Part I: Update extended attribute API and ABI:

o Modify the system call syntax for extattr_{get,set}_{fd,file}() so
  as not to use the scatter gather API (which appeared not to be used
  by any consumers, and be less portable), rather, accepts 'data'
  and 'nbytes' in the style of other simple read/write interfaces.
  This changes the API and ABI.

o Modify system call semantics so that extattr_get_{fd,file}() return
  a size_t.  When performing a read, the number of bytes read will
  be returned, unless the data pointer is NULL, in which case the
  number of bytes of data are returned.  This changes the API only.

o Modify the VOP_GETEXTATTR() vnode operation to accept a *size_t
  argument so as to return the size, if desirable.  If set to NULL,
  the size will not be returned.

o Update various filesystems (pseodofs, ufs) to DTRT.

These changes should make extended attributes more useful and more
portable.  More commits to rebuild the system call files, as well
as update userland utilities to follow.

Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, NAI Labs

1 files changed, 60 insertions, 81 deletions

diff --git a/sys/kern/vfs_extattr.c b/sys/kern/vfs_extattr.c
index 0500ddeb4b30..67cec3e21942 100644
--- a/sys/kern/vfs_extattr.c
+++ b/sys/kern/vfs_extattr.c
@@ -3993,67 +3993,52 @@ extattrctl(td, uap)
 	return (error);
 }
 
-/*
- * extattr_set_vp(): Set a named extended attribute on a file or directory
+/*-
+ * Set a named extended attribute on a file or directory
  * 
  * Arguments: unlocked vnode "vp", attribute namespace "attrnamespace",
- *            kernelspace string pointer "attrname",
- *            userspace iovec array pointer "iovp", unsigned int iovcnt
- *            proc "p"
+ *            kernelspace string pointer "attrname", userspace buffer
+ *            pointer "data", buffer length "nbytes", thread "td".
  * Returns: 0 on success, an error number otherwise
  * Locks: none
  * References: vp must be a valid reference for the duration of the call
  */
 static int
 extattr_set_vp(struct vnode *vp, int attrnamespace, const char *attrname,
-    struct iovec *iovp, unsigned iovcnt, struct thread *td)
+    const void *data, size_t nbytes, struct thread *td)
 {
 	struct mount *mp;
 	struct uio auio;
-	struct iovec *iov, *needfree = NULL, aiov[UIO_SMALLIOV];
-	u_int iovlen, cnt;
-	int error, i;
+	struct iovec aiov;
+	ssize_t cnt;
+	int error;
 
 	if ((error = vn_start_write(vp, &mp, V_WAIT | PCATCH)) != 0)
 		return (error);
 	VOP_LEASE(vp, td, td->td_proc->p_ucred, LEASE_WRITE);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
 
-	iovlen = iovcnt * sizeof(struct iovec);
-	if (iovcnt > UIO_SMALLIOV) {
-		if (iovcnt > UIO_MAXIOV) {
-			error = EINVAL;
-			goto done;
-		}
-		MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
-		needfree = iov;
-	} else
-		iov = aiov;
-	auio.uio_iov = iov;
-	auio.uio_iovcnt = iovcnt;
-	auio.uio_rw = UIO_WRITE;
-	auio.uio_segflg = UIO_USERSPACE;
-	auio.uio_td = td;
+	aiov.iov_base = data;
+	aiov.iov_len = nbytes;
+	auio.uio_iov = &aiov;
+	auio.uio_iovcnt = 1;
 	auio.uio_offset = 0;
-	if ((error = copyin((caddr_t)iovp, (caddr_t)iov, iovlen)))
+	if (nbytes > INT_MAX) {
+		error = EINVAL;
 		goto done;
-	auio.uio_resid = 0;
-	for (i = 0; i < iovcnt; i++) {
-		if (iov->iov_len > INT_MAX - auio.uio_resid) {
-			error = EINVAL;
-			goto done;
-		}
-		auio.uio_resid += iov->iov_len;
-		iov++;
 	}
-	cnt = auio.uio_resid;
+	auio.uio_resid = nbytes;
+	auio.uio_rw = UIO_WRITE;
+	auio.uio_segflg = UIO_USERSPACE;
+	auio.uio_td = td;
+	cnt = nbytes;
+
 	error = VOP_SETEXTATTR(vp, attrnamespace, attrname, &auio,
 	    td->td_proc->p_ucred, td);
 	cnt -= auio.uio_resid;
 	td->td_retval[0] = cnt;
+
 done:
-	if (needfree)
-		FREE(needfree, M_IOV);
 	VOP_UNLOCK(vp, 0, td);
 	vn_finished_write(mp);
 	return (error);
@@ -4079,7 +4064,7 @@ extattr_set_file(td, uap)
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 
 	error = extattr_set_vp(nd.ni_vp, SCARG(uap, attrnamespace), attrname,
-	    SCARG(uap, iovp), SCARG(uap, iovcnt), td);
+	    SCARG(uap, data), SCARG(uap, nbytes), td);
 
 	vrele(nd.ni_vp);
 	return (error);
@@ -4103,71 +4088,65 @@ extattr_set_fd(td, uap)
 		return (error);
 
