root/fs/read_write.c

/*
 *  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/smp_lock.h>
#include <linux/dnotify.h>
#include <linux/security.h>
#include <linux/module.h>

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

struct file_operations generic_ro_fops = {
        .llseek         = generic_file_llseek,
        .read           = generic_file_read,
        .mmap           = generic_file_readonly_mmap,
        .sendfile       = generic_file_sendfile,
};

EXPORT_SYMBOL(generic_ro_fops);

loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
{
        long long retval;
        struct inode *inode = file->f_mapping->host;

        down(&inode->i_sem);
        switch (origin) {
                case 2:
                        offset += inode->i_size;
                        break;
                case 1:
                        offset += file->f_pos;
        }
        retval = -EINVAL;
        if (offset>=0 && offset<=inode->i_sb->s_maxbytes) {
                if (offset != file->f_pos) {
                        file->f_pos = offset;
                        file->f_version = 0;
                }
                retval = offset;
        }
        up(&inode->i_sem);
        return retval;
}

EXPORT_SYMBOL(generic_file_llseek);

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

        lock_kernel();
        switch (origin) {
                case 2:
                        offset += i_size_read(file->f_dentry->d_inode);
                        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_version = 0;
                }
                retval = offset;
        }
        unlock_kernel();
        return retval;
}

EXPORT_SYMBOL(remote_llseek);

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

EXPORT_SYMBOL(no_llseek);

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

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

EXPORT_SYMBOL(default_llseek);

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

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

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

        retval = -EBADF;
        file = fget_light(fd, &fput_needed);
        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_light(file, fput_needed);
bad:
        return retval;
}
EXPORT_SYMBOL_GPL(sys_lseek);

#ifdef __ARCH_WANT_SYS_LLSEEK
asmlinkage long sys_llseek(unsigned int fd, unsigned long offset_high,
                           unsigned long offset_low, loff_t __user * result,
                           unsigned int origin)
{
        int retval;
        struct file * file;
        loff_t offset;
        int fput_needed;

        retval = -EBADF;
        file = fget_light(fd, &fput_needed);
        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_light(file, fput_needed);
bad:
        return retval;
}
#endif

ssize_t do_sync_read(struct file *filp, char __user *buf, size_t len, loff_t *ppos)
{
        struct kiocb kiocb;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        if ((unsigned long) filp->f_op->aio_read > PAGE_OFFSET) //kernel
                ret = filp->f_op->aio_read(&kiocb, buf, len, kiocb.ki_pos);
        else {
                //Well, the last parameter is actually 64-bits
                //We could deal with this, it would require extra work though
                //Let's just assume no one will ever call this function
                CALLDRIVER_PREP4(aio, &kiocb, buf, len, (unsigned long) kiocb.ki_pos)
                ret = calldriver((unsigned long) filp->f_op->aio_read, aio_args,aio_sizes, 4, current->mm, 1, 0);
        }

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

EXPORT_SYMBOL(do_sync_read);

ssize_t vfs_read(struct file *file, char __user *buf, size_t count, loff_t *pos)
{
        struct inode *inode = file->f_dentry->d_inode;
        ssize_t ret;

        if (!(file->f_mode & FMODE_READ))
                return -EBADF;
        if (!file->f_op || (!file->f_op->read && !file->f_op->aio_read))
                return -EINVAL;

        ret = locks_verify_area(FLOCK_VERIFY_READ, inode, file, *pos, count);
        if (!ret) {
                ret = security_file_permission (file, MAY_READ);
                if (!ret) {
                        if (file->f_op->read) {
                                if ((unsigned long) file->f_op->read > PAGE_OFFSET) //kernel
                                        ret = file->f_op->read(file, buf, count, pos);
                                else {
                                        CALLDRIVER_PREP4(read, file, buf, count, pos)
              read_sizes[0]=sizeof(*file);
          read_sizes[3]=sizeof(*pos);
                                        ret = calldriver((unsigned long) file->f_op->read, read_args, read_sizes, 4, current->mm, 9, 0);
                                }
                        }
                        else
                                ret = do_sync_read(file, buf, count, pos);
                        if (ret > 0)
                                dnotify_parent(file->f_dentry, DN_ACCESS);
                }
        }

        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 kiocb kiocb;
        ssize_t ret;

        init_sync_kiocb(&kiocb, filp);
        kiocb.ki_pos = *ppos;
        if ((unsigned long) filp->f_op->aio_write > PAGE_OFFSET) //kernel
                ret = filp->f_op->aio_write(&kiocb, buf, len, kiocb.ki_pos);
        else {
                //See commend about aio_read
                CALLDRIVER_PREP4(aio, &kiocb, buf, len, (unsigned long) kiocb.ki_pos)
                ret = calldriver((unsigned long) filp->f_op->aio_write, aio_args, aio_sizes, 4, current->mm, 1, 0);
        }


