freebsd/sys/boot/common/module.c

/*-
 * Copyright (c) 1998 Michael Smith <msmith@freebsd.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");

/*
 * file/module function dispatcher, support, etc.
 */

#include <stand.h>
#include <string.h>
#include <sys/param.h>
#include <sys/linker.h>
#include <sys/module.h>
#include <sys/queue.h>

#include "bootstrap.h"

#define	MDIR_REMOVED	0x0001
#define	MDIR_NOHINTS	0x0002

struct moduledir {
	char	*d_path;	/* path of modules directory */
	u_char	*d_hints;	/* content of linker.hints file */
	int	d_hintsz;	/* size of hints data */
	int	d_flags;
	STAILQ_ENTRY(moduledir) d_link;
};

static int			file_load(char *filename, vm_offset_t dest, struct preloaded_file **result);
static int			file_loadraw(char *type, char *name);
static int			file_load_dependencies(struct preloaded_file *base_mod);
static char *			file_search(const char *name, char **extlist);
static struct kernel_module *	file_findmodule(struct preloaded_file *fp, char *modname, struct mod_depend *verinfo);
static int			file_havepath(const char *name);
static char			*mod_searchmodule(char *name, struct mod_depend *verinfo);
static void			file_insert_tail(struct preloaded_file *mp);
struct file_metadata*		metadata_next(struct file_metadata *base_mp, int type);
static void			moduledir_readhints(struct moduledir *mdp);
static void			moduledir_rebuild(void);

/* load address should be tweaked by first module loaded (kernel) */
static vm_offset_t	loadaddr = 0;

static const char	*default_searchpath ="/boot/kernel;/boot/modules";

static STAILQ_HEAD(, moduledir) moduledir_list = STAILQ_HEAD_INITIALIZER(moduledir_list);

struct preloaded_file *preloaded_files = NULL;

static char *kld_ext_list[] = {
    ".ko",
    "",
    NULL
};


/*
 * load an object, either a disk file or code module.
 *
 * To load a file, the syntax is:
 *
 * load -t <type> <path>
 *
 * code modules are loaded as:
 *
 * load <path> <options>
 */

COMMAND_SET(load, "load", "load a kernel or module", command_load);

static int
command_load(int argc, char *argv[])
{
    char	*typestr;
    int		dofile, dokld, ch, error;
    
    dokld = dofile = 0;
    optind = 1;
    optreset = 1;
    typestr = NULL;
    if (argc == 1) {
	command_errmsg = "no filename specified";
	return(CMD_ERROR);
    }
    while ((ch = getopt(argc, argv, "kt:")) != -1) {
	switch(ch) {
	case 'k':
	    dokld = 1;
	    break;
	case 't':
	    typestr = optarg;
	    dofile = 1;
	    break;
	case '?':
	default:
	    /* getopt has already reported an error */
	    return(CMD_OK);
	}
    }
    argv += (optind - 1);
    argc -= (optind - 1);

    /*
     * Request to load a raw file?
     */
    if (dofile) {
	if ((argc != 2) || (typestr == NULL) || (*typestr == 0)) {
	    command_errmsg = "invalid load type";
	    return(CMD_ERROR);
	}
	return(file_loadraw(typestr, argv[1]));
    }
    /*
     * Do we have explicit KLD load ?
     */
    if (dokld || file_havepath(argv[1])) {
	error = mod_loadkld(argv[1], argc - 2, argv + 2);
	if (error == EEXIST)
	    sprintf(command_errbuf, "warning: KLD '%s' already loaded", argv[1]);
	return (error == 0 ? CMD_OK : CMD_ERROR);
    }
    /*
     * Looks like a request for a module.
     */
    error = mod_load(argv[1], NULL, argc - 2, argv + 2);
    if (error == EEXIST)
	sprintf(command_errbuf, "warning: module '%s' already loaded", argv[1]);
    return (error == 0 ? CMD_OK : CMD_ERROR);
}

COMMAND_SET(unload, "unload", "unload all modules", command_unload);

static int
command_unload(int argc, char *argv[])
{
    struct preloaded_file	*fp;
    
    while (preloaded_files != NULL) {
	fp = preloaded_files;
	preloaded_files = preloaded_files->f_next;
	file_discard(fp);
    }
    loadaddr = 0;
    unsetenv("kernelname");
    return(CMD_OK);
}

