trace.c revision d7e4ca82e1cf20bb2605befb1da74dd1688c706e
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 arch_addr_t ip = get_instruction_pointer(proc); 327 struct breakpoint **found = DICT_FIND(proc->leader->breakpoints, &ip, 328 struct breakpoint *); 329 if (found != NULL) 330 enable_breakpoint(proc, *found); 331 else 332 insert_breakpoint(proc, ip, NULL); 333 ptrace(PTRACE_CONT, proc->pid, 0, 0); 334} 335 336static void 337process_stopping_done(struct process_stopping_handler *self, 338 struct process *leader) 339{ 340 debug(DEBUG_PROCESS, "process stopping done %d", 341 self->task_enabling_breakpoint->pid); 342 343 if (!self->exiting) { 344 size_t i; 345 for (i = 0; i < self->pids.count; ++i) 346 if (self->pids.tasks[i].pid != 0 347 && (self->pids.tasks[i].delivered 348 || self->pids.tasks[i].sysret)) 349 continue_process(self->pids.tasks[i].pid); 350 continue_process(self->task_enabling_breakpoint->pid); 351 } 352 353 if (self->exiting) { 354 ugly_workaround: 355 self->state = PSH_UGLY_WORKAROUND; 356 ugly_workaround(self->task_enabling_breakpoint); 357 } else { 358 switch ((self->ugly_workaround_p)(self)) { 359 case CBS_FAIL: 360 /* xxx handle me */ 361 case CBS_STOP: 362 break; 363 case CBS_CONT: 364 goto ugly_workaround; 365 } 366 destroy_event_handler(leader); 367 } 368} 369 370/* Before we detach, we need to make sure that task's IP is on the 371 * edge of an instruction. So for tasks that have a breakpoint event 372 * in the queue, we adjust the instruction pointer, just like 373 * continue_after_breakpoint does. */ 374static enum ecb_status 375undo_breakpoint(Event *event, void *data) 376{ 377 if (event != NULL 378 && event->proc->leader == data 379 && event->type == EVENT_BREAKPOINT) 380 set_instruction_pointer(event->proc, event->e_un.brk_addr); 381 return ECB_CONT; 382} 383 384static enum callback_status 385untrace_task(struct process *task, void *data) 386{ 387 if (task != data) 388 untrace_pid(task->pid); 389 return CBS_CONT; 390} 391 392static enum callback_status 393remove_task(struct process *task, void *data) 394{ 395 /* Don't untrace leader just yet. */ 396 if (task != data) 397 remove_process(task); 398 return CBS_CONT; 399} 400 401static enum callback_status 402retract_breakpoint_cb(struct process *proc, struct breakpoint *bp, void *data) 403{ 404 breakpoint_on_retract(bp, proc); 405 return CBS_CONT; 406} 407 408static void 409detach_process(struct process *leader) 410{ 411 each_qd_event(&undo_breakpoint, leader); 412 disable_all_breakpoints(leader); 413 proc_each_breakpoint(leader, NULL, retract_breakpoint_cb, NULL); 414 415 /* Now untrace the process, if it was attached to by -p. */ 416 struct opt_p_t *it; 417 for (it = opt_p; it != NULL; it = it->next) { 418 struct process *proc = pid2proc(it->pid); 419 if (proc == NULL) 420 continue; 421 if (proc->leader == leader) { 422 each_task(leader, NULL, &untrace_task, NULL); 423 break; 424 } 425 } 426 each_task(leader, NULL, &remove_task, leader); 427 destroy_event_handler(leader); 428 remove_task(leader, NULL); 429} 430 431static void 432handle_stopping_event(struct pid_task *task_info, Event **eventp) 433{ 434 /* Mark all events, so that we know whom to SIGCONT later. */ 435 if (task_info != NULL) 436 task_info->got_event = 1; 437 438 Event *event = *eventp; 439 440 /* In every state, sink SIGSTOP events for tasks that it was 441 * sent to. */ 442 if (task_info != NULL 443 && event->type == EVENT_SIGNAL 444 && event->e_un.signum == SIGSTOP) { 445 debug(DEBUG_PROCESS, "SIGSTOP delivered to %d", task_info->pid); 446 if (task_info->sigstopped 447 && !task_info->delivered) { 448 task_info->delivered = 1; 449 *eventp = NULL; // sink the event 450 } else 451 fprintf(stderr, "suspicious: %d got