readdir.c

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/*
 *  linux/fs/readdir.c
 *
 *  Copyright (C) 1995  Linus Torvalds
 */

#include <linux/stddef.h>
#include <linux/kernel.h>
#include <linux/export.h>
#include <linux/time.h>
#include <linux/mm.h>
#include <linux/errno.h>
#include <linux/stat.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/dirent.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/unistd.h>

#include <asm/uaccess.h>

int vfs_readdir(struct file *file, filldir_t filler, void *buf)
{
    struct inode *inode = file->f_path.dentry->d_inode;
    int res = -ENOTDIR;
    if (!file->f_op || !file->f_op->readdir)
        goto out;

    res = security_file_permission(file, MAY_READ);
    if (res)
        goto out;

    res = mutex_lock_killable(&inode->i_mutex);
    if (res)
        goto out;

    res = -ENOENT;
    if (!IS_DEADDIR(inode)) {
        res = file->f_op->readdir(file, buf, filler);
        file_accessed(file);
    }
    mutex_unlock(&inode->i_mutex);
out:
    return res;
}

EXPORT_SYMBOL(vfs_readdir);

/*
 * Traditional linux readdir() handling..
 *
 * "count=1" is a special case, meaning that the buffer is one
 * dirent-structure in size and that the code can't handle more
 * anyway. Thus the special "fillonedir()" function for that
 * case (the low-level handlers don't need to care about this).
 */

#ifdef __ARCH_WANT_OLD_READDIR

struct old_linux_dirent {
    unsigned long   d_ino;
    unsigned long   d_offset;
    unsigned short  d_namlen;
    char        d_name[1];
};

struct readdir_callback {
    struct old_linux_dirent __user * dirent;
    int result;
};

static int fillonedir(void * __buf, const char * name, int namlen, loff_t offset,
              u64 ino, unsigned int d_type)
{
    struct readdir_callback * buf = (struct readdir_callback *) __buf;
    struct old_linux_dirent __user * dirent;
    unsigned long d_ino;

    if (buf->result)
        return -EINVAL;
    d_ino = ino;
    if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
        buf->result = -EOVERFLOW;
        return -EOVERFLOW;
    }
    buf->result++;
    dirent = buf->dirent;
    if (!access_ok(VERIFY_WRITE, dirent,
            (unsigned long)(dirent->d_name + namlen + 1) -
                (unsigned long)dirent))
        goto efault;
    if (    __put_user(d_ino, &dirent->d_ino) ||
        __put_user(offset, &dirent->d_offset) ||
        __put_user(namlen, &dirent->d_namlen) ||
        __copy_to_user(dirent->d_name, name, namlen) ||
        __put_user(0, dirent->d_name + namlen))
        goto efault;
    return 0;
efault:
    buf->result = -EFAULT;
    return -EFAULT;
}

SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
        struct old_linux_dirent __user *, dirent, unsigned int, count)
{
    int error;
    struct fd f = fdget(fd);
    struct readdir_callback buf;

    if (!f.file)
        return -EBADF;

    buf.result = 0;
    buf.dirent = dirent;

    error = vfs_readdir(f.file, fillonedir, &buf);
    if (buf.result)
        error = buf.result;

    fdput(f);
    return error;
}

#endif /* __ARCH_WANT_OLD_READDIR */

/*
 * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 * interface. 
 */
struct linux_dirent {
    unsigned long   d_ino;
    unsigned long   d_off;
    unsigned short  d_reclen;
    char        d_name[1];
};

struct getdents_callback {
    struct linux_dirent __user * current_dir;
    struct linux_dirent __user * previous;
    int count;
    int error;
};

static int filldir(void * __buf, const char * name, int namlen, loff_t offset,
           u64 ino, unsigned int d_type)
{
    struct linux_dirent __user * dirent;
    struct getdents_callback * buf = (struct getdents_callback *) __buf;
    unsigned long d_ino;
    int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
        sizeof(long));

