1 /* Generate a core file for the inferior process. 2 3 Copyright (C) 2001-2020 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 "elf-bfd.h" 22 #include "infcall.h" 23 #include "inferior.h" 24 #include "gdbcore.h" 25 #include "objfiles.h" 26 #include "solib.h" 27 #include "symfile.h" 28 #include "arch-utils.h" 29 #include "completer.h" 30 #include "gcore.h" 31 #include "cli/cli-decode.h" 32 #include <fcntl.h> 33 #include "regcache.h" 34 #include "regset.h" 35 #include "gdb_bfd.h" 36 #include "readline/tilde.h" 37 #include <algorithm> 38 #include "gdbsupport/gdb_unlinker.h" 39 #include "gdbsupport/byte-vector.h" 40 #include "gdbsupport/scope-exit.h" 41 42 /* The largest amount of memory to read from the target at once. We 43 must throttle it to limit the amount of memory used by GDB during 44 generate-core-file for programs with large resident data. */ 45 #define MAX_COPY_BYTES (1024 * 1024) 46 47 static const char *default_gcore_target (void); 48 static enum bfd_architecture default_gcore_arch (void); 49 static unsigned long default_gcore_mach (void); 50 static int gcore_memory_sections (bfd *); 51 52 /* create_gcore_bfd -- helper for gcore_command (exported). 53 Open a new bfd core file for output, and return the handle. */ 54 55 gdb_bfd_ref_ptr 56 create_gcore_bfd (const char *filename) 57 { 58 gdb_bfd_ref_ptr obfd (gdb_bfd_openw (filename, default_gcore_target ())); 59 60 if (obfd == NULL) 61 error (_("Failed to open '%s' for output."), filename); 62 bfd_set_format (obfd.get (), bfd_core); 63 bfd_set_arch_mach (obfd.get (), default_gcore_arch (), default_gcore_mach ()); 64 return obfd; 65 } 66 67 /* write_gcore_file_1 -- do the actual work of write_gcore_file. */ 68 69 static void 70 write_gcore_file_1 (bfd *obfd) 71 { 72 gdb::unique_xmalloc_ptr<char> note_data; 73 int note_size = 0; 74 asection *note_sec = NULL; 75 76 /* An external target method must build the notes section. */ 77 /* FIXME: uweigand/2011-10-06: All architectures that support core file 78 generation should be converted to gdbarch_make_corefile_notes; at that 79 point, the target vector method can be removed. */ 80 if (!gdbarch_make_corefile_notes_p (target_gdbarch ())) 81 note_data.reset (target_make_corefile_notes (obfd, ¬e_size)); 82 else 83 note_data.reset (gdbarch_make_corefile_notes (target_gdbarch (), obfd, 84 ¬e_size)); 85 86 if (note_data == NULL || note_size == 0) 87 error (_("Target does not support core file generation.")); 88 89 /* Create the note section. */ 90 note_sec = bfd_make_section_anyway_with_flags (obfd, "note0", 91 SEC_HAS_CONTENTS 92 | SEC_READONLY 93 | SEC_ALLOC); 94 if (note_sec == NULL) 95 error (_("Failed to create 'note' section for corefile: %s"), 96 bfd_errmsg (bfd_get_error ())); 97 98 bfd_set_section_vma (note_sec, 0); 99 bfd_set_section_alignment (note_sec, 0); 100 bfd_set_section_size (note_sec, note_size); 101 102 /* Now create the memory/load sections. */ 103 if (gcore_memory_sections (obfd) == 0) 104 error (_("gcore: failed to get corefile memory sections from target.")); 105 106 /* Write out the contents of the note section. */ 107 if (!bfd_set_section_contents (obfd, note_sec, note_data.get (), 0, 108 note_size)) 109 warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ())); 110 } 111 112 /* write_gcore_file -- helper for gcore_command (exported). 113 Compose and write the corefile data to the core file. */ 114 115 void 116 write_gcore_file (bfd *obfd) 117 { 118 target_prepare_to_generate_core (); 119 SCOPE_EXIT { target_done_generating_core (); }; 120 write_gcore_file_1 (obfd); 121 } 122 123 /* gcore_command -- implements the 'gcore' command. 