gcore.c revision 1.8
1/* Generate a core file for the inferior process. 2 3 Copyright (C) 2001-2019 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#include "common/byte-vector.h" 40 41/* The largest amount of memory to read from the target at once. We 42 must throttle it to limit the amount of memory used by GDB during 43 generate-core-file for programs with large resident data. */ 44#define MAX_COPY_BYTES (1024 * 1024) 45 46static const char *default_gcore_target (void); 47static enum bfd_architecture default_gcore_arch (void); 48static unsigned long default_gcore_mach (void); 49static int gcore_memory_sections (bfd *); 50 51/* create_gcore_bfd -- helper for gcore_command (exported). 52 Open a new bfd core file for output, and return the handle. */ 53 54gdb_bfd_ref_ptr 55create_gcore_bfd (const char *filename) 56{ 57 gdb_bfd_ref_ptr obfd (gdb_bfd_openw (filename, default_gcore_target ())); 58 59 if (obfd == NULL) 60 error (_("Failed to open '%s' for output."), filename); 61 bfd_set_format (obfd.get (), bfd_core); 62 bfd_set_arch_mach (obfd.get (), default_gcore_arch (), default_gcore_mach ()); 63 return obfd; 64} 65 66/* write_gcore_file_1 -- do the actual work of write_gcore_file. */ 67 68static void 69write_gcore_file_1 (bfd *obfd) 70{ 71 gdb::unique_xmalloc_ptr<char> note_data; 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.reset (target_make_corefile_notes (obfd, ¬e_size)); 81 else 82 note_data.reset (gdbarch_make_corefile_notes (target_gdbarch (), obfd, 83 ¬e_size)); 84 85 if (note_data == NULL || note_size == 0) 86 error (_("Target does not support core file generation.")); 87 88 /* Create the note section. */ 89 note_sec = bfd_make_section_anyway_with_flags (obfd, "note0", 90 SEC_HAS_CONTENTS 91 | SEC_READONLY 92 | SEC_ALLOC); 93 if (note_sec == NULL) 94 error (_("Failed to create 'note' section for corefile: %s"), 95 bfd_errmsg (bfd_get_error ())); 96 97 bfd_set_section_vma (obfd, note_sec, 0); 98 bfd_set_section_alignment (obfd, note_sec, 0); 99 bfd_set_section_size (obfd, note_sec, note_size); 100 101 /* Now create the memory/load sections. */ 102 if (gcore_memory_sections (obfd) == 0) 103 error (_("gcore: failed to get corefile memory sections from target.")); 104 105 /* Write out the contents of the note section. */ 106 if (!bfd_set_section_contents (obfd, note_sec, note_data.get (), 0, 107 note_size)) 108 warning (_("writing note section (%s)"), bfd_errmsg (bfd_get_error ())); 109} 110 111/* write_gcore_file -- helper for gcore_command (exported). 112 Compose and write the corefile data to the core file. */ 113 114void 115write_gcore_file (bfd *obfd) 116{ 117 struct gdb_exception except = exception_none; 118 119 target_prepare_to_generate_core (); 120 121 TRY 122 { 123 write_gcore_file_1 (obfd); 124 } 125 CATCH (e, RETURN_MASK_ALL) 126 { 127 except = e; 128 } 129 END_CATCH 130 131 target_done_generating_core (); 132 133 if (except.reason < 0) 134 throw_exception (except); 135} 136 137/* gcore_command -- implements the 'gcore' command. 138 Generate a core file from the inferior process. */ 139 140static void 141gcore_command (const char *args, int from_tty) 142{ 143 gdb::unique_xmalloc_ptr<char> corefilename; 144 145 /* No use generating a corefile without a target process. */ 146 if (!target_has_execution) 147 noprocess (); 148 149 if (args && *args) 150 corefilename.reset (tilde_expand (args)); 151 else 152 { 153 /* Default corefile name is "core.PID". */ 154 corefilename.reset (xstrprintf ("core.