/*
 * 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 http://www.opensolaris.org/os/licensing.
 * 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 2009 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 * Copyright (c) 2016 by Delphix. All rights reserved.
 */

#include "libdevinfo.h"
#include "devinfo_devlink.h"
#include "device_info.h"

#undef  DEBUG
#ifndef DEBUG
#define NDEBUG 1
#else
#undef  NDEBUG
#endif

#include <assert.h>

static mutex_t update_mutex = DEFAULTMUTEX; /* Protects update record lock */
static mutex_t temp_file_mutex = DEFAULTMUTEX; /* for file creation tests */

static const size_t elem_sizes[DB_TYPES] = {
        sizeof (struct db_node),
        sizeof (struct db_minor),
        sizeof (struct db_link),
        sizeof (char)
};

/*
 * List of directories/files skipped while physically walking /dev
 * Paths are relative to "<root>/dev/"
 */
static const char *skip_dirs[] = {"fd"};
static const char *skip_files[] = {
        "stdout",
        "stdin",
        "stderr"
};

#define N_SKIP_DIRS     (sizeof (skip_dirs) / sizeof (skip_dirs[0]))
#define N_SKIP_FILES    (sizeof (skip_files) / sizeof (skip_files[0]))

#define DI_TEST_DB      ETCDEV "di_test_db"

/*
 *
 * This file contains two sets of interfaces which operate on the reverse
 * links database. One set (which includes di_devlink_open()/_close())
 * allows link generators like devfsadm(8) and ucblinks(1B) (writers) to
 * populate the database with /devices -> /dev mappings. Another set
 * of interfaces (which includes di_devlink_init()/_fini()) allows
 * applications (readers) to lookup the database for /dev links corresponding
 * to a given minor.
 *
 * Writers operate on a cached version of the database. The cache is created
 * when di_devlink_open() is called. As links in /dev are created and removed,
 * the cache is updated to keep it in synch with /dev. When the /dev updates
 * are complete, the link generator calls di_devlink_close() which writes
 * out the cache to the database.
 *
 * Applications which need to lookup the database, call di_devlink_init().
 * di_devlink_init() checks the database file (if one exists). If the
 * database is valid, it is mapped into the address space of the
 * application. The database file consists of several segments. Each
 * segment can be mapped in independently and is mapped on demand.
 *
 *                 Database Layout
 *
 *              ---------------------
 *              |       Magic #     |
 *              | ----------------- |
 *              |       Version     |   HEADER
 *              | ----------------- |
 *              |        ...        |
 *              ---------------------
 *              |                   |
 *              |                   |   NODES
 *              |                   |
 *              |                   |
 *              ---------------------
 *              |                   |
 *              |                   |   MINORS
 *              |                   |
 *              |                   |
 *              ---------------------
 *              |                   |
 *              |                   |   LINKS
 *              |                   |
 *              |                   |
 *              ---------------------
 *              |                   |
 *              |                   |   STRINGS
 *              |                   |
 *              |                   |
 *              ---------------------
 *
 * Readers can lookup /dev links for a specific minor or
 * lookup all /dev links. In the latter case, the node
 * and minor segments are not mapped in and the reader
 * walks through every link in the link segment.
 *
 */
di_devlink_handle_t
di_devlink_open(const char *root_dir, uint_t flags)
{
        int err;
        char path[PATH_MAX];
        struct di_devlink_handle *hdp;
        int retried = 0;

retry:
        /*
         * Allocate a read-write handle but open the DB in readonly
         * mode. We do writes only to a temporary copy of the database.
         */
        if ((hdp = handle_alloc(root_dir, OPEN_RDWR)) == NULL) {
                return (NULL);
        }

        err = open_db(hdp, OPEN_RDONLY);

        /*
         * We don't want to unlink the db at this point - if we did we
         * would be creating a window where consumers would take a slow
         * code path (and those consumers might also trigger requests for
         * db creation, which we are already in the process of doing).
         * When we are done with our update, we use rename to install the
         * latest version of the db file.
         */
        get_db_path(hdp, DB_FILE, path, sizeof (path));

        /*
         * The flags argument is reserved for future use.
         */
        if (flags != 0) {
                handle_free(&hdp); /* also closes the DB */
                errno = EINVAL;
                return (NULL);
        }

        if (cache_alloc(hdp) != 0) {
                handle_free(&hdp);
                return (NULL);
        }

        if (err) {
                /*
                 * Failed to open DB.
                 * The most likely cause is that DB file did not exist.
                 * Call di_devlink_close() to recreate the DB file and
                 * retry di_devlink_open().
                 */
                if (retried == 0) {
                        (void) di_devlink_close(&hdp, 0);
                        retried = 1;
                        goto retry;
                }

                /*
                 * DB cannot be opened, just return the
                 * handle. We will recreate the DB later.
                 */
                return (hdp);
        }

        /* Read the database into the cache */
        CACHE(hdp)->update_count = DB_HDR(hdp)->update_count;
        (void) read_nodes(hdp, NULL, DB_HDR(hdp)->root_idx);
        (void) read_links(hdp, NULL, DB_HDR(hdp)->dngl_idx);

        (void) close_db(hdp);

        return (hdp);
}

static void
get_db_path(
        struct di_devlink_handle *hdp,
        const char *fname,
        char *buf,
        size_t blen)
{
        char *dir = NULL;

#ifdef  DEBUG
        if (dir = getenv(ALT_DB_DIR)) {
                (void) devlink_dprintf(DBG_INFO,
                    "get_db_path: alternate db dir: %s\n", dir);
        }
#endif
        if (dir == NULL) {
                dir = hdp->db_dir;
        }

        (void) snprintf(buf, blen, "%s/%s", dir, fname);
}

static int
open_db(struct di_devlink_handle *hdp, int flags)
{
        size_t sz;
        long page_sz;
        int fd, rv, flg;
        struct stat sbuf;
        uint32_t count[DB_TYPES] = {0};
        char path[PATH_MAX];
        void *cp;

        assert(!DB_OPEN(hdp));

#ifdef  DEBUG
        if (getenv(SKIP_DB)) {
                (void) devlink_dprintf(DBG_INFO,
                    "open_db: skipping database\n");
                return (-1);
        }
#endif
        if ((page_sz = sysconf(_SC_PAGE_SIZE)) == -1) {
                return (-1);
        }

        /*
         * Use O_TRUNC flag for write access, so that the subsequent ftruncate()
         * call will zero-fill the entire file
         */
        if (IS_RDONLY(flags)) {
                flg = O_RDONLY;
                get_db_path(hdp, DB_FILE, path, sizeof (path));
        } else {
                flg = O_RDWR|O_CREAT|O_TRUNC;
                get_db_path(hdp, DB_TMP, path, sizeof (path));
        }

        /*
         * Avoid triggering /dev reconfigure for read when not present
         */
        if (IS_RDONLY(flags) &&
            (strncmp(path, "/dev/", 5) == 0) && !device_exists(path)) {
                return (-1);
        }

        if ((fd = open(path, flg, DB_PERMS)) == -1) {
                return (-1);
        }

        if (IS_RDONLY(flags)) {
                flg = PROT_READ;
                rv = fstat(fd, &sbuf);
                sz = sbuf.st_size;
        } else {
                flg = PROT_READ | PROT_WRITE;
                sz = size_db(hdp, page_sz, count);
                rv = ftruncate(fd, sz);
        }

        if (rv == -1 || sz < HDR_LEN) {
                if (rv != -1)
                        errno = EINVAL;
                (void) close(fd);
                return (-1);
        }

        cp = mmap(0, HDR_LEN, flg, MAP_SHARED, fd, 0);
        if (cp == MAP_FAILED) {
                (void) close(fd);
                return (-1);
        }
        DB(hdp)->hdr = (struct db_hdr *)cp;
        DB(hdp)->db_fd = fd;
        DB(hdp)->flags = flags;

        if (IS_RDONLY(flags)) {
                rv = invalid_db(hdp, sz, page_sz);
        } else {
                rv = init_hdr(hdp, page_sz, count);
        }

        if (rv) {
                (void) devlink_dprintf(DBG_ERR, "open_db: invalid DB(%s)\n",
                    path);
                (void) close_db(hdp);
                return (-1);
        } else {
                (void) devlink_dprintf(DBG_STEP, "open_db: DB(%s): opened\n",
                    path);
                return (0);
        }
}

/*
 * A handle can be allocated for read-only or read-write access
 */
static struct di_devlink_handle *
handle_alloc(const char *root_dir, uint_t flags)
{
        char dev_dir[PATH_MAX], path[PATH_MAX], db_dir[PATH_MAX];
        struct di_devlink_handle *hdp, proto = {0};
        int install = 0;
        int isroot = 0;
        struct stat sb;
        char can_path[PATH_MAX];

        assert(flags == OPEN_RDWR || flags == OPEN_RDONLY);

        dev_dir[0] = '\0';
        db_dir[0] = '\0';

        /*
         * NULL and the empty string are equivalent to "/"
         */
        if (root_dir && root_dir[0] != '\0') {

                if (root_dir[0] != '/') {
                        errno = EINVAL;
                        return (NULL);
                }

#ifdef  DEBUG
                /*LINTED*/
                assert(sizeof (dev_dir) >= PATH_MAX);
#endif
                if ((realpath(root_dir, dev_dir) == NULL) ||
                    (realpath(root_dir, db_dir) == NULL)) {
                        return (NULL);
                }
        } else {
                /*
                 * The dev dir is at /dev i.e. we are not doing a -r /altroot
                 */
                isroot = 1;
        }

        if (strcmp(dev_dir, "/") == 0) {
                dev_dir[0] = 0;
                db_dir[0] = 0;
        } else {
                (void) strlcpy(db_dir, dev_dir, sizeof (db_dir));
        }

        (void) strlcat(dev_dir, DEV, sizeof (dev_dir));
        (void) strlcat(db_dir, ETCDEV, sizeof (db_dir));

        /*
         * The following code is for install. Readers and writers need
         * to be redirected to /tmp/etc/dev for the database file.
         * Note that we test for readonly /etc by actually creating a
         * file since statvfs is not a reliable method for determining
         * readonly filesystems.
         */
        install = 0;
        (void) snprintf(can_path, sizeof (can_path), "%s/%s", ETCDEV, DB_FILE);
        if (flags == OPEN_RDWR && isroot) {
                char di_test_db[PATH_MAX];
                int fd;
                (void) mutex_lock(&temp_file_mutex);
                (void) snprintf(di_test_db, sizeof (di_test_db), "%s.%d",
                    DI_TEST_DB, getpid());
                fd = open(di_test_db, O_CREAT|O_RDWR|O_EXCL, 0644);
                if (fd == -1 && errno == EROFS && stat(can_path, &sb) == -1)
                        install = 1;
                if (fd != -1) {
                        (void) close(fd);
                        (void) unlink(di_test_db);
                }
                (void) mutex_unlock(&temp_file_mutex);
        } else if (isroot) {
                /*
                 * Readers can be non-privileged so we cannot test by creating
                 * a file in /etc/dev. Instead we check if the database
                 * file is missing in /etc/dev and is present in /tmp/etc/dev
                 * and is owned by root.
                 */
                char install_path[PATH_MAX];

                (void) snprintf(install_path, sizeof (install_path),
                    "/tmp%s/%s", ETCDEV, DB_FILE);
                if (stat(can_path, &sb) == -1 && stat(install_path, &sb)
                    != -1 && sb.st_uid == 0) {
                        install = 1;
                }
        }

        /*
         * Check if we are in install. If we are, the database will be in
         * /tmp/etc/dev
         */
        if (install)
                (void) snprintf(db_dir, sizeof (db_dir), "/tmp%s", ETCDEV);

        proto.dev_dir = dev_dir;
        proto.db_dir = db_dir;
        proto.flags = flags;
        proto.lock_fd = -1;

        /*
         * Lock database if a read-write handle is being allocated.
         * Locks are needed to protect against multiple writers.
         * Readers don't need locks.
         */
        if (HDL_RDWR(&proto)) {
                if (enter_db_lock(&proto, root_dir) != 1) {
                        return (NULL);
                }
        }

        DB(&proto)->db_fd = -1;

        hdp = calloc(1, sizeof (struct di_devlink_handle));
        if (hdp == NULL) {
                goto error;
        }

        *hdp = proto;

        /*
         * The handle hdp now contains a pointer to local storage
         * in the dev_dir field (obtained from the proto handle).
         * In the following line, a dynamically allocated version
         * is substituted.
         */

        if ((hdp->dev_dir = strdup(proto.dev_dir)) == NULL) {
                free(hdp);
                goto error;
        }

        if ((hdp->db_dir = strdup(proto.db_dir)) == NULL) {
                free(hdp->dev_dir);
                free(hdp);
                goto error;
        }

        return (hdp);

error:
        if (HDL_RDWR(&proto)) {
                /* Unlink DB file on error */
                get_db_path(&proto, DB_FILE, path, sizeof (path));
                (void) unlink(path);
                exit_db_lock(&proto);
        }
        return (NULL);
}


static int
cache_alloc(struct di_devlink_handle *hdp)
{
        size_t hash_sz = 0;

        assert(HDL_RDWR(hdp));

        if (DB_OPEN(hdp)) {
                hash_sz = DB_NUM(hdp, DB_LINK) / AVG_CHAIN_SIZE;
        }
        hash_sz = (hash_sz >= MIN_HASH_SIZE) ? hash_sz : MIN_HASH_SIZE;

