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 2010 Sun Microsystems, Inc. All rights reserved.
24 * Use is subject to license terms.
25 */
26
27 /*
28 * DTrace Process Control
29 *
30 * This file provides a set of routines that permit libdtrace and its clients
31 * to create and grab process handles using libproc, and to share these handles
32 * between library mechanisms that need libproc access, such as ustack(), and
33 * client mechanisms that need libproc access, such as dtrace(1M) -c and -p.
34 * The library provides several mechanisms in the libproc control layer:
35 *
36 * Reference Counting: The library code and client code can independently grab
37 * the same process handles without interfering with one another. Only when
38 * the reference count drops to zero and the handle is not being cached (see
39 * below for more information on caching) will Prelease() be called on it.
40 *
41 * Handle Caching: If a handle is grabbed PGRAB_RDONLY (e.g. by ustack()) and
42 * the reference count drops to zero, the handle is not immediately released.
43 * Instead, libproc handles are maintained on dph_lrulist in order from most-
44 * recently accessed to least-recently accessed. Idle handles are maintained
45 * until a pre-defined LRU cache limit is exceeded, permitting repeated calls
46 * to ustack() to avoid the overhead of releasing and re-grabbing processes.
47 *
48 * Process Control: For processes that are grabbed for control (~PGRAB_RDONLY)
49 * or created by dt_proc_create(), a control thread is created to provide
50 * callbacks on process exit and symbol table caching on dlopen()s.
51 *
52 * MT-Safety: Libproc is not MT-Safe, so dt_proc_lock() and dt_proc_unlock()
53 * are provided to synchronize access to the libproc handle between libdtrace
54 * code and client code and the control thread's use of the ps_prochandle.
55 *
56 * NOTE: MT-Safety is NOT provided for libdtrace itself, or for use of the
57 * dtrace_proc_grab/dtrace_proc_create mechanisms. Like all exported libdtrace
58 * calls, these are assumed to be MT-Unsafe. MT-Safety is ONLY provided for
59 * synchronization between libdtrace control threads and the client thread.
60 *
61 * The ps_prochandles themselves are maintained along with a dt_proc_t struct
62 * in a hash table indexed by PID. This provides basic locking and reference
63 * counting. The dt_proc_t is also maintained in LRU order on dph_lrulist.
64 * The dph_lrucnt and dph_lrulim count the number of cacheable processes and
65 * the current limit on the number of actively cached entries.
66 *
67 * The control thread for a process establishes breakpoints at the rtld_db
68 * locations of interest, updates mappings and symbol tables at these points,
69 * and handles exec and fork (by always following the parent). The control
70 * thread automatically exits when the process dies or control is lost.
71 *
72 * A simple notification mechanism is provided for libdtrace clients using
73 * dtrace_handle_proc() for notification of PS_UNDEAD or PS_LOST events. If
74 * such an event occurs, the dt_proc_t itself is enqueued on a notification
75 * list and the control thread broadcasts to dph_cv. dtrace_sleep() will wake
76 * up using this condition and will then call the client handler as necessary.
77 */
78
79 #include <sys/wait.h>
80 #include <sys/lwp.h>
81 #include <strings.h>
82 #include <signal.h>
83 #include <assert.h>
84 #include <errno.h>
85
86 #include <dt_proc.h>
87 #include <dt_pid.h>
88 #include <dt_impl.h>
89
90 #define IS_SYS_EXEC(w) (w == SYS_execve)
91 #define IS_SYS_FORK(w) (w == SYS_vfork || w == SYS_forksys)
92
93 static dt_bkpt_t *
dt_proc_bpcreate(dt_proc_t * dpr,uintptr_t addr,dt_bkpt_f * func,void * data)94 dt_proc_bpcreate(dt_proc_t *dpr, uintptr_t addr, dt_bkpt_f *func, void *data)
95 {
96 struct ps_prochandle *P = dpr->dpr_proc;
97 dt_bkpt_t *dbp;
98
99 assert(MUTEX_HELD(&dpr->dpr_lock));
100
101 if ((dbp = dt_zalloc(dpr->dpr_hdl, sizeof (dt_bkpt_t))) != NULL) {
102 dbp->dbp_func = func;
103 dbp->dbp_data = data;
104 dbp->dbp_addr = addr;
105
106 if (Psetbkpt(P, dbp->dbp_addr, &dbp->dbp_instr) == 0)
107 dbp->dbp_active = B_TRUE;
108
109 dt_list_append(&dpr->dpr_bps, dbp);
110 }
111
112 return (dbp);
113 }
114
115 static void
dt_proc_bpdestroy(dt_proc_t * dpr,int delbkpts)116 dt_proc_bpdestroy(dt_proc_t *dpr, int delbkpts)
117 {
118 int state = Pstate(dpr->dpr_proc);
119 dt_bkpt_t *dbp, *nbp;
120
121 assert(MUTEX_HELD(&dpr->dpr_lock));
122
123 for (dbp = dt_list_next(&dpr->dpr_bps); dbp != NULL; dbp = nbp) {
124 if (delbkpts && dbp->dbp_active &&
125 state != PS_LOST && state != PS_UNDEAD) {
126 (void) Pdelbkpt(dpr->dpr_proc,
127 dbp->dbp_addr, dbp->dbp_instr);
128 }
129 nbp = dt_list_next(dbp);
130 dt_list_delete(&dpr->dpr_bps, dbp);
131 dt_free(dpr->dpr_hdl, dbp);
132 }
133 }
134
135 static void
dt_proc_bpmatch(dtrace_hdl_t * dtp,dt_proc_t * dpr)136 dt_proc_bpmatch(dtrace_hdl_t *dtp, dt_proc_t *dpr)
137 {
138 const lwpstatus_t *psp = &Pstatus(dpr->dpr_proc)->pr_lwp;
139 dt_bkpt_t *dbp;
140
141 assert(MUTEX_HELD(&dpr->dpr_lock));
142
143 for (dbp = dt_list_next(&dpr->dpr_bps);
144 dbp != NULL; dbp = dt_list_next(dbp)) {
145 if (psp->pr_reg[R_PC] == dbp->dbp_addr)
146 break;
147 }
148
149 if (dbp == NULL) {
