Allow zhack label repair to restore detached devices.

This commit expands on the zhack label repair command in d04b5c9 by
adding the -u option to undetach a device by regenerating uberblocks,
in addition to the existing functionality of fixing checksums, now
represented by -c. Previous behavior is retained in the case of no
options.

The changes are heavily inspired by Jeff Bonwick's labelfix
utility, as archived at:

https://gist.github.com/jjwhitney/baaa63144da89726e482

Additionally, it is now capable of properly determining the size of
block devices and other media, as well as handling sizes which are
not divisible by 2^18. This should make it viable for use on physical
devices and partitions, in addition to files.

These changes should make it possible to import zpools that have had
their uberblocks erased, such as in the case of pools rendered
inaccessible by erroneous detach commands.

Reviewed-by: Brian Behlendorf <[email protected]>
Signed-off-by: buzzingwires <[email protected]>
Closes #14773 

1 files changed, 415 insertions, 93 deletions

diff --git a/cmd/zhack.c b/cmd/zhack.c
index 0b6da31ec..44611887d 100644
--- a/cmd/zhack.c
+++ b/cmd/zhack.c
@@ -58,6 +58,12 @@ static importargs_t g_importargs;
 static char *g_pool;
 static boolean_t g_readonly;
 
+typedef enum {
+	ZHACK_REPAIR_OP_UNKNOWN  = 0,
+	ZHACK_REPAIR_OP_CKSUM    = (1 << 0),
+	ZHACK_REPAIR_OP_UNDETACH = (1 << 1)
+} zhack_repair_op_t;
+
 static __attribute__((noreturn)) void
 usage(void)
 {
@@ -81,7 +87,10 @@ usage(void)
 	    "    <feature> : should be a feature guid\n"
 	    "\n"
 	    "    label repair <device>\n"
-	    "        repair corrupted label checksums\n"
+	    "        repair labels of a specified device according to options\n"
+	    "        which may be combined to do their functions in one call\n"
+	    "        -c repair corrupted label checksums\n"
+	    "        -u restore the label on a detached device\n"
 	    "\n"
 	    "    <device> : path to vdev\n");
 	exit(1);
@@ -485,119 +494,398 @@ zhack_do_feature(int argc, char **argv)
 	return (0);
 }
 
+#define	ASHIFT_UBERBLOCK_SHIFT(ashift)	\
+	MIN(MAX(ashift, UBERBLOCK_SHIFT), \
+	MAX_UBERBLOCK_SHIFT)
+#define	ASHIFT_UBERBLOCK_SIZE(ashift) \
+	(1ULL << ASHIFT_UBERBLOCK_SHIFT(ashift))
+
+#define	REPAIR_LABEL_STATUS_CKSUM (1 << 0)
+#define	REPAIR_LABEL_STATUS_UB    (1 << 1)
+
 static int
-zhack_repair_label_cksum(int argc, char **argv)
+zhack_repair_read_label(const int fd, vdev_label_t *vl,
+    const uint64_t label_offset, const int l)
 {
-	zio_checksum_info_t *ci = &zio_checksum_table[ZIO_CHECKSUM_LABEL];
-	const char *cfg_keys[] = { ZPOOL_CONFIG_VERSION,
-	    ZPOOL_CONFIG_POOL_STATE, ZPOOL_CONFIG_GUID };
-	boolean_t labels_repaired[VDEV_LABELS] = {0};
-	boolean_t repaired = B_FALSE;
-	vdev_label_t labels[VDEV_LABELS] = {{{0}}};
-	struct stat st;
-	int fd;
+	const int err = pread64(fd, vl, sizeof (vdev_label_t), label_offset);
 
-	abd_init();
+	if (err == -1) {
+		(void) fprintf(stderr,
+		    "error: cannot read label %d: %s\n",
+		    l, strerror(errno));
+		return (err);
+	} else if (err != sizeof (vdev_label_t)) {
+		(void) fprintf(stderr,
+		    "error: bad label %d read size\n", l);
+		return (err);
+	}
 
