common/os/modsubr.c

	modsubr.c revision 7730e2acd408d8c08610e39353747d95fe743bce
/*
 * 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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/param.h>
#include <sys/modctl.h>
#include <sys/modhash.h>
#include <sys/open.h>
#include <sys/conf.h>
#include <sys/errno.h>
#include <sys/sysmacros.h>
#include <sys/kmem.h>
#include <sys/cmn_err.h>
#include <sys/stat.h>
#include <sys/mode.h>
#include <sys/pathname.h>
#include <sys/vnode.h>
#include <sys/ddi_impldefs.h>
#include <sys/ddi_implfuncs.h>
#include <sys/esunddi.h>
#include <sys/sunddi.h>
#include <sys/sunndi.h>
#include <sys/systeminfo.h>
#include <sys/hwconf.h>
#include <sys/file.h>
#include <sys/varargs.h>
#include <sys/thread.h>
#include <sys/cred.h>
#include <sys/autoconf.h>
#include <sys/kobj.h>
#include <sys/consdev.h>
#include <sys/systm.h>
#include <sys/debug.h>
#include <sys/atomic.h>

extern struct dev_ops nodev_ops;
extern struct dev_ops mod_nodev_ops;

struct mod_noload {
    struct mod_noload *mn_next;
    char *mn_name;
};

/*
 * Function prototypes
 */
static int init_stubs(struct modctl *, struct mod_modinfo *);
static int nm_hash(char *);
static void make_syscallname(char *, int);
static void hwc_hash_init();
static void hwc_hash(struct hwc_spec *, major_t);
static void hwc_unhash(struct hwc_spec *);

struct dev_ops *
mod_hold_dev_by_major(major_t major)
{
    struct dev_ops **devopspp, *ops;
    int loaded;
    char *drvname;

    if (major >= devcnt)
        return (NULL);

    LOCK_DEV_OPS(&(devnamesp[major].dn_lock));
    devopspp = &devopsp[major];
    loaded = 1;
    while (loaded && !CB_DRV_INSTALLED(*devopspp)) {
        UNLOCK_DEV_OPS(&(devnamesp[major].dn_lock));
        drvname = mod_major_to_name(major);
        if (drvname == NULL)
            return (NULL);
        loaded = (modload("drv", drvname) != -1);
        LOCK_DEV_OPS(&(devnamesp[major].dn_lock));
    }
    if (loaded) {
        INCR_DEV_OPS_REF(*devopspp);
        ops = *devopspp;
    } else {
        ops = NULL;
    }
    UNLOCK_DEV_OPS(&(devnamesp[major].dn_lock));
    return (ops);
}

#ifdef  DEBUG_RELE
static int mod_rele_pause = DEBUG_RELE;
#endif  /* DEBUG_RELE */

void
mod_rele_dev_by_major(major_t major)
{
    struct dev_ops *ops;
    struct devnames *dnp;

    if (major >= devcnt)
        return;

    dnp = &devnamesp[major];
    LOCK_DEV_OPS(&dnp->dn_lock);
    ops = devopsp[major];
    ASSERT(CB_DRV_INSTALLED(ops));

#ifdef  DEBUG_RELE
    if (!DEV_OPS_HELD(ops))  {
        char *s;
        static char *msg = "mod_rele_dev_by_major: unheld driver!";

        printf("mod_rele_dev_by_major: Major dev <%u>, name <%s>\n",
            (uint_t)major,
            (s = mod_major_to_name(major)) ? s : "unknown");
        if (mod_rele_pause)
            debug_enter(msg);
        else
            printf("%s\n", msg);
        UNLOCK_DEV_OPS(&dnp->dn_lock);
        return;         /* XXX: Note changed behavior */
    }

