1 /* Low-level child interface to ptrace.
3 Copyright (C) 1988-2015 Free Software Foundation, Inc.
5 This file is part of GDB.
7 This program is free software; you can redistribute it and/or modify
8 it under the terms of the GNU General Public License as published by
9 the Free Software Foundation; either version 3 of the License, or
10 (at your option) any later version.
12 This program is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 GNU General Public License for more details.
17 You should have received a copy of the GNU General Public License
18 along with this program. If not, see <http://www.gnu.org/licenses/>. */
27 #include "nat/gdb_ptrace.h"
31 #include "inf-ptrace.h"
32 #include "inf-child.h"
33 #include "gdbthread.h"
37 #ifdef PT_GET_PROCESS_STATE
39 /* Target hook for follow_fork. On entry and at return inferior_ptid is
40 the ptid of the followed inferior. */
43 inf_ptrace_follow_fork (struct target_ops *ops, int follow_child,
48 struct thread_info *tp = inferior_thread ();
49 pid_t child_pid = ptid_get_pid (tp->pending_follow.value.related_pid);
51 /* Breakpoints have already been detached from the child by
54 if (ptrace (PT_DETACH, child_pid, (PTRACE_TYPE_ARG3)1, 0) == -1)
55 perror_with_name (("ptrace"));
62 inf_ptrace_insert_fork_catchpoint (struct target_ops *self, int pid)
68 inf_ptrace_remove_fork_catchpoint (struct target_ops *self, int pid)
73 #endif /* PT_GET_PROCESS_STATE */
76 /* Prepare to be traced. */
81 /* "Trace me, Dr. Memory!" */
82 ptrace (PT_TRACE_ME, 0, (PTRACE_TYPE_ARG3)0, 0);
85 /* Start a new inferior Unix child process. EXEC_FILE is the file to
86 run, ALLARGS is a string containing the arguments to the program.
87 ENV is the environment vector to pass. If FROM_TTY is non-zero, be
91 inf_ptrace_create_inferior (struct target_ops *ops,
92 char *exec_file, char *allargs, char **env,
97 /* Do not change either targets above or the same target if already present.
98 The reason is the target stack is shared across multiple inferiors. */
99 int ops_already_pushed = target_is_pushed (ops);
100 struct cleanup *back_to = make_cleanup (null_cleanup, NULL);
102 if (! ops_already_pushed)
104 /* Clear possible core file with its process_stratum. */
106 make_cleanup_unpush_target (ops);
109 pid = fork_inferior (exec_file, allargs, env, inf_ptrace_me, NULL,
112 discard_cleanups (back_to);
114 startup_inferior (START_INFERIOR_TRAPS_EXPECTED);
116 /* On some targets, there must be some explicit actions taken after
117 the inferior has been started up. */
118 target_post_startup_inferior (pid_to_ptid (pid));
121 #ifdef PT_GET_PROCESS_STATE
124 inf_ptrace_post_startup_inferior (struct target_ops *self, ptid_t pid)
128 /* Set the initial event mask. */
129 memset (&pe, 0, sizeof pe);
130 pe.pe_set_event |= PTRACE_FORK;
131 if (ptrace (PT_SET_EVENT_MASK, ptid_get_pid (pid),
132 (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)
133 perror_with_name (("ptrace"));
138 /* Clean up a rotting corpse of an inferior after it died. */
141 inf_ptrace_mourn_inferior (struct target_ops *ops)
145 /* Wait just one more time to collect the inferior's exit status.
146 Do not check whether this succeeds though, since we may be
147 dealing with a process that we attached to. Such a process will
148 only report its exit status to its original parent. */
149 waitpid (ptid_get_pid (inferior_ptid), &status, 0);
151 inf_child_mourn_inferior (ops);
154 /* Attach to the process specified by ARGS. If FROM_TTY is non-zero,
155 be chatty about it. */
158 inf_ptrace_attach (struct target_ops *ops, const char *args, int from_tty)
162 struct inferior *inf;
164 /* Do not change either targets above or the same target if already present.
