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_now(tmr, tsk->signal->it_real_incr); 167 hrtimer_restart(tmr); 168 } 169 } 170 171 /* 172 * Interval timers are restarted in the signal delivery path. See 173 * posixtimer_rearm_itimer(). 174 */ 175 enum hrtimer_restart it_real_fn(struct hrtimer *timer) 176 { 177 struct signal_struct *sig = 178 container_of(timer, struct signal_struct, real_timer); 179 struct pid *leader_pid = sig->pids[PIDTYPE_TGID]; 180 181 trace_itimer_expire(ITIMER_REAL, leader_pid, 0); 182 kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid); 183 184 return HRTIMER_NORESTART; 185 } 186 187 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id, 188 const struct itimerspec64 *const value, 189 struct itimerspec64 *const ovalue) 190 { 191 u64 oval, nval, ointerval, ninterval; 192 struct cpu_itimer *it = &tsk->signal->it[clock_id]; 193 194 nval = timespec64_to_ns(&value->it_value); 195 ninterval = timespec64_to_ns(&value->it_interval); 196 197 spin_lock_irq(&tsk->sighand->siglock); 198 199 oval = it->expires; 200 ointerval = it->incr; 201 if (oval || nval) { 202 if (nval > 0) 203 nval += TICK_NSEC; 204 set_process_cpu_timer(tsk, clock_id, &nval, &oval); 205 } 206 it->expires = nval; 207 it->incr = ninterval; 208 trace_itimer_state(clock_id == CPUCLOCK_VIRT ? 209 ITIMER_VIRTUAL : ITIMER_PROF, value, nval); 210 211 spin_unlock_irq(&tsk->sighand->siglock); 212 213 if (ovalue) { 214 ovalue->it_value = ns_to_timespec64(oval); 215 ovalue->it_interval = ns_to_timespec64(ointerval); 216 } 217 } 218 219 /* 220 * Returns true if the timeval is in canonical form 221 */ 222 #define timeval_valid(t) \ 223 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC)) 224 225 static int do_setitimer(int which, struct itimerspec64 *value, 226 struct itimerspec64 *ovalue) 227 { 228 struct task_struct *tsk = current; 229 struct hrtimer *timer; 230 ktime_t expires; 231 232 switch (which) { 233 case ITIMER_REAL: 234 again: 235 spin_lock_irq(&tsk->sighand->siglock); 236 timer = &tsk->signal->real_timer; 237 if (ovalue) { 238 ovalue->it_value = itimer_get_remtime(timer); 239 ovalue->it_interval 240 = ktime_to_timespec64(tsk->signal->it_real_incr); 241 } 242 /* We are sharing ->siglock with it_real_fn() */ 243 if (hrtimer_try_to_cancel(timer) < 0) { 244 spin_unlock_irq(&tsk->sighand->siglock); 245 hrtimer_cancel_wait_running(timer); 246 goto again; 247 } 248 expires = timespec64_to_ktime(value->it_value); 249 if (expires != 0) { 250 tsk->signal->it_real_incr = 251 timespec64_to_ktime(value->it_interval); 252 hrtimer_start(timer, expires, HRTIMER_MODE_REL); 253 } else 254 tsk->signal->it_real_incr = 0; 255 256 trace_itimer_state(ITIMER_REAL, value, 0); 257 spin_unlock_irq(&tsk->sighand->siglock); 258 break; 259 case ITIMER_VIRTUAL: 260 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue); 261 break; 262 case ITIMER_PROF: 263 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue); 264 break; 265 default: 266 return -EINVAL; 267 } 268 return 0; 269 } 270 271 #ifdef CONFIG_SECURITY_SELINUX 272 void clear_itimer(void) 273 { 274 struct itimerspec64 v = {}; 275 int i; 276 277 for (i = 0; i < 3; i++) 278 do_setitimer(i, &v, NULL); 279 } 280 #endif 281 282 #ifdef __ARCH_WANT_SYS_ALARM 283 284 /** 285 * alarm_setitimer - set alarm in seconds 286 * 287 * @seconds: number of seconds until alarm 288 * 0 disables the alarm 289 * 290 * Returns the remaining time in seconds of a pending timer or 0 when 291 * the timer is not active. 292 * 293 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid 294 * negative timeval settings which would cause immediate expiry. 