Add a -o mountprog parameter to mount which explicitly allows

an alternative program to be used for mounting a file system.
Ideally, all file systems
should be converted to pass string arguments to nmount(), so that
/sbin/mount can handle them.  However, certain file systems such as FUSE have
not done this, and want to have their own userland mount programs.

For example, to mount an NTFS file system with the FUSE NTFS driver:

mount -t ntfs -o mountprog=/usr/local/bin/ntfs-3g /dev/acd0 /mnt

or via an fstab entry:

/dev/acd0  /mnt  ntfs    ro,noauto,mountprog=/usr/local/bin/ntfs-3g       0       0

PR:	120784
Requested by: Dominic Fandrey

2 files changed, 39 insertions, 4 deletions

diff --git a/sbin/mount/mount.8 b/sbin/mount/mount.8
index 4c55df8..7635d74 100644
--- a/sbin/mount/mount.8
+++ b/sbin/mount/mount.8
@@ -163,6 +163,15 @@ is run with the
 flag but without the
 .Fl l
 flag.
+.It Cm mountprog Ns = Ns Aq Ar program
+Force
+.Nm
+to use the specified program to mount the file system, instead of calling
+.Xr nmount 2
+directly.  For example:
+.Bd -literal
+mount -t foofs -o mountprog=/mydir/fooprog /dev/acd0 /mnt
+.Ed
 .It Cm multilabel
 Enable multi-label Mandatory Access Control, or MAC, on the specified file
 system.
diff --git a/sbin/mount/mount.c b/sbin/mount/mount.c
index 66b9c13..e11c1c2 100644
--- a/sbin/mount/mount.c
+++ b/sbin/mount/mount.c
@@ -129,6 +129,8 @@ remountable_fs_names[] = {
 static const char userquotaeq[] = "userquota=";
 static const char groupquotaeq[] = "groupquota=";
 
+static char *mountprog = NULL;
+
 static int
 use_mountprog(const char *vfstype)
 {
@@ -143,6 +145,9 @@ use_mountprog(const char *vfstype)
 	NULL
 	};
 
+	if (mountprog != NULL)
+		return (1);
+
 	for (i = 0; fs[i] != NULL; ++i) {
 		if (strcmp(vfstype, fs[i]) == 0)
 			return (1);
@@ -165,8 +170,10 @@ exec_mountprog(const char *name, const char *execname, char *const argv[])
 		/* Go find an executable. */
 		execvP(execname, _PATH_SYSPATH, argv);
 		if (errno == ENOENT) {
-			warn("exec %s not found in %s", execname,
-			    _PATH_SYSPATH);
+			warn("exec %s not found", execname);
+			if (execname[0] != '/') {
+				warnx("in path: %s", _PATH_SYSPATH);
+			}
 		}
 		exit(1);
 	default:				/* Parent. */
@@ -558,13 +565,16 @@ mountfs(const char *vfstype, const char *spec, const char *name, int flags,
 	mnt_argv.c = -1;
 	append_arg(&mnt_argv, execname);
 	mangle(optbuf, &mnt_argv);
+	if (mountprog != NULL)
+		strcpy(execname, mountprog);
+
 	append_arg(&mnt_argv, strdup(spec));
 	append_arg(&mnt_argv, strdup(name));
 	append_arg(&mnt_argv, NULL);
 
 	if (debug) {
 		if (use_mountprog(vfstype))
-			printf("exec: mount_%s", vfstype);
+			printf("exec: %s", execname);
 		else
 			printf("mount -t %s", vfstype);
 		for (i = 1; i < mnt_argv.c; i++)
@@ -681,7 +691,7 @@ catopt(char *s0, const char *s1)
 void
 mangle(char *options, struct cpa *a)
 {
-	char *p, *s;
+	char *p, *s, *val;
 
 	for (s = options; (p = strsep(&s, ",")) != NULL;)
 		if (*p != '\0') {
@@ -703,6 +713,22 @@ mangle(char *options, struct cpa *a)
 				 * before mountd starts.
 				 */
 				continue;
+			} else if (strncmp(p, "mountprog", 9) == 0) {
+				/*
+				 * "mountprog" is used to force the use of
+				 * userland mount programs.
+				 */
+				val = strchr(p, '=');
+                        	if (val != NULL) {
+                                	++val;
+					if (*val != '\0')
+						mountprog = strdup(val);
+				}
+
+				if (mountprog == NULL) {
+					errx(1, "Need value for -o mountprog");
+				}
+				continue;
 			} else if (strcmp(p, "userquota") == 0) {
 				continue;
 			} else if (strncmp(p, userquotaeq,