kernel/os/dtrace_subr.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2009 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  * Copyright 2016 Joyent, Inc.
  26  */
  27
  28 #include <sys/dtrace.h>
  29 #include <sys/cmn_err.h>
  30 #include <sys/tnf.h>
  31 #include <sys/atomic.h>
  32 #include <sys/prsystm.h>
  33 #include <sys/modctl.h>
  34 #include <sys/aio_impl.h>
  35
  36
  37 void (*dtrace_cpu_init)(processorid_t);
  38 void (*dtrace_modload)(struct modctl *);
  39 void (*dtrace_modunload)(struct modctl *);
  40 void (*dtrace_helpers_cleanup)(proc_t *);
  41 void (*dtrace_helpers_fork)(proc_t *, proc_t *);
  42 void (*dtrace_cpustart_init)(void);
  43 void (*dtrace_cpustart_fini)(void);
  44 void (*dtrace_cpc_fire)(uint64_t);
  45 void (*dtrace_closef)(void);
  46
  47 void (*dtrace_debugger_init)(void);
  48 void (*dtrace_debugger_fini)(void);
  49
  50 dtrace_vtime_state_t dtrace_vtime_active = 0;
  51 dtrace_cacheid_t dtrace_predcache_id = DTRACE_CACHEIDNONE + 1;
  52
  53 /*
  54  * dtrace_cpc_in_use usage statement: this global variable is used by the cpc
  55  * hardware overflow interrupt handler and the kernel cpc framework to check
  56  * whether or not the DTrace cpc provider is currently in use. The variable is
  57  * set before counters are enabled with the first enabling and cleared when
  58  * the last enabling is disabled. Its value at any given time indicates the
  59  * number of active dcpc based enablings. The global 'kcpc_cpuctx_lock' rwlock
  60  * is held during initial setting to protect races between kcpc_open() and the
  61  * first enabling. The locking provided by the DTrace subsystem, the kernel
  62  * cpc framework and the cpu management framework protect consumers from race
  63  * conditions on enabling and disabling probes.
  64  */
  65 uint32_t dtrace_cpc_in_use = 0;
  66
  67 typedef struct dtrace_hrestime {
  68         lock_t          dthr_lock;              /* lock for this element */
  69         timestruc_t     dthr_hrestime;          /* hrestime value */
  70         int64_t         dthr_adj;               /* hrestime_adj value */
  71         hrtime_t        dthr_hrtime;            /* hrtime value */
  72 } dtrace_hrestime_t;
  73
  74 static dtrace_hrestime_t dtrace_hrestime[2];
  75
  76 /*
  77  * Making available adjustable high-resolution time in DTrace is regrettably
  78  * more complicated than one might think it should be.  The problem is that
  79  * the variables related to adjusted high-resolution time (hrestime,
  80  * hrestime_adj and friends) are adjusted under hres_lock -- and this lock may
  81  * be held when we enter probe context.  One might think that we could address
  82  * this by having a single snapshot copy that is stored under a different lock
  83  * from hres_tick(), using the snapshot iff hres_lock is locked in probe
  84  * context.  Unfortunately, this too won't work:  because hres_lock is grabbed
  85  * in more than just hres_tick() context, we could enter probe context
  86  * concurrently on two different CPUs with both locks (hres_lock and the
  87  * snapshot lock) held.  As this implies, the fundamental problem is that we
  88  * need to have access to a snapshot of these variables that we _know_ will
  89  * not be locked in probe context.  To effect this, we have two snapshots
  90  * protected by two different locks, and we mandate that these snapshots are
  91  * recorded in succession by a single thread calling dtrace_hres_tick().  (We
  92  * assure this by calling it out of the same CY_HIGH_LEVEL cyclic that calls
  93  * hres_tick().)  A single thread can't be in two places at once:  one of the
  94  * snapshot locks is guaranteed to be unheld at all times.  The
  95  * dtrace_gethrestime() algorithm is thus to check first one snapshot and then
  96  * the other to find the unlocked snapshot.