150 dt_dprintf("pid %d: spurious breakpoint wakeup for %lx\n",
151 (int)dpr->dpr_pid, (ulong_t)psp->pr_reg[R_PC]);
152 return;
153 }
154
155 dt_dprintf("pid %d: hit breakpoint at %lx (%lu)\n",
156 (int)dpr->dpr_pid, (ulong_t)dbp->dbp_addr, ++dbp->dbp_hits);
157
158 dbp->dbp_func(dtp, dpr, dbp->dbp_data);
159 (void) Pxecbkpt(dpr->dpr_proc, dbp->dbp_instr);
160 }
161
162 static void
dt_proc_bpenable(dt_proc_t * dpr)163 dt_proc_bpenable(dt_proc_t *dpr)
164 {
165 dt_bkpt_t *dbp;
166
167 assert(MUTEX_HELD(&dpr->dpr_lock));
168
169 for (dbp = dt_list_next(&dpr->dpr_bps);
170 dbp != NULL; dbp = dt_list_next(dbp)) {
171 if (!dbp->dbp_active && Psetbkpt(dpr->dpr_proc,
172 dbp->dbp_addr, &dbp->dbp_instr) == 0)
173 dbp->dbp_active = B_TRUE;
174 }
175
176 dt_dprintf("breakpoints enabled\n");
177 }
178
179 static void
dt_proc_bpdisable(dt_proc_t * dpr)180 dt_proc_bpdisable(dt_proc_t *dpr)
181 {
182 dt_bkpt_t *dbp;
183
184 assert(MUTEX_HELD(&dpr->dpr_lock));
185
186 for (dbp = dt_list_next(&dpr->dpr_bps);
187 dbp != NULL; dbp = dt_list_next(dbp)) {
188 if (dbp->dbp_active && Pdelbkpt(dpr->dpr_proc,
189 dbp->dbp_addr, dbp->dbp_instr) == 0)
190 dbp->dbp_active = B_FALSE;
191 }
192
193 dt_dprintf("breakpoints disabled\n");
194 }
195
196 static void
dt_proc_notify(dtrace_hdl_t * dtp,dt_proc_hash_t * dph,dt_proc_t * dpr,const char * msg)197 dt_proc_notify(dtrace_hdl_t *dtp, dt_proc_hash_t *dph, dt_proc_t *dpr,
198 const char *msg)
199 {
200 dt_proc_notify_t *dprn = dt_alloc(dtp, sizeof (dt_proc_notify_t));
201
202 if (dprn == NULL) {
203 dt_dprintf("failed to allocate notification for %d %s\n",
204 (int)dpr->dpr_pid, msg);
205 } else {
206 dprn->dprn_dpr = dpr;
207 if (msg == NULL)
208 dprn->dprn_errmsg[0] = '\0';
209 else
210 (void) strlcpy(dprn->dprn_errmsg, msg,
211 sizeof (dprn->dprn_errmsg));
212
213 (void) pthread_mutex_lock(&dph->dph_lock);
214
215 dprn->dprn_next = dph->dph_notify;
216 dph->dph_notify = dprn;
217
218 (void) pthread_cond_broadcast(&dph->dph_cv);
219 (void) pthread_mutex_unlock(&dph->dph_lock);
220 }
221 }
222
223 /*
224 * Check to see if the control thread was requested to stop when the victim
225 * process reached a particular event (why) rather than continuing the victim.
226 * If 'why' is set in the stop mask, we wait on dpr_cv for dt_proc_continue().
227 * If 'why' is not set, this function returns immediately and does nothing.
228 */
229 static void
dt_proc_stop(dt_proc_t * dpr,uint8_t why)230 dt_proc_stop(dt_proc_t *dpr, uint8_t why)
231 {
232 assert(MUTEX_HELD(&dpr->dpr_lock));
233 assert(why != DT_PROC_STOP_IDLE);
234
235 if (dpr->dpr_stop & why) {
236 dpr->dpr_stop |= DT_PROC_STOP_IDLE;
237 dpr->dpr_stop &= ~why;
238
239 (void) pthread_cond_broadcast(&dpr->dpr_cv);
240
241 /*
242 * We disable breakpoints while stopped to preserve the
243 * integrity of the program text for both our own disassembly
244 * and that of the kernel.
245 */
246 dt_proc_bpdisable(dpr);
247
248 while (dpr->dpr_stop & DT_PROC_STOP_IDLE)
249 (void) pthread_cond_wait(&dpr->dpr_cv, &dpr->dpr_lock);
250
251 dt_proc_bpenable(dpr);
252 }
253 }
254
255 /*ARGSUSED*/
256 static void
dt_proc_bpmain(dtrace_hdl_t * dtp,dt_proc_t * dpr,const char * fname)257 dt_proc_bpmain(dtrace_hdl_t *dtp, dt_proc_t *dpr, const char *fname)
258 {
259 dt_dprintf("pid %d: breakpoint at %s()\n", (int)dpr->dpr_pid, fname);
260 dt_proc_stop(dpr, DT_PROC_STOP_MAIN);
261 }
262
263 static void
dt_proc_rdevent(dtrace_hdl_t * dtp,dt_proc_t * dpr,const char * evname)264 dt_proc_rdevent(dtrace_hdl_t *dtp, dt_proc_t *dpr, const char *evname)
265 {
266 rd_event_msg_t rdm;
267 rd_err_e err;
268
269 if ((err = rd_event_getmsg(dpr->dpr_rtld, &rdm)) != RD_OK) {
270 dt_dprintf("pid %d: failed to get %s event message: %s\n",
271 (int)dpr->dpr_pid, evname, rd_errstr(err));
272 return;
273 }
274
275 dt_dprintf("pid %d: rtld event %s type=%d state %d\n",
276 (int)dpr->dpr_pid, evname, rdm.type, rdm.u.state);
277
278 switch (rdm.type) {
279 case RD_DLACTIVITY:
280 if (rdm.u.state != RD_CONSISTENT)
281 break;
282
283 Pupdate_syms(dpr->dpr_proc);
284 if (dt_pid_create_probes_module(dtp, dpr) != 0)
285 dt_proc_notify(dtp, dtp->dt_procs, dpr,
286 dpr->dpr_errmsg);
287
288 break;
289 case RD_PREINIT:
290 Pupdate_syms(dpr->dpr_proc);
291 dt_proc_stop(dpr, DT_PROC_STOP_PREINIT);
292 break;
293 case RD_POSTINIT:
294 Pupdate_syms(dpr->dpr_proc);
295 dt_proc_stop(dpr, DT_PROC_STOP_POSTINIT);
296 break;
297 }
298 }
299
300 static void
dt_proc_rdwatch(dt_proc_t * dpr,rd_event_e event,const char * evname)301 dt_proc_rdwatch(dt_proc_t *dpr, rd_event_e event, const char *evname)
302 {
303 rd_notify_t rdn;
304 rd_err_e err;
305
306 if ((err = rd_event_addr(dpr->dpr_rtld, event, &rdn)) != RD_OK) {
307 dt_dprintf("pid %d: failed to get event address for %s: %s\n",
308 (int)dpr->dpr_pid, evname, rd_errstr(err));
309 return;
310 }
311
312 if (rdn.type != RD_NOTIFY_BPT) {
313 dt_dprintf("pid %d: event %s has unexpected type %d\n",
314 (int)dpr->dpr_pid, evname, rdn.type);
315 return;
316 }
317
318 (void) dt_proc_bpcreate(dpr, rdn.u.bptaddr,
319 (dt_bkpt_f *)dt_proc_rdevent, (void *)evname);
320 }
321
322 /*
323 * Common code for enabling events associated with the run-time linker after
324 * attaching to a process or after a victim process completes an exec(2).
