1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * Copyright (C) 1992 Darren Senn 4 */ 5 6 /* These are all the functions necessary to implement itimers */ 7 8 #include <linux/mm.h> 9 #include <linux/interrupt.h> 10 #include <linux/syscalls.h> 11 #include <linux/time.h> 12 #include <linux/sched/signal.h> 13 #include <linux/sched/cputime.h> 14 #include <linux/posix-timers.h> 15 #include <linux/hrtimer.h> 16 #include <trace/events/timer.h> 17 #include <linux/compat.h> 18 19 #include <linux/uaccess.h> 20 21 /** 22 * itimer_get_remtime - get remaining time for the timer 23 * 24 * @timer: the timer to read 25 * 26 * Returns the delta between the expiry time and now, which can be 27 * less than zero or 1usec for an pending expired timer 28 */ 29 static struct timespec64 itimer_get_remtime(struct hrtimer *timer) 30 { 31 ktime_t rem = __hrtimer_get_remaining(timer, true); 32 33 /* 34 * Racy but safe: if the itimer expires after the above 35 * hrtimer_get_remtime() call but before this condition 36 * then we return 0 - which is correct. 37 */ 38 if (hrtimer_active(timer)) { 39 if (rem <= 0) 40 rem = NSEC_PER_USEC; 41 } else 42 rem = 0; 43 44 return ktime_to_timespec64(rem); 45 } 46 47 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id, 48 struct itimerspec64 *const value) 49 { 50 u64 val, interval; 51 struct cpu_itimer *it = &tsk->signal->it[clock_id]; 52 53 spin_lock_irq(&tsk->sighand->siglock); 54 55 val = it->expires; 56 interval = it->incr; 57 if (val) { 58 u64 t, samples[CPUCLOCK_MAX]; 59 60 thread_group_sample_cputime(tsk, samples); 61 t = samples[clock_id]; 62 63 if (val < t) 64 /* about to fire */ 65 val = TICK_NSEC; 66 else 67 val -= t; 68 } 69 70 spin_unlock_irq(&tsk->sighand->siglock); 71 72 value->it_value = ns_to_timespec64(val); 73 value->it_interval = ns_to_timespec64(interval); 74 } 75 76 static int do_getitimer(int which, struct itimerspec64 *value) 77 { 78 struct task_struct *tsk = current; 79 80 switch (which) { 81 case ITIMER_REAL: 82 spin_lock_irq(&tsk->sighand->siglock); 83 value->it_value = itimer_get_remtime(&tsk->signal->real_timer); 84 value->it_interval = 85 ktime_to_timespec64(tsk->signal->it_real_incr); 86 spin_unlock_irq(&tsk->sighand->siglock); 87 break; 88 case ITIMER_VIRTUAL: 89 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value); 90 break; 91 case ITIMER_PROF: 92 get_cpu_itimer(tsk, CPUCLOCK_PROF, value); 93 break; 94 default: 95 return(-EINVAL); 96 } 97 return 0; 98 } 99 100 static int put_itimerval(struct __kernel_old_itimerval __user *o, 101 const struct itimerspec64 *i) 102 { 103 struct __kernel_old_itimerval v; 104 105 v.it_interval.tv_sec = i->it_interval.tv_sec; 106 v.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC; 107 v.it_value.tv_sec = i->it_value.tv_sec; 108 v.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC; 109 return copy_to_user(o, &v, sizeof(struct __kernel_old_itimerval)) ? -EFAULT : 0; 110 } 111 112 113 SYSCALL_DEFINE2(getitimer, int, which, struct __kernel_old_itimerval __user *, value) 114 { 115 struct itimerspec64 get_buffer; 116 int error = do_getitimer(which, &get_buffer); 117 118 if (!error && put_itimerval(value, &get_buffer)) 119 error = -EFAULT; 120 return error; 121 } 122 123 #if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA) 124 struct old_itimerval32 { 125 struct old_timeval32 it_interval; 126 struct old_timeval32 it_value; 127 }; 128 129 static int put_old_itimerval32(struct old_itimerval32 __user *o, 130 const struct itimerspec64 *i) 131 { 132 struct old_itimerval32 v32; 133 134 v32.it_interval.tv_sec = i->it_interval.tv_sec; 135 v32.it_interval.tv_usec = i->it_interval.tv_nsec / NSEC_PER_USEC; 136 v32.it_value.tv_sec = i->it_value.tv_sec; 137 v32.it_value.tv_usec = i->it_value.tv_nsec / NSEC_PER_USEC; 138 return copy_to_user(o, &v32, sizeof(struct old_itimerval32)) ? -EFAULT : 0; 139 } 140 141 COMPAT_SYSCALL_DEFINE2(getitimer, int, which, 142 struct old_itimerval32 __user *, value) 143 { 144 struct itimerspec64 get_buffer; 145 int error = do_getitimer(which, &get_buffer); 146 147 if (!error && put_old_itimerval32(value, &get_buffer)) 148 error = -EFAULT; 149 return error; 150 } 151 #endif 152 153 /* 154 * Invoked from dequeue_signal() when SIG_ALRM is delivered. 