1 /* Read ELF (Executable and Linking Format) object files for GDB.
3 Copyright (C) 1991-2018 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"
32 #include "stabsread.h"
33 #include "gdb-stabs.h"
34 #include "complaints.h"
37 #include "filenames.h"
39 #include "arch-utils.h"
43 #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)
125 if ((bfd_get_section_flags (abfd, sect) & SEC_ALLOC) == 0)
128 vma = bfd_get_section_vma (abfd, sect);
130 for (j = 0; j < num_segments; j++)
131 if (segments[j]->p_memsz > 0
132 && vma >= segments[j]->p_vaddr
133 && (vma - segments[j]->p_vaddr) < segments[j]->p_memsz)
135 data->segment_info[i] = j + 1;
139 /* We should have found a segment for every non-empty section.
140 If we haven't, we will not relocate this section by any
141 offsets we apply to the segments. As an exception, do not
142 warn about SHT_NOBITS sections; in normal ELF execution
143 environments, SHT_NOBITS means zero-initialized and belongs
144 in a segment, but in no-OS environments some tools (e.g. ARM
145 RealView) use SHT_NOBITS for uninitialized data. Since it is
146 uninitialized, it doesn't need a program header. Such
147 binaries are not relocatable. */
148 if (bfd_get_section_size (sect) > 0 && j == num_segments
149 && (bfd_get_section_flags (abfd, sect) & SEC_LOAD) != 0)
150 warning (_("Loadable section \"%s\" outside of ELF segments"),
151 bfd_section_name (abfd, sect));
157 /* We are called once per section from elf_symfile_read. We
158 need to examine each section we are passed, check to see
159 if it is something we are interested in processing, and
160 if so, stash away some access information for the section.
162 For now we recognize the dwarf debug information sections and
163 line number sections from matching their section names. The
164 ELF definition is no real help here since it has no direct
165 knowledge of DWARF (by design, so any debugging format can be
168 We also recognize the ".stab" sections used by the Sun compilers
169 released with Solaris 2.
171 FIXME: The section names should not be hardwired strings (what
172 should they be? I don't think most object file formats have enough
173 section flags to specify what kind of debug section it is.
177 elf_locate_sections (bfd *ignore_abfd, asection *sectp, void *eip)
181 ei = (struct elfinfo *) eip;
182 if (strcmp (sectp->name, ".stab") == 0)
184 ei->stabsect = sectp;
186 else if (strcmp (sectp->name, ".mdebug") == 0)
188 ei->mdebugsect = sectp;
192 static struct minimal_symbol *
193 record_minimal_symbol (minimal_symbol_reader &reader,
194 const char *name, int name_len, bool copy_name,
196 enum minimal_symbol_type ms_type,
197 asection *bfd_section, struct objfile *objfile)
199 struct gdbarch *gdbarch = get_objfile_arch (objfile);
201 if (ms_type == mst_text || ms_type == mst_file_text
202 || ms_type == mst_text_gnu_ifunc)
203 address = gdbarch_addr_bits_remove (gdbarch, address);
205 return reader.record_full (name, name_len, copy_name, address,
207 gdb_bfd_section_index (objfile->obfd,
211 /* Read the symbol table of an ELF file.
213 Given an objfile, a symbol table, and a flag indicating whether the
214 symbol table contains regular, dynamic, or synthetic symbols, add all
215 the global function and data symbols to the minimal symbol table.
217 In stabs-in-ELF, as implemented by Sun, there are some local symbols
218 defined in the ELF symbol table, which can be used to locate
219 the beginnings of sections from each ".o" file that was linked to
220 form the executable objfile. We gather any such info and record it
221 in data structures hung off the objfile's private data. */
225 #define ST_SYNTHETIC 2
228 elf_symtab_read (minimal_symbol_reader &reader,
229 struct objfile *objfile, int type,
230 long number_of_symbols, asymbol **symbol_table,
233 struct gdbarch *gdbarch = get_objfile_arch (objfile);
237 enum minimal_symbol_type ms_type;
238 /* Name of the last file symbol. This is either a constant string or is
239 saved on the objfile's filename cache. */
240 const char *filesymname = "";
241 int stripped = (bfd_get_symcount (objfile->obfd) == 0);
242 int elf_make_msymbol_special_p
243 = gdbarch_elf_make_msymbol_special_p (gdbarch);
245 for (i = 0; i < number_of_symbols; i++)
247 sym = symbol_table[i];
248 if (sym->name == NULL || *sym->name == '\0')
250 /* Skip names that don't exist (shouldn't happen), or names
251 that are null strings (may happen). */
255 /* Skip "special" symbols, e.g. ARM mapping symbols. These are
256 symbols which do not correspond to objects in the symbol table,
257 but have some other target-specific meaning. */
258 if (bfd_is_target_special_symbol (objfile->obfd, sym))
260 if (gdbarch_record_special_symbol_p (gdbarch))
261 gdbarch_record_special_symbol (gdbarch, objfile, sym);
265 if (type == ST_DYNAMIC
266 && sym->section == bfd_und_section_ptr
267 && (sym->flags & BSF_FUNCTION))
269 struct minimal_symbol *msym;
270 bfd *abfd = objfile->obfd;
273 /* Symbol is a reference to a function defined in
275 If its value is non zero then it is usually the address
276 of the corresponding entry in the procedure linkage table,
277 plus the desired section offset.
