| 1 | /* Low-level child interface to ptrace. |
| 2 | |
| 3 | Copyright (C) 1988-2020 Free Software Foundation, Inc. |
| 4 | |
| 5 | This file is part of GDB. |
| 6 | |
| 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. |
| 11 | |
| 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. |
| 16 | |
| 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/>. */ |
| 19 | |
| 20 | #include "defs.h" |
| 21 | #include "command.h" |
| 22 | #include "inferior.h" |
| 23 | #include "inflow.h" |
| 24 | #include "terminal.h" |
| 25 | #include "gdbcore.h" |
| 26 | #include "regcache.h" |
| 27 | #include "nat/gdb_ptrace.h" |
| 28 | #include "gdbsupport/gdb_wait.h" |
| 29 | #include <signal.h> |
| 30 | |
| 31 | #include "inf-ptrace.h" |
| 32 | #include "inf-child.h" |
| 33 | #include "gdbthread.h" |
| 34 | #include "nat/fork-inferior.h" |
| 35 | #include "utils.h" |
| 36 | #include "gdbarch.h" |
| 37 | |
| 38 | \f |
| 39 | |
| 40 | static PTRACE_TYPE_RET |
| 41 | gdb_ptrace (PTRACE_TYPE_ARG1 request, ptid_t ptid, PTRACE_TYPE_ARG3 addr, |
| 42 | PTRACE_TYPE_ARG4 data) |
| 43 | { |
| 44 | #ifdef __NetBSD__ |
| 45 | return ptrace (request, ptid.pid (), addr, data); |
| 46 | #else |
| 47 | pid_t pid = get_ptrace_pid (ptid); |
| 48 | return ptrace (request, pid, addr, data); |
| 49 | #endif |
| 50 | } |
| 51 | |
| 52 | /* A unique_ptr helper to unpush a target. */ |
| 53 | |
| 54 | struct target_unpusher |
| 55 | { |
| 56 | void operator() (struct target_ops *ops) const |
| 57 | { |
| 58 | unpush_target (ops); |
| 59 | } |
| 60 | }; |
| 61 | |
| 62 | /* A unique_ptr that unpushes a target on destruction. */ |
| 63 | |
| 64 | typedef std::unique_ptr<struct target_ops, target_unpusher> target_unpush_up; |
| 65 | |
| 66 | \f |
| 67 | |
| 68 | inf_ptrace_target::~inf_ptrace_target () |
| 69 | {} |
| 70 | |
| 71 | \f |
| 72 | |
| 73 | /* Prepare to be traced. */ |
| 74 | |
| 75 | static void |
| 76 | inf_ptrace_me (void) |
| 77 | { |
| 78 | /* "Trace me, Dr. Memory!" */ |
| 79 | if (ptrace (PT_TRACE_ME, 0, (PTRACE_TYPE_ARG3) 0, 0) < 0) |
| 80 | trace_start_error_with_name ("ptrace"); |
| 81 | } |
| 82 | |
| 83 | /* Start a new inferior Unix child process. EXEC_FILE is the file to |
| 84 | run, ALLARGS is a string containing the arguments to the program. |
| 85 | ENV is the environment vector to pass. If FROM_TTY is non-zero, be |
| 86 | chatty about it. */ |
| 87 | |
| 88 | void |
| 89 | inf_ptrace_target::create_inferior (const char *exec_file, |
| 90 | const std::string &allargs, |
| 91 | char **env, int from_tty) |
| 92 | { |
| 93 | pid_t pid; |
| 94 | ptid_t ptid; |
| 95 | |
| 96 | /* Do not change either targets above or the same target if already present. |
| 97 | The reason is the target stack is shared across multiple inferiors. */ |
| 98 | int ops_already_pushed = target_is_pushed (this); |
| 99 | |
| 100 | target_unpush_up unpusher; |
| 101 | if (! ops_already_pushed) |
| 102 | { |
| 103 | /* Clear possible core file with its process_stratum. */ |
| 104 | push_target (this); |