COMMAND_SET(lsmod, "lsmod", "list loaded modules", command_lsmod);

static int
command_lsmod(int argc, char *argv[])
{
    struct preloaded_file	*fp;
    struct kernel_module	*mp;
    struct file_metadata	*md;
    char			lbuf[80];
    int				ch, verbose;

    verbose = 0;
    optind = 1;
    optreset = 1;
    while ((ch = getopt(argc, argv, "v")) != -1) {
	switch(ch) {
	case 'v':
	    verbose = 1;
	    break;
	case '?':
	default:
	    /* getopt has already reported an error */
	    return(CMD_OK);
	}
    }

    pager_open();
    for (fp = preloaded_files; fp; fp = fp->f_next) {
	sprintf(lbuf, " %p: %s (%s, 0x%lx)\n", 
		(void *) fp->f_addr, fp->f_name, fp->f_type, (long) fp->f_size);
	pager_output(lbuf);
	if (fp->f_args != NULL) {
	    pager_output("    args: ");
	    pager_output(fp->f_args);
	    pager_output("\n");
	}
	if (fp->f_modules) {
	    pager_output("  modules: ");
	    for (mp = fp->f_modules; mp; mp = mp->m_next) {
		sprintf(lbuf, "%s.%d ", mp->m_name, mp->m_version);
		pager_output(lbuf);
	    }
	    pager_output("\n");
	}
	if (verbose) {
	    /* XXX could add some formatting smarts here to display some better */
	    for (md = fp->f_metadata; md != NULL; md = md->md_next) {
		sprintf(lbuf, "      0x%04x, 0x%lx\n", md->md_type, (long) md->md_size);
		pager_output(lbuf);
	    }
	}
    }
    pager_close();
    return(CMD_OK);
}

/*
 * File level interface, functions file_*
 */
int
file_load(char *filename, vm_offset_t dest, struct preloaded_file **result)
{
    struct preloaded_file *fp;
    int error;
    int i;

    error = EFTYPE;
    for (i = 0, fp = NULL; file_formats[i] && fp == NULL; i++) {
	error = (file_formats[i]->l_load)(filename, loadaddr, &fp);
	if (error == 0) {
	    fp->f_loader = i;		/* remember the loader */
	    *result = fp;
	    break;
	}
	if (error == EFTYPE)
	    continue;		/* Unknown to this handler? */
	if (error) {
	    sprintf(command_errbuf, "can't load file '%s': %s",
		filename, strerror(error));
	    break;
	}
    }
    return (error);
}

static int
file_load_dependencies(struct preloaded_file *base_file) {
    struct file_metadata *md;
    struct preloaded_file *fp;
    struct mod_depend *verinfo;
    struct kernel_module *mp;
    char *dmodname;
    int error;

    md = file_findmetadata(base_file, MODINFOMD_DEPLIST);
    if (md == NULL)
	return (0);
    error = 0;
    do {
	verinfo = (struct mod_depend*)md->md_data;
	dmodname = (char *)(verinfo + 1);
	if (file_findmodule(NULL, dmodname, verinfo) == NULL) {
	    printf("loading required module '%s'\n", dmodname);
	    error = mod_load(dmodname, verinfo, 0, NULL);
	    if (error)
		break;
	    /*
	     * If module loaded via kld name which isn't listed
	     * in the linker.hints file, we should check if it have
	     * required version.
	     */
	    mp = file_findmodule(NULL, dmodname, verinfo);
	    if (mp == NULL) {
		sprintf(command_errbuf, "module '%s' exists but with wrong version",
		    dmodname);
		error = ENOENT;
		break;
	    }
	}
	md = metadata_next(md, MODINFOMD_DEPLIST);
    } while (md);
    if (!error)
	return (0);
    /* Load failed; discard everything */
    while (base_file != NULL) {
        fp = base_file;
        base_file = base_file->f_next;
        file_discard(fp);
    }
    return (error);
}
/*
 * We've been asked to load (name) as (type), so just suck it in,
 * no arguments or anything.
 */
int
file_loadraw(char *type, char *name)
{
    struct preloaded_file	*fp;
    char			*cp;
    int				fd, got;
    vm_offset_t			laddr;

    /* We can't load first */
    if ((file_findfile(NULL, NULL)) == NULL) {
	command_errmsg = "can't load file before kernel";
	return(CMD_ERROR);
    }