SIGSTOP, but " 452 "sigstopped=%d and delivered=%d\n", 453 task_info->pid, task_info->sigstopped, 454 task_info->delivered); 455 } 456} 457 458/* Some SIGSTOPs may have not been delivered to their respective tasks 459 * yet. They are still in the queue. If we have seen an event for 460 * that process, continue it, so that the SIGSTOP can be delivered and 461 * caught by ltrace. We don't mind that the process is after 462 * breakpoint (and therefore potentially doesn't have aligned IP), 463 * because the signal will be delivered without the process actually 464 * starting. */ 465static void 466continue_for_sigstop_delivery(struct pid_set *pids) 467{ 468 size_t i; 469 for (i = 0; i < pids->count; ++i) { 470 if (pids->tasks[i].pid != 0 471 && pids->tasks[i].sigstopped 472 && !pids->tasks[i].delivered 473 && pids->tasks[i].got_event) { 474 debug(DEBUG_PROCESS, "continue %d for SIGSTOP delivery", 475 pids->tasks[i].pid); 476 ptrace(PTRACE_SYSCALL, pids->tasks[i].pid, 0, 0); 477 } 478 } 479} 480 481static int 482event_exit_p(Event *event) 483{ 484 return event != NULL && (event->type == EVENT_EXIT 485 || event->type == EVENT_EXIT_SIGNAL); 486} 487 488static int 489event_exit_or_none_p(Event *event) 490{ 491 return event == NULL || event_exit_p(event) 492 || event->type == EVENT_NONE; 493} 494 495static int 496await_sigstop_delivery(struct pid_set *pids, struct pid_task *task_info, 497 Event *event) 498{ 499 /* If we still didn't get our SIGSTOP, continue the process 500 * and carry on. */ 501 if (event != NULL && !event_exit_or_none_p(event) 502 && task_info != NULL && task_info->sigstopped) { 503 debug(DEBUG_PROCESS, "continue %d for SIGSTOP delivery", 504 task_info->pid); 505 /* We should get the signal the first thing 506 * after this, so it should be OK to continue 507 * even if we are over a breakpoint. */ 508 ptrace(PTRACE_SYSCALL, task_info->pid, 0, 0); 509 510 } else { 511 /* If all SIGSTOPs were delivered, uninstall the 512 * handler and continue everyone. */ 513 /* XXX I suspect that we should check tasks that are 514 * still around. Is things are now, there should be a 515 * race between waiting for everyone to stop and one 516 * of the tasks exiting. */ 517 int all_clear = 1; 518 size_t i; 519 for (i = 0; i < pids->count; ++i) 520 if (pids->tasks[i].pid != 0 521 && pids->tasks[i].sigstopped 522 && !pids->tasks[i].delivered) { 523 all_clear = 0; 524 break; 525 } 526 return all_clear; 527 } 528 529 return 0; 530} 531 532static int 533all_stops_accountable(struct pid_set *pids) 534{ 535 size_t i; 536 for (i = 0; i < pids->count; ++i) 537 if (pids->tasks[i].pid != 0 538 && !pids->tasks[i].got_event 539 && !have_events_for(pids->tasks[i].pid)) 540 return 0; 541 return 1; 542} 543 544#ifndef ARCH_HAVE_SW_SINGLESTEP 545enum sw_singlestep_status 546arch_sw_singlestep(struct process *proc, struct breakpoint *bp, 547 int (*add_cb)(arch_addr_t, struct sw_singlestep_data *), 548 struct sw_singlestep_data *data) 549{ 550 return SWS_HW; 551} 552#endif 553 554static Event *process_stopping_on_event(struct event_handler *super, 555 Event *event); 556 557static void 558remove_sw_breakpoints(struct process *proc) 559{ 560 struct process_stopping_handler *self 561 = (void *)proc->leader->event_handler; 562 assert(self != NULL); 563 assert(self->super.on_event == process_stopping_on_event); 564 565 int ct = sizeof(self->sws_bp_addrs) / sizeof(*self->sws_bp_addrs); 566 int i; 567 for (i = 0; i < ct; ++i) 568 if (self->sws_bp_addrs[i] != 0) { 569 delete_breakpoint(proc, self->sws_bp_addrs[i]); 570 self->sws_bp_addrs[i] = 0; 571 } 572} 573 574static void 575sw_singlestep_bp_on_hit(struct breakpoint *bp, struct process *proc) 576{ 577 remove_sw_breakpoints(proc); 578} 579 580struct