-	argc -= 1;
-	argv += 1;
+	return (0);
+}
 
-	if (argc < 1) {
-		(void) fprintf(stderr, "error: missing device\n");
-		usage();
-	}
+static void
+zhack_repair_calc_cksum(const int byteswap, void *data, const uint64_t offset,
+    const uint64_t abdsize, zio_eck_t *eck, zio_cksum_t *cksum)
+{
+	zio_cksum_t verifier;
+	zio_cksum_t current_cksum;
+	zio_checksum_info_t *ci;
+	abd_t *abd;
 
-	if ((fd = open(argv[0], O_RDWR)) == -1)
-		fatal(NULL, FTAG, "cannot open '%s': %s", argv[0],
-		    strerror(errno));
+	ZIO_SET_CHECKSUM(&verifier, offset, 0, 0, 0);
 
-	if (stat(argv[0], &st) != 0)
-		fatal(NULL, FTAG, "cannot stat '%s': %s", argv[0],
-		    strerror(errno));
+	if (byteswap)
+		byteswap_uint64_array(&verifier, sizeof (zio_cksum_t));
 
-	for (int l = 0; l < VDEV_LABELS; l++) {
-		uint64_t label_offset, offset;
-		zio_cksum_t expected_cksum;
-		zio_cksum_t actual_cksum;
-		zio_cksum_t verifier;
-		zio_eck_t *eck;
-		nvlist_t *cfg;
-		int byteswap;
+	current_cksum = eck->zec_cksum;
+	eck->zec_cksum = verifier;
+
+	ci = &zio_checksum_table[ZIO_CHECKSUM_LABEL];
+	abd = abd_get_from_buf(data, abdsize);
+	ci->ci_func[byteswap](abd, abdsize, NULL, cksum);
+	abd_free(abd);
+
+	eck->zec_cksum = current_cksum;
+}
+
+static int
+zhack_repair_check_label(uberblock_t *ub, const int l, const char **cfg_keys,
+    const size_t cfg_keys_len, nvlist_t *cfg, nvlist_t *vdev_tree_cfg,
+    uint64_t *ashift)
+{
+	int err;
+
+	if (ub->ub_txg != 0) {
+		(void) fprintf(stderr,
+		    "error: label %d: UB TXG of 0 expected, but got %"
+		    PRIu64 "\n",
+		    l, ub->ub_txg);
+		(void) fprintf(stderr, "It would appear the device was not "
+		    "properly removed.\n");
+		return (1);
+	}
+
+	for (int i = 0; i < cfg_keys_len; i++) {
 		uint64_t val;
-		ssize_t err;
-
-		vdev_label_t *vl = &labels[l];
-
-		label_offset = vdev_label_offset(st.st_size, l, 0);
-		err = pread64(fd, vl, sizeof (vdev_label_t), label_offset);
-		if (err == -1) {
-			(void) fprintf(stderr, "error: cannot read "
-			    "label %d: %s\n", l, strerror(errno));
-			continue;
-		} else if (err != sizeof (vdev_label_t)) {
-			(void) fprintf(stderr, "error: bad label %d read size "
-			    "\n", l);
-			continue;
+		err = nvlist_lookup_uint64(cfg, cfg_keys[i], &val);
+		if (err) {
+			(void) fprintf(stderr,
+			    "error: label %d, %d: "
+			    "cannot find nvlist key %s\n",
+			    l, i, cfg_keys[i]);
+			return (err);
 		}
+	}
 
