1 /* Read ELF (Executable and Linking Format) object files for GDB.
3 Copyright (C) 1991-2019 Free Software Foundation, Inc.
5 Written by Fred Fish at Cygnus Support.
7 This file is part of GDB.
9 This program is free software; you can redistribute it and/or modify
10 it under the terms of the GNU General Public License as published by
11 the Free Software Foundation; either version 3 of the License, or
12 (at your option) any later version.
14 This program is distributed in the hope that it will be useful,
15 but WITHOUT ANY WARRANTY; without even the implied warranty of
16 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 GNU General Public License for more details.
19 You should have received a copy of the GNU General Public License
20 along with this program. If not, see <http://www.gnu.org/licenses/>. */
25 #include "elf/common.h"
26 #include "elf/internal.h"
31 #include "stabsread.h"
32 #include "gdb-stabs.h"
33 #include "complaints.h"
36 #include "filenames.h"
38 #include "arch-utils.h"
42 #include "gdbthread.h"
51 /* Forward declarations. */
52 extern const struct sym_fns elf_sym_fns_gdb_index;
53 extern const struct sym_fns elf_sym_fns_debug_names;
54 extern const struct sym_fns elf_sym_fns_lazy_psyms;
56 /* The struct elfinfo is available only during ELF symbol table and
57 psymtab reading. It is destroyed at the completion of psymtab-reading.
58 It's local to elf_symfile_read. */
62 asection *stabsect; /* Section pointer for .stab section */
63 asection *mdebugsect; /* Section pointer for .mdebug section */
66 /* Per-BFD data for probe info. */
68 static const struct bfd_data *probe_key = NULL;
70 /* Minimal symbols located at the GOT entries for .plt - that is the real
71 pointer where the given entry will jump to. It gets updated by the real
72 function address during lazy ld.so resolving in the inferior. These
73 minimal symbols are indexed for <tab>-completion. */
75 #define SYMBOL_GOT_PLT_SUFFIX "@got.plt"
77 /* Locate the segments in ABFD. */
79 static struct symfile_segment_data *
80 elf_symfile_segments (bfd *abfd)
82 Elf_Internal_Phdr *phdrs, **segments;
84 int num_phdrs, num_segments, num_sections, i;
86 struct symfile_segment_data *data;
88 phdrs_size = bfd_get_elf_phdr_upper_bound (abfd);
92 phdrs = (Elf_Internal_Phdr *) alloca (phdrs_size);
93 num_phdrs = bfd_get_elf_phdrs (abfd, phdrs);
98 segments = XALLOCAVEC (Elf_Internal_Phdr *, num_phdrs);
99 for (i = 0; i < num_phdrs; i++)
100 if (phdrs[i].p_type == PT_LOAD)
101 segments[num_segments++] = &phdrs[i];
103 if (num_segments == 0)
106 data = XCNEW (struct symfile_segment_data);
107 data->num_segments = num_segments;
108 data->segment_bases = XCNEWVEC (CORE_ADDR, num_segments);
109 data->segment_sizes = XCNEWVEC (CORE_ADDR, num_segments);
111 for (i = 0; i < num_segments; i++)
113 data->segment_bases[i] = segments[i]->p_vaddr;
114 data->segment_sizes[i] = segments[i]->p_memsz;
117 num_sections = bfd_count_sections (abfd);
118 data->segment_info = XCNEWVEC (int, num_sections);
120 for (i = 0, sect = abfd->sections; sect != NULL; i++, sect = sect->next)
124 if ((bfd_get_section_flags (abfd, sect) & SEC_ALLOC) == 0)
127 Elf_Internal_Shdr *this_hdr = &elf_section_data (sect)->this_hdr;
129 for (j = 0; j < num_segments; j++)
130 if (ELF_SECTION_IN_SEGMENT (this_hdr, segments[j]))
132 data->segment_info[i] = j + 1;
136 /* We should have found a segment for every non-empty section.
137 If we haven't, we will not relocate this section by any
138 offsets we apply to the segments. As an exception, do not
139 warn about SHT_NOBITS sections; in normal ELF execution
140 environments, SHT_NOBITS means zero-initialized and belongs
141 in a segment, but in no-OS environments some tools (e.g. ARM
142 RealView) use SHT_NOBITS for uninitialized data. Since it is
143 uninitialized, it doesn't need a program header. Such
144 binaries are not relocatable. */
145 if (bfd_get_section_size (sect) > 0 && j == num_segments
146 && (bfd_get_section_flags (abfd, sect) & SEC_LOAD) != 0)
147 warning (_("Loadable section \"%s\" outside of ELF segments"),
148 bfd_section_name (abfd, sect));
154 /* We are called once per section from elf_symfile_read. We
155 need to examine each section we are passed, check to see
156 if it is something we are interested in processing, and
157 if so, stash away some access information for the section.
159 For now we recognize the dwarf debug information sections and
160 line number sections from matching their section names. The
161 ELF definition is no real help here since it has no direct
162 knowledge of DWARF (by design, so any debugging format can be
165 We also recognize the ".stab" sections used by the Sun compilers
166 released with Solaris 2.
168 FIXME: The section names should not be hardwired strings (what
169 should they be? I don't think most object file formats have enough
170 section flags to specify what kind of debug section it is.
174 elf_locate_sections (bfd *ignore_abfd, asection *sectp, void *eip)
178 ei = (struct elfinfo *) eip;
179 if (strcmp (sectp->name, ".stab") == 0)
181 ei->stabsect = sectp;
183 else if (strcmp (sectp->name, ".mdebug") == 0)
185 ei->mdebugsect = sectp;
189 static struct minimal_symbol *
190 record_minimal_symbol (minimal_symbol_reader &reader,
191 const char *name, int name_len, bool copy_name,
193 enum minimal_symbol_type ms_type,
194 asection *bfd_section, struct objfile *objfile)
196 struct gdbarch *gdbarch = get_objfile_arch (objfile);
198 if (ms_type == mst_text || ms_type == mst_file_text
199 || ms_type == mst_text_gnu_ifunc)
200 address = gdbarch_addr_bits_remove (gdbarch, address);
202 return reader.record_full (name, name_len, copy_name, address,
204 gdb_bfd_section_index (objfile->obfd,
208 /* Read the symbol table of an ELF file.