278 If its value is zero then the dynamic linker has to resolve
279 the symbol. We are unable to find any meaningful address
280 for this symbol in the executable file, so we skip it. */
281 symaddr = sym->value;
285 /* sym->section is the undefined section. However, we want to
286 record the section where the PLT stub resides with the
287 minimal symbol. Search the section table for the one that
288 covers the stub's address. */
289 for (sect = abfd->sections; sect != NULL; sect = sect->next)
291 if ((bfd_get_section_flags (abfd, sect) & SEC_ALLOC) == 0)
294 if (symaddr >= bfd_get_section_vma (abfd, sect)
295 && symaddr < bfd_get_section_vma (abfd, sect)
296 + bfd_get_section_size (sect))
302 /* On ia64-hpux, we have discovered that the system linker
303 adds undefined symbols with nonzero addresses that cannot
304 be right (their address points inside the code of another
305 function in the .text section). This creates problems
306 when trying to determine which symbol corresponds to
309 We try to detect those buggy symbols by checking which
310 section we think they correspond to. Normally, PLT symbols
311 are stored inside their own section, and the typical name
312 for that section is ".plt". So, if there is a ".plt"
313 section, and yet the section name of our symbol does not
314 start with ".plt", we ignore that symbol. */
315 if (!startswith (sect->name, ".plt")
316 && bfd_get_section_by_name (abfd, ".plt") != NULL)
319 msym = record_minimal_symbol
320 (reader, sym->name, strlen (sym->name), copy_names,
321 symaddr, mst_solib_trampoline, sect, objfile);
324 msym->filename = filesymname;
325 if (elf_make_msymbol_special_p)
326 gdbarch_elf_make_msymbol_special (gdbarch, sym, msym);
331 /* If it is a nonstripped executable, do not enter dynamic
332 symbols, as the dynamic symbol table is usually a subset
333 of the main symbol table. */
334 if (type == ST_DYNAMIC && !stripped)
336 if (sym->flags & BSF_FILE)
339 = (const char *) bcache (sym->name, strlen (sym->name) + 1,
340 objfile->per_bfd->filename_cache);
342 else if (sym->flags & BSF_SECTION_SYM)
344 else if (sym->flags & (BSF_GLOBAL | BSF_LOCAL | BSF_WEAK
347 struct minimal_symbol *msym;
349 /* Select global/local/weak symbols. Note that bfd puts abs
350 symbols in their own section, so all symbols we are
351 interested in will have a section. */
352 /* Bfd symbols are section relative. */
353 symaddr = sym->value + sym->section->vma;
354 /* For non-absolute symbols, use the type of the section
355 they are relative to, to intuit text/data. Bfd provides
356 no way of figuring this out for absolute symbols. */
357 if (sym->section == bfd_abs_section_ptr)
359 /* This is a hack to get the minimal symbol type
360 right for Irix 5, which has absolute addresses
361 with special section indices for dynamic symbols.
363 NOTE: uweigand-20071112: Synthetic symbols do not
364 have an ELF-private part, so do not touch those. */
365 unsigned int shndx = type == ST_SYNTHETIC ? 0 :
366 ((elf_symbol_type *) sym)->internal_elf_sym.st_shndx;
376 case SHN_MIPS_ACOMMON:
383 /* If it is an Irix dynamic symbol, skip section name
384 symbols, relocate all others by section offset. */
385 if (ms_type != mst_abs)
387 if (sym->name[0] == '.')
391 else if (sym->section->flags & SEC_CODE)
393 if (sym->flags & (BSF_GLOBAL | BSF_WEAK | BSF_GNU_UNIQUE))
395 if (sym->flags & BSF_GNU_INDIRECT_FUNCTION)
396 ms_type = mst_text_gnu_ifunc;
400 /* The BSF_SYNTHETIC check is there to omit ppc64 function
401 descriptors mistaken for static functions starting with 'L'.
403 else if ((sym->name[0] == '.' && sym->name[1] == 'L'
404 && (sym->flags & BSF_SYNTHETIC) == 0)
405 || ((sym->flags & BSF_LOCAL)
406 && sym->name[0] == '$'
407 && sym->name[1] == 'L'))
408 /* Looks like a compiler-generated label. Skip
409 it. The assembler should be skipping these (to
410 keep executables small), but apparently with
411 gcc on the (deleted) delta m88k SVR4, it loses.
