NetBSD/distrib/utils/sysinst/target.c

935 lines
23 KiB
C

/* $NetBSD: target.c,v 1.31 2001/01/14 02:38:15 mrg Exp $ */
/*
* Copyright 1997 Jonathan Stone
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed for the NetBSD Project by
* Jonathan Stone.
* 4. The name of Jonathan Stone may not be used to endorse
* or promote products derived from this software without specific prior
* written permission.
*
* THIS SOFTWARE IS PROVIDED BY JONATHAN STONE ``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 PIERMONT INFORMATION SYSTEMS INC. 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.
*
*/
/* Copyright below applies to the realpath() code */
/*
* Copyright (c) 1989, 1991, 1993, 1995
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Jan-Simon Pendry.
*
* 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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>
#if defined(LIBC_SCCS) && !defined(lint)
__RCSID("$NetBSD: target.c,v 1.31 2001/01/14 02:38:15 mrg Exp $");
#endif
/*
* target.c -- path-prefixing routines to access the target installation
* filesystems. Makes the install tools more independent of whether
* we're installing into a separate filesystem hierarchy mounted under /mnt,
* or into the currently active root mounted on /.
*/
#include <sys/param.h> /* XXX vm_param.h always defines TRUE*/
#include <sys/types.h>
#include <sys/sysctl.h>
#include <sys/stat.h> /* stat() */
#include <sys/mount.h> /* statfs() */
#include <fcntl.h>
#include <stdio.h>
#include <stdarg.h>
#include <unistd.h>
#include <curses.h> /* defines TRUE, but checks */
#include <errno.h>
#include "defs.h"
#include "md.h"
#include "msg_defs.h"
#include "menu_defs.h"
/*
* local prototypes
*/
static const char* get_rootdev (void);
static const char* mounted_rootpart (void);
int target_on_current_disk (void);
int must_mount_root (void);
static void make_prefixed_dir (const char *prefix, const char *path);
static int do_target_chdir (const char *dir, int flag);
int target_test(unsigned int mode, const char *path);
int target_test_dir (const char *path); /* deprecated */
int target_test_file (const char *path); /* deprecated */
int target_test_symlink (const char *path); /* deprecated */
void backtowin(void);
void unwind_mounts (void);
int mount_with_unwind (const char *fstype, const char *from, const char *on);
/* Record a mount for later unwinding of target mounts. */
struct unwind_mount {
struct unwind_mount *um_prev;
char um_mountpoint[STRSIZE];
};
/* Unwind-mount stack */
struct unwind_mount *unwind_mountlist = NULL;
/*
* Debugging options
*/
/*#define DEBUG_ROOT*/ /* turn on what-is-root? debugging. */
/*#define DEBUG_UNWIND*/ /* turn on unwind-target-mount debugging. */
/*
* debugging helper. curses...
*/
void
backtowin()
{
fflush(stdout); /* curses does not leave stdout linebuffered. */
getchar(); /* wait for user to press return */
wrefresh(stdscr);
}
/*
* Get name of current root device from kernel via sysctl.
* On NetBSD-1.3_ALPHA, this just returns the name of a
* device (e.g., "sd0"), not a specific partition -- like "sd0a",
* or "sd0b" for root-in-swap.
*/
static const char *
get_rootdev()
{
int mib[2];
static char rootdev[STRSIZE];
size_t varlen;
mib[0] = CTL_KERN;
mib[1] = KERN_ROOT_DEVICE;
varlen = sizeof(rootdev);
if (sysctl(mib, 2, rootdev, &varlen, NULL, 0) < 0)
return (NULL);
#ifdef DEBUG
printf("get_rootdev(): sysctl returns %s\n", rootdev);
#endif
return (rootdev);
}
/*
* Check if current root and target are on the same
* device (e.g., both on "sd0") or on different devices
* e.g., target is "sd0" and root is "le0" (nfs).
*/
int
target_on_current_disk()
{
int same;
if (strcmp(diskdev, "") == 0) /* nothing selected yet */
same = 1; /* bad assumption: this is a live system */
else
same = (strcmp(diskdev, get_rootdev()) == 0);
return (same);
}
/*
* must_mount_root -- check to see if the current root
* partition and the target root partition are on the same
* device. If they are, we need to have the root mounted read/write
* in order to find out whether they're the same partition.
* (this is arguably a bug in the kernel API.)
