d118ae3895
kernels. The error message was "elf_loadexec: cannot seek". Libstand maintains a read-ahead buffer for each open file, so that it can read in chunks of 512 bytes for greater efficiency. When the loader tries to lseek forward in a file by a small amount, it sometimes happens that the target file offset is already in the read-ahead buffer. But the lseek code simply discarded the contents of that buffer and performed a seek directly on the underlying file. This resulted in an attempt to seek backwards in the file, since some of the data has already been read into the read-ahead buffer. Gzipped data streams cannot seek backwards, so an error was returned. This commit adds code which checks to see if the desired file offset is already in the read-ahead buffer. If it is, the code simply adjusts the buffer pointer and length, thereby avoiding a reverse seek on the gzipped data stream. I incorporated a suggestion from Matt Dillon which saved a little bit of code in this fix. Reviewed by: dillon, gallatin, jhb
145 lines
4.8 KiB
C
145 lines
4.8 KiB
C
/* $FreeBSD$ */
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/* $NetBSD: lseek.c,v 1.4 1997/01/22 00:38:10 cgd Exp $ */
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/*-
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* Copyright (c) 1993
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* The Regents of the University of California. All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* The Mach Operating System project at Carnegie-Mellon University.
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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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* 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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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS 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 REGENTS 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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* @(#)lseek.c 8.1 (Berkeley) 6/11/93
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*
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*
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* Copyright (c) 1989, 1990, 1991 Carnegie Mellon University
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* All Rights Reserved.
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*
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* Author: Alessandro Forin
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*
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* Permission to use, copy, modify and distribute this software and its
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* documentation is hereby granted, provided that both the copyright
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* notice and this permission notice appear in all copies of the
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* software, derivative works or modified versions, and any portions
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* thereof, and that both notices appear in supporting documentation.
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*
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* CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
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* CONDITION. CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
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* ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
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*
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* Carnegie Mellon requests users of this software to return to
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*
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* Software Distribution Coordinator or Software.Distribution@CS.CMU.EDU
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* School of Computer Science
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* Carnegie Mellon University
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* Pittsburgh PA 15213-3890
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*
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* any improvements or extensions that they make and grant Carnegie the
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* rights to redistribute these changes.
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*/
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#include "stand.h"
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off_t
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lseek(int fd, off_t offset, int where)
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{
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off_t bufpos, filepos, target;
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struct open_file *f = &files[fd];
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if ((unsigned)fd >= SOPEN_MAX || f->f_flags == 0) {
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errno = EBADF;
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return (-1);
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}
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if (f->f_flags & F_RAW) {
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/*
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* On RAW devices, update internal offset.
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*/
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switch (where) {
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case SEEK_SET:
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f->f_offset = offset;
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break;
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case SEEK_CUR:
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f->f_offset += offset;
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break;
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case SEEK_END:
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default:
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errno = EOFFSET;
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return (-1);
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}
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return (f->f_offset);
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}
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/*
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* If there is some unconsumed data in the readahead buffer and it
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* contains the desired offset, simply adjust the buffer offset and
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* length. We don't bother with SEEK_END here, since the code to
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* handle it would fail in the same cases where the non-readahead
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* code fails (namely, for streams which cannot seek backward and whose
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* size isn't known in advance).
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*/
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if (f->f_ralen != 0 && where != SEEK_END) {
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if ((filepos = (f->f_ops->fo_seek)(f, (off_t)0, SEEK_CUR)) == -1)
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return (-1);
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bufpos = filepos - f->f_ralen;
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switch (where) {
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case SEEK_SET:
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target = offset;
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break;
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case SEEK_CUR:
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target = bufpos + offset;
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break;
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default:
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errno = EINVAL;
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return (-1);
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}
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if (bufpos <= target && target < filepos) {
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f->f_raoffset += target - bufpos;
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f->f_ralen -= target - bufpos;
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return (target);
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}
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}
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/*
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* If this is a relative seek, we need to correct the offset for
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* bytes that we have already read but the caller doesn't know
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* about.
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*/
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if (where == SEEK_CUR)
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offset -= f->f_ralen;
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/*
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* Invalidate the readahead buffer.
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*/
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f->f_ralen = 0;
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return (f->f_ops->fo_seek)(f, offset, where);
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}
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