sw_singlestep_data { 581 struct process_stopping_handler *self; 582}; 583 584static int 585sw_singlestep_add_bp(arch_addr_t addr, struct sw_singlestep_data *data) 586{ 587 struct process_stopping_handler *self = data->self; 588 struct process *proc = self->task_enabling_breakpoint; 589 590 int ct = sizeof(self->sws_bp_addrs) 591 / sizeof(*self->sws_bp_addrs); 592 int i; 593 for (i = 0; i < ct; ++i) 594 if (self->sws_bp_addrs[i] == 0) { 595 self->sws_bp_addrs[i] = addr; 596 static struct bp_callbacks cbs = { 597 .on_hit = sw_singlestep_bp_on_hit, 598 }; 599 struct breakpoint *bp 600 = insert_breakpoint(proc, addr, NULL); 601 breakpoint_set_callbacks(bp, &cbs); 602 return 0; 603 } 604 605 assert(!"Too many sw singlestep breakpoints!"); 606 abort(); 607} 608 609static int 610singlestep(struct process_stopping_handler *self) 611{ 612 struct process *proc = self->task_enabling_breakpoint; 613 614 struct sw_singlestep_data data = { self }; 615 switch (arch_sw_singlestep(self->task_enabling_breakpoint, 616 self->breakpoint_being_enabled, 617 &sw_singlestep_add_bp, &data)) { 618 case SWS_HW: 619 /* Otherwise do the default action: singlestep. */ 620 debug(1, "PTRACE_SINGLESTEP"); 621 if (ptrace(PTRACE_SINGLESTEP, proc->pid, 0, 0)) { 622 perror("PTRACE_SINGLESTEP"); 623 return -1; 624 } 625 return 0; 626 627 case SWS_OK: 628 return 0; 629 630 case SWS_FAIL: 631 return -1; 632 } 633 abort(); 634} 635 636static void 637post_singlestep(struct process_stopping_handler *self, 638 struct Event **eventp) 639{ 640 continue_for_sigstop_delivery(&self->pids); 641 642 if (*eventp != NULL && (*eventp)->type == EVENT_BREAKPOINT) 643 *eventp = NULL; // handled 644 645 struct process *proc = self->task_enabling_breakpoint; 646 647 remove_sw_breakpoints(proc); 648 self->breakpoint_being_enabled = NULL; 649} 650 651static void 652singlestep_error(struct process_stopping_handler *self) 653{ 654 struct process *teb = self->task_enabling_breakpoint; 655 struct breakpoint *sbp = self->breakpoint_being_enabled; 656 fprintf(stderr, "%d couldn't continue when handling %s (%p) at %p\n", 657 teb->pid, breakpoint_name(sbp), sbp->addr, 658 get_instruction_pointer(teb)); 659 delete_breakpoint(teb->leader, sbp->addr); 660} 661 662static void 663pt_continue(struct process_stopping_handler *self) 664{ 665 struct process *teb = self->task_enabling_breakpoint; 666 debug(1, "PTRACE_CONT"); 667 ptrace(PTRACE_CONT, teb->pid, 0, 0); 668} 669 670static void 671pt_singlestep(struct process_stopping_handler *self) 672{ 673 if (singlestep(self) < 0) 674 singlestep_error(self); 675} 676 677static void 678disable_and(struct process_stopping_handler *self, 679 void (*do_this)(struct process_stopping_handler *self)) 680{ 681 struct process *teb = self->task_enabling_breakpoint; 682 debug(DEBUG_PROCESS, "all stopped, now singlestep/cont %d", teb->pid); 683 if (self->breakpoint_being_enabled->enabled) 684 disable_breakpoint(teb, self->breakpoint_being_enabled); 685 (do_this)(self); 686 self->state = PSH_SINGLESTEP; 687} 688 689void 690linux_ptrace_disable_and_singlestep(struct process_stopping_handler *self) 691{ 692 disable_and(self, &pt_singlestep); 693} 694 695void 696linux_ptrace_disable_and_continue(struct process_stopping_handler *self) 697{ 698 disable_and(self, &pt_continue); 699} 700 701/* This event handler is installed when we are in the process of 702 * stopping the whole thread group to do the pointer re-enablement for 703 * one of the threads. We pump all events to the queue for later 704 * processing while we wait for all the threads to stop. When this 705 * happens, we let the re-enablement thread to PTRACE_SINGLESTEP, 706 * re-enable, and continue everyone. */ 707static Event * 708process_stopping_on_event(struct