| 105 | unpusher.reset (this); |
| 106 | } |
| 107 | |
| 108 | pid = fork_inferior (exec_file, allargs, env, inf_ptrace_me, NULL, |
| 109 | NULL, NULL, NULL); |
| 110 | |
| 111 | ptid = ptid_t (pid); |
| 112 | /* We have something that executes now. We'll be running through |
| 113 | the shell at this point (if startup-with-shell is true), but the |
| 114 | pid shouldn't change. */ |
| 115 | add_thread_silent (this, ptid); |
| 116 | |
| 117 | unpusher.release (); |
| 118 | |
| 119 | gdb_startup_inferior (pid, START_INFERIOR_TRAPS_EXPECTED); |
| 120 | |
| 121 | /* On some targets, there must be some explicit actions taken after |
| 122 | the inferior has been started up. */ |
| 123 | target_post_startup_inferior (ptid); |
| 124 | } |
| 125 | |
| 126 | /* Clean up a rotting corpse of an inferior after it died. */ |
| 127 | |
| 128 | void |
| 129 | inf_ptrace_target::mourn_inferior () |
| 130 | { |
| 131 | int status; |
| 132 | |
| 133 | /* Wait just one more time to collect the inferior's exit status. |
| 134 | Do not check whether this succeeds though, since we may be |
| 135 | dealing with a process that we attached to. Such a process will |
| 136 | only report its exit status to its original parent. */ |
| 137 | waitpid (inferior_ptid.pid (), &status, 0); |
| 138 | |
| 139 | inf_child_target::mourn_inferior (); |
| 140 | } |
| 141 | |
| 142 | /* Attach to the process specified by ARGS. If FROM_TTY is non-zero, |
| 143 | be chatty about it. */ |
| 144 | |
| 145 | void |
| 146 | inf_ptrace_target::attach (const char *args, int from_tty) |
| 147 | { |
| 148 | pid_t pid; |
| 149 | struct inferior *inf; |
| 150 | |
| 151 | /* Do not change either targets above or the same target if already present. |
| 152 | The reason is the target stack is shared across multiple inferiors. */ |
| 153 | int ops_already_pushed = target_is_pushed (this); |
| 154 | |
| 155 | pid = parse_pid_to_attach (args); |
| 156 | |
| 157 | if (pid == getpid ()) /* Trying to masturbate? */ |
| 158 | error (_("I refuse to debug myself!")); |
| 159 | |
| 160 | target_unpush_up unpusher; |
| 161 | if (! ops_already_pushed) |
| 162 | { |
| 163 | /* target_pid_to_str already uses the target. Also clear possible core |
| 164 | file with its process_stratum. */ |
| 165 | push_target (this); |
| 166 | unpusher.reset (this); |
| 167 | } |
| 168 | |
| 169 | if (from_tty) |
| 170 | { |
| 171 | const char *exec_file = get_exec_file (0); |
| 172 | |
| 173 | if (exec_file) |
| 174 | printf_unfiltered (_("Attaching to program: %s, %s\n"), exec_file, |
| 175 | target_pid_to_str (ptid_t (pid)).c_str ()); |
| 176 | else |
| 177 | printf_unfiltered (_("Attaching to %s\n"), |
| 178 | target_pid_to_str (ptid_t (pid)).c_str ()); |
| 179 | } |
| 180 | |
| 181 | #ifdef PT_ATTACH |
| 182 | errno = 0; |
| 183 | ptrace (PT_ATTACH, pid, (PTRACE_TYPE_ARG3)0, 0); |
| 184 | if (errno != 0) |
| 185 | perror_with_name (("ptrace")); |
| 186 | #else |
| 187 | error (_("This system does not support attaching to a process")); |
