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

#include <linux/slab.h> 
#include <linux/stat.h>
#include <linux/fcntl.h>
#include <linux/file.h>
#include <linux/uio.h>
#include <linux/aio.h>
#include <linux/fsnotify.h>
#include <linux/security.h>
#include <linux/export.h>
#include <linux/syscalls.h>
#include <linux/pagemap.h>
#include <linux/splice.h>
#include <linux/compat.h>
#include "internal.h"

#include <asm/uaccess.h>
#include <asm/unistd.h>

typedef ssize_t (*io_fn_t)(struct file *, char __user *, size_t, loff_t *);
typedef ssize_t (*iov_fn_t)(struct kiocb *, const struct iovec *,
                unsigned long, loff_t);
typedef ssize_t (*iter_fn_t)(struct kiocb *, struct iov_iter *);

const struct file_operations generic_ro_fops = {
        .llseek         = generic_file_llseek,
        .read           = new_sync_read,
        .read_iter      = generic_file_read_iter,
        .mmap           = generic_file_readonly_mmap,
        .splice_read    = generic_file_splice_read,
};

EXPORT_SYMBOL(generic_ro_fops);

static inline int unsigned_offsets(struct file *file)
{
        return file->f_mode & FMODE_UNSIGNED_OFFSET;
}

/**
 * vfs_setpos - update the file offset for lseek
 * @file:       file structure in question
 * @offset:     file offset to seek to
 * @maxsize:    maximum file size
 *
 * This is a low-level filesystem helper for updating the file offset to
 * the value specified by @offset if the given offset is valid and it is
 * not equal to the current file offset.
 *
 * Return the specified offset on success and -EINVAL on invalid offset.
 */
loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize)
{
        if (offset < 0 && !unsigned_offsets(file))
                return -EINVAL;
        if (offset > maxsize)
                return -EINVAL;

        if (offset != file->f_pos) {
                file->f_pos = offset;
                file->f_version = 0;
        }
        return offset;
}
EXPORT_SYMBOL(vfs_setpos);

/**
 * generic_file_llseek_size - generic llseek implementation for regular files
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 * @size:       max size of this file in file system
 * @eof:        offset used for SEEK_END position
 *
 * This is a variant of generic_file_llseek that allows passing in a custom
 * maximum file size and a custom EOF position, for e.g. hashed directories
 *
 * Synchronization:
 * SEEK_SET and SEEK_END are unsynchronized (but atomic on 64bit platforms)
 * SEEK_CUR is synchronized against other SEEK_CURs, but not read/writes.
 * read/writes behave like SEEK_SET against seeks.
 */
loff_t
generic_file_llseek_size(struct file *file, loff_t offset, int whence,
                loff_t maxsize, loff_t eof)
{
        switch (whence) {
        case SEEK_END:
                offset += eof;
                break;
        case SEEK_CUR:
                /*
                 * Here we special-case the lseek(fd, 0, SEEK_CUR)
                 * position-querying operation.  Avoid rewriting the "same"
                 * f_pos value back to the file because a concurrent read(),
                 * write() or lseek() might have altered it
                 */
                if (offset == 0)
                        return file->f_pos;
                /*
                 * f_lock protects against read/modify/write race with other
                 * SEEK_CURs. Note that parallel writes and reads behave
                 * like SEEK_SET.
                 */
                spin_lock(&file->f_lock);
                offset = vfs_setpos(file, file->f_pos + offset, maxsize);
                spin_unlock(&file->f_lock);
                return offset;
        case SEEK_DATA:
                /*
                 * In the generic case the entire file is data, so as long as
                 * offset isn't at the end of the file then the offset is data.
                 */
                if (offset >= eof)
                        return -ENXIO;
                break;
        case SEEK_HOLE:
                /*
                 * There is a virtual hole at the end of the file, so as long as
                 * offset isn't i_size or larger, return i_size.
                 */
                if (offset >= eof)
                        return -ENXIO;
                offset = eof;
                break;
        }

        return vfs_setpos(file, offset, maxsize);
}
EXPORT_SYMBOL(generic_file_llseek_size);

/**
 * generic_file_llseek - generic llseek implementation for regular files
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 *
 * This is a generic implemenation of ->llseek useable for all normal local
 * filesystems.  It just updates the file offset to the value specified by
 * @offset and @whence.
 */
loff_t generic_file_llseek(struct file *file, loff_t offset, int whence)
{
        struct inode *inode = file->f_mapping->host;

        return generic_file_llseek_size(file, offset, whence,
                                        inode->i_sb->s_maxbytes,
                                        i_size_read(inode));
}
EXPORT_SYMBOL(generic_file_llseek);

