1 // SPDX-License-Identifier: GPL-2.0 2 /* 3 * linux/kernel/itimer.c 4 * 5 * Copyright (C) 1992 Darren Senn 6 */ 7 8 /* These are all the functions necessary to implement itimers */ 9 10 #include <linux/mm.h> 11 #include <linux/interrupt.h> 12 #include <linux/syscalls.h> 13 #include <linux/time.h> 14 #include <linux/sched/signal.h> 15 #include <linux/sched/cputime.h> 16 #include <linux/posix-timers.h> 17 #include <linux/hrtimer.h> 18 #include <trace/events/timer.h> 19 #include <linux/compat.h> 20 21 #include <linux/uaccess.h> 22 23 /** 24 * itimer_get_remtime - get remaining time for the timer 25 * 26 * @timer: the timer to read 27 * 28 * Returns the delta between the expiry time and now, which can be 29 * less than zero or 1usec for an pending expired timer 30 */ 31 static struct timeval itimer_get_remtime(struct hrtimer *timer) 32 { 33 ktime_t rem = __hrtimer_get_remaining(timer, true); 34 35 /* 36 * Racy but safe: if the itimer expires after the above 37 * hrtimer_get_remtime() call but before this condition 38 * then we return 0 - which is correct. 39 */ 40 if (hrtimer_active(timer)) { 41 if (rem <= 0) 42 rem = NSEC_PER_USEC; 43 } else 44 rem = 0; 45 46 return ktime_to_timeval(rem); 47 } 48 49 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id, 50 struct itimerval *const value) 51 { 52 u64 val, interval; 53 struct cpu_itimer *it = &tsk->signal->it[clock_id]; 54 55 spin_lock_irq(&tsk->sighand->siglock); 56 57 val = it->expires; 58 interval = it->incr; 59 if (val) { 60 struct task_cputime cputime; 61 u64 t; 62 63 thread_group_cputimer(tsk, &cputime); 64 if (clock_id == CPUCLOCK_PROF) 65 t = cputime.utime + cputime.stime; 66 else 67 /* CPUCLOCK_VIRT */ 68 t = cputime.utime; 69 70 if (val < t) 71 /* about to fire */ 72 val = TICK_NSEC; 73 else 74 val -= t; 75 } 76 77 spin_unlock_irq(&tsk->sighand->siglock); 78 79 value->it_value = ns_to_timeval(val); 80 value->it_interval = ns_to_timeval(interval); 81 } 82 83 int do_getitimer(int which, struct itimerval *value) 84 { 85 struct task_struct *tsk = current; 86 87 switch (which) { 88 case ITIMER_REAL: 89 spin_lock_irq(&tsk->sighand->siglock); 90 value->it_value = itimer_get_remtime(&tsk->signal->real_timer); 91 value->it_interval = 92 ktime_to_timeval(tsk->signal->it_real_incr); 93 spin_unlock_irq(&tsk->sighand->siglock); 94 break; 95 case ITIMER_VIRTUAL: 96 get_cpu_itimer(tsk, CPUCLOCK_VIRT, value); 97 break; 98 case ITIMER_PROF: 99 get_cpu_itimer(tsk, CPUCLOCK_PROF, value); 100 break; 101 default: 102 return(-EINVAL); 103 } 104 return 0; 105 } 106 107 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value) 108 { 109 int error = -EFAULT; 110 struct itimerval get_buffer; 111 112 if (value) { 113 error = do_getitimer(which, &get_buffer); 114 if (!error && 115 copy_to_user(value, &get_buffer, sizeof(get_buffer))) 116 error = -EFAULT; 117 } 118 return error; 119 } 120 121 #ifdef CONFIG_COMPAT 122 COMPAT_SYSCALL_DEFINE2(getitimer, int, which, 123 struct compat_itimerval __user *, it) 124 { 125 struct itimerval kit; 126 int error = do_getitimer(which, &kit); 127 128 if (!error && put_compat_itimerval(it, &kit)) 129 error = -EFAULT; 130 return error; 131 } 132 #endif 133 134 135 /* 136 * The timer is automagically restarted, when interval != 0 137 */ 138 enum hrtimer_restart it_real_fn(struct hrtimer *timer) 139 { 140 struct signal_struct *sig = 141 container_of(timer, struct signal_struct, real_timer); 142 struct pid *leader_pid = sig->pids[PIDTYPE_TGID]; 143 144 trace_itimer_expire(ITIMER_REAL, leader_pid, 0); 145 kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid); 146 147 return HRTIMER_NORESTART; 148 } 149 150 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id, 151 const struct itimerval *const value, 152 struct itimerval *const ovalue) 153 { 154 u64 oval, nval, ointerval, ninterval; 155 struct cpu_itimer *it = &tsk->signal->it[clock_id]; 156 157 /* 158 * Use the to_ktime conversion because that clamps the maximum 159 * value to KTIME_MAX and avoid multiplication overflows. 160 */ 161 nval = ktime_to_ns(timeval_to_ktime(value->it_value)); 162 ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval)); 163 164 spin_lock_irq(&tsk->sighand->siglock); 165 166 oval = it->expires; 167 ointerval = it->incr; 168 if (oval || nval) { 169 if (nval > 0) 170 nval += TICK_NSEC; 171 set_process_cpu_timer(tsk, clock_id, &nval, &oval); 172 } 173 it->expires = nval; 174 it->incr = ninterval; 175 trace_itimer_state(clock_id == CPUCLOCK_VIRT ? 