#endif  /* DEBUG_RELE */

    if (!DEV_OPS_HELD(ops)) {
        cmn_err(CE_PANIC,
            "mod_rele_dev_by_major: Unheld driver: major number <%u>",
            (uint_t)major);
    }
    DECR_DEV_OPS_REF(ops);
    UNLOCK_DEV_OPS(&dnp->dn_lock);
}

struct dev_ops *
mod_hold_dev_by_devi(dev_info_t *devi)
{
    major_t major;
    char *name;

    name = ddi_get_name(devi);
    if ((major = mod_name_to_major(name)) == (major_t)-1)
        return (NULL);
    return (mod_hold_dev_by_major(major));
}

void
mod_rele_dev_by_devi(dev_info_t *devi)
{
    major_t major;
    char *name;

    name = ddi_get_name(devi);
    if ((major = mod_name_to_major(name)) == (major_t)-1)
        return;
    mod_rele_dev_by_major(major);
}

int
nomod_zero()
{
    return (0);
}

int
nomod_minus_one()
{
    return (-1);
}

int
nomod_einval()
{
    return (EINVAL);
}

void
nomod_void()
{
    /* nothing */
}

/*
 * Install all the stubs for a module.
 * Return zero if there were no errors or an errno value.
 */
int
install_stubs_by_name(struct modctl *modp, char *name)
{
    char *p;
    char *filenamep;
    char namebuf[MODMAXNAMELEN + 12];
    struct mod_modinfo *mp;

    p = name;
    filenamep = name;

    while (*p)
        if (*p++ == '/')
            filenamep = p;

    /*
     * Concatenate "name" with "_modname" then look up this symbol
     * in the kernel.  If not found, we're done.
     * If found, then find the "mod" info structure and call init_stubs().
     */
    p = namebuf;

    while (*filenamep && *filenamep != '.')
        *p++ = *filenamep++;

    (void) strcpy(p, "_modinfo");

    if ((mp = (struct mod_modinfo *)modgetsymvalue(namebuf, 1)) != 0)
        return (init_stubs(modp, mp));
    else
        return (0);
}

static int
init_stubs(struct modctl *modp, struct mod_modinfo *mp)
{
    struct mod_stub_info *sp;
    int i;
    ulong_t offset;
    uintptr_t funcadr;
    char *funcname;

    modp->mod_modinfo = mp;

    /*
     * Fill in all stubs for this module.  We can't be lazy, since
     * some calls could come in from interrupt level, and we
     * can't modlookup then (symbols may be paged out).
     */
    sp = mp->modm_stubs;
    for (i = 0; sp->mods_func_adr; i++, sp++) {
        funcname = modgetsymname(sp->mods_stub_adr, &offset);
        if (funcname == NULL) {
            printf("init_stubs: couldn't find symbol "
                "in module %s\n", mp->modm_module_name);
            return (EFAULT);
        }
        funcadr = kobj_lookup(modp->mod_mp, funcname);

        if (kobj_addrcheck(modp->mod_mp, (caddr_t)funcadr)) {
            printf("%s:%s() not defined properly\n",
                mp->modm_module_name, funcname);
            return (EFAULT);
        }
        sp->mods_func_adr = funcadr;
    }
    mp->mp = modp;
    return (0);
}

/*
 * modp->mod_modinfo has to be checked in these functions before
 * mod_stub_info is accessed because it's not guranteed that all
 * modules define mod_stub_info structures.
 */
void
install_stubs(struct modctl *modp)
{
    struct mod_stub_info *stub;

    if (modp->mod_modinfo) {
        membar_producer();
        for (stub = modp->mod_modinfo->modm_stubs;
            stub->mods_func_adr; stub++) {
            stub->mods_flag |= MODS_INSTALLED;
        }
        membar_producer();
    }
}

void
uninstall_stubs(struct modctl *modp)
{
    struct mod_stub_info *stub;

    if (modp->mod_modinfo) {
        membar_producer();
        for (stub = modp->mod_modinfo->modm_stubs;
            stub->mods_func_adr; stub++) {
            stub->mods_flag &= ~MODS_INSTALLED;
        }
        membar_producer();
    }
}

void
reset_stubs(struct modctl *modp)
{
    struct mod_stub_info *stub;