325 */
326 static void
dt_proc_attach(dt_proc_t * dpr,int exec)327 dt_proc_attach(dt_proc_t *dpr, int exec)
328 {
329 const pstatus_t *psp = Pstatus(dpr->dpr_proc);
330 rd_err_e err;
331 GElf_Sym sym;
332
333 assert(MUTEX_HELD(&dpr->dpr_lock));
334
335 if (exec) {
336 if (psp->pr_lwp.pr_errno != 0)
337 return; /* exec failed: nothing needs to be done */
338
339 dt_proc_bpdestroy(dpr, B_FALSE);
340 Preset_maps(dpr->dpr_proc);
341 }
342
343 if ((dpr->dpr_rtld = Prd_agent(dpr->dpr_proc)) != NULL &&
344 (err = rd_event_enable(dpr->dpr_rtld, B_TRUE)) == RD_OK) {
345 dt_proc_rdwatch(dpr, RD_PREINIT, "RD_PREINIT");
346 dt_proc_rdwatch(dpr, RD_POSTINIT, "RD_POSTINIT");
347 dt_proc_rdwatch(dpr, RD_DLACTIVITY, "RD_DLACTIVITY");
348 } else {
349 dt_dprintf("pid %d: failed to enable rtld events: %s\n",
350 (int)dpr->dpr_pid, dpr->dpr_rtld ? rd_errstr(err) :
351 "rtld_db agent initialization failed");
352 }
353
354 Pupdate_maps(dpr->dpr_proc);
355
356 if (Pxlookup_by_name(dpr->dpr_proc, LM_ID_BASE,
357 "a.out", "main", &sym, NULL) == 0) {
358 (void) dt_proc_bpcreate(dpr, (uintptr_t)sym.st_value,
359 (dt_bkpt_f *)dt_proc_bpmain, "a.out`main");
360 } else {
361 dt_dprintf("pid %d: failed to find a.out`main: %s\n",
362 (int)dpr->dpr_pid, strerror(errno));
363 }
364 }
365
366 /*
367 * Wait for a stopped process to be set running again by some other debugger.
368 * This is typically not required by /proc-based debuggers, since the usual
369 * model is that one debugger controls one victim. But DTrace, as usual, has
370 * its own needs: the stop() action assumes that prun(1) or some other tool
371 * will be applied to resume the victim process. This could be solved by
372 * adding a PCWRUN directive to /proc, but that seems like overkill unless
373 * other debuggers end up needing this functionality, so we implement a cheap
374 * equivalent to PCWRUN using the set of existing kernel mechanisms.
375 *
376 * Our intent is really not just to wait for the victim to run, but rather to
377 * wait for it to run and then stop again for a reason other than the current
378 * PR_REQUESTED stop. Since PCWSTOP/Pstopstatus() can be applied repeatedly
379 * to a stopped process and will return the same result without affecting the
380 * victim, we can just perform these operations repeatedly until Pstate()
381 * changes, the representative LWP ID changes, or the stop timestamp advances.
382 * dt_proc_control() will then rediscover the new state and continue as usual.
383 * When the process is still stopped in the same exact state, we sleep for a
384 * brief interval before waiting again so as not to spin consuming CPU cycles.
385 */
386 static void
dt_proc_waitrun(dt_proc_t * dpr)387 dt_proc_waitrun(dt_proc_t *dpr)
388 {
389 struct ps_prochandle *P = dpr->dpr_proc;
390 const lwpstatus_t *psp = &Pstatus(P)->pr_lwp;
391
392 int krflag = psp->pr_flags & (PR_KLC | PR_RLC);
393 timestruc_t tstamp = psp->pr_tstamp;
394 lwpid_t lwpid = psp->pr_lwpid;
395
396 const long wstop = PCWSTOP;
397 int pfd = Pctlfd(P);
398
399 assert(MUTEX_HELD(&dpr->dpr_lock));
400 assert(psp->pr_flags & PR_STOPPED);
401 assert(Pstate(P) == PS_STOP);
402
403 /*
404 * While we are waiting for the victim to run, clear PR_KLC and PR_RLC
405 * so that if the libdtrace client is killed, the victim stays stopped.
406 * dt_proc_destroy() will also observe this and perform PRELEASE_HANG.
407 */
408 (void) Punsetflags(P, krflag);
409 Psync(P);
410
411 (void) pthread_mutex_unlock(&dpr->dpr_lock);
412
413 while (!dpr->dpr_quit) {
414 if (write(pfd, &wstop, sizeof (wstop)) == -1 && errno == EINTR)
415 continue; /* check dpr_quit and continue waiting */
416
417 (void) pthread_mutex_lock(&dpr->dpr_lock);
418 (void) Pstopstatus(P, PCNULL, 0);
419 psp = &Pstatus(P)->pr_lwp;
420
421 /*
422 * If we've reached a new state, found a new representative, or
423 * the stop timestamp has changed, restore PR_KLC/PR_RLC to its
424 * original setting and then return with dpr_lock held.