        CACHE(hdp)->hash = calloc(hash_sz, sizeof (cache_link_t *));
        if (CACHE(hdp)->hash == NULL) {
                return (-1);
        }
        CACHE(hdp)->hash_sz = hash_sz;

        return (0);
}


static int
invalid_db(struct di_devlink_handle *hdp, size_t fsize, long page_sz)
{
        int i;
        char *cp;
        size_t sz;

        if (DB_HDR(hdp)->magic != DB_MAGIC || DB_HDR(hdp)->vers != DB_VERSION) {
                return (1);
        }

        if (DB_HDR(hdp)->page_sz == 0 || DB_HDR(hdp)->page_sz != page_sz) {
                return (1);
        }

        sz = seg_size(hdp, DB_HEADER);
        for (i = 0; i < DB_TYPES; i++) {
                (void) devlink_dprintf(DBG_INFO, "N[%u] = %u\n", i,
                    DB_NUM(hdp, i));
                /* There must be at least 1 element of each type */
                if (DB_NUM(hdp, i) < 1) {
                        return (1);
                }
                sz += seg_size(hdp, i);
                assert(sz % page_sz == 0);
        }

        if (sz != fsize) {
                return (1);
        }

        if (!VALID_INDEX(hdp, DB_NODE, DB_HDR(hdp)->root_idx)) {
                return (1);
        }

        if (!VALID_INDEX(hdp, DB_LINK, DB_HDR(hdp)->dngl_idx)) {
                return (1);
        }

        if (DB_EMPTY(hdp)) {
                return (1);
        }

        /*
         * The last character in the string segment must be a NUL char.
         */
        cp = get_string(hdp, DB_NUM(hdp, DB_STR) - 1);
        if (cp == NULL || *cp != '\0') {
                return (1);
        }

        return (0);
}

static int
read_nodes(struct di_devlink_handle *hdp, cache_node_t *pcnp, uint32_t nidx)
{
        char *path;
        cache_node_t *cnp;
        struct db_node *dnp;
        const char *fcn = "read_nodes";

        assert(HDL_RDWR(hdp));

        /*
         * parent node should be NULL only for the root node
         */
        if ((pcnp == NULL) ^ (nidx == DB_HDR(hdp)->root_idx)) {
                (void) devlink_dprintf(DBG_ERR,
                    "%s: invalid parent or index(%u)\n", fcn, nidx);
                SET_DB_ERR(hdp);
                return (-1);
        }

        for (; dnp = get_node(hdp, nidx); nidx = dnp->sib) {

                path = get_string(hdp, dnp->path);

                /*
                 * Insert at head of list to recreate original order
                 */
                cnp = node_insert(hdp, pcnp, path, INSERT_HEAD);
                if (cnp == NULL) {
                        SET_DB_ERR(hdp);
                        break;
                }

                assert(strcmp(path, "/") ^ (nidx == DB_HDR(hdp)->root_idx));
                assert(strcmp(path, "/") != 0 || dnp->sib == DB_NIL);

                if (read_minors(hdp, cnp, dnp->minor) != 0 ||
                    read_nodes(hdp, cnp, dnp->child) != 0) {
                        break;
                }

                (void) devlink_dprintf(DBG_STEP, "%s: node[%u]: %s\n",
                    fcn, nidx, cnp->path);
        }

        return (dnp ? -1 : 0);
}

static int
read_minors(struct di_devlink_handle *hdp, cache_node_t *pcnp, uint32_t nidx)
{
        cache_minor_t *cmnp;
        struct db_minor *dmp;
        char *name, *nodetype;
        const char *fcn = "read_minors";

        assert(HDL_RDWR(hdp));

        if (pcnp == NULL) {
                (void) devlink_dprintf(DBG_ERR, "%s: minor[%u]: orphan minor\n",
                    fcn, nidx);
                SET_DB_ERR(hdp);
                return (-1);
        }

        for (; dmp = get_minor(hdp, nidx); nidx = dmp->sib) {

                name = get_string(hdp, dmp->name);
                nodetype = get_string(hdp, dmp->nodetype);

                cmnp = minor_insert(hdp, pcnp, name, nodetype, NULL);
                if (cmnp == NULL) {
                        SET_DB_ERR(hdp);
                        break;
                }

                (void) devlink_dprintf(DBG_STEP, "%s: minor[%u]: %s\n",
                    fcn, nidx, cmnp->name);

                if (read_links(hdp, cmnp, dmp->link) != 0) {
                        break;
                }
        }

        return (dmp ? -1 : 0);
}

/*
 * If the link is dangling the corresponding minor will be absent.
 */
static int
read_links(struct di_devlink_handle *hdp, cache_minor_t *pcmp, uint32_t nidx)
{
        cache_link_t *clp;
        struct db_link *dlp;
        char *path, *content;

        assert(HDL_RDWR(hdp));

        if (nidx != DB_NIL &&
            ((pcmp == NULL) ^ (nidx == DB_HDR(hdp)->dngl_idx))) {
                (void) devlink_dprintf(DBG_ERR, "read_links: invalid minor or"
                    " index(%u)\n", nidx);
                SET_DB_ERR(hdp);
                return (-1);
        }

        for (; dlp = get_link(hdp, nidx); nidx = dlp->sib) {

                path = get_string(hdp, dlp->path);
                content = get_string(hdp, dlp->content);

                clp = link_insert(hdp, pcmp, path, content, dlp->attr);
                if (clp == NULL) {
                        SET_DB_ERR(hdp);
                        break;
                }

                (void) devlink_dprintf(DBG_STEP, "read_links: link[%u]: %s%s\n",
                    nidx, clp->path, pcmp == NULL ? "(DANGLING)" : "");
        }

        return (dlp ? -1 : 0);
}

int
di_devlink_close(di_devlink_handle_t *pp, int flag)
{
        int i, rv;
        char tmp[PATH_MAX];
        char file[PATH_MAX];
        uint32_t next[DB_TYPES] = {0};
        struct di_devlink_handle *hdp;

        if (pp == NULL || *pp == NULL || !HDL_RDWR(*pp)) {
                errno = EINVAL;
                return (-1);
        }

        hdp = *pp;
        *pp = NULL;

        /*
         * The caller encountered some error in their processing.
         * so handle isn't valid. Discard it and return success.
         */
        if (flag == DI_LINK_ERROR) {
                handle_free(&hdp);
                return (0);
        }

        if (DB_ERR(hdp)) {
                handle_free(&hdp);
                errno = EINVAL;
                return (-1);
        }

        /*
         * Extract the DB path before the handle is freed.
         */
        get_db_path(hdp, DB_FILE, file, sizeof (file));
        get_db_path(hdp, DB_TMP, tmp, sizeof (tmp));

        /*
         * update database with actual contents of /dev
         */
        (void) devlink_dprintf(DBG_INFO,
            "di_devlink_close: update_count = %u\n", CACHE(hdp)->update_count);

        /*
         * For performance reasons, synchronization of the database
         * with /dev is turned off by default. However, applications
         * with appropriate permissions can request a "sync" by
         * calling di_devlink_update().
         */
        if (CACHE(hdp)->update_count == 0) {
                CACHE(hdp)->update_count = 1;
                (void) devlink_dprintf(DBG_INFO,
                    "di_devlink_close: synchronizing DB\n");
                (void) synchronize_db(hdp);
        }

        /*
         * Resolve dangling links AFTER synchronizing DB with /dev as the
         * synchronization process may create dangling links.
         */
        resolve_dangling_links(hdp);

        /*
         * All changes to the cache are complete. Write out the cache
         * to the database only if it is not empty.
         */
        if (CACHE_EMPTY(hdp)) {
                (void) devlink_dprintf(DBG_INFO,
                    "di_devlink_close: skipping write\n");
                (void) unlink(file);
                handle_free(&hdp);
                return (0);
        }

        if (open_db(hdp, OPEN_RDWR) != 0) {
                handle_free(&hdp);
                return (-1);
        }

        /*
         * Keep track of array assignments. There is at least
         * 1 element (the "NIL" element) per type.
         */
        for (i = 0; i < DB_TYPES; i++) {
                next[i] = 1;
        }

        (void) write_nodes(hdp, NULL, CACHE_ROOT(hdp), next);
        (void) write_links(hdp, NULL, CACHE(hdp)->dngl, next);
        DB_HDR(hdp)->update_count = CACHE(hdp)->update_count;

        rv = close_db(hdp);

        if (rv != 0 || DB_ERR(hdp) || rename(tmp, file) != 0) {
                (void) devlink_dprintf(DBG_ERR,
                    "di_devlink_close: %s error: %s\n",
                    rv ? "close_db" : "DB or rename", strerror(errno));
                (void) unlink(tmp);
                (void) unlink(file);
                handle_free(&hdp);
                return (-1);
        }

        handle_free(&hdp);

        (void) devlink_dprintf(DBG_INFO, "di_devlink_close: wrote DB(%s)\n",
            file);

        return (0);
}

/*
 * Inits the database header.
 */
static int
init_hdr(struct di_devlink_handle *hdp, long page_sz, uint32_t *count)
{
        int i;

        DB_HDR(hdp)->magic = DB_MAGIC;
        DB_HDR(hdp)->vers = DB_VERSION;
        DB_HDR(hdp)->root_idx = DB_NIL;
        DB_HDR(hdp)->dngl_idx = DB_NIL;
        DB_HDR(hdp)->page_sz = (uint32_t)page_sz;

        for (i = 0; i < DB_TYPES; i++) {
                assert(count[i] >= 1);
                DB_NUM(hdp, i) = count[i];
        }

        return (0);
}

static int
write_nodes(
        struct di_devlink_handle *hdp,
        struct db_node *pdnp,
        cache_node_t *cnp,
        uint32_t *next)
{
        uint32_t idx;
        struct db_node *dnp;
        const char *fcn = "write_nodes";

        assert(HDL_RDWR(hdp));

        for (; cnp != NULL; cnp = cnp->sib) {

                assert(cnp->path != NULL);

                /* parent node should only be NULL for root node */
                if ((pdnp == NULL) ^ (cnp == CACHE_ROOT(hdp))) {
                        (void) devlink_dprintf(DBG_ERR,
                            "%s: invalid parent for: %s\n", fcn, cnp->path);
                        SET_DB_ERR(hdp);
                        break;
                }

                assert((strcmp(cnp->path, "/") != 0) ^
                    (cnp == CACHE_ROOT(hdp)));

                idx = next[DB_NODE];
                if ((dnp = set_node(hdp, idx)) == NULL) {
                        SET_DB_ERR(hdp);
                        break;
                }

                dnp->path = write_string(hdp, cnp->path, next);
                if (dnp->path == DB_NIL) {
                        SET_DB_ERR(hdp);
                        break;
                }
                /* commit write for this node */
                next[DB_NODE]++;

                if (pdnp == NULL) {
                        assert(DB_HDR(hdp)->root_idx == DB_NIL);
                        DB_HDR(hdp)->root_idx = idx;
                } else {
                        dnp->sib = pdnp->child;
                        pdnp->child = idx;
                }

                (void) devlink_dprintf(DBG_STEP, "%s: node[%u]: %s\n", fcn, idx,
                    cnp->path);

                if (write_minors(hdp, dnp, cnp->minor, next) != 0 ||
                    write_nodes(hdp, dnp, cnp->child, next) != 0) {
                        break;
                }
        }

        return (cnp ? -1 : 0);
}

static int
write_minors(
        struct di_devlink_handle *hdp,
        struct db_node *pdnp,
        cache_minor_t *cmnp,
        uint32_t *next)
{
        uint32_t idx;
        struct db_minor *dmp;
        const char *fcn = "write_minors";

        assert(HDL_RDWR(hdp));

        if (pdnp == NULL) {
                (void) devlink_dprintf(DBG_ERR, "%s: no node for minor: %s\n",
                    fcn, cmnp ? cmnp->name : "<NULL>");
                SET_DB_ERR(hdp);
                return (-1);
        }

        for (; cmnp != NULL; cmnp = cmnp->sib) {

                assert(cmnp->name != NULL);

                idx = next[DB_MINOR];
                if ((dmp = set_minor(hdp, idx)) == NULL) {
                        SET_DB_ERR(hdp);
                        break;
                }

                dmp->name = write_string(hdp, cmnp->name, next);
                dmp->nodetype = write_string(hdp, cmnp->nodetype, next);
                if (dmp->name == DB_NIL || dmp->nodetype == DB_NIL) {
                        dmp->name = dmp->nodetype = DB_NIL;
                        SET_DB_ERR(hdp);
                        break;
                }

                /* Commit writes to this minor */
                next[DB_MINOR]++;

                dmp->sib = pdnp->minor;
                pdnp->minor = idx;

                (void) devlink_dprintf(DBG_STEP, "%s: minor[%u]: %s\n",
                    fcn, idx, cmnp->name);

                if (write_links(hdp, dmp, cmnp->link, next) != 0) {
                        break;
                }
        }

        return (cmnp ? -1 : 0);
}

static int
write_links(
        struct di_devlink_handle *hdp,
        struct db_minor *pdmp,
        cache_link_t *clp,
        uint32_t *next)
{
        uint32_t idx;
        struct db_link *dlp;
        const char *fcn = "write_links";

        assert(HDL_RDWR(hdp));

