1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause 3 * 4 * Copyright (c) 2000 Mark R. V. Murray & Jeroen C. van Gelderen 5 * Copyright (c) 2001-2004 Mark R. V. Murray 6 * Copyright (c) 2014 Eitan Adler 7 * Copyright (c) 2025 Pietro Cerutti 8 * All rights reserved. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer 15 * in this position and unchanged. 16 * 2. Redistributions in binary form must reproduce the above copyright 17 * notice, this list of conditions and the following disclaimer in the 18 * documentation and/or other materials provided with the distribution. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS ``AS IS'' AND ANY EXPRESS OR 21 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 22 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 23 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 24 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 25 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 26 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 27 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 28 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 29 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 30 * 31 */ 32 33 #include <sys/param.h> 34 #include <sys/systm.h> 35 #include <sys/conf.h> 36 #include <sys/uio.h> 37 #include <sys/kernel.h> 38 #include <sys/malloc.h> 39 #include <sys/module.h> 40 #include <sys/disk.h> 41 #include <sys/bus.h> 42 #include <sys/filio.h> 43 #include <sys/event.h> 44 45 #include <machine/bus.h> 46 #include <machine/vmparam.h> 47 48 /* For use with destroy_dev(9). */ 49 static struct cdev *full_dev; 50 static struct cdev *null_dev; 51 static struct cdev *zero_dev; 52 53 static d_write_t full_write; 54 static d_write_t null_write; 55 static d_ioctl_t null_ioctl; 56 static d_ioctl_t zero_ioctl; 57 static d_read_t zero_read; 58 static d_kqfilter_t kqfilter; 59 static int one_ev(struct knote *kn, long hint); 60 static int zero_ev(struct knote *kn, long hint); 61 62 static const struct filterops one_fop = { 63 .f_isfd = 1, 64 .f_event = one_ev, 65 .f_copy = knote_triv_copy, 66 }; 67 68 static const struct filterops zero_fop = { 69 .f_isfd = 1, 70 .f_event = zero_ev, 71 .f_copy = knote_triv_copy, 72 }; 73 74 static struct cdevsw full_cdevsw = { 75 .d_version = D_VERSION, 76 .d_read = zero_read, 77 .d_write = full_write, 78 .d_ioctl = zero_ioctl, 79 .d_kqfilter = kqfilter, 80 .d_name = "full", 81 }; 82 83 static struct cdevsw null_cdevsw = { 84 .d_version = D_VERSION, 85 .d_read = (d_read_t *)nullop, 86 .d_write = null_write, 87 .d_ioctl = null_ioctl, 88 .d_kqfilter = kqfilter, 89 .d_name = "null", 90 }; 91 92 static struct cdevsw zero_cdevsw = { 93 .d_version = D_VERSION, 94 .d_read = zero_read, 95 .d_write = null_write, 96 .d_ioctl = zero_ioctl, 97 .d_kqfilter = kqfilter, 98 .d_name = "zero", 99 .d_flags = D_MMAP_ANON, 100 }; 101 102 /* ARGSUSED */ 103 static int 104 full_write(struct cdev *dev __unused, struct uio *uio __unused, int flags __unused) 105 { 106 107 return (ENOSPC); 108 } 109 110 /* ARGSUSED */ 111 static int 112 null_write(struct cdev *dev __unused, struct uio *uio, int flags __unused) 113 { 114 uio->uio_resid = 0; 115 116 return (0); 117 } 118 119 /* ARGSUSED */ 120 static int 121 null_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused, 122 int flags __unused, struct thread *td) 123 { 124 struct diocskerneldump_arg kda; 125 int error; 126 127 error = 0; 128 switch (cmd) { 129 case DIOCSKERNELDUMP: 130 bzero(&kda, sizeof(kda)); 131 kda.kda_index = KDA_REMOVE_ALL; 132 error = dumper_remove(NULL, &kda); 133 break; 134 case FIONBIO: 135 break; 136 case FIOASYNC: 137 if (*(int *)data != 0) 138 error = EINVAL; 139 break; 140 default: 141 error = ENOIOCTL; 142 } 143 return (error); 144 } 145 146 /* ARGSUSED */ 147 static int 148 zero_ioctl(struct cdev *dev __unused, u_long cmd, caddr_t data __unused, 149 int flags __unused, struct thread *td) 150 { 151 int error; 152 error = 0; 153 154 switch (cmd) { 155 case FIONBIO: 156 break; 157 case FIOASYNC: 158 if (*(int *)data != 0) 159 error = EINVAL; 160 break; 161 default: 162 error = ENOIOCTL; 163 } 164 return (error); 165 } 166 167 /* ARGSUSED */ 168 static int 169 zero_read(struct cdev *dev __unused, struct uio *uio, int flags __unused) 170 { 171 void *zbuf; 172 ssize_t len; 173 int error = 0; 174 175 KASSERT(uio->uio_rw == UIO_READ, 176 ("Can't be in %s for write", __func__)); 177 zbuf = __DECONST(void *, zero_region); 178 while (uio->uio_resid > 0 && error == 0) { 179 len = uio->uio_resid; 180 if (len > ZERO_REGION_SIZE) 181 len = ZERO_REGION_SIZE; 182 error = uiomove(zbuf, len, uio); 183 } 184 185 return (error); 186 } 187 188 /* ARGSUSED */ 189 static int 190 null_modevent(module_t mod __unused, int type, void *data __unused) 191 { 192 switch(type) { 193 case MOD_LOAD: 194 if (bootverbose) 195 printf("null: <full device, null device, zero device>\n"); 196 full_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &full_cdevsw, 0, 197 NULL, UID_ROOT, GID_WHEEL, 0666, "full"); 198 null_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &null_cdevsw, 0, 199 NULL, UID_ROOT, GID_WHEEL, 0666, "null"); 200 zero_dev = make_dev_credf(MAKEDEV_ETERNAL_KLD, &zero_cdevsw, 0, 201 NULL, UID_ROOT, GID_WHEEL, 0666, "zero"); 202 break; 203 204 case MOD_UNLOAD: 205 destroy_dev(full_dev); 206 destroy_dev(null_dev); 207 destroy_dev(zero_dev); 208 break; 209 210 case MOD_SHUTDOWN: 211 break; 212 213 default: 214 return (EOPNOTSUPP); 215 } 216 217 return (0); 218 } 219 220 static int 221 one_ev(struct knote *kn, long hint) 222 { 223 224 return (1); 225 } 226 227 static int 228 zero_ev(struct knote *kn, long hint) 229 { 230 231 return (0); 232 } 233 234 static int 235 kqfilter(struct cdev *dev, struct knote *kn) 236 { 237 238 switch (kn->kn_filter) { 239 case EVFILT_READ: 240 kn->kn_fop = dev->si_devsw == &null_cdevsw ? &zero_fop : &one_fop; 241 return (0); 242 case EVFILT_WRITE: 243 kn->kn_fop = dev->si_devsw == &full_cdevsw ? &zero_fop : &one_fop; 244 return (0); 245 default: 246 return (EOPNOTSUPP); 247 } 248 } 249 250 DEV_MODULE(null, null_modevent, NULL); 251 MODULE_VERSION(null, 1); 252