1 /* 2 * This file and its contents are supplied under the terms of the 3 * Common Development and Distribution License ("CDDL"), version 1.0. 4 * You may only use this file in accordance with the terms of version 5 * 1.0 of the CDDL. 6 * 7 * A full copy of the text of the CDDL should have accompanied this 8 * source. A copy of the CDDL is also available via the Internet at 9 * http://www.illumos.org/license/CDDL. 10 */ 11 12 /* 13 * Copyright 2016 Joyent, Inc. 14 */ 15 16 /* 17 * Support for the eventfd facility, a Linux-borne facility for user-generated 18 * file descriptor-based events. 19 */ 20 21 #include <sys/ddi.h> 22 #include <sys/sunddi.h> 23 #include <sys/eventfd.h> 24 #include <sys/conf.h> 25 #include <sys/vmem.h> 26 #include <sys/sysmacros.h> 27 #include <sys/filio.h> 28 #include <sys/stat.h> 29 #include <sys/file.h> 30 31 struct eventfd_state; 32 typedef struct eventfd_state eventfd_state_t; 33 34 struct eventfd_state { 35 kmutex_t efd_lock; /* lock protecting state */ 36 boolean_t efd_semaphore; /* boolean: sema. semantics */ 37 kcondvar_t efd_cv; /* condvar */ 38 pollhead_t efd_pollhd; /* poll head */ 39 uint64_t efd_value; /* value */ 40 size_t efd_bwriters; /* count of blocked writers */ 41 eventfd_state_t *efd_next; /* next state on global list */ 42 }; 43 44 /* 45 * Internal global variables. 46 */ 47 static kmutex_t eventfd_lock; /* lock protecting state */ 48 static dev_info_t *eventfd_devi; /* device info */ 49 static vmem_t *eventfd_minor; /* minor number arena */ 50 static void *eventfd_softstate; /* softstate pointer */ 51 static eventfd_state_t *eventfd_state; /* global list of state */ 52 53 /*ARGSUSED*/ 54 static int 55 eventfd_open(dev_t *devp, int flag, int otyp, cred_t *cred_p) 56 { 57 eventfd_state_t *state; 58 major_t major = getemajor(*devp); 59 minor_t minor = getminor(*devp); 60 61 if (minor != EVENTFDMNRN_EVENTFD) 62 return (ENXIO); 63 64 mutex_enter(&eventfd_lock); 65 66 minor = (minor_t)(uintptr_t)vmem_alloc(eventfd_minor, 1, 67 VM_BESTFIT | VM_SLEEP); 68 69 if (ddi_soft_state_zalloc(eventfd_softstate, minor) != DDI_SUCCESS) { 70 vmem_free(eventfd_minor, (void *)(uintptr_t)minor, 1); 71 mutex_exit(&eventfd_lock); 72 return (NULL); 73 } 74 75 state = ddi_get_soft_state(eventfd_softstate, minor); 76 *devp = makedevice(major, minor); 77 78 state->efd_next = eventfd_state; 79 eventfd_state = state; 80 81 mutex_exit(&eventfd_lock); 82 83 return (0); 84 } 85 86 /*ARGSUSED*/ 87 static int 88 eventfd_read(dev_t dev, uio_t *uio, cred_t *cr) 89 { 90 eventfd_state_t *state; 91 minor_t minor = getminor(dev); 92 uint64_t val, oval; 93 int err; 94 95 if (uio->uio_resid < sizeof (val)) 96 return (EINVAL); 97 98 state = ddi_get_soft_state(eventfd_softstate, minor); 99 100 mutex_enter(&state->efd_lock); 101 102 while (state->efd_value == 0) { 103 if (uio->uio_fmode & (FNDELAY|FNONBLOCK)) { 104 mutex_exit(&state->efd_lock); 105 return (EAGAIN); 106 } 107 108 if (!cv_wait_sig_swap(&state->efd_cv, &state->efd_lock)) { 109 mutex_exit(&state->efd_lock); 110 return (EINTR); 111 } 112 } 113 114 /* 115 * We have a non-zero value and we own the lock; our behavior now 116 * depends on whether or not EFD_SEMAPHORE was set when the eventfd 117 * was created. 118 */ 119 val = oval = state->efd_value; 120 121 if (state->efd_semaphore) { 122 state->efd_value--; 123 val = 1; 124 } else { 125 state->efd_value = 0; 126 } 127 128 err = uiomove(&val, sizeof (val), UIO_READ, uio); 129 130 /* 131 * Wake any writers blocked on this eventfd as this read operation may 132 * have created adequate capacity for their values. 