/**
 * fixed_size_llseek - llseek implementation for fixed-sized devices
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 * @size:       size of the file
 *
 */
loff_t fixed_size_llseek(struct file *file, loff_t offset, int whence, loff_t size)
{
        switch (whence) {
        case SEEK_SET: case SEEK_CUR: case SEEK_END:
                return generic_file_llseek_size(file, offset, whence,
                                                size, size);
        default:
                return -EINVAL;
        }
}
EXPORT_SYMBOL(fixed_size_llseek);

/**
 * noop_llseek - No Operation Performed llseek implementation
 * @file:       file structure to seek on
 * @offset:     file offset to seek to
 * @whence:     type of seek
 *
 * This is an implementation of ->llseek useable for the rare special case when
 * userspace expects the seek to succeed but the (device) file is actually not
 * able to perform the seek. In this case you use noop_llseek() instead of
 * falling back to the default implementation of ->llseek.
 */
loff_t noop_llseek(struct file *file, loff_t offset, int whence)
{
        return file->f_pos;
}
EXPORT_SYMBOL(noop_llseek);

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

loff_t default_llseek(struct file *file, loff_t offset, int whence)
{
        struct inode *inode = file_inode(file);
        loff_t retval;

        mutex_lock(&inode->i_mutex);
        switch (whence) {
                case SEEK_END:
                        offset += i_size_read(inode);
                        break;
                case SEEK_CUR:
                        if (offset == 0) {
                                retval = file->f_pos;
                                goto out;
                        }
                        offset += file->f_pos;
                        break;
                case SEEK_DATA:
                        /*
                         * In the generic case the entire file is data, so as
                         * long as offset isn't at the end of the file then the
                         * offset is data.
                         */
                        if (offset >= inode->i_size) {
                                retval = -ENXIO;
                                goto out;
                        }
                        break;
                case SEEK_HOLE:
                        /*
                         * There is a virtual hole at the end of the file, so
                         * as long as offset isn't i_size or larger, return
                         * i_size.
                         */
                        if (offset >= inode->i_size) {
                                retval = -ENXIO;
                                goto out;
                        }
                        offset = inode->i_size;
                        break;
        }
        retval = -EINVAL;
        if (offset >= 0 || unsigned_offsets(file)) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_version = 0;
                }
                retval = offset;
        }
out:
        mutex_unlock(&inode->i_mutex);
        return retval;
}
EXPORT_SYMBOL(default_llseek);

loff_t vfs_llseek(struct file *file, loff_t offset, int whence)
{
        loff_t (*fn)(struct file *, loff_t, int);

        fn = no_llseek;
        if (file->f_mode & FMODE_LSEEK) {
                if (file->f_op->llseek)
                        fn = file->f_op->llseek;
        }
        return fn(file, offset, whence);
}
EXPORT_SYMBOL(vfs_llseek);

static inline struct fd fdget_pos(int fd)
{
        return __to_fd(__fdget_pos(fd));
}

static inline void fdput_pos(struct fd f)
{
        if (f.flags & FDPUT_POS_UNLOCK)
                mutex_unlock(&f.file->f_pos_lock);
        fdput(f);
}

SYSCALL_DEFINE3(lseek, unsigned int, fd, off_t, offset, unsigned int, whence)
{
        off_t retval;
        struct fd f = fdget_pos(fd);
        if (!f.file)
                return -EBADF;

        retval = -EINVAL;
        if (whence <= SEEK_MAX) {
                loff_t res = vfs_llseek(f.file, offset, whence);
                retval = res;
                if (res != (loff_t)retval)
                        retval = -EOVERFLOW;    /* LFS: should only happen on 32 bit platforms */
        }
        fdput_pos(f);
        return retval;
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE3(lseek, unsigned int, fd, compat_off_t, offset, unsigned int, whence)
{
        return sys_lseek(fd, offset, whence);
}
#endif

#ifdef __ARCH_WANT_SYS_LLSEEK
SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned long, offset_high,
                unsigned long, offset_low, loff_t __user *, result,
                unsigned int, whence)
{
        int retval;
        struct fd f = fdget_pos(fd);
        loff_t offset;

        if (!f.file)
                return -EBADF;

        retval = -EINVAL;
        if (whence > SEEK_MAX)
                goto out_putf;

        offset = vfs_llseek(f.file, ((loff_t) offset_high << 32) | offset_low,
                        whence);