        /* A NULL minor if and only if the links are dangling */
        if (clp != NULL && ((pdmp == NULL) ^ (clp == CACHE(hdp)->dngl))) {
                (void) devlink_dprintf(DBG_ERR, "%s: invalid minor for link\n",
                    fcn);
                SET_DB_ERR(hdp);
                return (-1);
        }

        for (; clp != NULL; clp = clp->sib) {

                assert(clp->path != NULL);

                if ((pdmp == NULL) ^ (clp->minor == NULL)) {
                        (void) devlink_dprintf(DBG_ERR,
                            "%s: invalid minor for link(%s)\n", fcn, clp->path);
                        SET_DB_ERR(hdp);
                        break;
                }

                idx = next[DB_LINK];
                if ((dlp = set_link(hdp, idx)) == NULL) {
                        SET_DB_ERR(hdp);
                        break;
                }

                dlp->path = write_string(hdp, clp->path, next);
                dlp->content = write_string(hdp, clp->content, next);
                if (dlp->path == DB_NIL || dlp->content == DB_NIL) {
                        dlp->path = dlp->content = DB_NIL;
                        SET_DB_ERR(hdp);
                        break;
                }

                dlp->attr = clp->attr;

                /* Commit writes to this link */
                next[DB_LINK]++;

                if (pdmp != NULL) {
                        dlp->sib = pdmp->link;
                        pdmp->link = idx;
                } else {
                        dlp->sib = DB_HDR(hdp)->dngl_idx;
                        DB_HDR(hdp)->dngl_idx = idx;
                }

                (void) devlink_dprintf(DBG_STEP, "%s: link[%u]: %s%s\n",
                    fcn, idx, clp->path, pdmp == NULL ? "(DANGLING)" : "");
        }

        return (clp ? -1 : 0);
}


static uint32_t
write_string(struct di_devlink_handle *hdp, const char *str, uint32_t *next)
{
        char *dstr;
        uint32_t idx;

        assert(HDL_RDWR(hdp));

        if (str == NULL) {
                (void) devlink_dprintf(DBG_ERR,
                    "write_string: NULL argument\n");
                return (DB_NIL);
        }

        idx = next[DB_STR];
        if (!VALID_STR(hdp, idx, str)) {
                (void) devlink_dprintf(DBG_ERR,
                    "write_string: invalid index[%u], string(%s)\n", idx, str);
                return (DB_NIL);
        }

        if ((dstr = set_string(hdp, idx)) == NULL) {
                return (DB_NIL);
        }

        (void) strcpy(dstr, str);

        next[DB_STR] += strlen(dstr) + 1;

        return (idx);
}

static int
close_db(struct di_devlink_handle *hdp)
{
        int i, rv = 0;
        size_t sz;

        if (!DB_OPEN(hdp)) {
#ifdef  DEBUG
                assert(DB(hdp)->db_fd == -1);
                assert(DB(hdp)->flags == 0);
                for (i = 0; i < DB_TYPES; i++) {
                        assert(DB_SEG(hdp, i) == NULL);
                        assert(DB_SEG_PROT(hdp, i) == 0);
                }
#endif
                return (0);
        }

        /* Unmap header after unmapping all other mapped segments */
        for (i = 0; i < DB_TYPES; i++) {
                if (DB_SEG(hdp, i)) {
                        sz = seg_size(hdp, i);
                        if (DB_RDWR(hdp))
                                rv += msync(DB_SEG(hdp, i), sz, MS_SYNC);
                        (void) munmap(DB_SEG(hdp, i), sz);
                        DB_SEG(hdp, i) = NULL;
                        DB_SEG_PROT(hdp, i) = 0;
                }
        }

        if (DB_RDWR(hdp))
                rv += msync((caddr_t)DB_HDR(hdp), HDR_LEN, MS_SYNC);
        (void) munmap((caddr_t)DB_HDR(hdp), HDR_LEN);
        DB(hdp)->hdr = NULL;

        (void) close(DB(hdp)->db_fd);
        DB(hdp)->db_fd = -1;
        DB(hdp)->flags = 0;

        return (rv ? -1 : 0);
}


static void
cache_free(struct di_devlink_handle *hdp)
{
        cache_link_t *clp;

        subtree_free(hdp, &(CACHE_ROOT(hdp)));
        assert(CACHE_LAST(hdp) == NULL);

        /*
         * Don't bother removing links from hash table chains,
         * as we are freeing the hash table itself.
         */
        while (CACHE(hdp)->dngl != NULL) {
                clp = CACHE(hdp)->dngl;
                CACHE(hdp)->dngl = clp->sib;
                assert(clp->minor == NULL);
                link_free(&clp);
        }

        assert((CACHE(hdp)->hash == NULL) ^ (CACHE(hdp)->hash_sz != 0));

        free(CACHE(hdp)->hash);
        CACHE(hdp)->hash = NULL;
        CACHE(hdp)->hash_sz = 0;
}

static void
handle_free(struct di_devlink_handle **pp)
{
        struct di_devlink_handle *hdp = *pp;

        *pp = NULL;

        if (hdp == NULL)
                return;

        (void) close_db(hdp);
        cache_free(hdp);

        if (HDL_RDWR(hdp))
                exit_db_lock(hdp);
        assert(hdp->lock_fd == -1);

        free(hdp->dev_dir);
        free(hdp->db_dir);
        free(hdp);
}

/*
 * Frees the tree rooted at a node. Siblings of the subtree root
 * have to be handled by the caller.
 */
static void
subtree_free(struct di_devlink_handle *hdp, cache_node_t **pp)
{
        cache_node_t *np;
        cache_link_t *clp;
        cache_minor_t *cmnp;

        if (pp == NULL || *pp == NULL)
                return;

        while ((*pp)->child != NULL) {
                np = (*pp)->child;
                (*pp)->child = np->sib;
                subtree_free(hdp, &np);
        }

        while ((*pp)->minor != NULL) {
                cmnp = (*pp)->minor;
                (*pp)->minor = cmnp->sib;

                while (cmnp->link != NULL) {
                        clp = cmnp->link;
                        cmnp->link = clp->sib;
                        rm_link_from_hash(hdp, clp);
                        link_free(&clp);
                }
                minor_free(hdp, &cmnp);
        }

        node_free(pp);
}

static void
rm_link_from_hash(struct di_devlink_handle *hdp, cache_link_t *clp)
{
        int hval;
        cache_link_t **pp;

        if (clp == NULL)
                return;

        if (clp->path == NULL)
                return;

        hval = hashfn(hdp, clp->path);
        pp = &(CACHE_HASH(hdp, hval));
        for (; *pp != NULL; pp = &(*pp)->hash) {
                if (*pp == clp) {
                        *pp = clp->hash;
                        clp->hash = NULL;
                        return;
                }
        }

        devlink_dprintf(DBG_ERR, "rm_link_from_hash: link(%s) not found\n",
            clp->path);
}

static cache_link_t *
link_hash(di_devlink_handle_t hdp, const char *link, uint_t flags)
{
        int hval;
        cache_link_t **pp, *clp;

        if (link == NULL)
                return (NULL);

        hval = hashfn(hdp, link);
        pp = &(CACHE_HASH(hdp, hval));
        for (; (clp = *pp) != NULL; pp = &clp->hash) {
                if (strcmp(clp->path, link) == 0) {
                        break;
                }
        }

        if (clp == NULL)
                return (NULL);

        if ((flags & UNLINK_FROM_HASH) == UNLINK_FROM_HASH) {
                *pp = clp->hash;
                clp->hash = NULL;
        }

        return (clp);
}

static cache_minor_t *
link2minor(struct di_devlink_handle *hdp, cache_link_t *clp)
{
        cache_link_t *plp;
        const char *minor_path;
        char *cp, buf[PATH_MAX], link[PATH_MAX];
        char abspath[PATH_MAX];
        struct stat st;

        if (TYPE_PRI(attr2type(clp->attr))) {
                /*
                 * For primary link, content should point to a /devices node.
                 */
                if (!is_minor_node(clp->content, &minor_path)) {
                        return (NULL);
                }

                return (lookup_minor(hdp, minor_path, NULL,
                    TYPE_CACHE|CREATE_FLAG));

        }

        /*
         * If secondary, the primary link is derived from the secondary
         * link contents. Secondary link contents can have two formats:
         *      audio -> /dev/sound/0
         *      fb0 -> fbs/afb0
         */

        buf[0] = '\0';
        if (strncmp(clp->content, DEV"/", strlen(DEV"/")) == 0) {
                cp = &clp->content[strlen(DEV"/")];
        } else if (clp->content[0] != '/') {
                if ((cp = strrchr(clp->path, '/')) != NULL) {
                        char savechar = *(cp + 1);
                        *(cp + 1) = '\0';
                        (void) snprintf(buf, sizeof (buf), "%s", clp->path);
                        *(cp + 1) = savechar;
                }
                (void) strlcat(buf, clp->content, sizeof (buf));
                cp = buf;
        } else {
                goto follow_link;
        }

        /*
         * Lookup the primary link if possible and find its minor.
         */
        if ((plp = link_hash(hdp, cp, 0)) != NULL && plp->minor != NULL) {
                return (plp->minor);
        }

        /* realpath() used only as a last resort because it is expensive */
follow_link:
        (void) snprintf(link, sizeof (link), "%s/%s", hdp->dev_dir, clp->path);

#ifdef  DEBUG
        /*LINTED*/
        assert(sizeof (buf) >= PATH_MAX);
#endif

        /*
         * A realpath attempt to lookup a dangling link can invoke implicit
         * reconfig so verify there's an actual device behind the link first.
         */
        if (lstat(link, &st) == -1)
                return (NULL);
        if (S_ISLNK(st.st_mode)) {
                if (s_readlink(link, buf, sizeof (buf)) < 0)
                        return (NULL);
                if (buf[0] != '/') {
                        char *p;
                        size_t n = sizeof (abspath);
                        if (strlcpy(abspath, link, n) >= n)
                                return (NULL);
                        p = strrchr(abspath, '/') + 1;
                        *p = 0;
                        n = sizeof (abspath) - strlen(p);
                        if (strlcpy(p, buf, n) >= n)
                                return (NULL);
                } else {
                        if (strlcpy(abspath, buf, sizeof (abspath)) >=
                            sizeof (abspath))
                                return (NULL);
                }
                if (!device_exists(abspath))
                        return (NULL);
        }

        if (s_realpath(link, buf) == NULL || !is_minor_node(buf, &minor_path)) {
                return (NULL);
        }
        return (lookup_minor(hdp, minor_path, NULL, TYPE_CACHE|CREATE_FLAG));
}


static void
resolve_dangling_links(struct di_devlink_handle *hdp)
{
        cache_minor_t *cmnp;
        cache_link_t *clp, **pp;

        for (pp = &(CACHE(hdp)->dngl); *pp != NULL; ) {
                clp = *pp;
                if ((cmnp = link2minor(hdp, clp)) != NULL) {
                        *pp = clp->sib;
                        clp->sib = cmnp->link;
                        cmnp->link = clp;
                        assert(clp->minor == NULL);
                        clp->minor = cmnp;
                } else {
                        devlink_dprintf(DBG_INFO,
                            "resolve_dangling_links: link(%s): unresolved\n",
                            clp->path);
                        pp = &clp->sib;
                }
        }
}


/*
 * The elements are assumed to be detached from the cache tree.
 */
static void
node_free(cache_node_t **pp)
{
        cache_node_t *cnp = *pp;

        *pp = NULL;

        if (cnp == NULL)
                return;

        free(cnp->path);
        free(cnp);
}

static void
minor_free(struct di_devlink_handle *hdp, cache_minor_t **pp)
{
        cache_minor_t *cmnp = *pp;

        *pp = NULL;

        if (cmnp == NULL)
                return;

        if (CACHE_LAST(hdp) == cmnp) {
                devlink_dprintf(DBG_STEP, "minor_free: last_minor(%s)\n",
                    cmnp->name);
                CACHE_LAST(hdp) = NULL;
        }

        free(cmnp->name);
        free(cmnp->nodetype);
        free(cmnp);
}

static void
link_free(cache_link_t **pp)
{
        cache_link_t *clp = *pp;

        *pp = NULL;

        if (clp == NULL)
                return;

        free(clp->path);
        free(clp->content);
        free(clp);
}

/*
 * Returns the ':' preceding the minor name
 */
static char *
minor_colon(const char *path)
{
        char *cp;

        if ((cp = strrchr(path, '/')) == NULL) {
                return (NULL);
        }

        return (strchr(cp, ':'));
}

static void *
lookup_minor(
        struct di_devlink_handle *hdp,
        const char *minor_path,
        const char *nodetype,
        const int flags)
{
        void *vp;
        char *colon;
        char pdup[PATH_MAX];
        const char *fcn = "lookup_minor";

        if (minor_path == NULL) {
                errno = EINVAL;
                return (NULL);
        }

