sys/kern/kern_linker.c

/*-
 * Copyright (c) 1997 Doug Rabson
 * 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.
 *
 * $FreeBSD: src/sys/kern/kern_linker.c,v 1.41.2.3 2001/11/21 17:50:35 luigi Exp $
 * $DragonFly: src/sys/kern/kern_linker.c,v 1.43 2008/02/06 22:37:46 nth Exp $
 */

#include "opt_ddb.h"

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/sysproto.h>
#include <sys/sysent.h>
#include <sys/proc.h>
#include <sys/lock.h>
#include <sys/module.h>
#include <sys/queue.h>
#include <sys/linker.h>
#include <sys/fcntl.h>
#include <sys/libkern.h>
#include <sys/nlookup.h>
#include <sys/vnode.h>
#include <sys/sysctl.h>

#include <vm/vm_zone.h>

#ifdef _KERNEL_VIRTUAL
#include <dlfcn.h>
#endif

#ifdef KLD_DEBUG
int kld_debug = 0;
#endif

/* Metadata from the static kernel */
SET_DECLARE(modmetadata_set, struct mod_metadata);
MALLOC_DEFINE(M_LINKER, "kld", "kernel linker");

linker_file_t linker_current_file;
linker_file_t linker_kernel_file;

static struct lock lock;	/* lock for the file list */
static linker_class_list_t classes;
static linker_file_list_t linker_files;
static int next_file_id = 1;

static void
linker_init(void* arg)
{
    lockinit(&lock, "klink", 0, 0);
    TAILQ_INIT(&classes);
    TAILQ_INIT(&linker_files);
}

SYSINIT(linker, SI_BOOT2_KLD, SI_ORDER_FIRST, linker_init, 0);

int
linker_add_class(const char* desc, void* priv,
		 struct linker_class_ops* ops)
{
    linker_class_t lc;

    lc = kmalloc(sizeof(struct linker_class), M_LINKER, M_NOWAIT | M_ZERO);
    if (!lc)
	return ENOMEM;

    lc->desc = desc;
    lc->priv = priv;
    lc->ops = ops;
    TAILQ_INSERT_HEAD(&classes, lc, link);

    return 0;
}

static int
linker_file_sysinit(linker_file_t lf)
{
    struct sysinit** start, ** stop;
    struct sysinit** sipp;
    struct sysinit** xipp;
    struct sysinit* save;
    const moduledata_t *moddata;
    int error;

    KLD_DPF(FILE, ("linker_file_sysinit: calling SYSINITs for %s\n",
		   lf->filename));

    if (linker_file_lookup_set(lf, "sysinit_set", &start, &stop, NULL) != 0)
	return 0; /* XXX is this correct ? No sysinit ? */

    /* HACK ALERT! */
    for (sipp = start; sipp < stop; sipp++) {
	if ((*sipp)->func == module_register_init) {
	    moddata = (*sipp)->udata;
	    error = module_register(moddata, lf);
	    if (error) {
		kprintf("linker_file_sysinit \"%s\" failed to register! %d\n",
		    lf->filename, error);
		return error;
	    }
	}
    }

    /*
     * Perform a bubble sort of the system initialization objects by
     * their subsystem (primary key) and order (secondary key).
     *
     * Since some things care about execution order, this is the
     * operation which ensures continued function.
     */
    for (sipp = start; sipp < stop; sipp++) {
	for (xipp = sipp + 1; xipp < stop; xipp++) {
	    if ((*sipp)->subsystem < (*xipp)->subsystem ||
		 ((*sipp)->subsystem == (*xipp)->subsystem &&
		  (*sipp)->order <= (*xipp)->order))
		continue;	/* skip*/
	    save = *sipp;
	    *sipp = *xipp;
	    *xipp = save;
	}
    }


    /*
     * Traverse the (now) ordered list of system initialization tasks.
     * Perform each task, and continue on to the next task.
     */
    for (sipp = start; sipp < stop; sipp++) {
	if ((*sipp)->subsystem == SI_SPECIAL_DUMMY)
	    continue;	/* skip dummy task(s)*/