210 Given an objfile, a symbol table, and a flag indicating whether the
211 symbol table contains regular, dynamic, or synthetic symbols, add all
212 the global function and data symbols to the minimal symbol table.
214 In stabs-in-ELF, as implemented by Sun, there are some local symbols
215 defined in the ELF symbol table, which can be used to locate
216 the beginnings of sections from each ".o" file that was linked to
217 form the executable objfile. We gather any such info and record it
218 in data structures hung off the objfile's private data. */
222 #define ST_SYNTHETIC 2
225 elf_symtab_read (minimal_symbol_reader &reader,
226 struct objfile *objfile, int type,
227 long number_of_symbols, asymbol **symbol_table,
230 struct gdbarch *gdbarch = get_objfile_arch (objfile);
234 enum minimal_symbol_type ms_type;
235 /* Name of the last file symbol. This is either a constant string or is
236 saved on the objfile's filename cache. */
237 const char *filesymname = "";
238 int stripped = (bfd_get_symcount (objfile->obfd) == 0);
239 int elf_make_msymbol_special_p
240 = gdbarch_elf_make_msymbol_special_p (gdbarch);
242 for (i = 0; i < number_of_symbols; i++)
244 sym = symbol_table[i];
245 if (sym->name == NULL || *sym->name == '\0')
247 /* Skip names that don't exist (shouldn't happen), or names
248 that are null strings (may happen). */
252 /* Skip "special" symbols, e.g. ARM mapping symbols. These are
253 symbols which do not correspond to objects in the symbol table,
254 but have some other target-specific meaning. */
255 if (bfd_is_target_special_symbol (objfile->obfd, sym))
257 if (gdbarch_record_special_symbol_p (gdbarch))
258 gdbarch_record_special_symbol (gdbarch, objfile, sym);
262 if (type == ST_DYNAMIC
263 && sym->section == bfd_und_section_ptr
264 && (sym->flags & BSF_FUNCTION))
266 struct minimal_symbol *msym;
267 bfd *abfd = objfile->obfd;
270 /* Symbol is a reference to a function defined in
272 If its value is non zero then it is usually the address
273 of the corresponding entry in the procedure linkage table,
274 plus the desired section offset.
275 If its value is zero then the dynamic linker has to resolve
276 the symbol. We are unable to find any meaningful address
277 for this symbol in the executable file, so we skip it. */
278 symaddr = sym->value;
282 /* sym->section is the undefined section. However, we want to
283 record the section where the PLT stub resides with the
284 minimal symbol. Search the section table for the one that
285 covers the stub's address. */
286 for (sect = abfd->sections; sect != NULL; sect = sect->next)
288 if ((bfd_get_section_flags (abfd, sect) & SEC_ALLOC) == 0)
291 if (symaddr >= bfd_get_section_vma (abfd, sect)
292 && symaddr < bfd_get_section_vma (abfd, sect)
293 + bfd_get_section_size (sect))
299 /* On ia64-hpux, we have discovered that the system linker
300 adds undefined symbols with nonzero addresses that cannot
301 be right (their address points inside the code of another
302 function in the .text section). This creates problems
303 when trying to determine which symbol corresponds to
306 We try to detect those buggy symbols by checking which
307 section we think they correspond to. Normally, PLT symbols
308 are stored inside their own section, and the typical name
309 for that section is ".plt". So, if there is a ".plt"
310 section, and yet the section name of our symbol does not
311 start with ".plt", we ignore that symbol. */
312 if (!startswith (sect->name, ".plt")
313 && bfd_get_section_by_name (abfd, ".plt") != NULL)
316 msym = record_minimal_symbol
317 (reader, sym->name, strlen (sym->name), copy_names,
318 symaddr, mst_solib_trampoline, sect, objfile);
321 msym->filename = filesymname;
322 if (elf_make_msymbol_special_p)
323 gdbarch_elf_make_msymbol_special (gdbarch, sym, msym);
328 /* If it is a nonstripped executable, do not enter dynamic
329 symbols, as the dynamic symbol table is usually a subset
330 of the main symbol table. */
331 if (type == ST_DYNAMIC && !stripped)
333 if (sym->flags & BSF_FILE)
336 = (const char *) bcache (sym->name, strlen (sym->name) + 1,
337 objfile->per_bfd->filename_cache);
339 else if (sym->flags & BSF_SECTION_SYM)
341 else if (sym->flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK
344 struct minimal_symbol *msym;
346 /* Select global/local/weak symbols. Note that bfd puts abs
347 symbols in their own section, so all symbols we are
348 interested in will have a section. */
349 /* Bfd symbols are section relative. */
350 symaddr = sym->value + sym->section->vma;
351 /* For non-absolute symbols, use the type of the section
352 they are relative to, to intuit text/data. Bfd provides
353 no way of figuring this out for absolute symbols. */
354 if (sym->section == bfd_abs_section_ptr)
356 /* This is a hack to get the minimal symbol type
357 right for Irix 5, which has absolute addresses
358 with special section indices for dynamic symbols.
360 NOTE: uweigand-20071112: Synthetic symbols do not
361 have an ELF-private part, so do not touch those. */
362 unsigned int shndx = type == ST_SYNTHETIC ? 0 :
363 ((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;
373 case SHN_MIPS_ACOMMON:
380 /* If it is an Irix dynamic symbol, skip section name
381 symbols, relocate all others by section offset. */
382 if (ms_type != mst_abs)
384 if (sym->name[0] == '.')
388 else if (sym->section->flags & SEC_CODE)
390 if (sym->flags & (BSF_GLOBAL | BSF_WEAK | BSF_GNU_UNIQUE))
392 if (sym->flags & BSF_GNU_INDIRECT_FUNCTION)
393 ms_type = mst_text_gnu_ifunc;
397 /* The BSF_SYNTHETIC check is there to omit ppc64 function
398 descriptors mistaken for static functions starting with 'L'.
