about to overwrite in this case.
 *
 * It should never happen - if we allow dup2() do it, _really_ bad things
 * will follow.
 */

void fd_install(unsigned int fd, struct file * file)
{
        struct files_struct *files = current->files;
        write_lock(&files->file_lock);
        if (unlikely(files->fd[fd] != NULL))
                BUG();
        files->fd[fd] = file;
        write_unlock(&files->file_lock);
}

asmlinkage long sys_open(const char * filename, int flags, int mode)
{
        char * tmp;
        int fd, error;

#if BITS_PER_LONG != 32
        flags |= O_LARGEFILE;
#endif
        tmp = getname(filename);
        fd = PTR_ERR(tmp);
        if (!IS_ERR(tmp)) {
                fd = get_unused_fd();
                if (fd >= 0) {
                        struct file *f = filp_open(tmp, flags, mode);
                        error = PTR_ERR(f);
                        if (IS_ERR(f))
                                goto out_error;
                        fd_install(fd, f);
                }
out:
                putname(tmp);
        }
        return fd;

out_error:
        put_unused_fd(fd);
        fd = error;
        goto out;
}

#ifndef __alpha__

/*
 * For backward compatibility?  Maybe this should be moved
 * into arch/i386 instead?
 */
asmlinkage long sys_creat(const char * pathname, int mode)
{
        return sys_open(pathname, O_CREAT | O_WRONLY | O_TRUNC, mode);
}

#endif

/*
 * "id" is the POSIX thread ID. We use the
 * files pointer for this..
 */
int filp_close(struct file *filp, fl_owner_t id)
{
        int retval;

        if (!file_count(filp)) {
                printk(KERN_ERR "VFS: Close: file count is 0\n");
                return 0;
        }
        retval = 0;
        if (filp->f_op && filp->f_op->flush) {
                lock_kernel();
                retval = filp->f_op->flush(filp);
                unlock_kernel();
        }
        dnotify_flush(filp, id);
        locks_remove_posix(filp, id);
        fput(filp);
        return retval;
}

/*
 * Careful here! We test whether the file pointer is NULL before
 * releasing the fd. This ensures that one clone task can't release
 * an fd while another clone is opening it.
 */
asmlinkage long sys_close(unsigned int fd)
{
        struct file * filp;
        struct files_struct *files = current->files;

        write_lock(&files->file_lock);
        if (fd >= files->max_fds)
                goto out_unlock;
        filp = files->fd[fd];
        if (!filp)
                goto out_unlock;
        files->fd[fd] = NULL;
        FD_CLR(fd, files->close_on_exec);
        __put_unused_fd(files, fd);
        write_unlock(&files->file_lock);
        return filp_close(filp, files);

out_unlock:
        write_unlock(&files->file_lock);
        return -EBADF;
}

/*
 * This routine simulates a hangup on the tty, to arrange that users
 * are given clean terminals at login time.
 */
asmlinkage long sys_vhangup(void)
{
        if (capable(CAP_SYS_TTY_CONFIG)) {
                tty_vhangup(current->tty);
                return 0;
        }
        return -EPERM;
}

/*
 * Called when an inode is about to be open.
 * We use this to disallow opening RW large files on 32bit systems if
 * the caller didn't specify O_LARGEFILE.  On 64bit systems we force
 * on this flag in sys_open.
 */
int generic_file_open(struct inode * inode, struct file * filp)
{
        if (!(filp->f_flags & O_LARGEFILE) && inode->i_size > MAX_NON_LFS)
                return -EFBIG;
        return 0;
}

EXPORT_SYMBOL(generic_file_open);