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/*-
* SPDX-License-Identifier: BSD-2-Clause
*
* Copyright (c) 2023 Klara, Inc.
*
* 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>
#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <unistd.h>
static int
exec_shortargs(char *argv[])
{
char *flag_arg = argv[2];
char *sentinel = argv[3];
char * nargv[] = { argv[0], __DECONST(char *, "--spin"), flag_arg,
sentinel, NULL };
char * const nenvp[] = { NULL };
execve(argv[0], nargv, nenvp);
err(1, "execve");
}
static int
exec_largeargs(char *argv[])
{
char *flag_arg = argv[2];
char *sentinel = argv[3];
/*
* Account for each argument and their NUL terminator, as well as an
* extra NUL terminator.
*/
size_t bufsz = ARG_MAX -
((strlen(argv[0]) + 1) + sizeof("--spin") + (strlen(flag_arg) + 1) +
(strlen(sentinel) + 1) + 1);
char *s = NULL;
char * nargv[] = { argv[0], __DECONST(char *, "--spin"), flag_arg, NULL,
sentinel, NULL };
char * const nenvp[] = { NULL };
/*
* Our heuristic may or may not be accurate, we'll keep trying with
* smaller argument sizes as needed until we stop getting E2BIG.
*/
do {
if (s == NULL)
s = malloc(bufsz + 1);
else
s = realloc(s, bufsz + 1);
if (s == NULL)
abort();
memset(s, 'x', bufsz);
s[bufsz] = '\0';
nargv[3] = s;
execve(argv[0], nargv, nenvp);
bufsz--;
} while (errno == E2BIG);
err(1, "execve");
}
int
main(int argc, char *argv[])
{
if (argc > 1 && strcmp(argv[1], "--spin") == 0) {
int fd;
if (argc < 4) {
fprintf(stderr, "usage: %s --spin flagfile ...\n", argv[0]);
return (1);
}
fd = open(argv[2], O_RDWR | O_CREAT, 0755);
if (fd < 0)
err(1, "%s", argv[2]);
close(fd);
for (;;) {
sleep(1);
}
return (1);
}
if (argc != 4) {
fprintf(stderr, "usage: %s [--short | --long] flagfile sentinel\n",
argv[0]);
return (1);
}
if (strcmp(argv[1], "--short") == 0)
exec_shortargs(argv);
else
exec_largeargs(argv);
}
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