/*
 *  linux/fs/read_write.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *  Minor pieces Copyright (C) 2002 Red Hat Inc, All Rights Reserved
 *
 *  This program is free software; you can redistribute it and/or modify
 *  it under the terms of the GNU General Public License as published by
 *  the Free Software Foundation; either version 2 of the License, or
 *  (at your option) any later version.
 *
 *  This program is distributed in the hope that it will be useful,
 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *  GNU General Public License for more details.
 *
 *  You should have received a copy of the GNU General Public License
 *  along with this program; if not, write to the Free Software
 *  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

#include <linux/slab.h> 
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/smp_lock.h>
#include <linux/dnotify.h>

#include <asm/uaccess.h>

struct file_operations generic_ro_fops = {
        llseek:         generic_file_llseek,
        read:           generic_file_read,
        mmap:           generic_file_mmap,
};

ssize_t generic_read_dir(struct file *filp, char *buf, size_t siz, loff_t *ppos)
{
        return -EISDIR;
}

loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
{
        long long retval;

        switch (origin) {
                case 2:
                        offset += file->f_dentry->d_inode->i_size;
                        break;
                case 1:
                        offset += file->f_pos;
        }
        retval = -EINVAL;
        if (offset>=0 && offset<=file->f_dentry->d_inode->i_sb->s_maxbytes) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_reada = 0;
                        file->f_version = ++event;
                }
                retval = offset;
        }
        return retval;
}

loff_t no_llseek(struct file *file, loff_t offset, int origin)
{
        return -ESPIPE;
}

loff_t default_llseek(struct file *file, loff_t offset, int origin)
{
        long long retval;

        switch (origin) {
                case 2:
                        offset += file->f_dentry->d_inode->i_size;
                        break;
                case 1:
                        offset += file->f_pos;
        }
        retval = -EINVAL;
        if (offset >= 0) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_reada = 0;
                        file->f_version = ++event;
                }
                retval = offset;
        }
        return retval;
}

static inline loff_t llseek(struct file *file, loff_t offset, int origin)
{
        loff_t (*fn)(struct file *, loff_t, int);
        loff_t retval;

        fn = default_llseek;
        if (file->f_op && file->f_op->llseek)
                fn = file->f_op->llseek;
        lock_kernel();
        retval = fn(file, offset, origin);
        unlock_kernel();
        return retval;
}

asmlinkage off_t sys_lseek(unsigned int fd, off_t offset, unsigned int origin)
{
        off_t retval;
        struct file * file;

        retval = -EBADF;
        file = fget(fd);
        if (!file)
                goto bad;
        retval = -EINVAL;
        if (origin <= 2) {
                loff_t res = llseek(file, offset, origin);
                retval = res;
                if (res != (loff_t)retval)
                        retval = -EOVERFLOW;    /* LFS: should only happen on 32 bit platforms */
        }
        fput(file);
bad:
        return retval;
}

#if !defined(__alpha__)
asmlinkage long sys_llseek(unsigned int fd, unsigned long offset_high,
                           unsigned long offset_low, loff_t * result,
                           unsigned int origin)
{
        int retval;
        struct file * file;
        loff_t offset;

        retval = -EBADF;
        file = fget(fd);
        if (!file)
                goto bad;
        retval = -EINVAL;
        if (origin > 2)
                goto out_putf;

        offset = llseek(file, ((loff_t) offset_high << 32) | offset_low,
                        origin);

        retval = (int)offset;
        if (offset >= 0) {
                retval = -EFAULT;
                if (!copy_to_user(result, &offset, sizeof(offset)))
                        retval = 0;
        }
out_putf:
        fput(file);
bad:
        return retval;
}
#endif

asmlinkage ssize_t sys_read(unsigned int fd, char * buf, size_t count)
{
        ssize_t ret;
        struct file * file;

