Provide macros for setting and getting blkptr birth times

[mirror_zfs.git] / cmd / zhack.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or https://opensource.org/licenses/CDDL-1.0.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright (c) 2011, 2015 by Delphix. All rights reserved.
 * Copyright (c) 2013 Steven Hartland. All rights reserved.
 */

/*
 * zhack is a debugging tool that can write changes to ZFS pool using libzpool
 * for testing purposes. Altering pools with zhack is unsupported and may
 * result in corrupted pools.
 */

#include <zfs_prop.h>
#include <stdio.h>
#include <stdlib.h>
#include <ctype.h>
#include <sys/stat.h>
#include <sys/zfs_context.h>
#include <sys/spa.h>
#include <sys/spa_impl.h>
#include <sys/dmu.h>
#include <sys/zap.h>
#include <sys/zfs_znode.h>
#include <sys/dsl_synctask.h>
#include <sys/vdev.h>
#include <sys/vdev_impl.h>
#include <sys/fs/zfs.h>
#include <sys/dmu_objset.h>
#include <sys/dsl_pool.h>
#include <sys/zio_checksum.h>
#include <sys/zio_compress.h>
#include <sys/zfeature.h>
#include <sys/dmu_tx.h>
#include <zfeature_common.h>
#include <libzutil.h>

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)
{
        (void) fprintf(stderr,
            "Usage: zhack [-c cachefile] [-d dir] <subcommand> <args> ...\n"
            "where <subcommand> <args> is one of the following:\n"
            "\n");

        (void) fprintf(stderr,
            "    feature stat <pool>\n"
            "        print information about enabled features\n"
            "    feature enable [-r] [-d desc] <pool> <feature>\n"
            "        add a new enabled feature to the pool\n"
            "        -d <desc> sets the feature's description\n"
            "        -r set read-only compatible flag for feature\n"
            "    feature ref [-md] <pool> <feature>\n"
            "        change the refcount on the given feature\n"
            "        -d decrease instead of increase the refcount\n"
            "        -m add the feature to the label if increasing refcount\n"
            "\n"
            "    <feature> : should be a feature guid\n"
            "\n"
            "    label repair <device>\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);
}


static __attribute__((format(printf, 3, 4))) __attribute__((noreturn)) void
fatal(spa_t *spa, const void *tag, const char *fmt, ...)
{
        va_list ap;

        if (spa != NULL) {
                spa_close(spa, tag);
                (void) spa_export(g_pool, NULL, B_TRUE, B_FALSE);
        }

        va_start(ap, fmt);
        (void) fputs("zhack: ", stderr);
        (void) vfprintf(stderr, fmt, ap);
        va_end(ap);
        (void) fputc('\n', stderr);

        exit(1);
}

static int
space_delta_cb(dmu_object_type_t bonustype, const void *data,
    zfs_file_info_t *zoi)
{
        (void) data, (void) zoi;

        /*
         * Is it a valid type of object to track?
         */
        if (bonustype != DMU_OT_ZNODE && bonustype != DMU_OT_SA)
                return (ENOENT);
        (void) fprintf(stderr, "modifying object that needs user accounting");
        abort();
}

/*
 * Target is the dataset whose pool we want to open.
 */
static void
zhack_import(char *target, boolean_t readonly)
{
        nvlist_t *config;
        nvlist_t *props;
        int error;

        kernel_init(readonly ? SPA_MODE_READ :
            (SPA_MODE_READ | SPA_MODE_WRITE));

        dmu_objset_register_type(DMU_OST_ZFS, space_delta_cb);

        g_readonly = readonly;
        g_importargs.can_be_active = readonly;
        g_pool = strdup(target);

        libpc_handle_t lpch = {
                .lpc_lib_handle = NULL,
                .lpc_ops = &libzpool_config_ops,
                .lpc_printerr = B_TRUE
        };
        error = zpool_find_config(&lpch, target, &config, &g_importargs);
        if (error)
                fatal(NULL, FTAG, "cannot import '%s'", target);

        props = NULL;
        if (readonly) {
                VERIFY(nvlist_alloc(&props, NV_UNIQUE_NAME, 0) == 0);
                VERIFY(nvlist_add_uint64(props,
                    zpool_prop_to_name(ZPOOL_PROP_READONLY), 1) == 0);
        }

