trace.c revision a9d6a6732c5b0b692a40ac073695332078a73738
1/* 2 * This file is part of ltrace. 3 * Copyright (C) 2007,2011,2012,2013 Petr Machata, Red Hat Inc. 4 * Copyright (C) 2010 Joe Damato 5 * Copyright (C) 1998,2002,2003,2004,2008,2009 Juan Cespedes 6 * Copyright (C) 2006 Ian Wienand 7 * 8 * This program is free software; you can redistribute it and/or 9 * modify it under the terms of the GNU General Public License as 10 * published by the Free Software Foundation; either version 2 of the 11 * License, or (at your option) any later version. 12 * 13 * This program is distributed in the hope that it will be useful, but 14 * WITHOUT ANY WARRANTY; without even the implied warranty of 15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 16 * General Public License for more details. 17 * 18 * You should have received a copy of the GNU General Public License 19 * along with this program; if not, write to the Free Software 20 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 21 * 02110-1301 USA 22 */ 23 24#include "config.h" 25 26#include <asm/unistd.h> 27#include <sys/types.h> 28#include <sys/wait.h> 29#include <assert.h> 30#include <errno.h> 31#include <stdio.h> 32#include <stdlib.h> 33#include <string.h> 34#include <unistd.h> 35 36#ifdef HAVE_LIBSELINUX 37# include <selinux/selinux.h> 38#endif 39 40#include "linux-gnu/trace.h" 41#include "linux-gnu/trace-defs.h" 42#include "backend.h" 43#include "breakpoint.h" 44#include "debug.h" 45#include "events.h" 46#include "options.h" 47#include "proc.h" 48#include "ptrace.h" 49#include "type.h" 50 51void 52trace_fail_warning(pid_t pid) 53{ 54 /* This was adapted from GDB. */ 55#ifdef HAVE_LIBSELINUX 56 static int checked = 0; 57 if (checked) 58 return; 59 checked = 1; 60 61 /* -1 is returned for errors, 0 if it has no effect, 1 if 62 * PTRACE_ATTACH is forbidden. */ 63 if (security_get_boolean_active("deny_ptrace") == 1) 64 fprintf(stderr, 65"The SELinux boolean 'deny_ptrace' is enabled, which may prevent ltrace from\n" 66"tracing other processes. You can disable this process attach protection by\n" 67"issuing 'setsebool deny_ptrace=0' in the superuser context.\n"); 68#endif /* HAVE_LIBSELINUX */ 69} 70 71void 72trace_me(void) 73{ 74 debug(DEBUG_PROCESS, "trace_me: pid=%d", getpid()); 75 if (ptrace(PTRACE_TRACEME, 0, 0, 0) < 0) { 76 perror("PTRACE_TRACEME"); 77 trace_fail_warning(getpid()); 78 exit(1); 79 } 80} 81 82/* There's a (hopefully) brief period of time after the child process 83 * forks when we can't trace it yet. Here we wait for kernel to 84 * prepare the process. */ 85int 86wait_for_proc(pid_t pid) 87{ 88 /* man ptrace: PTRACE_ATTACH attaches to the process specified 89 in pid. The child is sent a SIGSTOP, but will not 90 necessarily have stopped by the completion of this call; 91 use wait() to wait for the child to stop. */ 92 if (waitpid(pid, NULL, __WALL) != pid) { 93 perror ("trace_pid: waitpid"); 94 return -1; 95 } 96 97 return 0; 98} 99 100int 101trace_pid(pid_t pid) 102{ 103 debug(DEBUG_PROCESS, "trace_pid: pid=%d", pid); 104 /* This shouldn't emit error messages, as there are legitimate 105 * reasons that the PID can't be attached: like it may have 106 * already ended. */ 107 if (ptrace(PTRACE_ATTACH, pid, 0, 0) < 0) 108 return -1; 109 110 return wait_for_proc(pid); 111} 112 113void 114trace_set_options(struct process *proc) 115{ 116 if (proc->tracesysgood & 0x80) 117 return; 118 119 pid_t pid = proc->pid; 120 debug(DEBUG_PROCESS, "trace_set_options: pid=%d", pid); 121 122 long options = PTRACE_O_TRACESYSGOOD | PTRACE_O_TRACEFORK | 123 PTRACE_O_TRACEVFORK | PTRACE_O_TRACECLONE | 124 PTRACE_O_TRACEEXEC; 125 if (ptrace(PTRACE_SETOPTIONS, pid, 0, (void *)options) < 0 && 126 ptrace(PTRACE_OLDSETOPTIONS, pid, 0, (void *)options) < 0) { 127 perror("PTRACE_SETOPTIONS"); 128 return; 129 } 130 proc->tracesysgood |= 0x80; 131} 132 133void 134untrace_pid(pid_t pid) { 135 debug(DEBUG_PROCESS, "untrace_pid: pid=%d", pid); 136 ptrace(PTRACE_DETACH, pid, 0, 0); 137} 138 139void 140continue_after_signal(pid_t pid, int signum) 141{ 142 debug(DEBUG_PROCESS, "continue_after_signal: pid=%d, signum=%d", 143 pid, signum); 144 ptrace(PTRACE_SYSCALL, pid, 0, (void *)(uintptr_t)signum); 145} 146 147static enum ecb_status 148event_for_pid(Event *event, void *data) 149{ 150 if (event->proc != NULL && event->proc->pid == (pid_t)(uintptr_t)data) 151 return ECB_YIELD; 152 return ECB_CONT; 153} 154 155static int 156have_events_for(pid_t pid) 157{ 158 