124 Generate a core file from the inferior process. */ 125 126 static void 127 gcore_command (const char *args, int from_tty) 128 { 129 gdb::unique_xmalloc_ptr<char> corefilename; 130 131 /* No use generating a corefile without a target process. */ 132 if (!target_has_execution) 133 noprocess (); 134 135 if (args && *args) 136 corefilename.reset (tilde_expand (args)); 137 else 138 { 139 /* Default corefile name is "core.PID". */ 140 corefilename.reset (xstrprintf ("core.%d", inferior_ptid.pid ())); 141 } 142 143 if (info_verbose) 144 fprintf_filtered (gdb_stdout, 145 "Opening corefile '%s' for output.\n", 146 corefilename.get ()); 147 148 if (target_supports_dumpcore ()) 149 target_dumpcore (corefilename.get ()); 150 else 151 { 152 /* Open the output file. */ 153 gdb_bfd_ref_ptr obfd (create_gcore_bfd (corefilename.get ())); 154 155 /* Arrange to unlink the file on failure. */ 156 gdb::unlinker unlink_file (corefilename.get ()); 157 158 /* Call worker function. */ 159 write_gcore_file (obfd.get ()); 160 161 /* Succeeded. */ 162 unlink_file.keep (); 163 } 164 165 fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename.get ()); 166 } 167 168 static unsigned long 169 default_gcore_mach (void) 170 { 171 #if 1 /* See if this even matters... */ 172 return 0; 173 #else 174 175 const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ()); 176 177 if (bfdarch != NULL) 178 return bfdarch->mach; 179 if (exec_bfd == NULL) 180 error (_("Can't find default bfd machine type (need execfile).")); 181 182 return bfd_get_mach (exec_bfd); 183 #endif /* 1 */ 184 } 185 186 static enum bfd_architecture 187 default_gcore_arch (void) 188 { 189 const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ()); 190 191 if (bfdarch != NULL) 192 return bfdarch->arch; 193 if (exec_bfd == NULL) 194 error (_("Can't find bfd architecture for corefile (need execfile).")); 195 196 return bfd_get_arch (exec_bfd); 197 } 198 199 static const char * 200 default_gcore_target (void) 201 { 202 /* The gdbarch may define a target to use for core files. */ 203 if (gdbarch_gcore_bfd_target_p (target_gdbarch ())) 204 return gdbarch_gcore_bfd_target (target_gdbarch ()); 205 206 /* Otherwise, try to fall back to the exec_bfd target. This will probably 207 not work for non-ELF targets. */ 208 if (exec_bfd == NULL) 209 return NULL; 210 else 211 return bfd_get_target (exec_bfd); 212 } 213 214 /* Derive a reasonable stack segment by unwinding the target stack, 215 and store its limits in *BOTTOM and *TOP. Return non-zero if 216 successful. */ 217 218 static int 219 derive_stack_segment (bfd_vma *bottom, bfd_vma *top) 220 { 221 struct frame_info *fi, *tmp_fi; 222 223 gdb_assert (bottom); 224 gdb_assert (top); 225 226 /* Can't succeed without stack and registers. */ 227 if (!target_has_stack || !target_has_registers) 228 return 0; 229 230 /* Can't succeed without current frame. */ 231 fi = get_current_frame (); 232 if (fi == NULL) 233 return 0; 234 235 /* Save frame pointer of TOS frame. */ 236 *top = get_frame_base (fi); 237 /* If current stack pointer is more "inner", use that instead. */ 238 if (gdbarch_inner_than (get_frame_arch (fi), get_frame_sp (fi), *top)) 239 *top = get_frame_sp (fi); 240 241 /* Find prev-most frame. */ 242 while ((tmp_fi = get_prev_frame (fi)) != NULL) 243 fi = tmp_fi; 244 245 /* Save frame pointer of prev-most frame. */ 246 *bottom = get_frame_base (fi); 247 248 /* Now canonicalize