-		err = nvlist_unpack(vl->vl_vdev_phys.vp_nvlist,
-		    VDEV_PHYS_SIZE - sizeof (zio_eck_t), &cfg, 0);
-		if (err) {
-			(void) fprintf(stderr, "error: cannot unpack nvlist "
-			    "label %d\n", l);
-			continue;
+	err = nvlist_lookup_nvlist(cfg,
+	    ZPOOL_CONFIG_VDEV_TREE, &vdev_tree_cfg);
+	if (err) {
+		(void) fprintf(stderr,
+		    "error: label %d: cannot find nvlist key %s\n",
+		    l, ZPOOL_CONFIG_VDEV_TREE);
+		return (err);
+	}
+
+	err = nvlist_lookup_uint64(vdev_tree_cfg,
+	    ZPOOL_CONFIG_ASHIFT, ashift);
+	if (err) {
+		(void) fprintf(stderr,
+		    "error: label %d: cannot find nvlist key %s\n",
+		    l, ZPOOL_CONFIG_ASHIFT);
+		return (err);
+	}
+
+	if (*ashift == 0) {
+		(void) fprintf(stderr,
+		    "error: label %d: nvlist key %s is zero\n",
+		    l, ZPOOL_CONFIG_ASHIFT);
+		return (err);
+	}
+
+	return (0);
+}
+
+static int
+zhack_repair_undetach(uberblock_t *ub, nvlist_t *cfg, const int l)
+{
+	/*
+	 * Uberblock root block pointer has valid birth TXG.
+	 * Copying it to the label NVlist
+	 */
+	if (ub->ub_rootbp.blk_birth != 0) {
+		const uint64_t txg = ub->ub_rootbp.blk_birth;
+		ub->ub_txg = txg;
+
+		if (nvlist_remove_all(cfg, ZPOOL_CONFIG_CREATE_TXG) != 0) {
+			(void) fprintf(stderr,
+			    "error: label %d: "
+			    "Failed to remove pool creation TXG\n",
+			    l);
+			return (1);
 		}
 
-		for (int i = 0; i < ARRAY_SIZE(cfg_keys); i++) {
-			err = nvlist_lookup_uint64(cfg, cfg_keys[i], &val);
-			if (err) {
-				(void) fprintf(stderr, "error: label %d: "
-				    "cannot find nvlist key %s\n",
-				    l, cfg_keys[i]);
-				continue;
-			}
+		if (nvlist_remove_all(cfg, ZPOOL_CONFIG_POOL_TXG) != 0) {
+			(void) fprintf(stderr,
+			    "error: label %d: Failed to remove pool TXG to "
+			    "be replaced.\n",
+			    l);
+			return (1);
 		}
 
-		void *data = (char *)vl + offsetof(vdev_label_t, vl_vdev_phys);
-		eck = (zio_eck_t *)((char *)(data) + VDEV_PHYS_SIZE) - 1;
+		if (nvlist_add_uint64(cfg, ZPOOL_CONFIG_POOL_TXG, txg) != 0) {
+			(void) fprintf(stderr,
+			    "error: label %d: "
+			    "Failed to add pool TXG of %" PRIu64 "\n",
+			    l, txg);
+			return (1);
+		}
+	}
+
+	return (0);
+}
 
-		offset = label_offset + offsetof(vdev_label_t, vl_vdev_phys);
-		ZIO_SET_CHECKSUM(&verifier, offset, 0, 0, 0);
+static boolean_t
+zhack_repair_write_label(const int l, const int fd, const int byteswap,
+    void *data, zio_eck_t *eck, const uint64_t offset, const uint64_t abdsize)
+{
+	zio_cksum_t actual_cksum;
+	zhack_repair_calc_cksum(byteswap, data, offset, abdsize, eck,
+	    &actual_cksum);
+	zio_cksum_t expected_cksum = eck->zec_cksum;
+	ssize_t err;
+
+	if (ZIO_CHECKSUM_EQUAL(actual_cksum, expected_cksum))
+		return (B_FALSE);
+
+	eck->zec_cksum = actual_cksum;
+
+	err = pwrite64(fd, data, abdsize, offset);
+	if (err == -1) {
+		(void) fprintf(stderr, "error: cannot write label %d: %s\n",
+		    l, strerror(errno));
+		return (B_FALSE);
+	} else if (err != abdsize) {
+		(void) fprintf(stderr, "error: bad write size label %d\n", l);
+		return (B_FALSE);
+	} else {
+		(void) fprintf(stderr,
+		    "label %d: wrote %" PRIu64 " bytes at offset %" PRIu64 "\n",
+		    l, abdsize, offset);
+	}
 
-		byteswap = (eck->zec_magic == BSWAP_64(ZEC_MAGIC));
-		if (byteswap)
-			byteswap_uint64_array(&verifier, sizeof (zio_cksum_t));
+	return (B_TRUE);
+}
 
