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 timeval 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_timeval(rem); 45 } 46 47 static void get_cpu_itimer(struct task_struct *tsk, unsigned int clock_id, 48 struct itimerval *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_timeval(val); 73 value->it_interval = ns_to_timeval(interval); 74 } 75 76 int do_getitimer(int which, struct itimerval *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_timeval(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 SYSCALL_DEFINE2(getitimer, int, which, struct itimerval __user *, value) 101 { 102 int error = -EFAULT; 103 struct itimerval get_buffer; 104 105 if (value) { 106 error = do_getitimer(which, &get_buffer); 107 if (!error && 108 copy_to_user(value, &get_buffer, sizeof(get_buffer))) 109 error = -EFAULT; 110 } 111 return error; 112 } 113 114 #ifdef CONFIG_COMPAT 115 COMPAT_SYSCALL_DEFINE2(getitimer, int, which, 116 struct compat_itimerval __user *, it) 117 { 118 struct itimerval kit; 119 int error = do_getitimer(which, &kit); 120 121 if (!error && put_compat_itimerval(it, &kit)) 122 error = -EFAULT; 123 return error; 124 } 125 #endif 126 127 128 /* 129 * The timer is automagically restarted, when interval != 0 130 */ 131 enum hrtimer_restart it_real_fn(struct hrtimer *timer) 132 { 133 struct signal_struct *sig = 134 container_of(timer, struct signal_struct, real_timer); 135 struct pid *leader_pid = sig->pids[PIDTYPE_TGID]; 136 137 trace_itimer_expire(ITIMER_REAL, leader_pid, 0); 138 kill_pid_info(SIGALRM, SEND_SIG_PRIV, leader_pid); 139 140 return HRTIMER_NORESTART; 141 } 142 143 static void set_cpu_itimer(struct task_struct *tsk, unsigned int clock_id, 144 const struct itimerval *const value, 145 struct itimerval *const ovalue) 146 { 147 u64 oval, nval, ointerval, ninterval; 148 struct cpu_itimer *it = &tsk->signal->it[clock_id]; 149 150 /* 151 * Use the to_ktime conversion because that clamps the maximum 152 * value to KTIME_MAX and avoid multiplication overflows. 153 */ 154 nval = ktime_to_ns(timeval_to_ktime(value->it_value)); 155 ninterval = ktime_to_ns(timeval_to_ktime(value->it_interval)); 156 157 spin_lock_irq(&tsk->sighand->siglock); 158 159 oval = it->expires; 160 ointerval = it->incr; 161 if (oval || nval) { 162 if (nval > 0) 163 nval += TICK_NSEC; 164 set_process_cpu_timer(tsk, clock_id, &nval, &oval); 165 } 166 it->expires = nval; 167 it->incr = ninterval; 168 trace_itimer_state(clock_id == CPUCLOCK_VIRT ? 169 ITIMER_VIRTUAL : ITIMER_PROF, value, nval); 170 171 spin_unlock_irq(&tsk->sighand->siglock); 172 173 if (ovalue) { 174 ovalue->it_value = ns_to_timeval(oval); 175 ovalue->it_interval = ns_to_timeval(ointerval); 176 } 177 } 178 179 /* 180 * Returns true if the timeval is in canonical form 181 */ 182 #define timeval_valid(t) \ 183 (((t)->tv_sec >= 0) && (((unsigned long) (t)->tv_usec) < USEC_PER_SEC)) 184 185 int do_setitimer(int which, struct itimerval *value, struct itimerval *ovalue) 186 { 187 struct task_struct *tsk = current; 188 struct hrtimer *timer; 189 ktime_t expires; 190 191 /* 192 * Validate the timevals in value. 