425 */
426 if (Pstate(P) != PS_STOP || psp->pr_lwpid != lwpid ||
427 bcmp(&psp->pr_tstamp, &tstamp, sizeof (tstamp)) != 0) {
428 (void) Psetflags(P, krflag);
429 Psync(P);
430 return;
431 }
432
433 (void) pthread_mutex_unlock(&dpr->dpr_lock);
434 (void) poll(NULL, 0, MILLISEC / 2);
435 }
436
437 (void) pthread_mutex_lock(&dpr->dpr_lock);
438 }
439
440 typedef struct dt_proc_control_data {
441 dtrace_hdl_t *dpcd_hdl; /* DTrace handle */
442 dt_proc_t *dpcd_proc; /* proccess to control */
443 } dt_proc_control_data_t;
444
445 /*
446 * Main loop for all victim process control threads. We initialize all the
447 * appropriate /proc control mechanisms, and then enter a loop waiting for
448 * the process to stop on an event or die. We process any events by calling
449 * appropriate subroutines, and exit when the victim dies or we lose control.
450 *
451 * The control thread synchronizes the use of dpr_proc with other libdtrace
452 * threads using dpr_lock. We hold the lock for all of our operations except
453 * waiting while the process is running: this is accomplished by writing a
454 * PCWSTOP directive directly to the underlying /proc/<pid>/ctl file. If the
455 * libdtrace client wishes to exit or abort our wait, SIGCANCEL can be used.
456 */
457 static void *
dt_proc_control(void * arg)458 dt_proc_control(void *arg)
459 {
460 dt_proc_control_data_t *datap = arg;
461 dtrace_hdl_t *dtp = datap->dpcd_hdl;
462 dt_proc_t *dpr = datap->dpcd_proc;
463 dt_proc_hash_t *dph = dpr->dpr_hdl->dt_procs;
464 struct ps_prochandle *P = dpr->dpr_proc;
465
466 int pfd = Pctlfd(P);
467 int pid = dpr->dpr_pid;
468
469 const long wstop = PCWSTOP;
470 int notify = B_FALSE;
471
472 /*
473 * We disable the POSIX thread cancellation mechanism so that the
474 * client program using libdtrace can't accidentally cancel our thread.
475 * dt_proc_destroy() uses SIGCANCEL explicitly to simply poke us out
476 * of PCWSTOP with EINTR, at which point we will see dpr_quit and exit.
477 */
478 (void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL);
479
480 /*
481 * Set up the corresponding process for tracing by libdtrace. We want
482 * to be able to catch breakpoints and efficiently single-step over
483 * them, and we need to enable librtld_db to watch libdl activity.
484 */
485 (void) pthread_mutex_lock(&dpr->dpr_lock);
486
487 (void) Punsetflags(P, PR_ASYNC); /* require synchronous mode */
488 (void) Psetflags(P, PR_BPTADJ); /* always adjust eip on x86 */
489 (void) Punsetflags(P, PR_FORK); /* do not inherit on fork */
490
491 (void) Pfault(P, FLTBPT, B_TRUE); /* always trace breakpoints */
492 (void) Pfault(P, FLTTRACE, B_TRUE); /* always trace single-step */
493
494 /*
495 * We must trace exit from exec() system calls so that if the exec is
496 * successful, we can reset our breakpoints and re-initialize libproc.
497 */
498 (void) Psysexit(P, SYS_execve, B_TRUE);
499
500 /*
501 * We must trace entry and exit for fork() system calls in order to
502 * disable our breakpoints temporarily during the fork. We do not set
503 * the PR_FORK flag, so if fork succeeds the child begins executing and
504 * does not inherit any other tracing behaviors or a control thread.
505 */
506 (void) Psysentry(P, SYS_vfork, B_TRUE);
507 (void) Psysexit(P, SYS_vfork, B_TRUE);
508 (void) Psysentry(P, SYS_forksys, B_TRUE);
509 (void) Psysexit(P, SYS_forksys, B_TRUE);
510
511 Psync(P); /* enable all /proc changes */
512 dt_proc_attach(dpr, B_FALSE); /* enable rtld breakpoints */
513
514 /*
515 * If PR_KLC is set, we created the process; otherwise we grabbed it.
516 * Check for an appropriate stop request and wait for dt_proc_continue.
517 */
518 if (Pstatus(P)->pr_flags & PR_KLC)
519 dt_proc_stop(dpr, DT_PROC_STOP_CREATE);
520 else
521 dt_proc_stop(dpr, DT_PROC_STOP_GRAB);
522
523 if (Psetrun(P, 0, 0) == -1) {
524 dt_dprintf("pid %d: failed to set running: %s\n",
525 (int)dpr->dpr_pid, strerror(errno));
526 }
527
528 (void) pthread_mutex_unlock(&dpr->dpr_lock);
529
530 /*
531 * Wait for the process corresponding to this control thread to stop,
532 * process the event, and then set it running again. We want to sleep
533 * with dpr_lock *unheld* so that other parts of libdtrace can use the
534 * ps_prochandle in the meantime (e.g. ustack()). To do this, we write
535 * a PCWSTOP directive directly to the underlying /proc/<pid>/ctl file.
536 * Once the process stops, we wake up, grab dpr_lock, and then call
537 * Pwait() (which will return immediately) and do our processing.
538 */
539 while (!dpr->dpr_quit) {
540 const lwpstatus_t *psp;
541
542 if (write(pfd, &wstop, sizeof (wstop)) == -1 && errno == EINTR)
543 continue; /* check dpr_quit and continue waiting */
544
545 (void) pthread_mutex_lock(&dpr->dpr_lock);
546 pwait_locked:
547 if (Pstopstatus(P, PCNULL, 0) == -1 && errno == EINTR) {
548 (void) pthread_mutex_unlock(&dpr->dpr_lock);
549 continue; /* check dpr_quit and continue waiting */
550 }
551
552 switch (Pstate(P)) {
553 case PS_STOP:
554 psp = &Pstatus(P)->pr_lwp;
555
556 dt_dprintf("pid %d: proc stopped showing %d/%d\n",
557 pid, psp->pr_why, psp->pr_what);
558
559 /*
560 * If the process stops showing PR_REQUESTED, then the
561 * DTrace stop() action was applied to it or another
562 * debugging utility (e.g. pstop(1)) asked it to stop.