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

ssize_t vfs_iter_read(struct file *file, struct iov_iter *iter, loff_t *ppos)
{
        struct kiocb kiocb;
        ssize_t ret;

        if (!file->f_op->read_iter)
                return -EINVAL;

        init_sync_kiocb(&kiocb, file);
        kiocb.ki_pos = *ppos;
        kiocb.ki_nbytes = iov_iter_count(iter);

        iter->type |= READ;
        ret = file->f_op->read_iter(&kiocb, iter);
        if (ret == -EIOCBQUEUED)
                ret = wait_on_sync_kiocb(&kiocb);

        if (ret > 0)
                *ppos = kiocb.ki_pos;
        return ret;
}
EXPORT_SYMBOL(vfs_iter_read);

ssize_t vfs_iter_write(struct file *file, struct iov_iter *iter, loff_t *ppos)
{
        struct kiocb kiocb;
        ssize_t ret;

        if (!file->f_op->write_iter)
                return -EINVAL;

        init_sync_kiocb(&kiocb, file);
        kiocb.ki_pos = *ppos;
        kiocb.ki_nbytes = iov_iter_count(iter);

        iter->type |= WRITE;
        ret = file->f_op->write_iter(&kiocb, iter);
        if (ret == -EIOCBQUEUED)
                ret = wait_on_sync_kiocb(&kiocb);

        if (ret > 0)
                *ppos = kiocb.ki_pos;
        return ret;
}
EXPORT_SYMBOL(vfs_iter_write);

/*
 * rw_verify_area doesn't like huge counts. We limit
 * them to something that fits in "int" so that others
 * won't have to do range checks all the time.
 */
int rw_verify_area(int read_write, struct file *file, const loff_t *ppos, size_t count)
{
        struct inode *inode;
        loff_t pos;
        int retval = -EINVAL;

        inode = file_inode(file);
        if (unlikely((ssize_t) count < 0))
                return retval;
        pos = *ppos;
        if (unlikely(pos < 0)) {
                if (!unsigned_offsets(file))
                        return retval;
                if (count >= -pos) /* both values are in 0..LLONG_MAX */
                        return -EOVERFLOW;
        } else if (unlikely((loff_t) (pos + count) < 0)) {
                if (!unsigned_offsets(file))
                        return retval;
        }

        if (unlikely(inode->i_flctx && mandatory_lock(inode))) {
                retval = locks_mandatory_area(
                        read_write == READ ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE,
                        inode, file, pos, count);
                if (retval < 0)
                        return retval;
        }
        retval = security_file_permission(file,
                                read_write == READ ? MAY_READ : MAY_WRITE);
        if (retval)
                return retval;
        return count > MAX_RW_COUNT ? MAX_RW_COUNT : count;
}

ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
{
        struct iovec iov = { .iov_base = buf, .iov_len = len };
        struct kiocb kiocb;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        kiocb.ki_nbytes = len;

        ret = filp->f_op->aio_read(&kiocb, &iov, 1, kiocb.ki_pos);
        if (-EIOCBQUEUED == ret)
                ret = wait_on_sync_kiocb(&kiocb);
        *ppos = kiocb.ki_pos;
        return ret;
}

EXPORT_SYMBOL(do_sync_read);

ssize_t new_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
{
        struct iovec iov = { .iov_base = buf, .iov_len = len };
        struct kiocb kiocb;
        struct iov_iter iter;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        kiocb.ki_nbytes = len;
        iov_iter_init(&iter, READ, &iov, 1, len);

        ret = filp->f_op->read_iter(&kiocb, &iter);
        if (-EIOCBQUEUED == ret)
                ret = wait_on_sync_kiocb(&kiocb);
        *ppos = kiocb.ki_pos;
        return ret;
}

EXPORT_SYMBOL(new_sync_read);

ssize_t __vfs_read(struct file *file, char __user *buf, size_t count,
                   loff_t *pos)
{
        ssize_t ret;

        if (file->f_op->read)
                ret = file->f_op->read(file, buf, count, pos);
        else if (file->f_op->aio_read)
                ret = do_sync_read(file, buf, count, pos);
        else if (file->f_op->read_iter)
                ret = new_sync_read(file, buf, count, pos);
        else
                ret = -EINVAL;

        return ret;
}

ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
{
        ssize_t ret;

        if (!(file->f_mode & FMODE_READ))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_READ))
                return -EINVAL;
        if (unlikely(!access_ok(VERIFY_WRITE, buf, count)))
                return -EFAULT;

        ret = rw_verify_area(READ, file, pos, count);
        if (ret >= 0) {
                count = ret;
                ret = __vfs_read(file, buf, count, pos);
                if (ret > 0) {
                        fsnotify_access(file);
                        add_rchar(current, ret);
                }
                inc_syscr(current);
        }

        return ret;
}

EXPORT_SYMBOL(vfs_read);

ssize_t do_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
{
        struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = len };
        struct kiocb kiocb;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        kiocb.ki_nbytes = len;

        ret = filp->f_op->aio_write(&kiocb, &iov, 1, kiocb.ki_pos);
        if (-EIOCBQUEUED == ret)
                ret = wait_on_sync_kiocb(&kiocb);
        *ppos = kiocb.ki_pos;
        return ret;
}