400 else if ((sym->name[0] == '.' && sym->name[1] == 'L'
401 && (sym->flags & BSF_SYNTHETIC) == 0)
402 || ((sym->flags & BSF_LOCAL)
403 && sym->name[0] == '$'
404 && sym->name[1] == 'L'))
405 /* Looks like a compiler-generated label. Skip
406 it. The assembler should be skipping these (to
407 keep executables small), but apparently with
408 gcc on the (deleted) delta m88k SVR4, it loses.
409 So to have us check too should be harmless (but
410 I encourage people to fix this in the assembler
411 instead of adding checks here). */
415 ms_type = mst_file_text;
418 else if (sym->section->flags & SEC_ALLOC)
420 if (sym->flags & (BSF_GLOBAL | BSF_WEAK | BSF_GNU_UNIQUE))
422 if (sym->flags & BSF_GNU_INDIRECT_FUNCTION)
424 ms_type = mst_data_gnu_ifunc;
426 else if (sym->section->flags & SEC_LOAD)
435 else if (sym->flags & BSF_LOCAL)
437 if (sym->section->flags & SEC_LOAD)
439 ms_type = mst_file_data;
443 ms_type = mst_file_bss;
448 ms_type = mst_unknown;
453 /* FIXME: Solaris2 shared libraries include lots of
454 odd "absolute" and "undefined" symbols, that play
455 hob with actions like finding what function the PC
456 is in. Ignore them if they aren't text, data, or bss. */
457 /* ms_type = mst_unknown; */
458 continue; /* Skip this symbol. */
460 msym = record_minimal_symbol
461 (reader, sym->name, strlen (sym->name), copy_names, symaddr,
462 ms_type, sym->section, objfile);
466 /* NOTE: uweigand-20071112: A synthetic symbol does not have an
468 if (type != ST_SYNTHETIC)
470 /* Pass symbol size field in via BFD. FIXME!!! */
471 elf_symbol_type *elf_sym = (elf_symbol_type *) sym;
472 SET_MSYMBOL_SIZE (msym, elf_sym->internal_elf_sym.st_size);
475 msym->filename = filesymname;
476 if (elf_make_msymbol_special_p)
477 gdbarch_elf_make_msymbol_special (gdbarch, sym, msym);
480 /* If we see a default versioned symbol, install it under
481 its version-less name. */
484 const char *atsign = strchr (sym->name, '@');
486 if (atsign != NULL && atsign[1] == '@' && atsign > sym->name)
488 int len = atsign - sym->name;
490 record_minimal_symbol (reader, sym->name, len, true, symaddr,
491 ms_type, sym->section, objfile);
495 /* For @plt symbols, also record a trampoline to the
496 destination symbol. The @plt symbol will be used in
497 disassembly, and the trampoline will be used when we are
498 trying to find the target. */
499 if (msym && ms_type == mst_text && type == ST_SYNTHETIC)
501 int len = strlen (sym->name);
503 if (len > 4 && strcmp (sym->name + len - 4, "@plt") == 0)
505 struct minimal_symbol *mtramp;
507 mtramp = record_minimal_symbol (reader, sym->name, len - 4,
509 mst_solib_trampoline,
510 sym->section, objfile);
513 SET_MSYMBOL_SIZE (mtramp, MSYMBOL_SIZE (msym));
514 mtramp->created_by_gdb = 1;
515 mtramp->filename = filesymname;
516 if (elf_make_msymbol_special_p)
517 gdbarch_elf_make_msymbol_special (gdbarch,
526 /* Build minimal symbols named `function@got.plt' (see SYMBOL_GOT_PLT_SUFFIX)
527 for later look ups of which function to call when user requests
528 a STT_GNU_IFUNC function. As the STT_GNU_IFUNC type is found at the target
529 library defining `function' we cannot yet know while reading OBJFILE which
530 of the SYMBOL_GOT_PLT_SUFFIX entries will be needed and later
531 DYN_SYMBOL_TABLE is no longer easily available for OBJFILE. */
534 elf_rel_plt_read (minimal_symbol_reader &reader,
535 struct objfile *objfile, asymbol **dyn_symbol_table)
537 bfd *obfd = objfile->obfd;
538 const struct elf_backend_data *bed = get_elf_backend_data (obfd);
539 asection *relplt, *got_plt;
540 bfd_size_type reloc_count, reloc;
541 struct gdbarch *gdbarch = get_objfile_arch (objfile);
542 struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
543 size_t ptr_size = TYPE_LENGTH (ptr_type);
545 if (objfile->separate_debug_objfile_backlink)
548 got_plt = bfd_get_section_by_name (obfd, ".got.plt");
551 /* For platforms where there is no separate .got.plt. */
552 got_plt = bfd_get_section_by_name (obfd, ".got");
557 /* Depending on system, we may find jump slots in a relocation
558 section for either .got.plt or .plt. */
559 asection *plt = bfd_get_section_by_name (obfd, ".plt");
560 int plt_elf_idx = (plt != NULL) ? elf_section_data (plt)->this_idx : -1;
562 int got_plt_elf_idx = elf_section_data (got_plt)->this_idx;
564 /* This search algorithm is from _bfd_elf_canonicalize_dynamic_reloc. */
565 for (relplt = obfd->sections; relplt != NULL; relplt = relplt->next)
567 const auto &this_hdr = elf_section_data (relplt)->this_hdr;
569 if (this_hdr.sh_type == SHT_REL || this_hdr.sh_type == SHT_RELA)
571 if (this_hdr.sh_info == plt_elf_idx
572 || this_hdr.sh_info == got_plt_elf_idx)
579 if (! bed->s->slurp_reloc_table (obfd, relplt, dyn_symbol_table, TRUE))
582 std::string string_buffer;
584 /* Does ADDRESS reside in SECTION of OBFD? */
585 auto within_section = [obfd] (asection *section, CORE_ADDR address)
590 return (bfd_get_section_vma (obfd, section) <= address
591 && (address < bfd_get_section_vma (obfd, section)
592 + bfd_get_section_size (section)));
595 reloc_count = relplt->size / elf_section_data (relplt)->this_hdr.sh_entsize;
596 for (reloc = 0; reloc < reloc_count; reloc++)
599 struct minimal_symbol *msym;
601 const char *got_suffix = SYMBOL_GOT_PLT_SUFFIX;