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

EXPORT_SYMBOL(do_sync_write);

ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_t *pos)
{
        struct inode *inode = file->f_dentry->d_inode;
        ssize_t ret;

        if (!(file->f_mode & FMODE_WRITE))
                return -EBADF;
        if (!file->f_op || (!file->f_op->write && !file->f_op->aio_write))
                return -EINVAL;

        ret = locks_verify_area(FLOCK_VERIFY_WRITE, inode, file, *pos, count);
        if (!ret) {
                ret = security_file_permission (file, MAY_WRITE);
                if (!ret) {
                        if (file->f_op->write) {
                                if ((unsigned long) file->f_op->write > PAGE_OFFSET) //kernel
                                        ret = file->f_op->write(file, buf, count, pos);
                                else {
                                        CALLDRIVER_PREP4(write, file, buf, count, pos)
                                        ret = calldriver((unsigned long) file->f_op->write, write_args, write_sizes, 4, current->mm, 9, 0);
                                }
                        }
                        else
                                ret = do_sync_write(file, buf, count, pos);
                        if (ret > 0)
                                dnotify_parent(file->f_dentry, DN_MODIFY);
                }
        }

        return ret;
}

EXPORT_SYMBOL(vfs_write);

asmlinkage ssize_t sys_read(unsigned int fd, char __user * buf, size_t count)
{
        struct file *file;
        ssize_t ret = -EBADF;
        int fput_needed;

        file = fget_light(fd, &fput_needed);
        if (file) {
                ret = vfs_read(file, buf, count, &file->f_pos);
                fput_light(file, fput_needed);
        }

        return ret;
}
EXPORT_SYMBOL_GPL(sys_read);

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

        file = fget_light(fd, &fput_needed);
        if (file) {
                ret = vfs_write(file, buf, count, &file->f_pos);
                fput_light(file, fput_needed);
        }

        return ret;
}

asmlinkage ssize_t sys_pread64(unsigned int fd, char __user *buf,
                             size_t count, loff_t pos)
{
        struct file *file;
        ssize_t ret = -EBADF;
        int fput_needed;

        if (pos < 0)
                return -EINVAL;

        file = fget_light(fd, &fput_needed);
        if (file) {
                ret = vfs_read(file, buf, count, &pos);
                fput_light(file, fput_needed);
        }

        return ret;
}

asmlinkage ssize_t sys_pwrite64(unsigned int fd, const char __user *buf,
                              size_t count, loff_t pos)
{
        struct file *file;
        ssize_t ret = -EBADF;
        int fput_needed;

        if (pos < 0)
                return -EINVAL;

        file = fget_light(fd, &fput_needed);
        if (file) {
                ret = vfs_write(file, buf, count, &pos);
                fput_light(file, fput_needed);
        }

        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_readv_writev(int type, struct file *file,
                               const struct iovec __user * uvector,
                               unsigned long nr_segs, loff_t *pos)
{
        typedef ssize_t (*io_fn_t)(struct file *, char __user *, size_t, loff_t *);
        typedef ssize_t (*iov_fn_t)(struct file *, const struct iovec *, unsigned long, loff_t *);

        size_t tot_len;
        struct iovec iovstack[UIO_FASTIOV];
        struct iovec *iov=iovstack, *vector;
        ssize_t ret;
        int seg;
        io_fn_t fn;
        iov_fn_t fnv;
        struct inode *inode;

        /*
         * 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...
         */
        ret = 0;
        if (nr_segs == 0)
                goto out;

        /*
         * First get the "struct iovec" from user memory and
         * verify all the pointers
         */
        ret = -EINVAL;
        if ((nr_segs > UIO_MAXIOV) || (nr_segs <= 0))
                goto out;
        if (!file->f_op)
                goto out;
        if (nr_segs > UIO_FASTIOV) {
                ret = -ENOMEM;
                iov = kmalloc(nr_segs*sizeof(struct iovec), GFP_KERNEL);
                if (!iov)
                        goto out;
        }
        ret = -EFAULT;
        if (copy_from_user(iov, uvector, nr_segs*sizeof(*uvector)))
                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 (seg = 0; seg < nr_segs; seg++) {
                ssize_t len = (ssize_t)iov[seg].iov_len;

                if (len < 0)    /* size_t not fitting an ssize_t .. */
                        goto out;
                tot_len += len;
                if ((ssize_t)tot_len < 0) /* maths overflow on the ssize_t */
                        goto out;
        }
        if (tot_len == 0) {
                ret = 0;
                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 == READ 
                                 ? FLOCK_VERIFY_READ : FLOCK_VERIFY_WRITE),
                                inode, file, *pos, tot_len);
        if (ret)
                goto out;

        fnv = NULL;
        if (type == READ) {
                fn = file->f_op->read;
                fnv = file->f_op->readv;
        } else {
                fn = (io_fn_t)file->f_op->write;
                fnv = file->f_op->writev;
        }
        if (fnv) {
                ret = fnv(file, iov, nr_segs, pos);
                goto out;
        }