155 * 156 * Restart the ITIMER_REAL timer if it is armed as periodic timer. Doing 157 * this in the signal delivery path instead of self rearming prevents a DoS 158 * with small increments in the high reolution timer case and reduces timer 159 * noise in general. 160 */ 161 void posixtimer_rearm_itimer(struct task_struct *tsk) 162 { 163 struct hrtimer *tmr = &tsk->signal->real_timer; 164 165 if (!hrtimer_is_queued(tmr) && tsk->signal->it_real_incr != 0) { 166 hrtimer_forward(tmr, tmr->base->get_time(), 167 tsk->signal->it_real_incr); 168 hrtimer_restart(tmr); 169 } 170 } 171 172 /* 173 * Interval timers are restarted in the signal delivery path. See 174 * posixtimer_rearm_itimer(). 175 */ 176 enum hrtimer_restart it_real_fn(struct hrtimer *timer) 177 { 178 struct signal_struct *sig = 179 container_of(timer, struct signal_struct, real_timer); 180 struct pid *leader_pid = sig->pids[PIDTYPE_TGID]; 181 182 trace_itimer_expire(ITIMER_REAL, leader_pid, 0); 183 kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid); 184 185 return HRTIMER_NORESTART; 186 } 187 188 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id, 189 const struct itimerspec64 *const value, 190 struct itimerspec64 *const ovalue) 191 { 192 u64 oval, nval, ointerval, ninterval; 193 struct cpu_itimer *it = &tsk->signal->it[clock_id]; 194 195 nval = timespec64_to_ns(&value->it_value); 196 ninterval = timespec64_to_ns(&value->it_interval); 197 198 spin_lock_irq(&tsk->sighand->siglock); 199 200 oval = it->expires; 201 ointerval = it->incr; 202 if (oval || nval) { 203 if (nval > 0) 204 nval += TICK_NSEC; 205 set_process_cpu_timer(tsk, clock_id, &nval, &oval); 206 } 207 it->expires = nval; 208 it->incr = ninterval; 209 trace_itimer_state(clock_id == CPUCLOCK_VIRT ? 210 ITIMER_VIRTUAL : ITIMER_PROF, value, nval); 211 212 spin_unlock_irq(&tsk->sighand->siglock); 213 214 if (ovalue) { 215 ovalue->it_value = ns_to_timespec64(oval); 216 ovalue->it_interval = ns_to_timespec64(ointerval); 217 } 218 } 219 220 /* 221 * Returns true if the timeval is in canonical form 222 */ 223 #define timeval_valid(t) \ 224 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC)) 225 226 static int do_setitimer(int which, struct itimerspec64 *value, 227 struct itimerspec64 *ovalue) 228 { 229 struct task_struct *tsk = current; 230 struct hrtimer *timer; 231 ktime_t expires; 232 233 switch (which) { 234 case ITIMER_REAL: 235 again: 236 spin_lock_irq(&tsk->sighand->siglock); 237 timer = &tsk->signal->real_timer; 238 if (ovalue) { 239 ovalue->it_value = itimer_get_remtime(timer); 240 ovalue->it_interval 241 = ktime_to_timespec64(tsk->signal->it_real_incr); 242 } 243 /* We are sharing ->siglock with it_real_fn() */ 244 if (hrtimer_try_to_cancel(timer) < 0) { 245 spin_unlock_irq(&tsk->sighand->siglock); 246 hrtimer_cancel_wait_running(timer); 247 goto again; 248 } 249 expires = timespec64_to_ktime(value->it_value); 250 if (expires != 0) { 251 tsk->signal->it_real_incr = 252 timespec64_to_ktime(value->it_interval); 253 hrtimer_start(timer, expires, HRTIMER_MODE_REL); 254 } else 255 tsk->signal->it_real_incr = 0; 256 257 trace_itimer_state(ITIMER_REAL, value, 0); 258 spin_unlock_irq(&tsk->sighand->siglock); 259 break; 260 case ITIMER_VIRTUAL: 261 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue); 262 break; 263 case ITIMER_PROF: 264 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue); 265 break; 266 default: 267 return -EINVAL; 268 } 269 return 0; 270 } 271 272 #ifdef CONFIG_SECURITY_SELINUX 273 void clear_itimer(void) 274 { 275 struct itimerspec64 v = {}; 276 int i; 277 278 for (i = 0; i < 3; i++) 279 do_setitimer(i, &v, NULL); 280 } 281 #endif 282 283 #ifdef __ARCH_WANT_SYS_ALARM 284 285 /** 286 * alarm_setitimer - set alarm in seconds 287 * 288 * @seconds: number of seconds until alarm 289 * 0 disables the alarm 290 * 291 * Returns the remaining time in seconds of a pending timer or 0 when 292 * the timer is not active. 