        zfeature_checks_disable = B_TRUE;
        error = spa_import(target, config, props,
            (readonly ?  ZFS_IMPORT_SKIP_MMP : ZFS_IMPORT_NORMAL));
        fnvlist_free(config);
        zfeature_checks_disable = B_FALSE;
        if (error == EEXIST)
                error = 0;

        if (error)
                fatal(NULL, FTAG, "can't import '%s': %s", target,
                    strerror(error));
}

static void
zhack_spa_open(char *target, boolean_t readonly, const void *tag, spa_t **spa)
{
        int err;

        zhack_import(target, readonly);

        zfeature_checks_disable = B_TRUE;
        err = spa_open(target, spa, tag);
        zfeature_checks_disable = B_FALSE;

        if (err != 0)
                fatal(*spa, FTAG, "cannot open '%s': %s", target,
                    strerror(err));
        if (spa_version(*spa) < SPA_VERSION_FEATURES) {
                fatal(*spa, FTAG, "'%s' has version %d, features not enabled",
                    target, (int)spa_version(*spa));
        }
}

static void
dump_obj(objset_t *os, uint64_t obj, const char *name)
{
        zap_cursor_t zc;
        zap_attribute_t za;

        (void) printf("%s_obj:\n", name);

        for (zap_cursor_init(&zc, os, obj);
            zap_cursor_retrieve(&zc, &za) == 0;
            zap_cursor_advance(&zc)) {
                if (za.za_integer_length == 8) {
                        ASSERT(za.za_num_integers == 1);
                        (void) printf("\t%s = %llu\n",
                            za.za_name, (u_longlong_t)za.za_first_integer);
                } else {
                        ASSERT(za.za_integer_length == 1);
                        char val[1024];
                        VERIFY(zap_lookup(os, obj, za.za_name,
                            1, sizeof (val), val) == 0);
                        (void) printf("\t%s = %s\n", za.za_name, val);
                }
        }
        zap_cursor_fini(&zc);
}

static void
dump_mos(spa_t *spa)
{
        nvlist_t *nv = spa->spa_label_features;
        nvpair_t *pair;

        (void) printf("label config:\n");
        for (pair = nvlist_next_nvpair(nv, NULL);
            pair != NULL;
            pair = nvlist_next_nvpair(nv, pair)) {
                (void) printf("\t%s\n", nvpair_name(pair));
        }
}

static void
zhack_do_feature_stat(int argc, char **argv)
{
        spa_t *spa;
        objset_t *os;
        char *target;

        argc--;
        argv++;

        if (argc < 1) {
                (void) fprintf(stderr, "error: missing pool name\n");
                usage();
        }
        target = argv[0];

        zhack_spa_open(target, B_TRUE, FTAG, &spa);
        os = spa->spa_meta_objset;

        dump_obj(os, spa->spa_feat_for_read_obj, "for_read");
        dump_obj(os, spa->spa_feat_for_write_obj, "for_write");
        dump_obj(os, spa->spa_feat_desc_obj, "descriptions");
        if (spa_feature_is_active(spa, SPA_FEATURE_ENABLED_TXG)) {
                dump_obj(os, spa->spa_feat_enabled_txg_obj, "enabled_txg");
        }
        dump_mos(spa);

        spa_close(spa, FTAG);
}

static void
zhack_feature_enable_sync(void *arg, dmu_tx_t *tx)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;
        zfeature_info_t *feature = arg;

        feature_enable_sync(spa, feature, tx);

        spa_history_log_internal(spa, "zhack enable feature", tx,
            "name=%s flags=%u",
            feature->fi_guid, feature->fi_flags);
}

static void
zhack_do_feature_enable(int argc, char **argv)
{
        int c;
        char *desc, *target;
        spa_t *spa;
        objset_t *mos;
        zfeature_info_t feature;
        const spa_feature_t nodeps[] = { SPA_FEATURE_NONE };