602 const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
604 name = bfd_asymbol_name (*relplt->relocation[reloc].sym_ptr_ptr);
605 address = relplt->relocation[reloc].address;
607 asection *msym_section;
609 /* Does the pointer reside in either the .got.plt or .plt
611 if (within_section (got_plt, address))
612 msym_section = got_plt;
613 else if (within_section (plt, address))
618 /* We cannot check if NAME is a reference to
619 mst_text_gnu_ifunc/mst_data_gnu_ifunc as in OBJFILE the
620 symbol is undefined and the objfile having NAME defined may
621 not yet have been loaded. */
623 string_buffer.assign (name);
624 string_buffer.append (got_suffix, got_suffix + got_suffix_len);
626 msym = record_minimal_symbol (reader, string_buffer.c_str (),
627 string_buffer.size (),
628 true, address, mst_slot_got_plt,
629 msym_section, objfile);
631 SET_MSYMBOL_SIZE (msym, ptr_size);
635 /* The data pointer is htab_t for gnu_ifunc_record_cache_unchecked. */
637 static const struct objfile_data *elf_objfile_gnu_ifunc_cache_data;
639 /* Map function names to CORE_ADDR in elf_objfile_gnu_ifunc_cache_data. */
641 struct elf_gnu_ifunc_cache
643 /* This is always a function entry address, not a function descriptor. */
649 /* htab_hash for elf_objfile_gnu_ifunc_cache_data. */
652 elf_gnu_ifunc_cache_hash (const void *a_voidp)
654 const struct elf_gnu_ifunc_cache *a
655 = (const struct elf_gnu_ifunc_cache *) a_voidp;
657 return htab_hash_string (a->name);
660 /* htab_eq for elf_objfile_gnu_ifunc_cache_data. */
663 elf_gnu_ifunc_cache_eq (const void *a_voidp, const void *b_voidp)
665 const struct elf_gnu_ifunc_cache *a
666 = (const struct elf_gnu_ifunc_cache *) a_voidp;
667 const struct elf_gnu_ifunc_cache *b
668 = (const struct elf_gnu_ifunc_cache *) b_voidp;
670 return strcmp (a->name, b->name) == 0;
673 /* Record the target function address of a STT_GNU_IFUNC function NAME is the
674 function entry address ADDR. Return 1 if NAME and ADDR are considered as
675 valid and therefore they were successfully recorded, return 0 otherwise.
677 Function does not expect a duplicate entry. Use
678 elf_gnu_ifunc_resolve_by_cache first to check if the entry for NAME already
682 elf_gnu_ifunc_record_cache (const char *name, CORE_ADDR addr)
684 struct bound_minimal_symbol msym;
685 struct objfile *objfile;
687 struct elf_gnu_ifunc_cache entry_local, *entry_p;
690 msym = lookup_minimal_symbol_by_pc (addr);
691 if (msym.minsym == NULL)
693 if (BMSYMBOL_VALUE_ADDRESS (msym) != addr)
695 objfile = msym.objfile;
697 /* If .plt jumps back to .plt the symbol is still deferred for later
698 resolution and it has no use for GDB. */
699 const char *target_name = MSYMBOL_LINKAGE_NAME (msym.minsym);
700 size_t len = strlen (target_name);
702 /* Note we check the symbol's name instead of checking whether the
703 symbol is in the .plt section because some systems have @plt
704 symbols in the .text section. */
705 if (len > 4 && strcmp (target_name + len - 4, "@plt") == 0)
708 htab = (htab_t) objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data);
711 htab = htab_create_alloc_ex (1, elf_gnu_ifunc_cache_hash,
712 elf_gnu_ifunc_cache_eq,
713 NULL, &objfile->objfile_obstack,
714 hashtab_obstack_allocate,
715 dummy_obstack_deallocate);
716 set_objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data, htab);
719 entry_local.addr = addr;
720 obstack_grow (&objfile->objfile_obstack, &entry_local,
721 offsetof (struct elf_gnu_ifunc_cache, name));
722 obstack_grow_str0 (&objfile->objfile_obstack, name);
724 = (struct elf_gnu_ifunc_cache *) obstack_finish (&objfile->objfile_obstack);
726 slot = htab_find_slot (htab, entry_p, INSERT);
729 struct elf_gnu_ifunc_cache *entry_found_p
730 = (struct elf_gnu_ifunc_cache *) *slot;
731 struct gdbarch *gdbarch = get_objfile_arch (objfile);
733 if (entry_found_p->addr != addr)
735 /* This case indicates buggy inferior program, the resolved address
736 should never change. */
738 warning (_("gnu-indirect-function \"%s\" has changed its resolved "
739 "function_address from %s to %s"),
740 name, paddress (gdbarch, entry_found_p->addr),
741 paddress (gdbarch, addr));
744 /* New ENTRY_P is here leaked/duplicate in the OBJFILE obstack. */
751 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
752 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
753 is not NULL) and the function returns 1. It returns 0 otherwise.
755 Only the elf_objfile_gnu_ifunc_cache_data hash table is searched by this
759 elf_gnu_ifunc_resolve_by_cache (const char *name, CORE_ADDR *addr_p)
761 for (objfile *objfile : all_objfiles (current_program_space))
764 struct elf_gnu_ifunc_cache *entry_p;
767 htab = (htab_t) objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data);
771 entry_p = ((struct elf_gnu_ifunc_cache *)
772 alloca (sizeof (*entry_p) + strlen (name)));
773 strcpy (entry_p->name, name);
775 slot = htab_find_slot (htab, entry_p, NO_INSERT);
778 entry_p = (struct elf_gnu_ifunc_cache *) *slot;
779 gdb_assert (entry_p != NULL);
782 *addr_p = entry_p->addr;
789 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
790 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
791 is not NULL) and the function returns 1. It returns 0 otherwise.