	/* Call function */
	(*((*sipp)->func))((*sipp)->udata);
    }
    return 0; /* no errors */
}

static void
linker_file_sysuninit(linker_file_t lf)
{
    struct sysinit** start, ** stop;
    struct sysinit** sipp;
    struct sysinit** xipp;
    struct sysinit* save;

    KLD_DPF(FILE, ("linker_file_sysuninit: calling SYSUNINITs for %s\n",
		   lf->filename));

    if (linker_file_lookup_set(lf, "sysuninit_set", &start, &stop, NULL) != 0)
	return;

    /*
     * Perform a reverse bubble sort of the system initialization objects
     * by their subsystem (primary key) and order (secondary key).
     *
     * Since some things care about execution order, this is the
     * operation which ensures continued function.
     */
    for (sipp = start; sipp < stop; sipp++) {
	for (xipp = sipp + 1; xipp < stop; xipp++) {
	    if ((*sipp)->subsystem > (*xipp)->subsystem ||
		 ((*sipp)->subsystem == (*xipp)->subsystem &&
		  (*sipp)->order >= (*xipp)->order))
		continue;	/* skip*/
	    save = *sipp;
	    *sipp = *xipp;
	    *xipp = save;
	}
    }


    /*
     * Traverse the (now) ordered list of system initialization tasks.
     * Perform each task, and continue on to the next task.
     */
    for (sipp = start; sipp < stop; sipp++) {
	if ((*sipp)->subsystem == SI_SPECIAL_DUMMY)
	    continue;	/* skip dummy task(s)*/

	/* Call function */
	(*((*sipp)->func))((*sipp)->udata);
    }
}

static void
linker_file_register_sysctls(linker_file_t lf)
{
    struct sysctl_oid **start, **stop, **oidp;

    KLD_DPF(FILE, ("linker_file_register_sysctls: registering SYSCTLs for %s\n",
		   lf->filename));

    if (linker_file_lookup_set(lf, "sysctl_set", &start, &stop, NULL) != 0)
	return;
    for (oidp = start; oidp < stop; oidp++)
	sysctl_register_oid(*oidp);
}

static void
linker_file_unregister_sysctls(linker_file_t lf)
{
    struct sysctl_oid **start, **stop, **oidp;

    KLD_DPF(FILE, ("linker_file_unregister_sysctls: registering SYSCTLs for %s\n",
		   lf->filename));

    if (linker_file_lookup_set(lf, "sysctl_set", &start, &stop, NULL) != 0)
	return;
    for (oidp = start; oidp < stop; oidp++)
	sysctl_unregister_oid(*oidp);
}

int
linker_load_file(const char* filename, linker_file_t* result)
{
    linker_class_t lc;
    linker_file_t lf;
    int foundfile, error = 0;
    char *koname = NULL;

    /* Refuse to load modules if securelevel raised */
    if (securelevel > 0 || kernel_mem_readonly)
	return EPERM;

    lf = linker_find_file_by_name(filename);
    if (lf) {
	KLD_DPF(FILE, ("linker_load_file: file %s is already loaded, incrementing refs\n", filename));
	*result = lf;
	lf->refs++;
	goto out;
    }
    if (find_mod_metadata(filename)) {
	if (linker_kernel_file)
	    ++linker_kernel_file->refs;
	*result = linker_kernel_file;
	goto out;
    }

    koname = kmalloc(strlen(filename) + 4, M_LINKER, M_WAITOK);
    ksprintf(koname, "%s.ko", filename);
    lf = NULL;
    foundfile = 0;
    TAILQ_FOREACH(lc, &classes, link) {
	KLD_DPF(FILE, ("linker_load_file: trying to load %s as %s\n",
		       filename, lc->desc));

	error = lc->ops->load_file(koname, &lf);	/* First with .ko */
	if (lf == NULL && error == ENOENT)
	    error = lc->ops->load_file(filename, &lf);	/* Then try without */
	/*
	 * If we got something other than ENOENT, then it exists but we cannot
	 * load it for some other reason.
	 */
	if (error != ENOENT)
	    foundfile = 1;
	if (lf) {
	    linker_file_register_sysctls(lf);
	    error = linker_file_sysinit(lf);