295 */ 296 static unsigned int alarm_setitimer(unsigned int seconds) 297 { 298 struct itimerspec64 it_new, it_old; 299 300 #if BITS_PER_LONG < 64 301 if (seconds > INT_MAX) 302 seconds = INT_MAX; 303 #endif 304 it_new.it_value.tv_sec = seconds; 305 it_new.it_value.tv_nsec = 0; 306 it_new.it_interval.tv_sec = it_new.it_interval.tv_nsec = 0; 307 308 do_setitimer(ITIMER_REAL, &it_new, &it_old); 309 310 /* 311 * We can't return 0 if we have an alarm pending ... And we'd 312 * better return too much than too little anyway 313 */ 314 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_nsec) || 315 it_old.it_value.tv_nsec >= (NSEC_PER_SEC / 2)) 316 it_old.it_value.tv_sec++; 317 318 return it_old.it_value.tv_sec; 319 } 320 321 /* 322 * For backwards compatibility? This can be done in libc so Alpha 323 * and all newer ports shouldn't need it. 324 */ 325 SYSCALL_DEFINE1(alarm, unsigned int, seconds) 326 { 327 return alarm_setitimer(seconds); 328 } 329 330 #endif 331 332 static int get_itimerval(struct itimerspec64 *o, const struct __kernel_old_itimerval __user *i) 333 { 334 struct __kernel_old_itimerval v; 335 336 if (copy_from_user(&v, i, sizeof(struct __kernel_old_itimerval))) 337 return -EFAULT; 338 339 /* Validate the timevals in value. */ 340 if (!timeval_valid(&v.it_value) || 341 !timeval_valid(&v.it_interval)) 342 return -EINVAL; 343 344 o->it_interval.tv_sec = v.it_interval.tv_sec; 345 o->it_interval.tv_nsec = v.it_interval.tv_usec * NSEC_PER_USEC; 346 o->it_value.tv_sec = v.it_value.tv_sec; 347 o->it_value.tv_nsec = v.it_value.tv_usec * NSEC_PER_USEC; 348 return 0; 349 } 350 351 SYSCALL_DEFINE3(setitimer, int, which, struct __kernel_old_itimerval __user *, value, 352 struct __kernel_old_itimerval __user *, ovalue) 353 { 354 struct itimerspec64 set_buffer, get_buffer; 355 int error; 356 357 if (value) { 358 error = get_itimerval(&set_buffer, value); 359 if (error) 360 return error; 361 } else { 362 memset(&set_buffer, 0, sizeof(set_buffer)); 363 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer." 364 " Misfeature support will be removed\n", 365 current->comm); 366 } 367 368 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL); 369 if (error || !ovalue) 370 return error; 371 372 if (put_itimerval(ovalue, &get_buffer)) 373 return -EFAULT; 374 return 0; 375 } 376 377 #if defined(CONFIG_COMPAT) || defined(CONFIG_ALPHA) 378 static int get_old_itimerval32(struct itimerspec64 *o, const struct old_itimerval32 __user *i) 379 { 380 struct old_itimerval32 v32; 381 382 if (copy_from_user(&v32, i, sizeof(struct old_itimerval32))) 383 return -EFAULT; 384 385 /* Validate the timevals in value. */ 386 if (!timeval_valid(&v32.it_value) || 387 !timeval_valid(&v32.it_interval)) 388 return -EINVAL; 389 390 o->it_interval.tv_sec = v32.it_interval.tv_sec; 391 o->it_interval.tv_nsec = v32.it_interval.tv_usec * NSEC_PER_USEC; 392 o->it_value.tv_sec = v32.it_value.tv_sec; 393 o->it_value.tv_nsec = v32.it_value.tv_usec * NSEC_PER_USEC; 394 return 0; 395 } 396 397 COMPAT_SYSCALL_DEFINE3(setitimer, int, which, 398 struct old_itimerval32 __user *, value, 399 struct old_itimerval32 __user *, ovalue) 400 { 401 struct itimerspec64 set_buffer, get_buffer; 402 int error; 403 404 if (value) { 405 error = get_old_itimerval32(&set_buffer, value); 406 if (error) 407 return error; 408 } else { 409 memset(&set_buffer, 0, sizeof(set_buffer)); 410 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer." 411 " Misfeature support will be removed\n", 412 current->comm); 413 } 414 415 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL); 416 if (error || !ovalue) 417 return error; 418 if (put_old_itimerval32(ovalue, &get_buffer)) 419 return -EFAULT; 420 return 0; 421 } 422 #endif 423