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