1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2023 Klara, Inc. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 16 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 19 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 20 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 21 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 22 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 23 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 24 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 25 * SUCH DAMAGE. 26 */ 27 #include <sys/cdefs.h> 28 29 #include <err.h> 30 #include <errno.h> 31 #include <fcntl.h> 32 #include <limits.h> 33 #include <stdlib.h> 34 #include <string.h> 35 #include <stdio.h> 36 #include <unistd.h> 37 38 static int 39 exec_shortargs(char *argv[]) 40 { 41 char *flag_arg = argv[2]; 42 char *sentinel = argv[3]; 43 char * nargv[] = { argv[0], __DECONST(char *, "--spin"), flag_arg, 44 sentinel, NULL }; 45 char * const nenvp[] = { NULL }; 46 47 execve(argv[0], nargv, nenvp); 48 err(1, "execve"); 49 } 50 51 static int 52 exec_largeargs(char *argv[]) 53 { 54 char *flag_arg = argv[2]; 55 char *sentinel = argv[3]; 56 /* 57 * Account for each argument and their NUL terminator, as well as an 58 * extra NUL terminator. 59 */ 60 size_t bufsz = ARG_MAX - 61 ((strlen(argv[0]) + 1) + sizeof("--spin") + (strlen(flag_arg) + 1) + 62 (strlen(sentinel) + 1) + 1); 63 char *s = NULL; 64 char * nargv[] = { argv[0], __DECONST(char *, "--spin"), flag_arg, NULL, 65 sentinel, NULL }; 66 char * const nenvp[] = { NULL }; 67 68 /* 69 * Our heuristic may or may not be accurate, we'll keep trying with 70 * smaller argument sizes as needed until we stop getting E2BIG. 71 */ 72 do { 73 if (s == NULL) 74 s = malloc(bufsz + 1); 75 else 76 s = realloc(s, bufsz + 1); 77 if (s == NULL) 78 abort(); 79 memset(s, 'x', bufsz); 80 s[bufsz] = '\0'; 81 nargv[3] = s; 82 83 execve(argv[0], nargv, nenvp); 84 bufsz--; 85 } while (errno == E2BIG); 86 err(1, "execve"); 87 } 88 89 int 90 main(int argc, char *argv[]) 91 { 92 93 if (argc > 1 && strcmp(argv[1], "--spin") == 0) { 94 int fd; 95 96 if (argc < 4) { 97 fprintf(stderr, "usage: %s --spin flagfile ...\n", argv[0]); 98 return (1); 99 } 100 101 fd = open(argv[2], O_RDWR | O_CREAT, 0755); 102 if (fd < 0) 103 err(1, "%s", argv[2]); 104 close(fd); 105 106 for (;;) { 107 sleep(1); 108 } 109 110 return (1); 111 } 112 113 if (argc != 4) { 114 fprintf(stderr, "usage: %s [--short | --long] flagfile sentinel\n", 115 argv[0]); 116 return (1); 117 } 118 119 if (strcmp(argv[1], "--short") == 0) 120 exec_shortargs(argv); 121 else 122 exec_largeargs(argv); 123 } 124