event_handler *super, Event *event) 709{ 710 struct process_stopping_handler *self = (void *)super; 711 struct process *task = event->proc; 712 struct process *leader = task->leader; 713 struct process *teb = self->task_enabling_breakpoint; 714 715 debug(DEBUG_PROCESS, 716 "process_stopping_on_event: pid %d; event type %d; state %d", 717 task->pid, event->type, self->state); 718 719 struct pid_task *task_info = get_task_info(&self->pids, task->pid); 720 if (task_info == NULL) 721 fprintf(stderr, "new task??? %d\n", task->pid); 722 handle_stopping_event(task_info, &event); 723 724 int state = self->state; 725 int event_to_queue = !event_exit_or_none_p(event); 726 727 /* Deactivate the entry if the task exits. */ 728 if (event_exit_p(event) && task_info != NULL) 729 task_info->pid = 0; 730 731 /* Always handle sysrets. Whether sysret occurred and what 732 * sys it rets from may need to be determined based on process 733 * stack, so we need to keep that in sync with reality. Note 734 * that we don't continue the process after the sysret is 735 * handled. See continue_after_syscall. */ 736 if (event != NULL && event->type == EVENT_SYSRET) { 737 debug(1, "%d LT_EV_SYSRET", event->proc->pid); 738 event_to_queue = 0; 739 task_info->sysret = 1; 740 } 741 742 switch (state) { 743 case PSH_STOPPING: 744 /* If everyone is stopped, singlestep. */ 745 if (each_task(leader, NULL, &task_blocked, 746 &self->pids) == NULL) { 747 (self->on_all_stopped)(self); 748 state = self->state; 749 } 750 break; 751 752 case PSH_SINGLESTEP: 753 /* In singlestep state, breakpoint signifies that we 754 * have now stepped, and can re-enable the breakpoint. */ 755 if (event != NULL && task == teb) { 756 757 /* If this was caused by a real breakpoint, as 758 * opposed to a singlestep, assume that it's 759 * an artificial breakpoint installed for some 760 * reason for the re-enablement. In that case 761 * handle it. */ 762 if (event->type == EVENT_BREAKPOINT) { 763 arch_addr_t ip 764 = get_instruction_pointer(task); 765 struct breakpoint *other 766 = address2bpstruct(leader, ip); 767 if (other != NULL) 768 breakpoint_on_hit(other, task); 769 } 770 771 /* If we got SIGNAL instead of BREAKPOINT, 772 * then this is not singlestep at all. */ 773 if (event->type == EVENT_SIGNAL) { 774 do_singlestep: 775 if (singlestep(self) < 0) { 776 singlestep_error(self); 777 post_singlestep(self, &event); 778 goto psh_sinking; 779 } 780 break; 781 } else { 782 switch ((self->keep_stepping_p)(self)) { 783 case CBS_FAIL: 784 /* XXX handle me */ 785 case CBS_STOP: 786 break; 787 case CBS_CONT: 788 /* Sink singlestep event. */ 789 if (event->type == EVENT_BREAKPOINT) 790 event = NULL; 791 goto do_singlestep; 792 } 793 } 794 795 /* Re-enable the breakpoint that we are 796 * stepping over. */ 797 struct breakpoint *sbp = self->breakpoint_being_enabled; 798 if (sbp->enabled) 799 enable_breakpoint(teb, sbp); 800 801 post_singlestep(self, &event); 802 goto psh_sinking; 803 } 804 break; 805 806 psh_sinking: 807 state = self->state = PSH_SINKING; 808 /* Fall through. */ 809 case PSH_SINKING: 810 if (await_sigstop_delivery(&self->pids, task_info, event)) 811 process_stopping_done(self, leader); 812 break; 813 814 case PSH_UGLY_WORKAROUND: 815 if (event == NULL) 816 break; 817 if (event->type == EVENT_BREAKPOINT) { 818 undo_breakpoint(event, leader); 819 if (task == teb) 820 self->task_enabling_breakpoint = NULL; 821 } 822 if (self->task_enabling_breakpoint == NULL 823 && all_stops_accountable(&self->pids)) { 824 undo_breakpoint(event, leader); 825 detach_process(leader); 826 event = NULL; // handled 827 } 828 } 829 830 if (event != NULL && event_to_queue) { 831 enque_event(event); 832 event = NULL; // sink the event 833 } 