        (void) snprintf(pdup, sizeof (pdup), "%s", minor_path);

        if ((colon = minor_colon(pdup)) == NULL) {
                (void) devlink_dprintf(DBG_ERR, "%s: invalid minor path(%s)\n",
                    fcn, minor_path);
                errno = EINVAL;
                return (NULL);
        }
        *colon = '\0';

        if ((vp = get_last_minor(hdp, pdup, colon + 1, flags)) != NULL) {
                return (vp);
        }

        if ((vp = lookup_node(hdp, pdup, flags)) == NULL) {
                (void) devlink_dprintf(DBG_ERR, "%s: node(%s) not found\n",
                    fcn, pdup);
                return (NULL);
        }
        *colon = ':';

        if (LOOKUP_CACHE(flags)) {
                cache_minor_t **pp;

                pp = &((cache_node_t *)vp)->minor;
                for (; *pp != NULL; pp = &(*pp)->sib) {
                        if (strcmp((*pp)->name, colon + 1) == 0)
                                break;
                }

                if (*pp == NULL && CREATE_ELEM(flags)) {
                        *pp = minor_insert(hdp, vp, colon + 1, nodetype, pp);
                }
                set_last_minor(hdp, *pp, flags);

                return (*pp);
        } else {
                char *cp;
                uint32_t nidx;
                struct db_minor *dmp;

                nidx = (((struct db_node *)vp)->minor);
                for (; dmp = get_minor(hdp, nidx); nidx = dmp->sib) {
                        cp = get_string(hdp, dmp->name);
                        if (cp && strcmp(cp, colon + 1) == 0)
                                break;
                }
                return (dmp);
        }
}

static void *
lookup_node(struct di_devlink_handle *hdp, char *path, const int flags)
{
        struct tnode tnd = {NULL};

        if (tnd.node = get_last_node(hdp, path, flags))
                return (tnd.node);

        tnd.handle = hdp;
        tnd.flags = flags;

        if (walk_tree(path, &tnd, visit_node) != 0)
                return (NULL);

        return (tnd.node);
}

/*
 * last_minor is used for nodes of TYPE_CACHE only.
 */
static void *
get_last_node(struct di_devlink_handle *hdp, const char *path, int flags)
{
        cache_node_t *cnp;

#ifdef  DEBUG
        if (getenv(SKIP_LAST_CACHE)) {
                (void) devlink_dprintf(DBG_INFO,
                    "get_last_node: SKIPPING \"last\" node cache\n");
                return (NULL);
        }
#endif

        if (!LOOKUP_CACHE(flags) || CACHE_LAST(hdp) == NULL ||
            CACHE_LAST(hdp)->node == NULL) {
                return (NULL);
        }

        cnp = CACHE_LAST(hdp)->node;
        if (strcmp(cnp->path, path) == 0) {
                return (cnp);
        }

        cnp = cnp->sib;
        if (cnp && strcmp(cnp->path, path) == 0) {
                return (cnp);
        }

        return (NULL);
}

static void *
get_last_minor(
        struct di_devlink_handle *hdp,
        const char *devfs_path,
        const char *minor_name,
        int flags)
{
        cache_minor_t *cmnp;

#ifdef  DEBUG
        if (getenv(SKIP_LAST_CACHE)) {
                (void) devlink_dprintf(DBG_INFO,
                    "get_last_minor: SKIPPING \"last\" minor cache\n");
                return (NULL);
        }
#endif

        if (!LOOKUP_CACHE(flags) || CACHE_LAST(hdp) == NULL) {
                return (NULL);
        }

        cmnp = CACHE_LAST(hdp);
        if (strcmp(cmnp->name, minor_name) == 0 && cmnp->node &&
            strcmp(cmnp->node->path, devfs_path) == 0) {
                return (cmnp);
        }

        cmnp = cmnp->sib;
        if (cmnp && strcmp(cmnp->name, minor_name) == 0 && cmnp->node &&
            strcmp(cmnp->node->path, devfs_path) == 0) {
                set_last_minor(hdp, cmnp, TYPE_CACHE);
                return (cmnp);
        }

        return (NULL);
}

static void
set_last_minor(struct di_devlink_handle *hdp, cache_minor_t *cmnp, int flags)
{
#ifdef  DEBUG
        if (getenv(SKIP_LAST_CACHE)) {
                (void) devlink_dprintf(DBG_INFO,
                    "set_last_minor: SKIPPING \"last\" minor cache\n");
                return;
        }
#endif

        if (LOOKUP_CACHE(flags) && cmnp) {
                CACHE_LAST(hdp) = cmnp;
        }
}


/*
 * Returns 0 if normal return or -1 otherwise.
 */
static int
walk_tree(
        char *cur,
        void *arg,
        int (*node_callback)(const char *path, void *arg))
{
        char *slash, buf[PATH_MAX];

        if (cur == NULL || cur[0] != '/' || strlen(cur) > sizeof (buf) - 1) {
                errno = EINVAL;
                return (-1);
        }

        (void) strcpy(buf, "/");

        for (;;) {

                if (node_callback(buf, arg) != DI_WALK_CONTINUE)
                        break;

                while (*cur == '/')
                        cur++;

                if (*cur == '\0')
                        break;

                /*
                 * There is a next component(s). Append a "/" separator for all
                 * but the first (root) component.
                 */
                if (buf[1] != '\0') {
                        (void) strlcat(buf, "/", sizeof (buf));
                }

                if (slash = strchr(cur, '/')) {
                        *slash = '\0';
                        (void) strlcat(buf, cur, sizeof (buf));
                        *slash = '/';
                        cur = slash;
                } else {
                        (void) strlcat(buf, cur, sizeof (buf));
                        cur += strlen(cur);
                }

        }

        return (0);
}


static int
visit_node(const char *path, void *arg)
{
        struct tnode *tnp = arg;

        if (LOOKUP_CACHE(tnp->flags)) {

                cache_node_t *cnp = tnp->node;

                cnp = (cnp) ? cnp->child : CACHE_ROOT(tnp->handle);

                for (; cnp != NULL; cnp = cnp->sib) {
                        if (strcmp(cnp->path, path) == 0)
                                break;
                }
                if (cnp == NULL && CREATE_ELEM(tnp->flags)) {
                        cnp = node_insert(tnp->handle, tnp->node, path,
                            INSERT_TAIL);
                }
                tnp->node = cnp;
        } else {
                char *cp;
                struct db_node *dnp = tnp->node;

                dnp = (dnp) ? get_node(tnp->handle, dnp->child)
                    : get_node(tnp->handle, DB_HDR(tnp->handle)->root_idx);

                for (; dnp != NULL; dnp = get_node(tnp->handle, dnp->sib)) {
                        cp = get_string(tnp->handle, dnp->path);
                        if (cp && strcmp(cp, path) == 0) {
                                break;
                        }
                }
                tnp->node = dnp;
        }

        /*
         * Terminate walk if node is not found for a path component.
         */
        return (tnp->node ? DI_WALK_CONTINUE : DI_WALK_TERMINATE);
}

static void
minor_delete(di_devlink_handle_t hdp, cache_minor_t *cmnp)
{
        cache_link_t **lpp;
        cache_minor_t **mpp;
        const char *fcn = "minor_delete";

        (void) devlink_dprintf(DBG_STEP, "%s: removing minor: %s\n",
            fcn, cmnp->name);

        /* detach minor from node */
        if (cmnp->node != NULL) {
                mpp = &cmnp->node->minor;
                for (; *mpp != NULL; mpp = &(*mpp)->sib) {
                        if (*mpp == cmnp)
                                break;
                }

                if (*mpp == NULL) {
                        (void) devlink_dprintf(DBG_ERR,
                            "%s: dangling minor: %s\n", fcn, cmnp->name);
                } else {
                        *mpp = cmnp->sib;
                }
        } else {
                (void) devlink_dprintf(DBG_ERR, "%s: orphan minor(%s)\n", fcn,
                    cmnp->name);
        }

        delete_unused_nodes(hdp, cmnp->node);

        cmnp->node = NULL;
        cmnp->sib = NULL;

        /* Move all remaining links to dangling list */
        for (lpp = &cmnp->link; *lpp != NULL; lpp = &(*lpp)->sib) {
                (*lpp)->minor = NULL;
        }
        *lpp = CACHE(hdp)->dngl;
        CACHE(hdp)->dngl = cmnp->link;
        cmnp->link = NULL;

        minor_free(hdp, &cmnp);
}

static void
delete_unused_nodes(di_devlink_handle_t hdp, cache_node_t *cnp)
{
        cache_node_t **npp;
        const char *fcn = "delete_unused_nodes";

        if (cnp == NULL)
                return;

        if (cnp->minor != NULL || cnp->child != NULL)
                return;

        (void) devlink_dprintf(DBG_INFO, "%s: removing unused node: %s\n", fcn,
            cnp->path);

        /* Unlink node from tree */
        if (cnp->parent != NULL) {
                npp = &cnp->parent->child;
                for (; *npp != NULL; npp = &(*npp)->sib) {
                        if (*npp == cnp)
                                break;
                }

                if (*npp == NULL) {
                        (void) devlink_dprintf(DBG_ERR,
                            "%s: dangling node: %s\n", fcn, cnp->path);
                } else {
                        *npp = cnp->sib;
                }
        } else if (cnp == CACHE_ROOT(hdp)) {
                CACHE_ROOT(hdp) = NULL;
        } else {
                (void) devlink_dprintf(DBG_ERR, "%s: orphan node (%s)\n", fcn,
                    cnp->path);
        }

        delete_unused_nodes(hdp, cnp->parent);

        cnp->parent = cnp->sib = NULL;

        node_free(&cnp);
}

static int
rm_link(di_devlink_handle_t hdp, const char *link)
{
        cache_link_t *clp;
        const char *fcn = "rm_link";

        if (hdp == NULL || DB_ERR(hdp) || link == NULL || link[0] == '/' ||
            (!HDL_RDWR(hdp) && !HDL_RDONLY(hdp))) {
                devlink_dprintf(DBG_ERR, "%s: %s: invalid args\n",
                    fcn, link ? link : "<NULL>");
                errno = EINVAL;
                return (-1);
        }

        devlink_dprintf(DBG_STEP, "%s: link(%s)\n", fcn, link);

        if ((clp = link_hash(hdp, link, UNLINK_FROM_HASH)) == NULL) {
                return (0);
        }

        link_delete(hdp, clp);

        return (0);
}

int
di_devlink_rm_link(di_devlink_handle_t hdp, const char *link)
{
        if (hdp == NULL || !HDL_RDWR(hdp)) {
                errno = EINVAL;
                return (-1);
        }

        return (rm_link(hdp, link));
}

static void
link_delete(di_devlink_handle_t hdp, cache_link_t *clp)
{
        cache_link_t **pp;
        const char *fcn = "link_delete";

        (void) devlink_dprintf(DBG_STEP, "%s: removing link: %s\n",
            fcn, clp->path);

        if (clp->minor == NULL)
                pp = &(CACHE(hdp)->dngl);
        else
                pp = &clp->minor->link;

        for (; *pp != NULL; pp = &(*pp)->sib) {
                if (*pp == clp)
                        break;
        }

        if (*pp == NULL) {
                (void) devlink_dprintf(DBG_ERR, "%s: link(%s) not on list\n",
                    fcn, clp->path);
        } else {
                *pp = clp->sib;
        }

        delete_unused_minor(hdp, clp->minor);

        clp->minor = NULL;

        link_free(&clp);
}

static void
delete_unused_minor(di_devlink_handle_t hdp, cache_minor_t *cmnp)
{
        if (cmnp == NULL)
                return;

        if (cmnp->link != NULL)
                return;

        devlink_dprintf(DBG_STEP, "delete_unused_minor: removing minor(%s)\n",
            cmnp->name);

        minor_delete(hdp, cmnp);
}

int
di_devlink_add_link(
        di_devlink_handle_t hdp,
        const char *link,
        const char *content,
        int flags)
{
        return (add_link(hdp, link, content, flags) != NULL ? 0 : -1);
}

static cache_link_t *
add_link(
        struct di_devlink_handle *hdp,
        const char *link,
        const char *content,
        int flags)
{
        uint32_t attr;
        cache_link_t *clp;
        cache_minor_t *cmnp;
        const char *fcn = "add_link";

        if (hdp == NULL || DB_ERR(hdp) || link == NULL ||
            link[0] == '/' || content == NULL || !link_flag(flags) ||
            (!HDL_RDWR(hdp) && !HDL_RDONLY(hdp))) {
                devlink_dprintf(DBG_ERR, "%s: %s: invalid args\n",
                    fcn, link ? link : "<NULL>");
                errno = EINVAL;
                return (NULL);
        }

        if ((clp = link_hash(hdp, link, 0)) != NULL) {
                if (link_cmp(clp, content, LINK_TYPE(flags)) != 0) {
                        (void) rm_link(hdp, link);
                } else {
                        return (clp);
                }
        }

        if (TYPE_PRI(flags)) {
                const char *minor_path = NULL;

                if (!is_minor_node(content, &minor_path)) {
                        (void) devlink_dprintf(DBG_ERR,
                            "%s: invalid content(%s) for primary link\n",
                            fcn, content);
                        errno = EINVAL;
                        return (NULL);
                }
                if ((cmnp = lookup_minor(hdp, minor_path, NULL,
                    TYPE_CACHE|CREATE_FLAG)) == NULL) {
                        return (NULL);
                }
                attr = A_PRIMARY;
        } else {
                /*
                 * Defer resolving a secondary link to a minor until the
                 * database is closed. This ensures that the primary link
                 * (required for a successful resolve) has also been created.
                 */
                cmnp = NULL;
                attr = A_SECONDARY;
        }

        return (link_insert(hdp, cmnp, link, content, attr));
}

/*
 * Returns 0 on match or 1 otherwise.
 */
static int
link_cmp(cache_link_t *clp, const char *content, int type)
{
        if (strcmp(clp->content, content) != 0)
                return (1);

        if (attr2type(clp->attr) != type)
                return (1);

        return (0);
}

int
di_devlink_update(di_devlink_handle_t hdp)
{
        if (hdp == NULL || !HDL_RDWR(hdp) || DB_ERR(hdp)) {
                errno = EINVAL;
                return (-1);
        }