	    *result = lf;
	    goto out;
	}
    }
    /*
     * Less than ideal, but tells the user whether it failed to load or
     * the module was not found.
     */
    if (foundfile) {
	    /*
	     * Format not recognized or otherwise unloadable.
	     * When loading a module that is statically built into
	     * the kernel EEXIST percolates back up as the return
	     * value.  Preserve this so that apps can recognize this
	     * special case.
	     */
	    if (error != EEXIST)
		    error = ENOEXEC;
    } else {
	error = ENOENT;		/* Nothing found */
    }

out:
    if (koname)
	kfree(koname, M_LINKER);
    return error;
}

linker_file_t
linker_find_file_by_name(const char* filename)
{
    linker_file_t lf = 0;
    char *koname;
    int i;

    for (i = strlen(filename); i > 0 && filename[i-1] != '/'; --i)
	;
    filename += i;

    koname = kmalloc(strlen(filename) + 4, M_LINKER, M_WAITOK);
    ksprintf(koname, "%s.ko", filename);

    lockmgr(&lock, LK_SHARED);
    TAILQ_FOREACH(lf, &linker_files, link) {
	if (!strcmp(lf->filename, koname))
	    break;
	if (!strcmp(lf->filename, filename))
	    break;
    }
    lockmgr(&lock, LK_RELEASE);

    if (koname)
	kfree(koname, M_LINKER);
    return lf;
}

linker_file_t
linker_find_file_by_id(int fileid)
{
    linker_file_t lf = 0;

    lockmgr(&lock, LK_SHARED);
    TAILQ_FOREACH(lf, &linker_files, link)
	if (lf->id == fileid)
	    break;
    lockmgr(&lock, LK_RELEASE);

    return lf;
}

linker_file_t
linker_make_file(const char* pathname, void* priv, struct linker_file_ops* ops)
{
    linker_file_t lf = 0;
    int namelen;
    const char *filename;

    filename = rindex(pathname, '/');
    if (filename && filename[1])
	filename++;
    else
	filename = pathname;

    KLD_DPF(FILE, ("linker_make_file: new file, filename=%s\n", filename));
    lockmgr(&lock, LK_EXCLUSIVE);
    namelen = strlen(filename) + 1;
    lf = kmalloc(sizeof(struct linker_file) + namelen, M_LINKER, M_WAITOK);
    bzero(lf, sizeof(*lf));

    lf->refs = 1;
    lf->userrefs = 0;
    lf->flags = 0;
    lf->filename = (char*) (lf + 1);
    strcpy(lf->filename, filename);
    lf->id = next_file_id++;
    lf->ndeps = 0;
    lf->deps = NULL;
    STAILQ_INIT(&lf->common);
    TAILQ_INIT(&lf->modules);

    lf->priv = priv;
    lf->ops = ops;
    TAILQ_INSERT_TAIL(&linker_files, lf, link);

    lockmgr(&lock, LK_RELEASE);
    return lf;
}

int
linker_file_unload(linker_file_t file)
{
    module_t mod, next;
    struct common_symbol* cp;
    int error = 0;
    int i;

    /* Refuse to unload modules if securelevel raised */
    if (securelevel > 0 || kernel_mem_readonly)
	return EPERM;

    KLD_DPF(FILE, ("linker_file_unload: lf->refs=%d\n", file->refs));
    lockmgr(&lock, LK_EXCLUSIVE);
    if (file->refs == 1) {
	KLD_DPF(FILE, ("linker_file_unload: file is unloading, informing modules\n"));
	/*
	 * Temporarily bump file->refs to prevent recursive unloading
	 */
	++file->refs;

	/*
	 * Inform any modules associated with this file.
	 */
	mod = TAILQ_FIRST(&file->modules);
	while (mod) {
	    /*
	     * Give the module a chance to veto the unload.  Note that the
	     * act of unloading the module may cause other modules in the
	     * same file list to be unloaded recursively.
	     */
	    if ((error = module_unload(mod)) != 0) {
		KLD_DPF(FILE, ("linker_file_unload: module %x vetoes unload\n",
			       mod));
		lockmgr(&lock, LK_RELEASE);
		file->refs--;
		goto out;
	    }