return each_qd_event(event_for_pid, (void *)(uintptr_t)pid) != NULL; 159} 160 161void 162continue_process(pid_t pid) 163{ 164 debug(DEBUG_PROCESS, "continue_process: pid=%d", pid); 165 166 /* Only really continue the process if there are no events in 167 the queue for this process. Otherwise just wait for the 168 other events to arrive. */ 169 if (!have_events_for(pid)) 170 /* We always trace syscalls to control fork(), 171 * clone(), execve()... */ 172 ptrace(PTRACE_SYSCALL, pid, 0, 0); 173 else 174 debug(DEBUG_PROCESS, 175 "putting off the continue, events in que."); 176} 177 178static struct pid_task * 179get_task_info(struct pid_set *pids, pid_t pid) 180{ 181 assert(pid != 0); 182 size_t i; 183 for (i = 0; i < pids->count; ++i) 184 if (pids->tasks[i].pid == pid) 185 return &pids->tasks[i]; 186 187 return NULL; 188} 189 190static struct pid_task * 191add_task_info(struct pid_set *pids, pid_t pid) 192{ 193 if (pids->count == pids->alloc) { 194 size_t ns = (2 * pids->alloc) ?: 4; 195 struct pid_task *n = realloc(pids->tasks, 196 sizeof(*pids->tasks) * ns); 197 if (n == NULL) 198 return NULL; 199 pids->tasks = n; 200 pids->alloc = ns; 201 } 202 struct pid_task * task_info = &pids->tasks[pids->count++]; 203 memset(task_info, 0, sizeof(*task_info)); 204 task_info->pid = pid; 205 return task_info; 206} 207 208static enum callback_status 209task_stopped(struct process *task, void *data) 210{ 211 enum process_status st = process_status(task->pid); 212 if (data != NULL) 213 *(enum process_status *)data = st; 214 215 /* If the task is already stopped, don't worry about it. 216 * Likewise if it managed to become a zombie or terminate in 217 * the meantime. This can happen when the whole thread group 218 * is terminating. */ 219 switch (st) { 220 case PS_INVALID: 221 case PS_TRACING_STOP: 222 case PS_ZOMBIE: 223 return CBS_CONT; 224 case PS_SLEEPING: 225 case PS_STOP: 226 case PS_OTHER: 227 return CBS_STOP; 228 } 229 230 abort (); 231} 232 233/* Task is blocked if it's stopped, or if it's a vfork parent. */ 234static enum callback_status 235task_blocked(struct process *task, void *data) 236{ 237 struct pid_set *pids = data; 238 struct pid_task *task_info = get_task_info(pids, task->pid); 239 if (task_info != NULL 240 && task_info->vforked) 241 return CBS_CONT; 242 243 return task_stopped(task, NULL); 244} 245 246static Event *process_vfork_on_event(struct event_handler *super, Event *event); 247 248static enum callback_status 249task_vforked(struct process *task, void *data) 250{ 251 if (task->event_handler != NULL 252 && task->event_handler->on_event == &process_vfork_on_event) 253 return CBS_STOP; 254 return CBS_CONT; 255} 256 257static int 258is_vfork_parent(struct process *task) 259{ 260 return each_task(task->leader, NULL, &task_vforked, NULL) != NULL; 261} 262 263static enum callback_status 264send_sigstop(struct process *task, void *data) 265{ 266 struct process *leader = task->leader; 267 struct pid_set *pids = data; 268 269 /* Look for pre-existing task record, or add new. */ 270 struct pid_task *task_info = get_task_info(pids, task->pid); 271 if (task_info == NULL) 272 task_info = add_task_info(pids, task->pid); 273 if (task_info == NULL) { 274 perror("send_sigstop: add_task_info"); 275 destroy_event_handler(leader); 276 /* Signal failure upwards. */ 277 return CBS_STOP; 278 } 279 280 /* This task still has not been attached to. It should be 281 stopped by the kernel. */ 282 if (task->state == STATE_BEING_CREATED) 283 return CBS_CONT; 284 285 /* Don't bother sending SIGSTOP if we are already stopped, or 286 * if we sent the SIGSTOP already, which happens when we are 287 * handling "onexit" and inherited the handler from breakpoint 288 * re-enablement. */ 289 enum process_status st; 290 if (task_stopped(task, &st) == CBS_CONT) 291 return CBS_CONT; 292 if (task_info->sigstopped) { 293 if (!task_info->delivered) 294 return CBS_CONT; 295 task_info->delivered = 0; 296 } 297 298 /* Also don't attempt to stop the process if it's a parent of 299 * vforked process. We set up event handler specially to hint 300 * us. In that case parent is in D state, which we use to 301 * weed out unnecessary looping. */ 302 if (st == PS_SLEEPING 303 && is_vfork_parent(task)) { 304 task_info->vforked = 1; 305 return CBS_CONT; 306 } 307 308 if (task_kill(task->pid, SIGSTOP) >= 0) { 309 debug(DEBUG_PROCESS, "send SIGSTOP to %d", task->pid); 310 task_info->sigstopped = 1; 311 } else 312 fprintf(stderr, 313 "Warning: couldn't