MFOpenZFS: Add support for boot environment data to be stored in the label

We are building new bootonce mechanism (previously zfs bootnext) and it is
based on this OpenZFS change. Since this patch is nicely self contained,
I am commiting it as is, and we can stack our changes.

Original patch description follows:

Modern bootloaders leverage data stored in the root filesystem to
enable some of their powerful features. GRUB specifically has a grubenv
file which can store large amounts of configuration data that can be
read and written at boot time and during normal operation. This allows
sysadmins to configure useful features like automated failover after
failed boot attempts. Unfortunately, due to the Copy-on-Write nature
of ZFS, the standard behavior of these tools cannot handle writing to
ZFS files safely at boot time. We need an alternative way to store
data that allows the bootloader to make changes to the data.

This work is very similar to work that was done on Illumos to enable
similar functionality in the FreeBSD bootloader. This patch is different
in that the data being stored is a raw grubenv file; this file can store
arbitrary variables and values, and the scripting provided by grub is
powerful enough that special structures are not required to implement
advanced behavior.

We repurpose the second padding area in each label to store the grubenv
file, protected by an embedded checksum. We add two ioctls to get and
set this data, and libzfs_core and libzfs functions to access them more
easily. There are no direct command line interfaces to these functions;
these will be added directly to the bootloader utilities.

Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Paul Dagnelie <pcd@delphix.com>
Closes #10009

Obtained from:	OpenZFS
Sponsored by:	Netflix, Klara Inc.

5 files changed, 68 insertions, 6 deletions

diff --git a/cddl/contrib/opensolaris/cmd/zinject/translate.c b/cddl/contrib/opensolaris/cmd/zinject/translate.c
index af25d3c3c17d..99a3d0ca4ff3 100644
--- a/cddl/contrib/opensolaris/cmd/zinject/translate.c
+++ b/cddl/contrib/opensolaris/cmd/zinject/translate.c
@@ -20,7 +20,7 @@
  */
 /*
  * Copyright (c) 2006, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2012 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2020 by Delphix. All rights reserved.
  */
 
 #include <libzfs.h>
@@ -484,7 +484,7 @@ translate_device(const char *pool, const char *device, err_type_t label_type,
 		record->zi_end = record->zi_start + VDEV_PAD_SIZE - 1;
 		break;
 	case TYPE_LABEL_PAD2:
-		record->zi_start = offsetof(vdev_label_t, vl_pad2);
+		record->zi_start = offsetof(vdev_label_t, vl_be);
 		record->zi_end = record->zi_start + VDEV_PAD_SIZE - 1;
 		break;
 	}
diff --git a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs.h b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs.h
index 469d61f5e773..1899e318d53e 100644
--- a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs.h
+++ b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs.h
@@ -837,6 +837,8 @@ extern int zpool_in_use(libzfs_handle_t *, int, pool_state_t *, char **,
 extern int zpool_read_label(int, nvlist_t **);
 extern int zpool_read_all_labels(int, nvlist_t **);
 extern int zpool_clear_label(int);
+extern int zpool_set_bootenv(zpool_handle_t *, const char *);
+extern int zpool_get_bootenv(zpool_handle_t *, char *, size_t, off_t);
 
 /* is this zvol valid for use as a dump device? */
 extern int zvol_check_dump_config(char *);
diff --git a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_pool.c b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_pool.c
index 39b6c35f6fbd..434f77e27da9 100644
--- a/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_pool.c
+++ b/cddl/contrib/opensolaris/lib/libzfs/common/libzfs_pool.c
@@ -21,7 +21,7 @@
 
 /*
  * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
- * Copyright (c) 2011, 2017 by Delphix. All rights reserved.
+ * Copyright (c) 2011, 2020 by Delphix. All rights reserved.
  * Copyright (c) 2013, Joyent, Inc. All rights reserved.
  * Copyright 2016 Nexenta Systems, Inc.
  * Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com>
@@ -395,7 +395,7 @@ zpool_get_prop(zpool_handle_t *zhp, zpool_prop_t prop, char *buf, size_t len,
  * Assuming bootfs is a valid dataset name.
  */
 static boolean_t
-bootfs_name_valid(const char *pool, char *bootfs)
+bootfs_name_valid(const char *pool, const char *bootfs)
 {
 	int len = strlen(pool);
 