-		expected_cksum = eck->zec_cksum;
-		eck->zec_cksum = verifier;
+static void
+zhack_repair_write_uberblock(vdev_label_t *vl, const int l,
+    const uint64_t ashift, const int fd, const int byteswap,
+    const uint64_t label_offset, uint32_t *labels_repaired)
+{
+	void *ub_data =
+	    (char *)vl + offsetof(vdev_label_t, vl_uberblock);
+	zio_eck_t *ub_eck =
+	    (zio_eck_t *)
+	    ((char *)(ub_data) + (ASHIFT_UBERBLOCK_SIZE(ashift))) - 1;
 
-		abd_t *abd = abd_get_from_buf(data, VDEV_PHYS_SIZE);
-		ci->ci_func[byteswap](abd, VDEV_PHYS_SIZE, NULL, &actual_cksum);
-		abd_free(abd);
+	if (ub_eck->zec_magic != 0) {
+		(void) fprintf(stderr,
+		    "error: label %d: "
+		    "Expected Uberblock checksum magic number to "
+		    "be 0, but got %" PRIu64 "\n",
+		    l, ub_eck->zec_magic);
+		(void) fprintf(stderr, "It would appear there's already "
+		    "a checksum for the uberblock.\n");
+		return;
+	}
 
-		if (byteswap)
-			byteswap_uint64_array(&expected_cksum,
-			    sizeof (zio_cksum_t));
 
-		if (ZIO_CHECKSUM_EQUAL(actual_cksum, expected_cksum))
-			continue;
+	ub_eck->zec_magic = byteswap ? BSWAP_64(ZEC_MAGIC) : ZEC_MAGIC;
 
-		eck->zec_cksum = actual_cksum;
+	if (zhack_repair_write_label(l, fd, byteswap,
+	    ub_data, ub_eck,
+	    label_offset + offsetof(vdev_label_t, vl_uberblock),
+	    ASHIFT_UBERBLOCK_SIZE(ashift)))
+			labels_repaired[l] |= REPAIR_LABEL_STATUS_UB;
+}
 