563 * In either case, the user's intention is for the
564 * process to remain stopped until another external
565 * mechanism (e.g. prun(1)) is applied. So instead of
566 * setting the process running ourself, we wait for
567 * someone else to do so. Once that happens, we return
568 * to our normal loop waiting for an event of interest.
569 */
570 if (psp->pr_why == PR_REQUESTED) {
571 dt_proc_waitrun(dpr);
572 (void) pthread_mutex_unlock(&dpr->dpr_lock);
573 continue;
574 }
575
576 /*
577 * If the process stops showing one of the events that
578 * we are tracing, perform the appropriate response.
579 * Note that we ignore PR_SUSPENDED, PR_CHECKPOINT, and
580 * PR_JOBCONTROL by design: if one of these conditions
581 * occurs, we will fall through to Psetrun() but the
582 * process will remain stopped in the kernel by the
583 * corresponding mechanism (e.g. job control stop).
584 */
585 if (psp->pr_why == PR_FAULTED && psp->pr_what == FLTBPT)
586 dt_proc_bpmatch(dtp, dpr);
587 else if (psp->pr_why == PR_SYSENTRY &&
588 IS_SYS_FORK(psp->pr_what))
589 dt_proc_bpdisable(dpr);
590 else if (psp->pr_why == PR_SYSEXIT &&
591 IS_SYS_FORK(psp->pr_what))
592 dt_proc_bpenable(dpr);
593 else if (psp->pr_why == PR_SYSEXIT &&
594 IS_SYS_EXEC(psp->pr_what))
595 dt_proc_attach(dpr, B_TRUE);
596 break;
597
598 case PS_LOST:
599 if (Preopen(P) == 0)
600 goto pwait_locked;
601
602 dt_dprintf("pid %d: proc lost: %s\n",
603 pid, strerror(errno));
604
605 dpr->dpr_quit = B_TRUE;
606 notify = B_TRUE;
607 break;
608
609 case PS_UNDEAD:
610 dt_dprintf("pid %d: proc died\n", pid);
611 dpr->dpr_quit = B_TRUE;
612 notify = B_TRUE;
613 break;
614 }
615
616 if (Pstate(P) != PS_UNDEAD && Psetrun(P, 0, 0) == -1) {
617 dt_dprintf("pid %d: failed to set running: %s\n",
618 (int)dpr->dpr_pid, strerror(errno));
619 }
620
621 (void) pthread_mutex_unlock(&dpr->dpr_lock);
622 }
623
624 /*
625 * If the control thread detected PS_UNDEAD or PS_LOST, then enqueue
626 * the dt_proc_t structure on the dt_proc_hash_t notification list.
627 */
628 if (notify)
629 dt_proc_notify(dtp, dph, dpr, NULL);
630
631 /*
632 * Destroy and remove any remaining breakpoints, set dpr_done and clear
633 * dpr_tid to indicate the control thread has exited, and notify any
634 * waiting thread in dt_proc_destroy() that we have succesfully exited.
635 */
636 (void) pthread_mutex_lock(&dpr->dpr_lock);
637
638 dt_proc_bpdestroy(dpr, B_TRUE);
639 dpr->dpr_done = B_TRUE;
640 dpr->dpr_tid = 0;
641
642 (void) pthread_cond_broadcast(&dpr->dpr_cv);
643 (void) pthread_mutex_unlock(&dpr->dpr_lock);
644
645 return (NULL);
646 }
647
648 /*PRINTFLIKE3*/
649 static struct ps_prochandle *
dt_proc_error(dtrace_hdl_t * dtp,dt_proc_t * dpr,const char * format,...)650 dt_proc_error(dtrace_hdl_t *dtp, dt_proc_t *dpr, const char *format, ...)
651 {
652 va_list ap;
653
654 va_start(ap, format);
655 dt_set_errmsg(dtp, NULL, NULL, NULL, 0, format, ap);
656 va_end(ap);
657
658 if (dpr->dpr_proc != NULL)
659 Prelease(dpr->dpr_proc, 0);
660
661 dt_free(dtp, dpr);
662 (void) dt_set_errno(dtp, EDT_COMPILER);
663 return (NULL);
664 }
665
666 dt_proc_t *
dt_proc_lookup(dtrace_hdl_t * dtp,struct ps_prochandle * P,int remove)667 dt_proc_lookup(dtrace_hdl_t *dtp, struct ps_prochandle *P, int remove)
668 {
669 dt_proc_hash_t *dph = dtp->dt_procs;
670 pid_t pid = Pstatus(P)->pr_pid;
671 dt_proc_t *dpr, **dpp = &dph->dph_hash[pid & (dph->dph_hashlen - 1)];
672
673 for (dpr = *dpp; dpr != NULL; dpr = dpr->dpr_hash) {
674 if (dpr->dpr_pid == pid)
675 break;
676 else
677 dpp = &dpr->dpr_hash;
678 }
679
680 assert(dpr != NULL);
681 assert(dpr->dpr_proc == P);
682
683 if (remove)
684 *dpp = dpr->dpr_hash; /* remove from pid hash chain */
685
686 return (dpr);
687 }
688
689 static void
dt_proc_destroy(dtrace_hdl_t * dtp,struct ps_prochandle * P)690 dt_proc_destroy(dtrace_hdl_t *dtp, struct ps_prochandle *P)
691 {
692 dt_proc_t *dpr = dt_proc_lookup(dtp, P, B_FALSE);
693 dt_proc_hash_t *dph = dtp->dt_procs;
694 dt_proc_notify_t *npr, **npp;
695 int rflag;
696
697 assert(dpr != NULL);
698
699 /*
700 * If neither PR_KLC nor PR_RLC is set, then the process is stopped by
701 * an external debugger and we were waiting in dt_proc_waitrun().
702 * Leave the process in this condition using PRELEASE_HANG.