*
* check to see if they're
*/
int
must_mount_root()
{
int result;
#if defined(DEBUG) || defined(DEBUG_ROOT)
endwin();
printf("must_mount_root\n");
backtowin();
#endif
/* if they're on different devices, we're OK. */
if (target_on_current_disk() == 0) {
#if defined(DEBUG) || defined(DEBUG_ROOT)
endwin();
printf("must_mount_root: %s and %s, no?\n",
diskdev, get_rootdev());
fflush(stdout);
backtowin();
#endif
return (0);
}
/* If they're on the same device, and root not mounted, yell. */
result = (strcmp(mounted_rootpart(), "root_device") == 0);
#if defined(DEBUG) || defined(DEBUG_ROOT)
endwin();
printf("must_mount_root %s and root_device gives %d\n",
mounted_rootpart(), result);
fflush(stdout);
backtowin();
#endif
return (result);
}
/*
* Is the root partition we're running from the same as the root
* which the user has selected to install/upgrade?
* Uses global variable "diskdev" to find the selected device for
* install/upgrade.
* FIXME -- disklabel-editing code assumes that partition 'a' is always root.
*/
int
target_already_root()
{
register int result;
char diskdevroot[STRSIZE];
/* if they're on different devices, we're OK. */
if (target_on_current_disk() == 0)
return (0);
/*
* otherwise, install() or upgrade() should already did
* have forced the user to explicitly mount the root,
* so we can find out via statfs(). Abort if not.
*/
if (strcmp(diskdev, "") == 0) {
/* no root partition was ever selected. Assume that
* the currently mounted one should be used */
result = 1;
} else {
/* append 'a' to the partitionless target disk device name. */
snprintf(diskdevroot, STRSIZE, "%s%c", diskdev, 'a');
result = is_active_rootpart(diskdevroot);
}
return (result);
}
/*
* ask the kernel what the current root is.
* If it's "root_device", we should just give up now.
* (Why won't the kernel tell us? If we booted with "n",
* or an explicit bootpath, the operator told *it* ....)
*
* Don't cache the answer in case the user suspends and remounts.
*/
static const char *
mounted_rootpart()
{
struct statfs statfsbuf;
int result;
static char statrootstr[STRSIZE];
memset(&statfsbuf, 0, sizeof(statfsbuf));
result = statfs("/", &statfsbuf);
if (result < 0) {
fprintf(stderr, "Help! statfs() can't find root: %s\n",
strerror(errno));
fflush(stderr);
if (logging)
fprintf(log, "Help! statfs() can't find root: %s\n",
strerror(errno));
exit(errno);
return(0);
}
#if defined(DEBUG)
endwin();
printf("mounted_rootpart: got %s on %s\n",
statfsbuf.f_mntonname, statfsbuf.f_mntfromname);
fflush(stdout);
backtowin();
#endif
/*
* Check for unmounted root. We can't tell which partition
*/
strncpy(statrootstr, statfsbuf.f_mntfromname, STRSIZE);
return (statrootstr);
}
/*
* Is this device partition (e.g., "sd0a") mounted as root?
* Note difference from target_on_current_disk()!
*/
int
is_active_rootpart(devpart)
const char *devpart;
{
const char *root = 0;
int result;
static char devdirdevpart[STRSIZE];
/* check to see if the devices match? */
/* this changes on mounts, so don't cache it. */
root = mounted_rootpart();
/* prepend /dev. */
/* XXX post-1.3, use strstr to strip "/dev" from input. */
snprintf(devdirdevpart, STRSIZE, "/dev/%s", devpart);
result = (strcmp(devdirdevpart, root) == 0);
#if defined(DEBUG) || defined(DEBUG_ROOT)
endwin();
printf("is_active_rootpart: activeroot = %s, query=%s, mung=%s, answer=%d\n",
root, devpart, devdirdevpart, result);
fflush(stdout);
backtowin();
#endif
return (result);
}
/*
* Pathname prefixing glue to support installation either
* from in-ramdisk miniroots or on-disk diskimages.
* If our root is on the target disk, the install target is mounted
* on /mnt and we need to prefix installed pathnames with /mnt.
* otherwise we are installing to the currently-active root and
* no prefix is needed.
*/
const char *
target_prefix()
{
/*
* XXX fetch sysctl variable for current root, and compare
* to the devicename of the install target disk.
*/
return(target_already_root() ? "" : "/mnt");
}
/*
* concatenate two pathnames.
* XXX returns either input args or result in a static buffer.