their order, so that BOTTOM is a lower address 249 (as opposed to a lower stack frame). */ 250 if (*bottom > *top) 251 { 252 bfd_vma tmp_vma; 253 254 tmp_vma = *top; 255 *top = *bottom; 256 *bottom = tmp_vma; 257 } 258 259 return 1; 260 } 261 262 /* call_target_sbrk -- 263 helper function for derive_heap_segment. */ 264 265 static bfd_vma 266 call_target_sbrk (int sbrk_arg) 267 { 268 struct objfile *sbrk_objf; 269 struct gdbarch *gdbarch; 270 bfd_vma top_of_heap; 271 struct value *target_sbrk_arg; 272 struct value *sbrk_fn, *ret; 273 bfd_vma tmp; 274 275 if (lookup_minimal_symbol ("sbrk", NULL, NULL).minsym != NULL) 276 { 277 sbrk_fn = find_function_in_inferior ("sbrk", &sbrk_objf); 278 if (sbrk_fn == NULL) 279 return (bfd_vma) 0; 280 } 281 else if (lookup_minimal_symbol ("_sbrk", NULL, NULL).minsym != NULL) 282 { 283 sbrk_fn = find_function_in_inferior ("_sbrk", &sbrk_objf); 284 if (sbrk_fn == NULL) 285 return (bfd_vma) 0; 286 } 287 else 288 return (bfd_vma) 0; 289 290 gdbarch = sbrk_objf->arch (); 291 target_sbrk_arg = value_from_longest (builtin_type (gdbarch)->builtin_int, 292 sbrk_arg); 293 gdb_assert (target_sbrk_arg); 294 ret = call_function_by_hand (sbrk_fn, NULL, target_sbrk_arg); 295 if (ret == NULL) 296 return (bfd_vma) 0; 297 298 tmp = value_as_long (ret); 299 if ((LONGEST) tmp <= 0 || (LONGEST) tmp == 0xffffffff) 300 return (bfd_vma) 0; 301 302 top_of_heap = tmp; 303 return top_of_heap; 304 } 305 306 /* Derive a reasonable heap segment for ABFD by looking at sbrk and 307 the static data sections. Store its limits in *BOTTOM and *TOP. 308 Return non-zero if successful. */ 309 310 static int 311 derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top) 312 { 313 bfd_vma top_of_data_memory = 0; 314 bfd_vma top_of_heap = 0; 315 bfd_size_type sec_size; 316 bfd_vma sec_vaddr; 317 asection *sec; 318 319 gdb_assert (bottom); 320 gdb_assert (top); 321 322 /* This function depends on being able to call a function in the 323 inferior. */ 324 if (!target_has_execution) 325 return 0; 326 327 /* The following code assumes that the link map is arranged as 328 follows (low to high addresses): 329 330 --------------------------------- 331 | text sections | 332 --------------------------------- 333 | data sections (including bss) | 334 --------------------------------- 335 | heap | 336 --------------------------------- */ 337 338 for (sec = abfd->sections; sec; sec = sec->next) 339 { 340 if (bfd_section_flags (sec) & SEC_DATA 341 || strcmp (".bss", bfd_section_name (sec)) == 0) 342 { 343 sec_vaddr = bfd_section_vma (sec); 344 sec_size = bfd_section_size (sec); 345 if (sec_vaddr + sec_size > top_of_data_memory) 346 top_of_data_memory = sec_vaddr + sec_size; 347 } 348 } 349 350 top_of_heap = call_target_sbrk (0); 351 if (top_of_heap == (bfd_vma) 0) 352 return 0; 353 354 /* Return results. */ 355 if (top_of_heap > top_of_data_memory) 356 { 357 *bottom = top_of_data_memory; 358 *top = top_of_heap; 359 return 1; 360 } 361 362 /* No additional heap space needs to be saved. */ 363 return 0; 364 } 365 366 static void 367 make_output_phdrs (bfd *obfd, asection *osec, void *ignored) 368 { 369 int p_flags = 0; 370 int p_type = 0; 371 372 /* FIXME: these constants may only be applicable for ELF. */ 373 if (startswith (bfd_section_name (osec), "load")) 374 p_type = PT_LOAD; 375 else if (startswith (bfd_section_name (osec), "note")) 376 p_type = PT_NOTE; 377 else 378 p_type = PT_NULL; 379 380 p_flags |= PF_R; /* Segment is readable. */ 381 if (!