        ret = -EBADF;
        file = fget(fd);
        if (file) {
                if (file->f_mode & FMODE_READ) {
                        ret = locks_verify_area(FLOCK_VERIFY_READ, file->f_dentry->d_inode,
                                                file, file->f_pos, count);
                        if (!ret) {
                                ssize_t (*read)(struct file *, char *, size_t, loff_t *);
                                ret = -EINVAL;
                                if (file->f_op && (read = file->f_op->read) != NULL)
                                        ret = read(file, buf, count, &file->f_pos);
                        }
                }
                if (ret > 0)
                        dnotify_parent(file->f_dentry, DN_ACCESS);
                fput(file);
        }
        return ret;
}

asmlinkage ssize_t sys_write(unsigned int fd, const char * buf, size_t count)
{
        ssize_t ret;
        struct file * file;

        ret = -EBADF;
        file = fget(fd);
        if (file) {
                if (file->f_mode & FMODE_WRITE) {
                        struct inode *inode = file->f_dentry->d_inode;
                        ret = locks_verify_area(FLOCK_VERIFY_WRITE, inode, file,
                                file->f_pos, count);
                        if (!ret) {
                                ssize_t (*write)(struct file *, const char *, size_t, loff_t *);
                                ret = -EINVAL;
                                if (file->f_op && (write = file->f_op->write) != NULL)
                                        ret = write(file, buf, count, &file->f_pos);
                        }
                }
                if (ret > 0)
                        dnotify_parent(file->f_dentry, DN_MODIFY);
                fput(file);
        }
        return ret;
}


static ssize_t do_readv_writev(int type, struct file *file,
                               const struct iovec * vector,
                               unsigned long count)
{
        typedef ssize_t (*io_fn_t)(struct file *, char *, size_t, loff_t *);
        typedef ssize_t (*iov_fn_t)(struct file *, const struct iovec *, unsigned long, loff_t *);

        ssize_t tot_len;
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov=iovstack;
        ssize_t ret, i;
        io_fn_t fn;
        iov_fn_t fnv;
        struct inode *inode;

        /*
         * First get the "struct iovec" from user memory and
         * verify all the pointers
         */
        ret = 0;
        if (!count)
                goto out_nofree;
        ret = -EINVAL;
        if (count > UIO_MAXIOV)
                goto out_nofree;
        if (!file->f_op)
                goto out_nofree;
        if (count > UIO_FASTIOV) {
                ret = -ENOMEM;
                iov = kmalloc(count*sizeof(struct iovec), GFP_KERNEL);
                if (!iov)
                        goto out_nofree;
        }
        ret = -EFAULT;
        if (copy_from_user(iov, vector, count*sizeof(*vector)))
                goto out;

        /*
         * Single unix specification:
         * We should -EINVAL if an element length is not >= 0 and fitting an ssize_t
         * The total length is fitting an ssize_t
         *
         * Be careful here because iov_len is a size_t not an ssize_t
         */
         
        tot_len = 0;
        ret = -EINVAL;
        for (i = 0 ; i < count ; i++) {
                ssize_t tmp = tot_len;
                ssize_t len = (ssize_t) iov[i].iov_len;
                if (len < 0)    /* size_t not fitting an ssize_t .. */
                        goto out;
                tot_len += len;
                if (tot_len < tmp) /* maths overflow on the ssize_t */
                        goto out;
        }

        inode = file->f_dentry->d_inode;
        /* VERIFY_WRITE actually means a read, as we write to user space */
        ret = locks_verify_area((type == VERIFY_WRITE
                                 ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE),
                                inode, file, file->f_pos, tot_len);
        if (ret) goto out;

        fnv = (type == VERIFY_WRITE ? file->f_op->readv : file->f_op->writev);
        if (fnv) {
                ret = fnv(file, iov, count, &file->f_pos);
                goto out;
        }

