kern_linker.c
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kern_linker.c
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	/*-
	* SPDX-License-Identifier: BSD-2-Clause-FreeBSD
	*
	* Copyright (c) 1997-2000 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.
	*/

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

	#include "opt_ddb.h"
	#include "opt_kld.h"
	#include "opt_hwpmc_hooks.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/priv.h>
	#include <sys/proc.h>
	#include <sys/lock.h>
	#include <sys/mutex.h>
	#include <sys/sx.h>
	#include <sys/module.h>
	#include <sys/mount.h>
	#include <sys/linker.h>
	#include <sys/eventhandler.h>
	#include <sys/fcntl.h>
	#include <sys/jail.h>
	#include <sys/libkern.h>
	#include <sys/namei.h>
	#include <sys/vnode.h>
	#include <sys/syscallsubr.h>
	#include <sys/sysctl.h>

	#ifdef DDB
	#include <ddb/ddb.h>
	#endif

	#include <net/vnet.h>

	#include <security/mac/mac_framework.h>

	#include "linker_if.h"

	#ifdef HWPMC_HOOKS
	#include <sys/pmckern.h>
	#endif

	#ifdef KLD_DEBUG
	int kld_debug = 0;
	SYSCTL_INT(_debug, OID_AUTO, kld_debug, CTLFLAG_RWTUN,
	&kld_debug, 0, "Set various levels of KLD debug");
	#endif

	/* These variables are used by kernel debuggers to enumerate loaded files. */
	const int kld_off_address = offsetof(struct linker_file, address);
	const int kld_off_filename = offsetof(struct linker_file, filename);
	const int kld_off_pathname = offsetof(struct linker_file, pathname);
	const int kld_off_next = offsetof(struct linker_file, link.tqe_next);

	/*
	* static char linker_search_path(const char name, struct mod_depend
	* *verinfo);
	*/
	static const char linker_basename(const char path);

	/*
	* Find a currently loaded file given its filename.
	*/
	static linker_file_t linker_find_file_by_name(const char* _filename);

	/*
	* Find a currently loaded file given its file id.
	*/
	static linker_file_t linker_find_file_by_id(int _fileid);

	/* Metadata from the static kernel */
	SET_DECLARE(modmetadata_set, struct mod_metadata);

	MALLOC_DEFINE(M_LINKER, "linker", "kernel linker");

	linker_file_t linker_kernel_file;

	static struct sx kld_sx; /* kernel linker lock */
	static bool kld_busy;

	/*
	* Load counter used by clients to determine if a linker file has been
	* re-loaded. This counter is incremented for each file load.
	*/
	static int loadcnt;

	static linker_class_list_t classes;
	static linker_file_list_t linker_files;
	static int next_file_id = 1;
	static int linker_no_more_classes = 0;

	#define LINKER_GET_NEXT_FILE_ID(a) do { \
	linker_file_t lftmp; \
	\
	if (!cold) \
	sx_assert(&kld_sx, SA_XLOCKED); \
	retry: \
	TAILQ_FOREACH(lftmp, &linker_files, link) { \
	if (next_file_id == lftmp->id) { \
	next_file_id++; \
	goto retry; \
	} \
	} \
	(a) = next_file_id; \
	} while (0)

	/* XXX wrong name; we're looking at version provision tags here, not modules */
	typedef TAILQ_HEAD(, modlist) modlisthead_t;
	struct modlist {
	TAILQ_ENTRY(modlist) link; /* chain together all modules */
	linker_file_t container;
	const char *name;
	int version;
	};
	typedef struct modlist *modlist_t;
	static modlisthead_t found_modules;

	static int linker_file_add_dependency(linker_file_t file,
	linker_file_t dep);
	static caddr_t linker_file_lookup_symbol_internal(linker_file_t file,
	const char* name, int deps);
	static int linker_load_module(const char *kldname,
	const char modname, struct linker_file parent,
	const struct mod_depend verinfo, struct linker_file *lfpp);
	static modlist_t modlist_lookup2(const char name, const struct mod_depend verinfo);

	static void
	linker_init(void *arg)
	{

	sx_init(&kld_sx, "kernel linker");
	TAILQ_INIT(&classes);
	TAILQ_INIT(&linker_files);
	}

	SYSINIT(linker, SI_SUB_KLD, SI_ORDER_FIRST, linker_init, NULL);

	static void
	linker_stop_class_add(void *arg)
	{

	linker_no_more_classes = 1;
	}

	SYSINIT(linker_class, SI_SUB_KLD, SI_ORDER_ANY, linker_stop_class_add, NULL);

	int
	linker_add_class(linker_class_t lc)
	{

	/*
	* We disallow any class registration past SI_ORDER_ANY
	* of SI_SUB_KLD. We bump the reference count to keep the
	* ops from being freed.
	*/
	if (linker_no_more_classes == 1)
	return (EPERM);
	kobj_class_compile((kobj_class_t) lc);
	((kobj_class_t)lc)->refs++; /* XXX: kobj_mtx */
	TAILQ_INSERT_TAIL(&classes, lc, link);
	return (0);
	}

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

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

	sx_assert(&kld_sx, SA_XLOCKED);

	if (linker_file_lookup_set(lf, "sysinit_set", &start, &stop, NULL) != 0)
	return;
	/*
	* 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.
	*/
	sx_xunlock(&kld_sx);
	mtx_lock(&Giant);
	for (sipp = start; sipp < stop; sipp++) {
	if ((*sipp)->subsystem == SI_SUB_DUMMY)
	continue; /* skip dummy task(s) */

	/* Call function */
	(((sipp)->func)) ((*sipp)->udata);
	}
	mtx_unlock(&Giant);
	sx_xlock(&kld_sx);
	}

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

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

	sx_assert(&kld_sx, SA_XLOCKED);

	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.
	*/
	sx_xunlock(&kld_sx);
	mtx_lock(&Giant);
	for (sipp = start; sipp < stop; sipp++) {
	if ((*sipp)->subsystem == SI_SUB_DUMMY)
	continue; /* skip dummy task(s) */

	/* Call function */
	(((sipp)->func)) ((*sipp)->udata);
	}
	mtx_unlock(&Giant);
	sx_xlock(&kld_sx);
	}

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

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

	sx_assert(&kld_sx, SA_XLOCKED);

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

	sx_xunlock(&kld_sx);
	sysctl_wlock();
	for (oidp = start; oidp < stop; oidp++) {
	if (enable)
	sysctl_register_oid(*oidp);
	else
	sysctl_register_disabled_oid(*oidp);
	}
	sysctl_wunlock();
	sx_xlock(&kld_sx);
	}

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

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

	sx_assert(&kld_sx, SA_XLOCKED);

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

	sx_xunlock(&kld_sx);
	sysctl_wlock();
	for (oidp = start; oidp < stop; oidp++)
	sysctl_enable_oid(*oidp);
	sysctl_wunlock();
	sx_xlock(&kld_sx);
	}

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

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

	sx_assert(&kld_sx, SA_XLOCKED);

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

	sx_xunlock(&kld_sx);
	sysctl_wlock();
	for (oidp = start; oidp < stop; oidp++)
	sysctl_unregister_oid(*oidp);
	sysctl_wunlock();
	sx_xlock(&kld_sx);
	}

	static int
	linker_file_register_modules(linker_file_t lf)
	{
	struct mod_metadata start, stop, **mdp;
	const moduledata_t *moddata;
	int first_error, error;