* The caller must copy if it wants to use the pathname past the
* next call to a target-prefixing function, or to modify the inputs..
* Used only internally so this is probably safe.
*/
const char*
concat_paths(prefix, suffix)
const char* prefix;
const char *suffix;
{
static char realpath[MAXPATHLEN];
/* absolute prefix and null suffix? */
if (prefix[0] == '/' && suffix[0] == 0)
return prefix;
/* null prefix and absolute suffix? */
if (prefix[0] == 0 && suffix[0] == '/')
return suffix;
/* avoid "//" */
if (suffix[0] == '/' || suffix[0] == 0)
snprintf(realpath, MAXPATHLEN, "%s%s", prefix, suffix);
else
snprintf(realpath, MAXPATHLEN, "%s/%s", prefix, suffix);
return (realpath);
}
/*
* Do target prefix expansion on a pathname.
* XXX uses concat_paths and so returns result in a static buffer.
* The caller must copy if it wants to use the pathname past the
* next call to a target-prefixing function, or to modify the inputs..
* Used only internally so this is probably safe.
*
* Not static so other functions can generate target related file names.
*/
const char *
target_expand(tgtpath)
const char *tgtpath;
{
return concat_paths(target_prefix(), tgtpath);
}
/* Make a directory, with a prefix like "/mnt" or possibly just "". */
static void
make_prefixed_dir(prefix, path)
const char *prefix;
const char *path;
{
run_prog(0, NULL, "/bin/mkdir -p %s", concat_paths(prefix, path));
}
/* Make a directory with a pathname relative to the installation target. */
void
make_target_dir(path)
const char *path;
{
make_prefixed_dir(target_prefix(), path);
}
/* Make a directory with a pathname in the currently-mounted root. */
void
make_ramdisk_dir(path)
const char *path;
{
make_prefixed_dir(path, "");
}
#if 0
/* unused, will not work with new run.c */
/*
*
* Append |string| to the filename |path|, where |path| is
* relative to the root of the install target.
* for example,
* echo_to_target_file( "Newbie.NetBSD.ORG", "/etc/myname");
* would set the default hostname at the next reboot of the installed-on disk.
*/
void
append_to_target_file(path, string)
const char *path;
const char *string;
{
run_prog(RUN_FATAL, NULL, "echo %s >> %s", string, target_expand(path));
}
/*
* As append_to_target_file, but with ftrunc semantics.
*/
void
echo_to_target_file(path, string)
const char *path;
const char *string;
{
trunc_target_file(path);
append_to_target_file(path, string);
}
void
sprintf_to_target_file(const char *path, const char *format, ...)
{
char lines[STRSIZE];
va_list ap;
trunc_target_file(path);
va_start(ap, format);
vsnprintf(lines, STRSIZE, format, ap);
va_end(ap);
append_to_target_file(path, lines);
}
void
trunc_target_file(path)
const char *path;
{
run_prog(RUN_FATAL, NULL, "cat < /dev/null > %s", target_expand(path));
}
#endif /* if 0 */
static int
do_target_chdir(dir, must_succeed)
const char *dir;
int must_succeed;
{
const char *tgt_dir;
int error;
error = 0;
tgt_dir = target_expand(dir);
#ifndef DEBUG
/* chdir returns -1 on error and sets errno. */
if (chdir(tgt_dir) < 0)
error = errno;
if (logging) {
fprintf(log, "cd to %s\n", tgt_dir);
fflush(log);
}
if (scripting) {
scripting_fprintf(NULL, "cd %s\n", tgt_dir);
fflush(script);
}
if (error && must_succeed) {
fprintf(stderr, msg_string(MSG_realdir),
target_prefix(), strerror(error));
if (logging)
fprintf(log, msg_string(MSG_realdir),
target_prefix(), strerror(error));
exit(1);
}
return (error);
#else
printf("target_chdir (%s)\n", tgt_dir);
return (0);
#endif
}
void
target_chdir_or_die(dir)
const char *dir;
{
(void) do_target_chdir(dir, 1);
}
int
target_chdir(dir)
const char *dir;
{
return(do_target_chdir(dir, 0));
}
/*
* Copy a file from the current root into the target system,
* where the destination pathname is relative to the target root.
* Does not check for copy-to-self when target is current root.
