gcore.c revision 1.7
1/* Generate a core file for the inferior process. 2 3 Copyright (C) 2001-2017 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 "common/gdb_unlinker.h" 39 40/* The largest amount of memory to read from the target at once. We 41 must throttle it to limit the amount of memory used by GDB during 42 generate-core-file for programs with large resident data. */ 43#define MAX_COPY_BYTES (1024 * 1024) 44 45static const char *default_gcore_target (void); 46static enum bfd_architecture default_gcore_arch (void); 47static unsigned long default_gcore_mach (void); 48static int gcore_memory_sections (bfd *); 49 50/* create_gcore_bfd -- helper for gcore_command (exported). 51 Open a new bfd core file for output, and return the handle. */ 52 53gdb_bfd_ref_ptr 54create_gcore_bfd (const char *filename) 55{ 56 gdb_bfd_ref_ptr obfd (gdb_bfd_openw (filename, default_gcore_target ())); 57 58 if (obfd == NULL) 59 error (_("Failed to open '%s' for output."), filename); 60 bfd_set_format (obfd.get (), bfd_core); 61 bfd_set_arch_mach (obfd.get (), default_gcore_arch (), default_gcore_mach ()); 62 return obfd; 63} 64 65/* write_gcore_file_1 -- do the actual work of write_gcore_file. */ 66 67static void 68write_gcore_file_1 (bfd *obfd) 69{ 70 struct cleanup *cleanup; 71 void *note_data = NULL; 72 int note_size = 0; 73 asection *note_sec = NULL; 74 75 /* An external target method must build the notes section. */ 76 /* FIXME: uweigand/2011-10-06: All architectures that support core file 77 generation should be converted to gdbarch_make_corefile_notes; at that 78 point, the target vector method can be removed. */ 79 if (!gdbarch_make_corefile_notes_p (target_gdbarch ())) 80 note_data = target_make_corefile_notes (obfd, ¬e_size); 81 else 82 note_data = gdbarch_make_corefile_notes (target_gdbarch (), obfd, ¬e_size); 83 84 cleanup = make_cleanup (xfree, note_data); 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 (obfd, note_sec, 0); 99 bfd_set_section_alignment (obfd, note_sec, 0); 100 bfd_set_section_size (obfd, 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, 0, note_size)) 108 warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ())); 109 110 do_cleanups (cleanup); 111} 112 113/* write_gcore_file -- helper for gcore_command (exported). 114 Compose and write the corefile data to the core file. */ 115 116void 117write_gcore_file (bfd *obfd) 118{ 119 struct gdb_exception except = exception_none; 120 121 target_prepare_to_generate_core (); 122 123 TRY 124 { 125 write_gcore_file_1 (obfd); 126 } 127 CATCH (e, RETURN_MASK_ALL) 128 { 129 except = e; 130 } 131 END_CATCH 132 133 target_done_generating_core (); 134 135 if (except.reason < 0) 136 throw_exception (except); 137} 138 139/* gcore_command -- implements the 'gcore' command. 140 Generate a core file from the inferior process. */ 141 142static void 143gcore_command (char *args, int from_tty) 144{ 145 gdb::unique_xmalloc_ptr<char> corefilename; 146 147 /* No use generating a corefile without a target process. */ 148 if (!target_has_execution) 149 noprocess (); 150 151 if (args && *args) 152 corefilename.reset (tilde_expand (args)); 153 else 154 { 155 /* Default corefile name is "core.PID". */ 156 corefilename.reset (xstrprintf ("core.%d", ptid_get_pid (inferior_ptid))); 157 } 158 159 if (info_verbose) 160 fprintf_filtered (gdb_stdout, 161 "Opening corefile '%s' for output.