	KLD_DPF(FILE, ("linker_file_register_modules: registering modules"
	" in %s\n", lf->filename));

	sx_assert(&kld_sx, SA_XLOCKED);

	if (linker_file_lookup_set(lf, MDT_SETNAME, &start, &stop, NULL) != 0) {
	/*
	* This fallback should be unnecessary, but if we get booted
	* from boot2 instead of loader and we are missing our
	* metadata then we have to try the best we can.
	*/
	if (lf == linker_kernel_file) {
	start = SET_BEGIN(modmetadata_set);
	stop = SET_LIMIT(modmetadata_set);
	} else
	return (0);
	}
	first_error = 0;
	for (mdp = start; mdp < stop; mdp++) {
	if ((*mdp)->md_type != MDT_MODULE)
	continue;
	moddata = (*mdp)->md_data;
	KLD_DPF(FILE, ("Registering module %s in %s\n",
	moddata->name, lf->filename));
	error = module_register(moddata, lf);
	if (error) {
	printf("Module %s failed to register: %d\n",
	moddata->name, error);
	if (first_error == 0)
	first_error = error;
	}
	}
	return (first_error);
	}

	static void
	linker_init_kernel_modules(void)
	{

	sx_xlock(&kld_sx);
	linker_file_register_modules(linker_kernel_file);
	sx_xunlock(&kld_sx);
	}

	SYSINIT(linker_kernel, SI_SUB_KLD, SI_ORDER_ANY, linker_init_kernel_modules,
	NULL);

	static int
	linker_load_file(const char filename, linker_file_t result)
	{
	linker_class_t lc;
	linker_file_t lf;
	int foundfile, error, modules;

	/* Refuse to load modules if securelevel raised */
	if (prison0.pr_securelevel > 0)
	return (EPERM);

	sx_assert(&kld_sx, SA_XLOCKED);
	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++;
	return (0);
	}
	foundfile = 0;
	error = 0;

	/*
	* We do not need to protect (lock) classes here because there is
	* no class registration past startup (SI_SUB_KLD, SI_ORDER_ANY)
	* and there is no class deregistration mechanism at this time.
	*/
	TAILQ_FOREACH(lc, &classes, link) {
	KLD_DPF(FILE, ("linker_load_file: trying to load %s\n",
	filename));
	error = LINKER_LOAD_FILE(lc, filename, &lf);
	/*
	* 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) {
	error = linker_file_register_modules(lf);
	if (error == EEXIST) {
	linker_file_unload(lf, LINKER_UNLOAD_FORCE);
	return (error);
	}
	modules = !TAILQ_EMPTY(&lf->modules);
	linker_file_register_sysctls(lf, false);
	linker_file_sysinit(lf);
	lf->flags \|= LINKER_FILE_LINKED;

	/*
	* If all of the modules in this file failed
	* to load, unload the file and return an
	* error of ENOEXEC.
	*/
	if (modules && TAILQ_EMPTY(&lf->modules)) {
	linker_file_unload(lf, LINKER_UNLOAD_FORCE);
	return (ENOEXEC);
	}
	linker_file_enable_sysctls(lf);
	EVENTHANDLER_INVOKE(kld_load, lf);
	*result = lf;
	return (0);
	}
	}
	/*
	* Less than ideal, but tells the user whether it failed to load or
	* the module was not found.
	*/
	if (foundfile) {
	/*
	* If the file type has not been recognized by the last try
	* printout a message before to fail.
	*/
	if (error == ENOSYS)
	printf("%s: %s - unsupported file type\n",
	__func__, filename);

	/*
	* 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 like sysinstall
	* can recognize this special case and not post bogus
	* dialog boxes.
	*/
	if (error != EEXIST)
	error = ENOEXEC;
	} else
	error = ENOENT; /* Nothing found */
	return (error);
	}

	int
	linker_reference_module(const char modname, struct mod_depend verinfo,
	linker_file_t *result)
	{
	modlist_t mod;
	int error;

	sx_xlock(&kld_sx);
	if ((mod = modlist_lookup2(modname, verinfo)) != NULL) {
	*result = mod->container;
	(*result)->refs++;
	sx_xunlock(&kld_sx);
	return (0);
	}

	error = linker_load_module(NULL, modname, NULL, verinfo, result);
	sx_xunlock(&kld_sx);
	return (error);
	}

	int
	linker_release_module(const char modname, struct mod_depend verinfo,
	linker_file_t lf)
	{
	modlist_t mod;
	int error;

	sx_xlock(&kld_sx);
	if (lf == NULL) {
	KASSERT(modname != NULL,
	("linker_release_module: no file or name"));
	mod = modlist_lookup2(modname, verinfo);
	if (mod == NULL) {
	sx_xunlock(&kld_sx);
	return (ESRCH);
	}
	lf = mod->container;
	} else
	KASSERT(modname == NULL && verinfo == NULL,
	("linker_release_module: both file and name"));
	error = linker_file_unload(lf, LINKER_UNLOAD_NORMAL);
	sx_xunlock(&kld_sx);
	return (error);
	}

	static linker_file_t
	linker_find_file_by_name(const char *filename)
	{
	linker_file_t lf;
	char *koname;

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

	sx_assert(&kld_sx, SA_XLOCKED);
	TAILQ_FOREACH(lf, &linker_files, link) {
	if (strcmp(lf->filename, koname) == 0)
	break;
	if (strcmp(lf->filename, filename) == 0)
	break;
	}
	free(koname, M_LINKER);
	return (lf);
	}

	static linker_file_t
	linker_find_file_by_id(int fileid)
	{
	linker_file_t lf;

	sx_assert(&kld_sx, SA_XLOCKED);
	TAILQ_FOREACH(lf, &linker_files, link)
	if (lf->id == fileid && lf->flags & LINKER_FILE_LINKED)
	break;
	return (lf);
	}

	int
	linker_file_foreach(linker_predicate_t predicate, void context)
	{
	linker_file_t lf;
	int retval = 0;

	sx_xlock(&kld_sx);
	TAILQ_FOREACH(lf, &linker_files, link) {
	retval = predicate(lf, context);
	if (retval != 0)
	break;
	}
	sx_xunlock(&kld_sx);
	return (retval);
	}

	linker_file_t
	linker_make_file(const char *pathname, linker_class_t lc)
	{
	linker_file_t lf;
	const char *filename;

	if (!cold)
	sx_assert(&kld_sx, SA_XLOCKED);
	filename = linker_basename(pathname);

	KLD_DPF(FILE, ("linker_make_file: new file, filename='%s' for pathname='%s'\n", filename, pathname));
	lf = (linker_file_t)kobj_create((kobj_class_t)lc, M_LINKER, M_WAITOK);
	if (lf == NULL)
	return (NULL);
	lf->ctors_addr = 0;
	lf->ctors_size = 0;
	lf->dtors_addr = 0;
	lf->dtors_size = 0;
	lf->refs = 1;
	lf->userrefs = 0;
	lf->flags = 0;
	lf->filename = strdup(filename, M_LINKER);
	lf->pathname = strdup(pathname, M_LINKER);
	LINKER_GET_NEXT_FILE_ID(lf->id);
	lf->ndeps = 0;
	lf->deps = NULL;
	lf->loadcnt = ++loadcnt;
	#ifdef __arm__
	lf->exidx_addr = 0;
	lf->exidx_size = 0;
	#endif
	STAILQ_INIT(&lf->common);
	TAILQ_INIT(&lf->modules);
	TAILQ_INSERT_TAIL(&linker_files, lf, link);
	return (lf);
	}

	int
	linker_file_unload(linker_file_t file, int flags)
	{
	module_t mod, next;
	modlist_t ml, nextml;
	struct common_symbol *cp;
	int error, i;

	/* Refuse to unload modules if securelevel raised. */
	if (prison0.pr_securelevel > 0)
	return (EPERM);

	sx_assert(&kld_sx, SA_XLOCKED);
	KLD_DPF(FILE, ("linker_file_unload: lf->refs=%d\n", file->refs));

