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); 142 143 trace_itimer_expire(ITIMER_REAL, sig->leader_pid, 0); 144 kill_pid_info(SIGALRM, SEND_SIG_PRIV, sig->leader_pid); 145 146 return HRTIMER_NORESTART; 147 } 148 149 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id, 150 const struct itimerval *const value, 151 struct itimerval *const ovalue) 152 { 153 u64 oval, nval, ointerval, ninterval; 154 struct cpu_itimer *it = &tsk->signal->it[clock_id]; 155 156 /* 157 * Use the to_ktime conversion because that clamps the maximum 158 * value to KTIME_MAX and avoid multiplication overflows. 159 */ 160 nval = ktime_to_ns(timeval_to_ktime(value->it_value)); 161 ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval)); 162 163 spin_lock_irq(&tsk->sighand->siglock); 164 165 oval = it->expires; 166 ointerval = it->incr; 167 if (oval || nval) { 168 if (nval > 0) 169 nval += TICK_NSEC; 170 set_process_cpu_timer(tsk, clock_id, &nval, &oval); 171 } 172 it->expires = nval; 173 it->incr = ninterval; 174 trace_itimer_state(clock_id == CPUCLOCK_VIRT ? 175 ITIMER_VIRTUAL : ITIMER_PROF, value, nval); 176 177 spin_unlock_irq(&tsk->sighand->siglock); 178 179 if (ovalue) { 180 ovalue->it_value = ns_to_timeval(oval); 181 ovalue->it_interval = ns_to_timeval(ointerval); 182 } 183 } 184 185 /* 186 * Returns true if the timeval is in canonical form 187 */ 188 #define timeval_valid(t) \ 189 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC)) 190 191 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue) 192 { 193 struct task_struct *tsk = current; 194 struct hrtimer *timer; 195 ktime_t expires; 196 197 /* 198 * Validate the timevals in value. 199 */ 200 if (!timeval_valid(&value->it_value) || 201 !timeval_valid(&value->it_interval)) 202 return -EINVAL; 203 204 switch (which) { 205 case ITIMER_REAL: 206 again: 207 spin_lock_irq(&tsk->sighand->siglock); 208 timer = &tsk->signal->real_timer; 209 if (ovalue) { 210 ovalue->it_value = itimer_get_remtime(timer); 211 ovalue->it_interval 212 = ktime_to_timeval(tsk->signal->it_real_incr); 213 } 214 /* We are sharing ->siglock with it_real_fn() */ 215 if (hrtimer_try_to_cancel(timer) < 0) { 216 spin_unlock_irq(&tsk->sighand->siglock); 217 goto again; 218 } 219 expires = timeval_to_ktime(value->it_value); 220 if (expires != 0) { 221 tsk->signal->it_real_incr = 222 timeval_to_ktime(value->it_interval); 223 hrtimer_start(timer, expires, HRTIMER_MODE_REL); 224 } else 225 tsk->signal->it_real_incr = 0; 226 227 trace_itimer_state(ITIMER_REAL, value, 0); 228 spin_unlock_irq(&tsk->sighand->siglock); 229 break; 230 case ITIMER_VIRTUAL: 231 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue); 232 break; 233 case ITIMER_PROF: 234 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue); 235 break; 236 default: 237 return -EINVAL; 238 } 239 return 0; 240 } 241 242 #ifdef __ARCH_WANT_SYS_ALARM 243 244 /** 245 * alarm_setitimer - set alarm in seconds 246 * 247 * @seconds: number of seconds until alarm 248 * 0 disables the alarm 249 * 250 * Returns the remaining time in seconds of a pending timer or 0 when 251 * the timer is not active. 252 * 253 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid 254 * negative timeval settings which would cause immediate expiry. 255 */ 256 static unsigned int alarm_setitimer(unsigned int seconds) 257 { 258 struct itimerval it_new, it_old; 259 260 #if BITS_PER_LONG < 64 261 if (seconds > INT_MAX) 262 seconds = INT_MAX; 263 #endif 264 it_new.it_value.tv_sec = seconds; 265 it_new.it_value.tv_usec = 0; 266 it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0; 267 268 do_setitimer(ITIMER_REAL, &it_new, &it_old); 269 270 /* 271 * We can't return 0 if we have an alarm pending ... And we'd 272 * better return too much than too little anyway 273 */ 274 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) || 275 it_old.it_value.tv_usec >= 500000) 276 it_old.it_value.tv_sec++; 277 278 return it_old.it_value.tv_sec; 279 } 280 281 /* 282 * For backwards compatibility? This can be done in libc so Alpha 283 * and all newer ports shouldn't need it. 284 */ 285 SYSCALL_DEFINE1(alarm, unsigned int, seconds) 286 { 287 return alarm_setitimer(seconds); 288 } 289 290 #endif 291 292 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value, 293 struct itimerval __user *, ovalue) 294 { 295 struct itimerval set_buffer, get_buffer; 296 int error; 297 298 if (value) { 299 if(copy_from_user(&set_buffer, value, sizeof(set_buffer))) 300 return -EFAULT; 301 } else { 302 memset(&set_buffer, 0, sizeof(set_buffer)); 303 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer." 304 " Misfeature support will be removed\n", 305 current->comm); 306 } 307 308 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL); 309 if (error || !ovalue) 310 return error; 311 312 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer))) 313 return -EFAULT; 314 return 0; 315 } 316 317 #ifdef CONFIG_COMPAT 318 COMPAT_SYSCALL_DEFINE3(setitimer, int, which, 319 struct compat_itimerval __user *, in, 320 struct compat_itimerval __user *, out) 321 { 322 struct itimerval kin, kout; 323 int error; 324 325 if (in) { 326 if (get_compat_itimerval(&kin, in)) 327 return -EFAULT; 328 } else { 329 memset(&kin, 0, sizeof(kin)); 330 } 331 332 error = do_setitimer(which, &kin, out ? &kout : NULL); 333 if (error || !out) 334 return error; 335 if (put_compat_itimerval(out, &kout)) 336 return -EFAULT; 337 return 0; 338 } 339 #endif 340