703 */
704 if (!(Pstatus(dpr->dpr_proc)->pr_flags & (PR_KLC | PR_RLC))) {
705 dt_dprintf("abandoning pid %d\n", (int)dpr->dpr_pid);
706 rflag = PRELEASE_HANG;
707 } else if (Pstatus(dpr->dpr_proc)->pr_flags & PR_KLC) {
708 dt_dprintf("killing pid %d\n", (int)dpr->dpr_pid);
709 rflag = PRELEASE_KILL; /* apply kill-on-last-close */
710 } else {
711 dt_dprintf("releasing pid %d\n", (int)dpr->dpr_pid);
712 rflag = 0; /* apply run-on-last-close */
713 }
714
715 if (dpr->dpr_tid) {
716 /*
717 * Set the dpr_quit flag to tell the daemon thread to exit. We
718 * send it a SIGCANCEL to poke it out of PCWSTOP or any other
719 * long-term /proc system call. Our daemon threads have POSIX
720 * cancellation disabled, so EINTR will be the only effect. We
721 * then wait for dpr_done to indicate the thread has exited.
722 *
723 * We can't use pthread_kill() to send SIGCANCEL because the
724 * interface forbids it and we can't use pthread_cancel()
725 * because with cancellation disabled it won't actually
726 * send SIGCANCEL to the target thread, so we use _lwp_kill()
727 * to do the job. This is all built on evil knowledge of
728 * the details of the cancellation mechanism in libc.
729 */
730 (void) pthread_mutex_lock(&dpr->dpr_lock);
731 dpr->dpr_quit = B_TRUE;
732 (void) _lwp_kill(dpr->dpr_tid, SIGCANCEL);
733
734 /*
735 * If the process is currently idling in dt_proc_stop(), re-
736 * enable breakpoints and poke it into running again.
737 */
738 if (dpr->dpr_stop & DT_PROC_STOP_IDLE) {
739 dt_proc_bpenable(dpr);
740 dpr->dpr_stop &= ~DT_PROC_STOP_IDLE;
741 (void) pthread_cond_broadcast(&dpr->dpr_cv);
742 }
743
744 while (!dpr->dpr_done)
745 (void) pthread_cond_wait(&dpr->dpr_cv, &dpr->dpr_lock);
746
747 (void) pthread_mutex_unlock(&dpr->dpr_lock);
748 }
749
750 /*
751 * Before we free the process structure, remove this dt_proc_t from the
752 * lookup hash, and then walk the dt_proc_hash_t's notification list
753 * and remove this dt_proc_t if it is enqueued.
754 */
755 (void) pthread_mutex_lock(&dph->dph_lock);
756 (void) dt_proc_lookup(dtp, P, B_TRUE);
757 npp = &dph->dph_notify;
758
759 while ((npr = *npp) != NULL) {
760 if (npr->dprn_dpr == dpr) {
761 *npp = npr->dprn_next;
762 dt_free(dtp, npr);
763 } else {
764 npp = &npr->dprn_next;
765 }
766 }
767
768 (void) pthread_mutex_unlock(&dph->dph_lock);
769
770 /*
771 * Remove the dt_proc_list from the LRU list, release the underlying
772 * libproc handle, and free our dt_proc_t data structure.
773 */
774 if (dpr->dpr_cacheable) {
775 assert(dph->dph_lrucnt != 0);
776 dph->dph_lrucnt--;
777 }
778
779 dt_list_delete(&dph->dph_lrulist, dpr);
780 Prelease(dpr->dpr_proc, rflag);
781 dt_free(dtp, dpr);
782 }
783
784 static int
dt_proc_create_thread(dtrace_hdl_t * dtp,dt_proc_t * dpr,uint_t stop)785 dt_proc_create_thread(dtrace_hdl_t *dtp, dt_proc_t *dpr, uint_t stop)
786 {
787 dt_proc_control_data_t data;
788 sigset_t nset, oset;
789 pthread_attr_t a;
790 int err;
791
792 (void) pthread_mutex_lock(&dpr->dpr_lock);
793 dpr->dpr_stop |= stop; /* set bit for initial rendezvous */
794
795 (void) pthread_attr_init(&a);
796 (void) pthread_attr_setdetachstate(&a, PTHREAD_CREATE_DETACHED);
797
798 (void) sigfillset(&nset);
799 (void) sigdelset(&nset, SIGABRT); /* unblocked for assert() */
800 (void) sigdelset(&nset, SIGCANCEL); /* see dt_proc_destroy() */
801
802 data.dpcd_hdl = dtp;
803 data.dpcd_proc = dpr;
804
805 (void) pthread_sigmask(SIG_SETMASK, &nset, &oset);
806 err = pthread_create(&dpr->dpr_tid, &a, dt_proc_control, &data);
807 (void) pthread_sigmask(SIG_SETMASK, &oset, NULL);
808
809 /*
810 * If the control thread was created, then wait on dpr_cv for either
811 * dpr_done to be set (the victim died or the control thread failed)
812 * or DT_PROC_STOP_IDLE to be set, indicating that the victim is now
813 * stopped by /proc and the control thread is at the rendezvous event.
814 * On success, we return with the process and control thread stopped:
815 * the caller can then apply dt_proc_continue() to resume both.
816 */
817 if (err == 0) {
818 while (!dpr->dpr_done && !(dpr->dpr_stop & DT_PROC_STOP_IDLE))
819 (void) pthread_cond_wait(&dpr->dpr_cv, &dpr->dpr_lock);
820
821 /*
822 * If dpr_done is set, the control thread aborted before it
823 * reached the rendezvous event. This is either due to PS_LOST
824 * or PS_UNDEAD (i.e. the process died). We try to provide a
825 * small amount of useful information to help figure it out.