    buf->error = -EINVAL;   /* only used if we fail.. */
    if (reclen > buf->count)
        return -EINVAL;
    d_ino = ino;
    if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
        buf->error = -EOVERFLOW;
        return -EOVERFLOW;
    }
    dirent = buf->previous;
    if (dirent) {
        if (__put_user(offset, &dirent->d_off))
            goto efault;
    }
    dirent = buf->current_dir;
    if (__put_user(d_ino, &dirent->d_ino))
        goto efault;
    if (__put_user(reclen, &dirent->d_reclen))
        goto efault;
    if (copy_to_user(dirent->d_name, name, namlen))
        goto efault;
    if (__put_user(0, dirent->d_name + namlen))
        goto efault;
    if (__put_user(d_type, (char __user *) dirent + reclen - 1))
        goto efault;
    buf->previous = dirent;
    dirent = (void __user *)dirent + reclen;
    buf->current_dir = dirent;
    buf->count -= reclen;
    return 0;
efault:
    buf->error = -EFAULT;
    return -EFAULT;
}

SYSCALL_DEFINE3(getdents, unsigned int, fd,
        struct linux_dirent __user *, dirent, unsigned int, count)
{
    struct fd f;
    struct linux_dirent __user * lastdirent;
    struct getdents_callback buf;
    int error;

    if (!access_ok(VERIFY_WRITE, dirent, count))
        return -EFAULT;

    f = fdget(fd);
    if (!f.file)
        return -EBADF;

    buf.current_dir = dirent;
    buf.previous = NULL;
    buf.count = count;
    buf.error = 0;

    error = vfs_readdir(f.file, filldir, &buf);
    if (error >= 0)
        error = buf.error;
    lastdirent = buf.previous;
    if (lastdirent) {
        if (put_user(f.file->f_pos, &lastdirent->d_off))
            error = -EFAULT;
        else
            error = count - buf.count;
    }
    fdput(f);
    return error;
}

struct getdents_callback64 {
    struct linux_dirent64 __user * current_dir;
    struct linux_dirent64 __user * previous;
    int count;
    int error;
};

static int filldir64(void * __buf, const char * name, int namlen, loff_t offset,
             u64 ino, unsigned int d_type)
{
    struct linux_dirent64 __user *dirent;
    struct getdents_callback64 * buf = (struct getdents_callback64 *) __buf;
    int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
        sizeof(u64));

    buf->error = -EINVAL;   /* only used if we fail.. */
    if (reclen > buf->count)
        return -EINVAL;
    dirent = buf->previous;
    if (dirent) {
        if (__put_user(offset, &dirent->d_off))
            goto efault;
    }
    dirent = buf->current_dir;
    if (__put_user(ino, &dirent->d_ino))
        goto efault;
    if (__put_user(0, &dirent->d_off))
        goto efault;
    if (__put_user(reclen, &dirent->d_reclen))
        goto efault;
    if (__put_user(d_type, &dirent->d_type))
        goto efault;
    if (copy_to_user(dirent->d_name, name, namlen))
        goto efault;
    if (__put_user(0, dirent->d_name + namlen))
        goto efault;
    buf->previous = dirent;
    dirent = (void __user *)dirent + reclen;
    buf->current_dir = dirent;
    buf->count -= reclen;
    return 0;
efault:
    buf->error = -EFAULT;
    return -EFAULT;
}

SYSCALL_DEFINE3(getdents64, unsigned int, fd,
        struct linux_dirent64 __user *, dirent, unsigned int, count)
{
    struct fd f;
    struct linux_dirent64 __user * lastdirent;
    struct getdents_callback64 buf;
    int error;

    if (!access_ok(VERIFY_WRITE, dirent, count))
        return -EFAULT;

    f = fdget(fd);
    if (!f.file)
        return -EBADF;

    buf.current_dir = dirent;
    buf.previous = NULL;
    buf.count = count;
    buf.error = 0;

    error = vfs_readdir(f.file, filldir64, &buf);
    if (error >= 0)
        error = buf.error;
    lastdirent = buf.previous;
    if (lastdirent) {
        typeof(lastdirent->d_off) d_off = f.file->f_pos;
        if (__put_user(d_off, &lastdirent->d_off))
            error = -EFAULT;
        else
            error = count - buf.count;
    }
    fdput(f);
    return error;
}