    if (modp->mod_modinfo) {
        for (stub = modp->mod_modinfo->modm_stubs;
            stub->mods_func_adr; stub++) {
            if (stub->mods_flag & (MODS_WEAK | MODS_NOUNLOAD))
                stub->mods_func_adr =
                    (uintptr_t)stub->mods_errfcn;
            else
                stub->mods_func_adr =
                    (uintptr_t)mod_hold_stub;
        }
        modp->mod_modinfo->mp = NULL;
    }
}

struct modctl *
mod_getctl(struct modlinkage *modlp)
{
    struct modctl   *modp;

    mutex_enter(&mod_lock);
    modp = &modules;
    do {
        if (modp->mod_linkage == modlp) {
            mutex_exit(&mod_lock);
            return (modp);
        }
    } while ((modp = modp->mod_next) != &modules);
    mutex_exit(&mod_lock);
    return (NULL);
}


/*
 * Attach driver.conf info to devnames for a driver
 */
struct par_list *
impl_make_parlist(major_t major)
{
    int err;
    struct par_list *pl = NULL, *tmp;
    ddi_prop_t *props = NULL;
    char *confname, *drvname;
    struct devnames *dnp;

    dnp = &devnamesp[major];

    ASSERT(mutex_owned(&dnp->dn_lock));

    /*
     * If .conf file already parsed or driver removed, just return.
     * May return NULL.
     */
    if (dnp->dn_flags & (DN_CONF_PARSED | DN_DRIVER_REMOVED))
        return (dnp->dn_pl);

    drvname = mod_major_to_name(major);
    if (drvname == NULL)
        return (NULL);

    confname = kmem_alloc(MAXNAMELEN, KM_SLEEP);
    (void) snprintf(confname, MAXNAMELEN, "drv/%s.conf", drvname);
    err = hwc_parse(confname, &pl, &props);
    kmem_free(confname, MAXNAMELEN);
    if (err)    /* file doesn't exist */
        return (NULL);

    /*
     * If there are global properties, reference it from dnp.
     */
    if (props)
        dnp->dn_global_prop_ptr = i_ddi_prop_list_create(props);

    /*
     * Hash specs to be looked up by nexus drivers
     */
    tmp = pl;
    while (tmp) {
        (void) hwc_hash(tmp->par_specs, major);
        tmp = tmp->par_next;
    }

    if (!i_ddi_io_initialized()) {
        if (i_ddi_prop_search(DDI_DEV_T_ANY, DDI_FORCEATTACH,
            DDI_PROP_TYPE_INT, &props))
            dnp->dn_flags |= DN_FORCE_ATTACH;
        if (i_ddi_prop_search(DDI_DEV_T_ANY, DDI_OPEN_RETURNS_EINTR,
            DDI_PROP_TYPE_INT, &props))
            dnp->dn_flags |= DN_OPEN_RETURNS_EINTR;
    }

    if (i_ddi_prop_search(DDI_DEV_T_ANY, DDI_VHCI_CLASS,
        DDI_PROP_TYPE_STRING, &props))
        dnp->dn_flags |= DN_PHCI_DRIVER;

    dnp->dn_flags |= DN_CONF_PARSED;
    dnp->dn_pl = pl;
    return (pl);
}

/*
 * Destroy driver.conf info in devnames array for a driver
 */
int
impl_free_parlist(major_t major)
{
    struct par_list *pl;
    struct devnames *dnp = &devnamesp[major];

    /*
     * Unref driver global property list. Don't destroy it
     * because some instances may still be referencing it.
     * The property list will be freed when the last ref
     * goes away.
     */
    if (dnp->dn_global_prop_ptr) {
        i_ddi_prop_list_rele(dnp->dn_global_prop_ptr, dnp);
        dnp->dn_global_prop_ptr = NULL;
    }