193 */ 194 if (!timeval_valid(&value->it_value) || 195 !timeval_valid(&value->it_interval)) 196 return -EINVAL; 197 198 switch (which) { 199 case ITIMER_REAL: 200 again: 201 spin_lock_irq(&tsk->sighand->siglock); 202 timer = &tsk->signal->real_timer; 203 if (ovalue) { 204 ovalue->it_value = itimer_get_remtime(timer); 205 ovalue->it_interval 206 = ktime_to_timeval(tsk->signal->it_real_incr); 207 } 208 /* We are sharing ->siglock with it_real_fn() */ 209 if (hrtimer_try_to_cancel(timer) < 0) { 210 spin_unlock_irq(&tsk->sighand->siglock); 211 hrtimer_cancel_wait_running(timer); 212 goto again; 213 } 214 expires = timeval_to_ktime(value->it_value); 215 if (expires != 0) { 216 tsk->signal->it_real_incr = 217 timeval_to_ktime(value->it_interval); 218 hrtimer_start(timer, expires, HRTIMER_MODE_REL); 219 } else 220 tsk->signal->it_real_incr = 0; 221 222 trace_itimer_state(ITIMER_REAL, value, 0); 223 spin_unlock_irq(&tsk->sighand->siglock); 224 break; 225 case ITIMER_VIRTUAL: 226 set_cpu_itimer(tsk, CPUCLOCK_VIRT, value, ovalue); 227 break; 228 case ITIMER_PROF: 229 set_cpu_itimer(tsk, CPUCLOCK_PROF, value, ovalue); 230 break; 231 default: 232 return -EINVAL; 233 } 234 return 0; 235 } 236 237 #ifdef __ARCH_WANT_SYS_ALARM 238 239 /** 240 * alarm_setitimer - set alarm in seconds 241 * 242 * @seconds: number of seconds until alarm 243 * 0 disables the alarm 244 * 245 * Returns the remaining time in seconds of a pending timer or 0 when 246 * the timer is not active. 247 * 248 * On 32 bit machines the seconds value is limited to (INT_MAX/2) to avoid 249 * negative timeval settings which would cause immediate expiry. 250 */ 251 static unsigned int alarm_setitimer(unsigned int seconds) 252 { 253 struct itimerval it_new, it_old; 254 255 #if BITS_PER_LONG < 64 256 if (seconds > INT_MAX) 257 seconds = INT_MAX; 258 #endif 259 it_new.it_value.tv_sec = seconds; 260 it_new.it_value.tv_usec = 0; 261 it_new.it_interval.tv_sec = it_new.it_interval.tv_usec = 0; 262 263 do_setitimer(ITIMER_REAL, &it_new, &it_old); 264 265 /* 266 * We can't return 0 if we have an alarm pending ... And we'd 267 * better return too much than too little anyway 268 */ 269 if ((!it_old.it_value.tv_sec && it_old.it_value.tv_usec) || 270 it_old.it_value.tv_usec >= 500000) 271 it_old.it_value.tv_sec++; 272 273 return it_old.it_value.tv_sec; 274 } 275 276 /* 277 * For backwards compatibility? This can be done in libc so Alpha 278 * and all newer ports shouldn't need it. 279 */ 280 SYSCALL_DEFINE1(alarm, unsigned int, seconds) 281 { 282 return alarm_setitimer(seconds); 283 } 284 285 #endif 286 287 SYSCALL_DEFINE3(setitimer, int, which, struct itimerval __user *, value, 288 struct itimerval __user *, ovalue) 289 { 290 struct itimerval set_buffer, get_buffer; 291 int error; 292 293 if (value) { 294 if(copy_from_user(&set_buffer, value, sizeof(set_buffer))) 295 return -EFAULT; 296 } else { 297 memset(&set_buffer, 0, sizeof(set_buffer)); 298 printk_once(KERN_WARNING "%s calls setitimer() with new_value NULL pointer." 299 " Misfeature support will be removed\n", 300 current->comm); 301 } 302 303 error = do_setitimer(which, &set_buffer, ovalue ? &get_buffer : NULL); 304 if (error || !ovalue) 305 return error; 306 307 if (copy_to_user(ovalue, &get_buffer, sizeof(get_buffer))) 308 return -EFAULT; 309 return 0; 310 } 311 312 #ifdef CONFIG_COMPAT 313 COMPAT_SYSCALL_DEFINE3(setitimer, int, which, 314 struct compat_itimerval __user *, in, 315 struct compat_itimerval __user *, out) 316 { 317 struct itimerval kin, kout; 318 int error; 319 320 if (in) { 321 if (get_compat_itimerval(&kin, in)) 322 return -EFAULT; 323 } else { 324 memset(&kin, 0, sizeof(kin)); 325 } 326 327 error = do_setitimer(which, &kin, out ? &kout : NULL); 328 if (error || !out) 329 return error; 330 if (put_compat_itimerval(out, &kout)) 331 return -EFAULT; 332 return 0; 333 } 334 #endif 335