793 Only the SYMBOL_GOT_PLT_SUFFIX locations are searched by this function.
794 elf_gnu_ifunc_resolve_by_cache must have been already called for NAME to
795 prevent cache entries duplicates. */
798 elf_gnu_ifunc_resolve_by_got (const char *name, CORE_ADDR *addr_p)
801 const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
803 name_got_plt = (char *) alloca (strlen (name) + got_suffix_len + 1);
804 sprintf (name_got_plt, "%s" SYMBOL_GOT_PLT_SUFFIX, name);
806 for (objfile *objfile : all_objfiles (current_program_space))
808 bfd *obfd = objfile->obfd;
809 struct gdbarch *gdbarch = get_objfile_arch (objfile);
810 struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
811 size_t ptr_size = TYPE_LENGTH (ptr_type);
812 CORE_ADDR pointer_address, addr;
814 gdb_byte *buf = (gdb_byte *) alloca (ptr_size);
815 struct bound_minimal_symbol msym;
817 msym = lookup_minimal_symbol (name_got_plt, NULL, objfile);
818 if (msym.minsym == NULL)
820 if (MSYMBOL_TYPE (msym.minsym) != mst_slot_got_plt)
822 pointer_address = BMSYMBOL_VALUE_ADDRESS (msym);
824 plt = bfd_get_section_by_name (obfd, ".plt");
828 if (MSYMBOL_SIZE (msym.minsym) != ptr_size)
830 if (target_read_memory (pointer_address, buf, ptr_size) != 0)
832 addr = extract_typed_address (buf, ptr_type);
833 addr = gdbarch_convert_from_func_ptr_addr (gdbarch, addr,
834 current_top_target ());
835 addr = gdbarch_addr_bits_remove (gdbarch, addr);
837 if (elf_gnu_ifunc_record_cache (name, addr))
848 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
849 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
850 is not NULL) and the function returns 1. It returns 0 otherwise.
852 Both the elf_objfile_gnu_ifunc_cache_data hash table and
853 SYMBOL_GOT_PLT_SUFFIX locations are searched by this function. */
856 elf_gnu_ifunc_resolve_name (const char *name, CORE_ADDR *addr_p)
858 if (elf_gnu_ifunc_resolve_by_cache (name, addr_p))
861 if (elf_gnu_ifunc_resolve_by_got (name, addr_p))
867 /* Call STT_GNU_IFUNC - a function returning addresss of a real function to
868 call. PC is theSTT_GNU_IFUNC resolving function entry. The value returned
869 is the entry point of the resolved STT_GNU_IFUNC target function to call.
873 elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc)
875 const char *name_at_pc;
876 CORE_ADDR start_at_pc, address;
877 struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func;
878 struct value *function, *address_val;
880 struct value *hwcap_val;
882 /* Try first any non-intrusive methods without an inferior call. */
884 if (find_pc_partial_function (pc, &name_at_pc, &start_at_pc, NULL)
885 && start_at_pc == pc)
887 if (elf_gnu_ifunc_resolve_name (name_at_pc, &address))
893 function = allocate_value (func_func_type);
894 VALUE_LVAL (function) = lval_memory;
895 set_value_address (function, pc);
897 /* STT_GNU_IFUNC resolver functions usually receive the HWCAP vector as
898 parameter. FUNCTION is the function entry address. ADDRESS may be a
899 function descriptor. */
901 target_auxv_search (current_top_target (), AT_HWCAP, &hwcap);
902 hwcap_val = value_from_longest (builtin_type (gdbarch)
903 ->builtin_unsigned_long, hwcap);
904 address_val = call_function_by_hand (function, NULL, hwcap_val);
905 address = value_as_address (address_val);
906 address = gdbarch_convert_from_func_ptr_addr (gdbarch, address, current_top_target ());
907 address = gdbarch_addr_bits_remove (gdbarch, address);
910 elf_gnu_ifunc_record_cache (name_at_pc, address);
915 /* Handle inferior hit of bp_gnu_ifunc_resolver, see its definition. */
918 elf_gnu_ifunc_resolver_stop (struct breakpoint *b)
920 struct breakpoint *b_return;
921 struct frame_info *prev_frame = get_prev_frame (get_current_frame ());
922 struct frame_id prev_frame_id = get_stack_frame_id (prev_frame);
923 CORE_ADDR prev_pc = get_frame_pc (prev_frame);
924 int thread_id = inferior_thread ()->global_num;
926 gdb_assert (b->type == bp_gnu_ifunc_resolver);
928 for (b_return = b->related_breakpoint; b_return != b;
929 b_return = b_return->related_breakpoint)
931 gdb_assert (b_return->type == bp_gnu_ifunc_resolver_return);
932 gdb_assert (b_return->loc != NULL && b_return->loc->next == NULL);
933 gdb_assert (frame_id_p (b_return->frame_id));
935 if (b_return->thread == thread_id
936 && b_return->loc->requested_address == prev_pc
937 && frame_id_eq (b_return->frame_id, prev_frame_id))
943 /* No need to call find_pc_line for symbols resolving as this is only
944 a helper breakpointer never shown to the user. */
947 sal.pspace = current_inferior ()->pspace;
949 sal.section = find_pc_overlay (sal.pc);
952 = set_momentary_breakpoint (get_frame_arch (prev_frame), sal,
954 bp_gnu_ifunc_resolver_return).release ();
956 /* set_momentary_breakpoint invalidates PREV_FRAME. */
959 /* Add new b_return to the ring list b->related_breakpoint. */
960 gdb_assert (b_return->related_breakpoint == b_return);
961 b_return->related_breakpoint = b->related_breakpoint;
962 b->related_breakpoint = b_return;
966 /* Handle inferior hit of bp_gnu_ifunc_resolver_return, see its definition. */
969 elf_gnu_ifunc_resolver_return_stop (struct breakpoint *b)
971 thread_info *thread = inferior_thread ();