*/
int
cp_to_target(srcpath, tgt_path)
const char *srcpath;
const char *tgt_path;
{
const char *realpath = target_expand(tgt_path);
return run_prog(0, NULL, "/bin/cp %s %s", srcpath, realpath);
}
/*
* Duplicate a file from the current root to the same pathname
* in the target system. Pathname must be an absolute pathname.
* If we're running in the target, do nothing.
*/
void
dup_file_into_target(filename)
const char *filename;
{
if (!target_already_root())
cp_to_target(filename, filename);
}
/*
* Do a mv where both pathnames are within the target filesystem.
*/
void
mv_within_target_or_die(frompath, topath)
const char *frompath;
const char *topath;
{
char realfrom[STRSIZE];
char realto[STRSIZE];
strncpy(realfrom, target_expand(frompath), STRSIZE);
strncpy(realto, target_expand(topath), STRSIZE);
run_prog(RUN_FATAL, NULL, "mv %s %s", realfrom, realto);
}
/* Do a cp where both pathnames are within the target filesystem. */
int cp_within_target(frompath, topath)
const char *frompath;
const char *topath;
{
char realfrom[STRSIZE];
char realto[STRSIZE];
strncpy(realfrom, target_expand(frompath), STRSIZE);
strncpy(realto, target_expand(topath), STRSIZE);
return (run_prog(0, NULL, "cp -p %s %s", realfrom, realto));
}
/* fopen a pathname in the target. */
FILE *
target_fopen(filename, type)
const char *filename;
const char *type;
{
return fopen(target_expand(filename), type);
}
/*
* Do a mount and record the mountpoint in a list of mounts to
* unwind after completing or aborting a mount.
*/
int
mount_with_unwind(fstype, from, on)
const char *fstype;
const char *from;
const char *on;
{
int error;
struct unwind_mount * m;
m = malloc(sizeof(*m));
if (m == 0)
return (ENOMEM); /* XXX */
strncpy(m->um_mountpoint, on, STRSIZE);
m->um_prev = unwind_mountlist;
unwind_mountlist = m;
#ifdef DEBUG_UNWIND
endwin();
fprintf(stderr, "mounting %s with unwind\n", on);
backtowin();
#endif
error = run_prog(0, NULL, "/sbin/mount %s %s %s", fstype, from, on);
return (error);
}
/*
* unwind the mount stack, unmounting mounted filesystems.
* For now, ignore any errors in unmount.
* (Why would we be unable to unmount? The user has suspended
* us and forked shell sitting somewhere in the target root?)
*/
void
unwind_mounts()
{
struct unwind_mount *m, *prev;
volatile static int unwind_in_progress = 0;
/* signal safety */
if (unwind_in_progress)
return;
unwind_in_progress = 1;
prev = NULL;
for (m = unwind_mountlist; m; ) {
struct unwind_mount *prev;
#ifdef DEBUG_UNWIND
endwin();
fprintf(stderr, "unmounting %s\n", m->um_mountpoint);
backtowin();
#endif
run_prog(0, NULL, "/sbin/umount %s", m->um_mountpoint);
prev = m->um_prev;
free(m);
m = prev;
}
unwind_mountlist = NULL;
unwind_in_progress = 0;
}
/*
* Do a mount onto a mountpoint in the install target.
* NB: does not prefix mount-from, which probably breaks nullfs mounts.
*/
int
target_mount(fstype, from, on)
const char *fstype;
const char *from;
const char *on;
{
int error;
const char *realmount = target_expand(on);
/* mount and record for unmounting when done. */
error = mount_with_unwind(fstype, from, realmount);
return (error);
}
int
target_collect_file(kind, buffer, name)
int kind;
char **buffer;
char *name;
{
const char *realname =target_expand(name);
#ifdef DEBUG
printf("collect real name %s\n", realname);
#endif
return collect(kind, buffer, realname);
}
/*
* Verify a pathname already exists in the target root filesystem,
* by running test "testflag" on the expanded target pathname.
*/
int
target_test(mode, path)
unsigned int mode;
const char *path;
{
const char *realpath = target_expand(path);
register int result;
result = !file_mode_match(realpath, mode);
scripting_fprintf(NULL, "if [ $? != 0 ]; then echo \"%s does not exist!\"; fi\n", realpath);
#if defined(DEBUG)
printf("target_test(%s %s) returning %d\n", test, realpath, result);
#endif
return (result);
}
/*
* Verify a directory already exists in the target root
* filesystem. Do not create the directory if it doesn't exist.
* Assumes that sysinst has already mounted the target root.