    /* locate the file on the load path */
    cp = file_search(name, NULL);
    if (cp == NULL) {
	sprintf(command_errbuf, "can't find '%s'", name);
	return(CMD_ERROR);
    }
    name = cp;
    
    if ((fd = open(name, O_RDONLY)) < 0) {
	sprintf(command_errbuf, "can't open '%s': %s", name, strerror(errno));
	free(name);
	return(CMD_ERROR);
    }

    laddr = loadaddr;
    for (;;) {
	/* read in 4k chunks; size is not really important */
	got = archsw.arch_readin(fd, laddr, 4096);
	if (got == 0)				/* end of file */
	    break;
	if (got < 0) {				/* error */
	    sprintf(command_errbuf, "error reading '%s': %s", name, strerror(errno));
	    free(name);
	    close(fd);
	    return(CMD_ERROR);
	}
	laddr += got;
    }
    
    /* Looks OK so far; create & populate control structure */
    fp = file_alloc();
    fp->f_name = name;
    fp->f_type = strdup(type);
    fp->f_args = NULL;
    fp->f_metadata = NULL;
    fp->f_loader = -1;
    fp->f_addr = loadaddr;
    fp->f_size = laddr - loadaddr;

    /* recognise space consumption */
    loadaddr = laddr;

    /* Add to the list of loaded files */
    file_insert_tail(fp);
    close(fd);
    return(CMD_OK);
}

/*
 * Load the module (name), pass it (argc),(argv), add container file
 * to the list of loaded files.
 * If module is already loaded just assign new argc/argv.
 */
int
mod_load(char *modname, struct mod_depend *verinfo, int argc, char *argv[])
{
    struct kernel_module	*mp;
    int				err;
    char			*filename;

    if (file_havepath(modname)) {
	printf("Warning: mod_load() called instead of mod_loadkld() for module '%s'\n", modname);
	return (mod_loadkld(modname, argc, argv));
    }
    /* see if module is already loaded */
    mp = file_findmodule(NULL, modname, verinfo);
    if (mp) {
#ifdef moduleargs
	if (mp->m_args)
	    free(mp->m_args);
	mp->m_args = unargv(argc, argv);
#endif
	sprintf(command_errbuf, "warning: module '%s' already loaded", mp->m_name);
	return (0);
    }
    /* locate file with the module on the search path */
    filename = mod_searchmodule(modname, verinfo);
    if (filename == NULL) {
	sprintf(command_errbuf, "can't find '%s'", modname);
	return (ENOENT);
    }
    err = mod_loadkld(filename, argc, argv);
    return (err);
}

/*
 * Load specified KLD. If path is omitted, then try to locate it via
 * search path.
 */
int
mod_loadkld(const char *kldname, int argc, char *argv[])
{
    struct preloaded_file	*fp, *last_file;
    int				err;
    char			*filename;

    /*
     * Get fully qualified KLD name
     */
    filename = file_search(kldname, kld_ext_list);
    if (filename == NULL) {
	sprintf(command_errbuf, "can't find '%s'", kldname);
	return (ENOENT);
    }
    /* 
     * Check if KLD already loaded
     */
    fp = file_findfile(filename, NULL);
    if (fp) {
	sprintf(command_errbuf, "warning: KLD '%s' already loaded", filename);
	free(filename);
	return (0);
    }
    for (last_file = preloaded_files; 
	 last_file != NULL && last_file->f_next != NULL;
	 last_file = last_file->f_next)
	;

    do {
	err = file_load(filename, loadaddr, &fp);
	if (err)
	    break;
	fp->f_args = unargv(argc, argv);
	loadaddr = fp->f_addr + fp->f_size;
	file_insert_tail(fp);		/* Add to the list of loaded files */
	if (file_load_dependencies(fp) != 0) {
	    err = ENOENT;
	    last_file->f_next = NULL;
	    loadaddr = last_file->f_addr + last_file->f_size;
	    fp = NULL;
	    break;
	}
    } while(0);
    if (err == EFTYPE)
	sprintf(command_errbuf, "don't know how to load module '%s'", filename);
    if (err && fp)
	file_discard(fp);
    free(filename);
    return (err);
}

/*
 * Find a file matching (name) and (type).
 * NULL may be passed as a wildcard to either.
 */
struct preloaded_file *
file_findfile(char *name, char *type)
{
    struct preloaded_file *fp;

    for (fp = preloaded_files; fp != NULL; fp = fp->f_next) {
	if (((name == NULL) || !strcmp(name, fp->f_name)) &&
	    ((type == NULL) || !strcmp(type, fp->f_type)))
	    break;
    }
    return (fp);
}