send SIGSTOP to %d\n", task->pid); 314 315 return CBS_CONT; 316} 317 318/* On certain kernels, detaching right after a singlestep causes the 319 tracee to be killed with a SIGTRAP (that even though the singlestep 320 was properly caught by waitpid. The ugly workaround is to put a 321 breakpoint where IP points and let the process continue. After 322 this the breakpoint can be retracted and the process detached. */ 323static void 324ugly_workaround(struct process *proc) 325{ 326 void *ip = get_instruction_pointer(proc); 327 struct breakpoint *sbp = dict_find_entry(proc->leader->breakpoints, ip); 328 if (sbp != NULL) 329 enable_breakpoint(proc, sbp); 330 else 331 insert_breakpoint(proc, ip, NULL); 332 ptrace(PTRACE_CONT, proc->pid, 0, 0); 333} 334 335static void 336process_stopping_done(struct process_stopping_handler *self, 337 struct process *leader) 338{ 339 debug(DEBUG_PROCESS, "process stopping done %d", 340 self->task_enabling_breakpoint->pid); 341 342 if (!self->exiting) { 343 size_t i; 344 for (i = 0; i < self->pids.count; ++i) 345 if (self->pids.tasks[i].pid != 0 346 && (self->pids.tasks[i].delivered 347 || self->pids.tasks[i].sysret)) 348 continue_process(self->pids.tasks[i].pid); 349 continue_process(self->task_enabling_breakpoint->pid); 350 } 351 352 if (self->exiting) { 353 ugly_workaround: 354 self->state = PSH_UGLY_WORKAROUND; 355 ugly_workaround(self->task_enabling_breakpoint); 356 } else { 357 switch ((self->ugly_workaround_p)(self)) { 358 case CBS_FAIL: 359 /* xxx handle me */ 360 case CBS_STOP: 361 break; 362 case CBS_CONT: 363 goto ugly_workaround; 364 } 365 destroy_event_handler(leader); 366 } 367} 368 369/* Before we detach, we need to make sure that task's IP is on the 370 * edge of an instruction. So for tasks that have a breakpoint event 371 * in the queue, we adjust the instruction pointer, just like 372 * continue_after_breakpoint does. */ 373static enum ecb_status 374undo_breakpoint(Event *event, void *data) 375{ 376 if (event != NULL 377 && event->proc->leader == data 378 && event->type == EVENT_BREAKPOINT) 379 set_instruction_pointer(event->proc, event->e_un.brk_addr); 380 return ECB_CONT; 381} 382 383static enum callback_status 384untrace_task(struct process *task, void *data) 385{ 386 if (task != data) 387 untrace_pid(task->pid); 388 return CBS_CONT; 389} 390 391static enum callback_status 392remove_task(struct process *task, void *data) 393{ 394 /* Don't untrace leader just yet. */ 395 if (task != data) 396 remove_process(task); 397 return CBS_CONT; 398} 399 400static enum callback_status 401retract_breakpoint_cb(struct process *proc, struct breakpoint *bp, void *data) 402{ 403 breakpoint_on_retract(bp, proc); 404 return CBS_CONT; 405} 406 407static void 408detach_process(struct process *leader) 409{ 410 each_qd_event(&undo_breakpoint, leader); 411 disable_all_breakpoints(leader); 412 proc_each_breakpoint(leader, NULL, retract_breakpoint_cb, NULL); 413 414 /* Now untrace the process, if it was attached to by -p. */ 415 struct opt_p_t *it; 416 for (it = opt_p; it != NULL; it = it->next) { 417 struct process *proc = pid2proc(it->pid); 418 if (proc == NULL) 419 continue; 420 if (proc->leader == leader) { 421 each_task(leader, NULL, &untrace_task, NULL); 422 break; 423 } 424 } 425 each_task(leader, NULL, &remove_task, leader); 426 destroy_event_handler(leader); 427 remove_task(leader, NULL); 428} 429 430static void 431handle_stopping_event(struct pid_task *task_info, Event **eventp) 432{ 433 /* Mark all events, so that we know whom to SIGCONT later. */ 434 if (task_info != NULL) 435 task_info->got_event = 1; 436 437 Event *event = *eventp; 438 439 /* In every state, sink SIGSTOP events for tasks that it was 440 * sent to. */ 441 if (task_info != NULL 442 && event->type == EVENT_SIGNAL 443 && event->e_un.signum == SIGSTOP) { 444 debug(DEBUG_PROCESS, "SIGSTOP delivered to %d", task_info->pid); 445 if (task_info->sigstopped 446 && !task_info->delivered) { 447 task_info->delivered = 1; 448 *eventp = NULL; // sink the event 449 } else 450 fprintf(stderr, "suspicious: %d got SIGSTOP, but " 451 "sigstopped=%d and delivered=%d\n", 452 task_info->pid, task_info->sigstopped, 453 task_info->delivered); 454 } 455} 456 457/* Some SIGSTOPs may have not been delivered to their respective tasks 458 * yet. They are still in the queue. If we have seen an event for 459 * that process, continue it, so that the SIGSTOP can be delivered and 460 * caught by ltrace. We don't mind that