	    /*
	     * Recursive relationships may prevent the release from
	     * immediately removing the module, or may remove other
	     * modules in the list.
	     */
	    next = module_getfnext(mod);
	    module_release(mod);
	    mod = next;
	}

	/*
	 * Since we intend to destroy the file structure, we expect all
	 * modules to have been removed by now.
	 */
	for (mod = TAILQ_FIRST(&file->modules);
	     mod;
	     mod = module_getfnext(mod)
	) {
	    kprintf("linker_file_unload: module %p still has refs!\n", mod);
	}
	--file->refs;
    }

    file->refs--;
    if (file->refs > 0) {
	lockmgr(&lock, LK_RELEASE);
	goto out;
    }

    /* Don't try to run SYSUNINITs if we are unloaded due to a link error */
    if (file->flags & LINKER_FILE_LINKED) {
	linker_file_sysuninit(file);
	linker_file_unregister_sysctls(file);
    }

    TAILQ_REMOVE(&linker_files, file, link);
    lockmgr(&lock, LK_RELEASE);

    for (i = 0; i < file->ndeps; i++)
	linker_file_unload(file->deps[i]);
    kfree(file->deps, M_LINKER);

    for (cp = STAILQ_FIRST(&file->common); cp;
	 cp = STAILQ_FIRST(&file->common)) {
	STAILQ_REMOVE(&file->common, cp, common_symbol, link);
	kfree(cp, M_LINKER);
    }

    file->ops->unload(file);
    kfree(file, M_LINKER);

out:
    return error;
}

void
linker_file_add_dependancy(linker_file_t file, linker_file_t dep)
{
    linker_file_t* newdeps;

    newdeps = kmalloc((file->ndeps + 1) * sizeof(linker_file_t*),
		     M_LINKER, M_WAITOK | M_ZERO);

    if (file->deps) {
	bcopy(file->deps, newdeps, file->ndeps * sizeof(linker_file_t*));
	kfree(file->deps, M_LINKER);
    }
    file->deps = newdeps;
    file->deps[file->ndeps] = dep;
    file->ndeps++;
}

/*
 * Locate a linker set and its contents.
 * This is a helper function to avoid linker_if.h exposure elsewhere.
 * Note: firstp and lastp are really void ***
 */
int
linker_file_lookup_set(linker_file_t file, const char *name,
                      void *firstp, void *lastp, int *countp)
{
    return file->ops->lookup_set(file, name, firstp, lastp, countp);
}

int
linker_file_lookup_symbol(linker_file_t file, const char* name, int deps, caddr_t *raddr)
{
    c_linker_sym_t sym;
    linker_symval_t symval;
    linker_file_t lf;
    size_t common_size = 0;
    int i;

    KLD_DPF(SYM, ("linker_file_lookup_symbol: file=%x, name=%s, deps=%d\n",
		  file, name, deps));

    if (file->ops->lookup_symbol(file, name, &sym) == 0) {
	file->ops->symbol_values(file, sym, &symval);

	/*
	 * XXX Assume a common symbol if its value is 0 and it has a non-zero
	 * size, otherwise it could be an absolute symbol with a value of 0.
	 */
	if (symval.value == 0 && symval.size != 0) {
	    /*
	     * For commons, first look them up in the dependancies and
	     * only allocate space if not found there.
	     */
	    common_size = symval.size;
	} else {
	    KLD_DPF(SYM, ("linker_file_lookup_symbol: symbol.value=%x\n", symval.value));
	    *raddr = symval.value;
	    return 0;
	}
    }
    if (deps) {
	for (i = 0; i < file->ndeps; i++) {
	    if (linker_file_lookup_symbol(file->deps[i], name, 0, raddr) == 0) {
		KLD_DPF(SYM, ("linker_file_lookup_symbol: deps value=%x\n", *raddr));
		return 0;
	    }
	}

	/* If we have not found it in the dependencies, search globally */
	TAILQ_FOREACH(lf, &linker_files, link) {
	    /* But skip the current file if it's on the list */
	    if (lf == file)
		continue;
	    /* And skip the files we searched above */
	    for (i = 0; i < file->ndeps; i++)
		if (lf == file->deps[i])
		    break;
	    if (i < file->ndeps)
		continue;
	    if (linker_file_lookup_symbol(lf, name, 0, raddr) == 0) {
		KLD_DPF(SYM, ("linker_file_lookup_symbol: global value=%x\n", *raddr));
		return 0;
	    }
	}
    }

    if (common_size > 0) {
	/*
	 * This is a common symbol which was not found in the
	 * dependancies.  We maintain a simple common symbol table in
	 * the file object.
	 */
	struct common_symbol* cp;