412 So to have us check too should be harmless (but
413 I encourage people to fix this in the assembler
414 instead of adding checks here). */
418 ms_type = mst_file_text;
421 else if (sym->section->flags & SEC_ALLOC)
423 if (sym->flags & (BSF_GLOBAL | BSF_WEAK | BSF_GNU_UNIQUE))
425 if (sym->section->flags & SEC_LOAD)
434 else if (sym->flags & BSF_LOCAL)
436 if (sym->section->flags & SEC_LOAD)
438 ms_type = mst_file_data;
442 ms_type = mst_file_bss;
447 ms_type = mst_unknown;
452 /* FIXME: Solaris2 shared libraries include lots of
453 odd "absolute" and "undefined" symbols, that play
454 hob with actions like finding what function the PC
455 is in. Ignore them if they aren't text, data, or bss. */
456 /* ms_type = mst_unknown; */
457 continue; /* Skip this symbol. */
459 msym = record_minimal_symbol
460 (reader, sym->name, strlen (sym->name), copy_names, symaddr,
461 ms_type, sym->section, objfile);
465 /* NOTE: uweigand-20071112: A synthetic symbol does not have an
467 if (type != ST_SYNTHETIC)
469 /* Pass symbol size field in via BFD. FIXME!!! */
470 elf_symbol_type *elf_sym = (elf_symbol_type *) sym;
471 SET_MSYMBOL_SIZE (msym, elf_sym->internal_elf_sym.st_size);
474 msym->filename = filesymname;
475 if (elf_make_msymbol_special_p)
476 gdbarch_elf_make_msymbol_special (gdbarch, sym, msym);
479 /* If we see a default versioned symbol, install it under
480 its version-less name. */
483 const char *atsign = strchr (sym->name, '@');
485 if (atsign != NULL && atsign[1] == '@' && atsign > sym->name)
487 int len = atsign - sym->name;
489 record_minimal_symbol (reader, sym->name, len, true, symaddr,
490 ms_type, sym->section, objfile);
494 /* For @plt symbols, also record a trampoline to the
495 destination symbol. The @plt symbol will be used in
496 disassembly, and the trampoline will be used when we are
497 trying to find the target. */
498 if (msym && ms_type == mst_text && type == ST_SYNTHETIC)
500 int len = strlen (sym->name);
502 if (len > 4 && strcmp (sym->name + len - 4, "@plt") == 0)
504 struct minimal_symbol *mtramp;
506 mtramp = record_minimal_symbol (reader, sym->name, len - 4,
508 mst_solib_trampoline,
509 sym->section, objfile);
512 SET_MSYMBOL_SIZE (mtramp, MSYMBOL_SIZE (msym));
513 mtramp->created_by_gdb = 1;
514 mtramp->filename = filesymname;
515 if (elf_make_msymbol_special_p)
516 gdbarch_elf_make_msymbol_special (gdbarch,
525 /* Build minimal symbols named `function@got.plt' (see SYMBOL_GOT_PLT_SUFFIX)
526 for later look ups of which function to call when user requests
527 a STT_GNU_IFUNC function. As the STT_GNU_IFUNC type is found at the target
528 library defining `function' we cannot yet know while reading OBJFILE which
529 of the SYMBOL_GOT_PLT_SUFFIX entries will be needed and later
530 DYN_SYMBOL_TABLE is no longer easily available for OBJFILE. */
533 elf_rel_plt_read (minimal_symbol_reader &reader,
534 struct objfile *objfile, asymbol **dyn_symbol_table)
536 bfd *obfd = objfile->obfd;
537 const struct elf_backend_data *bed = get_elf_backend_data (obfd);
538 asection *plt, *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 plt = bfd_get_section_by_name (obfd, ".plt");
551 plt_elf_idx = elf_section_data (plt)->this_idx;
553 got_plt = bfd_get_section_by_name (obfd, ".got.plt");
556 /* For platforms where there is no separate .got.plt. */
557 got_plt = bfd_get_section_by_name (obfd, ".got");
562 /* This search algorithm is from _bfd_elf_canonicalize_dynamic_reloc. */
563 for (relplt = obfd->sections; relplt != NULL; relplt = relplt->next)
564 if (elf_section_data (relplt)->this_hdr.sh_info == plt_elf_idx
565 && (elf_section_data (relplt)->this_hdr.sh_type == SHT_REL
566 || elf_section_data (relplt)->this_hdr.sh_type == SHT_RELA))
571 if (! bed->s->slurp_reloc_table (obfd, relplt, dyn_symbol_table, TRUE))
574 std::string string_buffer;
576 reloc_count = relplt->size / elf_section_data (relplt)->this_hdr.sh_entsize;
577 for (reloc = 0; reloc < reloc_count; reloc++)
580 struct minimal_symbol *msym;
582 const char *got_suffix = SYMBOL_GOT_PLT_SUFFIX;
583 const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
585 name = bfd_asymbol_name (*relplt->relocation[reloc].sym_ptr_ptr);
586 address = relplt->relocation[reloc].address;
588 /* Does the pointer reside in the .got.plt section? */
589 if (!(bfd_get_section_vma (obfd, got_plt) <= address
590 && address < bfd_get_section_vma (obfd, got_plt)
591 + bfd_get_section_size (got_plt)))
594 /* We cannot check if NAME is a reference to mst_text_gnu_ifunc as in
595 OBJFILE the symbol is undefined and the objfile having NAME defined
596 may not yet have been loaded. */
598 string_buffer.assign (name);
599 string_buffer.append (got_suffix, got_suffix + got_suffix_len);
601 msym = record_minimal_symbol (reader, string_buffer.c_str (),
602 string_buffer.size (),
603 true, address, mst_slot_got_plt, got_plt,
606 SET_MSYMBOL_SIZE (msym, ptr_size);
610 /* The data pointer is htab_t for gnu_ifunc_record_cache_unchecked. */
612 static const struct objfile_data *elf_objfile_gnu_ifunc_cache_data;
614 /* Map function names to CORE_ADDR in elf_objfile_gnu_ifunc_cache_data. */
616 struct elf_gnu_ifunc_cache
618 /* This is always a function entry address, not a function descriptor. */
624 /* htab_hash for elf_objfile_gnu_ifunc_cache_data. */
627 elf_gnu_ifunc_cache_hash (const void *a_voidp)
629 const struct elf_gnu_ifunc_cache *a
630 = (const struct elf_gnu_ifunc_cache *) a_voidp;
632 return htab_hash_string (a->name);
635 /* htab_eq for elf_objfile_gnu_ifunc_cache_data. */
638 elf_gnu_ifunc_cache_eq (const void *a_voidp, const void *b_voidp)
640 const struct elf_gnu_ifunc_cache *a
641 = (const struct elf_gnu_ifunc_cache *) a_voidp;
642 const struct elf_gnu_ifunc_cache *b
643 = (const struct elf_gnu_ifunc_cache *) b_voidp;
645 return strcmp (a->name, b->name) == 0;
648 /* Record the target function address of a STT_GNU_IFUNC function NAME is the
649 function entry address ADDR. Return 1 if NAME and ADDR are considered as
650 valid and therefore they were successfully recorded, return 0 otherwise.