834 835 return event; 836} 837 838static void 839process_stopping_destroy(struct event_handler *super) 840{ 841 struct process_stopping_handler *self = (void *)super; 842 free(self->pids.tasks); 843} 844 845static enum callback_status 846no(struct process_stopping_handler *self) 847{ 848 return CBS_STOP; 849} 850 851int 852process_install_stopping_handler(struct process *proc, struct breakpoint *sbp, 853 void (*as)(struct process_stopping_handler *), 854 enum callback_status (*ks) 855 (struct process_stopping_handler *), 856 enum callback_status (*uw) 857 (struct process_stopping_handler *)) 858{ 859 debug(DEBUG_FUNCTION, 860 "process_install_stopping_handler: pid=%d", proc->pid); 861 862 struct process_stopping_handler *handler = calloc(sizeof(*handler), 1); 863 if (handler == NULL) 864 return -1; 865 866 if (as == NULL) 867 as = &linux_ptrace_disable_and_singlestep; 868 if (ks == NULL) 869 ks = &no; 870 if (uw == NULL) 871 uw = &no; 872 873 handler->super.on_event = process_stopping_on_event; 874 handler->super.destroy = process_stopping_destroy; 875 handler->task_enabling_breakpoint = proc; 876 handler->breakpoint_being_enabled = sbp; 877 handler->on_all_stopped = as; 878 handler->keep_stepping_p = ks; 879 handler->ugly_workaround_p = uw; 880 881 install_event_handler(proc->leader, &handler->super); 882 883 if (each_task(proc->leader, NULL, &send_sigstop, 884 &handler->pids) != NULL) { 885 destroy_event_handler(proc); 886 return -1; 887 } 888 889 /* And deliver the first fake event, in case all the 890 * conditions are already fulfilled. */ 891 Event ev = { 892 .type = EVENT_NONE, 893 .proc = proc, 894 }; 895 process_stopping_on_event(&handler->super, &ev); 896 897 return 0; 898} 899 900void 901continue_after_breakpoint(struct process *proc, struct breakpoint *sbp) 902{ 903 debug(DEBUG_PROCESS, 904 "continue_after_breakpoint: pid=%d, addr=%p", 905 proc->pid, sbp->addr); 906 907 set_instruction_pointer(proc, sbp->addr); 908 909 if (sbp->enabled == 0) { 910 continue_process(proc->pid); 911 } else if (process_install_stopping_handler 912 (proc, sbp, NULL, NULL, NULL) < 0) { 913 perror("process_stopping_handler_create"); 914 /* Carry on not bothering to re-enable. */ 915 continue_process(proc->pid); 916 } 917} 918 919/** 920 * Ltrace exit. When we are about to exit, we have to go through all 921 * the processes, stop them all, remove all the breakpoints, and then 922 * detach the processes that we attached to using -p. If we left the 923 * other tasks running, they might hit stray return breakpoints and 924 * produce artifacts, so we better stop everyone, even if it's a bit 925 * of extra work. 926 */ 927struct ltrace_exiting_handler 928{ 929 struct event_handler super; 930 struct pid_set pids; 931}; 932 933static Event * 934ltrace_exiting_on_event(struct event_handler *super, Event *event) 935{ 936 struct ltrace_exiting_handler *self = (void *)super; 937 struct process *task = event->proc; 938 struct process *leader = task->leader; 939 940 debug(DEBUG_PROCESS, 941 "ltrace_exiting_on_event: pid %d; event type %d", 942 task->pid, event->type); 943 944 struct pid_task *task_info = get_task_info(&self->pids, task->pid); 945 handle_stopping_event(task_info, &event); 946 947 if (event != NULL && event->type == EVENT_BREAKPOINT) 948 undo_breakpoint(event, leader); 949 950 if (await_sigstop_delivery(&self->pids, task_info, event) 951 && all_stops_accountable(&self->pids)) 952 detach_process(leader); 953 954 /* Sink all non-exit events. We are about to exit, so we 955 * don't bother with queuing them. */ 956 if (event_exit_or_none_p(event)) 957 return event; 958 959 return NULL; 960} 961 962static void 963ltrace_exiting_destroy(struct event_handler *super) 964{ 965 struct