    /*
     * remove specs from hash table
     */
    for (pl = dnp->dn_pl; pl; pl = pl->par_next)
        hwc_unhash(pl->par_specs);

    impl_delete_par_list(dnp->dn_pl);
    dnp->dn_pl = NULL;
    dnp->dn_flags &= ~DN_CONF_PARSED;
    return (0);
}

struct bind *mb_hashtab[MOD_BIND_HASHSIZE];
struct bind *sb_hashtab[MOD_BIND_HASHSIZE];

static int
nm_hash(char *name)
{
    char c;
    int hash = 0;

    for (c = *name++; c; c = *name++)
        hash ^= c;

    return (hash & MOD_BIND_HASHMASK);
}

void
clear_binding_hash(struct bind **bhash)
{
    int i;
    struct bind *bp, *bp1;

    for (i = 0; i < MOD_BIND_HASHSIZE; i++) {
        bp = bhash[i];
        while (bp != NULL) {
            kmem_free(bp->b_name, strlen(bp->b_name) + 1);
            if (bp->b_bind_name) {
                kmem_free(bp->b_bind_name,
                    strlen(bp->b_bind_name) + 1);
            }
            bp1 = bp;
            bp = bp->b_next;
            kmem_free(bp1, sizeof (struct bind));
        }
        bhash[i] = NULL;
    }
}

static struct bind *
find_mbind(char *name, struct bind **hashtab)
{
    int hashndx;
    struct bind *mb;

    hashndx = nm_hash(name);
    for (mb = hashtab[hashndx]; mb; mb = mb->b_next) {
        if (strcmp(name, mb->b_name) == 0)
            break;
    }

    return (mb);
}

/*
 * Create an entry for the given (name, major, bind_name) tuple in the
 * hash table supplied.  Reject the attempt to do so if 'name' is already
 * in the hash table.
 *
 * Does not provide synchronization, so use only during boot or with
 * externally provided locking.
 */
int
make_mbind(char *name, int major, char *bind_name, struct bind **hashtab)
{
    struct bind *bp;
    int hashndx;

    ASSERT(hashtab != NULL);

    /*
     * Fail if the key being added is already in the hash table
     */
    if (find_mbind(name, hashtab) != NULL)
        return (-1);

    bp = kmem_zalloc(sizeof (struct bind), KM_SLEEP);
    bp->b_name = kmem_alloc(strlen(name) + 1, KM_SLEEP);
    (void) strcpy(bp->b_name, name);
    bp->b_num = major;
    if (bind_name != NULL) {
        bp->b_bind_name = kmem_alloc(strlen(bind_name) + 1, KM_SLEEP);
        (void) strcpy(bp->b_bind_name, bind_name);
    }
    hashndx = nm_hash(name);
    bp->b_next = hashtab[hashndx];
    hashtab[hashndx] = bp;

    return (0);
}

/*
 * Delete a binding from a binding-hash.
 *
 * Does not provide synchronization, so use only during boot or with
 * externally provided locking.
 */
void
delete_mbind(char *name, struct bind **hashtab)
{
    int hashndx;
    struct bind *b, *bparent = NULL;
    struct bind *t = NULL;      /* target to delete */

    hashndx = nm_hash(name);

    if (hashtab[hashndx] == NULL)
        return;

    b = hashtab[hashndx];
    if (strcmp(name, b->b_name) == 0) { /* special case first elem. */
        hashtab[hashndx] = b->b_next;
        t = b;
    } else {
        for (b = hashtab[hashndx]; b; b = b->b_next) {
            if (strcmp(name, b->b_name) == 0) {
                ASSERT(bparent);
                t = b;
                bparent->b_next = b->b_next;
                break;
            }
            bparent = b;
        }
    }

    if (t != NULL) {    /* delete the target */
        ASSERT(t->b_name);
        kmem_free(t->b_name, strlen(t->b_name) + 1);
        if (t->b_bind_name)
            kmem_free(t->b_bind_name, strlen(t->b_bind_name) + 1);
        kmem_free(t, sizeof (struct bind));
    }
}


major_t
mod_name_to_major(char *name)
{
    struct bind *mbind;

    if ((mbind = find_mbind(name, mb_hashtab)) != NULL)
        return ((major_t)mbind->b_num);

    return ((major_t)-1);
}

char *
mod_major_to_name(major_t major)
{
    if (major >= devcnt)
        return (NULL);
    return ((&devnamesp[major])->dn_name);
}