| 188 | #endif |
| 189 | |
| 190 | inf = current_inferior (); |
| 191 | inferior_appeared (inf, pid); |
| 192 | inf->attach_flag = 1; |
| 193 | inferior_ptid = ptid_t (pid); |
| 194 | |
| 195 | /* Always add a main thread. If some target extends the ptrace |
| 196 | target, it should decorate the ptid later with more info. */ |
| 197 | thread_info *thr = add_thread_silent (this, inferior_ptid); |
| 198 | /* Don't consider the thread stopped until we've processed its |
| 199 | initial SIGSTOP stop. */ |
| 200 | set_executing (this, thr->ptid, true); |
| 201 | |
| 202 | unpusher.release (); |
| 203 | } |
| 204 | |
| 205 | /* Detach from the inferior. If FROM_TTY is non-zero, be chatty about it. */ |
| 206 | |
| 207 | void |
| 208 | inf_ptrace_target::detach (inferior *inf, int from_tty) |
| 209 | { |
| 210 | pid_t pid = inferior_ptid.pid (); |
| 211 | |
| 212 | target_announce_detach (from_tty); |
| 213 | |
| 214 | #ifdef PT_DETACH |
| 215 | /* We'd better not have left any breakpoints in the program or it'll |
| 216 | die when it hits one. Also note that this may only work if we |
| 217 | previously attached to the inferior. It *might* work if we |
| 218 | started the process ourselves. */ |
| 219 | errno = 0; |
| 220 | ptrace (PT_DETACH, pid, (PTRACE_TYPE_ARG3)1, 0); |
| 221 | if (errno != 0) |
| 222 | perror_with_name (("ptrace")); |
| 223 | #else |
| 224 | error (_("This system does not support detaching from a process")); |
| 225 | #endif |
| 226 | |
| 227 | detach_success (inf); |
| 228 | } |
| 229 | |
| 230 | /* See inf-ptrace.h. */ |
| 231 | |
| 232 | void |
| 233 | inf_ptrace_target::detach_success (inferior *inf) |
| 234 | { |
| 235 | inferior_ptid = null_ptid; |
| 236 | detach_inferior (inf); |
| 237 | |
| 238 | maybe_unpush_target (); |
| 239 | } |
| 240 | |
| 241 | /* Kill the inferior. */ |
| 242 | |
| 243 | void |
| 244 | inf_ptrace_target::kill () |
| 245 | { |
| 246 | pid_t pid = inferior_ptid.pid (); |
| 247 | int status; |
| 248 | |
| 249 | if (pid == 0) |
| 250 | return; |
| 251 | |
| 252 | ptrace (PT_KILL, pid, (PTRACE_TYPE_ARG3)0, 0); |
| 253 | waitpid (pid, &status, 0); |
| 254 | |
| 255 | target_mourn_inferior (inferior_ptid); |
| 256 | } |
| 257 | |
| 258 | #ifndef __NetBSD__ |
| 259 | |
| 260 | /* See inf-ptrace.h. */ |
| 261 | |
| 262 | pid_t |
| 263 | get_ptrace_pid (ptid_t ptid) |
| 264 | { |
| 265 | pid_t pid; |
| 266 | |
| 267 | /* If we have an LWPID to work with, use it. Otherwise, we're |
| 268 | dealing with a non-threaded program/target. */ |
| 269 | pid = ptid.lwp (); |
| 270 | if (pid == 0) |
| 271 | pid = ptid.pid (); |
| 272 | return pid; |
| 273 | } |
| 274 | #endif |
| 275 | |
| 276 | /* Resume execution of thread PTID, or all threads if PTID is -1. If |
| 277 | STEP is nonzero, single-step it. If SIGNAL is nonzero, give it |
| 278 | that signal. */ |
| 279 | |
| 280 | void |
| 281 | inf_ptrace_target::resume (ptid_t ptid, int step, enum gdb_signal signal) |
| 282 | { |
| 283 | PTRACE_TYPE_ARG1 request; |