133 */ 134 if (state->efd_bwriters != 0) { 135 cv_broadcast(&state->efd_cv); 136 } 137 mutex_exit(&state->efd_lock); 138 139 /* 140 * It is necessary to emit POLLOUT events only when the eventfd 141 * transitions from EVENTFD_VALMAX to a lower value. At all other 142 * times, it is already considered writable by poll. 143 */ 144 if (oval == EVENTFD_VALMAX) { 145 pollwakeup(&state->efd_pollhd, POLLWRNORM | POLLOUT); 146 } 147 148 return (err); 149 } 150 151 /*ARGSUSED*/ 152 static int 153 eventfd_write(dev_t dev, struct uio *uio, cred_t *credp) 154 { 155 eventfd_state_t *state; 156 minor_t minor = getminor(dev); 157 uint64_t val, oval; 158 int err; 159 160 if (uio->uio_resid < sizeof (val)) 161 return (EINVAL); 162 163 if ((err = uiomove(&val, sizeof (val), UIO_WRITE, uio)) != 0) 164 return (err); 165 166 if (val > EVENTFD_VALMAX) 167 return (EINVAL); 168 169 state = ddi_get_soft_state(eventfd_softstate, minor); 170 171 mutex_enter(&state->efd_lock); 172 173 while (val > EVENTFD_VALMAX - state->efd_value) { 174 if (uio->uio_fmode & (FNDELAY|FNONBLOCK)) { 175 mutex_exit(&state->efd_lock); 176 return (EAGAIN); 177 } 178 179 state->efd_bwriters++; 180 if (!cv_wait_sig_swap(&state->efd_cv, &state->efd_lock)) { 181 state->efd_bwriters--; 182 mutex_exit(&state->efd_lock); 183 return (EINTR); 184 } 185 state->efd_bwriters--; 186 } 187 188 /* 189 * We now know that we can add the value without overflowing. 190 */ 191 state->efd_value = (oval = state->efd_value) + val; 192 193 /* 194 * If the value was previously "empty", notify blocked readers that 195 * data is available. 196 */ 197 if (oval == 0) { 198 cv_broadcast(&state->efd_cv); 199 } 200 mutex_exit(&state->efd_lock); 201 202 /* 203 * Notify pollers as well if the eventfd is now readable. 204 */ 205 if (oval == 0) { 206 pollwakeup(&state->efd_pollhd, POLLRDNORM | POLLIN); 207 } 208 209 return (0); 210 } 211 212 /*ARGSUSED*/ 213 static int 214 eventfd_poll(dev_t dev, short events, int anyyet, short *reventsp, 215 struct pollhead **phpp) 216 { 217 eventfd_state_t *state; 218 minor_t minor = getminor(dev); 219 short revents = 0; 220 221 state = ddi_get_soft_state(eventfd_softstate, minor); 222 223 mutex_enter(&state->efd_lock); 224 225 if (state->efd_value > 0) 226 revents |= POLLRDNORM | POLLIN; 227 228 if (state->efd_value < EVENTFD_VALMAX) 229 revents |= POLLWRNORM | POLLOUT; 230 231 if (!(*reventsp = revents & events) && !anyyet) 232 *phpp = &state->efd_pollhd; 233 234 mutex_exit(&state->efd_lock); 235 236 return (0); 237 } 238 239 /*ARGSUSED*/ 240 static int 241 eventfd_ioctl(dev_t dev, int cmd, intptr_t arg, int md, cred_t *cr, int *rv) 242 { 243 eventfd_state_t *state; 244 minor_t minor = getminor(dev); 245 246 state = ddi_get_soft_state(eventfd_softstate, minor); 247 248 switch (cmd) { 249 case EVENTFDIOC_SEMAPHORE: { 250 mutex_enter(&state->efd_lock); 251 state->efd_semaphore ^= 1; 252 mutex_exit(&state->efd_lock); 253 254 return (0); 255 } 256 257 default: 258 break; 259 } 260 261 return (ENOTTY); 262 } 263 264 /*ARGSUSED*/ 265 static int 266 eventfd_close(dev_t dev, int flag, int otyp, cred_t *cred_p) 267 { 268 eventfd_state_t *state, **sp; 269 minor_t minor = getminor(dev); 270 271 state = ddi_get_soft_state(eventfd_softstate, minor); 272 273 if (state->efd_pollhd.ph_list != NULL) { 274 pollwakeup(&state->efd_pollhd, POLLERR); 275 pollhead_clean(&state->efd_pollhd); 276 } 277 278 mutex_enter(&eventfd_lock); 279 280 /* 281 * Remove our state from our global list. 282 */ 283 for (sp = &eventfd_state; *sp != state; sp = &((*sp)->efd_next)) 284 VERIFY(*sp != NULL); 285 286 *sp = (*sp)->efd_next; 287 288 ddi_soft_state_free(eventfd_softstate, minor); 