-		err = pwrite64(fd, data, VDEV_PHYS_SIZE, offset);
-		if (err == -1) {
-			(void) fprintf(stderr, "error: cannot write "
-			    "label %d: %s\n", l, strerror(errno));
-			continue;
-		} else if (err != VDEV_PHYS_SIZE) {
-			(void) fprintf(stderr, "error: bad write size "
-			    "label %d\n", l);
-			continue;
+static void
+zhack_repair_print_cksum(FILE *stream, const zio_cksum_t *cksum)
+{
+	(void) fprintf(stream,
+	    "%016llx:%016llx:%016llx:%016llx",
+	    (u_longlong_t)cksum->zc_word[0],
+	    (u_longlong_t)cksum->zc_word[1],
+	    (u_longlong_t)cksum->zc_word[2],
+	    (u_longlong_t)cksum->zc_word[3]);
+}
+
+static int
+zhack_repair_test_cksum(const int byteswap, void *vdev_data,
+    zio_eck_t *vdev_eck, const uint64_t vdev_phys_offset, const int l)
+{
+	const zio_cksum_t expected_cksum = vdev_eck->zec_cksum;
+	zio_cksum_t actual_cksum;
+	zhack_repair_calc_cksum(byteswap, vdev_data, vdev_phys_offset,
+	    VDEV_PHYS_SIZE, vdev_eck, &actual_cksum);
+	const uint64_t expected_magic = byteswap ?
+	    BSWAP_64(ZEC_MAGIC) : ZEC_MAGIC;
+	const uint64_t actual_magic = vdev_eck->zec_magic;
+	int err = 0;
+	if (actual_magic != expected_magic) {
+		(void) fprintf(stderr, "error: label %d: "
+		    "Expected "
+		    "the nvlist checksum magic number to not be %"
+		    PRIu64 " not %" PRIu64 "\n",
+		    l, expected_magic, actual_magic);
+		err = ECKSUM;
+	}
+	if (!ZIO_CHECKSUM_EQUAL(actual_cksum, expected_cksum)) {
+		(void) fprintf(stderr, "error: label %d: "
+		    "Expected the nvlist checksum to be ", l);
+		(void) zhack_repair_print_cksum(stderr,
+		    &expected_cksum);
+		(void) fprintf(stderr, " not ");
+		zhack_repair_print_cksum(stderr, &actual_cksum);
+		(void) fprintf(stderr, "\n");
+		err = ECKSUM;
+	}
+	return (err);
+}
+
+static void
+zhack_repair_one_label(const zhack_repair_op_t op, const int fd,
+    vdev_label_t *vl, const uint64_t label_offset, const int l,
+    uint32_t *labels_repaired)
+{
+	ssize_t err;
+	uberblock_t *ub = (uberblock_t *)vl->vl_uberblock;
+	void *vdev_data =
+	    (char *)vl + offsetof(vdev_label_t, vl_vdev_phys);
+	zio_eck_t *vdev_eck =
+	    (zio_eck_t *)((char *)(vdev_data) + VDEV_PHYS_SIZE) - 1;
+	const uint64_t vdev_phys_offset =
+	    label_offset + offsetof(vdev_label_t, vl_vdev_phys);
+	const char *cfg_keys[] = { ZPOOL_CONFIG_VERSION,
+	    ZPOOL_CONFIG_POOL_STATE, ZPOOL_CONFIG_GUID };
+	nvlist_t *cfg;
+	nvlist_t *vdev_tree_cfg = NULL;
+	uint64_t ashift;
+	int byteswap;
+
+	err = zhack_repair_read_label(fd, vl, label_offset, l);
+	if (err)
+		return;
+
+	if (vdev_eck->zec_magic == 0) {
+		(void) fprintf(stderr, "error: label %d: "
+		    "Expected the nvlist checksum magic number to not be zero"
+		    "\n",
+		    l);
+		(void) fprintf(stderr, "There should already be a checksum "
+		    "for the label.\n");
+		return;
+	}
+
+	byteswap =
+	    (vdev_eck->zec_magic == BSWAP_64((uint64_t)ZEC_MAGIC));
+
+	if (byteswap) {
+		byteswap_uint64_array(&vdev_eck->zec_cksum,
+		    sizeof (zio_cksum_t));
+		vdev_eck->zec_magic = BSWAP_64(vdev_eck->zec_magic);
+	}
+
+	if ((op & ZHACK_REPAIR_OP_CKSUM) == 0 &&
+	    zhack_repair_test_cksum(byteswap, vdev_data, vdev_eck,
+	    vdev_phys_offset, l) != 0) {
+		(void) fprintf(stderr, "It would appear checksums are "
+		    "corrupted. Try zhack repair label -c <device>\n");
+		return;
+	}
+
+	err = nvlist_unpack(vl->vl_vdev_phys.vp_nvlist,
+	    VDEV_PHYS_SIZE - sizeof (zio_eck_t), &cfg, 0);
+	if (err) {
+		(void) fprintf(stderr,
+		    "error: cannot unpack nvlist label %d\n", l);
+		return;
+	}
+
+	err = zhack_repair_check_label(ub,
+	    l, cfg_keys, ARRAY_SIZE(cfg_keys), cfg, vdev_tree_cfg, &ashift);
+	if (err)
+		return;
+
+	if ((op & ZHACK_REPAIR_OP_UNDETACH) != 0) {
+		char *buf;
+		size_t buflen;
+
+		err = zhack_repair_undetach(ub, cfg, l);
+		if (err)
+			return;
+
+		buf = vl->vl_vdev_phys.vp_nvlist;
+		buflen = VDEV_PHYS_SIZE - sizeof (zio_eck_t);
+		if (nvlist_pack(cfg, &buf, &buflen, NV_ENCODE_XDR, 0) != 0) {
+			(void) fprintf(stderr,
+			    "error: label %d: Failed to pack nvlist\n", l);
+			return;
 		}
 