165 The reason is the target stack is shared across multiple inferiors. */
166 int ops_already_pushed = target_is_pushed (ops);
167 struct cleanup *back_to = make_cleanup (null_cleanup, NULL);
169 pid = parse_pid_to_attach (args);
171 if (pid == getpid ()) /* Trying to masturbate? */
172 error (_("I refuse to debug myself!"));
174 if (! ops_already_pushed)
176 /* target_pid_to_str already uses the target. Also clear possible core
177 file with its process_stratum. */
179 make_cleanup_unpush_target (ops);
184 exec_file = get_exec_file (0);
187 printf_unfiltered (_("Attaching to program: %s, %s\n"), exec_file,
188 target_pid_to_str (pid_to_ptid (pid)));
190 printf_unfiltered (_("Attaching to %s\n"),
191 target_pid_to_str (pid_to_ptid (pid)));
193 gdb_flush (gdb_stdout);
198 ptrace (PT_ATTACH, pid, (PTRACE_TYPE_ARG3)0, 0);
200 perror_with_name (("ptrace"));
202 error (_("This system does not support attaching to a process"));
205 inf = current_inferior ();
206 inferior_appeared (inf, pid);
207 inf->attach_flag = 1;
208 inferior_ptid = pid_to_ptid (pid);
210 /* Always add a main thread. If some target extends the ptrace
211 target, it should decorate the ptid later with more info. */
212 add_thread_silent (inferior_ptid);
214 discard_cleanups (back_to);
217 #ifdef PT_GET_PROCESS_STATE
220 inf_ptrace_post_attach (struct target_ops *self, int pid)
224 /* Set the initial event mask. */
225 memset (&pe, 0, sizeof pe);
226 pe.pe_set_event |= PTRACE_FORK;
227 if (ptrace (PT_SET_EVENT_MASK, pid,
228 (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)
229 perror_with_name (("ptrace"));
234 /* Detach from the inferior, optionally passing it the signal
235 specified by ARGS. If FROM_TTY is non-zero, be chatty about it. */
238 inf_ptrace_detach (struct target_ops *ops, const char *args, int from_tty)
240 pid_t pid = ptid_get_pid (inferior_ptid);
245 char *exec_file = get_exec_file (0);
248 printf_unfiltered (_("Detaching from program: %s, %s\n"), exec_file,
249 target_pid_to_str (pid_to_ptid (pid)));
250 gdb_flush (gdb_stdout);
256 /* We'd better not have left any breakpoints in the program or it'll
257 die when it hits one. Also note that this may only work if we
258 previously attached to the inferior. It *might* work if we
259 started the process ourselves. */
261 ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3)1, sig);
263 perror_with_name (("ptrace"));
265 error (_("This system does not support detaching from a process"));
268 inferior_ptid = null_ptid;
269 detach_inferior (pid);
271 inf_child_maybe_unpush_target (ops);
274 /* Kill the inferior. */
277 inf_ptrace_kill (struct target_ops *ops)
279 pid_t pid = ptid_get_pid (inferior_ptid);
285 ptrace (PT_KILL, pid, (PTRACE_TYPE_ARG3)0, 0);
286 waitpid (pid, &status, 0);
288 target_mourn_inferior ();
291 /* Interrupt the inferior. */
294 inf_ptrace_interrupt (struct target_ops *self, ptid_t ptid)
296 /* Send a SIGINT to the process group. This acts just like the user
297 typed a ^C on the controlling terminal. Note that using a
298 negative process number in kill() is a System V-ism. The proper
299 BSD interface is killpg(). However, all modern BSDs support the
300 System V interface too. */
301 kill (-inferior_process_group (), SIGINT);
304 /* Return which PID to pass to ptrace in order to observe/control the
305 tracee identified by PTID. */
308 get_ptrace_pid (ptid_t ptid)
312 /* If we have an LWPID to work with, use it. Otherwise, we're
313 dealing with a non-threaded program/target. */
314 pid = ptid_get_lwp (ptid);
316 pid = ptid_get_pid (ptid);
320 /* Resume execution of thread PTID, or all threads if PTID is -1. If
321 STEP is nonzero, single-step it. If SIGNAL is nonzero, give it
325 inf_ptrace_resume (struct target_ops *ops,
326 ptid_t ptid, int step, enum gdb_signal signal)