/*
 * Set up the devnames array.  Error check for duplicate entries.
 */
void
init_devnamesp(int size)
{
    int hshndx;
    struct bind *bp;
    static char dupwarn[] =
        "!Device entry \"%s %d\" conflicts with previous entry \"%s %d\" "
        "in /etc/name_to_major.";
    static char badmaj[] = "The major number %u is invalid.";

    ASSERT(size <= L_MAXMAJ32 && size > 0);

    /*
     * Allocate the devnames array.  All mutexes and cv's will be
     * automagically initialized.
     */
    devnamesp = kobj_zalloc(size * sizeof (struct devnames), KM_SLEEP);

    /*
     * Stick the contents of mb_hashtab into the devnames array.  Warn if
     * two hash entries correspond to the same major number, or if a
     * major number is out of range.
     */
    for (hshndx = 0; hshndx < MOD_BIND_HASHSIZE; hshndx++) {
        for (bp = mb_hashtab[hshndx]; bp; bp = bp->b_next) {
            if (make_devname(bp->b_name, (major_t)bp->b_num) != 0) {
                /*
                 * If there is not an entry at b_num already,
                 * then this must be a bad major number.
                 */
                char *nm = mod_major_to_name(bp->b_num);
                if (nm == NULL) {
                    cmn_err(CE_WARN, badmaj,
                        (uint_t)bp->b_num);
                } else {
                    cmn_err(CE_WARN, dupwarn, bp->b_name,
                        bp->b_num, nm, bp->b_num);
                }
            }
        }
    }

    /* Initialize hash table for hwc_spec's */
    hwc_hash_init();
}

int
make_devname(char *name, major_t major)
{
    struct devnames *dnp;
    char *copy;

    /*
     * Until on-disk support for major nums > 14 bits arrives, fail
     * any major numbers that are too big.
     */
    if (major > L_MAXMAJ32)
        return (EINVAL);

    dnp = &devnamesp[major];
    LOCK_DEV_OPS(&dnp->dn_lock);
    if (dnp->dn_name) {
        if (strcmp(dnp->dn_name, name) != 0) {
            /* Another driver already here */
            UNLOCK_DEV_OPS(&dnp->dn_lock);
            return (EINVAL);
        }
        /* Adding back a removed driver */
        dnp->dn_flags &= ~DN_DRIVER_REMOVED;
        UNLOCK_DEV_OPS(&dnp->dn_lock);
        return (0);
    }

    /*
     * Check if flag is taken by getudev()
     */
    if (dnp->dn_flags & DN_TAKEN_GETUDEV) {
        UNLOCK_DEV_OPS(&dnp->dn_lock);
        return (EINVAL);
    }

    copy = kmem_alloc(strlen(name) + 1, KM_SLEEP);
    (void) strcpy(copy, name);

    /* Make sure string is copied before setting dn_name */
    membar_producer();
    dnp->dn_name = copy;
    dnp->dn_flags = 0;
    UNLOCK_DEV_OPS(&dnp->dn_lock);
    return (0);
}

/*
 * Set up the syscallnames array.
 */
void
init_syscallnames(int size)
{
    int hshndx;
    struct bind *bp;

    syscallnames = kobj_zalloc(size * sizeof (char *), KM_SLEEP);

    for (hshndx = 0; hshndx < MOD_BIND_HASHSIZE; hshndx++) {
        for (bp = sb_hashtab[hshndx]; bp; bp = bp->b_next) {
            if (bp->b_num < 0 || bp->b_num >= size) {
                cmn_err(CE_WARN,
                    "!Couldn't add system call \"%s %d\". "
                    "Value out of range (0..%d) in "
                    "/etc/name_to_sysnum.",
                    bp->b_name, bp->b_num, size - 1);
                continue;
            }
            make_syscallname(bp->b_name, bp->b_num);
        }
    }
}

static void
make_syscallname(char *name, int sysno)
{
    char **cp = &syscallnames[sysno];

    if (*cp != NULL) {
        cmn_err(CE_WARN, "!Couldn't add system call \"%s %d\". "
            "It conflicts with \"%s %d\" in /etc/name_to_sysnum.",
            name, sysno, *cp, sysno);
        return;
    }
    *cp = kmem_alloc(strlen(name) + 1, KM_SLEEP);
    (void) strcpy(*cp, name);
}