| 284 | |
| 285 | if (minus_one_ptid == ptid) |
| 286 | /* Resume all threads. Traditionally ptrace() only supports |
| 287 | single-threaded processes, so simply resume the inferior. */ |
| 288 | ptid = ptid_t (inferior_ptid.pid ()); |
| 289 | |
| 290 | if (catch_syscall_enabled () > 0) |
| 291 | request = PT_SYSCALL; |
| 292 | else |
| 293 | request = PT_CONTINUE; |
| 294 | |
| 295 | if (step) |
| 296 | { |
| 297 | /* If this system does not support PT_STEP, a higher level |
| 298 | function will have called the appropriate functions to transmute the |
| 299 | step request into a continue request (by setting breakpoints on |
| 300 | all possible successor instructions), so we don't have to |
| 301 | worry about that here. */ |
| 302 | request = PT_STEP; |
| 303 | } |
| 304 | |
| 305 | /* An address of (PTRACE_TYPE_ARG3)1 tells ptrace to continue from |
| 306 | where it was. If GDB wanted it to start some other way, we have |
| 307 | already written a new program counter value to the child. */ |
| 308 | errno = 0; |
| 309 | gdb_ptrace (request, ptid, (PTRACE_TYPE_ARG3)1, gdb_signal_to_host (signal)); |
| 310 | if (errno != 0) |
| 311 | perror_with_name (("ptrace")); |
| 312 | } |
| 313 | |
| 314 | /* Wait for the child specified by PTID to do something. Return the |
| 315 | process ID of the child, or MINUS_ONE_PTID in case of error; store |
| 316 | the status in *OURSTATUS. */ |
| 317 | |
| 318 | ptid_t |
| 319 | inf_ptrace_target::wait (ptid_t ptid, struct target_waitstatus *ourstatus, |
| 320 | int options) |
| 321 | { |
| 322 | pid_t pid; |
| 323 | int status, save_errno; |
| 324 | |
| 325 | do |
| 326 | { |
| 327 | set_sigint_trap (); |
| 328 | |
| 329 | do |
| 330 | { |
| 331 | pid = waitpid (ptid.pid (), &status, 0); |
| 332 | save_errno = errno; |
| 333 | } |
| 334 | while (pid == -1 && errno == EINTR); |
| 335 | |
| 336 | clear_sigint_trap (); |
| 337 | |
| 338 | if (pid == -1) |
| 339 | { |
| 340 | fprintf_unfiltered (gdb_stderr, |
| 341 | _("Child process unexpectedly missing: %s.\n"), |
| 342 | safe_strerror (save_errno)); |
| 343 | |
| 344 | /* Claim it exited with unknown signal. */ |
| 345 | ourstatus->kind = TARGET_WAITKIND_SIGNALLED; |
| 346 | ourstatus->value.sig = GDB_SIGNAL_UNKNOWN; |
| 347 | return inferior_ptid; |
| 348 | } |
| 349 | |
| 350 | /* Ignore terminated detached child processes. */ |
| 351 | if (!WIFSTOPPED (status) && pid != inferior_ptid.pid ()) |
| 352 | pid = -1; |
| 353 | } |
| 354 | while (pid == -1); |
| 355 | |
| 356 | store_waitstatus (ourstatus, status); |
| 357 | return ptid_t (pid); |
| 358 | } |
| 359 | |
| 360 | /* Transfer data via ptrace into process PID's memory from WRITEBUF, or |
| 361 | from process PID's memory into READBUF. Start at target address ADDR |
| 362 | and transfer up to LEN bytes. Exactly one of READBUF and WRITEBUF must |
| 363 | be non-null. Return the number of transferred bytes. */ |
| 364 | |
| 365 | static ULONGEST |
| 366 | inf_ptrace_peek_poke (ptid_t ptid, gdb_byte *readbuf, |