/*
 * Find a module matching (name) inside of given file.
 * NULL may be passed as a wildcard.
 */
struct kernel_module *
file_findmodule(struct preloaded_file *fp, char *modname,
	struct mod_depend *verinfo)
{
    struct kernel_module *mp, *best;
    int bestver, mver;

    if (fp == NULL) {
	for (fp = preloaded_files; fp; fp = fp->f_next) {
	    mp = file_findmodule(fp, modname, verinfo);
    	    if (mp)
		return (mp);
	}
	return (NULL);
    }
    best = NULL;
    bestver = 0;
    for (mp = fp->f_modules; mp; mp = mp->m_next) {
        if (strcmp(modname, mp->m_name) == 0) {
	    if (verinfo == NULL)
		return (mp);
	    mver = mp->m_version;
	    if (mver == verinfo->md_ver_preferred)
		return (mp);
	    if (mver >= verinfo->md_ver_minimum && 
		mver <= verinfo->md_ver_maximum &&
		mver > bestver) {
		best = mp;
		bestver = mver;
	    }
	}
    }
    return (best);
}
/*
 * Make a copy of (size) bytes of data from (p), and associate them as
 * metadata of (type) to the module (mp).
 */
void
file_addmetadata(struct preloaded_file *fp, int type, size_t size, void *p)
{
    struct file_metadata	*md;

    md = malloc(sizeof(struct file_metadata) - sizeof(md->md_data) + size);
    md->md_size = size;
    md->md_type = type;
    bcopy(p, md->md_data, size);
    md->md_next = fp->f_metadata;
    fp->f_metadata = md;
}

/*
 * Find a metadata object of (type) associated with the file (fp)
 */
struct file_metadata *
file_findmetadata(struct preloaded_file *fp, int type)
{
    struct file_metadata *md;

    for (md = fp->f_metadata; md != NULL; md = md->md_next)
	if (md->md_type == type)
	    break;
    return(md);
}

struct file_metadata *
metadata_next(struct file_metadata *md, int type)
{
    if (md == NULL)
	return (NULL);
    while((md = md->md_next) != NULL)
	if (md->md_type == type)
	    break;
    return (md);
}

static char *emptyextlist[] = { "", NULL };

/*
 * Check if the given file is in place and return full path to it.
 */
static char *
file_lookup(const char *path, const char *name, int namelen, char **extlist)
{
    struct stat	st;
    char	*result, *cp, **cpp;
    int		pathlen, extlen, len;

    pathlen = strlen(path);
    extlen = 0;
    if (extlist == NULL)
	extlist = emptyextlist;
    for (cpp = extlist; *cpp; cpp++) {
	len = strlen(*cpp);
	if (len > extlen)
	    extlen = len;
    }
    result = malloc(pathlen + namelen + extlen + 2);
    if (result == NULL)
	return (NULL);
    bcopy(path, result, pathlen);
    if (pathlen > 0 && result[pathlen - 1] != '/')
	result[pathlen++] = '/';
    cp = result + pathlen;
    bcopy(name, cp, namelen);
    cp += namelen;
    for (cpp = extlist; *cpp; cpp++) {
	strcpy(cp, *cpp);
	if (stat(result, &st) == 0 && S_ISREG(st.st_mode))
	    return result;
    }
    free(result);
    return NULL;
}

/*
 * Check if file name have any qualifiers
 */
static int
file_havepath(const char *name)
{
    const char		*cp;

    archsw.arch_getdev(NULL, name, &cp);
    return (cp != name || strchr(name, '/') != NULL);
}

/*
 * Attempt to find the file (name) on the module searchpath.
 * If (name) is qualified in any way, we simply check it and
 * return it or NULL.  If it is not qualified, then we attempt
 * to construct a path using entries in the environment variable
 * module_path.
 *
 * The path we return a pointer to need never be freed, as we manage
 * it internally.
 */
static char *
file_search(const char *name, char **extlist)
{
    struct moduledir	*mdp;
    struct stat		sb;
    char		*result;
    int			namelen;

    /* Don't look for nothing */
    if (name == NULL)
	return(NULL);

    if (*name == 0)
	return(strdup(name));

    if (file_havepath(name)) {
	/* Qualified, so just see if it exists */
	if (stat(name, &sb) == 0)
	    return(strdup(name));
	return(NULL);
    }
    moduledir_rebuild();
    result = NULL;
    namelen = strlen(name);
    STAILQ_FOREACH(mdp, &moduledir_list, d_link) {
	result = file_lookup(mdp->d_path, name, namelen, extlist);
	if (result)
	    break;
    }
    return(result);
}