the process is after 461 * breakpoint (and therefore potentially doesn't have aligned IP), 462 * because the signal will be delivered without the process actually 463 * starting. */ 464static void 465continue_for_sigstop_delivery(struct pid_set *pids) 466{ 467 size_t i; 468 for (i = 0; i < pids->count; ++i) { 469 if (pids->tasks[i].pid != 0 470 && pids->tasks[i].sigstopped 471 && !pids->tasks[i].delivered 472 && pids->tasks[i].got_event) { 473 debug(DEBUG_PROCESS, "continue %d for SIGSTOP delivery", 474 pids->tasks[i].pid); 475 ptrace(PTRACE_SYSCALL, pids->tasks[i].pid, 0, 0); 476 } 477 } 478} 479 480static int 481event_exit_p(Event *event) 482{ 483 return event != NULL && (event->type == EVENT_EXIT 484 || event->type == EVENT_EXIT_SIGNAL); 485} 486 487static int 488event_exit_or_none_p(Event *event) 489{ 490 return event == NULL || event_exit_p(event) 491 || event->type == EVENT_NONE; 492} 493 494static int 495await_sigstop_delivery(struct pid_set *pids, struct pid_task *task_info, 496 Event *event) 497{ 498 /* If we still didn't get our SIGSTOP, continue the process 499 * and carry on. */ 500 if (event != NULL && !event_exit_or_none_p(event) 501 && task_info != NULL && task_info->sigstopped) { 502 debug(DEBUG_PROCESS, "continue %d for SIGSTOP delivery", 503 task_info->pid); 504 /* We should get the signal the first thing 505 * after this, so it should be OK to continue 506 * even if we are over a breakpoint. */ 507 ptrace(PTRACE_SYSCALL, task_info->pid, 0, 0); 508 509 } else { 510 /* If all SIGSTOPs were delivered, uninstall the 511 * handler and continue everyone. */ 512 /* XXX I suspect that we should check tasks that are 513 * still around. Is things are now, there should be a 514 * race between waiting for everyone to stop and one 515 * of the tasks exiting. */ 516 int all_clear = 1; 517 size_t i; 518 for (i = 0; i < pids->count; ++i) 519 if (pids->tasks[i].pid != 0 520 && pids->tasks[i].sigstopped 521 && !pids->tasks[i].delivered) { 522 all_clear = 0; 523 break; 524 } 525 return all_clear; 526 } 527 528 return 0; 529} 530 531static int 532all_stops_accountable(struct pid_set *pids) 533{ 534 size_t i; 535 for (i = 0; i < pids->count; ++i) 536 if (pids->tasks[i].pid != 0 537 && !pids->tasks[i].got_event 538 && !have_events_for(pids->tasks[i].pid)) 539 return 0; 540 return 1; 541} 542 543#ifndef ARCH_HAVE_SW_SINGLESTEP 544enum sw_singlestep_status 545arch_sw_singlestep(struct process *proc, struct breakpoint *bp, 546 int (*add_cb)(arch_addr_t, struct sw_singlestep_data *), 547 struct sw_singlestep_data *data) 548{ 549 return SWS_HW; 550} 551#endif 552 553static Event *process_stopping_on_event(struct event_handler *super, 554 Event *event); 555 556static void 557remove_sw_breakpoints(struct process *proc) 558{ 559 struct process_stopping_handler *self 560 = (void *)proc->leader->event_handler; 561 assert(self != NULL); 562 assert(self->super.on_event == process_stopping_on_event); 563 564 int ct = sizeof(self->sws_bp_addrs) / sizeof(*self->sws_bp_addrs); 565 int i; 566 for (i = 0; i < ct; ++i) 567 if (self->sws_bp_addrs[i] != 0) { 568 delete_breakpoint(proc, self->sws_bp_addrs[i]); 569 self->sws_bp_addrs[i] = 0; 570 } 571} 572 573static void 574sw_singlestep_bp_on_hit(struct breakpoint *bp, struct process *proc) 575{ 576 remove_sw_breakpoints(proc); 577} 578 579struct sw_singlestep_data { 580 struct process_stopping_handler *self; 581}; 582 583static int 584sw_singlestep_add_bp(arch_addr_t addr, struct sw_singlestep_data *data) 585{ 586 struct process_stopping_handler *self = data->self; 587 struct process *proc = self->task_enabling_breakpoint; 588 589 int ct = sizeof(self->sws_bp_addrs) 590 / sizeof(*self->sws_bp_addrs); 591 int i; 592 for (i = 0; i < ct; ++i) 593 if (self->sws_bp_addrs[i] == 0) { 594 self->sws_bp_addrs[i] = addr; 595 static struct bp_callbacks cbs = { 596 .on_hit = sw_singlestep_bp_on_hit, 597 }; 598 struct breakpoint *bp 599 = insert_breakpoint(proc, addr, NULL); 600 breakpoint_set_callbacks(bp, &cbs); 601 return 0; 602 } 603 604 assert(!"Too many sw singlestep breakpoints!"); 605 abort(); 606} 607 608static int 609singlestep(struct process_stopping_handler *self) 610{ 611 struct process *proc = self->task_enabling_breakpoint; 612 613 struct sw_singlestep_data data = { self }; 614 switch (arch_sw_singlestep(self->task_enabling_breakpoint, 615 self->breakpoint_being_enabled, 616 &sw_singlestep_add_bp, &data)) { 617 case SWS_HW: 618 /* Otherwise do the default action: singlestep. */ 619 debug(1, "PTRACE_SINGLESTEP"); 620 if (ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0)) { 621 perror("PTRACE_SINGLESTEP"); 622 return -1; 623 } 624 return 0; 625 626 case SWS_OK: 627 return 0; 628 629 case SWS_FAIL: 630 return -1; 631 } 632 abort(); 633} 634 635static void 636post_singlestep(struct process_stopping_handler *self, 637 struct Event **eventp) 638{ 639 continue_for_sigstop_delivery(&self->pids); 640 641 if (*eventp != NULL && (*eventp)->type == EVENT_BREAKPOINT) 642 *eventp = NULL; // handled 643 644 struct process *proc = self->task_enabling_breakpoint; 645 646 remove_sw_breakpoints(proc); 647 self->breakpoint_being_enabled = NULL; 648} 649 650static void 651singlestep_error(struct process_stopping_handler *self) 652{ 653 struct process *teb = self->task_enabling_breakpoint; 654 struct breakpoint *sbp = self->breakpoint_being_enabled; 655 fprintf(stderr, "%d couldn't continue when handling %s (%p) at %p\n", 656 teb->pid, breakpoint_name(sbp), sbp->addr, 657 get_instruction_pointer(teb)); 658 delete_breakpoint(teb->leader, sbp->addr); 659} 660 661static void 662pt_continue(struct process_stopping_handler *self) 663{ 664 struct process *teb = self->task_enabling_breakpoint; 665 debug(1, "PTRACE_CONT"); 666 ptrace(PTRACE_CONT, teb->pid, 0, 0); 667} 668 669static void 670pt_singlestep(struct process_stopping_handler *self) 671{ 672 if (singlestep(self) < 0) 673 singlestep_error(self); 674} 675 676static void 677disable_and(struct process_stopping_handler *self, 678 void (*do_this)(struct process_stopping_handler *self)) 679{ 680 struct process *teb = self->task_enabling_breakpoint; 681 debug(DEBUG_PROCESS, "all stopped, now singlestep/cont %d", teb->pid); 682 if (self->breakpoint_being_enabled->enabled) 683 disable_breakpoint(teb, self->breakpoint_being_enabled); 684 (do_this)(self); 685 self->state = PSH_SINGLESTEP; 686} 687 688void 689linux_ptrace_disable_and_singlestep(struct process_stopping_handler *self) 690{ 691 disable_and(self, &pt_singlestep); 692} 693 694void 695linux_ptrace_disable_and_continue(struct process_stopping_handler *self) 696{ 697 disable_and(self, &pt_continue); 698} 699 700/* This event handler is installed when we are in the process of 701 * stopping the whole thread group to do the pointer re-enablement for 702 * one of the threads. We pump all events to the queue for later 703 * processing while we wait for all the threads to stop. When this 704 * happens, we let the re-enablement thread to PTRACE_SINGLESTEP, 705 * re-enable, and continue everyone. */ 706static Event * 707process_stopping_on_event(struct event_handler *super, Event *event) 708{ 709 struct process_stopping_handler *self = (void *)super; 710 struct process *task = event->proc; 711 struct process *leader = task->leader; 712 struct process *teb = self->task_enabling_breakpoint; 713 714 debug(DEBUG_PROCESS, 715 "process_stopping_on_event: pid %d; event type %d; state %d", 716 task->pid, event->type, self->state); 717 718 struct pid_task *task_info = get_task_info(&self->pids, task->pid); 719 if (task_info == NULL) 720 fprintf(stderr, "new task??? %d\n", task->pid); 721 handle_stopping_event(task_info, &event); 722 723 int state = self->state; 724 int event_to_queue = !event_exit_or_none_p(event); 725 726 /* Deactivate the entry if the task exits. */ 727 if (event_exit_p(event) && task_info != NULL) 728 task_info->pid = 0; 729 730 /* Always handle sysrets. Whether sysret occurred and what 731 * sys it rets from may need to be determined based on process 732 * stack, so we need to keep that in sync with reality. Note 733 * that we don't continue the process after the sysret is 734 * handled. See continue_after_syscall. */ 735 if (event != NULL && event->type == EVENT_SYSRET) { 736 debug(1, "%d LT_EV_SYSRET", event->proc->pid); 737 event_to_queue = 0; 738 task_info->sysret = 1; 739 } 740 741 switch (state) { 742 case PSH_STOPPING: 743 /* If everyone is stopped, singlestep. */ 744 if (each_task(leader, NULL, &task_blocked, 745 &self->pids) == NULL) { 746 (self->on_all_stopped)(self); 747 state = self->state; 748 } 749 break; 750 751 case PSH_SINGLESTEP: 752 /* In singlestep state, breakpoint signifies that we 753 * have now stepped, and can re-enable the breakpoint. */ 754 if (event != NULL && task == teb) { 755 756 /* If this was caused by a real breakpoint, as 757 * opposed to a singlestep, assume that it's 758 * an artificial breakpoint installed for some 759 * reason