        /*
         * Reset the counter to schedule a synchronization with /dev on the next
         * di_devlink_close().
         */
        CACHE(hdp)->update_count = 0;

        return (0);
}

static int
synchronize_db(di_devlink_handle_t hdp)
{
        int hval;
        cache_link_t *clp;
        char pdup[PATH_MAX];
        recurse_t rec = {NULL};
        const char *fcn = "synchronize_db";

        rec.data = NULL;
        rec.fcn = cache_dev_link;

        /*
         * Walk through $ROOT/dev, reading every link and marking the
         * corresponding cached version as valid(adding new links as needed).
         * Then walk through the cache and remove all unmarked links.
         */
        if (recurse_dev(hdp, &rec) != 0) {
                return (-1);
        }

        for (hval = 0; hval < CACHE(hdp)->hash_sz; hval++) {
                for (clp = CACHE_HASH(hdp, hval); clp != NULL; ) {
                        if (GET_VALID_ATTR(clp->attr)) {
                                CLR_VALID_ATTR(clp->attr);
                                clp = clp->hash;
                                continue;
                        }

                        /*
                         * The link is stale, so remove it. Since the link
                         * will be destroyed, use a copy of the link path to
                         * invoke the remove function.
                         */
                        (void) snprintf(pdup, sizeof (pdup), "%s", clp->path);
                        clp = clp->hash;
                        (void) devlink_dprintf(DBG_STEP,
                            "%s: removing invalid link: %s\n", fcn, pdup);
                        (void) di_devlink_rm_link(hdp, pdup);
                }
        }

        (void) devlink_dprintf(DBG_STEP, "%s: update completed\n", fcn);

        return (0);
}

static di_devlink_handle_t
di_devlink_init_impl(const char *root, const char *name, uint_t flags)
{
        int     err = 0;

        if ((flags != 0 && flags != DI_MAKE_LINK) ||
            (flags == 0 && name != NULL)) {
                errno = EINVAL;
                return (NULL);
        }

        if ((flags == DI_MAKE_LINK) &&
            (err = devlink_create(root, name, DCA_DEVLINK_CACHE))) {
                errno = err;
                return (NULL);
        }

        (void) devlink_dprintf(DBG_INFO, "devlink_init_impl: success\n");

        return (devlink_snapshot(root));
}

di_devlink_handle_t
di_devlink_init(const char *name, uint_t flags)
{
        return (di_devlink_init_impl("/", name, flags));
}

di_devlink_handle_t
di_devlink_init_root(const char *root, const char *name, uint_t flags)
{
        return (di_devlink_init_impl(root, name, flags));
}

static di_devlink_handle_t
devlink_snapshot(const char *root_dir)
{
        struct di_devlink_handle *hdp;
        int             err;
        static int      retried = 0;

        if ((hdp = handle_alloc(root_dir, OPEN_RDONLY)) == NULL) {
                return (NULL);
        }

        /*
         * We don't need to lock.  If a consumer wants the very latest db
         * then it must perform a di_devlink_init with the DI_MAKE_LINK
         * flag to force a sync with devfsadm first.  Otherwise, the
         * current database file is opened and mmaped on demand: the rename
         * associated with a db update does not change the contents
         * of files already opened.
         */
again:  err = open_db(hdp, OPEN_RDONLY);

        /*
         * If we failed to open DB the most likely cause is that DB file did
         * not exist. If we have not done a retry, signal devfsadmd to
         * recreate the DB file and retry. If we fail to open the DB after
         * retry, we will walk /dev in di_devlink_walk.
         */
        if (err && (retried == 0)) {
                retried++;
                (void) devlink_create(root_dir, NULL, DCA_DEVLINK_SYNC);
                goto again;
        }
        return (hdp);
}

int
di_devlink_fini(di_devlink_handle_t *pp)
{
        if (pp == NULL || *pp == NULL || !HDL_RDONLY(*pp)) {
                errno = EINVAL;
                return (-1);
        }

        /* Freeing the handle also closes the DB */
        handle_free(pp);

        return (0);
}

int
di_devlink_walk(
        di_devlink_handle_t hdp,
        const char *re,
        const char *minor_path,
        uint_t flags,
        void *arg,
        int (*devlink_callback)(di_devlink_t, void *))
{
        int rv;
        regex_t reg;
        link_desc_t linkd = {NULL};

        if (hdp == NULL || !HDL_RDONLY(hdp)) {
                errno = EINVAL;
                return (-1);
        }

        linkd.minor_path = minor_path;
        linkd.flags = flags;
        linkd.arg = arg;
        linkd.fcn = devlink_callback;

        if (re) {
                if (regcomp(&reg, re, REG_EXTENDED) != 0)
                        return (-1);
                linkd.regp = &reg;
        }

        if (check_args(&linkd)) {
                errno = EINVAL;
                rv = -1;
                goto out;
        }

        if (DB_OPEN(hdp)) {
                rv = walk_db(hdp, &linkd);
        } else {
                rv = walk_dev(hdp, &linkd);
        }

out:
        if (re) {
                regfree(&reg);
        }

        return (rv ? -1 : 0);
}

static int
link_flag(uint_t flags)
{
        if (flags != 0 && flags != DI_PRIMARY_LINK &&
            flags != DI_SECONDARY_LINK) {
                return (0);
        }

        return (1);
}

/*
 * Currently allowed flags are:
 *      DI_PRIMARY_LINK
 *      DI_SECONDARY_LINK
 */
static int
check_args(link_desc_t *linkp)
{
        if (linkp->fcn == NULL)
                return (-1);

        if (!link_flag(linkp->flags)) {
                return (-1);
        }

        /*
         * Minor path can be NULL. In that case, all links will be
         * selected.
         */
        if (linkp->minor_path) {
                if (linkp->minor_path[0] != '/' ||
                    minor_colon(linkp->minor_path) == NULL) {
                        return (-1);
                }
        }

        return (0);
}


/*
 * Walk all links in database if no minor path is specified.
 */
static int
walk_db(struct di_devlink_handle *hdp, link_desc_t *linkp)
{
        assert(DB_OPEN(hdp));

        if (linkp->minor_path == NULL) {
                return (walk_all_links(hdp, linkp));
        } else {
                return (walk_matching_links(hdp, linkp));
        }
}

static int
cache_dev(struct di_devlink_handle *hdp)
{
        size_t sz;
        recurse_t rec = {NULL};

        assert(hdp);
        assert(HDL_RDONLY(hdp));

        if (hdp == NULL || !HDL_RDONLY(hdp)) {
                devlink_dprintf(DBG_ERR, "cache_dev: invalid arg\n");
                return (-1);
        }

        sz = MIN_HASH_SIZE;

        CACHE(hdp)->hash = calloc(sz, sizeof (cache_link_t *));
        if (CACHE(hdp)->hash == NULL) {
                return (-1);
        }
        CACHE(hdp)->hash_sz = sz;

        rec.data = NULL;
        rec.fcn = cache_dev_link;

        return (recurse_dev(hdp, &rec));
}

static int
walk_dev(struct di_devlink_handle *hdp, link_desc_t *linkp)
{
        assert(hdp && linkp);
        assert(!DB_OPEN(hdp));
        assert(HDL_RDONLY(hdp));

        if (hdp == NULL || !HDL_RDONLY(hdp) || DB_OPEN(hdp)) {
                devlink_dprintf(DBG_ERR, "walk_dev: invalid args\n");
                return (-1);
        }

        if (CACHE_EMPTY(hdp) && cache_dev(hdp) != 0) {
                devlink_dprintf(DBG_ERR, "walk_dev: /dev caching failed\n");
                return (-1);
        }

        if (linkp->minor_path)
                walk_cache_minor(hdp, linkp->minor_path, linkp);
        else
                walk_all_cache(hdp, linkp);

        return (linkp->retval);
}

/* ARGSUSED */
static int
cache_dev_link(struct di_devlink_handle *hdp, void *data, const char *link)
{
        int flags;
        cache_link_t *clp;
        char content[PATH_MAX];

        assert(HDL_RDWR(hdp) || HDL_RDONLY(hdp));

        if (s_readlink(link, content, sizeof (content)) < 0) {
                return (DI_WALK_CONTINUE);
        }

        if (is_minor_node(content, NULL)) {
                flags = DI_PRIMARY_LINK;
        } else {
                flags = DI_SECONDARY_LINK;
        }

        assert(strncmp(link, hdp->dev_dir, strlen(hdp->dev_dir)) == 0);

        /*
         * Store only the part after <root-dir>/dev/
         */
        link += strlen(hdp->dev_dir) + 1;

        if ((clp = add_link(hdp, link, content, flags)) != NULL) {
                SET_VALID_ATTR(clp->attr);
        }

        return (DI_WALK_CONTINUE);
}


static int
walk_all_links(struct di_devlink_handle *hdp, link_desc_t *linkp)
{
        struct db_link *dlp;
        uint32_t nidx, eidx;

        assert(DB_NUM(hdp, DB_LINK) >= 1);

        eidx = DB_NUM(hdp, DB_LINK);

        /* Skip the "NIL" (index == 0) link. */
        for (nidx = 1; nidx < eidx; nidx++) {
                /*
                 * Declare this local to the block with zero
                 * initializer so that it gets rezeroed
                 * for each iteration.
                 */
                struct di_devlink vlink = {NULL};

                if ((dlp = get_link(hdp, nidx)) == NULL)
                        continue;

                vlink.rel_path = get_string(hdp, dlp->path);
                vlink.content = get_string(hdp, dlp->content);
                vlink.type = attr2type(dlp->attr);

                if (visit_link(hdp, linkp, &vlink) != DI_WALK_CONTINUE) {
                        break;
                }
        }

        return (linkp->retval);
}

static int
walk_matching_links(struct di_devlink_handle *hdp, link_desc_t *linkp)
{
        uint32_t nidx;
        struct db_link *dlp;
        struct db_minor *dmp;

        assert(linkp->minor_path != NULL);

        dmp = lookup_minor(hdp, linkp->minor_path, NULL, TYPE_DB);

        /*
         * If a minor matching the path exists, walk that minor's devlinks list.
         * Then walk the dangling devlinks list. Non-matching devlinks will be
         * filtered out in visit_link.
         */
        for (;;) {
                nidx = dmp ? dmp->link : DB_HDR(hdp)->dngl_idx;
                for (; dlp = get_link(hdp, nidx); nidx = dlp->sib) {
                        struct di_devlink vlink = {NULL};

                        vlink.rel_path = get_string(hdp, dlp->path);
                        vlink.content = get_string(hdp, dlp->content);
                        vlink.type = attr2type(dlp->attr);

                        if (visit_link(hdp, linkp, &vlink) != DI_WALK_CONTINUE)
                                goto out;
                }
                if (dmp == NULL) {
                        break;
                } else {
                        dmp = NULL;
                }
        }

out:
        return (linkp->retval);
}

static int
visit_link(
        struct di_devlink_handle *hdp,
        link_desc_t *linkp,
        struct di_devlink *vlp)
{
        struct stat sbuf;
        const char *minor_path = NULL;
        char abs_path[PATH_MAX], cont[PATH_MAX];

        /*
         * It is legal for the link's content and type to be unknown.
         * but one of absolute or relative path must be set.
         */
        if (vlp->rel_path == NULL && vlp->abs_path == NULL) {
                (void) devlink_dprintf(DBG_ERR,
                    "visit_link: invalid arguments\n");
                return (DI_WALK_CONTINUE);
        }

        if (vlp->rel_path == NULL) {
                vlp->rel_path = (char *)rel_path(hdp, vlp->abs_path);
                if (vlp->rel_path == NULL || vlp->rel_path[0] == '\0')
                        return (DI_WALK_CONTINUE);
        }

        if (linkp->regp) {
                if (regexec(linkp->regp, vlp->rel_path, 0, NULL, 0) != 0)
                        return (DI_WALK_CONTINUE);
        }

        if (vlp->abs_path == NULL) {
                assert(vlp->rel_path[0] != '/');
                (void) snprintf(abs_path, sizeof (abs_path), "%s/%s",
                    hdp->dev_dir, vlp->rel_path);
                vlp->abs_path = abs_path;
        }

        if (vlp->content == NULL) {
                if (s_readlink(vlp->abs_path, cont, sizeof (cont)) < 0) {
                        return (DI_WALK_CONTINUE);
                }
                vlp->content = cont;
        }


        if (vlp->type == 0) {
                if (is_minor_node(vlp->content, &minor_path)) {
                        vlp->type = DI_PRIMARY_LINK;
                } else {
                        vlp->type = DI_SECONDARY_LINK;
                }
        }

        /*
         * Filter based on minor path
         */
        if (linkp->minor_path) {
                char tmp[PATH_MAX];

                /*
                 * derive minor path
                 */
                if (vlp->type == DI_SECONDARY_LINK) {

#ifdef  DEBUG
                        /*LINTED*/
                        assert(sizeof (tmp) >= PATH_MAX);
#endif
                        if (s_realpath(vlp->abs_path, tmp) == NULL)
                                return (DI_WALK_CONTINUE);

                        if (!is_minor_node(tmp, &minor_path))
                                return (DI_WALK_CONTINUE);

                } else if (minor_path == NULL) {
                        if (!is_minor_node(vlp->content, &minor_path))
                                return (DI_WALK_CONTINUE);
                }

                assert(minor_path != NULL);

                if (strcmp(linkp->minor_path, minor_path) != 0)
                        return (DI_WALK_CONTINUE);
        }