EXPORT_SYMBOL(do_sync_write);

ssize_t new_sync_write(struct file *filp, const char __user *buf, size_t len, loff_t *ppos)
{
        struct iovec iov = { .iov_base = (void __user *)buf, .iov_len = len };
        struct kiocb kiocb;
        struct iov_iter iter;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        kiocb.ki_nbytes = len;
        iov_iter_init(&iter, WRITE, &iov, 1, len);

        ret = filp->f_op->write_iter(&kiocb, &iter);
        if (-EIOCBQUEUED == ret)
                ret = wait_on_sync_kiocb(&kiocb);
        *ppos = kiocb.ki_pos;
        return ret;
}

EXPORT_SYMBOL(new_sync_write);

ssize_t __kernel_write(struct file *file, const char *buf, size_t count, loff_t *pos)
{
        mm_segment_t old_fs;
        const char __user *p;
        ssize_t ret;

        if (!(file->f_mode & FMODE_CAN_WRITE))
                return -EINVAL;

        old_fs = get_fs();
        set_fs(get_ds());
        p = (__force const char __user *)buf;
        if (count > MAX_RW_COUNT)
                count =  MAX_RW_COUNT;
        if (file->f_op->write)
                ret = file->f_op->write(file, p, count, pos);
        else if (file->f_op->aio_write)
                ret = do_sync_write(file, p, count, pos);
        else
                ret = new_sync_write(file, p, count, pos);
        set_fs(old_fs);
        if (ret > 0) {
                fsnotify_modify(file);
                add_wchar(current, ret);
        }
        inc_syscw(current);
        return ret;
}

EXPORT_SYMBOL(__kernel_write);

ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
{
        ssize_t ret;

        if (!(file->f_mode & FMODE_WRITE))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_WRITE))
                return -EINVAL;
        if (unlikely(!access_ok(VERIFY_READ, buf, count)))
                return -EFAULT;

        ret = rw_verify_area(WRITE, file, pos, count);
        if (ret >= 0) {
                count = ret;
                file_start_write(file);
                if (file->f_op->write)
                        ret = file->f_op->write(file, buf, count, pos);
                else if (file->f_op->aio_write)
                        ret = do_sync_write(file, buf, count, pos);
                else
                        ret = new_sync_write(file, buf, count, pos);
                if (ret > 0) {
                        fsnotify_modify(file);
                        add_wchar(current, ret);
                }
                inc_syscw(current);
                file_end_write(file);
        }

        return ret;
}

EXPORT_SYMBOL(vfs_write);

static inline loff_t file_pos_read(struct file *file)
{
        return file->f_pos;
}

static inline void file_pos_write(struct file *file, loff_t pos)
{
        file->f_pos = pos;
}

SYSCALL_DEFINE3(read, unsigned int, fd, char __user *, buf, size_t, count)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;

        if (f.file) {
                loff_t pos = file_pos_read(f.file);
                ret = vfs_read(f.file, buf, count, &pos);
                if (ret >= 0)
                        file_pos_write(f.file, pos);
                fdput_pos(f);
        }
        return ret;
}

SYSCALL_DEFINE3(write, unsigned int, fd, const char __user *, buf,
                size_t, count)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;

        if (f.file) {
                loff_t pos = file_pos_read(f.file);
                ret = vfs_write(f.file, buf, count, &pos);
                if (ret >= 0)
                        file_pos_write(f.file, pos);
                fdput_pos(f);
        }

        return ret;
}

SYSCALL_DEFINE4(pread64, unsigned int, fd, char __user *, buf,
                        size_t, count, loff_t, pos)
{
        struct fd f;
        ssize_t ret = -EBADF;

        if (pos < 0)
                return -EINVAL;

        f = fdget(fd);
        if (f.file) {
                ret = -ESPIPE;
                if (f.file->f_mode & FMODE_PREAD)
                        ret = vfs_read(f.file, buf, count, &pos);
                fdput(f);
        }

        return ret;
}

SYSCALL_DEFINE4(pwrite64, unsigned int, fd, const char __user *, buf,
                         size_t, count, loff_t, pos)
{
        struct fd f;
        ssize_t ret = -EBADF;

        if (pos < 0)
                return -EINVAL;

        f = fdget(fd);
        if (f.file) {
                ret = -ESPIPE;
                if (f.file->f_mode & FMODE_PWRITE)  
                        ret = vfs_write(f.file, buf, count, &pos);
                fdput(f);
        }

        return ret;
}

/*
 * Reduce an iovec's length in-place.  Return the resulting number of segments
 */
unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to)
{
        unsigned long seg = 0;
        size_t len = 0;

        while (seg < nr_segs) {
                seg++;
                if (len + iov->iov_len >= to) {
                        iov->iov_len = to - len;
                        break;
                }
                len += iov->iov_len;
                iov++;
        }
        return seg;
}
EXPORT_SYMBOL(iov_shorten);

static ssize_t do_iter_readv_writev(struct file *filp, int rw, const struct iovec *iov,
                unsigned long nr_segs, size_t len, loff_t *ppos, iter_fn_t fn)
{
        struct kiocb kiocb;
        struct iov_iter iter;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        kiocb.ki_nbytes = len;