331 if (ptid_equal (minus_one_ptid, ptid))
332 /* Resume all threads. Traditionally ptrace() only supports
333 single-threaded processes, so simply resume the inferior. */
334 pid = ptid_get_pid (inferior_ptid);
336 pid = get_ptrace_pid (ptid);
338 if (catch_syscall_enabled () > 0)
339 request = PT_SYSCALL;
341 request = PT_CONTINUE;
345 /* If this system does not support PT_STEP, a higher level
346 function will have called single_step() to transmute the step
347 request into a continue request (by setting breakpoints on
348 all possible successor instructions), so we don't have to
349 worry about that here. */
353 /* An address of (PTRACE_TYPE_ARG3)1 tells ptrace to continue from
354 where it was. If GDB wanted it to start some other way, we have
355 already written a new program counter value to the child. */
357 ptrace (request, pid, (PTRACE_TYPE_ARG3)1, gdb_signal_to_host (signal));
359 perror_with_name (("ptrace"));
362 /* Wait for the child specified by PTID to do something. Return the
363 process ID of the child, or MINUS_ONE_PTID in case of error; store
364 the status in *OURSTATUS. */
367 inf_ptrace_wait (struct target_ops *ops,
368 ptid_t ptid, struct target_waitstatus *ourstatus, int options)
371 int status, save_errno;
379 pid = waitpid (ptid_get_pid (ptid), &status, 0);
382 while (pid == -1 && errno == EINTR);
384 clear_sigint_trap ();
388 fprintf_unfiltered (gdb_stderr,
389 _("Child process unexpectedly missing: %s.\n"),
390 safe_strerror (save_errno));
392 /* Claim it exited with unknown signal. */
393 ourstatus->kind = TARGET_WAITKIND_SIGNALLED;
394 ourstatus->value.sig = GDB_SIGNAL_UNKNOWN;
395 return inferior_ptid;
398 /* Ignore terminated detached child processes. */
399 if (!WIFSTOPPED (status) && pid != ptid_get_pid (inferior_ptid))
404 #ifdef PT_GET_PROCESS_STATE
405 if (WIFSTOPPED (status))
410 if (ptrace (PT_GET_PROCESS_STATE, pid,
411 (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)
412 perror_with_name (("ptrace"));
414 switch (pe.pe_report_event)
417 ourstatus->kind = TARGET_WAITKIND_FORKED;
418 ourstatus->value.related_pid = pid_to_ptid (pe.pe_other_pid);
420 /* Make sure the other end of the fork is stopped too. */
421 fpid = waitpid (pe.pe_other_pid, &status, 0);
423 perror_with_name (("waitpid"));
425 if (ptrace (PT_GET_PROCESS_STATE, fpid,
426 (PTRACE_TYPE_ARG3)&pe, sizeof pe) == -1)
427 perror_with_name (("ptrace"));
429 gdb_assert (pe.pe_report_event == PTRACE_FORK);
430 gdb_assert (pe.pe_other_pid == pid);
431 if (fpid == ptid_get_pid (inferior_ptid))
433 ourstatus->value.related_pid = pid_to_ptid (pe.pe_other_pid);
434 return pid_to_ptid (fpid);
437 return pid_to_ptid (pid);
442 store_waitstatus (ourstatus, status);
443 return pid_to_ptid (pid);
446 /* Implement the to_xfer_partial target_ops method. */
448 static enum target_xfer_status
449 inf_ptrace_xfer_partial (struct target_ops *ops, enum target_object object,
450 const char *annex, gdb_byte *readbuf,
451 const gdb_byte *writebuf,
452 ULONGEST offset, ULONGEST len, ULONGEST *xfered_len)
454 pid_t pid = ptid_get_pid (inferior_ptid);
458 case TARGET_OBJECT_MEMORY:
460 /* OpenBSD 3.1, NetBSD 1.6 and FreeBSD 5.0 have a new PT_IO
461 request that promises to be much more efficient in reading
462 and writing data in the traced process's address space. */
464 struct ptrace_io_desc piod;
466 /* NOTE: We assume that there are no distinct address spaces
467 for instruction and data. However, on OpenBSD 3.9 and
468 later, PIOD_WRITE_D doesn't allow changing memory that's
469 mapped read-only. Since most code segments will be
470 read-only, using PIOD_WRITE_D will prevent us from
471 inserting breakpoints, so we use PIOD_WRITE_I instead. */
472 piod.piod_op = writebuf ? PIOD_WRITE_I : PIOD_READ_D;