ltrace_exiting_handler *self = (void *)super; 966 free(self->pids.tasks); 967} 968 969static int 970ltrace_exiting_install_handler(struct process *proc) 971{ 972 /* Only install to leader. */ 973 if (proc->leader != proc) 974 return 0; 975 976 /* Perhaps we are already installed, if the user passed 977 * several -p options that are tasks of one process. */ 978 if (proc->event_handler != NULL 979 && proc->event_handler->on_event == <race_exiting_on_event) 980 return 0; 981 982 /* If stopping handler is already present, let it do the 983 * work. */ 984 if (proc->event_handler != NULL) { 985 assert(proc->event_handler->on_event 986 == &process_stopping_on_event); 987 struct process_stopping_handler *other 988 = (void *)proc->event_handler; 989 other->exiting = 1; 990 return 0; 991 } 992 993 struct ltrace_exiting_handler *handler 994 = calloc(sizeof(*handler), 1); 995 if (handler == NULL) { 996 perror("malloc exiting handler"); 997 fatal: 998 /* XXXXXXXXXXXXXXXXXXX fixme */ 999 return -1; 1000 } 1001 1002 handler->super.on_event = ltrace_exiting_on_event; 1003 handler->super.destroy = ltrace_exiting_destroy; 1004 install_event_handler(proc->leader, &handler->super); 1005 1006 if (each_task(proc->leader, NULL, &send_sigstop, 1007 &handler->pids) != NULL) 1008 goto fatal; 1009 1010 return 0; 1011} 1012 1013/* 1014 * When the traced process vforks, it's suspended until the child 1015 * process calls _exit or exec*. In the meantime, the two share the 1016 * address space. 1017 * 1018 * The child process should only ever call _exit or exec*, but we 1019 * can't count on that (it's not the role of ltrace to policy, but to 1020 * observe). In any case, we will _at least_ have to deal with 1021 * removal of vfork return breakpoint (which we have to smuggle back 1022 * in, so that the parent can see it, too), and introduction of exec* 1023 * return breakpoint. Since we already have both breakpoint actions 1024 * to deal with, we might as well support it all. 1025 * 1026 * The gist is that we pretend that the child is in a thread group 1027 * with its parent, and handle it as a multi-threaded case, with the 1028 * exception that we know that the parent is blocked, and don't 1029 * attempt to stop it. When the child execs, we undo the setup. 1030 */ 1031 1032struct process_vfork_handler 1033{ 1034 struct event_handler super; 1035 arch_addr_t bp_addr; 1036}; 1037 1038static Event * 1039process_vfork_on_event(struct event_handler *super, Event *event) 1040{ 1041 debug(DEBUG_PROCESS, 1042 "process_vfork_on_event: pid %d; event type %d", 1043 event->proc->pid, event->type); 1044 1045 struct process_vfork_handler *self = (void *)super; 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 struct breakpoint **found 1062 = DICT_FIND(event->proc->leader->breakpoints, 1063 &self->bp_addr, 1064 struct breakpoint *); 1065 if (found != NULL) 1066 assert((*found)->libsym == NULL); 1067 /* We don't mind failing that, it's not a big 1068 * deal to not display one extra vfork return. */ 1069 insert_breakpoint(event->proc->parent, 1070 self->bp_addr, NULL); 1071 } 1072 1073 continue_process(event->proc->parent->pid); 1074 1075 /* Remove the leader that we artificially set up 1076 * earlier. */ 1077 change_process_leader(event->proc, event->proc); 1078 destroy_event_handler(event->proc); 1079 1080 default: 1081 ; 1082 } 1083 1084 return event; 1085} 1086 1087void 1088continue_after_vfork(struct process *proc) 1089{ 1090 debug(DEBUG_PROCESS, "continue_after_vfork: pid=%d", proc->pid); 1091 struct process_vfork_handler *handler = calloc(sizeof(*handler), 1); 1092 if (handler == NULL) { 1093 perror("malloc vfork handler"); 1094 /* Carry on not bothering to treat the process as 1095 * necessary. */ 1096 