kern_descrip.c

很好的一个嵌入式linux平台下的bootloader

	int lim, last, nfiles;
	struct file **newofile;
	char *newofileflags;

	/*
	 * Search for a free descriptor starting at the higher
	 * of want or fd_freefile.  If that fails, consider
	 * expanding the ofile array.
	 */
#ifdef PROM
	lim = NDFILE;
#else
	lim = p->p_rlimit[RLIMIT_OFILE].rlim_cur;
#endif
	for (;;) {
		last = min(fdp->fd_nfiles, lim);
		if ((i = want) < fdp->fd_freefile)
			i = fdp->fd_freefile;
		for (; i < last; i++) {
			if (fdp->fd_ofiles[i] == NULL) {
				fdp->fd_ofileflags[i] = 0;
				if (i > fdp->fd_lastfile)
					fdp->fd_lastfile = i;
				if (want <= fdp->fd_freefile)
					fdp->fd_freefile = i;
				*result = i;
				return (0);
			}
		}

		/*
		 * No space in current array.  Expand?
		 */
#ifdef PROM
		return (EMFILE);
#else
		if (fdp->fd_nfiles >= lim)
			return (EMFILE);
		if (fdp->fd_nfiles < NDEXTENT)
			nfiles = NDEXTENT;
		else
			nfiles = 2 * fdp->fd_nfiles;
		MALLOC(newofile, struct file **, nfiles * OFILESIZE,
		    M_FILEDESC, M_WAITOK);
		newofileflags = (char *) &newofile[nfiles];
		/*
		 * Copy the existing ofile and ofileflags arrays
		 * and zero the new portion of each array.
		 */
		bcopy(fdp->fd_ofiles, newofile,
			(i = sizeof(struct file *) * fdp->fd_nfiles));
		bzero((char *)newofile + i, nfiles * sizeof(struct file *) - i);
		bcopy(fdp->fd_ofileflags, newofileflags,
			(i = sizeof(char) * fdp->fd_nfiles));
		bzero(newofileflags + i, nfiles * sizeof(char) - i);
		if (fdp->fd_nfiles > NDFILE)
			FREE(fdp->fd_ofiles, M_FILEDESC);
		fdp->fd_ofiles = newofile;
		fdp->fd_ofileflags = newofileflags;
		fdp->fd_nfiles = nfiles;
		fdexpand++;
#endif
	}
}

/*
 * Check to see whether n user file descriptors
 * are available to the process p.
 */
fdavail(p, n)
	struct proc *p;
	register int n;
{
	register struct filedesc *fdp = p->p_fd;
	register struct file **fpp;
	register int i;

#ifdef PROM
	if ((i = NDFILE - fdp->fd_nfiles) > 0 &&
	    (n -= i) <= 0)
		return (1);
#else
	if ((i = p->p_rlimit[RLIMIT_OFILE].rlim_cur - fdp->fd_nfiles) > 0 &&
	    (n -= i) <= 0)
		return (1);
#endif
	fpp = &fdp->fd_ofiles[fdp->fd_freefile];
	for (i = fdp->fd_nfiles - fdp->fd_freefile; --i >= 0; fpp++)
		if (*fpp == NULL && --n <= 0)
			return (1);
	return (0);
}

/*
 * Create a new open file structure and allocate
 * a file decriptor for the process that refers to it.
 */
falloc(p, resultfp, resultfd)
	register struct proc *p;
	struct file **resultfp;
	int *resultfd;
{
	register struct file *fp, *fq, **fpp;
	int error, i;

	if (error = fdalloc(p, 0, &i))
		return (error);
	if (nfiles >= maxfiles) {
		tablefull("file");
		return (ENFILE);
	}
	/*
	 * Allocate a new file descriptor.
	 * If the process has file descriptor zero open, add to the list
	 * of open files at that point, otherwise put it at the front of
	 * the list of open files.
	 */
	nfiles++;
	MALLOC(fp, struct file *, sizeof(struct file), M_FILE, M_WAITOK);
	if (fq = p->p_fd->fd_ofiles[0])
		fpp = &fq->f_filef;
	else
		fpp = &filehead;
	p->p_fd->fd_ofiles[i] = fp;
	if (fq = *fpp)
		fq->f_fileb = &fp->f_filef;
	fp->f_filef = fq;
	fp->f_fileb = fpp;
	*fpp = fp;
	fp->f_count = 1;
	fp->f_msgcount = 0;
	fp->f_offset = 0;
	fp->f_cred = p->p_ucred;
	crhold(fp->f_cred);
	if (resultfp)
		*resultfp = fp;
	if (resultfd)
		*resultfd = i;
	return (0);
}