473 piod.piod_addr = writebuf ? (void *) writebuf : readbuf;
474 piod.piod_offs = (void *) (long) offset;
478 if (ptrace (PT_IO, pid, (caddr_t)&piod, 0) == 0)
480 /* Return the actual number of bytes read or written. */
481 *xfered_len = piod.piod_len;
482 return (piod.piod_len == 0) ? TARGET_XFER_EOF : TARGET_XFER_OK;
484 /* If the PT_IO request is somehow not supported, fallback on
485 using PT_WRITE_D/PT_READ_D. Otherwise we will return zero
486 to indicate failure. */
488 return TARGET_XFER_EOF;
494 PTRACE_TYPE_RET word;
495 gdb_byte byte[sizeof (PTRACE_TYPE_RET)];
497 ULONGEST rounded_offset;
498 ULONGEST partial_len;
500 /* Round the start offset down to the next long word
502 rounded_offset = offset & -(ULONGEST) sizeof (PTRACE_TYPE_RET);
504 /* Since ptrace will transfer a single word starting at that
505 rounded_offset the partial_len needs to be adjusted down to
506 that (remember this function only does a single transfer).
507 Should the required length be even less, adjust it down
509 partial_len = (rounded_offset + sizeof (PTRACE_TYPE_RET)) - offset;
510 if (partial_len > len)
515 /* If OFFSET:PARTIAL_LEN is smaller than
516 ROUNDED_OFFSET:WORDSIZE then a read/modify write will
517 be needed. Read in the entire word. */
518 if (rounded_offset < offset
519 || (offset + partial_len
520 < rounded_offset + sizeof (PTRACE_TYPE_RET)))
521 /* Need part of initial word -- fetch it. */
522 buffer.word = ptrace (PT_READ_I, pid,
523 (PTRACE_TYPE_ARG3)(uintptr_t)
526 /* Copy data to be written over corresponding part of
528 memcpy (buffer.byte + (offset - rounded_offset),
529 writebuf, partial_len);
532 ptrace (PT_WRITE_D, pid,
533 (PTRACE_TYPE_ARG3)(uintptr_t)rounded_offset,
537 /* Using the appropriate one (I or D) is necessary for
538 Gould NP1, at least. */
540 ptrace (PT_WRITE_I, pid,
541 (PTRACE_TYPE_ARG3)(uintptr_t)rounded_offset,
544 return TARGET_XFER_EOF;
551 buffer.word = ptrace (PT_READ_I, pid,
552 (PTRACE_TYPE_ARG3)(uintptr_t)rounded_offset,
555 return TARGET_XFER_EOF;
556 /* Copy appropriate bytes out of the buffer. */
557 memcpy (readbuf, buffer.byte + (offset - rounded_offset),
561 *xfered_len = partial_len;
562 return TARGET_XFER_OK;
565 case TARGET_OBJECT_UNWIND_TABLE:
566 return TARGET_XFER_E_IO;
568 case TARGET_OBJECT_AUXV:
569 #if defined (PT_IO) && defined (PIOD_READ_AUXV)
570 /* OpenBSD 4.5 has a new PIOD_READ_AUXV operation for the PT_IO
571 request that allows us to read the auxilliary vector. Other
572 BSD's may follow if they feel the need to support PIE. */
574 struct ptrace_io_desc piod;
577 return TARGET_XFER_E_IO;
578 piod.piod_op = PIOD_READ_AUXV;
579 piod.piod_addr = readbuf;
580 piod.piod_offs = (void *) (long) offset;
584 if (ptrace (PT_IO, pid, (caddr_t)&piod, 0) == 0)
586 /* Return the actual number of bytes read or written. */
587 *xfered_len = piod.piod_len;
588 return (piod.piod_len == 0) ? TARGET_XFER_EOF : TARGET_XFER_OK;
592 return TARGET_XFER_E_IO;
594 case TARGET_OBJECT_WCOOKIE:
595 return TARGET_XFER_E_IO;
598 return TARGET_XFER_E_IO;
602 /* Return non-zero if the thread specified by PTID is alive. */
605 inf_ptrace_thread_alive (struct target_ops *ops, ptid_t ptid)
607 /* ??? Is kill the right way to do this? */
608 return (kill (ptid_get_pid (ptid), 0) != -1);
611 /* Print status information about what we're accessing. */
614 inf_ptrace_files_info (struct target_ops *ignore)
616 struct inferior *inf = current_inferior ();
618 printf_filtered (_("\tUsing the running image of %s %s.\n"),
619 inf->attach_flag ? "attached" : "child",
620 target_pid_to_str (inferior_ptid));
624 inf_ptrace_pid_to_str (struct target_ops *ops, ptid_t ptid)
626 return normal_pid_to_str (ptid);
629 #if defined (PT_IO) && defined (PIOD_READ_AUXV)
631 /* Read one auxv entry from *READPTR, not reading locations >= ENDPTR.