        /*
         * Filter based on link type
         */
        if (!TYPE_NONE(linkp->flags) && LINK_TYPE(linkp->flags) != vlp->type) {
                return (DI_WALK_CONTINUE);
        }

        if (lstat(vlp->abs_path, &sbuf) < 0) {
                devlink_dprintf(DBG_ERR, "visit_link: %s: lstat failed: %s\n",
                    vlp->abs_path, strerror(errno));
                return (DI_WALK_CONTINUE);
        }

        return (linkp->fcn(vlp, linkp->arg));
}

static int
devlink_valid(di_devlink_t devlink)
{
        if (devlink == NULL || devlink->rel_path == NULL ||
            devlink->abs_path == NULL || devlink->content == NULL ||
            TYPE_NONE(devlink->type)) {
                return (0);
        }

        return (1);
}

const char *
di_devlink_path(di_devlink_t devlink)
{
        if (!devlink_valid(devlink)) {
                errno = EINVAL;
                return (NULL);
        }

        return (devlink->abs_path);
}

const char *
di_devlink_content(di_devlink_t devlink)
{
        if (!devlink_valid(devlink)) {
                errno = EINVAL;
                return (NULL);
        }

        return (devlink->content);
}

int
di_devlink_type(di_devlink_t devlink)
{
        if (!devlink_valid(devlink)) {
                errno = EINVAL;
                return (-1);
        }

        return (devlink->type);
}

di_devlink_t
di_devlink_dup(di_devlink_t devlink)
{
        struct di_devlink *duplink;

        if (!devlink_valid(devlink)) {
                errno = EINVAL;
                return (NULL);
        }

        if ((duplink = calloc(1, sizeof (struct di_devlink))) == NULL) {
                return (NULL);
        }

        duplink->rel_path = strdup(devlink->rel_path);
        duplink->abs_path = strdup(devlink->abs_path);
        duplink->content  = strdup(devlink->content);
        duplink->type     = devlink->type;

        if (!devlink_valid(duplink)) {
                (void) di_devlink_free(duplink);
                errno = ENOMEM;
                return (NULL);
        }

        return (duplink);
}

int
di_devlink_free(di_devlink_t devlink)
{
        if (devlink == NULL) {
                errno = EINVAL;
                return (-1);
        }

        free(devlink->rel_path);
        free(devlink->abs_path);
        free(devlink->content);
        free(devlink);

        return (0);
}

/*
 * Obtain path relative to dev_dir
 */
static const char *
rel_path(struct di_devlink_handle *hdp, const char *path)
{
        const size_t len = strlen(hdp->dev_dir);

        if (strncmp(path, hdp->dev_dir, len) != 0)
                return (NULL);

        if (path[len] == '\0')
                return (&path[len]);

        if (path[len] != '/')
                return (NULL);

        return (&path[len+1]);
}

static int
recurse_dev(struct di_devlink_handle *hdp, recurse_t *rp)
{
        int ret = 0;

        (void) do_recurse(hdp->dev_dir, hdp, rp, &ret);

        return (ret);
}

static int
do_recurse(
        const char *dir,
        struct di_devlink_handle *hdp,
        recurse_t *rp,
        int *retp)
{
        size_t len;
        const char *rel;
        struct stat sbuf;
        char cur[PATH_MAX], *cp;
        int i, rv = DI_WALK_CONTINUE;
        finddevhdl_t handle;
        char *d_name;


        if ((rel = rel_path(hdp, dir)) == NULL)
                return (DI_WALK_CONTINUE);

        /*
         * Skip directories we are not interested in.
         */
        for (i = 0; i < N_SKIP_DIRS; i++) {
                if (strcmp(rel, skip_dirs[i]) == 0) {
                        (void) devlink_dprintf(DBG_STEP,
                            "do_recurse: skipping %s\n", dir);
                        return (DI_WALK_CONTINUE);
                }
        }

        (void) devlink_dprintf(DBG_STEP, "do_recurse: dir = %s\n", dir);

        if (finddev_readdir(dir, &handle) != 0)
                return (DI_WALK_CONTINUE);

        (void) snprintf(cur, sizeof (cur), "%s/", dir);
        len = strlen(cur);
        cp = cur + len;
        len = sizeof (cur) - len;

        for (;;) {
                if ((d_name = (char *)finddev_next(handle)) == NULL)
                        break;

                if (strlcpy(cp, d_name, len) >= len)
                        break;

                /*
                 * Skip files we are not interested in.
                 */
                for (i = 0; i < N_SKIP_FILES; i++) {

                        rel = rel_path(hdp, cur);
                        if (rel == NULL || strcmp(rel, skip_files[i]) == 0) {
                                (void) devlink_dprintf(DBG_STEP,
                                    "do_recurse: skipping %s\n", cur);
                                goto next_entry;
                        }
                }

                if (lstat(cur, &sbuf) == 0) {
                        if (S_ISDIR(sbuf.st_mode)) {
                                rv = do_recurse(cur, hdp, rp, retp);
                        } else if (S_ISLNK(sbuf.st_mode)) {
                                rv = rp->fcn(hdp, rp->data, cur);
                        } else {
                                (void) devlink_dprintf(DBG_STEP,
                                    "do_recurse: Skipping entry: %s\n", cur);
                        }
                } else {
                        (void) devlink_dprintf(DBG_ERR,
                            "do_recurse: cur(%s): lstat failed: %s\n",
                            cur, strerror(errno));
                }

next_entry:
                *cp = '\0';

                if (rv != DI_WALK_CONTINUE)
                        break;
        }

        finddev_close(handle);

        return (rv);
}


static int
check_attr(uint32_t attr)
{
        switch (attr & A_LINK_TYPES) {
                case A_PRIMARY:
                case A_SECONDARY:
                        return (1);
                default:
                        devlink_dprintf(DBG_ERR,
                            "check_attr: incorrect attr(%u)\n", attr);
                        return (0);
        }
}

static int
attr2type(uint32_t attr)
{
        switch (attr & A_LINK_TYPES) {
                case A_PRIMARY:
                        return (DI_PRIMARY_LINK);
                case A_SECONDARY:
                        return (DI_SECONDARY_LINK);
                default:
                        devlink_dprintf(DBG_ERR,
                            "attr2type: incorrect attr(%u)\n", attr);
                        return (0);
        }
}

/* Allocate new node and link it in */
static cache_node_t *
node_insert(
        struct di_devlink_handle *hdp,
        cache_node_t *pcnp,
        const char *path,
        int insert)
{
        cache_node_t *cnp;

        if (path == NULL) {
                errno = EINVAL;
                SET_DB_ERR(hdp);
                return (NULL);
        }

        if ((cnp = calloc(1, sizeof (cache_node_t))) == NULL) {
                SET_DB_ERR(hdp);
                return (NULL);
        }

        if ((cnp->path = strdup(path)) == NULL) {
                SET_DB_ERR(hdp);
                free(cnp);
                return (NULL);
        }

        cnp->parent = pcnp;

        if (pcnp == NULL) {
                assert(strcmp(path, "/") == 0);
                assert(CACHE(hdp)->root == NULL);
                CACHE(hdp)->root = cnp;
        } else if (insert == INSERT_HEAD) {
                cnp->sib = pcnp->child;
                pcnp->child = cnp;
        } else if (CACHE_LAST(hdp) && CACHE_LAST(hdp)->node &&
            CACHE_LAST(hdp)->node->parent == pcnp &&
            CACHE_LAST(hdp)->node->sib == NULL) {

                CACHE_LAST(hdp)->node->sib = cnp;

        } else {
                cache_node_t **pp;

                for (pp = &pcnp->child; *pp != NULL; pp = &(*pp)->sib)
                        ;
                *pp = cnp;
        }

        return (cnp);
}

/*
 * Allocate a new minor and link it in either at the tail or head
 * of the minor list depending on the value of "prev".
 */
static cache_minor_t *
minor_insert(
        struct di_devlink_handle *hdp,
        cache_node_t *pcnp,
        const char *name,
        const char *nodetype,
        cache_minor_t **prev)
{
        cache_minor_t *cmnp;

        if (pcnp == NULL || name == NULL) {
                errno = EINVAL;
                SET_DB_ERR(hdp);
                return (NULL);
        }

        /*
         * Some pseudo drivers don't specify nodetype. Assume pseudo if
         * nodetype is not specified.
         */
        if (nodetype == NULL)
                nodetype = DDI_PSEUDO;

        if ((cmnp = calloc(1, sizeof (cache_minor_t))) == NULL) {
                SET_DB_ERR(hdp);
                return (NULL);
        }

        cmnp->name = strdup(name);
        cmnp->nodetype = strdup(nodetype);
        if (cmnp->name == NULL || cmnp->nodetype == NULL) {
                SET_DB_ERR(hdp);
                free(cmnp->name);
                free(cmnp->nodetype);
                free(cmnp);
                return (NULL);
        }

        cmnp->node = pcnp;

        /* Add to node's minor list */
        if (prev == NULL) {
                cmnp->sib = pcnp->minor;
                pcnp->minor = cmnp;
        } else {
                assert(*prev == NULL);
                *prev = cmnp;
        }

        return (cmnp);
}

static cache_link_t *
link_insert(
        struct di_devlink_handle *hdp,
        cache_minor_t *cmnp,
        const char *path,
        const char *content,
        uint32_t attr)
{
        cache_link_t *clp;

        if (path == NULL || content == NULL || !check_attr(attr)) {
                errno = EINVAL;
                SET_DB_ERR(hdp);
                return (NULL);
        }

        if ((clp = calloc(1, sizeof (cache_link_t))) == NULL) {
                SET_DB_ERR(hdp);
                return (NULL);
        }

        clp->path = strdup(path);
        clp->content = strdup(content);
        if (clp->path == NULL || clp->content == NULL) {
                SET_DB_ERR(hdp);
                link_free(&clp);
                return (NULL);
        }

        clp->attr = attr;
        hash_insert(hdp, clp);
        clp->minor = cmnp;

        /* Add to minor's link list */
        if (cmnp != NULL) {
                clp->sib = cmnp->link;
                cmnp->link = clp;
        } else {
                clp->sib = CACHE(hdp)->dngl;
                CACHE(hdp)->dngl = clp;
        }

        return (clp);
}

static void
hash_insert(struct di_devlink_handle *hdp, cache_link_t *clp)
{
        uint_t hval;

        hval = hashfn(hdp, clp->path);
        clp->hash = CACHE_HASH(hdp, hval);
        CACHE_HASH(hdp, hval) = clp;
}


static struct db_node *
get_node(struct di_devlink_handle *hdp, uint32_t idx)
{
        return (map_seg(hdp, idx, PROT_READ, DB_NODE));
}

static struct db_node *
set_node(struct di_devlink_handle *hdp, uint32_t idx)
{
        return (map_seg(hdp, idx, PROT_READ | PROT_WRITE, DB_NODE));
}

static struct db_minor *
get_minor(struct di_devlink_handle *hdp, uint32_t idx)
{
        return (map_seg(hdp, idx, PROT_READ, DB_MINOR));
}

static struct db_minor *
set_minor(struct di_devlink_handle *hdp, uint32_t idx)
{
        return (map_seg(hdp, idx, PROT_READ | PROT_WRITE, DB_MINOR));
}

static struct db_link *
get_link(struct di_devlink_handle *hdp, uint32_t idx)
{
        return (map_seg(hdp, idx, PROT_READ, DB_LINK));
}

static struct db_link *
set_link(struct di_devlink_handle *hdp, uint32_t idx)
{
        return (map_seg(hdp, idx, PROT_READ | PROT_WRITE, DB_LINK));
}

static char *
get_string(struct di_devlink_handle *hdp, uint32_t idx)
{
        return (map_seg(hdp, idx, PROT_READ, DB_STR));
}

static char *
set_string(struct di_devlink_handle *hdp, uint32_t idx)
{
        return (map_seg(hdp, idx, PROT_READ | PROT_WRITE, DB_STR));
}


/*
 * Returns the element corresponding to idx. If the portion of file involved
 * is not yet mapped, does an mmap() as well. Existing mappings are not changed.
 */
static void *
map_seg(
        struct di_devlink_handle *hdp,
        uint32_t idx,
        int prot,
        db_seg_t seg)
{
        int s;
        off_t off;
        size_t slen;
        caddr_t addr;

        if (idx == DB_NIL) {
                return (NULL);
        }

        if (!VALID_INDEX(hdp, seg, idx)) {
                (void) devlink_dprintf(DBG_ERR,
                    "map_seg: seg(%d): invalid idx(%u)\n", seg, idx);
                return (NULL);
        }

        /*
         * If the seg is already mapped in, use it if the access type is
         * valid.
         */
        if (DB_SEG(hdp, seg) != NULL) {
                if (DB_SEG_PROT(hdp, seg) != prot) {
                        (void) devlink_dprintf(DBG_ERR,
                            "map_seg: illegal access: "
                            "seg[%d]: idx=%u, seg_prot=%d, access=%d\n",
                            seg, idx, DB_SEG_PROT(hdp, seg), prot);
                        return (NULL);
                }
                return (DB_SEG(hdp, seg) + idx * elem_sizes[seg]);
        }

        /*
         * Segment is not mapped. Mmap() the segment.
         */
        off = seg_size(hdp, DB_HEADER);
        for (s = 0; s < seg; s++) {
                off += seg_size(hdp, s);
        }
        slen = seg_size(hdp, seg);

        addr = mmap(0, slen, prot, MAP_SHARED, DB(hdp)->db_fd, off);
        if (addr == MAP_FAILED) {
                (void) devlink_dprintf(DBG_ERR,
                    "map_seg: seg[%d]: mmap failed: %s\n", seg,
                    strerror(errno));
                (void) devlink_dprintf(DBG_ERR,
                    "map_seg: args: len=%lu, prot=%d, fd=%d, off=%ld\n",
                    (ulong_t)slen, prot, DB(hdp)->db_fd, off);
                return (NULL);
        }

