zfs boot: export boot/primary pool and vdev guid all the way to kenv

This is work in progress to for znextboot and it also provides
some convenient infrastructure.

MFC after:	20 days

2 files changed, 30 insertions, 0 deletions

diff --git a/sys/boot/zfs/libzfs.h b/sys/boot/zfs/libzfs.h
index 92611db..6834f8b 100644
--- a/sys/boot/zfs/libzfs.h
+++ b/sys/boot/zfs/libzfs.h
@@ -53,6 +53,8 @@ struct zfs_boot_args
     uint32_t		reserved;
     uint64_t		pool;
     uint64_t		root;
+    uint64_t		primary_pool;
+    uint64_t		primary_vdev;
 };
 
 int	zfs_parsedev(struct zfs_devdesc *dev, const char *devspec,
diff --git a/sys/boot/zfs/zfsimpl.c b/sys/boot/zfs/zfsimpl.c
index 182bd83..1a82fe6 100644
--- a/sys/boot/zfs/zfsimpl.c
+++ b/sys/boot/zfs/zfsimpl.c
@@ -706,6 +706,34 @@ spa_find_by_name(const char *name)
 	return (0);
 }
 
+#ifdef BOOT2
+static spa_t *
+spa_get_primary(void)
+{
+
+	return (STAILQ_FIRST(&zfs_pools));
+}
+
+static vdev_t *
+spa_get_primary_vdev(const spa_t *spa)
+{
+	vdev_t *vdev;
+	vdev_t *kid;
+
+	if (spa == NULL)
+		spa = spa_get_primary();
+	if (spa == NULL)
+		return (NULL);
+	vdev = STAILQ_FIRST(&spa->spa_vdevs);
+	if (vdev == NULL)
+		return (NULL);
+	for (kid = STAILQ_FIRST(&vdev->v_children); kid != NULL;
+	     kid = STAILQ_FIRST(&vdev->v_children))
+		vdev = kid;
+	return (vdev);
+}
+#endif
+
 static spa_t *
 spa_create(uint64_t guid)
 {