continue_process(proc->parent->pid); 1097 return; 1098 } 1099 1100 /* We must set up custom event handler, so that we see 1101 * exec/exit events for the task itself. */ 1102 handler->super.on_event = process_vfork_on_event; 1103 install_event_handler(proc, &handler->super); 1104 1105 /* Make sure that the child is sole thread. */ 1106 assert(proc->leader == proc); 1107 assert(proc->next == NULL || proc->next->leader != proc); 1108 1109 /* Make sure that the child's parent is properly set up. */ 1110 assert(proc->parent != NULL); 1111 assert(proc->parent->leader != NULL); 1112 1113 change_process_leader(proc, proc->parent->leader); 1114} 1115 1116static int 1117is_mid_stopping(struct process *proc) 1118{ 1119 return proc != NULL 1120 && proc->event_handler != NULL 1121 && proc->event_handler->on_event == &process_stopping_on_event; 1122} 1123 1124void 1125continue_after_syscall(struct process *proc, int sysnum, int ret_p) 1126{ 1127 /* Don't continue if we are mid-stopping. */ 1128 if (ret_p && (is_mid_stopping(proc) || is_mid_stopping(proc->leader))) { 1129 debug(DEBUG_PROCESS, 1130 "continue_after_syscall: don't continue %d", 1131 proc->pid); 1132 return; 1133 } 1134 continue_process(proc->pid); 1135} 1136 1137void 1138continue_after_exec(struct process *proc) 1139{ 1140 continue_process(proc->pid); 1141 1142 /* After the exec, we expect to hit the first executable 1143 * instruction. 1144 * 1145 * XXX TODO It would be nice to have this removed, but then we 1146 * need to do that also for initial call to wait_for_proc in 1147 * execute_program. In that case we could generate a 1148 * EVENT_FIRST event or something, or maybe this could somehow 1149 * be rolled into EVENT_NEW. */ 1150 wait_for_proc(proc->pid); 1151 continue_process(proc->pid); 1152} 1153 1154/* If ltrace gets SIGINT, the processes directly or indirectly run by 1155 * ltrace get it too. We just have to wait long enough for the signal 1156 * to be delivered and the process terminated, which we notice and 1157 * exit ltrace, too. So there's not much we need to do there. We 1158 * want to keep tracing those processes as usual, in case they just 1159 * SIG_IGN the SIGINT to do their shutdown etc. 1160 * 1161 * For processes ran on the background, we want to install an exit 1162 * handler that stops all the threads, removes all breakpoints, and 1163 * detaches. 1164 */ 1165void 1166os_ltrace_exiting(void) 1167{ 1168 struct opt_p_t *it; 1169 for (it = opt_p; it != NULL; it = it->next) { 1170 struct process *proc = pid2proc(it->pid); 1171 if (proc == NULL || proc->leader == NULL) 1172 continue; 1173 if (ltrace_exiting_install_handler(proc->leader) < 0) 1174 fprintf(stderr, 1175 "Couldn't install exiting handler for %d.\n", 1176 proc->pid); 1177 } 1178} 1179 1180int 1181os_ltrace_exiting_sighandler(void) 1182{ 1183 extern int linux_in_waitpid; 1184 if (linux_in_waitpid) { 1185 os_ltrace_exiting(); 1186 return 1; 1187 } 1188 return 0; 1189} 1190 1191size_t 1192umovebytes(struct process *proc, void *addr, void *laddr, size_t len) 1193{ 1194 1195 union { 1196 long a; 1197 char c[sizeof(long)]; 1198 } a; 1199 int started = 0; 1200 size_t offset = 0, bytes_read = 0; 1201 1202 while (offset < len) { 1203 a.a = ptrace(PTRACE_PEEKTEXT, proc->pid, addr + offset, 0); 1204 if (a.a == -1 && errno) { 1205 if (started && errno == EIO) 1206 return bytes_read; 1207 else 1208 return -1; 1209 } 1210 started = 1; 1211 1212 if (len - offset >= sizeof(long)) { 1213 memcpy(laddr + offset, &a.c[0], sizeof(long)); 1214 bytes_read += sizeof(long); 1215 } 1216 else { 1217 memcpy(laddr + offset, &a.c[0], len - offset); 1218 bytes_read += (len - offset); 1219 } 1220 offset += sizeof(long); 1221 } 1222 1223 return bytes_read; 1224} 1225