972 struct gdbarch *gdbarch = get_frame_arch (get_current_frame ());
973 struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func;
974 struct type *value_type = TYPE_TARGET_TYPE (func_func_type);
975 struct regcache *regcache = get_thread_regcache (thread);
976 struct value *func_func;
978 CORE_ADDR resolved_address, resolved_pc;
980 gdb_assert (b->type == bp_gnu_ifunc_resolver_return);
982 while (b->related_breakpoint != b)
984 struct breakpoint *b_next = b->related_breakpoint;
988 case bp_gnu_ifunc_resolver:
990 case bp_gnu_ifunc_resolver_return:
991 delete_breakpoint (b);
994 internal_error (__FILE__, __LINE__,
995 _("handle_inferior_event: Invalid "
996 "gnu-indirect-function breakpoint type %d"),
1001 gdb_assert (b->type == bp_gnu_ifunc_resolver);
1002 gdb_assert (b->loc->next == NULL);
1004 func_func = allocate_value (func_func_type);
1005 VALUE_LVAL (func_func) = lval_memory;
1006 set_value_address (func_func, b->loc->related_address);
1008 value = allocate_value (value_type);
1009 gdbarch_return_value (gdbarch, func_func, value_type, regcache,
1010 value_contents_raw (value), NULL);
1011 resolved_address = value_as_address (value);
1012 resolved_pc = gdbarch_convert_from_func_ptr_addr (gdbarch,
1014 current_top_target ());
1015 resolved_pc = gdbarch_addr_bits_remove (gdbarch, resolved_pc);
1017 gdb_assert (current_program_space == b->pspace || b->pspace == NULL);
1018 elf_gnu_ifunc_record_cache (event_location_to_string (b->location.get ()),
1021 b->type = bp_breakpoint;
1022 update_breakpoint_locations (b, current_program_space,
1023 find_function_start_sal (resolved_pc, NULL, true),
1027 /* A helper function for elf_symfile_read that reads the minimal
1031 elf_read_minimal_symbols (struct objfile *objfile, int symfile_flags,
1032 const struct elfinfo *ei)
1034 bfd *synth_abfd, *abfd = objfile->obfd;
1035 long symcount = 0, dynsymcount = 0, synthcount, storage_needed;
1036 asymbol **symbol_table = NULL, **dyn_symbol_table = NULL;
1038 struct dbx_symfile_info *dbx;
1040 if (symtab_create_debug)
1042 fprintf_unfiltered (gdb_stdlog,
1043 "Reading minimal symbols of objfile %s ...\n",
1044 objfile_name (objfile));
1047 /* If we already have minsyms, then we can skip some work here.
1048 However, if there were stabs or mdebug sections, we go ahead and
1049 redo all the work anyway, because the psym readers for those
1050 kinds of debuginfo need extra information found here. This can
1051 go away once all types of symbols are in the per-BFD object. */
1052 if (objfile->per_bfd->minsyms_read
1053 && ei->stabsect == NULL
1054 && ei->mdebugsect == NULL)
1056 if (symtab_create_debug)
1057 fprintf_unfiltered (gdb_stdlog,
1058 "... minimal symbols previously read\n");
1062 minimal_symbol_reader reader (objfile);
1064 /* Allocate struct to keep track of the symfile. */
1065 dbx = XCNEW (struct dbx_symfile_info);
1066 set_objfile_data (objfile, dbx_objfile_data_key, dbx);
1068 /* Process the normal ELF symbol table first. */
1070 storage_needed = bfd_get_symtab_upper_bound (objfile->obfd);
1071 if (storage_needed < 0)
1072 error (_("Can't read symbols from %s: %s"),
1073 bfd_get_filename (objfile->obfd),
1074 bfd_errmsg (bfd_get_error ()));
1076 if (storage_needed > 0)
1078 /* Memory gets permanently referenced from ABFD after
1079 bfd_canonicalize_symtab so it must not get freed before ABFD gets. */
1081 symbol_table = (asymbol **) bfd_alloc (abfd, storage_needed);
1082 symcount = bfd_canonicalize_symtab (objfile->obfd, symbol_table);
1085 error (_("Can't read symbols from %s: %s"),
1086 bfd_get_filename (objfile->obfd),
1087 bfd_errmsg (bfd_get_error ()));
1089 elf_symtab_read (reader, objfile, ST_REGULAR, symcount, symbol_table,
1093 /* Add the dynamic symbols. */
1095 storage_needed = bfd_get_dynamic_symtab_upper_bound (objfile->obfd);
1097 if (storage_needed > 0)
1099 /* Memory gets permanently referenced from ABFD after
1100 bfd_get_synthetic_symtab so it must not get freed before ABFD gets.
1101 It happens only in the case when elf_slurp_reloc_table sees
1102 asection->relocation NULL. Determining which section is asection is
1103 done by _bfd_elf_get_synthetic_symtab which is all a bfd
1104 implementation detail, though. */
1106 dyn_symbol_table = (asymbol **) bfd_alloc (abfd, storage_needed);
1107 dynsymcount = bfd_canonicalize_dynamic_symtab (objfile->obfd,
1110 if (dynsymcount < 0)
1111 error (_("Can't read symbols from %s: %s"),
1112 bfd_get_filename (objfile->obfd),
1113 bfd_errmsg (bfd_get_error ()));
1115 elf_symtab_read (reader, objfile, ST_DYNAMIC, dynsymcount,
1116 dyn_symbol_table, false);
1118 elf_rel_plt_read (reader, objfile, dyn_symbol_table);
1121 /* Contrary to binutils --strip-debug/--only-keep-debug the strip command from
1122 elfutils (eu-strip) moves even the .symtab section into the .debug file.
1124 bfd_get_synthetic_symtab on ppc64 for each function descriptor ELF symbol
1125 'name' creates a new BSF_SYNTHETIC ELF symbol '.name' with its code
1126 address. But with eu-strip files bfd_get_synthetic_symtab would fail to
1127 read the code address from .opd while it reads the .symtab section from
1128 a separate debug info file as the .opd section is SHT_NOBITS there.