#define	INT_ALIGN(base, ptr)	ptr = \
	(base) + (((ptr) - (base) + sizeof(int) - 1) & ~(sizeof(int) - 1))

static char *
mod_search_hints(struct moduledir *mdp, const char *modname,
	struct mod_depend *verinfo)
{
    u_char	*cp, *recptr, *bufend, *best;
    char	*result;
    int		*intp, bestver, blen, clen, found, ival, modnamelen, reclen;

    moduledir_readhints(mdp);
    modnamelen = strlen(modname);
    found = 0;
    result = NULL;
    bestver = 0;
    if (mdp->d_hints == NULL)
	goto bad;
    recptr = mdp->d_hints;
    bufend = recptr + mdp->d_hintsz;
    clen = blen = 0;
    best = cp = NULL;
    while (recptr < bufend && !found) {
	intp = (int*)recptr;
	reclen = *intp++;
	ival = *intp++;
	cp = (char*)intp;
	switch (ival) {
	case MDT_VERSION:
	    clen = *cp++;
	    if (clen != modnamelen || bcmp(cp, modname, clen) != 0)
		break;
	    cp += clen;
	    INT_ALIGN(mdp->d_hints, cp);
	    ival = *(int*)cp;
	    cp += sizeof(int);
	    clen = *cp++;
	    if (verinfo == NULL || ival == verinfo->md_ver_preferred) {
		found = 1;
		break;
	    }
	    if (ival >= verinfo->md_ver_minimum && 
		ival <= verinfo->md_ver_maximum &&
		ival > bestver) {
		bestver = ival;
		best = cp;
		blen = clen;
	    }
	    break;
	default:
	    break;
	}
	recptr += reclen + sizeof(int);
    }
    /*
     * Finally check if KLD is in the place
     */
    if (found)
	result = file_lookup(mdp->d_path, cp, clen, NULL);
    else if (best)
	result = file_lookup(mdp->d_path, best, blen, NULL);
bad:
    /*
     * If nothing found or hints is absent - fallback to the old way
     * by using "kldname[.ko]" as module name.
     */
    if (!found && !bestver && result == NULL)
	result = file_lookup(mdp->d_path, modname, modnamelen, kld_ext_list);
    return result;
}

/*
 * Attempt to locate the file containing the module (name)
 */
static char *
mod_searchmodule(char *name, struct mod_depend *verinfo)
{
    struct	moduledir *mdp;
    char	*result;

    moduledir_rebuild();
    /*
     * Now we ready to lookup module in the given directories
     */
    result = NULL;
    STAILQ_FOREACH(mdp, &moduledir_list, d_link) {
	result = mod_search_hints(mdp, name, verinfo);
	if (result)
	    break;
    }

    return(result);
}

int
file_addmodule(struct preloaded_file *fp, char *modname, int version,
	struct kernel_module **newmp)
{
    struct kernel_module *mp;
    struct mod_depend mdepend;

    bzero(&mdepend, sizeof(mdepend));
    mdepend.md_ver_preferred = version;
    mp = file_findmodule(fp, modname, &mdepend);
    if (mp)
	return (EEXIST);
    mp = malloc(sizeof(struct kernel_module));
    if (mp == NULL)
	return (ENOMEM);
    bzero(mp, sizeof(struct kernel_module));
    mp->m_name = strdup(modname);
    mp->m_version = version;
    mp->m_fp = fp;
    mp->m_next = fp->f_modules;
    fp->f_modules = mp;
    if (newmp)
	*newmp = mp;
    return (0);
}

/*
 * Throw a file away
 */
void
file_discard(struct preloaded_file *fp)
{
    struct file_metadata	*md, *md1;
    struct kernel_module	*mp, *mp1;
    if (fp == NULL)
	return;
    md = fp->f_metadata;
    while (md) {
	md1 = md;
	md = md->md_next;
	free(md1);
    }
    mp = fp->f_modules;
    while (mp) {
	if (mp->m_name)
	    free(mp->m_name);
	mp1 = mp;
	mp = mp->m_next;
	free(mp1);
    }	
    if (fp->f_name != NULL)
	free(fp->f_name);
    if (fp->f_type != NULL)
        free(fp->f_type);
    if (fp->f_args != NULL)
        free(fp->f_args);
    free(fp);
}

/*
 * Allocate a new file; must be used instead of malloc()
 * to ensure safe initialisation.
 */
struct preloaded_file *
file_alloc(void)
{
    struct preloaded_file	*fp;
    
    if ((fp = malloc(sizeof(struct preloaded_file))) != NULL) {
	bzero(fp, sizeof(struct preloaded_file));
    }
    return (fp);
}