-		fsync(fd);
+		zhack_repair_write_uberblock(vl,
+		    l, ashift, fd, byteswap, label_offset, labels_repaired);
+	}
+
+	if (zhack_repair_write_label(l, fd, byteswap, vdev_data, vdev_eck,
+	    vdev_phys_offset, VDEV_PHYS_SIZE))
+			labels_repaired[l] |= REPAIR_LABEL_STATUS_CKSUM;
+
+	fsync(fd);
+}
+
+static const char *
+zhack_repair_label_status(const uint32_t label_status,
+    const uint32_t to_check)
+{
+	return ((label_status & to_check) != 0 ? "repaired" : "skipped");
+}
+
+static int
+zhack_label_repair(const zhack_repair_op_t op, const int argc, char **argv)
+{
+	uint32_t labels_repaired[VDEV_LABELS] = {0};
+	vdev_label_t labels[VDEV_LABELS] = {{{0}}};
+	struct stat64 st;
+	int fd;
+	off_t filesize;
+	uint32_t repaired = 0;
+
+	abd_init();
+
+	if (argc < 1) {
+		(void) fprintf(stderr, "error: missing device\n");
+		usage();
+	}
+
+	if ((fd = open(argv[0], O_RDWR)) == -1)
+		fatal(NULL, FTAG, "cannot open '%s': %s", argv[0],
+		    strerror(errno));
+
+	if (fstat64_blk(fd, &st) != 0)
+		fatal(NULL, FTAG, "cannot stat '%s': %s", argv[0],
+		    strerror(errno));
+
+	filesize = st.st_size;
+	(void) fprintf(stderr, "Calculated filesize to be %jd\n",
+	    (intmax_t)filesize);
+
+	if (filesize % sizeof (vdev_label_t) != 0)
+		filesize =
+		    (filesize / sizeof (vdev_label_t)) * sizeof (vdev_label_t);
 
-		labels_repaired[l] = B_TRUE;
+	for (int l = 0; l < VDEV_LABELS; l++) {
+		zhack_repair_one_label(op, fd, &labels[l],
+		    vdev_label_offset(filesize, l, 0), l, labels_repaired);
 	}
 
 	close(fd);
@@ -605,18 +893,52 @@ zhack_repair_label_cksum(int argc, char **argv)
 	abd_fini();
 
 	for (int l = 0; l < VDEV_LABELS; l++) {
-		(void) printf("label %d: %s\n", l,
-		    labels_repaired[l] ? "repaired" : "skipped");
-		repaired |= labels_repaired[l];
+		const uint32_t lr = labels_repaired[l];
+		(void) printf("label %d: ", l);
+		(void) printf("uberblock: %s ",
+		    zhack_repair_label_status(lr, REPAIR_LABEL_STATUS_UB));
+		(void) printf("checksum: %s\n",
+		    zhack_repair_label_status(lr, REPAIR_LABEL_STATUS_CKSUM));
+		repaired |= lr;
 	}
 
-	if (repaired)
+	if (repaired > 0)
 		return (0);
 
 	return (1);
 }
 
 static int
+zhack_do_label_repair(int argc, char **argv)
+{
+	zhack_repair_op_t op = ZHACK_REPAIR_OP_UNKNOWN;
+	int c;
+
+	optind = 1;
+	while ((c = getopt(argc, argv, "+cu")) != -1) {
+		switch (c) {
+		case 'c':
+			op |= ZHACK_REPAIR_OP_CKSUM;
+			break;
+		case 'u':
+			op |= ZHACK_REPAIR_OP_UNDETACH;
+			break;
+		default:
+			usage();
+			break;
+		}
+	}
+
+	argc -= optind;
+	argv += optind;
+
+	if (op == ZHACK_REPAIR_OP_UNKNOWN)
+		op = ZHACK_REPAIR_OP_CKSUM;
+
+	return (zhack_label_repair(op, argc, argv));
+}
+
+static int
 zhack_do_label(int argc, char **argv)
 {
 	char *subcommand;
@@ -632,7 +954,7 @@ zhack_do_label(int argc, char **argv)
 
 	subcommand = argv[0];
 	if (strcmp(subcommand, "repair") == 0) {
-		err = zhack_repair_label_cksum(argc, argv);
+		err = zhack_do_label_repair(argc, argv);
 	} else {
 		(void) fprintf(stderr, "error: unknown subcommand: %s\n",
 		    subcommand);