For nmount(), allow a text string error message to be propagated back

to user-space if a parameter named "errmsg" is passed into the iovec.
Used in conjunction with vfs_mount_error(), more useful error messages
than errno can be passed back to userspace when mounting a filesystem
fails.

Discussed with:		phk, pjd

1 files changed, 37 insertions, 2 deletions

diff --git a/sys/kern/vfs_mount.c b/sys/kern/vfs_mount.c
index 508fd7b..449231f 100644
--- a/sys/kern/vfs_mount.c
+++ b/sys/kern/vfs_mount.c
@@ -390,6 +390,18 @@ nmount(td, uap)
 		iov++;
 	}
 	error = vfs_donmount(td, uap->flags, auio);
+
+	/* copyout the errmsg */
+	for (i = 0; (error != 0) && (i < iovcnt); i += 2) {
+		const char *name = (const char *)auio->uio_iov[i].iov_base;
+		if (!strcmp(name, "errmsg")) {
+			copyout(auio->uio_iov[i+1].iov_base,
+			    uap->iovp[i+1].iov_base, uap->iovp[i+1].iov_len);
+			
+			break;
+		}
+	}
+
 	free(auio, M_IOV);
 	return (error);
 }
@@ -464,8 +476,15 @@ static int
 vfs_donmount(struct thread *td, int fsflags, struct uio *fsoptions)
 {
 	struct vfsoptlist *optlist;
+	struct iovec *iov_errmsg = NULL;
 	char *fstype, *fspath;
 	int error, fstypelen, fspathlen;
+	int i;
+
+	for (i = 0; i < fsoptions->uio_iovcnt; i += 2) {
+		if (!strcmp((char *)fsoptions->uio_iov[i].iov_base, "errmsg"))
+			iov_errmsg = &fsoptions->uio_iov[i+1];
+	}
 
 	error = vfs_buildopts(fsoptions, &optlist);
 	if (error)
@@ -480,12 +499,18 @@ vfs_donmount(struct thread *td, int fsflags, struct uio *fsoptions)
 	error = vfs_getopt(optlist, "fstype", (void **)&fstype, &fstypelen);
 	if (error || fstype[fstypelen - 1] != '\0') {
 		error = EINVAL;
+		if (iov_errmsg)
+			strncpy((char *)iov_errmsg->iov_base, "Invalid fstype",
+			    iov_errmsg->iov_len);
 		goto bail;
 	}
 	fspathlen = 0;
 	error = vfs_getopt(optlist, "fspath", (void **)&fspath, &fspathlen);
 	if (error || fspath[fspathlen - 1] != '\0') {
 		error = EINVAL;
+		if (iov_errmsg != NULL)
+			strncpy((char *)iov_errmsg->iov_base, "Invalid fspath",
+			    iov_errmsg->iov_len);
 		goto bail;
 	}
 
@@ -503,6 +528,17 @@ vfs_donmount(struct thread *td, int fsflags, struct uio *fsoptions)
 	error = vfs_domount(td, fstype, fspath, fsflags, optlist);
 	mtx_unlock(&Giant);
 bail:
+	if (error && iov_errmsg != NULL) {
+		/* save the errmsg */
+		char *errmsg;
+		int len, ret;
+		ret = vfs_getopt(optlist, "errmsg", (void **)&errmsg, &len);  
+		if(ret == 0 && len > 0) 
+			strncpy((char *)iov_errmsg->iov_base, errmsg,
+			    iov_errmsg->iov_len);
+		
+	}
+	
 	if (error)
 		vfs_freeopts(optlist);
 	return (error);
@@ -1195,9 +1231,8 @@ vfs_mount_error(struct mount *mp, const char *fmt, ...)
 	char *errmsg;
 
 	error = vfs_getopt(moptlist, "errmsg", (void **)&errmsg, &len);
-	if (error || errmsg == NULL || len <= 0) {
+	if (error || errmsg == NULL || len <= 0)
 		return;
-	}
 
 	va_start(ap, fmt);
 	vsnprintf(errmsg, (size_t)len, fmt, ap);