652 Function does not expect a duplicate entry. Use
653 elf_gnu_ifunc_resolve_by_cache first to check if the entry for NAME already
657 elf_gnu_ifunc_record_cache (const char *name, CORE_ADDR addr)
659 struct bound_minimal_symbol msym;
661 struct objfile *objfile;
663 struct elf_gnu_ifunc_cache entry_local, *entry_p;
666 msym = lookup_minimal_symbol_by_pc (addr);
667 if (msym.minsym == NULL)
669 if (BMSYMBOL_VALUE_ADDRESS (msym) != addr)
671 /* minimal symbols have always SYMBOL_OBJ_SECTION non-NULL. */
672 sect = MSYMBOL_OBJ_SECTION (msym.objfile, msym.minsym)->the_bfd_section;
673 objfile = msym.objfile;
675 /* If .plt jumps back to .plt the symbol is still deferred for later
676 resolution and it has no use for GDB. Besides ".text" this symbol can
677 reside also in ".opd" for ppc64 function descriptor. */
678 if (strcmp (bfd_get_section_name (objfile->obfd, sect), ".plt") == 0)
681 htab = (htab_t) objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data);
684 htab = htab_create_alloc_ex (1, elf_gnu_ifunc_cache_hash,
685 elf_gnu_ifunc_cache_eq,
686 NULL, &objfile->objfile_obstack,
687 hashtab_obstack_allocate,
688 dummy_obstack_deallocate);
689 set_objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data, htab);
692 entry_local.addr = addr;
693 obstack_grow (&objfile->objfile_obstack, &entry_local,
694 offsetof (struct elf_gnu_ifunc_cache, name));
695 obstack_grow_str0 (&objfile->objfile_obstack, name);
697 = (struct elf_gnu_ifunc_cache *) obstack_finish (&objfile->objfile_obstack);
699 slot = htab_find_slot (htab, entry_p, INSERT);
702 struct elf_gnu_ifunc_cache *entry_found_p
703 = (struct elf_gnu_ifunc_cache *) *slot;
704 struct gdbarch *gdbarch = get_objfile_arch (objfile);
706 if (entry_found_p->addr != addr)
708 /* This case indicates buggy inferior program, the resolved address
709 should never change. */
711 warning (_("gnu-indirect-function \"%s\" has changed its resolved "
712 "function_address from %s to %s"),
713 name, paddress (gdbarch, entry_found_p->addr),
714 paddress (gdbarch, addr));
717 /* New ENTRY_P is here leaked/duplicate in the OBJFILE obstack. */
724 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
725 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
726 is not NULL) and the function returns 1. It returns 0 otherwise.
728 Only the elf_objfile_gnu_ifunc_cache_data hash table is searched by this
732 elf_gnu_ifunc_resolve_by_cache (const char *name, CORE_ADDR *addr_p)
734 struct objfile *objfile;
736 ALL_PSPACE_OBJFILES (current_program_space, objfile)
739 struct elf_gnu_ifunc_cache *entry_p;
742 htab = (htab_t) objfile_data (objfile, elf_objfile_gnu_ifunc_cache_data);
746 entry_p = ((struct elf_gnu_ifunc_cache *)
747 alloca (sizeof (*entry_p) + strlen (name)));
748 strcpy (entry_p->name, name);
750 slot = htab_find_slot (htab, entry_p, NO_INSERT);
753 entry_p = (struct elf_gnu_ifunc_cache *) *slot;
754 gdb_assert (entry_p != NULL);
757 *addr_p = entry_p->addr;
764 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
765 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
766 is not NULL) and the function returns 1. It returns 0 otherwise.
768 Only the SYMBOL_GOT_PLT_SUFFIX locations are searched by this function.
769 elf_gnu_ifunc_resolve_by_cache must have been already called for NAME to
770 prevent cache entries duplicates. */
773 elf_gnu_ifunc_resolve_by_got (const char *name, CORE_ADDR *addr_p)
776 struct objfile *objfile;
777 const size_t got_suffix_len = strlen (SYMBOL_GOT_PLT_SUFFIX);
779 name_got_plt = (char *) alloca (strlen (name) + got_suffix_len + 1);
780 sprintf (name_got_plt, "%s" SYMBOL_GOT_PLT_SUFFIX, name);
782 ALL_PSPACE_OBJFILES (current_program_space, objfile)
784 bfd *obfd = objfile->obfd;
785 struct gdbarch *gdbarch = get_objfile_arch (objfile);
786 struct type *ptr_type = builtin_type (gdbarch)->builtin_data_ptr;
787 size_t ptr_size = TYPE_LENGTH (ptr_type);
788 CORE_ADDR pointer_address, addr;
790 gdb_byte *buf = (gdb_byte *) alloca (ptr_size);
791 struct bound_minimal_symbol msym;
793 msym = lookup_minimal_symbol (name_got_plt, NULL, objfile);
794 if (msym.minsym == NULL)
796 if (MSYMBOL_TYPE (msym.minsym) != mst_slot_got_plt)
798 pointer_address = BMSYMBOL_VALUE_ADDRESS (msym);
800 plt = bfd_get_section_by_name (obfd, ".plt");
804 if (MSYMBOL_SIZE (msym.minsym) != ptr_size)
806 if (target_read_memory (pointer_address, buf, ptr_size) != 0)
808 addr = extract_typed_address (buf, ptr_type);
809 addr = gdbarch_convert_from_func_ptr_addr (gdbarch, addr,
811 addr = gdbarch_addr_bits_remove (gdbarch, addr);
815 if (elf_gnu_ifunc_record_cache (name, addr))
822 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
823 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
824 is not NULL) and the function returns 1. It returns 0 otherwise.
