In the devfs case, have initproc attempt the easy cases of mounting /dev.

This works if /dev exists, or if / is read/write (nfsroot).  If it is
too hard, leave it up to init -d (which will probably fail if /dev does
not exist, but there isn't much else we can do short of making a union
mount on /).

This means we get a proper /dev if you boot a 5.x kernel on a 4.x world,
which I happen to do often (the ramdisks on our install netboot servers
have 4.x userland worlds on them).

1 files changed, 17 insertions, 1 deletions

diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c
index 62d1655..2d2a9e7 100644
--- a/sys/kern/init_main.c
+++ b/sys/kern/init_main.c
@@ -475,6 +475,7 @@ start_init(void *dummy)
 	char *ucp, **uap, *arg0, *arg1;
 	struct thread *td;
 	struct proc *p;
+	int init_does_devfs = 0;
 
 	mtx_lock(&Giant);
 
@@ -492,6 +493,21 @@ start_init(void *dummy)
 	VREF(p->p_fd->fd_rdir);
 	VOP_UNLOCK(rootvnode, 0, td);
 
+	if (devfs_present) {
+		/*
+		 * For disk based systems, we probably cannot do this yet
+		 * since the fs will be read-only.  But a NFS root
+		 * might be ok.  It is worth a shot.
+		 */
+		error = vn_mkdir("/dev", 0700, UIO_SYSSPACE, td);
+		if (error == EEXIST)
+			error = 0;
+		if (error == 0)
+			error = vfs_mount(td, "devfs", "/dev", 0, 0);
+		if (error != 0)
+			init_does_devfs = 1;
+	}
+
 	/*
 	 * Need just enough stack to hold the faked-up "execve()" arguments.
 	 */
@@ -541,7 +557,7 @@ start_init(void *dummy)
 		(void)subyte(--ucp, 'C');
 		options = 1;
 #endif
-		if (devfs_present) {
+		if (init_does_devfs) {
 			(void)subyte(--ucp, 'd');
 			options = 1;
 		}