289 vmem_free(eventfd_minor, (void *)(uintptr_t)minor, 1); 290 291 mutex_exit(&eventfd_lock); 292 293 return (0); 294 } 295 296 static int 297 eventfd_attach(dev_info_t *devi, ddi_attach_cmd_t cmd) 298 { 299 switch (cmd) { 300 case DDI_ATTACH: 301 break; 302 303 case DDI_RESUME: 304 return (DDI_SUCCESS); 305 306 default: 307 return (DDI_FAILURE); 308 } 309 310 mutex_enter(&eventfd_lock); 311 312 if (ddi_soft_state_init(&eventfd_softstate, 313 sizeof (eventfd_state_t), 0) != 0) { 314 cmn_err(CE_NOTE, "/dev/eventfd failed to create soft state"); 315 mutex_exit(&eventfd_lock); 316 return (DDI_FAILURE); 317 } 318 319 if (ddi_create_minor_node(devi, "eventfd", S_IFCHR, 320 EVENTFDMNRN_EVENTFD, DDI_PSEUDO, NULL) == DDI_FAILURE) { 321 cmn_err(CE_NOTE, "/dev/eventfd couldn't create minor node"); 322 ddi_soft_state_fini(&eventfd_softstate); 323 mutex_exit(&eventfd_lock); 324 return (DDI_FAILURE); 325 } 326 327 ddi_report_dev(devi); 328 eventfd_devi = devi; 329 330 eventfd_minor = vmem_create("eventfd_minor", (void *)EVENTFDMNRN_CLONE, 331 UINT32_MAX - EVENTFDMNRN_CLONE, 1, NULL, NULL, NULL, 0, 332 VM_SLEEP | VMC_IDENTIFIER); 333 334 mutex_exit(&eventfd_lock); 335 336 return (DDI_SUCCESS); 337 } 338 339 /*ARGSUSED*/ 340 static int 341 eventfd_detach(dev_info_t *dip, ddi_detach_cmd_t cmd) 342 { 343 switch (cmd) { 344 case DDI_DETACH: 345 break; 346 347 case DDI_SUSPEND: 348 return (DDI_SUCCESS); 349 350 default: 351 return (DDI_FAILURE); 352 } 353 354 mutex_enter(&eventfd_lock); 355 vmem_destroy(eventfd_minor); 356 357 ddi_remove_minor_node(eventfd_devi, NULL); 358 eventfd_devi = NULL; 359 360 ddi_soft_state_fini(&eventfd_softstate); 361 mutex_exit(&eventfd_lock); 362 363 return (DDI_SUCCESS); 364 } 365 366 /*ARGSUSED*/ 367 static int 368 eventfd_info(dev_info_t *dip, ddi_info_cmd_t infocmd, void *arg, void **result) 369 { 370 int error; 371 372 switch (infocmd) { 373 case DDI_INFO_DEVT2DEVINFO: 374 *result = (void *)eventfd_devi; 375 error = DDI_SUCCESS; 376 break; 377 case DDI_INFO_DEVT2INSTANCE: 378 *result = (void *)0; 379 error = DDI_SUCCESS; 380 break; 381 default: 382 error = DDI_FAILURE; 383 } 384 return (error); 385 } 386 387 static struct cb_ops eventfd_cb_ops = { 388 eventfd_open, /* open */ 389 eventfd_close, /* close */ 390 nulldev, /* strategy */ 391 nulldev, /* print */ 392 nodev, /* dump */ 393 eventfd_read, /* read */ 394 eventfd_write, /* write */ 395 eventfd_ioctl, /* ioctl */ 396 nodev, /* devmap */ 397 nodev, /* mmap */ 398 nodev, /* segmap */ 399 eventfd_poll, /* poll */ 400 ddi_prop_op, /* cb_prop_op */ 401 0, /* streamtab */ 402 D_NEW | D_MP /* Driver compatibility flag */ 403 }; 404 405 static struct dev_ops eventfd_ops = { 406 DEVO_REV, /* devo_rev */ 407 0, /* refcnt */ 408 eventfd_info, /* get_dev_info */ 409 nulldev, /* identify */ 410 nulldev, /* probe */ 411 eventfd_attach, /* attach */ 412 eventfd_detach, /* detach */ 413 nodev, /* reset */ 414 &eventfd_cb_ops, /* driver operations */ 415 NULL, /* bus operations */ 416 nodev, /* dev power */ 417 ddi_quiesce_not_needed, /* quiesce */ 418 }; 419 420 static struct modldrv modldrv = { 421 &mod_driverops, /* module type (this is a pseudo driver) */ 422 "eventfd support", /* name of module */ 423 &eventfd_ops, /* driver ops */ 424 }; 425 426 static struct modlinkage modlinkage = { 427 MODREV_1, 428 (void *)&modldrv, 429 NULL 430 }; 431 432 int 433 _init(void) 434 { 435 return (mod_install(&modlinkage)); 436 } 437 438 int 439 _info(struct modinfo *modinfop) 440 { 441 return (mod_info(&modlinkage, modinfop)); 442 } 443 444 int 445 _fini(void) 446 { 447 return (mod_remove(&modlinkage)); 448 } 449