for the re-enablement. In that case 760 * handle it. */ 761 if (event->type == EVENT_BREAKPOINT) { 762 arch_addr_t ip 763 = get_instruction_pointer(task); 764 struct breakpoint *other 765 = address2bpstruct(leader, ip); 766 if (other != NULL) 767 breakpoint_on_hit(other, task); 768 } 769 770 /* If we got SIGNAL instead of BREAKPOINT, 771 * then this is not singlestep at all. */ 772 if (event->type == EVENT_SIGNAL) { 773 do_singlestep: 774 if (singlestep(self) < 0) { 775 singlestep_error(self); 776 post_singlestep(self, &event); 777 goto psh_sinking; 778 } 779 break; 780 } else { 781 switch ((self->keep_stepping_p)(self)) { 782 case CBS_FAIL: 783 /* XXX handle me */ 784 case CBS_STOP: 785 break; 786 case CBS_CONT: 787 /* Sink singlestep event. */ 788 if (event->type == EVENT_BREAKPOINT) 789 event = NULL; 790 goto do_singlestep; 791 } 792 } 793 794 /* Re-enable the breakpoint that we are 795 * stepping over. */ 796 struct breakpoint *sbp = self->breakpoint_being_enabled; 797 if (sbp->enabled) 798 enable_breakpoint(teb, sbp); 799 800 post_singlestep(self, &event); 801 goto psh_sinking; 802 } 803 break; 804 805 psh_sinking: 806 state = self->state = PSH_SINKING; 807 /* Fall through. */ 808 case PSH_SINKING: 809 if (await_sigstop_delivery(&self->pids, task_info, event)) 810 process_stopping_done(self, leader); 811 break; 812 813 case PSH_UGLY_WORKAROUND: 814 if (event == NULL) 815 break; 816 if (event->type == EVENT_BREAKPOINT) { 817 undo_breakpoint(event, leader); 818 if (task == teb) 819 self->task_enabling_breakpoint = NULL; 820 } 821 if (self->task_enabling_breakpoint == NULL 822 && all_stops_accountable(&self->pids)) { 823 undo_breakpoint(event, leader); 824 detach_process(leader); 825 event = NULL; // handled 826 } 827 } 828 829 if (event != NULL && event_to_queue) { 830 enque_event(event); 831 event = NULL; // sink the event 832 } 833 834 return event; 835} 836 837static void 838process_stopping_destroy(struct event_handler *super) 839{ 840 struct process_stopping_handler *self = (void *)super; 841 free(self->pids.tasks); 842} 843 844static enum callback_status 845no(struct process_stopping_handler *self) 846{ 847 return CBS_STOP; 848} 849 850int 851process_install_stopping_handler(struct process *proc, struct breakpoint *sbp, 852 void (*as)(struct process_stopping_handler *), 853 enum callback_status (*ks) 854 (struct process_stopping_handler *), 855 enum callback_status (*uw) 856 (struct process_stopping_handler *)) 857{ 858 debug(DEBUG_FUNCTION, 859 "process_install_stopping_handler: pid=%d", proc->pid); 860 861 struct process_stopping_handler *handler = calloc(sizeof(*handler), 1); 862 if (handler == NULL) 863 return -1; 864 865 if (as == NULL) 866 as = &linux_ptrace_disable_and_singlestep; 867 if (ks == NULL) 868 ks = &no; 869 if (uw == NULL) 870 uw = &no; 871 872 handler->super.on_event = process_stopping_on_event; 873 handler->super.destroy = process_stopping_destroy; 874 handler->task_enabling_breakpoint = proc; 875 handler->breakpoint_being_enabled = sbp; 876 handler->on_all_stopped = as; 877 handler->keep_stepping_p = ks; 878 handler->ugly_workaround_p = uw; 879 880 install_event_handler(proc->leader, &handler->super); 881 882 if (each_task(proc->leader, NULL, &send_sigstop, 883 &handler->pids) != NULL) { 884 destroy_event_handler(proc); 885 return -1; 886 } 887 888 /* And deliver the first fake event, in case all the 889 * conditions are already fulfilled. */ 890 Event ev = { 891 .type = EVENT_NONE, 892 .proc = proc, 893 }; 894 process_stopping_on_event(&handler->super, &ev); 895 896 return 0; 897} 898 899void 900continue_after_breakpoint(struct process *proc, struct breakpoint *sbp) 901{ 902 debug(DEBUG_PROCESS, 903 "continue_after_breakpoint: pid=%d, addr=%p", 904 proc->pid, sbp->addr); 905 906 set_instruction_pointer(proc, sbp->addr); 907 908 if (sbp->enabled == 0) { 909 continue_process(proc->pid); 910 } else if (process_install_stopping_handler 911 (proc, sbp, NULL, NULL, NULL) < 0) { 912 perror("process_stopping_handler_create"); 913 /* Carry on not bothering to re-enable. */ 914 continue_process(proc->pid); 915 } 916} 917 918/** 919 * Ltrace exit. When we are about to exit, we have to go through all 920 * the processes, stop them all, remove all the breakpoints, and then 921 * detach the processes that we attached to using -p. If we left the 922 * other tasks running, they might hit stray return breakpoints and 923 * produce artifacts, so we better stop everyone, even if