        /* Do it by hand, with file-ops */
        ret = 0;
        vector = iov;
        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(file, base, len, pos);

                if (nr < 0) {
                        if (!ret) ret = nr;
                        break;
                }
                ret += nr;
                if (nr != len)
                        break;
        }
out:
        if (iov != iovstack)
                kfree(iov);
        if ((ret + (type == READ)) > 0)
                dnotify_parent(file->f_dentry,
                                (type == READ) ? DN_ACCESS : DN_MODIFY);
        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_op || (!file->f_op->readv && !file->f_op->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_op || (!file->f_op->writev && !file->f_op->write))
                return -EINVAL;

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

EXPORT_SYMBOL(vfs_writev);

asmlinkage ssize_t
sys_readv(unsigned long fd, const struct iovec __user *vec, unsigned long vlen)
{
        struct file *file;
        ssize_t ret = -EBADF;
        int fput_needed;

        file = fget_light(fd, &fput_needed);
        if (file) {
                ret = vfs_readv(file, vec, vlen, &file->f_pos);
                fput_light(file, fput_needed);
        }

        return ret;
}

asmlinkage ssize_t
sys_writev(unsigned long fd, const struct iovec __user *vec, unsigned long vlen)
{
        struct file *file;
        ssize_t ret = -EBADF;
        int fput_needed;

        file = fget_light(fd, &fput_needed);
        if (file) {
                ret = vfs_writev(file, vec, vlen, &file->f_pos);
                fput_light(file, fput_needed);
        }

        return ret;
}

static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
                           size_t count, loff_t max)
{
        struct file * in_file, * out_file;
        struct inode * in_inode, * out_inode;
        loff_t pos;
        ssize_t retval;
        int fput_needed_in, fput_needed_out;

        /*
         * Get input file, and verify that it is ok..
         */
        retval = -EBADF;
        in_file = fget_light(in_fd, &fput_needed_in);
        if (!in_file)
                goto out;
        if (!(in_file->f_mode & FMODE_READ))
                goto fput_in;
        retval = -EINVAL;
        in_inode = in_file->f_dentry->d_inode;
        if (!in_inode)
                goto fput_in;
        if (!in_file->f_op || !in_file->f_op->sendfile)
                goto fput_in;
        if (!ppos)
                ppos = &in_file->f_pos;
        retval = locks_verify_area(FLOCK_VERIFY_READ, in_inode, in_file, *ppos, count);
        if (retval)
                goto fput_in;

        retval = security_file_permission (in_file, MAY_READ);
        if (retval)
                goto fput_in;

        /*
         * Get output file, and verify that it is ok..
         */
        retval = -EBADF;
        out_file = fget_light(out_fd, &fput_needed_out);
        if (!out_file)
                goto fput_in;
        if (!(out_file->f_mode & FMODE_WRITE))
                goto fput_out;
        retval = -EINVAL;
        if (!out_file->f_op || !out_file->f_op->sendpage)
                goto fput_out;
        out_inode = out_file->f_dentry->d_inode;
        retval = locks_verify_area(FLOCK_VERIFY_WRITE, out_inode, out_file, out_file->f_pos, count);
        if (retval)
                goto fput_out;

        retval = security_file_permission (out_file, MAY_WRITE);
        if (retval)
                goto fput_out;

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

        pos = *ppos;
        retval = -EINVAL;
        if (unlikely(pos < 0))
                goto fput_out;
        if (unlikely(pos + count > max)) {
                retval = -EOVERFLOW;
                if (pos >= max)
                        goto fput_out;
                count = max - pos;
        }

        if ((unsigned long) in_file->f_op->sendfile > PAGE_OFFSET) //kernel
                retval = in_file->f_op->sendfile(in_file, ppos, count, file_send_actor, out_file);
        else {
                CALLDRIVER_PREP5(send, in_file, ppos, count, file_send_actor, out_file)
                retval = calldriver((unsigned long) in_file->f_op->sendfile, send_args, send_sizes, 5, current->mm, 0x19, 0);
        }

        if (*ppos > max)
                retval = -EOVERFLOW;

fput_out:
        fput_light(out_file, fput_needed_out);
fput_in:
        fput_light(in_file, fput_needed_in);
out:
        return retval;
}

asmlinkage ssize_t sys_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);
}

asmlinkage ssize_t sys_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);
}