826 Both the elf_objfile_gnu_ifunc_cache_data hash table and
827 SYMBOL_GOT_PLT_SUFFIX locations are searched by this function. */
830 elf_gnu_ifunc_resolve_name (const char *name, CORE_ADDR *addr_p)
832 if (elf_gnu_ifunc_resolve_by_cache (name, addr_p))
835 if (elf_gnu_ifunc_resolve_by_got (name, addr_p))
841 /* Call STT_GNU_IFUNC - a function returning addresss of a real function to
842 call. PC is theSTT_GNU_IFUNC resolving function entry. The value returned
843 is the entry point of the resolved STT_GNU_IFUNC target function to call.
847 elf_gnu_ifunc_resolve_addr (struct gdbarch *gdbarch, CORE_ADDR pc)
849 const char *name_at_pc;
850 CORE_ADDR start_at_pc, address;
851 struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func;
852 struct value *function, *address_val;
854 struct value *hwcap_val;
856 /* Try first any non-intrusive methods without an inferior call. */
858 if (find_pc_partial_function (pc, &name_at_pc, &start_at_pc, NULL)
859 && start_at_pc == pc)
861 if (elf_gnu_ifunc_resolve_name (name_at_pc, &address))
867 function = allocate_value (func_func_type);
868 VALUE_LVAL (function) = lval_memory;
869 set_value_address (function, pc);
871 /* STT_GNU_IFUNC resolver functions usually receive the HWCAP vector as
872 parameter. FUNCTION is the function entry address. ADDRESS may be a
873 function descriptor. */
875 target_auxv_search (¤t_target, AT_HWCAP, &hwcap);
876 hwcap_val = value_from_longest (builtin_type (gdbarch)
877 ->builtin_unsigned_long, hwcap);
878 address_val = call_function_by_hand (function, NULL, 1, &hwcap_val);
879 address = value_as_address (address_val);
880 address = gdbarch_convert_from_func_ptr_addr (gdbarch, address,
882 address = gdbarch_addr_bits_remove (gdbarch, address);
885 elf_gnu_ifunc_record_cache (name_at_pc, address);
890 /* Handle inferior hit of bp_gnu_ifunc_resolver, see its definition. */
893 elf_gnu_ifunc_resolver_stop (struct breakpoint *b)
895 struct breakpoint *b_return;
896 struct frame_info *prev_frame = get_prev_frame (get_current_frame ());
897 struct frame_id prev_frame_id = get_stack_frame_id (prev_frame);
898 CORE_ADDR prev_pc = get_frame_pc (prev_frame);
899 int thread_id = ptid_to_global_thread_id (inferior_ptid);
901 gdb_assert (b->type == bp_gnu_ifunc_resolver);
903 for (b_return = b->related_breakpoint; b_return != b;
904 b_return = b_return->related_breakpoint)
906 gdb_assert (b_return->type == bp_gnu_ifunc_resolver_return);
907 gdb_assert (b_return->loc != NULL && b_return->loc->next == NULL);
908 gdb_assert (frame_id_p (b_return->frame_id));
910 if (b_return->thread == thread_id
911 && b_return->loc->requested_address == prev_pc
912 && frame_id_eq (b_return->frame_id, prev_frame_id))
918 /* No need to call find_pc_line for symbols resolving as this is only
919 a helper breakpointer never shown to the user. */
922 sal.pspace = current_inferior ()->pspace;
924 sal.section = find_pc_overlay (sal.pc);
927 = set_momentary_breakpoint (get_frame_arch (prev_frame), sal,
929 bp_gnu_ifunc_resolver_return).release ();
931 /* set_momentary_breakpoint invalidates PREV_FRAME. */
934 /* Add new b_return to the ring list b->related_breakpoint. */
935 gdb_assert (b_return->related_breakpoint == b_return);
936 b_return->related_breakpoint = b->related_breakpoint;
937 b->related_breakpoint = b_return;
941 /* Handle inferior hit of bp_gnu_ifunc_resolver_return, see its definition. */
944 elf_gnu_ifunc_resolver_return_stop (struct breakpoint *b)
946 struct gdbarch *gdbarch = get_frame_arch (get_current_frame ());
947 struct type *func_func_type = builtin_type (gdbarch)->builtin_func_func;
948 struct type *value_type = TYPE_TARGET_TYPE (func_func_type);
949 struct regcache *regcache = get_thread_regcache (inferior_ptid);
950 struct value *func_func;
952 CORE_ADDR resolved_address, resolved_pc;
954 gdb_assert (b->type == bp_gnu_ifunc_resolver_return);
956 while (b->related_breakpoint != b)
958 struct breakpoint *b_next = b->related_breakpoint;
962 case bp_gnu_ifunc_resolver:
964 case bp_gnu_ifunc_resolver_return:
965 delete_breakpoint (b);
968 internal_error (__FILE__, __LINE__,
969 _("handle_inferior_event: Invalid "
970 "gnu-indirect-function breakpoint type %d"),
975 gdb_assert (b->type == bp_gnu_ifunc_resolver);
976 gdb_assert (b->loc->next == NULL);
978 func_func = allocate_value (func_func_type);
979 VALUE_LVAL (func_func) = lval_memory;
980 set_value_address (func_func, b->loc->related_address);
982 value = allocate_value (value_type);
983 gdbarch_return_value (gdbarch, func_func, value_type, regcache,
984 value_contents_raw (value), NULL);
985 resolved_address = value_as_address (value);
986 resolved_pc = gdbarch_convert_from_func_ptr_addr (gdbarch,
989 resolved_pc = gdbarch_addr_bits_remove (gdbarch, resolved_pc);
991 gdb_assert (current_program_space == b->pspace || b->pspace == NULL);
992 elf_gnu_ifunc_record_cache (event_location_to_string (b->location.get ()),
995 b->type = bp_breakpoint;
996 update_breakpoint_locations (b, current_program_space,
997 find_pc_line (resolved_pc, 0), {});
1000 /* A helper function for elf_symfile_read that reads the minimal
1004 elf_read_minimal_symbols (struct objfile *objfile, int symfile_flags,
1005 const struct elfinfo *ei)
1007 bfd *synth_abfd, *abfd = objfile->obfd;
1008 long symcount = 0, dynsymcount = 0, synthcount, storage_needed;
1009 asymbol **symbol_table = NULL, **dyn_symbol_table = NULL;
1011 struct dbx_symfile_info *dbx;
1013 if (symtab_create_debug)
1015 fprintf_unfiltered (gdb_stdlog,
1016 "Reading minimal symbols of objfile %s ...\n",
1017 objfile_name (objfile));
1020 /* If we already have minsyms, then we can skip some work here.