/*
 * Free a file descriptor.
 */
ffree(fp)
	register struct file *fp;
{
	register struct file *fq;

	if (fq = fp->f_filef)
		fq->f_fileb = fp->f_fileb;
	*fp->f_fileb = fq;
	crfree(fp->f_cred);
#ifdef DIAGNOSTIC
	fp->f_filef = NULL;
	fp->f_fileb = NULL;
	fp->f_count = 0;
#endif
	nfiles--;
	FREE(fp, M_FILE);
}

/*
 * Copy a filedesc structure.
 */
struct filedesc *
fdcopy(p)
	struct proc *p;
{
	register struct filedesc *newfdp, *fdp = p->p_fd;
	register struct file **fpp;
	register int i;

	MALLOC(newfdp, struct filedesc *, sizeof(struct filedesc0),
	    M_FILEDESC, M_WAITOK);
	bcopy(fdp, newfdp, sizeof(struct filedesc));
#ifndef PROM
	VREF(newfdp->fd_cdir);
	if (newfdp->fd_rdir)
		VREF(newfdp->fd_rdir);
#endif
	newfdp->fd_refcnt = 1;

	/*
	 * If the number of open files fits in the internal arrays
	 * of the open file structure, use them, otherwise allocate
	 * additional memory for the number of descriptors currently
	 * in use.
	 */
	if (newfdp->fd_lastfile < NDFILE) {
		newfdp->fd_ofiles = ((struct filedesc0 *) newfdp)->fd_dfiles;
		newfdp->fd_ofileflags =
		    ((struct filedesc0 *) newfdp)->fd_dfileflags;
		i = NDFILE;
	} else {
#ifdef PROM
	    	panic ("fdcopy");
#else
		/*
		 * Compute the smallest multiple of NDEXTENT needed
		 * for the file descriptors currently in use,
		 * allowing the table to shrink.
		 */
		i = newfdp->fd_nfiles;
		while (i > 2 * NDEXTENT && i >= newfdp->fd_lastfile * 2)
			i /= 2;
		MALLOC(newfdp->fd_ofiles, struct file **, i * OFILESIZE,
		    M_FILEDESC, M_WAITOK);
		newfdp->fd_ofileflags = (char *) &newfdp->fd_ofiles[i];
#endif
	}
	newfdp->fd_nfiles = i;
	bcopy(fdp->fd_ofiles, newfdp->fd_ofiles, i * sizeof(struct file **));
	bcopy(fdp->fd_ofileflags, newfdp->fd_ofileflags, i * sizeof(char));
	fpp = newfdp->fd_ofiles;
	for (i = newfdp->fd_lastfile; i-- >= 0; fpp++)
		if (*fpp != NULL)
			(*fpp)->f_count++;
	return (newfdp);
}


/*
 * Release a filedesc structure.
 */
void
fdfree(p)
	struct proc *p;
{
	register struct filedesc *fdp = p->p_fd;
	struct file **fpp;
	register int i;

	if (--fdp->fd_refcnt > 0)
		return;
	fpp = fdp->fd_ofiles;
	for (i = fdp->fd_lastfile; i-- >= 0; fpp++)
		if (*fpp)
			(void) closef(*fpp, p);
	if (fdp->fd_nfiles > NDFILE)
		FREE(fdp->fd_ofiles, M_FILEDESC);
#ifndef PROM
	vrele(fdp->fd_cdir);
	if (fdp->fd_rdir)
		vrele(fdp->fd_rdir);
#endif
	FREE(fdp, M_FILEDESC);
}

/*
 * Internal form of close.
 * Decrement reference count on file structure.
 */
closef(fp, p)
	register struct file *fp;
	register struct proc *p;
{
	struct vnode *vp;
	struct flock lf;
	int error;

	if (fp == NULL)
		return (0);
#ifndef PROM
	/*
	 * POSIX record locking dictates that any close releases ALL
	 * locks owned by this process.  This is handled by setting
	 * a flag in the unlock to free ONLY locks obeying POSIX
	 * semantics, and not to free BSD-style file locks.
	 */
	if ((p->p_flag & SADVLCK) && fp->f_type == DTYPE_VNODE) {
		lf.l_whence = SEEK_SET;
		lf.l_start = 0;
		lf.l_len = 0;
		lf.l_type = F_UNLCK;
		vp = (struct vnode *)fp->f_data;
		(void) VOP_ADVLOCK(vp, (caddr_t)p, F_UNLCK, &lf, F_POSIX);
	}
#endif
	if (--fp->f_count > 0)
		return (0);
	if (fp->f_count < 0)
		panic("closef: count < 0");
#ifndef PROM
	if ((fp->f_flag & FHASLOCK) && fp->f_type == DTYPE_VNODE) {
		lf.l_whence = SEEK_SET;
		lf.l_start = 0;
		lf.l_len = 0;
		lf.l_type = F_UNLCK;
		vp = (struct vnode *)fp->f_data;
		(void) VOP_ADVLOCK(vp, (caddr_t)fp, F_UNLCK, &lf, F_FLOCK);
	}
#endif
	error = (*fp->f_ops->fo_close)(fp, p);
	ffree(fp);
	return (error);
}