/*
 * Given a system call name, get its number.
 */
int
mod_getsysnum(char *name)
{
    struct bind *mbind;

    if ((mbind = find_mbind(name, sb_hashtab)) != NULL)
        return (mbind->b_num);

    return (-1);
}

/*
 * Given a system call number, get the system call name.
 */
char *
mod_getsysname(int sysnum)
{
    return (syscallnames[sysnum]);
}

/*
 * Find the name of the module containing the specified pc.
 * Returns the name on success, "<unknown>" on failure.
 * No mod_lock locking is required because things are never deleted from
 * the &modules list.
 */
char *
mod_containing_pc(caddr_t pc)
{
    struct modctl   *mcp = &modules;

    do {
        if (mcp->mod_mp != NULL &&
            (size_t)pc - (size_t)mcp->mod_text < mcp->mod_text_size)
            return (mcp->mod_modname);
    } while ((mcp = mcp->mod_next) != &modules);
    return ("<unknown>");
}

/*
 * Hash tables for hwc_spec
 *
 * The purpose of these hash tables are to allow the framework to discover
 * all possible .conf children for a given nexus. There are two hash tables.
 * One is hashed based on parent name, the on the class name. Each
 * driver.conf file translates to a list of hwc_spec's. Adding and
 * removing the entire list is an atomic operation, protected by
 * the hwc_hash_lock.
 *
 * What we get from all the hashing is the function hwc_get_child_spec().
 */
#define HWC_SPEC_HASHSIZE   (1 << 6)    /* 64 */

static mod_hash_t *hwc_par_hash;    /* hash by parent name */
static mod_hash_t *hwc_class_hash;  /* hash by class name */
static kmutex_t hwc_hash_lock;      /* lock protecting hwc hashes */

/*
 * Initialize hash tables for parent and class specs
 */
static void
hwc_hash_init()
{
    hwc_par_hash = mod_hash_create_strhash("hwc parent spec hash",
        HWC_SPEC_HASHSIZE, mod_hash_null_valdtor);
    hwc_class_hash = mod_hash_create_strhash("hwc class spec hash",
        HWC_SPEC_HASHSIZE, mod_hash_null_valdtor);
}

/*
 * Insert a spec into hash table. hwc_hash_lock must be held
 */
static void
hwc_hash_insert(struct hwc_spec *spec, char *name, mod_hash_t *hash)
{
    mod_hash_key_t key;
    struct hwc_spec *entry = NULL;

    ASSERT(name != NULL);

    if (mod_hash_find(hash, (mod_hash_key_t)name,
        (mod_hash_val_t)&entry) != 0) {
        /* Name doesn't exist, insert a new key */
        key = kmem_alloc(strlen(name) + 1, KM_SLEEP);
        (void) strcpy((char *)key, name);
        if (mod_hash_insert(hash, key, (mod_hash_val_t)spec) != 0) {
            kmem_free(key, strlen(name) + 1);
            cmn_err(CE_WARN, "hwc hash state inconsistent");
        }
        return;
    }

    /*
     * Name is already present, append spec to the list.
     * This is the case when driver.conf specifies multiple
     * nodes under a single parent or class.
     */
    while (entry->hwc_hash_next)
        entry = entry->hwc_hash_next;
    entry->hwc_hash_next = spec;
}

/*
 * Remove a spec entry from spec hash table, the spec itself is
 * destroyed external to this function.
 */
static void
hwc_hash_remove(struct hwc_spec *spec, char *name, mod_hash_t *hash)
{
    char *key;
    struct hwc_spec *entry;

    ASSERT(name != NULL);

    if (mod_hash_find(hash, (mod_hash_key_t)name,
        (mod_hash_val_t)&entry) != 0) {
        return; /* name not found in hash */
    }