	/* Easy case of just dropping a reference. */
	if (file->refs > 1) {
	file->refs--;
	return (0);
	}

	/* Give eventhandlers a chance to prevent the unload. */
	error = 0;
	EVENTHANDLER_INVOKE(kld_unload_try, file, &error);
	if (error != 0)
	return (EBUSY);

	KLD_DPF(FILE, ("linker_file_unload: file is unloading,"
	" informing modules\n"));

	/*
	* Quiesce all the modules to give them a chance to veto the unload.
	*/
	MOD_SLOCK;
	for (mod = TAILQ_FIRST(&file->modules); mod;
	mod = module_getfnext(mod)) {
	error = module_quiesce(mod);
	if (error != 0 && flags != LINKER_UNLOAD_FORCE) {
	KLD_DPF(FILE, ("linker_file_unload: module %s"
	" vetoed unload\n", module_getname(mod)));
	/*
	* XXX: Do we need to tell all the quiesced modules
	* that they can resume work now via a new module
	* event?
	*/
	MOD_SUNLOCK;
	return (error);
	}
	}
	MOD_SUNLOCK;

	/*
	* Inform any modules associated with this file that they are
	* being unloaded.
	*/
	MOD_XLOCK;
	for (mod = TAILQ_FIRST(&file->modules); mod; mod = next) {
	next = module_getfnext(mod);
	MOD_XUNLOCK;

	/*
	* Give the module a chance to veto the unload.
	*/
	if ((error = module_unload(mod)) != 0) {
	#ifdef KLD_DEBUG
	MOD_SLOCK;
	KLD_DPF(FILE, ("linker_file_unload: module %s"
	" failed unload\n", module_getname(mod)));
	MOD_SUNLOCK;
	#endif
	return (error);
	}
	MOD_XLOCK;
	module_release(mod);
	}
	MOD_XUNLOCK;

	TAILQ_FOREACH_SAFE(ml, &found_modules, link, nextml) {
	if (ml->container == file) {
	TAILQ_REMOVE(&found_modules, ml, link);
	free(ml, M_LINKER);
	}
	}

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

	if (file->deps) {
	for (i = 0; i < file->ndeps; i++)
	linker_file_unload(file->deps[i], flags);
	free(file->deps, M_LINKER);
	file->deps = NULL;
	}
	while ((cp = STAILQ_FIRST(&file->common)) != NULL) {
	STAILQ_REMOVE_HEAD(&file->common, link);
	free(cp, M_LINKER);
	}

	LINKER_UNLOAD(file);

	EVENTHANDLER_INVOKE(kld_unload, file->filename, file->address,
	file->size);

	if (file->filename) {
	free(file->filename, M_LINKER);
	file->filename = NULL;
	}
	if (file->pathname) {
	free(file->pathname, M_LINKER);
	file->pathname = NULL;
	}
	kobj_delete((kobj_t) file, M_LINKER);
	return (0);
	}

	int
	linker_ctf_get(linker_file_t file, linker_ctf_t *lc)
	{
	return (LINKER_CTF_GET(file, lc));
	}

	static int
	linker_file_add_dependency(linker_file_t file, linker_file_t dep)
	{
	linker_file_t *newdeps;

	sx_assert(&kld_sx, SA_XLOCKED);
	file->deps = realloc(file->deps, (file->ndeps + 1) * sizeof(*newdeps),
	M_LINKER, M_WAITOK \| M_ZERO);
	file->deps[file->ndeps] = dep;
	file->ndeps++;
	KLD_DPF(FILE, ("linker_file_add_dependency:"
	" adding %s as dependency for %s\n",
	dep->filename, file->filename));
	return (0);
	}

	/*
	* 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 **.
	* This function is used in this file so we can avoid having lots of (void **)
	* casts.
	*/
	int
	linker_file_lookup_set(linker_file_t file, const char *name,
	void firstp, void lastp, int *countp)
	{

	sx_assert(&kld_sx, SA_LOCKED);
	return (LINKER_LOOKUP_SET(file, name, firstp, lastp, countp));
	}

	/*
	* List all functions in a file.
	*/
	int
	linker_file_function_listall(linker_file_t lf,
	linker_function_nameval_callback_t callback_func, void *arg)
	{
	return (LINKER_EACH_FUNCTION_NAMEVAL(lf, callback_func, arg));
	}

	caddr_t
	linker_file_lookup_symbol(linker_file_t file, const char *name, int deps)
	{
	caddr_t sym;
	int locked;

	locked = sx_xlocked(&kld_sx);
	if (!locked)
	sx_xlock(&kld_sx);
	sym = linker_file_lookup_symbol_internal(file, name, deps);
	if (!locked)
	sx_xunlock(&kld_sx);
	return (sym);
	}

	static caddr_t
	linker_file_lookup_symbol_internal(linker_file_t file, const char *name,
	int deps)
	{
	c_linker_sym_t sym;
	linker_symval_t symval;
	caddr_t address;
	size_t common_size = 0;
	int i;

	sx_assert(&kld_sx, SA_XLOCKED);
	KLD_DPF(SYM, ("linker_file_lookup_symbol: file=%p, name=%s, deps=%d\n",
	file, name, deps));

	if (LINKER_LOOKUP_SYMBOL(file, name, &sym) == 0) {
	LINKER_SYMBOL_VALUES(file, sym, &symval);
	if (symval.value == 0)
	/*
	* For commons, first look them up in the
	* dependencies and only allocate space if not found
	* there.
	*/
	common_size = symval.size;
	else {
	KLD_DPF(SYM, ("linker_file_lookup_symbol: symbol"
	".value=%p\n", symval.value));
	return (symval.value);
	}
	}
	if (deps) {
	for (i = 0; i < file->ndeps; i++) {
	address = linker_file_lookup_symbol_internal(
	file->deps[i], name, 0);
	if (address) {
	KLD_DPF(SYM, ("linker_file_lookup_symbol:"
	" deps value=%p\n", address));
	return (address);
	}
	}
	}
	if (common_size > 0) {
	/*
	* This is a common symbol which was not found in the
	* dependencies. 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) == 0) {
	KLD_DPF(SYM, ("linker_file_lookup_symbol:"
	" old common value=%p\n", cp->address));
	return (cp->address);
	}
	}
	/*
	* Round the symbol size up to align.
	*/
	common_size = (common_size + sizeof(int) - 1) & -sizeof(int);
	cp = malloc(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=%p\n", cp->address));
	return (cp->address);
	}
	KLD_DPF(SYM, ("linker_file_lookup_symbol: fail\n"));
	return (0);
	}

	/*
	* Both DDB and stack(9) rely on the kernel linker to provide forward and
	* backward lookup of symbols. However, DDB and sometimes stack(9) need to
	* do this in a lockfree manner. We provide a set of internal helper
	* routines to perform these operations without locks, and then wrappers that
	* optionally lock.
	*
	* linker_debug_lookup() is ifdef DDB as currently it's only used by DDB.
	*/
	#ifdef DDB
	static int
	linker_debug_lookup(const char symstr, c_linker_sym_t sym)
	{
	linker_file_t lf;

	TAILQ_FOREACH(lf, &linker_files, link) {
	if (LINKER_LOOKUP_SYMBOL(lf, symstr, sym) == 0)
	return (0);
	}
	return (ENOENT);
	}
	#endif

	static int
	linker_debug_search_symbol(caddr_t value, c_linker_sym_t sym, long diffp)
	{
	linker_file_t lf;
	c_linker_sym_t best, es;
	u_long diff, bestdiff, off;

	best = 0;
	off = (uintptr_t)value;
	bestdiff = off;
	TAILQ_FOREACH(lf, &linker_files, link) {
	if (LINKER_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);
	}
	}