\n", 162 corefilename.get ()); 163 164 /* Open the output file. */ 165 gdb_bfd_ref_ptr obfd (create_gcore_bfd (corefilename.get ())); 166 167 /* Arrange to unlink the file on failure. */ 168 gdb::unlinker unlink_file (corefilename.get ()); 169 170 /* Call worker function. */ 171 write_gcore_file (obfd.get ()); 172 173 /* Succeeded. */ 174 unlink_file.keep (); 175 176 fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename.get ()); 177} 178 179static unsigned long 180default_gcore_mach (void) 181{ 182#if 1 /* See if this even matters... */ 183 return 0; 184#else 185 186 const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ()); 187 188 if (bfdarch != NULL) 189 return bfdarch->mach; 190 if (exec_bfd == NULL) 191 error (_("Can't find default bfd machine type (need execfile).")); 192 193 return bfd_get_mach (exec_bfd); 194#endif /* 1 */ 195} 196 197static enum bfd_architecture 198default_gcore_arch (void) 199{ 200 const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ()); 201 202 if (bfdarch != NULL) 203 return bfdarch->arch; 204 if (exec_bfd == NULL) 205 error (_("Can't find bfd architecture for corefile (need execfile).")); 206 207 return bfd_get_arch (exec_bfd); 208} 209 210static const char * 211default_gcore_target (void) 212{ 213 /* The gdbarch may define a target to use for core files. */ 214 if (gdbarch_gcore_bfd_target_p (target_gdbarch ())) 215 return gdbarch_gcore_bfd_target (target_gdbarch ()); 216 217 /* Otherwise, try to fall back to the exec_bfd target. This will probably 218 not work for non-ELF targets. */ 219 if (exec_bfd == NULL) 220 return NULL; 221 else 222 return bfd_get_target (exec_bfd); 223} 224 225/* Derive a reasonable stack segment by unwinding the target stack, 226 and store its limits in *BOTTOM and *TOP. Return non-zero if 227 successful. */ 228 229static int 230derive_stack_segment (bfd_vma *bottom, bfd_vma *top) 231{ 232 struct frame_info *fi, *tmp_fi; 233 234 gdb_assert (bottom); 235 gdb_assert (top); 236 237 /* Can't succeed without stack and registers. */ 238 if (!target_has_stack || !target_has_registers) 239 return 0; 240 241 /* Can't succeed without current frame. */ 242 fi = get_current_frame (); 243 if (fi == NULL) 244 return 0; 245 246 /* Save frame pointer of TOS frame. */ 247 *top = get_frame_base (fi); 248 /* If current stack pointer is more "inner", use that instead. */ 249 if (gdbarch_inner_than (get_frame_arch (fi), get_frame_sp (fi), *top)) 250 *top = get_frame_sp (fi); 251 252 /* Find prev-most frame. */ 253 while ((tmp_fi = get_prev_frame (fi)) != NULL) 254 fi = tmp_fi; 255 256 /* Save frame pointer of prev-most frame. */ 257 *bottom = get_frame_base (fi); 258 259 /* Now canonicalize their order, so that BOTTOM is a lower address 260 (as opposed to a lower stack frame). */ 261 if (*bottom > *top) 262 { 263 bfd_vma tmp_vma; 264 265 tmp_vma = *top; 266 *top = *bottom; 267 *bottom = tmp_vma; 268 } 269 270 return 1; 271} 272 273/* call_target_sbrk -- 274 helper function for derive_heap_segment. */ 275 276static bfd_vma 277call_target_sbrk (int sbrk_arg) 278{ 279 struct objfile *sbrk_objf; 280 struct gdbarch *gdbarch; 281 bfd_vma top_of_heap; 282 struct value *target_sbrk_arg; 283 struct value *sbrk_fn, *ret; 284 bfd_vma tmp; 285 286 if (lookup_minimal_symbol ("sbrk", NULL, NULL).minsym != NULL) 287 { 288 sbrk_fn = find_function_in_inferior ("sbrk", &sbrk_objf); 