it's a bit 924 * of extra work. 925 */ 926struct ltrace_exiting_handler 927{ 928 struct event_handler super; 929 struct pid_set pids; 930}; 931 932static Event * 933ltrace_exiting_on_event(struct event_handler *super, Event *event) 934{ 935 struct ltrace_exiting_handler *self = (void *)super; 936 struct process *task = event->proc; 937 struct process *leader = task->leader; 938 939 debug(DEBUG_PROCESS, 940 "ltrace_exiting_on_event: pid %d; event type %d", 941 task->pid, event->type); 942 943 struct pid_task *task_info = get_task_info(&self->pids, task->pid); 944 handle_stopping_event(task_info, &event); 945 946 if (event != NULL && event->type == EVENT_BREAKPOINT) 947 undo_breakpoint(event, leader); 948 949 if (await_sigstop_delivery(&self->pids, task_info, event) 950 && all_stops_accountable(&self->pids)) 951 detach_process(leader); 952 953 /* Sink all non-exit events. We are about to exit, so we 954 * don't bother with queuing them. */ 955 if (event_exit_or_none_p(event)) 956 return event; 957 958 return NULL; 959} 960 961static void 962ltrace_exiting_destroy(struct event_handler *super) 963{ 964 struct ltrace_exiting_handler *self = (void *)super; 965 free(self->pids.tasks); 966} 967 968static int 969ltrace_exiting_install_handler(struct process *proc) 970{ 971 /* Only install to leader. */ 972 if (proc->leader != proc) 973 return 0; 974 975 /* Perhaps we are already installed, if the user passed 976 * several -p options that are tasks of one process. */ 977 if (proc->event_handler != NULL 978 && proc->event_handler->on_event == <race_exiting_on_event) 979 return 0; 980 981 /* If stopping handler is already present, let it do the 982 * work. */ 983 if (proc->event_handler != NULL) { 984 assert(proc->event_handler->on_event 985 == &process_stopping_on_event); 986 struct process_stopping_handler *other 987 = (void *)proc->event_handler; 988 other->exiting = 1; 989 return 0; 990 } 991 992 struct ltrace_exiting_handler *handler 993 = calloc(sizeof(*handler), 1); 994 if (handler == NULL) { 995 perror("malloc exiting handler"); 996 fatal: 997 /* XXXXXXXXXXXXXXXXXXX fixme */ 998 return -1; 999 } 1000 1001 handler->super.on_event = ltrace_exiting_on_event; 1002 handler->super.destroy = ltrace_exiting_destroy; 1003 install_event_handler(proc->leader, &handler->super); 1004 1005 if (each_task(proc->leader, NULL, &send_sigstop, 1006 &handler->pids) != NULL) 1007 goto fatal; 1008 1009 return 0; 1010} 1011 1012/* 1013 * When the traced process vforks, it's suspended until the child 1014 * process calls _exit or exec*. In the meantime, the two share the 1015 * address space. 1016 * 1017 * The child process should only ever call _exit or exec*, but we 1018 * can't count on that (it's not the role of ltrace to policy, but to 1019 * observe). In any case, we will _at least_ have to deal with 1020 * removal of vfork return breakpoint (which we have to smuggle back 1021 * in, so that the parent can see it, too), and introduction of exec* 1022 * return breakpoint. Since we already have both breakpoint actions 1023 * to deal with, we might as well support it all. 1024 * 1025 * The gist is that we pretend that the child is in a thread group 1026 * with its parent, and handle it as a multi-threaded case, with the 1027 * exception that we know that the parent is blocked, and don't 1028 * attempt to stop it. When the child execs, we undo the setup. 1029 */ 1030 1031struct process_vfork_handler 1032{ 1033 struct event_handler super; 1034 void *bp_addr; 1035}; 1036 1037static Event * 1038process_vfork_on_event(struct event_handler *super, Event *event) 1039{ 1040 debug(DEBUG_PROCESS, 1041 "process_vfork_on_event: pid %d; event type %d", 1042 event->proc->pid, event->type); 1043 1044 struct process_vfork_handler *self = (void *)super; 1045 struct breakpoint *sbp; 1046 assert(self != NULL); 1047 1048 switch (event->type) { 1049 case EVENT_BREAKPOINT: 1050 /* Remember the vfork return breakpoint. */ 1051 if (self->bp_addr == 0) 1052 self->bp_addr = event->e_un.brk_addr; 1053 break; 1054 1055 case EVENT_EXIT: 1056 case EVENT_EXIT_SIGNAL: 1057 case EVENT_EXEC: 1058 /* Smuggle back in the vfork return breakpoint, so 1059 * that our parent can trip over it once again. */ 1060 if (self->bp_addr != 0) { 1061 sbp = dict_find_entry(event->proc->leader->breakpoints, 1062 self->bp_addr); 1063 if (sbp != NULL) 1064 assert(sbp->libsym == NULL); 1065 /* We don't mind failing that, it's not a big 1066 * deal to not display one extra