1 /* Read ELF (Executable and Linking Format) object files for GDB.
3 Copyright (C) 1991-2024 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"
33 #include "filenames.h"
35 #include "arch-utils.h"
39 #include "gdbthread.h"
46 #include "mdebugread.h"
48 #include <string_view>
49 #include "gdbsupport/scoped_fd.h"
50 #include "dwarf2/public.h"
51 #include "cli/cli-cmds.h"
53 /* Whether ctf should always be read, or only if no dwarf is present. */
54 static bool always_read_ctf
;
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 */
64 asection
*ctfsect
; /* Section pointer for .ctf section */
67 /* Type for per-BFD data. */
69 typedef std::vector
<std::unique_ptr
<probe
>> elfread_data
;
71 /* Per-BFD data for probe info. */
73 static const registry
<bfd
>::key
<elfread_data
> probe_key
;
75 /* Minimal symbols located at the GOT entries for .plt - that is the real
76 pointer where the given entry will jump to. It gets updated by the real
77 function address during lazy ld.so resolving in the inferior. These
78 minimal symbols are indexed for <tab>-completion. */
80 #define SYMBOL_GOT_PLT_SUFFIX "@got.plt"
82 /* Locate the segments in ABFD. */
84 static symfile_segment_data_up
85 elf_symfile_segments (bfd
*abfd
)
87 Elf_Internal_Phdr
*phdrs
, **segments
;
89 int num_phdrs
, num_segments
, num_sections
, i
;
92 phdrs_size
= bfd_get_elf_phdr_upper_bound (abfd
);
96 phdrs
= (Elf_Internal_Phdr
*) alloca (phdrs_size
);
97 num_phdrs
= bfd_get_elf_phdrs (abfd
, phdrs
);
102 segments
= XALLOCAVEC (Elf_Internal_Phdr
*, num_phdrs
);
103 for (i
= 0; i
< num_phdrs
; i
++)
104 if (phdrs
[i
].p_type
== PT_LOAD
)
105 segments
[num_segments
++] = &phdrs
[i
];
107 if (num_segments
== 0)
110 symfile_segment_data_up
data (new symfile_segment_data
);
111 data
->segments
.reserve (num_segments
);
113 for (i
= 0; i
< num_segments
; i
++)
114 data
->segments
.emplace_back (segments
[i
]->p_vaddr
, segments
[i
]->p_memsz
);
116 num_sections
= bfd_count_sections (abfd
);
118 /* All elements are initialized to 0 (map to no segment). */
119 data
->segment_info
.resize (num_sections
);
121 for (i
= 0, sect
= abfd
->sections
; sect
!= NULL
; i
++, sect
= sect
->next
)
125 if ((bfd_section_flags (sect
) & SEC_ALLOC
) == 0)
128 Elf_Internal_Shdr
*this_hdr
= &elf_section_data (sect
)->this_hdr
;
130 for (j
= 0; j
< num_segments
; j
++)
131 if (ELF_SECTION_IN_SEGMENT (this_hdr
, segments
[j
]))
133 data
->segment_info
[i
] = j
+ 1;
137 /* We should have found a segment for every non-empty section.
138 If we haven't, we will not relocate this section by any
139 offsets we apply to the segments. As an exception, do not
140 warn about SHT_NOBITS sections; in normal ELF execution
141 environments, SHT_NOBITS means zero-initialized and belongs
142 in a segment, but in no-OS environments some tools (e.g. ARM
143 RealView) use SHT_NOBITS for uninitialized data. Since it is
144 uninitialized, it doesn't need a program header. Such
145 binaries are not relocatable. */
147 /* Exclude debuginfo files from this warning, too, since those
148 are often not strictly compliant with the standard. See, e.g.,
149 ld/24717 for more discussion. */
150 if (!is_debuginfo_file (abfd
)
151 && bfd_section_size (sect
) > 0 && j
== num_segments
152 && (bfd_section_flags (sect
) & SEC_LOAD
) != 0)
153 warning (_("Loadable section \"%s\" outside of ELF segments\n in %s"),
154 bfd_section_name (sect
), bfd_get_filename (abfd
));
160 /* We are called once per section from elf_symfile_read. We
161 need to examine each section we are passed, check to see
162 if it is something we are interested in processing, and
163 if so, stash away some access information for the section.
165 For now we recognize the dwarf debug information sections and
166 line number sections from matching their section names. The
167 ELF definition is no real help here since it has no direct
168 knowledge of DWARF (by design, so any debugging format can be
171 We also recognize the ".stab" sections used by the Sun compilers
172 released with Solaris 2.
174 FIXME: The section names should not be hardwired strings (what
175 should they be? I don't think most object file formats have enough
176 section flags to specify what kind of debug section it is.