        DB_SEG(hdp, seg) = addr;
        DB_SEG_PROT(hdp, seg) = prot;

        (void) devlink_dprintf(DBG_STEP, "map_seg: seg[%d]: len=%lu, prot=%d, "
            "fd=%d, off=%ld, seg_base=%p\n", seg, (ulong_t)slen, prot,
            DB(hdp)->db_fd, off, (void *)addr);

        return (DB_SEG(hdp, seg) + idx * elem_sizes[seg]);
}

/*
 * Computes the size of a segment rounded up to the nearest page boundary.
 */
static size_t
seg_size(struct di_devlink_handle *hdp, int seg)
{
        size_t sz;

        assert(DB_HDR(hdp)->page_sz);

        if (seg == DB_HEADER) {
                sz = HDR_LEN;
        } else {
                assert(DB_NUM(hdp, seg) >= 1);
                sz = DB_NUM(hdp, seg) * elem_sizes[seg];
        }

        sz = (sz / DB_HDR(hdp)->page_sz) + 1;

        sz *= DB_HDR(hdp)->page_sz;

        return (sz);
}

static size_t
size_db(struct di_devlink_handle *hdp, long page_sz, uint32_t *count)
{
        int i;
        size_t sz;
        cache_link_t *clp;

        assert(page_sz > 0);

        /* Take "NIL" element into account */
        for (i = 0; i < DB_TYPES; i++) {
                count[i] = 1;
        }

        count_node(CACHE(hdp)->root, count);

        for (clp = CACHE(hdp)->dngl; clp != NULL; clp = clp->sib) {
                count_link(clp, count);
        }

        sz = ((HDR_LEN / page_sz) + 1) * page_sz;
        for (i = 0; i < DB_TYPES; i++) {
                assert(count[i] >= 1);
                sz += (((count[i] * elem_sizes[i]) / page_sz) + 1) * page_sz;
                (void) devlink_dprintf(DBG_INFO, "N[%u]=%u\n", i, count[i]);
        }
        (void) devlink_dprintf(DBG_INFO, "DB size=%lu\n", (ulong_t)sz);

        return (sz);
}


static void
count_node(cache_node_t *cnp, uint32_t *count)
{
        cache_minor_t *cmnp;

        if (cnp == NULL)
                return;

        count[DB_NODE]++;
        count_string(cnp->path, count);

        for (cmnp = cnp->minor; cmnp != NULL; cmnp = cmnp->sib) {
                count_minor(cmnp, count);
        }

        for (cnp = cnp->child; cnp != NULL; cnp = cnp->sib) {
                count_node(cnp, count);
        }

}

static void
count_minor(cache_minor_t *cmnp, uint32_t *count)
{
        cache_link_t *clp;

        if (cmnp == NULL)
                return;

        count[DB_MINOR]++;
        count_string(cmnp->name, count);
        count_string(cmnp->nodetype, count);

        for (clp = cmnp->link; clp != NULL; clp = clp->sib) {
                count_link(clp, count);
        }
}

static void
count_link(cache_link_t *clp, uint32_t *count)
{
        if (clp == NULL)
                return;

        count[DB_LINK]++;
        count_string(clp->path, count);
        count_string(clp->content, count);
}


static void
count_string(const char *str, uint32_t *count)
{
        if (str == NULL) {
                (void) devlink_dprintf(DBG_ERR,
                    "count_string: NULL argument\n");
                return;
        }

        count[DB_STR] += strlen(str) + 1;
}

static uint_t
hashfn(struct di_devlink_handle *hdp, const char *str)
{
        const char *cp;
        ulong_t hval = 0;

        if (str == NULL) {
                return (0);
        }

        assert(CACHE(hdp)->hash_sz >= MIN_HASH_SIZE);

        for (cp = str; *cp != '\0'; cp++) {
                hval += *cp;
        }

        return (hval % CACHE(hdp)->hash_sz);
}

/*
 * enter_db_lock()
 *
 * If the handle is IS_RDWR then we lock as writer to "update" database,
 * if IS_RDONLY then we lock as reader to "snapshot" database. The
 * implementation uses advisory file locking.
 *
 * This function returns:
 *   == 1       success and grabbed the lock file, we can open the DB.
 *   == 0       success but did not lock the lock file, reader must walk
 *              the /dev directory.
 *   == -1      failure.
 */
static int
enter_db_lock(struct di_devlink_handle *hdp, const char *root_dir)
{
        int             fd;
        struct flock    lock;
        char            lockfile[PATH_MAX];
        int             rv;
        int             writer = HDL_RDWR(hdp);
        static int      did_sync = 0;
        int             eintrs;

        assert(hdp->lock_fd < 0);

        get_db_path(hdp, DB_LOCK, lockfile, sizeof (lockfile));

        devlink_dprintf(DBG_LCK, "enter_db_lock: %s BEGIN\n",
            writer ? "update" : "snapshot");

        /* Record locks are per-process. Protect against multiple threads. */
        (void) mutex_lock(&update_mutex);

again:  if ((fd = open(lockfile,
            (writer ? (O_RDWR|O_CREAT) : O_RDONLY), DB_LOCK_PERMS)) < 0) {
                /*
                 * Typically the lock file and the database go hand in hand.
                 * If we find that the lock file does not exist (for some
                 * unknown reason) and we are the reader then we return
                 * success (after triggering devfsadm to create the file and
                 * a retry) so that we can still provide service via slow
                 * /dev walk.  If we get a failure as a writer we want the
                 * error to manifests itself.
                 */
                if ((errno == ENOENT) && !writer) {
                        /* If reader, signal once to get files created */
                        if (did_sync == 0) {
                                did_sync = 1;
                                devlink_dprintf(DBG_LCK,
                                    "enter_db_lock: %s OSYNC\n",
                                    writer ? "update" : "snapshot");

                                /* signal to get files created */
                                (void) devlink_create(root_dir, NULL,
                                    DCA_DEVLINK_SYNC);
                                goto again;
                        }
                        devlink_dprintf(DBG_LCK,
                            "enter_db_lock: %s OPENFAILD %s: WALK\n",
                            writer ? "update" : "snapshot", strerror(errno));
                        (void) mutex_unlock(&update_mutex);
                        return (0);             /* success, but not locked */
                } else {
                        devlink_dprintf(DBG_LCK,
                            "enter_db_lock: %s OPENFAILD %s\n",
                            writer ? "update" : "snapshot", strerror(errno));
                        (void) mutex_unlock(&update_mutex);
                        return (-1);            /* failed */
                }
        }

        lock.l_type = writer ? F_WRLCK : F_RDLCK;
        lock.l_whence = SEEK_SET;
        lock.l_start = 0;
        lock.l_len = 0;

        /* Enter the lock. */
        for (eintrs = 0; eintrs < MAX_LOCK_RETRY; eintrs++) {
                rv = fcntl(fd, F_SETLKW, &lock);
                if ((rv != -1) || (errno != EINTR))
                        break;
        }

        if (rv != -1) {
                hdp->lock_fd = fd;
                devlink_dprintf(DBG_LCK, "enter_db_lock: %s LOCKED\n",
                    writer ? "update" : "snapshot");
                return (1);             /* success, locked */
        }

        (void) close(fd);
        devlink_dprintf(DBG_ERR, "enter_db_lock: %s FAILED: %s: WALK\n",
            writer ? "update" : "snapshot", strerror(errno));
        (void) mutex_unlock(&update_mutex);
        return (-1);
}

/*
 * Close and re-open lock file every time so that it is recreated if deleted.
 */
static void
exit_db_lock(struct di_devlink_handle *hdp)
{
        struct flock    unlock;
        int             writer = HDL_RDWR(hdp);

        if (hdp->lock_fd < 0) {
                return;
        }

        unlock.l_type = F_UNLCK;
        unlock.l_whence = SEEK_SET;
        unlock.l_start = 0;
        unlock.l_len = 0;

        devlink_dprintf(DBG_LCK, "exit_db_lock : %s UNLOCKED\n",
            writer ? "update" : "snapshot");
        if (fcntl(hdp->lock_fd, F_SETLK, &unlock) == -1) {
                devlink_dprintf(DBG_ERR, "exit_db_lock : %s failed: %s\n",
                    writer ? "update" : "snapshot", strerror(errno));
        }

        (void) close(hdp->lock_fd);

        hdp->lock_fd = -1;

        (void) mutex_unlock(&update_mutex);
}

/*
 * returns 1 if contents is a minor node in /devices.
 * If mn_root is not NULL, mn_root is set to:
 *      if contents is a /dev node, mn_root = contents
 *                      OR
 *      if contents is a /devices node, mn_root set to the '/'
 *      following /devices.
 */
int
is_minor_node(const char *contents, const char **mn_root)
{
        char *ptr, *prefix;

        prefix = "../devices/";

        if ((ptr = strstr(contents, prefix)) != NULL) {

                /* mn_root should point to the / following /devices */
                if (mn_root != NULL) {
                        *mn_root = ptr += strlen(prefix) - 1;
                }
                return (1);
        }

        prefix = "/devices/";

        if (strncmp(contents, prefix, strlen(prefix)) == 0) {

                /* mn_root should point to the / following /devices/ */
                if (mn_root != NULL) {
                        *mn_root = contents + strlen(prefix) - 1;
                }
                return (1);
        }

        if (mn_root != NULL) {
                *mn_root = contents;
        }
        return (0);
}

static int
s_readlink(const char *link, char *buf, size_t blen)
{
        int rv;

        if ((rv = readlink(link, buf, blen)) == -1)
                goto bad;

        if (rv >= blen && buf[blen - 1] != '\0') {
                errno = ENAMETOOLONG;
                goto bad;
        } else if (rv < blen) {
                buf[rv] = '\0';
        }

        return (0);
bad:
        devlink_dprintf(DBG_ERR, "s_readlink: %s: failed: %s\n",
            link, strerror(errno));
        return (-1);
}

/*
 * Synchronous link creation interface routines
 * The scope of the operation is determined by the "name" arg.
 * "name" can be NULL, a driver name or a devfs pathname (without /devices)
 *
 *      "name"                          creates
 *      ======                          =======
 *
 *      NULL            =>              All devlinks in system
 *      <driver>        =>              devlinks for named driver
 *      /pci@1          =>              devlinks for subtree rooted at pci@1
 *      /pseudo/foo@0:X =>              devlinks for minor X
 *
 * devlink_create() returns 0 on success or an errno value on failure
 */

#define MAX_DAEMON_ATTEMPTS 2

static int
devlink_create(const char *root, const char *name, int dca_devlink_flag)
{
        int i;
        int install;
        struct dca_off dca;

        assert(root);

        /*
         * Convert name into arg for door_call
         */
        if (dca_init(name, &dca, dca_devlink_flag) != 0)
                return (EINVAL);

        /*
         * Attempt to use the daemon first
         */
        i = 0;
        do {
                install = daemon_call(root, &dca);

                devlink_dprintf(DBG_INFO, "daemon_call() retval=%d\n",
                    dca.dca_error);

                /*
                 * Retry only if door server isn't running
                 */
                if (dca.dca_error != ENOENT && dca.dca_error != EBADF) {
                        return (dca.dca_error);
                }

                dca.dca_error = 0;

                /*
                 * To improve performance defer this check until the first
                 * failure. Safe to defer as door server checks perms.
                 */
                if (geteuid() != 0)
                        return (EPERM);
        /*
         * Daemon may not be running. Try to start it.
         */
        } while ((++i < MAX_DAEMON_ATTEMPTS) &&
            start_daemon(root, install) == 0);

        devlink_dprintf(DBG_INFO, "devlink_create: can't start daemon\n");

        assert(dca.dca_error == 0);

        /*
         * If the daemon cannot be started execute the devfsadm command.
         */
        exec_cmd(root, &dca);

        return (dca.dca_error);
}

/*
 * The "name" member of "struct dca" contains data in the following order
 *      root'\0'minor'\0'driver'\0'
 * The root component is always present at offset 0 in the "name" field.
 * The driver and minor are optional. If present they have a non-zero
 * offset in the "name" member.
 */
static int
dca_init(const char *name, struct dca_off *dcp, int dca_flags)
{
        char *cp;

        dcp->dca_root = 0;
        dcp->dca_minor = 0;
        dcp->dca_driver = 0;
        dcp->dca_error = 0;
        dcp->dca_flags = dca_flags;
        dcp->dca_name[0] = '\0';

        name = name ? name : "/";

        /*
         *  Check if name is a driver name
         */
        if (*name != '/') {
                (void) snprintf(dcp->dca_name, sizeof (dcp->dca_name),
                    "/ %s", name);
                dcp->dca_root = 0;
                *(dcp->dca_name + 1) = '\0';
                dcp->dca_driver = 2;
                return (0);
        }

        (void) snprintf(dcp->dca_name, sizeof (dcp->dca_name), "%s", name);

        /*
         * "/devices" not allowed in devfs pathname
         */
        if (is_minor_node(name, NULL))
                return (-1);

        dcp->dca_root = 0;
        if (cp = strrchr(dcp->dca_name, ':')) {
                *cp++ = '\0';
                dcp->dca_minor = cp - dcp->dca_name;
        }

        return (0);
}


#define DAEMON_STARTUP_TIME     1 /* 1 second. This may need to be adjusted */
#define DEVNAME_CHECK_FILE      "/etc/devname_check_RDONLY"

static int
daemon_call(const char *root, struct dca_off *dcp)
{
        door_arg_t      arg;
        int             fd, door_error;
        sigset_t        oset, nset;
        char            synch_door[PATH_MAX];
        struct stat     sb;
        char            *prefix;
        int             rofd;
        int             rdonly;
        int             install = 0;