vfork return. */ 1067 insert_breakpoint(event->proc->parent, 1068 self->bp_addr, NULL); 1069 } 1070 1071 continue_process(event->proc->parent->pid); 1072 1073 /* Remove the leader that we artificially set up 1074 * earlier. */ 1075 change_process_leader(event->proc, event->proc); 1076 destroy_event_handler(event->proc); 1077 1078 default: 1079 ; 1080 } 1081 1082 return event; 1083} 1084 1085void 1086continue_after_vfork(struct process *proc) 1087{ 1088 debug(DEBUG_PROCESS, "continue_after_vfork: pid=%d", proc->pid); 1089 struct process_vfork_handler *handler = calloc(sizeof(*handler), 1); 1090 if (handler == NULL) { 1091 perror("malloc vfork handler"); 1092 /* Carry on not bothering to treat the process as 1093 * necessary. */ 1094 continue_process(proc->parent->pid); 1095 return; 1096 } 1097 1098 /* We must set up custom event handler, so that we see 1099 * exec/exit events for the task itself. */ 1100 handler->super.on_event = process_vfork_on_event; 1101 install_event_handler(proc, &handler->super); 1102 1103 /* Make sure that the child is sole thread. */ 1104 assert(proc->leader == proc); 1105 assert(proc->next == NULL || proc->next->leader != proc); 1106 1107 /* Make sure that the child's parent is properly set up. */ 1108 assert(proc->parent != NULL); 1109 assert(proc->parent->leader != NULL); 1110 1111 change_process_leader(proc, proc->parent->leader); 1112} 1113 1114static int 1115is_mid_stopping(struct process *proc) 1116{ 1117 return proc != NULL 1118 && proc->event_handler != NULL 1119 && proc->event_handler->on_event == &process_stopping_on_event; 1120} 1121 1122void 1123continue_after_syscall(struct process *proc, int sysnum, int ret_p) 1124{ 1125 /* Don't continue if we are mid-stopping. */ 1126 if (ret_p && (is_mid_stopping(proc) || is_mid_stopping(proc->leader))) { 1127 debug(DEBUG_PROCESS, 1128 "continue_after_syscall: don't continue %d", 1129 proc->pid); 1130 return; 1131 } 1132 continue_process(proc->pid); 1133} 1134 1135void 1136continue_after_exec(struct process *proc) 1137{ 1138 continue_process(proc->pid); 1139 1140 /* After the exec, we expect to hit the first executable 1141 * instruction. 1142 * 1143 * XXX TODO It would be nice to have this removed, but then we 1144 * need to do that also for initial call to wait_for_proc in 1145 * execute_program. In that case we could generate a 1146 * EVENT_FIRST event or something, or maybe this could somehow 1147 * be rolled into EVENT_NEW. */ 1148 wait_for_proc(proc->pid); 1149 continue_process(proc->pid); 1150} 1151 1152/* If ltrace gets SIGINT, the processes directly or indirectly run by 1153 * ltrace get it too. We just have to wait long enough for the signal 1154 * to be delivered and the process terminated, which we notice and 1155 * exit ltrace, too. So there's not much we need to do there. We 1156 * want to keep tracing those processes as usual, in case they just 1157 * SIG_IGN the SIGINT to do their shutdown etc. 1158 * 1159 * For processes ran on the background, we want to install an exit 1160 * handler that stops all the threads, removes all breakpoints, and 1161 * detaches. 1162 */ 1163void 1164os_ltrace_exiting(void) 1165{ 1166 struct opt_p_t *it; 1167 for (it = opt_p; it != NULL; it = it->next) { 1168 struct process *proc = pid2proc(it->pid); 1169 if (proc == NULL || proc->leader == NULL) 1170 continue; 1171 if (ltrace_exiting_install_handler(proc->leader) < 0) 1172 fprintf(stderr, 1173 "Couldn't install exiting handler for %d.\n", 1174 proc->pid); 1175 } 1176} 1177 1178int 1179os_ltrace_exiting_sighandler(void) 1180{ 1181 extern int linux_in_waitpid; 1182 if (linux_in_waitpid) { 1183 os_ltrace_exiting(); 1184 return 1; 1185 } 1186 return 0; 1187} 1188 1189size_t 1190umovebytes(struct process *proc, void *addr, void *laddr, size_t len) 1191{ 1192 1193 union { 1194 long a; 1195 char c[sizeof(long)]; 1196 } a; 1197 int started = 0; 1198 size_t offset = 0, bytes_read = 0; 1199 1200 while (offset < len) { 1201 a.a = ptrace(PTRACE_PEEKTEXT, proc->pid, addr + offset, 0); 1202 if (a.a == -1 && errno) { 1203 if (started && errno == EIO) 1204 return bytes_read; 1205 else 1206 return -1; 1207 } 1208 started = 1; 1209 1210 if (len - offset >= sizeof(long)) { 1211 memcpy(laddr + offset, &a.c[0], sizeof(long)); 1212 bytes_read += sizeof(long); 1213 } 1214 else { 1215 memcpy(laddr + offset, &a.c[0], len - offset); 1216 bytes_read += (len - offset); 1217 } 1218 offset += sizeof(long); 1219 } 1220 1221 return bytes_read; 1222} 1223