        iov_iter_init(&iter, rw, iov, nr_segs, len);
        ret = fn(&kiocb, &iter);
        if (ret == -EIOCBQUEUED)
                ret = wait_on_sync_kiocb(&kiocb);
        *ppos = kiocb.ki_pos;
        return ret;
}

static ssize_t do_sync_readv_writev(struct file *filp, const struct iovec *iov,
                unsigned long nr_segs, size_t len, loff_t *ppos, iov_fn_t fn)
{
        struct kiocb kiocb;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        kiocb.ki_nbytes = len;

        ret = fn(&kiocb, iov, nr_segs, kiocb.ki_pos);
        if (ret == -EIOCBQUEUED)
                ret = wait_on_sync_kiocb(&kiocb);
        *ppos = kiocb.ki_pos;
        return ret;
}

/* Do it by hand, with file-ops */
static ssize_t do_loop_readv_writev(struct file *filp, struct iovec *iov,
                unsigned long nr_segs, loff_t *ppos, io_fn_t fn)
{
        struct iovec *vector = iov;
        ssize_t ret = 0;

        while (nr_segs > 0) {
                void __user *base;
                size_t len;
                ssize_t nr;

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

                nr = fn(filp, base, len, ppos);

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

        return ret;
}

/* A write operation does a read from user space and vice versa */
#define vrfy_dir(type) ((type) == READ ? VERIFY_WRITE : VERIFY_READ)

ssize_t rw_copy_check_uvector(int type, const struct iovec __user * uvector,
                              unsigned long nr_segs, unsigned long fast_segs,
                              struct iovec *fast_pointer,
                              struct iovec **ret_pointer)
{
        unsigned long seg;
        ssize_t ret;
        struct iovec *iov = fast_pointer;

        /*
         * SuS says "The readv() function *may* fail if the iovcnt argument
         * was less than or equal to 0, or greater than {IOV_MAX}.  Linux has
         * traditionally returned zero for zero segments, so...
         */
        if (nr_segs == 0) {
                ret = 0;
                goto out;
        }

        /*
         * First get the "struct iovec" from user memory and
         * verify all the pointers
         */
        if (nr_segs > UIO_MAXIOV) {
                ret = -EINVAL;
                goto out;
        }
        if (nr_segs > fast_segs) {
                iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
                if (iov == NULL) {
                        ret = -ENOMEM;
                        goto out;
                }
        }
        if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector))) {
                ret = -EFAULT;
                goto out;
        }

        /*
         * According to the Single Unix Specification we should return EINVAL
         * if an element length is < 0 when cast to ssize_t or if the
         * total length would overflow the ssize_t return value of the
         * system call.
         *
         * Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
         * overflow case.
         */
        ret = 0;
        for (seg = 0; seg < nr_segs; seg++) {
                void __user *buf = iov[seg].iov_base;
                ssize_t len = (ssize_t)iov[seg].iov_len;

                /* see if we we're about to use an invalid len or if
                 * it's about to overflow ssize_t */
                if (len < 0) {
                        ret = -EINVAL;
                        goto out;
                }
                if (type >= 0
                    && unlikely(!access_ok(vrfy_dir(type), buf, len))) {
                        ret = -EFAULT;
                        goto out;
                }
                if (len > MAX_RW_COUNT - ret) {
                        len = MAX_RW_COUNT - ret;
                        iov[seg].iov_len = len;
                }
                ret += len;
        }
out:
        *ret_pointer = iov;
        return ret;
}

static ssize_t do_readv_writev(int type, struct file *file,
                               const struct iovec __user * uvector,
                               unsigned long nr_segs, loff_t *pos)
{
        size_t tot_len;
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov = iovstack;
        ssize_t ret;
        io_fn_t fn;
        iov_fn_t fnv;
        iter_fn_t iter_fn;

        ret = rw_copy_check_uvector(type, uvector, nr_segs,
                                    ARRAY_SIZE(iovstack), iovstack, &iov);
        if (ret <= 0)
                goto out;

        tot_len = ret;
        ret = rw_verify_area(type, file, pos, tot_len);
        if (ret < 0)
                goto out;

        fnv = NULL;
        if (type == READ) {
                fn = file->f_op->read;
                fnv = file->f_op->aio_read;
                iter_fn = file->f_op->read_iter;
        } else {
                fn = (io_fn_t)file->f_op->write;
                fnv = file->f_op->aio_write;
                iter_fn = file->f_op->write_iter;
                file_start_write(file);
        }

        if (iter_fn)
                ret = do_iter_readv_writev(file, type, iov, nr_segs, tot_len,
                                                pos, iter_fn);
        else if (fnv)
                ret = do_sync_readv_writev(file, iov, nr_segs, tot_len,
                                                pos, fnv);
        else
                ret = do_loop_readv_writev(file, iov, nr_segs, pos, fn);