*/
int
target_test_dir(path)
const char *path;
{
return target_test(S_IFDIR, path);
}
/*
* Verify an ordinary file already exists in the target root
* filesystem. Do not create the directory if it doesn't exist.
* Assumes that sysinst has already mounted the target root.
*/
int
target_test_file(path)
const char *path;
{
return target_test(S_IFREG, path);
}
int
target_test_symlink(path)
const char *path;
{
return target_test(S_IFLNK, path);
}
int target_file_exists_p(path)
const char *path;
{
return (target_test_file(path) == 0);
}
int target_dir_exists_p(path)
const char *path;
{
return (target_test_dir(path) == 0);
}
int target_symlink_exists_p(path)
const char *path;
{
return (target_test_symlink(path) == 0);
}
/*
* XXXX had to include this to deal with symlinks in some places. When the target
* disk is mounted under /mnt, absolute symlinks on it don't work right. This
* function will resolve them using the mountpoint as prefix. Copied verbatim
* from libc, with added prefix handling.
*
* char *realpath(const char *path, char resolved_path[MAXPATHLEN]);
*
* Find the real name of path, by removing all ".", ".." and symlink
* components. Returns (resolved) on success, or (NULL) on failure,
* in which case the path which caused trouble is left in (resolved).
*/
char *
target_realpath(const char *path, char *resolved)
{
struct stat sb;
int fd, n, rootd, serrno, nlnk = 0;
char *p, *q, wbuf[MAXPATHLEN];
/* Save the starting point. */
if ((fd = open(".", O_RDONLY)) < 0) {
(void)strcpy(resolved, ".");
return (NULL);
}
/*
* Find the dirname and basename from the path to be resolved.
* Change directory to the dirname component.
* lstat the basename part.
* if it is a symlink, read in the value and loop.
* if it is a directory, then change to that directory.
* get the current directory name and append the basename.
*/
if (target_prefix() != NULL && strcmp(target_prefix(), "") != 0)
snprintf(resolved, MAXPATHLEN, "%s/%s", target_prefix(), path);
else {
(void)strncpy(resolved, path, MAXPATHLEN - 1);
resolved[MAXPATHLEN - 1] = '\0';
}
loop:
q = strrchr(resolved, '/');
if (q != NULL) {
p = q + 1;
if (q == resolved)
q = "/";
else {
do {
--q;
} while (q > resolved && *q == '/');
q[1] = '\0';
q = resolved;
}
if (chdir(q) < 0)
goto err1;
} else
p = resolved;
/* Deal with the last component. */
if (lstat(p, &sb) == 0) {
if (S_ISLNK(sb.st_mode)) {
if (nlnk++ >= MAXSYMLINKS) {
errno = ELOOP;
goto err1;
}
n = readlink(p, wbuf, MAXPATHLEN);
if (n < 0)
goto err1;
wbuf[n] = '\0';
if (wbuf[0] == '/')
snprintf(resolved, MAXPATHLEN, "%s%s", target_prefix(),
wbuf);
else
strcpy(resolved, wbuf);
goto loop;
}
if (S_ISDIR(sb.st_mode)) {
if (chdir(p) < 0)
goto err1;
p = "";
}
}
/*
* Save the last component name and get the full pathname of
* the current directory.
*/
(void)strncpy(wbuf, p, (sizeof(wbuf) - 1));
/*
* Call the internal internal version of getcwd which
* does a physical search rather than using the $PWD short-cut
*/
if (getcwd(resolved, MAXPATHLEN) == 0)
goto err1;
/*
* Join the two strings together, ensuring that the right thing
* happens if the last component is empty, or the dirname is root.
*/
if (resolved[0] == '/' && resolved[1] == '\0')
rootd = 1;
else
rootd = 0;
if (*wbuf) {
if (strlen(resolved) + strlen(wbuf) + rootd + 1 > MAXPATHLEN) {
errno = ENAMETOOLONG;
goto err1;
}
if (rootd == 0)
(void)strcat(resolved, "/"); /* XXX: strcat is safe */
(void)strcat(resolved, wbuf); /* XXX: strcat is safe */
}
/* Go back to where we came from. */
if (fchdir(fd) < 0) {
serrno = errno;
goto err2;
}
/* It's okay if the close fails, what's an fd more or less? */
(void)close(fd);
return (resolved);
err1: serrno = errno;
(void)fchdir(fd);
err2: (void)close(fd);
errno = serrno;
return (NULL);
}