289 if (sbrk_fn == NULL) 290 return (bfd_vma) 0; 291 } 292 else if (lookup_minimal_symbol ("_sbrk", NULL, NULL).minsym != NULL) 293 { 294 sbrk_fn = find_function_in_inferior ("_sbrk", &sbrk_objf); 295 if (sbrk_fn == NULL) 296 return (bfd_vma) 0; 297 } 298 else 299 return (bfd_vma) 0; 300 301 gdbarch = get_objfile_arch (sbrk_objf); 302 target_sbrk_arg = value_from_longest (builtin_type (gdbarch)->builtin_int, 303 sbrk_arg); 304 gdb_assert (target_sbrk_arg); 305 ret = call_function_by_hand (sbrk_fn, 1, &target_sbrk_arg); 306 if (ret == NULL) 307 return (bfd_vma) 0; 308 309 tmp = value_as_long (ret); 310 if ((LONGEST) tmp <= 0 || (LONGEST) tmp == 0xffffffff) 311 return (bfd_vma) 0; 312 313 top_of_heap = tmp; 314 return top_of_heap; 315} 316 317/* Derive a reasonable heap segment for ABFD by looking at sbrk and 318 the static data sections. Store its limits in *BOTTOM and *TOP. 319 Return non-zero if successful. */ 320 321static int 322derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top) 323{ 324 bfd_vma top_of_data_memory = 0; 325 bfd_vma top_of_heap = 0; 326 bfd_size_type sec_size; 327 bfd_vma sec_vaddr; 328 asection *sec; 329 330 gdb_assert (bottom); 331 gdb_assert (top); 332 333 /* This function depends on being able to call a function in the 334 inferior. */ 335 if (!target_has_execution) 336 return 0; 337 338 /* The following code assumes that the link map is arranged as 339 follows (low to high addresses): 340 341 --------------------------------- 342 | text sections | 343 --------------------------------- 344 | data sections (including bss) | 345 --------------------------------- 346 | heap | 347 --------------------------------- */ 348 349 for (sec = abfd->sections; sec; sec = sec->next) 350 { 351 if (bfd_get_section_flags (abfd, sec) & SEC_DATA 352 || strcmp (".bss", bfd_section_name (abfd, sec)) == 0) 353 { 354 sec_vaddr = bfd_get_section_vma (abfd, sec); 355 sec_size = bfd_get_section_size (sec); 356 if (sec_vaddr + sec_size > top_of_data_memory) 357 top_of_data_memory = sec_vaddr + sec_size; 358 } 359 } 360 361 top_of_heap = call_target_sbrk (0); 362 if (top_of_heap == (bfd_vma) 0) 363 return 0; 364 365 /* Return results. */ 366 if (top_of_heap > top_of_data_memory) 367 { 368 *bottom = top_of_data_memory; 369 *top = top_of_heap; 370 return 1; 371 } 372 373 /* No additional heap space needs to be saved. */ 374 return 0; 375} 376 377static void 378make_output_phdrs (bfd *obfd, asection *osec, void *ignored) 379{ 380 int p_flags = 0; 381 int p_type = 0; 382 383 /* FIXME: these constants may only be applicable for ELF. */ 384 if (startswith (bfd_section_name (obfd, osec), "load")) 385 p_type = PT_LOAD; 386 else if (startswith (bfd_section_name (obfd, osec), "note")) 387 p_type = PT_NOTE; 388 else 389 p_type = PT_NULL; 390 391 p_flags |= PF_R; /* Segment is readable. */ 392 if (!(bfd_get_section_flags (obfd, osec) & SEC_READONLY)) 393 p_flags |= PF_W; /* Segment is writable. */ 394 if (bfd_get_section_flags (obfd, osec) & SEC_CODE) 395 p_flags |= PF_X; /* Segment is executable. */ 396 397 bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec); 398} 399 400/* find_memory_region_ftype implementation. DATA is 'bfd *' for the core file 401 GDB is creating. */ 402 403static int 404gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read, 405 int write, int exec, int modified, void *data) 406{ 407 bfd *obfd = (bfd *) data; 408 asection *osec; 409 flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD; 410 411 /* If the memory segment has no permissions set, ignore it, otherwise 412 when we later try to access it for read/write, we'll get an error 413 or jam the kernel. */ 414 if (read == 0 && write == 0 && exec == 0 && modified == 0) 415 { 416 if (info_verbose) 417 { 418 fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at %s\n", 419 plongest (size), paddress (target_gdbarch (), vaddr)); 420 } 421 422 return 0; 423 } 424 425 if (write == 0 && modified == 0 && !solib_keep_data_in_core (vaddr, size)) 426 { 427 /* See if this region of memory lies inside a known file on disk. 428 If so, we can avoid copying its contents by clearing SEC_LOAD. */ 429 struct objfile *objfile; 430 struct obj_section *objsec; 431 432 ALL_OBJSECTIONS (objfile, objsec) 433 { 434 bfd *abfd = objfile->obfd; 435 asection *asec = objsec->the_bfd_section; 436 bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd, 437 asec); 438 bfd_vma start = obj_section_addr (objsec) & -align; 439 bfd_vma end = (obj_section_endaddr (objsec) + align - 1) & -align; 440 441 /* Match if either the entire memory region lies inside the 442 section (i.e. a mapping covering some pages of a large 443 segment) or the entire section lies inside the memory region 444 (i.e. a mapping covering multiple small sections). 445 446 This BFD was synthesized from reading target memory, 447 we don't want to omit that. */ 448 if (objfile->separate_debug_objfile_backlink == NULL 449 && ((vaddr >= start && vaddr + size <= end) 450 || (start >= vaddr && end <= vaddr + size)) 451 && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY)) 452 { 453 flags &= ~(SEC_LOAD | SEC_HAS_CONTENTS); 454 goto keep; /* Break out of two nested for loops. */ 455 } 456 } 457 458 keep:; 459 } 460 461 if (write == 0) 462 flags |= SEC_READONLY; 463 464 if (exec) 465 flags |= SEC_CODE; 466 else 467 flags |= SEC_DATA; 468 469 osec = bfd_make_section_anyway_with_flags (obfd, "load", flags); 470 if (osec == NULL) 471 { 472 warning (_("Couldn't make gcore segment: %s"), 473 bfd_errmsg (bfd_get_error ())); 474 return 1; 475 } 476 477 if (info_verbose) 478 { 479 fprintf_filtered (gdb_stdout, "Save segment, %s bytes at %s\n", 480 plongest (size), paddress (target_gdbarch (), vaddr)); 481 } 482 483 bfd_set_section_size (obfd, osec, size); 484 bfd_set_section_vma (obfd, osec, vaddr); 485 bfd_section_lma (obfd, osec) = 0; /* ??? bfd_set_section_lma? */ 486 return 0; 487} 488 489int 490objfile_find_memory_regions (struct target_ops *self, 491 find_memory_region_ftype func, void *obfd) 492{ 493 /* Use objfile data to create memory sections. */ 494 struct objfile *objfile; 495 struct obj_section *objsec; 496 bfd_vma temp_bottom, temp_top; 497 498 /* Call callback function for each objfile section. */ 499 ALL_OBJSECTIONS (objfile, objsec) 500 { 501 bfd *ibfd = objfile->obfd; 502 asection *isec = objsec->the_bfd_section; 503 flagword flags = bfd_get_section_flags (ibfd, isec); 504 505 /* Separate debug info files are irrelevant for gcore. */ 506 if (objfile->separate_debug_objfile_backlink != NULL) 507 continue; 508 509 if ((flags & SEC_ALLOC) || (flags & SEC_LOAD)) 510 { 511 int size = bfd_section_size (ibfd, isec); 512 int ret; 513 514 ret = (*func) (obj_section_addr (objsec), size, 515 1, /* All sections will be readable. */ 