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

	TAILQ_FOREACH(lf, &linker_files, link) {
	if (LINKER_SYMBOL_VALUES(lf, sym, symval) == 0)
	return (0);
	}
	return (ENOENT);
	}

	static int
	linker_debug_search_symbol_name(caddr_t value, char *buf, u_int buflen,
	long *offset)
	{
	linker_symval_t symval;
	c_linker_sym_t sym;
	int error;

	*offset = 0;
	error = linker_debug_search_symbol(value, &sym, offset);
	if (error)
	return (error);
	error = linker_debug_symbol_values(sym, &symval);
	if (error)
	return (error);
	strlcpy(buf, symval.name, buflen);
	return (0);
	}

	/*
	* 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 inconsistent instead.
	*/
	#ifdef DDB
	int
	linker_ddb_lookup(const char symstr, c_linker_sym_t sym)
	{

	return (linker_debug_lookup(symstr, sym));
	}
	#endif

	int
	linker_ddb_search_symbol(caddr_t value, c_linker_sym_t sym, long diffp)
	{

	return (linker_debug_search_symbol(value, sym, diffp));
	}

	int
	linker_ddb_symbol_values(c_linker_sym_t sym, linker_symval_t *symval)
	{

	return (linker_debug_symbol_values(sym, symval));
	}

	int
	linker_ddb_search_symbol_name(caddr_t value, char *buf, u_int buflen,
	long *offset)
	{

	return (linker_debug_search_symbol_name(value, buf, buflen, offset));
	}

	/*
	* stack(9) helper for non-debugging environemnts. Unlike DDB helpers, we do
	* obey locking protocols, and offer a significantly less complex interface.
	*/
	int
	linker_search_symbol_name_flags(caddr_t value, char *buf, u_int buflen,
	long *offset, int flags)
	{
	int error;

	KASSERT((flags & (M_NOWAIT \| M_WAITOK)) != 0 &&
	(flags & (M_NOWAIT \| M_WAITOK)) != (M_NOWAIT \| M_WAITOK),
	("%s: bad flags: 0x%x", __func__, flags));

	if (flags & M_NOWAIT) {
	if (!sx_try_slock(&kld_sx))
	return (EWOULDBLOCK);
	} else
	sx_slock(&kld_sx);

	error = linker_debug_search_symbol_name(value, buf, buflen, offset);
	sx_sunlock(&kld_sx);
	return (error);
	}

	int
	linker_search_symbol_name(caddr_t value, char *buf, u_int buflen,
	long *offset)
	{

	return (linker_search_symbol_name_flags(value, buf, buflen, offset,
	M_WAITOK));
	}

	int
	linker_kldload_busy(int flags)
	{
	int error;

	MPASS((flags & ~(LINKER_UB_UNLOCK \| LINKER_UB_LOCKED \|
	LINKER_UB_PCATCH)) == 0);
	if ((flags & LINKER_UB_LOCKED) != 0)
	sx_assert(&kld_sx, SA_XLOCKED);

	if ((flags & LINKER_UB_LOCKED) == 0)
	sx_xlock(&kld_sx);
	while (kld_busy) {
	error = sx_sleep(&kld_busy, &kld_sx,
	(flags & LINKER_UB_PCATCH) != 0 ? PCATCH : 0,
	"kldbusy", 0);
	if (error != 0) {
	if ((flags & LINKER_UB_UNLOCK) != 0)
	sx_xunlock(&kld_sx);
	return (error);
	}
	}
	kld_busy = true;
	if ((flags & LINKER_UB_UNLOCK) != 0)
	sx_xunlock(&kld_sx);
	return (0);
	}

	void
	linker_kldload_unbusy(int flags)
	{
	MPASS((flags & ~LINKER_UB_LOCKED) == 0);
	if ((flags & LINKER_UB_LOCKED) != 0)
	sx_assert(&kld_sx, SA_XLOCKED);

	if ((flags & LINKER_UB_LOCKED) == 0)
	sx_xlock(&kld_sx);
	MPASS(kld_busy);
	kld_busy = false;
	wakeup(&kld_busy);
	sx_xunlock(&kld_sx);
	}

	/*
	* Syscalls.
	*/
	int
	kern_kldload(struct thread td, const char file, int *fileid)
	{
	const char kldname, modname;
	linker_file_t lf;
	int error;

	if ((error = securelevel_gt(td->td_ucred, 0)) != 0)
	return (error);

	if ((error = priv_check(td, PRIV_KLD_LOAD)) != 0)
	return (error);

	/*
	* If file does not contain a qualified name or any dot in it
	* (kldname.ko, or kldname.ver.ko) treat it as an interface
	* name.
	*/
	if (strchr(file, '/') \|\| strchr(file, '.')) {
	kldname = file;
	modname = NULL;
	} else {
	kldname = NULL;
	modname = file;
	}

	error = linker_kldload_busy(LINKER_UB_PCATCH);
	if (error != 0) {
	sx_xunlock(&kld_sx);
	return (error);
	}

	/*
	* It is possible that kldloaded module will attach a new ifnet,
	* so vnet context must be set when this ocurs.
	*/
	CURVNET_SET(TD_TO_VNET(td));

	error = linker_load_module(kldname, modname, NULL, NULL, &lf);
	CURVNET_RESTORE();

	if (error == 0) {
	lf->userrefs++;
	if (fileid != NULL)
	*fileid = lf->id;
	}
	linker_kldload_unbusy(LINKER_UB_LOCKED);
	return (error);
	}

	int
	sys_kldload(struct thread td, struct kldload_args uap)
	{
	char *pathname = NULL;
	int error, fileid;

	td->td_retval[0] = -1;

	pathname = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
	error = copyinstr(uap->file, pathname, MAXPATHLEN, NULL);
	if (error == 0) {
	error = kern_kldload(td, pathname, &fileid);
	if (error == 0)
	td->td_retval[0] = fileid;
	}
	free(pathname, M_TEMP);
	return (error);
	}

	int
	kern_kldunload(struct thread *td, int fileid, int flags)
	{
	linker_file_t lf;
	int error = 0;

	if ((error = securelevel_gt(td->td_ucred, 0)) != 0)
	return (error);

	if ((error = priv_check(td, PRIV_KLD_UNLOAD)) != 0)
	return (error);

	error = linker_kldload_busy(LINKER_UB_PCATCH);
	if (error != 0) {
	sx_xunlock(&kld_sx);
	return (error);
	}

	CURVNET_SET(TD_TO_VNET(td));
	lf = linker_find_file_by_id(fileid);
	if (lf) {
	KLD_DPF(FILE, ("kldunload: lf->userrefs=%d\n", lf->userrefs));

	if (lf->userrefs == 0) {
	/*
	* XXX: maybe LINKER_UNLOAD_FORCE should override ?
	*/
	printf("kldunload: attempt to unload file that was"
	" loaded by the kernel\n");
	error = EBUSY;
	} else {
	lf->userrefs--;
	error = linker_file_unload(lf, flags);
	if (error)
	lf->userrefs++;
	}
	} else
	error = ENOENT;
	CURVNET_RESTORE();
	linker_kldload_unbusy(LINKER_UB_LOCKED);
	return (error);
	}

	int
	sys_kldunload(struct thread td, struct kldunload_args uap)
	{

	return (kern_kldunload(td, uap->fileid, LINKER_UNLOAD_NORMAL));
	}

	int
	sys_kldunloadf(struct thread td, struct kldunloadf_args uap)
	{

	if (uap->flags != LINKER_UNLOAD_NORMAL &&
	uap->flags != LINKER_UNLOAD_FORCE)
	return (EINVAL);
	return (kern_kldunload(td, uap->fileid, uap->flags));
	}

	int
	sys_kldfind(struct thread td, struct kldfind_args uap)
	{
	char *pathname;
	const char *filename;
	linker_file_t lf;
	int error;