#ifndef PROM
/*
 * Apply an advisory lock on a file descriptor.
 *
 * Just attempt to get a record lock of the requested type on
 * the entire file (l_whence = SEEK_SET, l_start = 0, l_len = 0).
 */

/* ARGSUSED */
flock(p, uap, retval)
	struct proc *p;
	register struct args {
		int	fd;
		int	how;
	} *uap;
	int *retval;
{
	register struct filedesc *fdp = p->p_fd;
	register struct file *fp;
	struct vnode *vp;
	struct flock lf;
	int error;

	if ((unsigned)uap->fd >= fdp->fd_nfiles ||
	    (fp = fdp->fd_ofiles[uap->fd]) == NULL)
		return (EBADF);
	if (fp->f_type != DTYPE_VNODE)
		return (EOPNOTSUPP);
	vp = (struct vnode *)fp->f_data;
	lf.l_whence = SEEK_SET;
	lf.l_start = 0;
	lf.l_len = 0;
	if (uap->how & LOCK_UN) {
		lf.l_type = F_UNLCK;
		fp->f_flag &= ~FHASLOCK;
		return (VOP_ADVLOCK(vp, (caddr_t)fp, F_UNLCK, &lf, F_FLOCK));
	}
	if (uap->how & LOCK_EX)
		lf.l_type = F_WRLCK;
	else if (uap->how & LOCK_SH)
		lf.l_type = F_RDLCK;
	else
		return (EBADF);
	fp->f_flag |= FHASLOCK;
	if (uap->how & LOCK_NB)
		return (VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, F_FLOCK));
	return (VOP_ADVLOCK(vp, (caddr_t)fp, F_SETLK, &lf, F_FLOCK|F_WAIT));
}

/*
 * File Descriptor pseudo-device driver (/dev/fd/).
 *
 * Opening minor device N dup()s the file (if any) connected to file
 * descriptor N belonging to the calling process.  Note that this driver
 * consists of only the ``open()'' routine, because all subsequent
 * references to this file will be direct to the other driver.
 */
/* ARGSUSED */
fdopen(dev, mode, type)
	dev_t dev;
	int mode, type;
{

	/*
	 * XXX Kludge: set curproc->p_dupfd to contain the value of the
	 * the file descriptor being sought for duplication. The error 
	 * return ensures that the vnode for this device will be released
	 * by vn_open. Open will detect this special error and take the
	 * actions in dupfdopen below. Other callers of vn_open or VOP_OPEN
	 * will simply report the error.
	 */
	curproc->p_dupfd = minor(dev);		/* XXX */
	return (ENODEV);
}

/*
 * Duplicate the specified descriptor to a free descriptor.
 */
dupfdopen(fdp, indx, dfd, mode)
	register struct filedesc *fdp;
	register int indx, dfd;
	int mode;
{
	register struct file *wfp;
	struct file *fp;
	
	/*
	 * If the to-be-dup'd fd number is greater than the allowed number
	 * of file descriptors, or the fd to be dup'd has already been
	 * closed, reject.  Note, check for new == old is necessary as
	 * falloc could allocate an already closed to-be-dup'd descriptor
	 * as the new descriptor.
	 */
	fp = fdp->fd_ofiles[indx];
	if ((u_int)dfd >= fdp->fd_nfiles ||
	    (wfp = fdp->fd_ofiles[dfd]) == NULL || fp == wfp)
		return (EBADF);

	/*
	 * Check that the mode the file is being opened for is a subset 
	 * of the mode of the existing descriptor.
	 */
	if (((mode & (FREAD|FWRITE)) | wfp->f_flag) != wfp->f_flag)
		return (EACCES);
	fdp->fd_ofiles[indx] = wfp;
	fdp->fd_ofileflags[indx] = fdp->fd_ofileflags[dfd];
	wfp->f_count++;
	if (indx > fdp->fd_lastfile)
		fdp->fd_lastfile = indx;
	return (0);
}
#endif /* !PROM */