  97  */
  98 void
  99 dtrace_hres_tick(void)
 100 {
 101         int i;
 102         ushort_t spl;
 103
 104         for (i = 0; i < 2; i++) {
 105                 dtrace_hrestime_t tmp;
 106
 107                 spl = hr_clock_lock();
 108                 tmp.dthr_hrestime = hrestime;
 109                 tmp.dthr_adj = hrestime_adj;
 110                 tmp.dthr_hrtime = dtrace_gethrtime();
 111                 hr_clock_unlock(spl);
 112
 113                 lock_set(&dtrace_hrestime[i].dthr_lock);
 114                 dtrace_hrestime[i].dthr_hrestime = tmp.dthr_hrestime;
 115                 dtrace_hrestime[i].dthr_adj = tmp.dthr_adj;
 116                 dtrace_hrestime[i].dthr_hrtime = tmp.dthr_hrtime;
 117                 dtrace_membar_producer();
 118
 119                 /*
 120                  * To allow for lock-free examination of this lock, we use
 121                  * the same trick that is used hres_lock; for more details,
 122                  * see the description of this technique in sun4u/sys/clock.h.
 123                  */
 124                 dtrace_hrestime[i].dthr_lock++;
 125         }
 126 }
 127
 128 hrtime_t
 129 dtrace_gethrestime(void)
 130 {
 131         dtrace_hrestime_t snap;
 132         hrtime_t now;
 133         int i = 0, adj, nslt;
 134
 135         for (;;) {
 136                 snap.dthr_lock = dtrace_hrestime[i].dthr_lock;
 137                 dtrace_membar_consumer();
 138                 snap.dthr_hrestime = dtrace_hrestime[i].dthr_hrestime;
 139                 snap.dthr_hrtime = dtrace_hrestime[i].dthr_hrtime;
 140                 snap.dthr_adj = dtrace_hrestime[i].dthr_adj;
 141                 dtrace_membar_consumer();
 142
 143                 if ((snap.dthr_lock & ~1) == dtrace_hrestime[i].dthr_lock)
 144                         break;
 145
 146                 /*
 147                  * If we're here, the lock was either locked, or it
 148                  * transitioned while we were taking the snapshot.  Either
 149                  * way, we're going to try the other dtrace_hrestime element;
 150                  * we know that it isn't possible for both to be locked
 151                  * simultaneously, so we will ultimately get a good snapshot.
 152                  */
 153                 i ^= 1;
 154         }
 155
 156         /*
 157          * We have a good snapshot.  Now perform any necessary adjustments.
 158          */
 159         nslt = dtrace_gethrtime() - snap.dthr_hrtime;
 160         ASSERT(nslt >= 0);
 161
 162         now = ((hrtime_t)snap.dthr_hrestime.tv_sec * (hrtime_t)NANOSEC) +
 163             snap.dthr_hrestime.tv_nsec;
 164
 165         if (snap.dthr_adj != 0) {
 166                 if (snap.dthr_adj > 0) {
 167                         adj = (nslt >> adj_shift);
 168                         if (adj > snap.dthr_adj)
 169                                 adj = (int)snap.dthr_adj;
 170                 } else {
 171                         adj = -(nslt >> adj_shift);
 172                         if (adj < snap.dthr_adj)
 173                                 adj = (int)snap.dthr_adj;
 174                 }
 175                 now += adj;
 176         }
 177
 178         return (now);
 179 }
 180
 181 void
 182 dtrace_vtime_enable(void)
 183 {
 184         dtrace_vtime_state_t state, nstate;
 185
 186         do {
 187                 state = dtrace_vtime_active;
 188
 189                 switch (state) {
 190                 case DTRACE_VTIME_INACTIVE:
 191                         nstate = DTRACE_VTIME_ACTIVE;
 192                         break;
 193
 194                 case DTRACE_VTIME_INACTIVE_TNF:
 195                         nstate = DTRACE_VTIME_ACTIVE_TNF;
 196                         break;
 197
 198                 case DTRACE_VTIME_ACTIVE:
 199                 case DTRACE_VTIME_ACTIVE_TNF:
 200                         panic("DTrace virtual time already enabled");
 201                         /*NOTREACHED*/
 202                 }
 203
 204         } while (atomic_cas_32((uint32_t *)&dtrace_vtime_active,
 205             state, nstate) != state);
 206 }
 207
 208 void
 209 dtrace_vtime_disable(void)
 210 {
 211         dtrace_vtime_state_t state, nstate;
 212
 213         do {