        if (type != READ)
                file_end_write(file);

out:
        if (iov != iovstack)
                kfree(iov);
        if ((ret + (type == READ)) > 0) {
                if (type == READ)
                        fsnotify_access(file);
                else
                        fsnotify_modify(file);
        }
        return ret;
}

ssize_t vfs_readv(struct file *file, const struct iovec __user *vec,
                  unsigned long vlen, loff_t *pos)
{
        if (!(file->f_mode & FMODE_READ))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_READ))
                return -EINVAL;

        return do_readv_writev(READ, file, vec, vlen, pos);
}

EXPORT_SYMBOL(vfs_readv);

ssize_t vfs_writev(struct file *file, const struct iovec __user *vec,
                   unsigned long vlen, loff_t *pos)
{
        if (!(file->f_mode & FMODE_WRITE))
                return -EBADF;
        if (!(file->f_mode & FMODE_CAN_WRITE))
                return -EINVAL;

        return do_readv_writev(WRITE, file, vec, vlen, pos);
}

EXPORT_SYMBOL(vfs_writev);

SYSCALL_DEFINE3(readv, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;

        if (f.file) {
                loff_t pos = file_pos_read(f.file);
                ret = vfs_readv(f.file, vec, vlen, &pos);
                if (ret >= 0)
                        file_pos_write(f.file, pos);
                fdput_pos(f);
        }

        if (ret > 0)
                add_rchar(current, ret);
        inc_syscr(current);
        return ret;
}

SYSCALL_DEFINE3(writev, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret = -EBADF;

        if (f.file) {
                loff_t pos = file_pos_read(f.file);
                ret = vfs_writev(f.file, vec, vlen, &pos);
                if (ret >= 0)
                        file_pos_write(f.file, pos);
                fdput_pos(f);
        }

        if (ret > 0)
                add_wchar(current, ret);
        inc_syscw(current);
        return ret;
}

static inline loff_t pos_from_hilo(unsigned long high, unsigned long low)
{
#define HALF_LONG_BITS (BITS_PER_LONG / 2)
        return (((loff_t)high << HALF_LONG_BITS) << HALF_LONG_BITS) | low;
}

SYSCALL_DEFINE5(preadv, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h)
{
        loff_t pos = pos_from_hilo(pos_h, pos_l);
        struct fd f;
        ssize_t ret = -EBADF;

        if (pos < 0)
                return -EINVAL;

        f = fdget(fd);
        if (f.file) {

                ret = -ESPIPE;
                if (f.file->f_mode & FMODE_PREAD)
                        ret = vfs_readv(f.file, vec, vlen, &pos);
                fdput(f);
        }

        if (ret > 0)
                add_rchar(current, ret);
        inc_syscr(current);
        return ret;
}

SYSCALL_DEFINE5(pwritev, unsigned long, fd, const struct iovec __user *, vec,
                unsigned long, vlen, unsigned long, pos_l, unsigned long, pos_h)
{
        loff_t pos = pos_from_hilo(pos_h, pos_l);
        struct fd f;
        ssize_t ret = -EBADF;

        if (pos < 0)
                return -EINVAL;

        f = fdget(fd);
        if (f.file) {
                ret = -ESPIPE;
                if (f.file->f_mode & FMODE_PWRITE)
                        ret = vfs_writev(f.file, vec, vlen, &pos);
                fdput(f);
        }

        if (ret > 0)
                add_wchar(current, ret);
        inc_syscw(current);
        return ret;
}

#ifdef CONFIG_COMPAT

static ssize_t compat_do_readv_writev(int type, struct file *file,
                               const struct compat_iovec __user *uvector,
                               unsigned long nr_segs, loff_t *pos)
{
        compat_ssize_t tot_len;
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov = iovstack;
        ssize_t ret;
        io_fn_t fn;
        iov_fn_t fnv;
        iter_fn_t iter_fn;

        ret = compat_rw_copy_check_uvector(type, uvector, nr_segs,
                                               UIO_FASTIOV, iovstack, &iov);
        if (ret <= 0)
                goto out;

        tot_len = ret;
        ret = rw_verify_area(type, file, pos, tot_len);
        if (ret < 0)
                goto out;

        fnv = NULL;
        if (type == READ) {
                fn = file->f_op->read;
                fnv = file->f_op->aio_read;
                iter_fn = file->f_op->read_iter;
        } else {
                fn = (io_fn_t)file->f_op->write;
                fnv = file->f_op->aio_write;
                iter_fn = file->f_op->write_iter;
                file_start_write(file);
        }

        if (iter_fn)
                ret = do_iter_readv_writev(file, type, iov, nr_segs, tot_len,
                                                pos, iter_fn);
        else if (fnv)
                ret = do_sync_readv_writev(file, iov, nr_segs, tot_len,
                                                pos, fnv);
        else
                ret = do_loop_readv_writev(file, iov, nr_segs, pos, fn);