        /* VERIFY_WRITE actually means a read, as we write to user space */
        fn = (type == VERIFY_WRITE ? file->f_op->read :
              (io_fn_t) file->f_op->write);

        ret = 0;
        vector = iov;
        while (count > 0) {
                void * base;
                size_t len;
                ssize_t nr;

                base = vector->iov_base;
                len = vector->iov_len;
                vector++;
                count--;

                nr = fn(file, base, len, &file->f_pos);

                if (nr < 0) {
                        if (!ret) ret = nr;
                        break;
                }
                ret += nr;
                if (nr != len)
                        break;
        }

out:
        if (iov != iovstack)
                kfree(iov);
out_nofree:
        /* VERIFY_WRITE actually means a read, as we write to user space */
        if ((ret + (type == VERIFY_WRITE)) > 0)
                dnotify_parent(file->f_dentry,
                        (type == VERIFY_WRITE) ? DN_MODIFY : DN_ACCESS);
        return ret;
}

asmlinkage ssize_t sys_readv(unsigned long fd, const struct iovec * vector,
                             unsigned long count)
{
        struct file * file;
        ssize_t ret;


        ret = -EBADF;
        file = fget(fd);
        if (!file)
                goto bad_file;
        if (file->f_op && (file->f_mode & FMODE_READ) &&
            (file->f_op->readv || file->f_op->read))
                ret = do_readv_writev(VERIFY_WRITE, file, vector, count);
        fput(file);

bad_file:
        return ret;
}

asmlinkage ssize_t sys_writev(unsigned long fd, const struct iovec * vector,
                              unsigned long count)
{
        struct file * file;
        ssize_t ret;


        ret = -EBADF;
        file = fget(fd);
        if (!file)
                goto bad_file;
        if (file->f_op && (file->f_mode & FMODE_WRITE) &&
            (file->f_op->writev || file->f_op->write))
                ret = do_readv_writev(VERIFY_READ, file, vector, count);
        fput(file);

bad_file:
        return ret;
}

/* From the Single Unix Spec: pread & pwrite act like lseek to pos + op +
   lseek back to original location.  They fail just like lseek does on
   non-seekable files.  */

asmlinkage ssize_t sys_pread(unsigned int fd, char * buf,
                             size_t count, loff_t pos)
{
        ssize_t ret;
        struct file * file;
        ssize_t (*read)(struct file *, char *, size_t, loff_t *);

        ret = -EBADF;
        file = fget(fd);
        if (!file)
                goto bad_file;
        if (!(file->f_mode & FMODE_READ))
                goto out;
        ret = locks_verify_area(FLOCK_VERIFY_READ, file->f_dentry->d_inode,
                                file, pos, count);
        if (ret)
                goto out;
        ret = -EINVAL;
        if (!file->f_op || !(read = file->f_op->read))
                goto out;
        if (pos < 0)
                goto out;
        ret = read(file, buf, count, &pos);
        if (ret > 0)
                dnotify_parent(file->f_dentry, DN_ACCESS);
out:
        fput(file);
bad_file:
        return ret;
}

asmlinkage ssize_t sys_pwrite(unsigned int fd, const char * buf,
                              size_t count, loff_t pos)
{
        ssize_t ret;
        struct file * file;
        ssize_t (*write)(struct file *, const char *, size_t, loff_t *);

        ret = -EBADF;
        file = fget(fd);
        if (!file)
                goto bad_file;
        if (!(file->f_mode & FMODE_WRITE))
                goto out;
        ret = locks_verify_area(FLOCK_VERIFY_WRITE, file->f_dentry->d_inode,
                                file, pos, count);
        if (ret)
                goto out;
        ret = -EINVAL;
        if (!file->f_op || !(write = file->f_op->write))
                goto out;
        if (pos < 0)
                goto out;

        ret = write(file, buf, count, &pos);
        if (ret > 0)
                dnotify_parent(file->f_dentry, DN_MODIFY);
out:
        fput(file);
bad_file:
        return ret;
}