293 * 294 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid 295 * negative timeval settings which would cause immediate expiry. 296 */ 297 static unsigned int alarm_setitimer(unsigned int seconds) 298 { 299 struct itimerspec64 it_new, it_old; 300 301 #if BITS_PER_LONG < 64 302 if (seconds > INT_MAX) 303 seconds = INT_MAX; 304 #endif 305 it_new.it_value.tv_sec = seconds; 306 it_new.it_value.tv_nsec = 0; 307 it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 0; 308 309 do_setitimer(ITIMER_REAL, &it_new, &it_old); 310 311 /* 312 * We can't return 0 if we have an alarm pending ... And we'd 313 * better return too much than too little anyway 314 */ 315 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_nsec) || 316 it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2)) 317 it_old.it_value.tv_sec++; 318 319 return it_old.it_value.tv_sec; 320 } 321 322 /* 323 * For backwards compatibility? This can be done in libc so Alpha 324 * and all newer ports shouldn't need it. 325 */ 326 SYSCALL_DEFINE1(alarm, unsigned int, seconds) 327 { 328 return alarm_setitimer(seconds); 329 } 330 331 #endif 332 333 static int get_itimerval(struct itimerspec64 *o, const struct __kernel_old_itimerval __user *i) 334 { 335 struct __kernel_old_itimerval v; 336 337 if (copy_from_user(&v, i, sizeof(struct __kernel_old_itimerval))) 338 return -EFAULT; 339 340 /* Validate the timevals in value. */ 341 if (!timeval_valid(&v.it_value) || 342 !timeval_valid(&v.it_interval)) 343 return -EINVAL; 344 345 o->it_interval.tv_sec = v.it_interval.tv_sec; 346 o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC; 347 o->it_value.tv_sec = v.it_value.tv_sec; 348 o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC; 349 return 0; 350 } 351 352 SYSCALL_DEFINE3(setitimer, int, which, struct __kernel_old_itimerval __user *, value, 353 struct __kernel_old_itimerval __user *, ovalue) 354 { 355 struct itimerspec64 set_buffer, get_buffer; 356 int error; 357 358 if (value) { 359 error = get_itimerval(&set_buffer, value); 360 if (error) 361 return error; 362 } else { 363 memset(&set_buffer, 0, sizeof(set_buffer)); 364 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer." 365 " Misfeature support will be removed\n", 366 current->comm); 367 } 368 369 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL); 370 if (error || !ovalue) 371 return error; 372 373 if (put_itimerval(ovalue, &get_buffer)) 374 return -EFAULT; 375 return 0; 376 } 377 378 #if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA) 379 static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i) 380 { 381 struct old_itimerval32 v32; 382 383 if (copy_from_user(&v32, i, sizeof(struct old_itimerval32))) 384 return -EFAULT; 385 386 /* Validate the timevals in value. */ 387 if (!timeval_valid(&v32.it_value) || 388 !timeval_valid(&v32.it_interval)) 389 return -EINVAL; 390 391 o->it_interval.tv_sec = v32.it_interval.tv_sec; 392 o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC; 393 o->it_value.tv_sec = v32.it_value.tv_sec; 394 o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC; 395 return 0; 396 } 397 398 COMPAT_SYSCALL_DEFINE3(setitimer, int, which, 399 struct old_itimerval32 __user *, value, 400 struct old_itimerval32 __user *, ovalue) 401 { 402 struct itimerspec64 set_buffer, get_buffer; 403 int error; 404 405 if (value) { 406 error = get_old_itimerval32(&set_buffer, value); 407 if (error) 408 return error; 409 } else { 410 memset(&set_buffer, 0, sizeof(set_buffer)); 411 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer." 412 " Misfeature support will be removed\n", 413 current->comm); 414 } 415 416 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL); 417 if (error || !ovalue) 418 return error; 419 if (put_old_itimerval32(ovalue, &get_buffer)) 420 return -EFAULT; 421 return 0; 422 } 423 #endif 424