1021 However, if there were stabs or mdebug sections, we go ahead and
1022 redo all the work anyway, because the psym readers for those
1023 kinds of debuginfo need extra information found here. This can
1024 go away once all types of symbols are in the per-BFD object. */
1025 if (objfile->per_bfd->minsyms_read
1026 && ei->stabsect == NULL
1027 && ei->mdebugsect == NULL)
1029 if (symtab_create_debug)
1030 fprintf_unfiltered (gdb_stdlog,
1031 "... minimal symbols previously read\n");
1035 minimal_symbol_reader reader (objfile);
1037 /* Allocate struct to keep track of the symfile. */
1038 dbx = XCNEW (struct dbx_symfile_info);
1039 set_objfile_data (objfile, dbx_objfile_data_key, dbx);
1041 /* Process the normal ELF symbol table first. */
1043 storage_needed = bfd_get_symtab_upper_bound (objfile->obfd);
1044 if (storage_needed < 0)
1045 error (_("Can't read symbols from %s: %s"),
1046 bfd_get_filename (objfile->obfd),
1047 bfd_errmsg (bfd_get_error ()));
1049 if (storage_needed > 0)
1051 /* Memory gets permanently referenced from ABFD after
1052 bfd_canonicalize_symtab so it must not get freed before ABFD gets. */
1054 symbol_table = (asymbol **) bfd_alloc (abfd, storage_needed);
1055 symcount = bfd_canonicalize_symtab (objfile->obfd, symbol_table);
1058 error (_("Can't read symbols from %s: %s"),
1059 bfd_get_filename (objfile->obfd),
1060 bfd_errmsg (bfd_get_error ()));
1062 elf_symtab_read (reader, objfile, ST_REGULAR, symcount, symbol_table,
1066 /* Add the dynamic symbols. */
1068 storage_needed = bfd_get_dynamic_symtab_upper_bound (objfile->obfd);
1070 if (storage_needed > 0)
1072 /* Memory gets permanently referenced from ABFD after
1073 bfd_get_synthetic_symtab so it must not get freed before ABFD gets.
1074 It happens only in the case when elf_slurp_reloc_table sees
1075 asection->relocation NULL. Determining which section is asection is
1076 done by _bfd_elf_get_synthetic_symtab which is all a bfd
1077 implementation detail, though. */
1079 dyn_symbol_table = (asymbol **) bfd_alloc (abfd, storage_needed);
1080 dynsymcount = bfd_canonicalize_dynamic_symtab (objfile->obfd,
1083 if (dynsymcount < 0)
1084 error (_("Can't read symbols from %s: %s"),
1085 bfd_get_filename (objfile->obfd),
1086 bfd_errmsg (bfd_get_error ()));
1088 elf_symtab_read (reader, objfile, ST_DYNAMIC, dynsymcount,
1089 dyn_symbol_table, false);
1091 elf_rel_plt_read (reader, objfile, dyn_symbol_table);
1094 /* Contrary to binutils --strip-debug/--only-keep-debug the strip command from
1095 elfutils (eu-strip) moves even the .symtab section into the .debug file.
1097 bfd_get_synthetic_symtab on ppc64 for each function descriptor ELF symbol
1098 'name' creates a new BSF_SYNTHETIC ELF symbol '.name' with its code
1099 address. But with eu-strip files bfd_get_synthetic_symtab would fail to
1100 read the code address from .opd while it reads the .symtab section from
1101 a separate debug info file as the .opd section is SHT_NOBITS there.
1103 With SYNTH_ABFD the .opd section will be read from the original
1104 backlinked binary where it is valid. */
1106 if (objfile->separate_debug_objfile_backlink)
1107 synth_abfd = objfile->separate_debug_objfile_backlink->obfd;
1111 /* Add synthetic symbols - for instance, names for any PLT entries. */
1113 synthcount = bfd_get_synthetic_symtab (synth_abfd, symcount, symbol_table,
1114 dynsymcount, dyn_symbol_table,
1120 std::unique_ptr<asymbol *[]>
1121 synth_symbol_table (new asymbol *[synthcount]);
1122 for (i = 0; i < synthcount; i++)
1123 synth_symbol_table[i] = synthsyms + i;
1124 elf_symtab_read (reader, objfile, ST_SYNTHETIC, synthcount,
1125 synth_symbol_table.get (), true);
1131 /* Install any minimal symbols that have been collected as the current
1132 minimal symbols for this objfile. The debug readers below this point
1133 should not generate new minimal symbols; if they do it's their
1134 responsibility to install them. "mdebug" appears to be the only one
1135 which will do this. */
1139 if (symtab_create_debug)
1140 fprintf_unfiltered (gdb_stdlog, "Done reading minimal symbols.\n");
1143 /* Scan and build partial symbols for a symbol file.