%d", inferior_ptid.pid ())); 155 } 156 157 if (info_verbose) 158 fprintf_filtered (gdb_stdout, 159 "Opening corefile '%s' for output.\n", 160 corefilename.get ()); 161 162 /* Open the output file. */ 163 gdb_bfd_ref_ptr obfd (create_gcore_bfd (corefilename.get ())); 164 165 /* Arrange to unlink the file on failure. */ 166 gdb::unlinker unlink_file (corefilename.get ()); 167 168 /* Call worker function. */ 169 write_gcore_file (obfd.get ()); 170 171 /* Succeeded. */ 172 unlink_file.keep (); 173 174 fprintf_filtered (gdb_stdout, "Saved corefile %s\n", corefilename.get ()); 175} 176 177static unsigned long 178default_gcore_mach (void) 179{ 180#if 1 /* See if this even matters... */ 181 return 0; 182#else 183 184 const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ()); 185 186 if (bfdarch != NULL) 187 return bfdarch->mach; 188 if (exec_bfd == NULL) 189 error (_("Can't find default bfd machine type (need execfile).")); 190 191 return bfd_get_mach (exec_bfd); 192#endif /* 1 */ 193} 194 195static enum bfd_architecture 196default_gcore_arch (void) 197{ 198 const struct bfd_arch_info *bfdarch = gdbarch_bfd_arch_info (target_gdbarch ()); 199 200 if (bfdarch != NULL) 201 return bfdarch->arch; 202 if (exec_bfd == NULL) 203 error (_("Can't find bfd architecture for corefile (need execfile).")); 204 205 return bfd_get_arch (exec_bfd); 206} 207 208static const char * 209default_gcore_target (void) 210{ 211 /* The gdbarch may define a target to use for core files. */ 212 if (gdbarch_gcore_bfd_target_p (target_gdbarch ())) 213 return gdbarch_gcore_bfd_target (target_gdbarch ()); 214 215 /* Otherwise, try to fall back to the exec_bfd target. This will probably 216 not work for non-ELF targets. */ 217 if (exec_bfd == NULL) 218 return NULL; 219 else 220 return bfd_get_target (exec_bfd); 221} 222 223/* Derive a reasonable stack segment by unwinding the target stack, 224 and store its limits in *BOTTOM and *TOP. Return non-zero if 225 successful. */ 226 227static int 228derive_stack_segment (bfd_vma *bottom, bfd_vma *top) 229{ 230 struct frame_info *fi, *tmp_fi; 231 232 gdb_assert (bottom); 233 gdb_assert (top); 234 235 /* Can't succeed without stack and registers. */ 236 if (!target_has_stack || !target_has_registers) 237 return 0; 238 239 /* Can't succeed without current frame. */ 240 fi = get_current_frame (); 241 if (fi == NULL) 242 return 0; 243 244 /* Save frame pointer of TOS frame. */ 245 *top = get_frame_base (fi); 246 /* If current stack pointer is more "inner", use that instead. */ 247 if (gdbarch_inner_than (get_frame_arch (fi), get_frame_sp (fi), *top)) 248 *top = get_frame_sp (fi); 249 250 /* Find prev-most frame. */ 251 while ((tmp_fi = get_prev_frame (fi)) != NULL) 252 fi = tmp_fi; 253 254 /* Save frame pointer of prev-most frame. */ 255 *bottom = get_frame_base (fi); 256 257 /* Now canonicalize their order, so that BOTTOM is a lower address 258 (as opposed to a lower stack frame). */ 259 if (*bottom > *top) 260 { 261 bfd_vma tmp_vma; 262 263 tmp_vma = *top; 264 *top = *bottom; 265 *bottom = tmp_vma; 266 } 267 268 return 1; 269} 270 271/* call_target_sbrk -- 272 helper function for derive_heap_segment. */ 273 274static bfd_vma 275call_target_sbrk (int sbrk_arg) 276{ 277 struct objfile *sbrk_objf; 278 struct gdbarch *gdbarch; 279 bfd_vma top_of_heap; 280 struct value *target_sbrk_arg; 281 struct value *sbrk_fn, *ret; 282 bfd_vma tmp; 283 284 if (lookup_minimal_symbol ("sbrk", NULL, NULL).minsym != NULL) 285 { 286 sbrk_fn = find_function_in_inferior ("sbrk", &sbrk_objf); 287 if (sbrk_fn == NULL) 288 return (bfd_vma) 0; 289 } 290 else if (lookup_minimal_symbol ("_sbrk", NULL, NULL).minsym != NULL) 291 { 292 sbrk_fn = find_function_in_inferior ("_sbrk", &sbrk_objf); 293 if (sbrk_fn == NULL) 294 return (bfd_vma) 0; 295 } 296 else 297 return (bfd_vma) 0; 298 299 gdbarch = get_objfile_arch (sbrk_objf); 300 target_sbrk_arg = value_from_longest (builtin_type (gdbarch)->builtin_int, 301 sbrk_arg); 302 gdb_assert (target_sbrk_arg); 303 ret = call_function_by_hand (sbrk_fn, NULL, target_sbrk_arg); 304 if (ret == NULL) 305 return (bfd_vma) 0; 306 307 tmp = value_as_long (ret); 308 if ((LONGEST) tmp <= 0 || (LONGEST) tmp == 0xffffffff) 309 return (bfd_vma) 0; 310 311 top_of_heap = tmp; 312 return top_of_heap; 313} 314 315/* Derive a reasonable heap segment for ABFD by looking at sbrk and 316 the static data sections. Store its limits in *BOTTOM and *TOP. 317 Return non-zero if successful. */ 318 319static int 320derive_heap_segment (bfd *abfd, bfd_vma *bottom, bfd_vma *top) 321{ 322 bfd_vma top_of_data_memory = 0; 323 bfd_vma top_of_heap = 0; 324 bfd_size_type sec_size; 325 bfd_vma sec_vaddr; 326 asection *sec; 327 328 gdb_assert (bottom); 329 gdb_assert (top); 330 331 /* This function depends on being able to call a function in the 332 inferior. */ 333 if (!target_has_execution) 334 return 0; 335 336 /* The following code assumes that the link map is arranged as 337 follows (low to high addresses): 338 339 --------------------------------- 340 | text sections | 341 --------------------------------- 342 | data sections (including bss) | 343 --------------------------------- 344 | heap | 345 --------------------------------- */ 346 347 for (sec = abfd->sections; sec; sec = sec->next) 348 { 349 if (bfd_get_section_flags (abfd, sec) & SEC_DATA 350 || strcmp (".bss", bfd_section_name (abfd, sec)) == 0) 351 { 352 sec_vaddr = bfd_get_section_vma (abfd, sec); 353 sec_size = bfd_get_section_size (sec); 354 if (sec_vaddr + sec_size > top_of_data_memory) 355 top_of_data_memory = sec_vaddr + sec_size; 356 } 357 } 358 359 top_of_heap = call_target_sbrk (0); 360 if (top_of_heap == (bfd_vma) 0) 361 return 0; 362 363 /* Return results. */ 364 if (top_of_heap > top_of_data_memory) 365 { 366 *bottom = top_of_data_memory; 367 *top = top_of_heap; 368 return 1; 369 } 370 371 /* No additional heap space needs to be saved. */ 372 return 0; 373} 374 375static void 376make_output_phdrs (bfd *obfd, asection *osec, void *ignored) 377{ 378 int p_flags = 0; 379 int p_type = 0; 380 381 /* FIXME: these constants may only be applicable for ELF. */ 382 if (startswith (bfd_section_name (obfd, osec), "load")) 383 p_type = PT_LOAD; 384 else if (startswith (bfd_section_name (obfd, osec), "note")) 385 p_type = PT_NOTE; 386 else 387 p_type = PT_NULL; 388 389 p_flags |= PF_R; /* Segment is readable. */ 390 if (!