1130 With SYNTH_ABFD the .opd section will be read from the original
1131 backlinked binary where it is valid. */
1133 if (objfile->separate_debug_objfile_backlink)
1134 synth_abfd = objfile->separate_debug_objfile_backlink->obfd;
1138 /* Add synthetic symbols - for instance, names for any PLT entries. */
1140 synthcount = bfd_get_synthetic_symtab (synth_abfd, symcount, symbol_table,
1141 dynsymcount, dyn_symbol_table,
1147 std::unique_ptr<asymbol *[]>
1148 synth_symbol_table (new asymbol *[synthcount]);
1149 for (i = 0; i < synthcount; i++)
1150 synth_symbol_table[i] = synthsyms + i;
1151 elf_symtab_read (reader, objfile, ST_SYNTHETIC, synthcount,
1152 synth_symbol_table.get (), true);
1158 /* Install any minimal symbols that have been collected as the current
1159 minimal symbols for this objfile. The debug readers below this point
1160 should not generate new minimal symbols; if they do it's their
1161 responsibility to install them. "mdebug" appears to be the only one
1162 which will do this. */
1166 if (symtab_create_debug)
1167 fprintf_unfiltered (gdb_stdlog, "Done reading minimal symbols.\n");
1170 /* Scan and build partial symbols for a symbol file.
1171 We have been initialized by a call to elf_symfile_init, which
1172 currently does nothing.
1174 This function only does the minimum work necessary for letting the
1175 user "name" things symbolically; it does not read the entire symtab.
1176 Instead, it reads the external and static symbols and puts them in partial
1177 symbol tables. When more extensive information is requested of a
1178 file, the corresponding partial symbol table is mutated into a full
1179 fledged symbol table by going back and reading the symbols
1182 We look for sections with specific names, to tell us what debug
1183 format to look for: FIXME!!!
1185 elfstab_build_psymtabs() handles STABS symbols;
1186 mdebug_build_psymtabs() handles ECOFF debugging information.
1188 Note that ELF files have a "minimal" symbol table, which looks a lot
1189 like a COFF symbol table, but has only the minimal information necessary
1190 for linking. We process this also, and use the information to
1191 build gdb's minimal symbol table. This gives us some minimal debugging
1192 capability even for files compiled without -g. */
1195 elf_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
1197 bfd *abfd = objfile->obfd;
1200 memset ((char *) &ei, 0, sizeof (ei));
1201 if (!(objfile->flags & OBJF_READNEVER))
1202 bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei);
1204 elf_read_minimal_symbols (objfile, symfile_flags, &ei);
1206 /* ELF debugging information is inserted into the psymtab in the
1207 order of least informative first - most informative last. Since
1208 the psymtab table is searched `most recent insertion first' this
1209 increases the probability that more detailed debug information
1210 for a section is found.
1212 For instance, an object file might contain both .mdebug (XCOFF)
1213 and .debug_info (DWARF2) sections then .mdebug is inserted first
1214 (searched last) and DWARF2 is inserted last (searched first). If
1215 we don't do this then the XCOFF info is found first - for code in
1216 an included file XCOFF info is useless. */
1220 const struct ecoff_debug_swap *swap;
1222 /* .mdebug section, presumably holding ECOFF debugging
1224 swap = get_elf_backend_data (abfd)->elf_backend_ecoff_debug_swap;
1226 elfmdebug_build_psymtabs (objfile, swap, ei.mdebugsect);
1232 /* Stab sections have an associated string table that looks like
1233 a separate section. */
1234 str_sect = bfd_get_section_by_name (abfd, ".stabstr");
1236 /* FIXME should probably warn about a stab section without a stabstr. */
1238 elfstab_build_psymtabs (objfile,
1241 bfd_section_size (abfd, str_sect));
1244 if (dwarf2_has_info (objfile, NULL))
1246 dw_index_kind index_kind;
1248 /* elf_sym_fns_gdb_index cannot handle simultaneous non-DWARF
1249 debug information present in OBJFILE. If there is such debug
1250 info present never use an index. */
1251 if (!objfile_has_partial_symbols (objfile)
1252 && dwarf2_initialize_objfile (objfile, &index_kind))
1256 case dw_index_kind::GDB_INDEX:
1257 objfile_set_sym_fns (objfile, &elf_sym_fns_gdb_index);
1259 case dw_index_kind::DEBUG_NAMES:
1260 objfile_set_sym_fns (objfile, &elf_sym_fns_debug_names);
1266 /* It is ok to do this even if the stabs reader made some
1267 partial symbols, because OBJF_PSYMTABS_READ has not been
1268 set, and so our lazy reader function will still be called
1270 objfile_set_sym_fns (objfile, &elf_sym_fns_lazy_psyms);
1273 /* If the file has its own symbol tables it has no separate debug
1274 info. `.dynsym'/`.symtab' go to MSYMBOLS, `.debug_info' goes to
1275 SYMTABS/PSYMTABS. `.gnu_debuglink' may no longer be present with
1276 `.note.gnu.build-id'.