632 Return 0 if *READPTR is already at the end of the buffer.
633 Return -1 if there is insufficient buffer for a whole entry.
634 Return 1 if an entry was read into *TYPEP and *VALP. */
637 inf_ptrace_auxv_parse (struct target_ops *ops, gdb_byte **readptr,
638 gdb_byte *endptr, CORE_ADDR *typep, CORE_ADDR *valp)
640 struct type *int_type = builtin_type (target_gdbarch ())->builtin_int;
641 struct type *ptr_type = builtin_type (target_gdbarch ())->builtin_data_ptr;
642 const int sizeof_auxv_type = TYPE_LENGTH (int_type);
643 const int sizeof_auxv_val = TYPE_LENGTH (ptr_type);
644 enum bfd_endian byte_order = gdbarch_byte_order (target_gdbarch ());
645 gdb_byte *ptr = *readptr;
650 if (endptr - ptr < 2 * sizeof_auxv_val)
653 *typep = extract_unsigned_integer (ptr, sizeof_auxv_type, byte_order);
654 ptr += sizeof_auxv_val; /* Alignment. */
655 *valp = extract_unsigned_integer (ptr, sizeof_auxv_val, byte_order);
656 ptr += sizeof_auxv_val;
664 /* Create a prototype ptrace target. The client can override it with
668 inf_ptrace_target (void)
670 struct target_ops *t = inf_child_target ();
672 t->to_attach = inf_ptrace_attach;
673 t->to_detach = inf_ptrace_detach;
674 t->to_resume = inf_ptrace_resume;
675 t->to_wait = inf_ptrace_wait;
676 t->to_files_info = inf_ptrace_files_info;
677 t->to_kill = inf_ptrace_kill;
678 t->to_create_inferior = inf_ptrace_create_inferior;
679 #ifdef PT_GET_PROCESS_STATE
680 t->to_follow_fork = inf_ptrace_follow_fork;
681 t->to_insert_fork_catchpoint = inf_ptrace_insert_fork_catchpoint;
682 t->to_remove_fork_catchpoint = inf_ptrace_remove_fork_catchpoint;
683 t->to_post_startup_inferior = inf_ptrace_post_startup_inferior;
684 t->to_post_attach = inf_ptrace_post_attach;
686 t->to_mourn_inferior = inf_ptrace_mourn_inferior;
687 t->to_thread_alive = inf_ptrace_thread_alive;
688 t->to_pid_to_str = inf_ptrace_pid_to_str;
689 t->to_interrupt = inf_ptrace_interrupt;
690 t->to_xfer_partial = inf_ptrace_xfer_partial;
691 #if defined (PT_IO) && defined (PIOD_READ_AUXV)
692 t->to_auxv_parse = inf_ptrace_auxv_parse;
699 /* Pointer to a function that returns the offset within the user area
700 where a particular register is stored. */
701 static CORE_ADDR (*inf_ptrace_register_u_offset)(struct gdbarch *, int, int);
703 /* Fetch register REGNUM from the inferior. */
706 inf_ptrace_fetch_register (struct regcache *regcache, int regnum)
708 struct gdbarch *gdbarch = get_regcache_arch (regcache);
711 PTRACE_TYPE_RET *buf;
714 /* This isn't really an address, but ptrace thinks of it as one. */
715 addr = inf_ptrace_register_u_offset (gdbarch, regnum, 0);
716 if (addr == (CORE_ADDR)-1
717 || gdbarch_cannot_fetch_register (gdbarch, regnum))
719 regcache_raw_supply (regcache, regnum, NULL);
723 /* Cater for systems like GNU/Linux, that implement threads as
724 separate processes. */
725 pid = ptid_get_lwp (inferior_ptid);
727 pid = ptid_get_pid (inferior_ptid);
729 size = register_size (gdbarch, regnum);