(bfd_section_flags (osec) & SEC_READONLY)) 382 p_flags |= PF_W; /* Segment is writable. */ 383 if (bfd_section_flags (osec) & SEC_CODE) 384 p_flags |= PF_X; /* Segment is executable. */ 385 386 bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec); 387 } 388 389 /* find_memory_region_ftype implementation. DATA is 'bfd *' for the core file 390 GDB is creating. */ 391 392 static int 393 gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read, 394 int write, int exec, int modified, void *data) 395 { 396 bfd *obfd = (bfd *) data; 397 asection *osec; 398 flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD; 399 400 /* If the memory segment has no permissions set, ignore it, otherwise 401 when we later try to access it for read/write, we'll get an error 402 or jam the kernel. */ 403 if (read == 0 && write == 0 && exec == 0 && modified == 0) 404 { 405 if (info_verbose) 406 { 407 fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at %s\n", 408 plongest (size), paddress (target_gdbarch (), vaddr)); 409 } 410 411 return 0; 412 } 413 414 if (write == 0 && modified == 0 && !solib_keep_data_in_core (vaddr, size)) 415 { 416 /* See if this region of memory lies inside a known file on disk. 417 If so, we can avoid copying its contents by clearing SEC_LOAD. */ 418 struct obj_section *objsec; 419 420 for (objfile *objfile : current_program_space->objfiles ()) 421 ALL_OBJFILE_OSECTIONS (objfile, objsec) 422 { 423 bfd *abfd = objfile->obfd; 424 asection *asec = objsec->the_bfd_section; 425 bfd_vma align = (bfd_vma) 1 << bfd_section_alignment (asec); 426 bfd_vma start = obj_section_addr (objsec) & -align; 427 bfd_vma end = (obj_section_endaddr (objsec) + align - 1) & -align; 428 429 /* Match if either the entire memory region lies inside the 430 section (i.e. a mapping covering some pages of a large 431 segment) or the entire section lies inside the memory region 432 (i.e. a mapping covering multiple small sections). 433 434 This BFD was synthesized from reading target memory, 435 we don't want to omit that. */ 436 if (objfile->separate_debug_objfile_backlink == NULL 437 && ((vaddr >= start && vaddr + size <= end) 438 || (start >= vaddr && end <= vaddr + size)) 439 && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY)) 440 { 441 flags &= ~(SEC_LOAD | SEC_HAS_CONTENTS); 442 goto keep; /* Break out of two nested for loops. */ 443 } 444 } 445 446 keep:; 447 } 448 449 if (write == 0) 450 flags |= SEC_READONLY; 451 452 if (exec) 453 flags |= SEC_CODE; 454 else 455 flags |= SEC_DATA; 456 457 osec = bfd_make_section_anyway_with_flags (obfd, "load", flags); 458 if (osec == NULL) 459 { 460 warning (_("Couldn't make gcore segment: %s"), 461 bfd_errmsg (bfd_get_error ())); 462 return 1; 463 } 464 465 if (info_verbose) 466 { 467 fprintf_filtered (gdb_stdout, "Save segment, %s bytes at %s\n", 468 plongest (size), paddress (target_gdbarch (), vaddr)); 469 } 470 471 bfd_set_section_size (osec, size); 472 bfd_set_section_vma (osec, vaddr); 473 bfd_set_section_lma (osec, 0); 474 return 0; 475 } 476 477 int 478 objfile_find_memory_regions (struct target_ops *self, 479 find_memory_region_ftype func, void *obfd) 480 { 481 /* Use objfile data to create memory sections. */ 482 struct obj_section *objsec; 483 bfd_vma temp_bottom, temp_top; 484 485 /* Call callback function for each objfile section. */ 486 for (objfile *objfile : current_program_space->objfiles ()) 487 ALL_OBJFILE_OSECTIONS (objfile, objsec) 488 { 489 asection *isec = objsec->the_bfd_section; 490 flagword flags = bfd_section_flags (isec); 