	STAILQ_FOREACH(cp, &file->common, link)
	    if (!strcmp(cp->name, name)) {
		KLD_DPF(SYM, ("linker_file_lookup_symbol: old common value=%x\n", cp->address));
		*raddr = cp->address;
		return 0;
	    }

	/*
	 * Round the symbol size up to align.
	 */
	common_size = (common_size + sizeof(int) - 1) & -sizeof(int);
	cp = kmalloc(sizeof(struct common_symbol)
		    + common_size
		    + strlen(name) + 1,
		    M_LINKER, M_WAITOK | M_ZERO);

	cp->address = (caddr_t) (cp + 1);
	cp->name = cp->address + common_size;
	strcpy(cp->name, name);
	bzero(cp->address, common_size);
	STAILQ_INSERT_TAIL(&file->common, cp, link);

	KLD_DPF(SYM, ("linker_file_lookup_symbol: new common value=%x\n", cp->address));
	*raddr = cp->address;
	return 0;
    }

#ifdef _KERNEL_VIRTUAL
    *raddr = dlsym(RTLD_NEXT, name);
    if (*raddr != NULL) {
	KLD_DPF(SYM, ("linker_file_lookup_symbol: found dlsym=%x\n", *raddr));
	return 0;
    }
#endif

    KLD_DPF(SYM, ("linker_file_lookup_symbol: fail\n"));
    return ENOENT;
}

#ifdef DDB
/*
 * DDB Helpers.  DDB has to look across multiple files with their own
 * symbol tables and string tables.
 *
 * Note that we do not obey list locking protocols here.  We really don't
 * need DDB to hang because somebody's got the lock held.  We'll take the
 * chance that the files list is inconsistant instead.
 */

int
linker_ddb_lookup(const char *symstr, c_linker_sym_t *sym)
{
    linker_file_t lf;

    TAILQ_FOREACH(lf, &linker_files, link) {
	if (lf->ops->lookup_symbol(lf, symstr, sym) == 0)
	    return 0;
    }
    return ENOENT;
}

int
linker_ddb_search_symbol(caddr_t value, c_linker_sym_t *sym, long *diffp)
{
    linker_file_t lf;
    u_long off = (uintptr_t)value;
    u_long diff, bestdiff;
    c_linker_sym_t best;
    c_linker_sym_t es;

    best = 0;
    bestdiff = off;
    TAILQ_FOREACH(lf, &linker_files, link) {
	if (lf->ops->search_symbol(lf, value, &es, &diff) != 0)
	    continue;
	if (es != 0 && diff < bestdiff) {
	    best = es;
	    bestdiff = diff;
	}
	if (bestdiff == 0)
	    break;
    }
    if (best) {
	*sym = best;
	*diffp = bestdiff;
	return 0;
    } else {
	*sym = 0;
	*diffp = off;
	return ENOENT;
    }
}

int
linker_ddb_symbol_values(c_linker_sym_t sym, linker_symval_t *symval)
{
    linker_file_t lf;

    TAILQ_FOREACH(lf, &linker_files, link) {
	if (lf->ops->symbol_values(lf, sym, symval) == 0)
	    return 0;
    }
    return ENOENT;
}

#endif

/*
 * Syscalls.
 */

int
sys_kldload(struct kldload_args *uap)
{
    struct thread *td = curthread;
    char* filename = NULL, *modulename;
    linker_file_t lf;
    int error = 0;

    uap->sysmsg_result = -1;

    if (securelevel > 0 || kernel_mem_readonly)	/* redundant, but that's OK */
	return EPERM;

    if ((error = suser(td)) != 0)
	return error;

    filename = kmalloc(MAXPATHLEN, M_TEMP, M_WAITOK);
    if ((error = copyinstr(uap->file, filename, MAXPATHLEN, NULL)) != 0)
	goto out;