        if (type != READ)
                file_end_write(file);

out:
        if (iov != iovstack)
                kfree(iov);
        if ((ret + (type == READ)) > 0) {
                if (type == READ)
                        fsnotify_access(file);
                else
                        fsnotify_modify(file);
        }
        return ret;
}

static size_t compat_readv(struct file *file,
                           const struct compat_iovec __user *vec,
                           unsigned long vlen, loff_t *pos)
{
        ssize_t ret = -EBADF;

        if (!(file->f_mode & FMODE_READ))
                goto out;

        ret = -EINVAL;
        if (!(file->f_mode & FMODE_CAN_READ))
                goto out;

        ret = compat_do_readv_writev(READ, file, vec, vlen, pos);

out:
        if (ret > 0)
                add_rchar(current, ret);
        inc_syscr(current);
        return ret;
}

COMPAT_SYSCALL_DEFINE3(readv, compat_ulong_t, fd,
                const struct compat_iovec __user *,vec,
                compat_ulong_t, vlen)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret;
        loff_t pos;

        if (!f.file)
                return -EBADF;
        pos = f.file->f_pos;
        ret = compat_readv(f.file, vec, vlen, &pos);
        if (ret >= 0)
                f.file->f_pos = pos;
        fdput_pos(f);
        return ret;
}

static long __compat_sys_preadv64(unsigned long fd,
                                  const struct compat_iovec __user *vec,
                                  unsigned long vlen, loff_t pos)
{
        struct fd f;
        ssize_t ret;

        if (pos < 0)
                return -EINVAL;
        f = fdget(fd);
        if (!f.file)
                return -EBADF;
        ret = -ESPIPE;
        if (f.file->f_mode & FMODE_PREAD)
                ret = compat_readv(f.file, vec, vlen, &pos);
        fdput(f);
        return ret;
}

#ifdef __ARCH_WANT_COMPAT_SYS_PREADV64
COMPAT_SYSCALL_DEFINE4(preadv64, unsigned long, fd,
                const struct compat_iovec __user *,vec,
                unsigned long, vlen, loff_t, pos)
{
        return __compat_sys_preadv64(fd, vec, vlen, pos);
}
#endif

COMPAT_SYSCALL_DEFINE5(preadv, compat_ulong_t, fd,
                const struct compat_iovec __user *,vec,
                compat_ulong_t, vlen, u32, pos_low, u32, pos_high)
{
        loff_t pos = ((loff_t)pos_high << 32) | pos_low;

        return __compat_sys_preadv64(fd, vec, vlen, pos);
}

static size_t compat_writev(struct file *file,
                            const struct compat_iovec __user *vec,
                            unsigned long vlen, loff_t *pos)
{
        ssize_t ret = -EBADF;

        if (!(file->f_mode & FMODE_WRITE))
                goto out;

        ret = -EINVAL;
        if (!(file->f_mode & FMODE_CAN_WRITE))
                goto out;

        ret = compat_do_readv_writev(WRITE, file, vec, vlen, pos);

out:
        if (ret > 0)
                add_wchar(current, ret);
        inc_syscw(current);
        return ret;
}

COMPAT_SYSCALL_DEFINE3(writev, compat_ulong_t, fd,
                const struct compat_iovec __user *, vec,
                compat_ulong_t, vlen)
{
        struct fd f = fdget_pos(fd);
        ssize_t ret;
        loff_t pos;

        if (!f.file)
                return -EBADF;
        pos = f.file->f_pos;
        ret = compat_writev(f.file, vec, vlen, &pos);
        if (ret >= 0)
                f.file->f_pos = pos;
        fdput_pos(f);
        return ret;
}

static long __compat_sys_pwritev64(unsigned long fd,
                                   const struct compat_iovec __user *vec,
                                   unsigned long vlen, loff_t pos)
{
        struct fd f;
        ssize_t ret;

        if (pos < 0)
                return -EINVAL;
        f = fdget(fd);
        if (!f.file)
                return -EBADF;
        ret = -ESPIPE;
        if (f.file->f_mode & FMODE_PWRITE)
                ret = compat_writev(f.file, vec, vlen, &pos);
        fdput(f);
        return ret;
}

#ifdef __ARCH_WANT_COMPAT_SYS_PWRITEV64
COMPAT_SYSCALL_DEFINE4(pwritev64, unsigned long, fd,
                const struct compat_iovec __user *,vec,
                unsigned long, vlen, loff_t, pos)
{
        return __compat_sys_pwritev64(fd, vec, vlen, pos);
}
#endif