730 gdb_assert ((size % sizeof (PTRACE_TYPE_RET)) == 0);
731 buf = (long int *) alloca (size);
733 /* Read the register contents from the inferior a chunk at a time. */
734 for (i = 0; i < size / sizeof (PTRACE_TYPE_RET); i++)
737 buf[i] = ptrace (PT_READ_U, pid, (PTRACE_TYPE_ARG3)(uintptr_t)addr, 0);
739 error (_("Couldn't read register %s (#%d): %s."),
740 gdbarch_register_name (gdbarch, regnum),
741 regnum, safe_strerror (errno));
743 addr += sizeof (PTRACE_TYPE_RET);
745 regcache_raw_supply (regcache, regnum, buf);
748 /* Fetch register REGNUM from the inferior. If REGNUM is -1, do this
749 for all registers. */
752 inf_ptrace_fetch_registers (struct target_ops *ops,
753 struct regcache *regcache, int regnum)
757 regnum < gdbarch_num_regs (get_regcache_arch (regcache));
759 inf_ptrace_fetch_register (regcache, regnum);
761 inf_ptrace_fetch_register (regcache, regnum);
764 /* Store register REGNUM into the inferior. */
767 inf_ptrace_store_register (const struct regcache *regcache, int regnum)
769 struct gdbarch *gdbarch = get_regcache_arch (regcache);
772 PTRACE_TYPE_RET *buf;
775 /* This isn't really an address, but ptrace thinks of it as one. */
776 addr = inf_ptrace_register_u_offset (gdbarch, regnum, 1);
777 if (addr == (CORE_ADDR)-1
778 || gdbarch_cannot_store_register (gdbarch, regnum))
781 /* Cater for systems like GNU/Linux, that implement threads as
782 separate processes. */
783 pid = ptid_get_lwp (inferior_ptid);
785 pid = ptid_get_pid (inferior_ptid);
787 size = register_size (gdbarch, regnum);
788 gdb_assert ((size % sizeof (PTRACE_TYPE_RET)) == 0);
789 buf = (long int *) alloca (size);
791 /* Write the register contents into the inferior a chunk at a time. */
792 regcache_raw_collect (regcache, regnum, buf);
793 for (i = 0; i < size / sizeof (PTRACE_TYPE_RET); i++)
796 ptrace (PT_WRITE_U, pid, (PTRACE_TYPE_ARG3)(uintptr_t)addr, buf[i]);
798 error (_("Couldn't write register %s (#%d): %s."),
799 gdbarch_register_name (gdbarch, regnum),
800 regnum, safe_strerror (errno));
802 addr += sizeof (PTRACE_TYPE_RET);
806 /* Store register REGNUM back into the inferior. If REGNUM is -1, do
807 this for all registers. */
810 inf_ptrace_store_registers (struct target_ops *ops,
811 struct regcache *regcache, int regnum)
815 regnum < gdbarch_num_regs (get_regcache_arch (regcache));
817 inf_ptrace_store_register (regcache, regnum);
819 inf_ptrace_store_register (regcache, regnum);
822 /* Create a "traditional" ptrace target. REGISTER_U_OFFSET should be
823 a function returning the offset within the user area where a
824 particular register is stored. */
827 inf_ptrace_trad_target (CORE_ADDR (*register_u_offset)
828 (struct gdbarch *, int, int))
830 struct target_ops *t = inf_ptrace_target();
832 gdb_assert (register_u_offset);
833 inf_ptrace_register_u_offset = register_u_offset;
834 t->to_fetch_registers = inf_ptrace_fetch_registers;
835 t->to_store_registers = inf_ptrace_store_registers;