	#ifdef MAC
	error = mac_kld_check_stat(td->td_ucred);
	if (error)
	return (error);
	#endif

	td->td_retval[0] = -1;

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

	filename = linker_basename(pathname);
	sx_xlock(&kld_sx);
	lf = linker_find_file_by_name(filename);
	if (lf)
	td->td_retval[0] = lf->id;
	else
	error = ENOENT;
	sx_xunlock(&kld_sx);
	out:
	free(pathname, M_TEMP);
	return (error);
	}

	int
	sys_kldnext(struct thread td, struct kldnext_args uap)
	{
	linker_file_t lf;
	int error = 0;

	#ifdef MAC
	error = mac_kld_check_stat(td->td_ucred);
	if (error)
	return (error);
	#endif

	sx_xlock(&kld_sx);
	if (uap->fileid == 0)
	lf = TAILQ_FIRST(&linker_files);
	else {
	lf = linker_find_file_by_id(uap->fileid);
	if (lf == NULL) {
	error = ENOENT;
	goto out;
	}
	lf = TAILQ_NEXT(lf, link);
	}

	/* Skip partially loaded files. */
	while (lf != NULL && !(lf->flags & LINKER_FILE_LINKED))
	lf = TAILQ_NEXT(lf, link);

	if (lf)
	td->td_retval[0] = lf->id;
	else
	td->td_retval[0] = 0;
	out:
	sx_xunlock(&kld_sx);
	return (error);
	}

	int
	sys_kldstat(struct thread td, struct kldstat_args uap)
	{
	struct kld_file_stat *stat;
	int error, version;

	/*
	* Check the version of the user's structure.
	*/
	if ((error = copyin(&uap->stat->version, &version, sizeof(version)))
	!= 0)
	return (error);
	if (version != sizeof(struct kld_file_stat_1) &&
	version != sizeof(struct kld_file_stat))
	return (EINVAL);

	stat = malloc(sizeof(*stat), M_TEMP, M_WAITOK \| M_ZERO);
	error = kern_kldstat(td, uap->fileid, stat);
	if (error == 0)
	error = copyout(stat, uap->stat, version);
	free(stat, M_TEMP);
	return (error);
	}

	int
	kern_kldstat(struct thread td, int fileid, struct kld_file_stat stat)
	{
	linker_file_t lf;
	int namelen;
	#ifdef MAC
	int error;

	error = mac_kld_check_stat(td->td_ucred);
	if (error)
	return (error);
	#endif

	sx_xlock(&kld_sx);
	lf = linker_find_file_by_id(fileid);
	if (lf == NULL) {
	sx_xunlock(&kld_sx);
	return (ENOENT);
	}

	/* Version 1 fields: */
	namelen = strlen(lf->filename) + 1;
	if (namelen > sizeof(stat->name))
	namelen = sizeof(stat->name);
	bcopy(lf->filename, &stat->name[0], namelen);
	stat->refs = lf->refs;
	stat->id = lf->id;
	stat->address = lf->address;
	stat->size = lf->size;
	/* Version 2 fields: */
	namelen = strlen(lf->pathname) + 1;
	if (namelen > sizeof(stat->pathname))
	namelen = sizeof(stat->pathname);
	bcopy(lf->pathname, &stat->pathname[0], namelen);
	sx_xunlock(&kld_sx);

	td->td_retval[0] = 0;
	return (0);
	}

	#ifdef DDB
	DB_COMMAND(kldstat, db_kldstat)
	{
	linker_file_t lf;

	#define POINTER_WIDTH ((int)(sizeof(void ) 2 + 2))
	db_printf("Id Refs Address%*c Size Name\n", POINTER_WIDTH - 7, ' ');
	#undef POINTER_WIDTH
	TAILQ_FOREACH(lf, &linker_files, link) {
	if (db_pager_quit)
	return;
	db_printf("%2d %4d %p %-8zx %s\n", lf->id, lf->refs,
	lf->address, lf->size, lf->filename);
	}
	}
	#endif /* DDB */

	int
	sys_kldfirstmod(struct thread td, struct kldfirstmod_args uap)
	{
	linker_file_t lf;
	module_t mp;
	int error = 0;

	#ifdef MAC
	error = mac_kld_check_stat(td->td_ucred);
	if (error)
	return (error);
	#endif

	sx_xlock(&kld_sx);
	lf = linker_find_file_by_id(uap->fileid);
	if (lf) {
	MOD_SLOCK;
	mp = TAILQ_FIRST(&lf->modules);
	if (mp != NULL)
	td->td_retval[0] = module_getid(mp);
	else
	td->td_retval[0] = 0;
	MOD_SUNLOCK;
	} else
	error = ENOENT;
	sx_xunlock(&kld_sx);
	return (error);
	}

	int
	sys_kldsym(struct thread td, 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;

	#ifdef MAC
	error = mac_kld_check_stat(td->td_ucred);
	if (error)
	return (error);
	#endif

	if ((error = copyin(uap->data, &lookup, sizeof(lookup))) != 0)
	return (error);
	if (lookup.version != sizeof(lookup) \|\|
	uap->cmd != KLDSYM_LOOKUP)
	return (EINVAL);
	symstr = malloc(MAXPATHLEN, M_TEMP, M_WAITOK);
	if ((error = copyinstr(lookup.symname, symstr, MAXPATHLEN, NULL)) != 0)
	goto out;
	sx_xlock(&kld_sx);
	if (uap->fileid != 0) {
	lf = linker_find_file_by_id(uap->fileid);
	if (lf == NULL)
	error = ENOENT;
	else if (LINKER_LOOKUP_SYMBOL(lf, symstr, &sym) == 0 &&
	LINKER_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 (LINKER_LOOKUP_SYMBOL(lf, symstr, &sym) == 0 &&
	LINKER_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 == NULL)
	error = ENOENT;
	}
	sx_xunlock(&kld_sx);
	out:
	free(symstr, M_TEMP);
	return (error);
	}

	/*
	* Preloaded module support
	*/

	static modlist_t
	modlist_lookup(const char *name, int ver)
	{
	modlist_t mod;

	TAILQ_FOREACH(mod, &found_modules, link) {
	if (strcmp(mod->name, name) == 0 &&
	(ver == 0 \|\| mod->version == ver))
	return (mod);
	}
	return (NULL);
	}

	static modlist_t
	modlist_lookup2(const char name, const struct mod_depend verinfo)
	{
	modlist_t mod, bestmod;
	int ver;

	if (verinfo == NULL)
	return (modlist_lookup(name, 0));
	bestmod = NULL;
	TAILQ_FOREACH(mod, &found_modules, link) {
	if (strcmp(mod->name, name) != 0)
	continue;
	ver = mod->version;
	if (ver == verinfo->md_ver_preferred)
	return (mod);
	if (ver >= verinfo->md_ver_minimum &&
	ver <= verinfo->md_ver_maximum &&
	(bestmod == NULL \|\| ver > bestmod->version))
	bestmod = mod;
	}
	return (bestmod);
	}

	static modlist_t
	modlist_newmodule(const char *modname, int version, linker_file_t container)
	{
	modlist_t mod;

	mod = malloc(sizeof(struct modlist), M_LINKER, M_NOWAIT \| M_ZERO);
	if (mod == NULL)
	panic("no memory for module list");
	mod->container = container;
	mod->name = modname;
	mod->version = version;
	TAILQ_INSERT_TAIL(&found_modules, mod, link);
	return (mod);
	}

	static void
	linker_addmodules(linker_file_t lf, struct mod_metadata **start,
	struct mod_metadata **stop, int preload)
	{
	struct mod_metadata mp, *mdp;
	const char *modname;
	int ver;

	for (mdp = start; mdp < stop; mdp++) {
	mp = *mdp;
	if (mp->md_type != MDT_VERSION)
	continue;
	modname = mp->md_cval;
	ver = ((const struct mod_version *)mp->md_data)->mv_version;
	if (modlist_lookup(modname, ver) != NULL) {
	printf("module %s already present!\n", modname);
	/* XXX what can we do? this is a build error. :-( */
	continue;
	}
	modlist_newmodule(modname, ver, lf);
	}
	}

	static void
	linker_preload(void *arg)
	{
	caddr_t modptr;
	const char modname, nmodname;
	char *modtype;
	linker_file_t lf, nlf;
	linker_class_t lc;
	int error;
	linker_file_list_t loaded_files;
	linker_file_list_t depended_files;
	struct mod_metadata mp, nmp;
	struct mod_metadata start, stop, mdp, nmdp;
	const struct mod_depend *verinfo;
	int nver;
	int resolves;
	modlist_t mod;
	struct sysinit si_start, si_stop;