| 367 | const gdb_byte *writebuf, |
| 368 | ULONGEST addr, ULONGEST len) |
| 369 | { |
| 370 | ULONGEST n; |
| 371 | unsigned int chunk; |
| 372 | |
| 373 | /* We transfer aligned words. Thus align ADDR down to a word |
| 374 | boundary and determine how many bytes to skip at the |
| 375 | beginning. */ |
| 376 | ULONGEST skip = addr & (sizeof (PTRACE_TYPE_RET) - 1); |
| 377 | addr -= skip; |
| 378 | |
| 379 | for (n = 0; |
| 380 | n < len; |
| 381 | n += chunk, addr += sizeof (PTRACE_TYPE_RET), skip = 0) |
| 382 | { |
| 383 | /* Restrict to a chunk that fits in the current word. */ |
| 384 | chunk = std::min (sizeof (PTRACE_TYPE_RET) - skip, len - n); |
| 385 | |
| 386 | /* Use a union for type punning. */ |
| 387 | union |
| 388 | { |
| 389 | PTRACE_TYPE_RET word; |
| 390 | gdb_byte byte[sizeof (PTRACE_TYPE_RET)]; |
| 391 | } buf; |
| 392 | |
| 393 | /* Read the word, also when doing a partial word write. */ |
| 394 | if (readbuf != NULL || chunk < sizeof (PTRACE_TYPE_RET)) |
| 395 | { |
| 396 | errno = 0; |
| 397 | buf.word = gdb_ptrace (PT_READ_I, ptid, |
| 398 | (PTRACE_TYPE_ARG3)(uintptr_t) addr, 0); |
| 399 | if (errno != 0) |
| 400 | break; |
| 401 | if (readbuf != NULL) |
| 402 | memcpy (readbuf + n, buf.byte + skip, chunk); |
| 403 | } |
| 404 | if (writebuf != NULL) |
| 405 | { |
| 406 | memcpy (buf.byte + skip, writebuf + n, chunk); |
| 407 | errno = 0; |
| 408 | gdb_ptrace (PT_WRITE_D, ptid, (PTRACE_TYPE_ARG3)(uintptr_t) addr, |
| 409 | buf.word); |
| 410 | if (errno != 0) |
| 411 | { |
| 412 | /* Using the appropriate one (I or D) is necessary for |
| 413 | Gould NP1, at least. */ |
| 414 | errno = 0; |
| 415 | gdb_ptrace (PT_WRITE_I, ptid, (PTRACE_TYPE_ARG3)(uintptr_t) addr, |
| 416 | buf.word); |
| 417 | if (errno != 0) |
| 418 | break; |
| 419 | } |
| 420 | } |
| 421 | } |
| 422 | |
| 423 | return n; |
| 424 | } |
| 425 | |
| 426 | /* Implement the to_xfer_partial target_ops method. */ |
| 427 | |
| 428 | enum target_xfer_status |
| 429 | inf_ptrace_target::xfer_partial (enum target_object object, |
| 430 | const char *annex, gdb_byte *readbuf, |
| 431 | const gdb_byte *writebuf, |
| 432 | ULONGEST offset, ULONGEST len, ULONGEST *xfered_len) |
| 433 | { |
| 434 | ptid_t ptid = inferior_ptid; |
| 435 | |
| 436 | switch (object) |
| 437 | { |
| 438 | case TARGET_OBJECT_MEMORY: |
| 439 | #ifdef PT_IO |
| 440 | /* OpenBSD 3.1, NetBSD 1.6 and FreeBSD 5.0 have a new PT_IO |
| 441 | request that promises to be much more efficient in reading |
| 442 | and writing data in the traced process's address space. */ |
| 443 | { |
| 444 | struct ptrace_io_desc piod; |
| 445 | |
| 446 | /* NOTE: We assume that there are no distinct address spaces |
| 447 | for instruction and data. However, on OpenBSD 3.9 and |
| 448 | later, PIOD_WRITE_D doesn't allow changing memory that's |
| 449 | mapped read-only. Since most code segments will be |
| 450 | read-only, using PIOD_WRITE_D will prevent us from |
| 451 | inserting breakpoints, so we use PIOD_WRITE_I instead. */ |