176 ITIMER_VIRTUAL : ITIMER_PROF, value, nval); 177 178 spin_unlock_irq(&tsk->sighand->siglock); 179 180 if (ovalue) { 181 ovalue->it_value = ns_to_timeval(oval); 182 ovalue->it_interval = ns_to_timeval(ointerval); 183 } 184 } 185 186 /* 187 * Returns true if the timeval is in canonical form 188 */ 189 #define timeval_valid(t) \ 190 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC)) 191 192 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue) 193 { 194 struct task_struct *tsk = current; 195 struct hrtimer *timer; 196 ktime_t expires; 197 198 /* 199 * Validate the timevals in value. 200 */ 201 if (!timeval_valid(&value->it_value) || 202 !timeval_valid(&value->it_interval)) 203 return -EINVAL; 204 205 switch (which) { 206 case ITIMER_REAL: 207 again: 208 spin_lock_irq(&tsk->sighand->siglock); 209 timer = &tsk->signal->real_timer; 210 if (ovalue) { 211 ovalue->it_value = itimer_get_remtime(timer); 212 ovalue->it_interval 213 = ktime_to_timeval(tsk->signal->it_real_incr); 214 } 215 /* We are sharing ->siglock with it_real_fn() */ 216 if (hrtimer_try_to_cancel(timer) < 0) { 217 spin_unlock_irq(&tsk->sighand->siglock); 218 goto again; 219 } 220 expires = timeval_to_ktime(value->it_value); 221 if (expires != 0) { 222 tsk->signal->it_real_incr = 223 timeval_to_ktime(value->it_interval); 224 hrtimer_start(timer, expires, HRTIMER_MODE_REL); 225 } else 226 tsk->signal->it_real_incr = 0; 227 228 trace_itimer_state(ITIMER_REAL, value, 0); 229 spin_unlock_irq(&tsk->sighand->siglock); 230 break; 231 case ITIMER_VIRTUAL: 232 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue); 233 break; 234 case ITIMER_PROF: 235 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue); 236 break; 237 default: 238 return -EINVAL; 239 } 240 return 0; 241 } 242 243 #ifdef __ARCH_WANT_SYS_ALARM 244 245 /** 246 * alarm_setitimer - set alarm in seconds 247 * 248 * @seconds: number of seconds until alarm 249 * 0 disables the alarm 250 * 251 * Returns the remaining time in seconds of a pending timer or 0 when 252 * the timer is not active. 253 * 254 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid 255 * negative timeval settings which would cause immediate expiry. 256 */ 257 static unsigned int alarm_setitimer(unsigned int seconds) 258 { 259 struct itimerval it_new, it_old; 260 261 #if BITS_PER_LONG < 64 262 if (seconds > INT_MAX) 263 seconds = INT_MAX; 264 #endif 265 it_new.it_value.tv_sec = seconds; 266 it_new.it_value.tv_usec = 0; 267 it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0; 268 269 do_setitimer(ITIMER_REAL, &it_new, &it_old); 270 271 /* 272 * We can't return 0 if we have an alarm pending ... And we'd 273 * better return too much than too little anyway 274 */ 275 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) || 276 it_old.it_value.tv_usec >= 500000) 277 it_old.it_value.tv_sec++; 278 279 return it_old.it_value.tv_sec; 280 } 281 282 /* 283 * For backwards compatibility? This can be done in libc so Alpha 284 * and all newer ports shouldn't need it. 285 */ 286 SYSCALL_DEFINE1(alarm, unsigned int, seconds) 287 { 288 return alarm_setitimer(seconds); 289 } 290 291 #endif 292 293 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value, 294 struct itimerval __user *, ovalue) 295 { 296 struct itimerval set_buffer, get_buffer; 297 int error; 298 299 if (value) { 300 if(copy_from_user(&set_buffer, value, sizeof(set_buffer))) 301 return -EFAULT; 302 } else { 303 memset(&set_buffer, 0, sizeof(set_buffer)); 304 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer." 305 " Misfeature support will be removed\n", 306 current->comm); 307 } 308 309 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL); 310 if (error || !ovalue) 311 return error; 312 313 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer))) 314 return -EFAULT; 315 return 0; 316 } 317 318 #ifdef CONFIG_COMPAT 319 COMPAT_SYSCALL_DEFINE3(setitimer, int, which, 320 struct compat_itimerval __user *, in, 321 struct compat_itimerval __user *, out) 322 { 323 struct itimerval kin, kout; 324 int error; 325 326 if (in) { 327 if (get_compat_itimerval(&kin, in)) 328 return -EFAULT; 329 } else { 330 memset(&kin, 0, sizeof(kin)); 331 } 332 333 error = do_setitimer(which, &kin, out ? &kout : NULL); 334 if (error || !out) 335 return error; 336 if (put_compat_itimerval(out, &kout)) 337 return -EFAULT; 338 return 0; 339 } 340 #endif 341