1 /* $NetBSD: panic_string.c,v 1.1 2018/05/29 16:53:56 kamil Exp $ */ 2 3 /*- 4 * Copyright (c) 2018 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 16 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 17 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 18 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 19 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 20 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 21 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 22 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 23 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 24 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 25 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 26 * POSSIBILITY OF SUCH DAMAGE. 27 */ 28 29 30 #include <sys/cdefs.h> 31 __KERNEL_RCSID(0, "$NetBSD: panic_string.c,v 1.1 2018/05/29 16:53:56 kamil Exp $"); 32 33 #include <sys/param.h> 34 #include <sys/types.h> 35 #include <sys/conf.h> 36 #include <sys/device.h> 37 #include <sys/filedesc.h> 38 #include <sys/kernel.h> 39 #include <sys/kmem.h> 40 #include <sys/lwp.h> 41 #include <sys/module.h> 42 #include <sys/vfs_syscalls.h> 43 44 /* 45 * Create a device /dev/panic from which you can read sequential 46 * user input. 47 * 48 * To use this device you need to do: 49 * mknod /dev/panic c 210 0 50 * 51 * To write to the device you might need: 52 * chmod 666 /dev/panic 53 * 54 * Commentary: 55 * This module manages the device /dev/panic, 56 * tranfers a string from userspace to kernel space 57 * and calls kernel panic with the passed string. 58 * 59 * echo 'string' > /dev/panic 60 * will do the trick after loading the module. 61 */ 62 63 dev_type_open(panic_string_open); 64 dev_type_close(panic_string_close); 65 dev_type_write(panic_string_write); 66 67 static struct cdevsw panic_string_cdevsw = { 68 .d_open = panic_string_open, 69 .d_close = panic_string_close, 70 .d_read = noread, 71 .d_write = panic_string_write, 72 .d_ioctl = noioctl, 73 .d_stop = nostop, 74 .d_tty = notty, 75 .d_poll = nopoll, 76 .d_mmap = nommap, 77 .d_kqfilter = nokqfilter, 78 .d_discard = nodiscard, 79 .d_flag = D_OTHER 80 }; 81 82 static struct panic_string_softc { 83 int refcnt; 84 } sc; 85 86 /* 87 * A function similar to strnlen + isprint 88 * 89 * Detect length of the printable and non-whitespace string in the buffer. 90 * A string is accepted if it contains any non-space character. 91 */ 92 93 static size_t 94 printable_length(const char *str, size_t len) 95 { 96 size_t n; 97 bool accepted; 98 99 n = 0; 100 accepted = false; 101 102 while (len > n) { 103 if (str[n] >= 0x20 && str[n] <= 0x7e) { 104 if (str[n] != 0x20 /* space */) 105 accepted = true; 106 n++; 107 } else 108 break; 109 } 110 111 if (accepted) 112 return n; 113 else 114 return 0; 115 } 116 117 int 118 panic_string_open(dev_t self __unused, int flag __unused, int mod __unused, struct lwp *l) 119 { 120 121 /* Make sure the device is opened once at a time */ 122 if (sc.refcnt > 0) 123 return EBUSY; 124 125 ++sc.refcnt; 126 127 return 0; 128 } 129 130 int 131 panic_string_close(dev_t self __unused, int flag __unused, int mod __unused, struct lwp *l __unused) 132 { 133 134 --sc.refcnt; 135 return 0; 136 } 137 138 int 139 panic_string_write(dev_t self, struct uio *uio, int flags) 140 { 141 size_t len, printlen; 142 char *buffer; 143 144 /* Buffer length */ 145 len = uio->uio_iov->iov_len; 146 147 /* Allocate a local buffer to store the string */ 148 buffer = (char *)kmem_alloc(len, KM_SLEEP); 149 150 /* Move the string from user to kernel space and store it locally */ 151 uiomove(buffer, len, uio); 152 153 printlen = printable_length(buffer, len); 154 155 if (printlen > 0) { 156 /* Flushing disk changes */ 157 do_sys_sync(curlwp); 158 159 panic("panic string: %.*s\n", (int)printlen, buffer); 160 // printf("panic string: %.*s\n", (int)printlen, buffer); 161 162 /* NOTREACHED */ 163 } 164 165 kmem_free(buffer, len); 166 return 0; 167 } 168 169 MODULE(MODULE_CLASS_MISC, panic_string, NULL); 170 171 static int 172 panic_string_modcmd(modcmd_t cmd, void *arg __unused) 173 { 174 /* The major should be verified and changed if needed to avoid 175 * conflicts with other devices. */ 176 int cmajor = 210, bmajor = -1; 177 178 switch (cmd) { 179 case MODULE_CMD_INIT: 180 printf("Panic String module loaded.\n"); 181 if (devsw_attach("panic", NULL, &bmajor, &panic_string_cdevsw, 182 &cmajor)) 183 return ENXIO; 184 return 0; 185 186 case MODULE_CMD_FINI: 187 printf("Panic String module unloaded.\n"); 188 if (sc.refcnt > 0) 189 return EBUSY; 190 191 devsw_detach(NULL, &panic_string_cdevsw); 192 return 0; 193 default: 194 return ENOTTY; 195 } 196 } 197