@@ -4233,6 +4233,42 @@ zpool_obj_to_path(zpool_handle_t *zhp, uint64_t dsobj, uint64_t obj,
 	free(mntpnt);
 }
 
+int
+zpool_set_bootenv(zpool_handle_t *zhp, const char *envmap)
+{
+	int error = lzc_set_bootenv(zhp->zpool_name, envmap);
+	if (error != 0) {
+		(void) zpool_standard_error_fmt(zhp->zpool_hdl, error,
+		    dgettext(TEXT_DOMAIN,
+		    "error setting bootenv in pool '%s'"), zhp->zpool_name);
+	}
+
+	return (error);
+}
+
+int
+zpool_get_bootenv(zpool_handle_t *zhp, char *outbuf, size_t size, off_t offset)
+{
+	nvlist_t *nvl;
+	int error = lzc_get_bootenv(zhp->zpool_name, &nvl);;
+	if (error != 0) {
+		(void) zpool_standard_error_fmt(zhp->zpool_hdl, error,
+		    dgettext(TEXT_DOMAIN,
+		    "error getting bootenv in pool '%s'"), zhp->zpool_name);
+		return (-1);
+	}
+	char *envmap = fnvlist_lookup_string(nvl, "envmap");
+	if (offset >= strlen(envmap)) {
+		fnvlist_free(nvl);
+		return (0);
+	}
+
+	strlcpy(outbuf, envmap + offset, size);
+	int bytes = MIN(strlen(envmap + offset), size);
+	fnvlist_free(nvl);
+	return (bytes);
+}
+
 #ifdef illumos
 /*
  * Read the EFI label from the config, if a label does not exist then
diff --git a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
index f4ed52a29232..2a6b5cc5927c 100644
--- a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
+++ b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.c
@@ -20,7 +20,7 @@
  */
 
 /*
- * Copyright (c) 2012, 2018 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2020 by Delphix. All rights reserved.
  * Copyright (c) 2013 Steven Hartland. All rights reserved.
  * Copyright (c) 2014 Integros [integros.com]
  * Copyright 2017 RackTop Systems.
@@ -1210,3 +1210,25 @@ lzc_initialize(const char *poolname, pool_initialize_func_t cmd_type,
 
 	return (error);
 }
+
+/*
+ * Set the bootenv contents for the given pool.
+ */
+int
+lzc_set_bootenv(const char *pool, const char *env)
+{
+	nvlist_t *args = fnvlist_alloc();
+	fnvlist_add_string(args, "envmap", env);
+	int error = lzc_ioctl(ZFS_IOC_SET_BOOTENV, pool, args, NULL);
+	fnvlist_free(args);
+	return (error);
+}
+
+/*
+ * Get the contents of the bootenv of the given pool.
+ */
+int
+lzc_get_bootenv(const char *pool, nvlist_t **outnvl)
+{
+	return (lzc_ioctl(ZFS_IOC_GET_BOOTENV, pool, NULL, outnvl));
+}
diff --git a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.h b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.h
index 97d7ce81d8ab..76c4fa1bf6b4 100644
--- a/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.h
+++ b/cddl/contrib/opensolaris/lib/libzfs_core/common/libzfs_core.h
@@ -20,7 +20,7 @@
  */
 
 /*
- * Copyright (c) 2012, 2016 by Delphix. All rights reserved.
+ * Copyright (c) 2012, 2020 by Delphix. All rights reserved.
  * Copyright (c) 2013 by Martin Matuska <mm@FreeBSD.org>. All rights reserved.
  * Copyright 2017 RackTop Systems.
  * Copyright (c) 2017 Datto Inc.
@@ -105,6 +105,8 @@ int lzc_channel_program_nosync(const char *, const char *, uint64_t,
 int lzc_pool_checkpoint(const char *);
 int lzc_pool_checkpoint_discard(const char *);
 
+int lzc_set_bootenv(const char *, const char *);
+int lzc_get_bootenv(const char *, nvlist_t **);
 #ifdef	__cplusplus
 }
 #endif