	TAILQ_INIT(&loaded_files);
	TAILQ_INIT(&depended_files);
	TAILQ_INIT(&found_modules);
	error = 0;

	modptr = NULL;
	sx_xlock(&kld_sx);
	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) {
	printf("Preloaded module at %p does not have a"
	" name!\n", modptr);
	continue;
	}
	if (modtype == NULL) {
	printf("Preloaded module at %p does not have a type!\n",
	modptr);
	continue;
	}
	if (bootverbose)
	printf("Preloaded %s \"%s\" at %p.\n", modtype, modname,
	modptr);
	lf = NULL;
	TAILQ_FOREACH(lc, &classes, link) {
	error = LINKER_LINK_PRELOAD(lc, modname, &lf);
	if (!error)
	break;
	lf = NULL;
	}
	if (lf)
	TAILQ_INSERT_TAIL(&loaded_files, lf, loaded);
	}

	/*
	* First get a list of stuff in the kernel.
	*/
	if (linker_file_lookup_set(linker_kernel_file, MDT_SETNAME, &start,
	&stop, NULL) == 0)
	linker_addmodules(linker_kernel_file, start, stop, 1);

	/*
	* This is a once-off kinky bubble sort to resolve relocation
	* dependency requirements.
	*/
	restart:
	TAILQ_FOREACH(lf, &loaded_files, loaded) {
	error = linker_file_lookup_set(lf, MDT_SETNAME, &start,
	&stop, NULL);
	/*
	* First, look to see if we would successfully link with this
	* stuff.
	*/
	resolves = 1; /* unless we know otherwise */
	if (!error) {
	for (mdp = start; mdp < stop; mdp++) {
	mp = *mdp;
	if (mp->md_type != MDT_DEPEND)
	continue;
	modname = mp->md_cval;
	verinfo = mp->md_data;
	for (nmdp = start; nmdp < stop; nmdp++) {
	nmp = *nmdp;
	if (nmp->md_type != MDT_VERSION)
	continue;
	nmodname = nmp->md_cval;
	if (strcmp(modname, nmodname) == 0)
	break;
	}
	if (nmdp < stop) /* it's a self reference */
	continue;

	/*
	* ok, the module isn't here yet, we
	* are not finished
	*/
	if (modlist_lookup2(modname, verinfo) == NULL)
	resolves = 0;
	}
	}
	/*
	* OK, if we found our modules, we can link. So, "provide"
	* the modules inside and add it to the end of the link order
	* list.
	*/
	if (resolves) {
	if (!error) {
	for (mdp = start; mdp < stop; mdp++) {
	mp = *mdp;
	if (mp->md_type != MDT_VERSION)
	continue;
	modname = mp->md_cval;
	nver = ((const struct mod_version *)
	mp->md_data)->mv_version;
	if (modlist_lookup(modname,
	nver) != NULL) {
	printf("module %s already"
	" present!\n", modname);
	TAILQ_REMOVE(&loaded_files,
	lf, loaded);
	linker_file_unload(lf,
	LINKER_UNLOAD_FORCE);
	/* we changed tailq next ptr */
	goto restart;
	}
	modlist_newmodule(modname, nver, lf);
	}
	}
	TAILQ_REMOVE(&loaded_files, lf, loaded);
	TAILQ_INSERT_TAIL(&depended_files, lf, loaded);
	/*
	* Since we provided modules, we need to restart the
	* sort so that the previous files that depend on us
	* have a chance. Also, we've busted the tailq next
	* pointer with the REMOVE.
	*/
	goto restart;
	}
	}

	/*
	* At this point, we check to see what could not be resolved..
	*/
	while ((lf = TAILQ_FIRST(&loaded_files)) != NULL) {
	TAILQ_REMOVE(&loaded_files, lf, loaded);
	printf("KLD file %s is missing dependencies\n", lf->filename);
	linker_file_unload(lf, LINKER_UNLOAD_FORCE);
	}

	/*
	* We made it. Finish off the linking in the order we determined.
	*/
	TAILQ_FOREACH_SAFE(lf, &depended_files, loaded, nlf) {
	if (linker_kernel_file) {
	linker_kernel_file->refs++;
	error = linker_file_add_dependency(lf,
	linker_kernel_file);
	if (error)
	panic("cannot add dependency");
	}
	error = linker_file_lookup_set(lf, MDT_SETNAME, &start,
	&stop, NULL);
	if (!error) {
	for (mdp = start; mdp < stop; mdp++) {
	mp = *mdp;
	if (mp->md_type != MDT_DEPEND)
	continue;
	modname = mp->md_cval;
	verinfo = mp->md_data;
	mod = modlist_lookup2(modname, verinfo);
	if (mod == NULL) {
	printf("KLD file %s - cannot find "
	"dependency \"%s\"\n",
	lf->filename, modname);
	goto fail;
	}
	/* Don't count self-dependencies */
	if (lf == mod->container)
	continue;
	mod->container->refs++;
	error = linker_file_add_dependency(lf,
	mod->container);
	if (error)
	panic("cannot add dependency");
	}
	}
	/*
	* Now do relocation etc using the symbol search paths
	* established by the dependencies
	*/
	error = LINKER_LINK_PRELOAD_FINISH(lf);
	if (error) {
	printf("KLD file %s - could not finalize loading\n",
	lf->filename);
	goto fail;
	}
	linker_file_register_modules(lf);
	if (!TAILQ_EMPTY(&lf->modules))
	lf->flags \|= LINKER_FILE_MODULES;
	if (linker_file_lookup_set(lf, "sysinit_set", &si_start,
	&si_stop, NULL) == 0)
	sysinit_add(si_start, si_stop);
	linker_file_register_sysctls(lf, true);
	lf->flags \|= LINKER_FILE_LINKED;
	continue;
	fail:
	TAILQ_REMOVE(&depended_files, lf, loaded);
	linker_file_unload(lf, LINKER_UNLOAD_FORCE);
	}
	sx_xunlock(&kld_sx);
	/* woohoo! we made it! */
	}

	SYSINIT(preload, SI_SUB_KLD, SI_ORDER_MIDDLE, linker_preload, NULL);

	/*
	* Handle preload files that failed to load any modules.
	*/
	static void
	linker_preload_finish(void *arg)
	{
	linker_file_t lf, nlf;

	sx_xlock(&kld_sx);
	TAILQ_FOREACH_SAFE(lf, &linker_files, link, nlf) {
	/*
	* If all of the modules in this file failed to load, unload
	* the file and return an error of ENOEXEC. (Parity with
	* linker_load_file.)
	*/
	if ((lf->flags & LINKER_FILE_MODULES) != 0 &&
	TAILQ_EMPTY(&lf->modules)) {
	linker_file_unload(lf, LINKER_UNLOAD_FORCE);
	continue;
	}

	lf->flags &= ~LINKER_FILE_MODULES;
	lf->userrefs++; /* so we can (try to) kldunload it */
	}
	sx_xunlock(&kld_sx);
	}