491 492 /* Separate debug info files are irrelevant for gcore. */ 493 if (objfile->separate_debug_objfile_backlink != NULL) 494 continue; 495 496 if ((flags & SEC_ALLOC) || (flags & SEC_LOAD)) 497 { 498 int size = bfd_section_size (isec); 499 int ret; 500 501 ret = (*func) (obj_section_addr (objsec), size, 502 1, /* All sections will be readable. */ 503 (flags & SEC_READONLY) == 0, /* Writable. */ 504 (flags & SEC_CODE) != 0, /* Executable. */ 505 1, /* MODIFIED is unknown, pass it as true. */ 506 obfd); 507 if (ret != 0) 508 return ret; 509 } 510 } 511 512 /* Make a stack segment. */ 513 if (derive_stack_segment (&temp_bottom, &temp_top)) 514 (*func) (temp_bottom, temp_top - temp_bottom, 515 1, /* Stack section will be readable. */ 516 1, /* Stack section will be writable. */ 517 0, /* Stack section will not be executable. */ 518 1, /* Stack section will be modified. */ 519 obfd); 520 521 /* Make a heap segment. */ 522 if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top)) 523 (*func) (temp_bottom, temp_top - temp_bottom, 524 1, /* Heap section will be readable. */ 525 1, /* Heap section will be writable. */ 526 0, /* Heap section will not be executable. */ 527 1, /* Heap section will be modified. */ 528 obfd); 529 530 return 0; 531 } 532 533 static void 534 gcore_copy_callback (bfd *obfd, asection *osec, void *ignored) 535 { 536 bfd_size_type size, total_size = bfd_section_size (osec); 537 file_ptr offset = 0; 538 539 /* Read-only sections are marked; we don't have to copy their contents. */ 540 if ((bfd_section_flags (osec) & SEC_LOAD) == 0) 541 return; 542 543 /* Only interested in "load" sections. */ 544 if (!startswith (bfd_section_name (osec), "load")) 545 return; 546 547 size = std::min (total_size, (bfd_size_type) MAX_COPY_BYTES); 548 gdb::byte_vector memhunk (size); 549 550 while (total_size > 0) 551 { 552 if (size > total_size) 553 size = total_size; 554 555 if (target_read_memory (bfd_section_vma (osec) + offset, 556 memhunk.data (), size) != 0) 557 { 558 warning (_("Memory read failed for corefile " 559 "section, %s bytes at %s."), 560 plongest (size), 561 paddress (target_gdbarch (), bfd_section_vma (osec))); 562 break; 563 } 564 if (!bfd_set_section_contents (obfd, osec, memhunk.data (), 565 offset, size)) 566 { 567 warning (_("Failed to write corefile contents (%s)."), 568 bfd_errmsg (bfd_get_error ())); 569 break; 570 } 571 572 total_size -= size; 573 offset += size; 574 } 575 } 576 577 static int 578 gcore_memory_sections (bfd *obfd) 579 { 580 /* Try gdbarch method first, then fall back to target method. */ 581 if (!gdbarch_find_memory_regions_p (target_gdbarch ()) 582 || gdbarch_find_memory_regions (target_gdbarch (), 583 gcore_create_callback, obfd) != 0) 584 { 585 if (target_find_memory_regions (gcore_create_callback, obfd) != 0) 586 return 0; /* FIXME: error return/msg? */ 587 } 588 589 /* Record phdrs for section-to-segment mapping. */ 590 bfd_map_over_sections (obfd, make_output_phdrs, NULL); 591 592 /* Copy memory region contents. */ 593 bfd_map_over_sections (obfd, gcore_copy_callback, NULL); 594 595 return 1; 596 } 597 598 void _initialize_gcore (); 599 void 600 _initialize_gcore () 601 { 602 add_com ("generate-core-file", class_files, gcore_command, _("\ 603 Save a core file with the current state of the debugged process.\n\ 604 Usage: generate-core-file [FILENAME]\n\ 605 Argument is optional filename. Default filename is 'core.PROCESS_ID'.")); 606 607 add_com_alias ("gcore", "generate-core-file", class_files, 1); 608 } 609