mirror of
https://github.com/freebsd/freebsd-src
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146 lines
3.7 KiB
C
146 lines
3.7 KiB
C
/*-
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* SPDX-License-Identifier: BSD-2-Clause
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*
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* Copyright (c) 2007-2009 Dag-Erling Smørgrav
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer
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* in this position and unchanged.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <sys/cdefs.h>
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#include <sys/file.h>
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#include <sys/stat.h>
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#include <errno.h>
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#include <stdarg.h>
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#include <unistd.h>
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#include <libutil.h>
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/*
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* Reliably open and lock a file.
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*
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* Please do not modify this code without first reading the revision history
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* and discussing your changes with <des@freebsd.org>. Don't be fooled by the
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* code's apparent simplicity; there would be no need for this function if it
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* was easy to get right.
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*/
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static int
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vflopenat(int dirfd, const char *path, int flags, va_list ap)
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{
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int fd, operation, serrno, trunc;
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struct stat sb, fsb;
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mode_t mode;
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#ifdef O_EXLOCK
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flags &= ~O_EXLOCK;
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#endif
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mode = 0;
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if (flags & O_CREAT) {
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mode = (mode_t)va_arg(ap, int); /* mode_t promoted to int */
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}
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operation = LOCK_EX;
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if (flags & O_NONBLOCK)
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operation |= LOCK_NB;
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trunc = (flags & O_TRUNC);
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flags &= ~O_TRUNC;
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for (;;) {
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if ((fd = openat(dirfd, path, flags, mode)) == -1)
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/* non-existent or no access */
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return (-1);
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if (flock(fd, operation) == -1) {
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/* unsupported or interrupted */
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serrno = errno;
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(void)close(fd);
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errno = serrno;
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return (-1);
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}
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if (fstatat(dirfd, path, &sb, 0) == -1) {
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/* disappeared from under our feet */
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(void)close(fd);
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continue;
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}
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if (fstat(fd, &fsb) == -1) {
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/* can't happen [tm] */
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serrno = errno;
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(void)close(fd);
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errno = serrno;
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return (-1);
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}
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if (sb.st_dev != fsb.st_dev ||
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sb.st_ino != fsb.st_ino) {
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/* changed under our feet */
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(void)close(fd);
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continue;
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}
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if (trunc && ftruncate(fd, 0) != 0) {
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/* can't happen [tm] */
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serrno = errno;
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(void)close(fd);
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errno = serrno;
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return (-1);
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}
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/*
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* The following change is provided as a specific example to
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* avoid.
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*/
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#if 0
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if (fcntl(fd, F_SETFD, FD_CLOEXEC) != 0) {
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serrno = errno;
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(void)close(fd);
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errno = serrno;
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return (-1);
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}
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#endif
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return (fd);
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}
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}
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int
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flopen(const char *path, int flags, ...)
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{
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va_list ap;
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int ret;
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va_start(ap, flags);
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ret = vflopenat(AT_FDCWD, path, flags, ap);
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va_end(ap);
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return (ret);
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}
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int
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flopenat(int dirfd, const char *path, int flags, ...)
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{
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va_list ap;
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int ret;
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va_start(ap, flags);
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ret = vflopenat(dirfd, path, flags, ap);
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va_end(ap);
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return (ret);
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}
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