 214                 state = dtrace_vtime_active;
 215
 216                 switch (state) {
 217                 case DTRACE_VTIME_ACTIVE:
 218                         nstate = DTRACE_VTIME_INACTIVE;
 219                         break;
 220
 221                 case DTRACE_VTIME_ACTIVE_TNF:
 222                         nstate = DTRACE_VTIME_INACTIVE_TNF;
 223                         break;
 224
 225                 case DTRACE_VTIME_INACTIVE:
 226                 case DTRACE_VTIME_INACTIVE_TNF:
 227                         panic("DTrace virtual time already disabled");
 228                         /*NOTREACHED*/
 229                 }
 230
 231         } while (atomic_cas_32((uint32_t *)&dtrace_vtime_active,
 232             state, nstate) != state);
 233 }
 234
 235 void
 236 dtrace_vtime_enable_tnf(void)
 237 {
 238         dtrace_vtime_state_t state, nstate;
 239
 240         do {
 241                 state = dtrace_vtime_active;
 242
 243                 switch (state) {
 244                 case DTRACE_VTIME_ACTIVE:
 245                         nstate = DTRACE_VTIME_ACTIVE_TNF;
 246                         break;
 247
 248                 case DTRACE_VTIME_INACTIVE:
 249                         nstate = DTRACE_VTIME_INACTIVE_TNF;
 250                         break;
 251
 252                 case DTRACE_VTIME_ACTIVE_TNF:
 253                 case DTRACE_VTIME_INACTIVE_TNF:
 254                         panic("TNF already active");
 255                         /*NOTREACHED*/
 256                 }
 257
 258         } while (atomic_cas_32((uint32_t *)&dtrace_vtime_active,
 259             state, nstate) != state);
 260 }
 261
 262 void
 263 dtrace_vtime_disable_tnf(void)
 264 {
 265         dtrace_vtime_state_t state, nstate;
 266
 267         do {
 268                 state = dtrace_vtime_active;
 269
 270                 switch (state) {
 271                 case DTRACE_VTIME_ACTIVE_TNF:
 272                         nstate = DTRACE_VTIME_ACTIVE;
 273                         break;
 274
 275                 case DTRACE_VTIME_INACTIVE_TNF:
 276                         nstate = DTRACE_VTIME_INACTIVE;
 277                         break;
 278
 279                 case DTRACE_VTIME_ACTIVE:
 280                 case DTRACE_VTIME_INACTIVE:
 281                         panic("TNF already inactive");
 282                         /*NOTREACHED*/
 283                 }
 284
 285         } while (atomic_cas_32((uint32_t *)&dtrace_vtime_active,
 286             state, nstate) != state);
 287 }
 288
 289 void
 290 dtrace_vtime_switch(kthread_t *next)
 291 {
 292         dtrace_icookie_t cookie;
 293         hrtime_t ts;
 294
 295         if (tnf_tracing_active) {
 296                 tnf_thread_switch(next);
 297
 298                 if (dtrace_vtime_active == DTRACE_VTIME_INACTIVE_TNF)
 299                         return;
 300         }
 301
 302         cookie = dtrace_interrupt_disable();
 303         ts = dtrace_gethrtime();
 304
 305         if (curthread->t_dtrace_start != 0) {
 306                 curthread->t_dtrace_vtime += ts - curthread->t_dtrace_start;
 307                 curthread->t_dtrace_start = 0;
 308         }
 309
 310         next->t_dtrace_start = ts;
 311
 312         dtrace_interrupt_enable(cookie);
 313 }
 314
 315 void (*dtrace_fasttrap_fork_ptr)(proc_t *, proc_t *);
 316 void (*dtrace_fasttrap_exec_ptr)(proc_t *);
 317 void (*dtrace_fasttrap_exit_ptr)(proc_t *);
 318
 319 /*
 320  * This function is called by cfork() in the event that it appears that
 321  * there may be dtrace tracepoints active in the parent process's address
 322  * space. This first confirms the existence of dtrace tracepoints in the
 323  * parent process and calls into the fasttrap module to remove the
 324  * corresponding tracepoints from the child. By knowing that there are
 325  * existing tracepoints, and ensuring they can't be removed, we can rely
 326  * on the fasttrap module remaining loaded.
 327  */
 328 void
 329 dtrace_fasttrap_fork(proc_t *p, proc_t *cp)
 330 {
 331         ASSERT(p->p_proc_flag & P_PR_LOCK);
 332         ASSERT(p->p_dtrace_count > 0);
 333         ASSERT(dtrace_fasttrap_fork_ptr != NULL);
 334
 335         dtrace_fasttrap_fork_ptr(p, cp);
 336 }