516 (flags & SEC_READONLY) == 0, /* Writable. */ 517 (flags & SEC_CODE) != 0, /* Executable. */ 518 1, /* MODIFIED is unknown, pass it as true. */ 519 obfd); 520 if (ret != 0) 521 return ret; 522 } 523 } 524 525 /* Make a stack segment. */ 526 if (derive_stack_segment (&temp_bottom, &temp_top)) 527 (*func) (temp_bottom, temp_top - temp_bottom, 528 1, /* Stack section will be readable. */ 529 1, /* Stack section will be writable. */ 530 0, /* Stack section will not be executable. */ 531 1, /* Stack section will be modified. */ 532 obfd); 533 534 /* Make a heap segment. */ 535 if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top)) 536 (*func) (temp_bottom, temp_top - temp_bottom, 537 1, /* Heap section will be readable. */ 538 1, /* Heap section will be writable. */ 539 0, /* Heap section will not be executable. */ 540 1, /* Heap section will be modified. */ 541 obfd); 542 543 return 0; 544} 545 546static void 547gcore_copy_callback (bfd *obfd, asection *osec, void *ignored) 548{ 549 bfd_size_type size, total_size = bfd_section_size (obfd, osec); 550 file_ptr offset = 0; 551 struct cleanup *old_chain = NULL; 552 gdb_byte *memhunk; 553 554 /* Read-only sections are marked; we don't have to copy their contents. */ 555 if ((bfd_get_section_flags (obfd, osec) & SEC_LOAD) == 0) 556 return; 557 558 /* Only interested in "load" sections. */ 559 if (!startswith (bfd_section_name (obfd, osec), "load")) 560 return; 561 562 size = std::min (total_size, (bfd_size_type) MAX_COPY_BYTES); 563 memhunk = (gdb_byte *) xmalloc (size); 564 old_chain = make_cleanup (xfree, memhunk); 565 566 while (total_size > 0) 567 { 568 if (size > total_size) 569 size = total_size; 570 571 if (target_read_memory (bfd_section_vma (obfd, osec) + offset, 572 memhunk, size) != 0) 573 { 574 warning (_("Memory read failed for corefile " 575 "section, %s bytes at %s."), 576 plongest (size), 577 paddress (target_gdbarch (), bfd_section_vma (obfd, osec))); 578 break; 579 } 580 if (!bfd_set_section_contents (obfd, osec, memhunk, offset, size)) 581 { 582 warning (_("Failed to write corefile contents (%s)."), 583 bfd_errmsg (bfd_get_error ())); 584 break; 585 } 586 587 total_size -= size; 588 offset += size; 589 } 590 591 do_cleanups (old_chain); /* Frees MEMHUNK. */ 592} 593 594static int 595gcore_memory_sections (bfd *obfd) 596{ 597 /* Try gdbarch method first, then fall back to target method. */ 598 if (!gdbarch_find_memory_regions_p (target_gdbarch ()) 599 || gdbarch_find_memory_regions (target_gdbarch (), 600 gcore_create_callback, obfd) != 0) 601 { 602 if (target_find_memory_regions (gcore_create_callback, obfd) != 0) 603 return 0; /* FIXME: error return/msg? */ 604 } 605 606 /* Record phdrs for section-to-segment mapping. */ 607 bfd_map_over_sections (obfd, make_output_phdrs, NULL); 608 609 /* Copy memory region contents. */ 610 bfd_map_over_sections (obfd, gcore_copy_callback, NULL); 611 612 return 1; 613} 614 615/* Provide a prototype to silence -Wmissing-prototypes. */ 616extern initialize_file_ftype _initialize_gcore; 617 618void 619_initialize_gcore (void) 620{ 621 add_com ("generate-core-file", class_files, gcore_command, _("\ 622Save a core file with the current state of the debugged process.\n\ 623Argument is optional filename. Default filename is 'core.<process_id>'.")); 624 625 add_com_alias ("gcore", "generate-core-file", class_files, 1); 626} 627