    /* Can't load more than one module with the same name */
    modulename = rindex(filename, '/');
    if (modulename == NULL)
	modulename = filename;
    else
	modulename++;
    if (linker_find_file_by_name(modulename)) {
	error = EEXIST;
	goto out;
    }

    if ((error = linker_load_file(filename, &lf)) != 0)
	goto out;

    lf->userrefs++;
    uap->sysmsg_result = lf->id;

out:
    if (filename)
	kfree(filename, M_TEMP);
    return error;
}

int
sys_kldunload(struct kldunload_args *uap)
{
    struct thread *td = curthread;
    linker_file_t lf;
    int error = 0;

    if (securelevel > 0 || kernel_mem_readonly)	/* redundant, but that's OK */
	return EPERM;

    if ((error = suser(td)) != 0)
	return error;

    lf = linker_find_file_by_id(uap->fileid);
    if (lf) {
	KLD_DPF(FILE, ("kldunload: lf->userrefs=%d\n", lf->userrefs));
	if (lf->userrefs == 0) {
	    kprintf("linkerunload: attempt to unload file that was loaded by the kernel\n");
	    error = EBUSY;
	    goto out;
	}
	lf->userrefs--;
	error = linker_file_unload(lf);
	if (error)
	    lf->userrefs++;
    } else
	error = ENOENT;

out:
    return error;
}

int
sys_kldfind(struct kldfind_args *uap)
{
    char *filename = NULL, *modulename;
    linker_file_t lf;
    int error = 0;

    uap->sysmsg_result = -1;

    filename = kmalloc(MAXPATHLEN, M_TEMP, M_WAITOK);
    if ((error = copyinstr(uap->file, filename, MAXPATHLEN, NULL)) != 0)
	goto out;

    modulename = rindex(filename, '/');
    if (modulename == NULL)
	modulename = filename;

    lf = linker_find_file_by_name(modulename);
    if (lf)
	uap->sysmsg_result = lf->id;
    else
	error = ENOENT;

out:
    if (filename)
	kfree(filename, M_TEMP);
    return error;
}

int
sys_kldnext(struct kldnext_args *uap)
{
    linker_file_t lf;
    int error = 0;

    if (uap->fileid == 0) {
	if (TAILQ_FIRST(&linker_files))
	    uap->sysmsg_result = TAILQ_FIRST(&linker_files)->id;
	else
	    uap->sysmsg_result = 0;
	return 0;
    }

    lf = linker_find_file_by_id(uap->fileid);
    if (lf) {
	if (TAILQ_NEXT(lf, link))
	    uap->sysmsg_result = TAILQ_NEXT(lf, link)->id;
	else
	    uap->sysmsg_result = 0;
    } else
	error = ENOENT;

    return error;
}

int
sys_kldstat(struct kldstat_args *uap)
{
    linker_file_t lf;
    int error = 0;
    int version;
    struct kld_file_stat* stat;
    int namelen;

    lf = linker_find_file_by_id(uap->fileid);
    if (!lf) {
	error = ENOENT;
	goto out;
    }

    stat = uap->stat;

    /*
     * Check the version of the user's structure.
     */
    if ((error = copyin(&stat->version, &version, sizeof(version))) != 0)
	goto out;
    if (version != sizeof(struct kld_file_stat)) {
	error = EINVAL;
	goto out;
    }

    namelen = strlen(lf->filename) + 1;
    if (namelen > MAXPATHLEN)
	namelen = MAXPATHLEN;
    if ((error = copyout(lf->filename, &stat->name[0], namelen)) != 0)
	goto out;
    if ((error = copyout(&lf->refs, &stat->refs, sizeof(int))) != 0)
	goto out;
    if ((error = copyout(&lf->id, &stat->id, sizeof(int))) != 0)
	goto out;
    if ((error = copyout(&lf->address, &stat->address, sizeof(caddr_t))) != 0)
	goto out;
    if ((error = copyout(&lf->size, &stat->size, sizeof(size_t))) != 0)
	goto out;

    uap->sysmsg_result = 0;

out:
    return error;
}

int
sys_kldfirstmod(struct kldfirstmod_args *uap)
{
    linker_file_t lf;
    int error = 0;