1278 .gnu_debugdata is !objfile_has_partial_symbols because it contains only
1279 .symtab, not .debug_* section. But if we already added .gnu_debugdata as
1280 an objfile via find_separate_debug_file_in_section there was no separate
1281 debug info available. Therefore do not attempt to search for another one,
1282 objfile->separate_debug_objfile->separate_debug_objfile GDB guarantees to
1283 be NULL and we would possibly violate it. */
1285 else if (!objfile_has_partial_symbols (objfile)
1286 && objfile->separate_debug_objfile == NULL
1287 && objfile->separate_debug_objfile_backlink == NULL)
1289 std::string debugfile = find_separate_debug_file_by_buildid (objfile);
1291 if (debugfile.empty ())
1292 debugfile = find_separate_debug_file_by_debuglink (objfile);
1294 if (!debugfile.empty ())
1296 gdb_bfd_ref_ptr debug_bfd (symfile_bfd_open (debugfile.c_str ()));
1298 symbol_file_add_separate (debug_bfd.get (), debugfile.c_str (),
1299 symfile_flags, objfile);
1304 /* Callback to lazily read psymtabs. */
1307 read_psyms (struct objfile *objfile)
1309 if (dwarf2_has_info (objfile, NULL))
1310 dwarf2_build_psymtabs (objfile);
1313 /* Initialize anything that needs initializing when a completely new symbol
1314 file is specified (not just adding some symbols from another file, e.g. a
1317 We reinitialize buildsym, since we may be reading stabs from an ELF
1321 elf_new_init (struct objfile *ignore)
1323 stabsread_new_init ();
1326 /* Perform any local cleanups required when we are done with a particular
1327 objfile. I.E, we are in the process of discarding all symbol information
1328 for an objfile, freeing up all memory held for it, and unlinking the
1329 objfile struct from the global list of known objfiles. */
1332 elf_symfile_finish (struct objfile *objfile)
1336 /* ELF specific initialization routine for reading symbols. */
1339 elf_symfile_init (struct objfile *objfile)
1341 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
1342 find this causes a significant slowdown in gdb then we could
1343 set it in the debug symbol readers only when necessary. */
1344 objfile->flags |= OBJF_REORDERED;
1347 /* Implementation of `sym_get_probes', as documented in symfile.h. */
1349 static const std::vector<probe *> &
1350 elf_get_probes (struct objfile *objfile)
1352 std::vector<probe *> *probes_per_bfd;
1354 /* Have we parsed this objfile's probes already? */
1355 probes_per_bfd = (std::vector<probe *> *) bfd_data (objfile->obfd, probe_key);
1357 if (probes_per_bfd == NULL)
1359 probes_per_bfd = new std::vector<probe *>;
1361 /* Here we try to gather information about all types of probes from the
1363 for (const static_probe_ops *ops : all_static_probe_ops)
1364 ops->get_probes (probes_per_bfd, objfile);
1366 set_bfd_data (objfile->obfd, probe_key, probes_per_bfd);
1369 return *probes_per_bfd;
1372 /* Helper function used to free the space allocated for storing SystemTap
1373 probe information. */
1376 probe_key_free (bfd *abfd, void *d)
1378 std::vector<probe *> *probes = (std::vector<probe *> *) d;
1380 for (probe *p : *probes)
1388 /* Implementation `sym_probe_fns', as documented in symfile.h. */
1390 static const struct sym_probe_fns elf_probe_fns =
1392 elf_get_probes, /* sym_get_probes */
1395 /* Register that we are able to handle ELF object file formats. */
1397 static const struct sym_fns elf_sym_fns =
1399 elf_new_init, /* init anything gbl to entire symtab */
1400 elf_symfile_init, /* read initial info, setup for sym_read() */
1401 elf_symfile_read, /* read a symbol file into symtab */
1402 NULL, /* sym_read_psymbols */
1403 elf_symfile_finish, /* finished with file, cleanup */
1404 default_symfile_offsets, /* Translate ext. to int. relocation */
1405 elf_symfile_segments, /* Get segment information from a file. */
1407 default_symfile_relocate, /* Relocate a debug section. */
1408 &elf_probe_fns, /* sym_probe_fns */
1412 /* The same as elf_sym_fns, but not registered and lazily reads
1415 const struct sym_fns elf_sym_fns_lazy_psyms =
1417 elf_new_init, /* init anything gbl to entire symtab */
1418 elf_symfile_init, /* read initial info, setup for sym_read() */
1419 elf_symfile_read, /* read a symbol file into symtab */
1420 read_psyms, /* sym_read_psymbols */
1421 elf_symfile_finish, /* finished with file, cleanup */
1422 default_symfile_offsets, /* Translate ext. to int. relocation */
1423 elf_symfile_segments, /* Get segment information from a file. */
1425 default_symfile_relocate, /* Relocate a debug section. */
1426 &elf_probe_fns, /* sym_probe_fns */
1430 /* The same as elf_sym_fns, but not registered and uses the
1431 DWARF-specific GNU index rather than psymtab. */
1432 const struct sym_fns elf_sym_fns_gdb_index =
1434 elf_new_init, /* init anything gbl to entire symab */
1435 elf_symfile_init, /* read initial info, setup for sym_red() */
1436 elf_symfile_read, /* read a symbol file into symtab */
1437 NULL, /* sym_read_psymbols */
1438 elf_symfile_finish, /* finished with file, cleanup */
1439 default_symfile_offsets, /* Translate ext. to int. relocatin */
1440 elf_symfile_segments, /* Get segment information from a file. */
1442 default_symfile_relocate, /* Relocate a debug section. */
1443 &elf_probe_fns, /* sym_probe_fns */
1444 &dwarf2_gdb_index_functions
1447 /* The same as elf_sym_fns, but not registered and uses the
1448 DWARF-specific .debug_names index rather than psymtab. */
1449 const struct sym_fns elf_sym_fns_debug_names =
1451 elf_new_init, /* init anything gbl to entire symab */
1452 elf_symfile_init, /* read initial info, setup for sym_red() */
1453 elf_symfile_read, /* read a symbol file into symtab */
1454 NULL, /* sym_read_psymbols */
1455 elf_symfile_finish, /* finished with file, cleanup */
1456 default_symfile_offsets, /* Translate ext. to int. relocatin */
1457 elf_symfile_segments, /* Get segment information from a file. */
1459 default_symfile_relocate, /* Relocate a debug section. */
1460 &elf_probe_fns, /* sym_probe_fns */
1461 &dwarf2_debug_names_functions
1464 /* STT_GNU_IFUNC resolver vector to be installed to gnu_ifunc_fns_p. */
1466 static const struct gnu_ifunc_fns elf_gnu_ifunc_fns =
1468 elf_gnu_ifunc_resolve_addr,
1469 elf_gnu_ifunc_resolve_name,
1470 elf_gnu_ifunc_resolver_stop,
1471 elf_gnu_ifunc_resolver_return_stop
1475 _initialize_elfread (void)
1477 probe_key = register_bfd_data_with_cleanup (NULL, probe_key_free);
1478 add_symtab_fns (bfd_target_elf_flavour, &elf_sym_fns);
1480 elf_objfile_gnu_ifunc_cache_data = register_objfile_data ();
1481 gnu_ifunc_fns_p = &elf_gnu_ifunc_fns;