	/*
	* Attempt to run after all DECLARE_MODULE SYSINITs. Unfortunately they can be
	* scheduled at any subsystem and order, so run this as late as possible. init
	* becomes runnable in SI_SUB_KTHREAD_INIT, so go slightly before that.
	*/
	SYSINIT(preload_finish, SI_SUB_KTHREAD_INIT - 100, SI_ORDER_MIDDLE,
	linker_preload_finish, NULL);

	/*
	* 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_hintfile[] = "linker.hints";
	static char linker_path[MAXPATHLEN] = "/boot/kernel;/boot/modules";

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

	TUNABLE_STR("module_path", linker_path, sizeof(linker_path));

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

	/*
	* Check if file actually exists either with or without extension listed in
	* the linker_ext_list. (probably should be generic for the rest of the
	* kernel)
	*/
	static char *
	linker_lookup_file(const char path, int pathlen, const char name,
	int namelen, struct vattr *vap)
	{
	struct nameidata nd;
	struct thread td = curthread; / XXX */
	const char * const cpp, sep;
	char *result;
	int error, len, extlen, reclen, flags;
	enum vtype type;

	extlen = 0;
	for (cpp = linker_ext_list; *cpp; cpp++) {
	len = strlen(*cpp);
	if (len > extlen)
	extlen = len;
	}
	extlen++; /* trailing '\0' */
	sep = (path[pathlen - 1] != '/') ? "/" : "";

	reclen = pathlen + strlen(sep) + namelen + extlen + 1;
	result = malloc(reclen, M_LINKER, M_WAITOK);
	for (cpp = linker_ext_list; *cpp; cpp++) {
	snprintf(result, reclen, "%.s%s%.s%s", pathlen, path, sep,
	namelen, name, *cpp);
	/*
	* Attempt to open the file, and return the path if
	* we succeed and it's a regular file.
	*/
	NDINIT(&nd, LOOKUP, FOLLOW, UIO_SYSSPACE, result);
	flags = FREAD;
	error = vn_open(&nd, &flags, 0, NULL);
	if (error == 0) {
	NDFREE(&nd, NDF_ONLY_PNBUF);
	type = nd.ni_vp->v_type;
	if (vap)
	VOP_GETATTR(nd.ni_vp, vap, td->td_ucred);
	VOP_UNLOCK(nd.ni_vp);
	vn_close(nd.ni_vp, FREAD, td->td_ucred, td);
	if (type == VREG)
	return (result);
	}
	}
	free(result, M_LINKER);
	return (NULL);
	}

	#define INT_ALIGN(base, ptr) ptr = \
	(base) + roundup2((ptr) - (base), sizeof(int))

	/*
	* Lookup KLD which contains requested module in the "linker.hints" file. If
	* version specification is available, then try to find the best KLD.
	* Otherwise just find the latest one.
	*/
	static char *
	linker_hints_lookup(const char path, int pathlen, const char modname,
	int modnamelen, const struct mod_depend *verinfo)
	{
	struct thread td = curthread; / XXX */
	struct ucred *cred = td ? td->td_ucred : NULL;
	struct nameidata nd;
	struct vattr vattr, mattr;
	const char best, sep;
	u_char *hints = NULL;
	u_char cp, recptr, bufend, result, *pathbuf;
	int error, ival, bestver, *intp, found, flags, clen, blen;
	ssize_t reclen;

	result = NULL;
	bestver = found = 0;

	sep = (path[pathlen - 1] != '/') ? "/" : "";
	reclen = imax(modnamelen, strlen(linker_hintfile)) + pathlen +
	strlen(sep) + 1;
	pathbuf = malloc(reclen, M_LINKER, M_WAITOK);
	snprintf(pathbuf, reclen, "%.*s%s%s", pathlen, path, sep,
	linker_hintfile);

	NDINIT(&nd, LOOKUP, NOFOLLOW, UIO_SYSSPACE, pathbuf);
	flags = FREAD;
	error = vn_open(&nd, &flags, 0, NULL);
	if (error)
	goto bad;
	NDFREE(&nd, NDF_ONLY_PNBUF);
	if (nd.ni_vp->v_type != VREG)
	goto bad;
	best = cp = NULL;
	error = VOP_GETATTR(nd.ni_vp, &vattr, cred);
	if (error)
	goto bad;
	/*
	* XXX: we need to limit this number to some reasonable value
	*/
	if (vattr.va_size > LINKER_HINTS_MAX) {
	printf("linker.hints file too large %ld\n", (long)vattr.va_size);
	goto bad;
	}
	hints = malloc(vattr.va_size, M_TEMP, M_WAITOK);
	error = vn_rdwr(UIO_READ, nd.ni_vp, (caddr_t)hints, vattr.va_size, 0,
	UIO_SYSSPACE, IO_NODELOCKED, cred, NOCRED, &reclen, td);
	if (error)
	goto bad;
	VOP_UNLOCK(nd.ni_vp);
	vn_close(nd.ni_vp, FREAD, cred, td);
	nd.ni_vp = NULL;
	if (reclen != 0) {
	printf("can't read %zd\n", reclen);
	goto bad;
	}
	intp = (int *)hints;
	ival = *intp++;
	if (ival != LINKER_HINTS_VERSION) {
	printf("linker.hints file version mismatch %d\n", ival);
	goto bad;
	}
	bufend = hints + vattr.va_size;
	recptr = (u_char *)intp;
	clen = blen = 0;
	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(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 = linker_lookup_file(path, pathlen, cp, clen, &mattr);
	else if (best)
	result = linker_lookup_file(path, pathlen, best, blen, &mattr);

	/*
	* KLD is newer than hints file. What we should do now?
	*/
	if (result && timespeccmp(&mattr.va_mtime, &vattr.va_mtime, >))
	printf("warning: KLD '%s' is newer than the linker.hints"
	" file\n", result);
	bad:
	free(pathbuf, M_LINKER);
	if (hints)
	free(hints, M_TEMP);
	if (nd.ni_vp != NULL) {
	VOP_UNLOCK(nd.ni_vp);
	vn_close(nd.ni_vp, FREAD, cred, td);
	}
	/*
	* 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 = linker_lookup_file(path, pathlen, modname,
	modnamelen, NULL);
	return (result);
	}

	/*
	* Lookup KLD which contains requested module in the all directories.
	*/
	static char *
	linker_search_module(const char *modname, int modnamelen,
	const struct mod_depend *verinfo)
	{
	char cp, ep, *result;

	/*
	* traverse the linker path
	*/
	for (cp = linker_path; *cp; cp = ep + 1) {
	/* find the end of this component */
	for (ep = cp; (ep != 0) && (ep != ';'); ep++);
	result = linker_hints_lookup(cp, ep - cp, modname,
	modnamelen, verinfo);
	if (result != NULL)
	return (result);
	if (*ep == 0)
	break;
	}
	return (NULL);
	}

	/*
	* Search for module in all directories listed in the linker_path.
	*/
	static char *
	linker_search_kld(const char *name)
	{
	char cp, ep, *result;
	int len;

	/* qualified at all? */
	if (strchr(name, '/'))
	return (strdup(name, M_LINKER));

	/* traverse the linker path */
	len = strlen(name);
	for (ep = linker_path; *ep; ep++) {
	cp = ep;
	/* find the end of this component */
	for (; ep != 0 && ep != ';'; ep++);
	result = linker_lookup_file(cp, ep - cp, name, len, NULL);
	if (result != NULL)
	return (result);
	}
	return (NULL);
	}

	static const char *
	linker_basename(const char *path)
	{
	const char *filename;

	filename = strrchr(path, '/');
	if (filename == NULL)
	return path;
	if (filename[1])
	filename++;
	return (filename);
	}