    /*
     * If the head is the spec to be removed, either destroy the
     * entry or replace it with the remaining list.
     */
    if (entry == spec) {
        if (spec->hwc_hash_next == NULL) {
            (void) mod_hash_destroy(hash, (mod_hash_key_t)name);
            return;
        }
        key = kmem_alloc(strlen(name) + 1, KM_SLEEP);
        (void) strcpy(key, name);
        (void) mod_hash_replace(hash, (mod_hash_key_t)key,
            (mod_hash_val_t)spec->hwc_hash_next);
        spec->hwc_hash_next = NULL;
        return;
    }

    /*
     * If the head is not the one, look for the spec in the
     * hwc_hash_next linkage.
     */
    while (entry->hwc_hash_next && (entry->hwc_hash_next != spec))
        entry = entry->hwc_hash_next;

    if (entry->hwc_hash_next) {
        entry->hwc_hash_next = spec->hwc_hash_next;
        spec->hwc_hash_next = NULL;
    }
}

/*
 * Hash a list of specs based on either parent name or class name
 */
static void
hwc_hash(struct hwc_spec *spec_list, major_t major)
{
    struct hwc_spec *spec = spec_list;

    mutex_enter(&hwc_hash_lock);
    while (spec) {
        /* Put driver major here so parent can find it */
        spec->hwc_major = major;

        if (spec->hwc_parent_name != NULL) {
            hwc_hash_insert(spec, spec->hwc_parent_name,
                hwc_par_hash);
        } else if (spec->hwc_class_name != NULL) {
            hwc_hash_insert(spec, spec->hwc_class_name,
                hwc_class_hash);
        } else {
            cmn_err(CE_WARN,
                "hwc_hash: No class or parent specified");
        }
        spec = spec->hwc_next;
    }
    mutex_exit(&hwc_hash_lock);
}

/*
 * Remove a list of specs from hash tables. Don't destroy the specs yet.
 */
static void
hwc_unhash(struct hwc_spec *spec_list)
{
    struct hwc_spec *spec = spec_list;

    mutex_enter(&hwc_hash_lock);
    while (spec) {
        if (spec->hwc_parent_name != NULL) {
            hwc_hash_remove(spec, spec->hwc_parent_name,
                hwc_par_hash);
        } else if (spec->hwc_class_name != NULL) {
            hwc_hash_remove(spec, spec->hwc_class_name,
                hwc_class_hash);
        } else {
            cmn_err(CE_WARN,
                "hwc_unhash: No class or parent specified");
        }
        spec = spec->hwc_next;
    }
    mutex_exit(&hwc_hash_lock);
}

/*
 * Make a copy of specs in a hash entry and add to the end of listp.
 * Called by nexus to locate a list of child specs.
 *
 * entry is a list of hwc_spec chained together with hwc_hash_next.
 * listp points to list chained together with hwc_next.
 */
static void
hwc_spec_add(struct hwc_spec **listp, struct hwc_spec *entry,
    major_t match_major)
{
    /* Find the tail of the list */
    while (*listp)
        listp = &(*listp)->hwc_next;

    while (entry) {
        struct hwc_spec *spec;

        if ((match_major != (major_t)-1) &&
            (match_major != entry->hwc_major)) {
            entry = entry->hwc_hash_next;
            continue;
        }

        /*
         * Allocate spec and copy the content of entry.
         * No need to copy class/parent name since caller
         * already knows the parent dip.
         */
        spec = kmem_zalloc(sizeof (*spec), KM_SLEEP);
        spec->hwc_devi_name = i_ddi_strdup(
            entry->hwc_devi_name, KM_SLEEP);
        spec->hwc_major = entry->hwc_major;
        spec->hwc_devi_sys_prop_ptr = i_ddi_prop_list_dup(
            entry->hwc_devi_sys_prop_ptr, KM_SLEEP);

        *listp = spec;
        listp = &spec->hwc_next;
        entry = entry->hwc_hash_next;
    }
}

