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freebsd/usr.bin/cmp/regular.c
David Schultz d48905120d The cmp utility has the questionable feature of using mmap when
comparing regular files.  Add a SIGSEGV handler to make its
behavior less surprising when a read error occurs.  The handler
does not attempt to distinguish errors from file truncation, but
anyone actively modifying a file while trying to compare it
shouldn't even expect something sane to happen.

PR:		45391
Reviewed by:	mike (mentor)
2003-02-26 06:44:46 +00:00

179 lines
4.8 KiB
C

/*-
* Copyright (c) 1991, 1993, 1994
* The Regents of the University of California. 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 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.
*/
#if 0
#ifndef lint
static char sccsid[] = "@(#)regular.c 8.3 (Berkeley) 4/2/94";
#endif
#endif
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <err.h>
#include <errno.h>
#include <limits.h>
#include <signal.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include "extern.h"
static u_char *remmap(u_char *, int, off_t);
static void segv_handler(int);
#define MMAP_CHUNK (8*1024*1024)
#define ROUNDPAGE(i) ((i) & ~pagemask)
void
c_regular(int fd1, const char *file1, off_t skip1, off_t len1,
int fd2, const char *file2, off_t skip2, off_t len2)
{
u_char ch, *p1, *p2, *m1, *m2, *e1, *e2;
off_t byte, length, line;
int dfound;
off_t pagemask, off1, off2;
size_t pagesize;
struct sigaction act, oact;
if (skip1 > len1)
eofmsg(file1);
len1 -= skip1;
if (skip2 > len2)
eofmsg(file2);
len2 -= skip2;
if (sflag && len1 != len2)
exit(DIFF_EXIT);
sigemptyset(&act.sa_mask);
act.sa_flags = SA_NODEFER;
act.sa_handler = segv_handler;
if (sigaction(SIGSEGV, &act, &oact))
err(ERR_EXIT, "sigaction()");
pagesize = getpagesize();
pagemask = (off_t)pagesize - 1;
off1 = ROUNDPAGE(skip1);
off2 = ROUNDPAGE(skip2);
length = MIN(len1, len2);
if ((m1 = remmap(NULL, fd1, off1)) == NULL) {
c_special(fd1, file1, skip1, fd2, file2, skip2);
return;
}
if ((m2 = remmap(NULL, fd2, off2)) == NULL) {
munmap(m1, MMAP_CHUNK);
c_special(fd1, file1, skip1, fd2, file2, skip2);
return;
}
dfound = 0;
e1 = m1 + MMAP_CHUNK;
e2 = m2 + MMAP_CHUNK;
p1 = m1 + (skip1 - off1);
p2 = m2 + (skip2 - off2);
for (byte = line = 1; length--; ++byte) {
if ((ch = *p1) != *p2) {
if (xflag) {
dfound = 1;
(void)printf("%08llx %02x %02x\n",
(long long)byte - 1, ch, *p2);
} else if (lflag) {
dfound = 1;
(void)printf("%6lld %3o %3o\n",
(long long)byte, ch, *p2);
} else
diffmsg(file1, file2, byte, line);
/* NOTREACHED */
}
if (ch == '\n')
++line;
if (++p1 == e1) {
off1 += MMAP_CHUNK;
if ((p1 = m1 = remmap(m1, fd1, off1)) == NULL) {
munmap(m2, MMAP_CHUNK);
err(ERR_EXIT, "remmap %s", file1);
}
e1 = m1 + MMAP_CHUNK;
}
if (++p2 == e2) {
off2 += MMAP_CHUNK;
if ((p2 = m2 = remmap(m2, fd2, off2)) == NULL) {
munmap(m1, MMAP_CHUNK);
err(ERR_EXIT, "remmap %s", file2);
}
e2 = m2 + MMAP_CHUNK;
}
}
munmap(m1, MMAP_CHUNK);
munmap(m2, MMAP_CHUNK);
if (sigaction(SIGSEGV, &oact, NULL))
err(ERR_EXIT, "sigaction()");
if (len1 != len2)
eofmsg (len1 > len2 ? file2 : file1);
if (dfound)
exit(DIFF_EXIT);
}
static u_char *
remmap(u_char *mem, int fd, off_t offset)
{
if (mem != NULL)
munmap(mem, MMAP_CHUNK);
mem = mmap(NULL, MMAP_CHUNK, PROT_READ, MAP_SHARED, fd, offset);
if (mem == MAP_FAILED)
return (NULL);
madvise(mem, MMAP_CHUNK, MADV_SEQUENTIAL);
return (mem);
}
static void
segv_handler(int sig) {
static const char msg[] = "cmp: Input/output error (caught SIGSEGV)\n";
write(STDERR_FILENO, msg, sizeof(msg));
_exit(EXIT_FAILURE);
}