1144 We have been initialized by a call to elf_symfile_init, which
1145 currently does nothing.
1147 This function only does the minimum work necessary for letting the
1148 user "name" things symbolically; it does not read the entire symtab.
1149 Instead, it reads the external and static symbols and puts them in partial
1150 symbol tables. When more extensive information is requested of a
1151 file, the corresponding partial symbol table is mutated into a full
1152 fledged symbol table by going back and reading the symbols
1155 We look for sections with specific names, to tell us what debug
1156 format to look for: FIXME!!!
1158 elfstab_build_psymtabs() handles STABS symbols;
1159 mdebug_build_psymtabs() handles ECOFF debugging information.
1161 Note that ELF files have a "minimal" symbol table, which looks a lot
1162 like a COFF symbol table, but has only the minimal information necessary
1163 for linking. We process this also, and use the information to
1164 build gdb's minimal symbol table. This gives us some minimal debugging
1165 capability even for files compiled without -g. */
1168 elf_symfile_read (struct objfile *objfile, symfile_add_flags symfile_flags)
1170 bfd *abfd = objfile->obfd;
1173 memset ((char *) &ei, 0, sizeof (ei));
1174 if (!(objfile->flags & OBJF_READNEVER))
1175 bfd_map_over_sections (abfd, elf_locate_sections, (void *) & ei);
1177 elf_read_minimal_symbols (objfile, symfile_flags, &ei);
1179 /* ELF debugging information is inserted into the psymtab in the
1180 order of least informative first - most informative last. Since
1181 the psymtab table is searched `most recent insertion first' this
1182 increases the probability that more detailed debug information
1183 for a section is found.
1185 For instance, an object file might contain both .mdebug (XCOFF)
1186 and .debug_info (DWARF2) sections then .mdebug is inserted first
1187 (searched last) and DWARF2 is inserted last (searched first). If
1188 we don't do this then the XCOFF info is found first - for code in
1189 an included file XCOFF info is useless. */
1193 const struct ecoff_debug_swap *swap;
1195 /* .mdebug section, presumably holding ECOFF debugging
1197 swap = get_elf_backend_data (abfd)->elf_backend_ecoff_debug_swap;
1199 elfmdebug_build_psymtabs (objfile, swap, ei.mdebugsect);
1205 /* Stab sections have an associated string table that looks like
1206 a separate section. */
1207 str_sect = bfd_get_section_by_name (abfd, ".stabstr");
1209 /* FIXME should probably warn about a stab section without a stabstr. */
1211 elfstab_build_psymtabs (objfile,
1214 bfd_section_size (abfd, str_sect));
1217 if (dwarf2_has_info (objfile, NULL))
1219 dw_index_kind index_kind;
1221 /* elf_sym_fns_gdb_index cannot handle simultaneous non-DWARF
1222 debug information present in OBJFILE. If there is such debug
1223 info present never use an index. */
1224 if (!objfile_has_partial_symbols (objfile)
1225 && dwarf2_initialize_objfile (objfile, &index_kind))
1229 case dw_index_kind::GDB_INDEX:
1230 objfile_set_sym_fns (objfile, &elf_sym_fns_gdb_index);
1232 case dw_index_kind::DEBUG_NAMES:
1233 objfile_set_sym_fns (objfile, &elf_sym_fns_debug_names);
1239 /* It is ok to do this even if the stabs reader made some
1240 partial symbols, because OBJF_PSYMTABS_READ has not been
1241 set, and so our lazy reader function will still be called
1243 objfile_set_sym_fns (objfile, &elf_sym_fns_lazy_psyms);
1246 /* If the file has its own symbol tables it has no separate debug
1247 info. `.dynsym'/`.symtab' go to MSYMBOLS, `.debug_info' goes to
1248 SYMTABS/PSYMTABS. `.gnu_debuglink' may no longer be present with
1249 `.note.gnu.build-id'.
1251 .gnu_debugdata is !objfile_has_partial_symbols because it contains only
1252 .symtab, not .debug_* section. But if we already added .gnu_debugdata as
1253 an objfile via find_separate_debug_file_in_section there was no separate
1254 debug info available. Therefore do not attempt to search for another one,
1255 objfile->separate_debug_objfile->separate_debug_objfile GDB guarantees to
1256 be NULL and we would possibly violate it. */
1258 else if (!objfile_has_partial_symbols (objfile)
1259 && objfile->separate_debug_objfile == NULL
1260 && objfile->separate_debug_objfile_backlink == NULL)
1262 std::string debugfile = find_separate_debug_file_by_buildid (objfile);
1264 if (debugfile.empty ())
1265 debugfile = find_separate_debug_file_by_debuglink (objfile);
1267 if (!debugfile.empty ())
1269 gdb_bfd_ref_ptr abfd (symfile_bfd_open (debugfile.c_str ()));
1271 symbol_file_add_separate (abfd.get (), debugfile.c_str (),
1272 symfile_flags, objfile);
1277 /* Callback to lazily read psymtabs. */
1280 read_psyms (struct objfile *objfile)
1282 if (dwarf2_has_info (objfile, NULL))
1283 dwarf2_build_psymtabs (objfile);
1286 /* Initialize anything that needs initializing when a completely new symbol
1287 file is specified (not just adding some symbols from another file, e.g. a
1290 We reinitialize buildsym, since we may be reading stabs from an ELF
1294 elf_new_init (struct objfile *ignore)
1296 stabsread_new_init ();
1297 buildsym_new_init ();