        /*
         * Features are not added to the pool's label until their refcounts
         * are incremented, so fi_mos can just be left as false for now.
         */
        desc = NULL;
        feature.fi_uname = "zhack";
        feature.fi_flags = 0;
        feature.fi_depends = nodeps;
        feature.fi_feature = SPA_FEATURE_NONE;

        optind = 1;
        while ((c = getopt(argc, argv, "+rd:")) != -1) {
                switch (c) {
                case 'r':
                        feature.fi_flags |= ZFEATURE_FLAG_READONLY_COMPAT;
                        break;
                case 'd':
                        if (desc != NULL)
                                free(desc);
                        desc = strdup(optarg);
                        break;
                default:
                        usage();
                        break;
                }
        }

        if (desc == NULL)
                desc = strdup("zhack injected");
        feature.fi_desc = desc;

        argc -= optind;
        argv += optind;

        if (argc < 2) {
                (void) fprintf(stderr, "error: missing feature or pool name\n");
                usage();
        }
        target = argv[0];
        feature.fi_guid = argv[1];

        if (!zfeature_is_valid_guid(feature.fi_guid))
                fatal(NULL, FTAG, "invalid feature guid: %s", feature.fi_guid);

        zhack_spa_open(target, B_FALSE, FTAG, &spa);
        mos = spa->spa_meta_objset;

        if (zfeature_is_supported(feature.fi_guid))
                fatal(spa, FTAG, "'%s' is a real feature, will not enable",
                    feature.fi_guid);
        if (0 == zap_contains(mos, spa->spa_feat_desc_obj, feature.fi_guid))
                fatal(spa, FTAG, "feature already enabled: %s",
                    feature.fi_guid);

        VERIFY0(dsl_sync_task(spa_name(spa), NULL,
            zhack_feature_enable_sync, &feature, 5, ZFS_SPACE_CHECK_NORMAL));

        spa_close(spa, FTAG);

        free(desc);
}

static void
feature_incr_sync(void *arg, dmu_tx_t *tx)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;
        zfeature_info_t *feature = arg;
        uint64_t refcount;

        VERIFY0(feature_get_refcount_from_disk(spa, feature, &refcount));
        feature_sync(spa, feature, refcount + 1, tx);
        spa_history_log_internal(spa, "zhack feature incr", tx,
            "name=%s", feature->fi_guid);
}

static void
feature_decr_sync(void *arg, dmu_tx_t *tx)
{
        spa_t *spa = dmu_tx_pool(tx)->dp_spa;
        zfeature_info_t *feature = arg;
        uint64_t refcount;

        VERIFY0(feature_get_refcount_from_disk(spa, feature, &refcount));
        feature_sync(spa, feature, refcount - 1, tx);
        spa_history_log_internal(spa, "zhack feature decr", tx,
            "name=%s", feature->fi_guid);
}

static void
zhack_do_feature_ref(int argc, char **argv)
{
        int c;
        char *target;
        boolean_t decr = B_FALSE;
        spa_t *spa;
        objset_t *mos;
        zfeature_info_t feature;
        const spa_feature_t nodeps[] = { SPA_FEATURE_NONE };

        /*
         * fi_desc does not matter here because it was written to disk
         * when the feature was enabled, but we need to properly set the
         * feature for read or write based on the information we read off
         * disk later.
         */
        feature.fi_uname = "zhack";
        feature.fi_flags = 0;
        feature.fi_desc = NULL;
        feature.fi_depends = nodeps;
        feature.fi_feature = SPA_FEATURE_NONE;

        optind = 1;
        while ((c = getopt(argc, argv, "+md")) != -1) {
                switch (c) {
                case 'm':
                        feature.fi_flags |= ZFEATURE_FLAG_MOS;
                        break;
                case 'd':
                        decr = B_TRUE;
                        break;
                default:
                        usage();
                        break;
                }
        }
        argc -= optind;
        argv += optind;

        if (argc < 2) {
                (void) fprintf(stderr, "error: missing feature or pool name\n");
                usage();
        }
        target = argv[0];
        feature.fi_guid = argv[1];

        if (!zfeature_is_valid_guid(feature.fi_guid))
                fatal(NULL, FTAG, "invalid feature guid: %s", feature.fi_guid);

        zhack_spa_open(target, B_FALSE, FTAG, &spa);
        mos = spa->spa_meta_objset;

        if (zfeature_is_supported(feature.fi_guid)) {
                fatal(spa, FTAG,
                    "'%s' is a real feature, will not change refcount",
                    feature.fi_guid);
        }

        if (0 == zap_contains(mos, spa->spa_feat_for_read_obj,
            feature.fi_guid)) {
                feature.fi_flags &= ~ZFEATURE_FLAG_READONLY_COMPAT;
        } else if (0 == zap_contains(mos, spa->spa_feat_for_write_obj,
            feature.fi_guid)) {
                feature.fi_flags |= ZFEATURE_FLAG_READONLY_COMPAT;
        } else {
                fatal(spa, FTAG, "feature is not enabled: %s", feature.fi_guid);
        }

        if (decr) {
                uint64_t count;
                if (feature_get_refcount_from_disk(spa, &feature,
                    &count) == 0 && count == 0) {
                        fatal(spa, FTAG, "feature refcount already 0: %s",
                            feature.fi_guid);
                }
        }