        /*
         * If root is readonly, there are two possibilities:
         *      - we are in some sort of install scenario
         *      - we are early in boot
         * If the latter we don't want daemon_call()  to succeed.
         * else we want to use /tmp/etc/dev
         *
         * Both of these requrements are fulfilled if we check for
         * for a root owned door file in /tmp/etc/dev. If we are
         * early in boot, the door file won't exist, so this call
         * will fail.
         *
         * If we are in install, the door file will be present.
         *
         * If root is read-only, try only once, since libdevinfo
         * isn't capable of starting devfsadmd correctly in that
         * situation.
         *
         * Don't use statvfs() to check for readonly roots since it
         * doesn't always report the truth.
         */
        rofd = -1;
        rdonly = 0;
        if ((rofd = open(DEVNAME_CHECK_FILE, O_WRONLY|O_CREAT|O_TRUNC, 0644))
            == -1 && errno == EROFS) {
                rdonly = 1;
                prefix = "/tmp";
        } else {
                if (rofd != -1) {
                        (void) close(rofd);
                        (void) unlink(DEVNAME_CHECK_FILE);
                }
                prefix = (char *)root;
        }

        if (rdonly && stat(DEVNAME_CHECK_FILE, &sb) != -1)
                install = 1;

        (void) snprintf(synch_door, sizeof (synch_door),
            "%s/etc/dev/%s", prefix, DEVFSADM_SYNCH_DOOR);

        /*
         * Return ENOTSUP to prevent retries if root is readonly
         */
        if (stat(synch_door, &sb) == -1 || sb.st_uid != 0) {
                if (rdonly)
                        dcp->dca_error = ENOTSUP;
                else
                        dcp->dca_error = ENOENT;
                devlink_dprintf(DBG_ERR,
                    "stat failed: %s: no file or not root owned\n", synch_door);
                return (install);
        }

        if ((fd = open(synch_door, O_RDONLY)) == -1) {
                dcp->dca_error = errno;
                devlink_dprintf(DBG_ERR, "open of %s failed: %s\n",
                    synch_door, strerror(errno));
                return (install);
        }

        arg.data_ptr = (char *)dcp;
        arg.data_size = sizeof (*dcp);
        arg.desc_ptr = NULL;
        arg.desc_num = 0;
        arg.rbuf = (char *)dcp;
        arg.rsize = sizeof (*dcp);

        /*
         * Block signals to this thread until door call
         * completes.
         */
        (void) sigfillset(&nset);
        (void) sigemptyset(&oset);
        (void) sigprocmask(SIG_SETMASK, &nset, &oset);
        if (door_call(fd, &arg)) {
                door_error = 1;
                dcp->dca_error = errno;
        }
        (void) sigprocmask(SIG_SETMASK, &oset, NULL);

        (void) close(fd);

        if (door_error)
                return (install);

        assert(arg.data_ptr);

        /*LINTED*/
        dcp->dca_error = ((struct dca_off *)arg.data_ptr)->dca_error;

        /*
         * The doors interface may return data in a different buffer
         * If that happens, deallocate buffer via munmap()
         */
        if (arg.rbuf != (char *)dcp)
                (void) munmap(arg.rbuf, arg.rsize);

        return (install);
}

#define DEVFSADM_PATH   "/usr/sbin/devfsadm"
#define DEVFSADM        "devfsadm"

#define DEVFSADMD_PATH  "/usr/lib/devfsadm/devfsadmd"
#define DEVFSADM_DAEMON "devfsadmd"

static int
start_daemon(const char *root, int install)
{
        int rv, i = 0;
        char *argv[20];

        argv[i++] = DEVFSADM_DAEMON;
        if (install) {
                argv[i++] = "-a";
                argv[i++] = "/tmp";
                argv[i++] = "-p";
                argv[i++] = "/tmp/root/etc/path_to_inst";
        } else if (strcmp(root, "/")) {
                argv[i++] = "-r";
                argv[i++] = (char *)root;
        }
        argv[i++] = NULL;

        rv = do_exec(DEVFSADMD_PATH, argv);

        (void) sleep(DAEMON_STARTUP_TIME);

        return (rv);
}

static void
exec_cmd(const char *root, struct dca_off *dcp)
{
        int i;
        char *argv[20];

        i = 0;
        argv[i++] = DEVFSADM;

        /*
         * Load drivers only if -i is specified
         */
        if (dcp->dca_driver) {
                argv[i++] = "-i";
                argv[i++] = &dcp->dca_name[dcp->dca_driver];
        } else {
                argv[i++] = "-n";
        }

        if (root != NULL && strcmp(root, "/") != 0) {
                argv[i++] = "-r";
                argv[i++] = (char *)root;
        }

        argv[i] = NULL;

        if (do_exec(DEVFSADM_PATH, argv))
                dcp->dca_error = errno;
}

static int
do_exec(const char *path, char *const argv[])
{
        int i;
        pid_t cpid;

#ifdef  DEBUG
        devlink_dprintf(DBG_INFO, "Executing %s\n\tArgument list:", path);
        for (i = 0; argv[i] != NULL; i++) {
                devlink_dprintf(DBG_INFO, " %s", argv[i]);
        }
        devlink_dprintf(DBG_INFO, "\n");
#endif

        if ((cpid = fork1()) == -1) {
                devlink_dprintf(DBG_ERR, "fork1 failed: %s\n", strerror(errno));
                return (-1);
        }

        if (cpid == 0) { /* child process */
                int fd;

                if ((fd = open("/dev/null", O_RDWR)) >= 0) {
                        (void) dup2(fd, fileno(stdout));
                        (void) dup2(fd, fileno(stderr));
                        (void) close(fd);

                        (void) execv(path, argv);
                } else {
                        devlink_dprintf(DBG_ERR,
                            "open of /dev/null failed: %s\n", strerror(errno));
                }

                _exit(-1);
        }

        /* Parent process */
        if (waitpid(cpid, &i, 0) == cpid) {
                if (WIFEXITED(i)) {
                        if (WEXITSTATUS(i) == 0) {
                                devlink_dprintf(DBG_STEP,
                                    "do_exec: child exited normally\n");
                                return (0);
                        } else
                                errno = EINVAL;
                } else {
                        /*
                         * The child was interrupted by a signal
                         */
                        errno = EINTR;
                }
                devlink_dprintf(DBG_ERR, "child terminated abnormally: %s\n",
                    strerror(errno));
        } else {
                devlink_dprintf(DBG_ERR, "waitpid failed: %s\n",
                    strerror(errno));
        }

        return (-1);
}

static int
walk_cache_links(di_devlink_handle_t hdp, cache_link_t *clp, link_desc_t *linkp)
{
        int i;

        assert(HDL_RDWR(hdp) || HDL_RDONLY(hdp));

        devlink_dprintf(DBG_INFO, "walk_cache_links: initial link: %s\n",
            clp ? clp->path : "<NULL>");

        /*
         * First search the links under the specified minor. On the
         * 2nd pass, search the dangling list - secondary links may
         * exist on this list since they are not resolved during the
         * /dev walk.
         */
        for (i = 0; i < 2; i++) {
                for (; clp != NULL; clp = clp->sib) {
                        struct di_devlink vlink = {NULL};

                        assert(clp->path[0] != '/');

                        vlink.rel_path = clp->path;
                        vlink.content = clp->content;
                        vlink.type = attr2type(clp->attr);

                        if (visit_link(hdp, linkp, &vlink)
                            != DI_WALK_CONTINUE) {
                                devlink_dprintf(DBG_INFO, "walk_cache_links: "
                                    "terminating at link: %s\n", clp->path);
                                goto out;
                        }
                }

                clp = CACHE(hdp)->dngl;
        }

out:

        /* If i < 2, we terminated the walk prematurely */
        return (i < 2 ? DI_WALK_TERMINATE : DI_WALK_CONTINUE);
}

static void
walk_all_cache(di_devlink_handle_t hdp, link_desc_t *linkp)
{
        int i;
        cache_link_t *clp;

        devlink_dprintf(DBG_INFO, "walk_all_cache: entered\n");

        for (i = 0; i < CACHE(hdp)->hash_sz; i++) {
                clp = CACHE_HASH(hdp, i);
                for (; clp; clp = clp->hash) {
                        struct di_devlink vlink = {NULL};

                        assert(clp->path[0] != '/');

                        vlink.rel_path = clp->path;
                        vlink.content = clp->content;
                        vlink.type = attr2type(clp->attr);
                        if (visit_link(hdp, linkp, &vlink) !=
                            DI_WALK_CONTINUE) {
                                devlink_dprintf(DBG_INFO, "walk_all_cache: "
                                    "terminating walk at link: %s\n",
                                    clp->path);
                                return;
                        }
                }
        }
}

static void
walk_cache_minor(di_devlink_handle_t hdp, const char *mpath, link_desc_t *linkp)
{
        cache_minor_t *cmnp;

        assert(mpath);

        if ((cmnp = lookup_minor(hdp, mpath, NULL, TYPE_CACHE)) != NULL) {
                (void) walk_cache_links(hdp, cmnp->link, linkp);
        } else {
                devlink_dprintf(DBG_ERR, "lookup minor failed: %s\n", mpath);
        }
}

static void
walk_cache_node(di_devlink_handle_t hdp, const char *path, link_desc_t *linkp)
{
        cache_minor_t *cmnp;
        cache_node_t *cnp;

        assert(path);

        if ((cnp = lookup_node(hdp, (char *)path, TYPE_CACHE)) == NULL) {
                devlink_dprintf(DBG_ERR, "lookup node failed: %s\n", path);
                return;
        }

        for (cmnp = cnp->minor; cmnp != NULL; cmnp = cmnp->sib) {
                if (walk_cache_links(hdp, cmnp->link, linkp)
                    == DI_WALK_TERMINATE)
                        break;
        }
}

/*
 * Private function
 *
 * Walk cached links corresponding to the given path.
 *
 * path         path to a node or minor node.
 *
 * flags        specifies the type of devlinks to be selected.
 *              If DI_PRIMARY_LINK is used, only primary links are selected.
 *              If DI_SECONDARY_LINK is specified, only secondary links
 *              are selected.
 *              If neither flag is specified, all devlinks are selected.
 *
 * re           An extended regular expression in regex(7) format which
 *              selects the /dev links to be returned. The regular
 *              expression should use link pathnames relative to
 *              /dev. i.e. without the leading "/dev/" prefix.
 *              A NULL value matches all devlinks.
 */
int
di_devlink_cache_walk(di_devlink_handle_t hdp,
    const char *re,
    const char *path,
    uint_t flags,
    void *arg,
    int (*devlink_callback)(di_devlink_t, void *))
{
        regex_t reg;
        link_desc_t linkd = {NULL};

        if (hdp == NULL || path == NULL || !link_flag(flags) ||
            !HDL_RDWR(hdp) || devlink_callback == NULL) {
                errno = EINVAL;
                return (-1);
        }

        linkd.flags = flags;
        linkd.arg = arg;
        linkd.fcn = devlink_callback;

        if (re) {
                if (regcomp(&reg, re, REG_EXTENDED) != 0)
                        return (-1);
                linkd.regp = &reg;
        }

        if (minor_colon(path) == NULL) {
                walk_cache_node(hdp, path, &linkd);
        } else {
                walk_cache_minor(hdp, path, &linkd);
        }

        if (re)
                regfree(&reg);

        return (0);
}

#define DEBUG_ENV_VAR   "_DEVLINK_DEBUG"
static int _devlink_debug = -1;

/*
 * debug level is initialized to -1.
 * On first call into this routine, debug level is set.
 * If debug level is zero, debugging msgs are disabled.
 */
static void
debug_print(debug_level_t msglevel, const char *fmt, va_list ap)
{
        char    *cp;
        int     save;

        /*
         * We shouldn't be here if debug is disabled
         */
        assert(_devlink_debug != 0);

        /*
         * Set debug level on first call into this routine
         */
        if (_devlink_debug < 0) {
                if ((cp = getenv(DEBUG_ENV_VAR)) == NULL) {
                        _devlink_debug = 0;
                        return;
                }

                save = errno;
                errno = 0;
                _devlink_debug = strtol(cp, NULL, 10);
                if (errno != 0 || _devlink_debug < 0)  {
                        _devlink_debug = 0;
                        errno = save;
                        return;
                }
                errno = save;

                if (!_devlink_debug)
                        return;
        }

        /* debug msgs are enabled */
        assert(_devlink_debug > 0);

        if (_devlink_debug < msglevel)
                return;
        if ((_devlink_debug == DBG_LCK) && (msglevel != _devlink_debug))
                return;

        /* Print a distinctive label for error msgs */
        if (msglevel == DBG_ERR) {
                (void) fprintf(stderr, "[ERROR]: ");
        }

        (void) vfprintf(stderr, fmt, ap);
        (void) fflush(stderr);
}

/* ARGSUSED */
/* PRINTFLIKE2 */
void
devlink_dprintf(debug_level_t msglevel, const char *fmt, ...)
{
        va_list ap;

        assert(msglevel > 0);
        if (!_devlink_debug)
                return;

        va_start(ap, fmt);
        debug_print(msglevel, fmt, ap);
        va_end(ap);
}