1300 /* Perform any local cleanups required when we are done with a particular
1301 objfile. I.E, we are in the process of discarding all symbol information
1302 for an objfile, freeing up all memory held for it, and unlinking the
1303 objfile struct from the global list of known objfiles. */
1306 elf_symfile_finish (struct objfile *objfile)
1308 dwarf2_free_objfile (objfile);
1311 /* ELF specific initialization routine for reading symbols. */
1314 elf_symfile_init (struct objfile *objfile)
1316 /* ELF objects may be reordered, so set OBJF_REORDERED. If we
1317 find this causes a significant slowdown in gdb then we could
1318 set it in the debug symbol readers only when necessary. */
1319 objfile->flags |= OBJF_REORDERED;
1322 /* Implementation of `sym_get_probes', as documented in symfile.h. */
1324 static const std::vector<probe *> &
1325 elf_get_probes (struct objfile *objfile)
1327 std::vector<probe *> *probes_per_bfd;
1329 /* Have we parsed this objfile's probes already? */
1330 probes_per_bfd = (std::vector<probe *> *) bfd_data (objfile->obfd, probe_key);
1332 if (probes_per_bfd == NULL)
1334 probes_per_bfd = new std::vector<probe *>;
1336 /* Here we try to gather information about all types of probes from the
1338 for (const static_probe_ops *ops : all_static_probe_ops)
1339 ops->get_probes (probes_per_bfd, objfile);
1341 set_bfd_data (objfile->obfd, probe_key, probes_per_bfd);
1344 return *probes_per_bfd;
1347 /* Helper function used to free the space allocated for storing SystemTap
1348 probe information. */
1351 probe_key_free (bfd *abfd, void *d)
1353 std::vector<probe *> *probes = (std::vector<probe *> *) d;
1355 for (probe *p : *probes)
1363 /* Implementation `sym_probe_fns', as documented in symfile.h. */
1365 static const struct sym_probe_fns elf_probe_fns =
1367 elf_get_probes, /* sym_get_probes */
1370 /* Register that we are able to handle ELF object file formats. */
1372 static const struct sym_fns elf_sym_fns =
1374 elf_new_init, /* init anything gbl to entire symtab */
1375 elf_symfile_init, /* read initial info, setup for sym_read() */
1376 elf_symfile_read, /* read a symbol file into symtab */
1377 NULL, /* sym_read_psymbols */
1378 elf_symfile_finish, /* finished with file, cleanup */
1379 default_symfile_offsets, /* Translate ext. to int. relocation */
1380 elf_symfile_segments, /* Get segment information from a file. */
1382 default_symfile_relocate, /* Relocate a debug section. */
1383 &elf_probe_fns, /* sym_probe_fns */
1387 /* The same as elf_sym_fns, but not registered and lazily reads
1390 const struct sym_fns elf_sym_fns_lazy_psyms =
1392 elf_new_init, /* init anything gbl to entire symtab */
1393 elf_symfile_init, /* read initial info, setup for sym_read() */
1394 elf_symfile_read, /* read a symbol file into symtab */
1395 read_psyms, /* sym_read_psymbols */
1396 elf_symfile_finish, /* finished with file, cleanup */
1397 default_symfile_offsets, /* Translate ext. to int. relocation */
1398 elf_symfile_segments, /* Get segment information from a file. */
1400 default_symfile_relocate, /* Relocate a debug section. */
1401 &elf_probe_fns, /* sym_probe_fns */
1405 /* The same as elf_sym_fns, but not registered and uses the
1406 DWARF-specific GNU index rather than psymtab. */
1407 const struct sym_fns elf_sym_fns_gdb_index =
1409 elf_new_init, /* init anything gbl to entire symab */
1410 elf_symfile_init, /* read initial info, setup for sym_red() */
1411 elf_symfile_read, /* read a symbol file into symtab */
1412 NULL, /* sym_read_psymbols */
1413 elf_symfile_finish, /* finished with file, cleanup */
1414 default_symfile_offsets, /* Translate ext. to int. relocatin */
1415 elf_symfile_segments, /* Get segment information from a file. */
1417 default_symfile_relocate, /* Relocate a debug section. */
1418 &elf_probe_fns, /* sym_probe_fns */
1419 &dwarf2_gdb_index_functions
1422 /* The same as elf_sym_fns, but not registered and uses the
1423 DWARF-specific .debug_names index rather than psymtab. */
1424 const struct sym_fns elf_sym_fns_debug_names =
1426 elf_new_init, /* init anything gbl to entire symab */
1427 elf_symfile_init, /* read initial info, setup for sym_red() */
1428 elf_symfile_read, /* read a symbol file into symtab */
1429 NULL, /* sym_read_psymbols */
1430 elf_symfile_finish, /* finished with file, cleanup */
1431 default_symfile_offsets, /* Translate ext. to int. relocatin */
1432 elf_symfile_segments, /* Get segment information from a file. */
1434 default_symfile_relocate, /* Relocate a debug section. */
1435 &elf_probe_fns, /* sym_probe_fns */
1436 &dwarf2_debug_names_functions
1439 /* STT_GNU_IFUNC resolver vector to be installed to gnu_ifunc_fns_p. */
1441 static const struct gnu_ifunc_fns elf_gnu_ifunc_fns =
1443 elf_gnu_ifunc_resolve_addr,
1444 elf_gnu_ifunc_resolve_name,
1445 elf_gnu_ifunc_resolver_stop,
1446 elf_gnu_ifunc_resolver_return_stop
1450 _initialize_elfread (void)
1452 probe_key = register_bfd_data_with_cleanup (NULL, probe_key_free);
1453 add_symtab_fns (bfd_target_elf_flavour, &elf_sym_fns);
1455 elf_objfile_gnu_ifunc_cache_data = register_objfile_data ();
1456 gnu_ifunc_fns_p = &elf_gnu_ifunc_fns;