        VERIFY0(dsl_sync_task(spa_name(spa), NULL,
            decr ? feature_decr_sync : feature_incr_sync, &feature,
            5, ZFS_SPACE_CHECK_NORMAL));

        spa_close(spa, FTAG);
}

static int
zhack_do_feature(int argc, char **argv)
{
        char *subcommand;

        argc--;
        argv++;
        if (argc == 0) {
                (void) fprintf(stderr,
                    "error: no feature operation specified\n");
                usage();
        }

        subcommand = argv[0];
        if (strcmp(subcommand, "stat") == 0) {
                zhack_do_feature_stat(argc, argv);
        } else if (strcmp(subcommand, "enable") == 0) {
                zhack_do_feature_enable(argc, argv);
        } else if (strcmp(subcommand, "ref") == 0) {
                zhack_do_feature_ref(argc, argv);
        } else {
                (void) fprintf(stderr, "error: unknown subcommand: %s\n",
                    subcommand);
                usage();
        }

        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_read_label(const int fd, vdev_label_t *vl,
    const uint64_t label_offset, const int l)
{
        const int 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));
                return (err);
        } else if (err != sizeof (vdev_label_t)) {
                (void) fprintf(stderr,
                    "error: bad label %d read size\n", l);
                return (err);
        }

        return (0);
}

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;

        ZIO_SET_CHECKSUM(&verifier, offset, 0, 0, 0);

        if (byteswap)
                byteswap_uint64_array(&verifier, sizeof (zio_cksum_t));

        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;
                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_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 (BP_GET_LOGICAL_BIRTH(&ub->ub_rootbp) != 0) {
                const uint64_t txg = BP_GET_LOGICAL_BIRTH(&ub->ub_rootbp);
                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);
                }

                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);
                }

                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);
}

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);
        }

        return (B_TRUE);
}

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;

        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;
        }


        ub_eck->zec_magic = byteswap ? BSWAP_64(ZEC_MAGIC) : ZEC_MAGIC;

        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;
}

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;
                }

                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);

        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);

        abd_fini();

        for (int l = 0; l < VDEV_LABELS; 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 > 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;
        int err;

        argc--;
        argv++;
        if (argc == 0) {
                (void) fprintf(stderr,
                    "error: no label operation specified\n");
                usage();
        }

        subcommand = argv[0];
        if (strcmp(subcommand, "repair") == 0) {
                err = zhack_do_label_repair(argc, argv);
        } else {
                (void) fprintf(stderr, "error: unknown subcommand: %s\n",
                    subcommand);
                usage();
        }

        return (err);
}

#define MAX_NUM_PATHS 1024

int
main(int argc, char **argv)
{
        char *path[MAX_NUM_PATHS];
        const char *subcommand;
        int rv = 0;
        int c;

        g_importargs.path = path;

        dprintf_setup(&argc, argv);
        zfs_prop_init();

        while ((c = getopt(argc, argv, "+c:d:")) != -1) {
                switch (c) {
                case 'c':
                        g_importargs.cachefile = optarg;
                        break;
                case 'd':
                        assert(g_importargs.paths < MAX_NUM_PATHS);
                        g_importargs.path[g_importargs.paths++] = optarg;
                        break;
                default:
                        usage();
                        break;
                }
        }

        argc -= optind;
        argv += optind;
        optind = 1;

        if (argc == 0) {
                (void) fprintf(stderr, "error: no command specified\n");
                usage();
        }

        subcommand = argv[0];

        if (strcmp(subcommand, "feature") == 0) {
                rv = zhack_do_feature(argc, argv);
        } else if (strcmp(subcommand, "label") == 0) {
                return (zhack_do_label(argc, argv));
        } else {
                (void) fprintf(stderr, "error: unknown subcommand: %s\n",
                    subcommand);
                usage();
        }

        if (!g_readonly && spa_export(g_pool, NULL, B_TRUE, B_FALSE) != 0) {
                fatal(NULL, FTAG, "pool export failed; "
                    "changes may not be committed to disk\n");
        }

        kernel_fini();

        return (rv);
}