826 */
827 if (dpr->dpr_done) {
828 const psinfo_t *prp = Ppsinfo(dpr->dpr_proc);
829 int stat = prp ? prp->pr_wstat : 0;
830 int pid = dpr->dpr_pid;
831
832 if (Pstate(dpr->dpr_proc) == PS_LOST) {
833 (void) dt_proc_error(dpr->dpr_hdl, dpr,
834 "failed to control pid %d: process exec'd "
835 "set-id or unobservable program\n", pid);
836 } else if (WIFSIGNALED(stat)) {
837 (void) dt_proc_error(dpr->dpr_hdl, dpr,
838 "failed to control pid %d: process died "
839 "from signal %d\n", pid, WTERMSIG(stat));
840 } else {
841 (void) dt_proc_error(dpr->dpr_hdl, dpr,
842 "failed to control pid %d: process exited "
843 "with status %d\n", pid, WEXITSTATUS(stat));
844 }
845
846 err = ESRCH; /* cause grab() or create() to fail */
847 }
848 } else {
849 (void) dt_proc_error(dpr->dpr_hdl, dpr,
850 "failed to create control thread for process-id %d: %s\n",
851 (int)dpr->dpr_pid, strerror(err));
852 }
853
854 (void) pthread_mutex_unlock(&dpr->dpr_lock);
855 (void) pthread_attr_destroy(&a);
856
857 return (err);
858 }
859
860 struct ps_prochandle *
dt_proc_create(dtrace_hdl_t * dtp,const char * file,char * const * argv)861 dt_proc_create(dtrace_hdl_t *dtp, const char *file, char *const *argv)
862 {
863 dt_proc_hash_t *dph = dtp->dt_procs;
864 dt_proc_t *dpr;
865 int err;
866
867 if ((dpr = dt_zalloc(dtp, sizeof (dt_proc_t))) == NULL)
868 return (NULL); /* errno is set for us */
869
870 (void) pthread_mutex_init(&dpr->dpr_lock, NULL);
871 (void) pthread_cond_init(&dpr->dpr_cv, NULL);
872
873 if ((dpr->dpr_proc = Pcreate(file, argv, &err, NULL, 0)) == NULL) {
874 return (dt_proc_error(dtp, dpr,
875 "failed to execute %s: %s\n", file, Pcreate_error(err)));
876 }
877
878 dpr->dpr_hdl = dtp;
879 dpr->dpr_pid = Pstatus(dpr->dpr_proc)->pr_pid;
880
881 (void) Punsetflags(dpr->dpr_proc, PR_RLC);
882 (void) Psetflags(dpr->dpr_proc, PR_KLC);
883
884 if (dt_proc_create_thread(dtp, dpr, dtp->dt_prcmode) != 0)
885 return (NULL); /* dt_proc_error() has been called for us */
886
887 dpr->dpr_hash = dph->dph_hash[dpr->dpr_pid & (dph->dph_hashlen - 1)];
888 dph->dph_hash[dpr->dpr_pid & (dph->dph_hashlen - 1)] = dpr;
889 dt_list_prepend(&dph->dph_lrulist, dpr);
890
891 dt_dprintf("created pid %d\n", (int)dpr->dpr_pid);
892 dpr->dpr_refs++;
893
894 return (dpr->dpr_proc);
895 }
896
897 struct ps_prochandle *
dt_proc_grab(dtrace_hdl_t * dtp,pid_t pid,int flags,int nomonitor)898 dt_proc_grab(dtrace_hdl_t *dtp, pid_t pid, int flags, int nomonitor)
899 {
900 dt_proc_hash_t *dph = dtp->dt_procs;
901 uint_t h = pid & (dph->dph_hashlen - 1);
902 dt_proc_t *dpr, *opr;
903 int err;
904
905 /*
906 * Search the hash table for the pid. If it is already grabbed or
907 * created, move the handle to the front of the lrulist, increment
908 * the reference count, and return the existing ps_prochandle.
909 */
910 for (dpr = dph->dph_hash[h]; dpr != NULL; dpr = dpr->dpr_hash) {
911 if (dpr->dpr_pid == pid && !dpr->dpr_stale) {
912 /*
913 * If the cached handle was opened read-only and
914 * this request is for a writeable handle, mark
915 * the cached handle as stale and open a new handle.
916 * Since it's stale, unmark it as cacheable.
917 */
918 if (dpr->dpr_rdonly && !(flags & PGRAB_RDONLY)) {
919 dt_dprintf("upgrading pid %d\n", (int)pid);
920 dpr->dpr_stale = B_TRUE;
921 dpr->dpr_cacheable = B_FALSE;
922 dph->dph_lrucnt--;
923 break;
924 }
925
926 dt_dprintf("grabbed pid %d (cached)\n", (int)pid);
927 dt_list_delete(&dph->dph_lrulist, dpr);
928 dt_list_prepend(&dph->dph_lrulist, dpr);
929 dpr->dpr_refs++;
930 return (dpr->dpr_proc);
931 }
932 }
933
934 if ((dpr = dt_zalloc(dtp, sizeof (dt_proc_t))) == NULL)
935 return (NULL); /* errno is set for us */
936
937 (void) pthread_mutex_init(&dpr->dpr_lock, NULL);
938 (void) pthread_cond_init(&dpr->dpr_cv, NULL);
939
940 if ((dpr->dpr_proc = Pgrab(pid, flags, &err)) == NULL) {
941 return (dt_proc_error(dtp, dpr,
942 "failed to grab pid %d: %s\n", (int)pid, Pgrab_error(err)));
943 }
944
945 dpr->dpr_hdl = dtp;
946 dpr->dpr_pid = pid;
947
948 (void) Punsetflags(dpr->dpr_proc, PR_KLC);
949 (void) Psetflags(dpr->dpr_proc, PR_RLC);
950
951 /*
952 * If we are attempting to grab the process without a monitor
953 * thread, then mark the process cacheable only if it's being
954 * grabbed read-only. If we're currently caching more process
955 * handles than dph_lrulim permits, attempt to find the
956 * least-recently-used handle that is currently unreferenced and
957 * release it from the cache. Otherwise we are grabbing the process
958 * for control: create a control thread for this process and store
959 * its ID in dpr->dpr_tid.