    lf = linker_find_file_by_id(uap->fileid);
    if (lf) {
	if (TAILQ_FIRST(&lf->modules))
	    uap->sysmsg_result = module_getid(TAILQ_FIRST(&lf->modules));
	else
	    uap->sysmsg_result = 0;
    } else
	error = ENOENT;

    return error;
}

int
sys_kldsym(struct kldsym_args *uap)
{
    char *symstr = NULL;
    c_linker_sym_t sym;
    linker_symval_t symval;
    linker_file_t lf;
    struct kld_sym_lookup lookup;
    int error = 0;

    if ((error = copyin(uap->data, &lookup, sizeof(lookup))) != 0)
	goto out;
    if (lookup.version != sizeof(lookup) || uap->cmd != KLDSYM_LOOKUP) {
	error = EINVAL;
	goto out;
    }

    symstr = kmalloc(MAXPATHLEN, M_TEMP, M_WAITOK);
    if ((error = copyinstr(lookup.symname, symstr, MAXPATHLEN, NULL)) != 0)
	goto out;

    if (uap->fileid != 0) {
	lf = linker_find_file_by_id(uap->fileid);
	if (lf == NULL) {
	    error = ENOENT;
	    goto out;
	}
	if (lf->ops->lookup_symbol(lf, symstr, &sym) == 0 &&
	    lf->ops->symbol_values(lf, sym, &symval) == 0) {
	    lookup.symvalue = (uintptr_t)symval.value;
	    lookup.symsize = symval.size;
	    error = copyout(&lookup, uap->data, sizeof(lookup));
	} else
	    error = ENOENT;
    } else {
	TAILQ_FOREACH(lf, &linker_files, link) {
	    if (lf->ops->lookup_symbol(lf, symstr, &sym) == 0 &&
		lf->ops->symbol_values(lf, sym, &symval) == 0) {
		lookup.symvalue = (uintptr_t)symval.value;
		lookup.symsize = symval.size;
		error = copyout(&lookup, uap->data, sizeof(lookup));
		break;
	    }
	}
	if (!lf)
	    error = ENOENT;
    }
out:
    if (symstr)
	kfree(symstr, M_TEMP);
    return error;
}

/*
 * Look for module metadata in the static kernel
 */
struct mod_metadata *
find_mod_metadata(const char *modname)
{
    int len;
    struct mod_metadata **mdp;
    struct mod_metadata *mdt;

    /*
     * Strip path prefixes and any dot extension.  MDT_MODULE names
     * are just the module name without a path or ".ko".
     */
    for (len = strlen(modname) - 1; len >= 0; --len) {
	if (modname[len] == '/')
	    break;
    }
    modname += len + 1;
    for (len = 0; modname[len] && modname[len] != '.'; ++len)
	;

    /*
     * Look for the module declaration
     */
    SET_FOREACH(mdp, modmetadata_set) {
	mdt = *mdp;
	if (mdt->md_type != MDT_MODULE)
	    continue;
	if (strlen(mdt->md_cval) == len &&
	    strncmp(mdt->md_cval, modname, len) == 0) {
	    return(mdt);
	}
    }
    return(NULL);
}

/*
 * Preloaded module support
 */
static void
linker_preload(void* arg)
{
    caddr_t		modptr;
    char		*modname;
    char		*modtype;
    linker_file_t	lf;
    linker_class_t	lc;
    int			error;
    struct sysinit	**sipp;
    const moduledata_t	*moddata;
    struct sysinit	**si_start, **si_stop;

    modptr = NULL;
    while ((modptr = preload_search_next_name(modptr)) != NULL) {
	modname = (char *)preload_search_info(modptr, MODINFO_NAME);
	modtype = (char *)preload_search_info(modptr, MODINFO_TYPE);
	if (modname == NULL) {
	    kprintf("Preloaded module at %p does not have a name!\n", modptr);
	    continue;
	}
	if (modtype == NULL) {
	    kprintf("Preloaded module at %p does not have a type!\n", modptr);
	    continue;
	}