(bfd_get_section_flags (obfd, osec) & SEC_READONLY)) 391 p_flags |= PF_W; /* Segment is writable. */ 392 if (bfd_get_section_flags (obfd, osec) & SEC_CODE) 393 p_flags |= PF_X; /* Segment is executable. */ 394 395 bfd_record_phdr (obfd, p_type, 1, p_flags, 0, 0, 0, 0, 1, &osec); 396} 397 398/* find_memory_region_ftype implementation. DATA is 'bfd *' for the core file 399 GDB is creating. */ 400 401static int 402gcore_create_callback (CORE_ADDR vaddr, unsigned long size, int read, 403 int write, int exec, int modified, void *data) 404{ 405 bfd *obfd = (bfd *) data; 406 asection *osec; 407 flagword flags = SEC_ALLOC | SEC_HAS_CONTENTS | SEC_LOAD; 408 409 /* If the memory segment has no permissions set, ignore it, otherwise 410 when we later try to access it for read/write, we'll get an error 411 or jam the kernel. */ 412 if (read == 0 && write == 0 && exec == 0 && modified == 0) 413 { 414 if (info_verbose) 415 { 416 fprintf_filtered (gdb_stdout, "Ignore segment, %s bytes at %s\n", 417 plongest (size), paddress (target_gdbarch (), vaddr)); 418 } 419 420 return 0; 421 } 422 423 if (write == 0 && modified == 0 && !solib_keep_data_in_core (vaddr, size)) 424 { 425 /* See if this region of memory lies inside a known file on disk. 426 If so, we can avoid copying its contents by clearing SEC_LOAD. */ 427 struct obj_section *objsec; 428 429 for (objfile *objfile : current_program_space->objfiles ()) 430 ALL_OBJFILE_OSECTIONS (objfile, objsec) 431 { 432 bfd *abfd = objfile->obfd; 433 asection *asec = objsec->the_bfd_section; 434 bfd_vma align = (bfd_vma) 1 << bfd_get_section_alignment (abfd, 435 asec); 436 bfd_vma start = obj_section_addr (objsec) & -align; 437 bfd_vma end = (obj_section_endaddr (objsec) + align - 1) & -align; 438 439 /* Match if either the entire memory region lies inside the 440 section (i.e. a mapping covering some pages of a large 441 segment) or the entire section lies inside the memory region 442 (i.e. a mapping covering multiple small sections). 443 444 This BFD was synthesized from reading target memory, 445 we don't want to omit that. */ 446 if (objfile->separate_debug_objfile_backlink == NULL 447 && ((vaddr >= start && vaddr + size <= end) 448 || (start >= vaddr && end <= vaddr + size)) 449 && !(bfd_get_file_flags (abfd) & BFD_IN_MEMORY)) 450 { 451 flags &= ~(SEC_LOAD | SEC_HAS_CONTENTS); 452 goto keep; /* Break out of two nested for loops. */ 453 } 454 } 455 456 keep:; 457 } 458 459 if (write == 0) 460 flags |= SEC_READONLY; 461 462 if (exec) 463 flags |= SEC_CODE; 464 else 465 flags |= SEC_DATA; 466 467 osec = bfd_make_section_anyway_with_flags (obfd, "load", flags); 468 if (osec == NULL) 469 { 470 warning (_("Couldn't make gcore segment: %s"), 471 bfd_errmsg (bfd_get_error ())); 472 return 1; 473 } 474 475 if (info_verbose) 476 { 477 fprintf_filtered (gdb_stdout, "Save segment, %s bytes at %s\n", 478 plongest (size), paddress (target_gdbarch (), vaddr)); 479 } 480 481 bfd_set_section_size (obfd, osec, size); 482 bfd_set_section_vma (obfd, osec, vaddr); 483 bfd_section_lma (obfd, osec) = 0; /* ??? bfd_set_section_lma? */ 484 return 0; 485} 486 487int 488objfile_find_memory_regions (struct target_ops *self, 489 find_memory_region_ftype func, void *obfd) 490{ 491 /* Use objfile data to create memory sections. */ 492 struct obj_section *objsec; 493 bfd_vma temp_bottom, temp_top; 494 495 /* Call callback function for each objfile section. */ 496 for (objfile *objfile : current_program_space->objfiles ()) 497 ALL_OBJFILE_OSECTIONS (objfile, objsec) 498 { 499 bfd *ibfd = objfile->obfd; 500 asection *isec = objsec->the_bfd_section; 501 flagword flags = bfd_get_section_flags (ibfd, isec); 502 503 /* Separate debug info files are irrelevant for gcore. */ 504 if (objfile->separate_debug_objfile_backlink != NULL) 505 continue; 506 507 if ((flags & SEC_ALLOC) || (flags & SEC_LOAD)) 508 { 509 int size = bfd_section_size (ibfd, isec); 510 int ret; 511 512 ret = (*func) (obj_section_addr (objsec), size, 513 1, /* All sections will be readable. */ 514 (flags & SEC_READONLY) == 0, /* Writable. */ 515 (flags & SEC_CODE) != 0, /* Executable. */ 516 1, /* MODIFIED is unknown, pass it as true. */ 517 obfd); 518 if (ret != 0) 519 return ret; 520 } 521 } 522 523 /* Make a stack segment. */ 524 if (derive_stack_segment (&temp_bottom, &temp_top)) 525 (*func) (temp_bottom, temp_top - temp_bottom, 526 1, /* Stack section will be readable. */ 527 1, /* Stack section will be writable. */ 528 0, /* Stack section will not be executable. */ 529 1, /* Stack section will be modified. */ 530 obfd); 531 532 /* Make a heap segment. */ 533 if (derive_heap_segment (exec_bfd, &temp_bottom, &temp_top)) 534 (*func) (temp_bottom, temp_top - temp_bottom, 535 1, /* Heap section will be readable. */ 536 1, /* Heap section will be writable. */ 537 0, /* Heap section will not be executable. */ 538 1, /* Heap section will be modified. */ 539 obfd); 540 541 return 0; 542} 543 544static void 545gcore_copy_callback (bfd *obfd, asection *osec, void *ignored) 546{ 547 bfd_size_type size, total_size = bfd_section_size (obfd, osec); 548 file_ptr offset = 0; 549 550 /* Read-only sections are marked; we don't have to copy their contents. */ 551 if ((bfd_get_section_flags (obfd, osec) & SEC_LOAD) == 0) 552 return; 553 554 /* Only interested in "load" sections. */ 555 if (!startswith (bfd_section_name (obfd, osec), "load")) 556 return; 557 558 size = std::min (total_size, (bfd_size_type) MAX_COPY_BYTES); 559 gdb::byte_vector memhunk (size); 560 561 while (total_size > 0) 562 { 563 if (size > total_size) 564 size = total_size; 565 566 if (target_read_memory (bfd_section_vma (obfd, osec) + offset, 567 memhunk.data (), size) != 0) 568 { 569 warning (_("Memory read failed for corefile " 570 "section, %s bytes at %s."), 571 plongest (size), 572 paddress (target_gdbarch (), bfd_section_vma (obfd, osec))); 573 break; 574 } 575 if (!bfd_set_section_contents (obfd, osec, memhunk.data (), 576 offset, size)) 577 { 578 warning (_("Failed to write corefile contents (%s)."), 579 bfd_errmsg (bfd_get_error ())); 580 break; 581 } 582 583 total_size -= size; 584 offset += size; 585 } 586} 587 588static int 589gcore_memory_sections (bfd *obfd) 590{ 591 /* Try gdbarch method first, then fall back to target method. */ 592 if (!gdbarch_find_memory_regions_p (target_gdbarch ()) 593 || gdbarch_find_memory_regions (target_gdbarch (), 594 gcore_create_callback, obfd) != 0) 595 { 596 if (target_find_memory_regions (gcore_create_callback, obfd) != 0) 597 return 0; /* FIXME: error return/msg? */ 598 } 599 600 /* Record phdrs for section-to-segment mapping. */ 601 bfd_map_over_sections (obfd, make_output_phdrs, NULL); 602 603 /* Copy memory region contents. */ 604 bfd_map_over_sections (obfd, gcore_copy_callback, NULL); 605 606 return 1; 607} 608 609void 610_initialize_gcore (void) 611{ 612 add_com ("generate-core-file", class_files, gcore_command, _("\ 613Save a core file with the current state of the debugged process.\n\ 614Usage: generate-core-file [FILENAME]\n\ 615Argument is optional filename. Default filename is 'core.PROCESS_ID'.")); 616 617 add_com_alias ("gcore", "generate-core-file", class_files, 1); 618} 619