960 */
961 if (nomonitor || (flags & PGRAB_RDONLY)) {
962 if (dph->dph_lrucnt >= dph->dph_lrulim) {
963 for (opr = dt_list_prev(&dph->dph_lrulist);
964 opr != NULL; opr = dt_list_prev(opr)) {
965 if (opr->dpr_cacheable && opr->dpr_refs == 0) {
966 dt_proc_destroy(dtp, opr->dpr_proc);
967 break;
968 }
969 }
970 }
971
972 if (flags & PGRAB_RDONLY) {
973 dpr->dpr_cacheable = B_TRUE;
974 dpr->dpr_rdonly = B_TRUE;
975 dph->dph_lrucnt++;
976 }
977
978 } else if (dt_proc_create_thread(dtp, dpr, DT_PROC_STOP_GRAB) != 0)
979 return (NULL); /* dt_proc_error() has been called for us */
980
981 dpr->dpr_hash = dph->dph_hash[h];
982 dph->dph_hash[h] = dpr;
983 dt_list_prepend(&dph->dph_lrulist, dpr);
984
985 dt_dprintf("grabbed pid %d\n", (int)pid);
986 dpr->dpr_refs++;
987
988 return (dpr->dpr_proc);
989 }
990
991 void
dt_proc_release(dtrace_hdl_t * dtp,struct ps_prochandle * P)992 dt_proc_release(dtrace_hdl_t *dtp, struct ps_prochandle *P)
993 {
994 dt_proc_t *dpr = dt_proc_lookup(dtp, P, B_FALSE);
995 dt_proc_hash_t *dph = dtp->dt_procs;
996
997 assert(dpr != NULL);
998 assert(dpr->dpr_refs != 0);
999
1000 if (--dpr->dpr_refs == 0 &&
1001 (!dpr->dpr_cacheable || dph->dph_lrucnt > dph->dph_lrulim))
1002 dt_proc_destroy(dtp, P);
1003 }
1004
1005 void
dt_proc_continue(dtrace_hdl_t * dtp,struct ps_prochandle * P)1006 dt_proc_continue(dtrace_hdl_t *dtp, struct ps_prochandle *P)
1007 {
1008 dt_proc_t *dpr = dt_proc_lookup(dtp, P, B_FALSE);
1009
1010 (void) pthread_mutex_lock(&dpr->dpr_lock);
1011
1012 if (dpr->dpr_stop & DT_PROC_STOP_IDLE) {
1013 dpr->dpr_stop &= ~DT_PROC_STOP_IDLE;
1014 (void) pthread_cond_broadcast(&dpr->dpr_cv);
1015 }
1016
1017 (void) pthread_mutex_unlock(&dpr->dpr_lock);
1018 }
1019
1020 void
dt_proc_lock(dtrace_hdl_t * dtp,struct ps_prochandle * P)1021 dt_proc_lock(dtrace_hdl_t *dtp, struct ps_prochandle *P)
1022 {
1023 dt_proc_t *dpr = dt_proc_lookup(dtp, P, B_FALSE);
1024 int err = pthread_mutex_lock(&dpr->dpr_lock);
1025 assert(err == 0); /* check for recursion */
1026 }
1027
1028 void
dt_proc_unlock(dtrace_hdl_t * dtp,struct ps_prochandle * P)1029 dt_proc_unlock(dtrace_hdl_t *dtp, struct ps_prochandle *P)
1030 {
1031 dt_proc_t *dpr = dt_proc_lookup(dtp, P, B_FALSE);
1032 int err = pthread_mutex_unlock(&dpr->dpr_lock);
1033 assert(err == 0); /* check for unheld lock */
1034 }
1035
1036 void
dt_proc_hash_create(dtrace_hdl_t * dtp)1037 dt_proc_hash_create(dtrace_hdl_t *dtp)
1038 {
1039 if ((dtp->dt_procs = dt_zalloc(dtp, sizeof (dt_proc_hash_t) +
1040 sizeof (dt_proc_t *) * _dtrace_pidbuckets - 1)) != NULL) {
1041
1042 (void) pthread_mutex_init(&dtp->dt_procs->dph_lock, NULL);
1043 (void) pthread_cond_init(&dtp->dt_procs->dph_cv, NULL);
1044
1045 dtp->dt_procs->dph_hashlen = _dtrace_pidbuckets;
1046 dtp->dt_procs->dph_lrulim = _dtrace_pidlrulim;
1047 }
1048 }
1049
1050 void
dt_proc_hash_destroy(dtrace_hdl_t * dtp)1051 dt_proc_hash_destroy(dtrace_hdl_t *dtp)
1052 {
1053 dt_proc_hash_t *dph = dtp->dt_procs;
1054 dt_proc_t *dpr;
1055
1056 while ((dpr = dt_list_next(&dph->dph_lrulist)) != NULL)
1057 dt_proc_destroy(dtp, dpr->dpr_proc);
1058
1059 dtp->dt_procs = NULL;
1060 dt_free(dtp, dph);
1061 }
1062
1063 struct ps_prochandle *
dtrace_proc_create(dtrace_hdl_t * dtp,const char * file,char * const * argv)1064 dtrace_proc_create(dtrace_hdl_t *dtp, const char *file, char *const *argv)
1065 {
1066 dt_ident_t *idp = dt_idhash_lookup(dtp->dt_macros, "target");
1067 struct ps_prochandle *P = dt_proc_create(dtp, file, argv);
1068
1069 if (P != NULL && idp != NULL && idp->di_id == 0)
1070 idp->di_id = Pstatus(P)->pr_pid; /* $target = created pid */
1071
1072 return (P);
1073 }
1074
1075 struct ps_prochandle *
dtrace_proc_grab(dtrace_hdl_t * dtp,pid_t pid,int flags)1076 dtrace_proc_grab(dtrace_hdl_t *dtp, pid_t pid, int flags)
1077 {
1078 dt_ident_t *idp = dt_idhash_lookup(dtp->dt_macros, "target");
1079 struct ps_prochandle *P = dt_proc_grab(dtp, pid, flags, 0);
1080
1081 if (P != NULL && idp != NULL && idp->di_id == 0)
1082 idp->di_id = pid; /* $target = grabbed pid */
1083
1084 return (P);
1085 }
1086
1087 void
dtrace_proc_release(dtrace_hdl_t * dtp,struct ps_prochandle * P)1088 dtrace_proc_release(dtrace_hdl_t *dtp, struct ps_prochandle *P)
1089 {
1090 dt_proc_release(dtp, P);
1091 }
1092
1093 void
dtrace_proc_continue(dtrace_hdl_t * dtp,struct ps_prochandle * P)1094 dtrace_proc_continue(dtrace_hdl_t *dtp, struct ps_prochandle *P)
1095 {
1096 dt_proc_continue(dtp, P);
1097 }
1098