	#ifdef HWPMC_HOOKS
	/*
	* Inform hwpmc about the set of kernel modules currently loaded.
	*/
	void *
	linker_hwpmc_list_objects(void)
	{
	linker_file_t lf;
	struct pmckern_map_in *kobase;
	int i, nmappings;

	nmappings = 0;
	sx_slock(&kld_sx);
	TAILQ_FOREACH(lf, &linker_files, link)
	nmappings++;

	/* Allocate nmappings + 1 entries. */
	kobase = malloc((nmappings + 1) * sizeof(struct pmckern_map_in),
	M_LINKER, M_WAITOK \| M_ZERO);
	i = 0;
	TAILQ_FOREACH(lf, &linker_files, link) {
	/* Save the info for this linker file. */
	kobase[i].pm_file = lf->filename;
	kobase[i].pm_address = (uintptr_t)lf->address;
	i++;
	}
	sx_sunlock(&kld_sx);

	KASSERT(i > 0, ("linker_hpwmc_list_objects: no kernel objects?"));

	/* The last entry of the malloced area comprises of all zeros. */
	KASSERT(kobase[i].pm_file == NULL,
	("linker_hwpmc_list_objects: last object not NULL"));

	return ((void *)kobase);
	}
	#endif

	/* check if root file system is not mounted */
	static bool
	linker_root_mounted(void)
	{
	struct pwd *pwd;
	bool ret;

	if (rootvnode == NULL)
	return (false);

	pwd = pwd_hold(curthread);
	ret = pwd->pwd_rdir != NULL;
	pwd_drop(pwd);
	return (ret);
	}

	/*
	* Find a file which contains given module and load it, if "parent" is not
	* NULL, register a reference to it.
	*/
	static int
	linker_load_module(const char kldname, const char modname,
	struct linker_file parent, const struct mod_depend verinfo,
	struct linker_file **lfpp)
	{
	linker_file_t lfdep;
	const char *filename;
	char *pathname;
	int error;

	sx_assert(&kld_sx, SA_XLOCKED);
	if (modname == NULL) {
	/*
	* We have to load KLD
	*/
	KASSERT(verinfo == NULL, ("linker_load_module: verinfo"
	" is not NULL"));
	if (!linker_root_mounted())
	return (ENXIO);
	pathname = linker_search_kld(kldname);
	} else {
	if (modlist_lookup2(modname, verinfo) != NULL)
	return (EEXIST);
	if (!linker_root_mounted())
	return (ENXIO);
	if (kldname != NULL)
	pathname = strdup(kldname, M_LINKER);
	else
	/*
	* Need to find a KLD with required module
	*/
	pathname = linker_search_module(modname,
	strlen(modname), verinfo);
	}
	if (pathname == NULL)
	return (ENOENT);

	/*
	* Can't load more than one file with the same basename XXX:
	* Actually it should be possible to have multiple KLDs with
	* the same basename but different path because they can
	* provide different versions of the same modules.
	*/
	filename = linker_basename(pathname);
	if (linker_find_file_by_name(filename))
	error = EEXIST;
	else do {
	error = linker_load_file(pathname, &lfdep);
	if (error)
	break;
	if (modname && verinfo &&
	modlist_lookup2(modname, verinfo) == NULL) {
	linker_file_unload(lfdep, LINKER_UNLOAD_FORCE);
	error = ENOENT;
	break;
	}
	if (parent) {
	error = linker_file_add_dependency(parent, lfdep);
	if (error)
	break;
	}
	if (lfpp)
	*lfpp = lfdep;
	} while (0);
	free(pathname, M_LINKER);
	return (error);
	}

	/*
	* This routine is responsible for finding dependencies of userland initiated
	* kldload(2)'s of files.
	*/
	int
	linker_load_dependencies(linker_file_t lf)
	{
	linker_file_t lfdep;
	struct mod_metadata start, stop, mdp, nmdp;
	struct mod_metadata mp, nmp;
	const struct mod_depend *verinfo;
	modlist_t mod;
	const char modname, nmodname;
	int ver, error = 0;

	/*
	* All files are dependent on /kernel.
	*/
	sx_assert(&kld_sx, SA_XLOCKED);
	if (linker_kernel_file) {
	linker_kernel_file->refs++;
	error = linker_file_add_dependency(lf, linker_kernel_file);
	if (error)
	return (error);
	}
	if (linker_file_lookup_set(lf, MDT_SETNAME, &start, &stop,
	NULL) != 0)
	return (0);
	for (mdp = start; mdp < stop; mdp++) {
	mp = *mdp;
	if (mp->md_type != MDT_VERSION)
	continue;
	modname = mp->md_cval;
	ver = ((const struct mod_version *)mp->md_data)->mv_version;
	mod = modlist_lookup(modname, ver);
	if (mod != NULL) {
	printf("interface %s.%d already present in the KLD"
	" '%s'!\n", modname, ver,
	mod->container->filename);
	return (EEXIST);
	}
	}

	for (mdp = start; mdp < stop; mdp++) {
	mp = *mdp;
	if (mp->md_type != MDT_DEPEND)
	continue;
	modname = mp->md_cval;
	verinfo = mp->md_data;
	nmodname = NULL;
	for (nmdp = start; nmdp < stop; nmdp++) {
	nmp = *nmdp;
	if (nmp->md_type != MDT_VERSION)
	continue;
	nmodname = nmp->md_cval;
	if (strcmp(modname, nmodname) == 0)
	break;
	}
	if (nmdp < stop)/* early exit, it's a self reference */
	continue;
	mod = modlist_lookup2(modname, verinfo);
	if (mod) { /* woohoo, it's loaded already */
	lfdep = mod->container;
	lfdep->refs++;
	error = linker_file_add_dependency(lf, lfdep);
	if (error)
	break;
	continue;
	}
	error = linker_load_module(NULL, modname, lf, verinfo, NULL);
	if (error) {
	printf("KLD %s: depends on %s - not available or"
	" version mismatch\n", lf->filename, modname);
	break;
	}
	}

	if (error)
	return (error);
	linker_addmodules(lf, start, stop, 0);
	return (error);
	}

	static int
	sysctl_kern_function_list_iterate(const char name, void opaque)
	{
	struct sysctl_req *req;

	req = opaque;
	return (SYSCTL_OUT(req, name, strlen(name) + 1));
	}

	/*
	* Export a nul-separated, double-nul-terminated list of all function names
	* in the kernel.
	*/
	static int
	sysctl_kern_function_list(SYSCTL_HANDLER_ARGS)
	{
	linker_file_t lf;
	int error;

	#ifdef MAC
	error = mac_kld_check_stat(req->td->td_ucred);
	if (error)
	return (error);
	#endif
	error = sysctl_wire_old_buffer(req, 0);
	if (error != 0)
	return (error);
	sx_xlock(&kld_sx);
	TAILQ_FOREACH(lf, &linker_files, link) {
	error = LINKER_EACH_FUNCTION_NAME(lf,
	sysctl_kern_function_list_iterate, req);
	if (error) {
	sx_xunlock(&kld_sx);
	return (error);
	}
	}
	sx_xunlock(&kld_sx);
	return (SYSCTL_OUT(req, "", 1));
	}

	SYSCTL_PROC(_kern, OID_AUTO, function_list,
	CTLTYPE_OPAQUE \| CTLFLAG_RD \| CTLFLAG_MPSAFE, NULL, 0,
	sysctl_kern_function_list, "",
	"kernel function list");

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