 	error = extattr_set_vp((struct vnode *)fp->f_data,
-	    SCARG(uap, attrnamespace), attrname, SCARG(uap, iovp),
-	    SCARG(uap, iovcnt), td);
+	    SCARG(uap, attrnamespace), attrname, SCARG(uap, data),
+	    SCARG(uap, nbytes), td);
 	fdrop(fp, td);
 
 	return (error);
 }
 
-/*
- * extattr_get_vp(): Get a named extended attribute on a file or directory
+/*-
+ * Get a named extended attribute on a file or directory
  * 
  * Arguments: unlocked vnode "vp", attribute namespace "attrnamespace",
- *            kernelspace string pointer "attrname",
- *            userspace iovec array pointer "iovp", unsigned int iovcnt,
- *            proc "p"
+ *            kernelspace string pointer "attrname", userspace buffer
+ *            pointer "data", buffer length "nbytes", thread "td".
  * Returns: 0 on success, an error number otherwise
  * Locks: none
  * References: vp must be a valid reference for the duration of the call
  */
 static int
 extattr_get_vp(struct vnode *vp, int attrnamespace, const char *attrname,
-    struct iovec *iovp, unsigned iovcnt, struct thread *td)
+    void *data, size_t nbytes, struct thread *td)
 {
 	struct uio auio;
-	struct iovec *iov, *needfree = NULL, aiov[UIO_SMALLIOV];
-	u_int iovlen, cnt;
-	int error, i;
+	struct iovec aiov;
+	ssize_t cnt;
+	size_t size;
+	int error;
 
 	VOP_LEASE(vp, td, td->td_proc->p_ucred, LEASE_READ);
 	vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
 
-	iovlen = iovcnt * sizeof (struct iovec);
-	if (iovcnt > UIO_SMALLIOV) {
-		if (iovcnt > UIO_MAXIOV) {
-			error = EINVAL;
-			goto done;
-		}
-		MALLOC(iov, struct iovec *, iovlen, M_IOV, M_WAITOK);
-		needfree = iov;
-	} else
-		iov = aiov;
-	auio.uio_iov = iov;
-	auio.uio_iovcnt = iovcnt;
-	auio.uio_rw = UIO_READ;
-	auio.uio_segflg = UIO_USERSPACE;
-	auio.uio_td = td;
-	auio.uio_offset = 0;
-	if ((error = copyin((caddr_t)iovp, (caddr_t)iov, iovlen)))
-		goto done;
-	auio.uio_resid = 0;
-	for (i = 0; i < iovcnt; i++) {
-		if (iov->iov_len > INT_MAX - auio.uio_resid) {
+	/*
+	 * Slightly unusual semantics: if the user provides a NULL data
+	 * pointer, they don't want to receive the data, just the
+	 * maximum read length.
+	 */
+	if (data != NULL) {
+		aiov.iov_base = data;
+		aiov.iov_len = nbytes;
+		auio.uio_iov = &aiov;
+		auio.uio_offset = 0;
+		if (nbytes > INT_MAX) {
 			error = EINVAL;
 			goto done;
 		}
-		auio.uio_resid += iov->iov_len;
-		iov++;
+		auio.uio_resid = nbytes;
+		auio.uio_rw = UIO_READ;
+		auio.uio_segflg = UIO_USERSPACE;
+		auio.uio_td = td;
+		cnt = nbytes;
+		error = VOP_GETEXTATTR(vp, attrnamespace, attrname, &auio,
+		    NULL, td->td_proc->p_ucred, td);
+		cnt -= auio.uio_resid;
+		td->td_retval[0] = cnt;
+	} else {
+		error = VOP_GETEXTATTR(vp, attrnamespace, attrname, NULL,
+		    &size, td->td_proc->p_ucred, td);
+		td->td_retval[0] = size;
 	}
-	cnt = auio.uio_resid;
-	error = VOP_GETEXTATTR(vp, attrnamespace, attrname, &auio,
-	    td->td_proc->p_ucred, td);
-	cnt -= auio.uio_resid;
-	td->td_retval[0] = cnt;
 done:
-	if (needfree)
-		FREE(needfree, M_IOV);
 	VOP_UNLOCK(vp, 0, td);
 	return (error);
 }
@@ -4192,7 +4171,7 @@ extattr_get_file(td, uap)
 	NDFREE(&nd, NDF_ONLY_PNBUF);
 
 	error = extattr_get_vp(nd.ni_vp, SCARG(uap, attrnamespace), attrname,
-	    SCARG(uap, iovp), SCARG(uap, iovcnt), td);
+	    SCARG(uap, data), SCARG(uap, nbytes), td);
 
 	vrele(nd.ni_vp);
 	return (error);
@@ -4216,8 +4195,8 @@ extattr_get_fd(td, uap)
 		return (error);
 
 	error = extattr_get_vp((struct vnode *)fp->f_data,
-	    SCARG(uap, attrnamespace), attrname, SCARG(uap, iovp),
-	    SCARG(uap, iovcnt), td);
+	    SCARG(uap, attrnamespace), attrname, SCARG(uap, data),
+	    SCARG(uap, nbytes), td);
 
 	fdrop(fp, td);
 	return (error);