COMPAT_SYSCALL_DEFINE5(pwritev, compat_ulong_t, fd,
                const struct compat_iovec __user *,vec,
                compat_ulong_t, vlen, u32, pos_low, u32, pos_high)
{
        loff_t pos = ((loff_t)pos_high << 32) | pos_low;

        return __compat_sys_pwritev64(fd, vec, vlen, pos);
}
#endif

static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
                           size_t count, loff_t max)
{
        struct fd in, out;
        struct inode *in_inode, *out_inode;
        loff_t pos;
        loff_t out_pos;
        ssize_t retval;
        int fl;

        /*
         * Get input file, and verify that it is ok..
         */
        retval = -EBADF;
        in = fdget(in_fd);
        if (!in.file)
                goto out;
        if (!(in.file->f_mode & FMODE_READ))
                goto fput_in;
        retval = -ESPIPE;
        if (!ppos) {
                pos = in.file->f_pos;
        } else {
                pos = *ppos;
                if (!(in.file->f_mode & FMODE_PREAD))
                        goto fput_in;
        }
        retval = rw_verify_area(READ, in.file, &pos, count);
        if (retval < 0)
                goto fput_in;
        count = retval;

        /*
         * Get output file, and verify that it is ok..
         */
        retval = -EBADF;
        out = fdget(out_fd);
        if (!out.file)
                goto fput_in;
        if (!(out.file->f_mode & FMODE_WRITE))
                goto fput_out;
        retval = -EINVAL;
        in_inode = file_inode(in.file);
        out_inode = file_inode(out.file);
        out_pos = out.file->f_pos;
        retval = rw_verify_area(WRITE, out.file, &out_pos, count);
        if (retval < 0)
                goto fput_out;
        count = retval;

        if (!max)
                max = min(in_inode->i_sb->s_maxbytes, out_inode->i_sb->s_maxbytes);

        if (unlikely(pos + count > max)) {
                retval = -EOVERFLOW;
                if (pos >= max)
                        goto fput_out;
                count = max - pos;
        }

        fl = 0;
#if 0
        /*
         * We need to debate whether we can enable this or not. The
         * man page documents EAGAIN return for the output at least,
         * and the application is arguably buggy if it doesn't expect
         * EAGAIN on a non-blocking file descriptor.
         */
        if (in.file->f_flags & O_NONBLOCK)
                fl = SPLICE_F_NONBLOCK;
#endif
        file_start_write(out.file);
        retval = do_splice_direct(in.file, &pos, out.file, &out_pos, count, fl);
        file_end_write(out.file);

        if (retval > 0) {
                add_rchar(current, retval);
                add_wchar(current, retval);
                fsnotify_access(in.file);
                fsnotify_modify(out.file);
                out.file->f_pos = out_pos;
                if (ppos)
                        *ppos = pos;
                else
                        in.file->f_pos = pos;
        }

        inc_syscr(current);
        inc_syscw(current);
        if (pos > max)
                retval = -EOVERFLOW;

fput_out:
        fdput(out);
fput_in:
        fdput(in);
out:
        return retval;
}

SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd, off_t __user *, offset, size_t, count)
{
        loff_t pos;
        off_t off;
        ssize_t ret;

        if (offset) {
                if (unlikely(get_user(off, offset)))
                        return -EFAULT;
                pos = off;
                ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
                if (unlikely(put_user(pos, offset)))
                        return -EFAULT;
                return ret;
        }

        return do_sendfile(out_fd, in_fd, NULL, count, 0);
}

SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd, loff_t __user *, offset, size_t, count)
{
        loff_t pos;
        ssize_t ret;

        if (offset) {
                if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
                        return -EFAULT;
                ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
                if (unlikely(put_user(pos, offset)))
                        return -EFAULT;
                return ret;
        }

        return do_sendfile(out_fd, in_fd, NULL, count, 0);
}

#ifdef CONFIG_COMPAT
COMPAT_SYSCALL_DEFINE4(sendfile, int, out_fd, int, in_fd,
                compat_off_t __user *, offset, compat_size_t, count)
{
        loff_t pos;
        off_t off;
        ssize_t ret;

        if (offset) {
                if (unlikely(get_user(off, offset)))
                        return -EFAULT;
                pos = off;
                ret = do_sendfile(out_fd, in_fd, &pos, count, MAX_NON_LFS);
                if (unlikely(put_user(pos, offset)))
                        return -EFAULT;
                return ret;
        }

        return do_sendfile(out_fd, in_fd, NULL, count, 0);
}

COMPAT_SYSCALL_DEFINE4(sendfile64, int, out_fd, int, in_fd,
                compat_loff_t __user *, offset, compat_size_t, count)
{
        loff_t pos;
        ssize_t ret;

        if (offset) {
                if (unlikely(copy_from_user(&pos, offset, sizeof(loff_t))))
                        return -EFAULT;
                ret = do_sendfile(out_fd, in_fd, &pos, count, 0);
                if (unlikely(put_user(pos, offset)))
                        return -EFAULT;
                return ret;
        }

        return do_sendfile(out_fd, in_fd, NULL, count, 0);
}
#endif