	/*
	 * This is a hack at the moment, but what's in FreeBSD-5 is even
	 * worse so I'd rather the hack.
	 */
	kprintf("Preloaded %s \"%s\" at %p", modtype, modname, modptr);
	if (find_mod_metadata(modname)) {
	    kprintf(" (ignored, already in static kernel)\n");
	    continue;
	}
	kprintf(".\n");

	lf = linker_find_file_by_name(modname);
	if (lf) {
	    lf->refs++;
	    lf->userrefs++;
	    continue;
	}
	lf = NULL;
	TAILQ_FOREACH(lc, &classes, link) {
	    error = lc->ops->load_file(modname, &lf);
	    if (error) {
		lf = NULL;
		break;
	    }
	}
	if (lf) {
	    lf->userrefs++;

	    if (linker_file_lookup_set(lf, "sysinit_set", &si_start, &si_stop, NULL) == 0) {
		/* HACK ALERT!
		 * This is to set the sysinit moduledata so that the module
		 * can attach itself to the correct containing file.
		 * The sysinit could be run at *any* time.
		 */
		for (sipp = si_start; sipp < si_stop; sipp++) {
		    if ((*sipp)->func == module_register_init) {
			moddata = (*sipp)->udata;
			error = module_register(moddata, lf);
			if (error)
			    kprintf("Preloaded %s \"%s\" failed to register: %d\n",
				modtype, modname, error);
		    }
		}
		sysinit_add(si_start, si_stop);
	    }
	    linker_file_register_sysctls(lf);
	}
    }
}

SYSINIT(preload, SI_BOOT2_KLD, SI_ORDER_MIDDLE, linker_preload, 0);

/*
 * Search for a not-loaded module by name.
 *
 * Modules may be found in the following locations:
 *
 * - preloaded (result is just the module name)
 * - on disk (result is full path to module)
 *
 * If the module name is qualified in any way (contains path, etc.)
 * the we simply return a copy of it.
 *
 * The search path can be manipulated via sysctl.  Note that we use the ';'
 * character as a separator to be consistent with the bootloader.
 */

static char linker_path[MAXPATHLEN] = "/;/boot;/modules";

SYSCTL_STRING(_kern, OID_AUTO, module_path, CTLFLAG_RW, linker_path,
	      sizeof(linker_path), "module load search path");
TUNABLE_STR("module_path", linker_path, sizeof(linker_path));

static char *
linker_strdup(const char *str)
{
    char	*result;

    result = kmalloc(strlen(str) + 1, M_LINKER, M_WAITOK);
    strcpy(result, str);
    return(result);
}

char *
linker_search_path(const char *name)
{
    struct nlookupdata	nd;
    char		*cp, *ep, *result;
    size_t		name_len, prefix_len;
    int			sep;
    int			error;
    enum vtype		type;

    /* qualified at all? */
    if (index(name, '/'))
	return(linker_strdup(name));

    /* traverse the linker path */
    cp = linker_path;
    name_len = strlen(name);
    for (;;) {

	/* find the end of this component */
	for (ep = cp; (*ep != 0) && (*ep != ';'); ep++)
	    ;
	prefix_len = ep - cp;
	/* if this component doesn't end with a slash, add one */
	if (ep == cp || *(ep - 1) != '/')
	    sep = 1;
	else
	    sep = 0;

	/*
	 * +2 : possible separator, plus terminator.
	 */
	result = kmalloc(prefix_len + name_len + 2, M_LINKER, M_WAITOK);

	strncpy(result, cp, prefix_len);
	if (sep)
	    result[prefix_len++] = '/';
	strcpy(result + prefix_len, name);

	/*
	 * Attempt to open the file, and return the path if we succeed and it's
	 * a regular file.
	 */
	error = nlookup_init(&nd, result, UIO_SYSSPACE, NLC_FOLLOW|NLC_LOCKVP);
	if (error == 0)
	    error = vn_open(&nd, NULL, FREAD, 0);
	if (error == 0) {
	    type = nd.nl_open_vp->v_type;
	    if (type == VREG) {
		nlookup_done(&nd);
		return (result);
	    }
	}
	nlookup_done(&nd);
	kfree(result, M_LINKER);

	if (*ep == 0)
	    break;
	cp = ep + 1;
    }
    return(NULL);
}