/*
 * Add a module to the chain
 */
static void
file_insert_tail(struct preloaded_file *fp)
{
    struct preloaded_file	*cm;
    
    /* Append to list of loaded file */
    fp->f_next = NULL;
    if (preloaded_files == NULL) {
	preloaded_files = fp;
    } else {
	for (cm = preloaded_files; cm->f_next != NULL; cm = cm->f_next)
	    ;
	cm->f_next = fp;
    }
}

static char *
moduledir_fullpath(struct moduledir *mdp, const char *fname)
{
    char *cp;

    cp = malloc(strlen(mdp->d_path) + strlen(fname) + 2);
    if (cp == NULL)
	return NULL;
    strcpy(cp, mdp->d_path);
    strcat(cp, "/");
    strcat(cp, fname);
    return (cp);
}

/*
 * Read linker.hints file into memory performing some sanity checks.
 */
static void
moduledir_readhints(struct moduledir *mdp)
{
    struct stat	st;
    char	*path;
    int		fd, size, version;

    if (mdp->d_hints != NULL || (mdp->d_flags & MDIR_NOHINTS))
	return;
    path = moduledir_fullpath(mdp, "linker.hints");
    if (stat(path, &st) != 0 || st.st_size < (sizeof(version) + sizeof(int)) ||
	st.st_size > 100 * 1024 || (fd = open(path, O_RDONLY)) < 0) {
	free(path);
	mdp->d_flags |= MDIR_NOHINTS;
	return;
    }
    free(path);
    size = read(fd, &version, sizeof(version));
    if (size != sizeof(version) || version != LINKER_HINTS_VERSION)
	goto bad;
    size = st.st_size - size;
    mdp->d_hints = malloc(size);
    if (mdp->d_hints == NULL)
	goto bad;
    if (read(fd, mdp->d_hints, size) != size)
	goto bad;
    mdp->d_hintsz = size;
    close(fd);
    return;
bad:
    close(fd);
    if (mdp->d_hints) {
	free(mdp->d_hints);
	mdp->d_hints = NULL;
    }
    mdp->d_flags |= MDIR_NOHINTS;
    return;
}

/*
 * Extract directories from the ';' separated list, remove duplicates.
 */
static void
moduledir_rebuild(void)
{
    struct	moduledir *mdp, *mtmp;
    const char	*path, *cp, *ep;
    int		cplen;

    path = getenv("module_path");
    if (path == NULL)
	path = default_searchpath;
    /*
     * Rebuild list of module directories if it changed
     */
    STAILQ_FOREACH(mdp, &moduledir_list, d_link)
	mdp->d_flags |= MDIR_REMOVED;

    for (ep = path; *ep != 0;  ep++) {
	cp = ep;
	for (; *ep != 0 && *ep != ';'; ep++)
	    ;
	/*
	 * Ignore trailing slashes
	 */
	for (cplen = ep - cp; cplen > 1 && cp[cplen - 1] == '/'; cplen--)
	    ;
	STAILQ_FOREACH(mdp, &moduledir_list, d_link) {
	    if (strlen(mdp->d_path) != cplen ||	bcmp(cp, mdp->d_path, cplen) != 0)
		continue;
	    mdp->d_flags &= ~MDIR_REMOVED;
	    break;
	}
	if (mdp == NULL) {
	    mdp = malloc(sizeof(*mdp) + cplen + 1);
	    if (mdp == NULL)
		return;
	    mdp->d_path = (char*)(mdp + 1);
	    bcopy(cp, mdp->d_path, cplen);
	    mdp->d_path[cplen] = 0;
	    mdp->d_hints = NULL;
	    mdp->d_flags = 0;
	    STAILQ_INSERT_TAIL(&moduledir_list, mdp, d_link);
	}
	if (*ep == 0)
	    break;
    }
    /*
     * Delete unused directories if any
     */
    mdp = STAILQ_FIRST(&moduledir_list);
    while (mdp) {
	if ((mdp->d_flags & MDIR_REMOVED) == 0) {
	    mdp = STAILQ_NEXT(mdp, d_link);
	} else {
	    if (mdp->d_hints)
		free(mdp->d_hints);
	    mtmp = mdp;
	    mdp = STAILQ_NEXT(mdp, d_link);
	    STAILQ_REMOVE(&moduledir_list, mtmp, moduledir, d_link);
	    free(mtmp);
	}
    }
    return;
}