| 452 | piod.piod_op = writebuf ? PIOD_WRITE_I : PIOD_READ_D; |
| 453 | piod.piod_addr = writebuf ? (void *) writebuf : readbuf; |
| 454 | piod.piod_offs = (void *) (long) offset; |
| 455 | piod.piod_len = len; |
| 456 | |
| 457 | errno = 0; |
| 458 | if (gdb_ptrace (PT_IO, ptid, (caddr_t)&piod, 0) == 0) |
| 459 | { |
| 460 | /* Return the actual number of bytes read or written. */ |
| 461 | *xfered_len = piod.piod_len; |
| 462 | return (piod.piod_len == 0) ? TARGET_XFER_EOF : TARGET_XFER_OK; |
| 463 | } |
| 464 | /* If the PT_IO request is somehow not supported, fallback on |
| 465 | using PT_WRITE_D/PT_READ_D. Otherwise we will return zero |
| 466 | to indicate failure. */ |
| 467 | if (errno != EINVAL) |
| 468 | return TARGET_XFER_EOF; |
| 469 | } |
| 470 | #endif |
| 471 | *xfered_len = inf_ptrace_peek_poke (ptid, readbuf, writebuf, |
| 472 | offset, len); |
| 473 | return *xfered_len != 0 ? TARGET_XFER_OK : TARGET_XFER_EOF; |
| 474 | |
| 475 | case TARGET_OBJECT_UNWIND_TABLE: |
| 476 | return TARGET_XFER_E_IO; |
| 477 | |
| 478 | case TARGET_OBJECT_AUXV: |
| 479 | #if defined (PT_IO) && defined (PIOD_READ_AUXV) |
| 480 | /* OpenBSD 4.5 has a new PIOD_READ_AUXV operation for the PT_IO |
| 481 | request that allows us to read the auxilliary vector. Other |
| 482 | BSD's may follow if they feel the need to support PIE. */ |
| 483 | { |
| 484 | struct ptrace_io_desc piod; |
| 485 | |
| 486 | if (writebuf) |
| 487 | return TARGET_XFER_E_IO; |
| 488 | piod.piod_op = PIOD_READ_AUXV; |
| 489 | piod.piod_addr = readbuf; |
| 490 | piod.piod_offs = (void *) (long) offset; |
| 491 | piod.piod_len = len; |
| 492 | |
| 493 | errno = 0; |
| 494 | if (gdb_ptrace (PT_IO, ptid, (caddr_t)&piod, 0) == 0) |
| 495 | { |
| 496 | /* Return the actual number of bytes read or written. */ |
| 497 | *xfered_len = piod.piod_len; |
| 498 | return (piod.piod_len == 0) ? TARGET_XFER_EOF : TARGET_XFER_OK; |
| 499 | } |
| 500 | } |
| 501 | #endif |
| 502 | return TARGET_XFER_E_IO; |
| 503 | |
| 504 | case TARGET_OBJECT_WCOOKIE: |
| 505 | return TARGET_XFER_E_IO; |
| 506 | |
| 507 | default: |
| 508 | return TARGET_XFER_E_IO; |
| 509 | } |
| 510 | } |
| 511 | |
| 512 | /* Return non-zero if the thread specified by PTID is alive. */ |
| 513 | |
| 514 | bool |
| 515 | inf_ptrace_target::thread_alive (ptid_t ptid) |
| 516 | { |
| 517 | /* ??? Is kill the right way to do this? */ |
| 518 | return (::kill (ptid.pid (), 0) != -1); |
| 519 | } |
| 520 | |
| 521 | /* Print status information about what we're accessing. */ |
| 522 | |
| 523 | void |
| 524 | inf_ptrace_target::files_info () |
| 525 | { |
| 526 | struct inferior *inf = current_inferior (); |
| 527 | |
| 528 | printf_filtered (_("\tUsing the running image of %s %s.\n"), |
| 529 | inf->attach_flag ? "attached" : "child", |
| 530 | target_pid_to_str (inferior_ptid).c_str ()); |
| 531 | } |
| 532 | |
| 533 | std::string |
| 534 | inf_ptrace_target::pid_to_str (ptid_t ptid) |
| 535 | { |
| 536 | return normal_pid_to_str (ptid); |
| 537 | } |