/*
 * Given a dip, find the list of child .conf specs from most specific
 * (parent pathname) to least specific (class name).
 *
 * This function allows top-down loading to be implemented without
 * changing the format of driver.conf file.
 */
struct hwc_spec *
hwc_get_child_spec(dev_info_t *dip, major_t match_major)
{
    extern char *i_ddi_parname(dev_info_t *, char *);
    extern int i_ddi_get_exported_classes(dev_info_t *, char ***);
    extern void i_ddi_free_exported_classes(char **, int);

    int i, nclass;
    char **classes;
    struct hwc_spec *list = NULL;
    mod_hash_val_t val;
    char *parname, *parname_buf;
    char *deviname, *deviname_buf;
    char *pathname, *pathname_buf;
    char *bindname;
    char *drvname;

    pathname_buf = kmem_alloc(3 * MAXPATHLEN, KM_SLEEP);
    deviname_buf = pathname_buf + MAXPATHLEN;
    parname_buf = pathname_buf + (2 * MAXPATHLEN);

    mutex_enter(&hwc_hash_lock);

    /*
     * Lookup based on full path.
     * In the case of root node, ddi_pathname would return
     * null string so just skip calling it.
     * As the pathname always begins with /, no simpler
     * name can duplicate it.
     */
    pathname = (dip == ddi_root_node()) ? "/" :
        ddi_pathname(dip, pathname_buf);
    ASSERT(pathname != NULL);
    ASSERT(*pathname == '/');

    if (mod_hash_find(hwc_par_hash, (mod_hash_key_t)pathname, &val) == 0) {
        hwc_spec_add(&list, (struct hwc_spec *)val, match_major);
    }

    /*
     * Lookup nodename@address.
     * Note deviname cannot match pathname.
     */
    deviname = ddi_deviname(dip, deviname_buf);
    if (*deviname != '\0') {
        /*
         * Skip leading / returned by ddi_deviname.
         */
        ASSERT(*deviname == '/');
        deviname++;
        if ((*deviname != '\0') && (mod_hash_find(hwc_par_hash,
            (mod_hash_key_t)deviname, &val) == 0))
            hwc_spec_add(&list,
                (struct hwc_spec *)val, match_major);
    }

    /*
     * Lookup bindingname@address.
     * Take care not to perform duplicate lookups.
     */
    parname = i_ddi_parname(dip, parname_buf);
    if (*parname != '\0') {
        ASSERT(*parname != '/');
        if ((strcmp(parname, deviname) != 0) &&
            (mod_hash_find(hwc_par_hash,
            (mod_hash_key_t)parname, &val) == 0)) {
            hwc_spec_add(&list,
                (struct hwc_spec *)val, match_major);
        }
    }

    /*
     * Lookup driver binding name
     */
    bindname = ddi_binding_name(dip);
    ASSERT(*bindname != '/');
    if ((strcmp(bindname, parname) != 0) &&
        (strcmp(bindname, deviname) != 0) &&
        (mod_hash_find(hwc_par_hash, (mod_hash_key_t)bindname, &val) == 0))
        hwc_spec_add(&list, (struct hwc_spec *)val, match_major);

    /*
     * Lookup driver name
     */
    drvname = (char *)ddi_driver_name(dip);
    ASSERT(*drvname != '/');
    if ((strcmp(drvname, bindname) != 0) &&
        (strcmp(drvname, parname) != 0) &&
        (strcmp(drvname, deviname) != 0) &&
        (mod_hash_find(hwc_par_hash, (mod_hash_key_t)drvname, &val) == 0))
        hwc_spec_add(&list, (struct hwc_spec *)val, match_major);

    kmem_free(pathname_buf, 3 * MAXPATHLEN);

    /*
     * Lookup classes exported by this node and lookup the
     * class hash table for all .conf specs
     */
    nclass = i_ddi_get_exported_classes(dip, &classes);
    for (i = 0; i < nclass; i++) {
        if (mod_hash_find(hwc_class_hash, (mod_hash_key_t)classes[i],
            &val) == 0)
            hwc_spec_add(&list, (struct hwc_spec *)val,
                match_major);
    }
    i_ddi_free_exported_classes(classes, nclass);

    mutex_exit(&hwc_hash_lock);
    return (list);
}