180 elf_locate_sections (asection
*sectp
, struct elfinfo
*ei
)
182 if (strcmp (sectp
->name
, ".stab") == 0)
184 ei
->stabsect
= sectp
;
186 else if (strcmp (sectp
->name
, ".mdebug") == 0)
188 ei
->mdebugsect
= sectp
;
190 else if (strcmp (sectp
->name
, ".ctf") == 0)
196 static struct minimal_symbol
*
197 record_minimal_symbol (minimal_symbol_reader
&reader
,
198 std::string_view name
, bool copy_name
,
199 unrelocated_addr address
,
200 enum minimal_symbol_type ms_type
,
201 asection
*bfd_section
, struct objfile
*objfile
)
203 struct gdbarch
*gdbarch
= objfile
->arch ();
205 if (ms_type
== mst_text
|| ms_type
== mst_file_text
206 || ms_type
== mst_text_gnu_ifunc
)
208 = unrelocated_addr (gdbarch_addr_bits_remove (gdbarch
,
209 CORE_ADDR (address
)));
211 /* We only setup section information for allocatable sections. Usually
212 we'd only expect to find msymbols for allocatable sections, but if the
213 ELF is malformed then this might not be the case. In that case don't
214 create an msymbol that references an uninitialised section object. */
215 int section_index
= 0;
216 if ((bfd_section_flags (bfd_section
) & SEC_ALLOC
) == SEC_ALLOC
217 || bfd_section
== bfd_abs_section_ptr
)
218 section_index
= gdb_bfd_section_index (objfile
->obfd
.get (), bfd_section
);
220 return reader
.record_full (name
, copy_name
, address
, ms_type
, section_index
);
223 /* Read the symbol table of an ELF file.
225 Given an objfile, a symbol table, and a flag indicating whether the
226 symbol table contains regular, dynamic, or synthetic symbols, add all
227 the global function and data symbols to the minimal symbol table.
229 In stabs-in-ELF, as implemented by Sun, there are some local symbols
230 defined in the ELF symbol table, which can be used to locate
231 the beginnings of sections from each ".o" file that was linked to
232 form the executable objfile. We gather any such info and record it
233 in data structures hung off the objfile's private data. */
237 #define ST_SYNTHETIC 2
240 elf_symtab_read (minimal_symbol_reader
&reader
,
241 struct objfile
*objfile
, int type
,
242 long number_of_symbols
, asymbol
**symbol_table
,
245 struct gdbarch
*gdbarch
= objfile
->arch ();
249 enum minimal_symbol_type ms_type
;
250 /* Name of the last file symbol. This is either a constant string or is
251 saved on the objfile's filename cache. */
252 const char *filesymname
= "";
253 int stripped
= (bfd_get_symcount (objfile
->obfd
.get ()) == 0);
254 int elf_make_msymbol_special_p
255 = gdbarch_elf_make_msymbol_special_p (gdbarch
);
257 for (i
= 0; i
< number_of_symbols
; i
++)
259 sym
= symbol_table
[i
];
260 if (sym
->name
== NULL
|| *sym
->name
== '\0')
262 /* Skip names that don't exist (shouldn't happen), or names
263 that are null strings (may happen). */
267 elf_symbol_type
*elf_sym
= (elf_symbol_type
*) sym
;
269 /* Skip "special" symbols, e.g. ARM mapping symbols. These are
270 symbols which do not correspond to objects in the symbol table,
271 but have some other target-specific meaning. */
272 if (bfd_is_target_special_symbol (objfile
->obfd
.get (), sym
))
274 if (gdbarch_record_special_symbol_p (gdbarch
))
275 gdbarch_record_special_symbol (gdbarch
, objfile
, sym
);
279 if (type
== ST_DYNAMIC
280 && sym
->section
== bfd_und_section_ptr
281 && (sym
->flags
& BSF_FUNCTION
))
283 struct minimal_symbol
*msym
;
284 bfd
*abfd
= objfile
->obfd
.get ();
287 /* Symbol is a reference to a function defined in
289 If its value is non zero then it is usually the address
290 of the corresponding entry in the procedure linkage table,
291 plus the desired section offset.
292 If its value is zero then the dynamic linker has to resolve
293 the symbol. We are unable to find any meaningful address
294 for this symbol in the executable file, so we skip it. */
295 symaddr
= sym
->value
;
299 /* sym->section is the undefined section. However, we want to
300 record the section where the PLT stub resides with the
301 minimal symbol. Search the section table for the one that
302 covers the stub's address. */
303 for (sect
= abfd
->sections
; sect
!= NULL
; sect
= sect
->next
)
305 if ((bfd_section_flags (sect
) & SEC_ALLOC
) == 0)
308 if (symaddr
>= bfd_section_vma (sect
)
309 && symaddr
< bfd_section_vma (sect
)
310 + bfd_section_size (sect
))
316 /* On ia64-hpux, we have discovered that the system linker
317 adds undefined symbols with nonzero addresses that cannot
318 be right (their address points inside the code of another
319 function in the .text section). This creates problems
320 when trying to determine which symbol corresponds to
323 We try to detect those buggy symbols by checking which
324 section we think they correspond to. Normally, PLT symbols
325 are stored inside their own section, and the typical name
326 for that section is ".plt". So, if there is a ".plt"
327 section, and yet the section name of our symbol does not
328 start with ".plt", we ignore that symbol. */
329 if (!startswith (sect
->name
, ".plt")
330 && bfd_get_section_by_name (abfd
, ".plt") != NULL
)
333 msym
= record_minimal_symbol
334 (reader
, sym
->name
, copy_names
,
335 unrelocated_addr (symaddr
),
336 mst_solib_trampoline
, sect
, objfile
);
339 msym
->filename
= filesymname
;
340 if (elf_make_msymbol_special_p
)
341 gdbarch_elf_make_msymbol_special (gdbarch
, sym
, msym
);
346 /* If it is a nonstripped executable, do not enter dynamic
347 symbols, as the dynamic symbol table is usually a subset
348 of the main symbol table. */
349 if (type
== ST_DYNAMIC
&& !stripped
)
351 if (sym
->flags
& BSF_FILE
)
352 filesymname
= objfile
->intern (sym
->name
);
353 else if (sym
->flags
& BSF_SECTION_SYM
)
355 else if (sym
->flags
& (BSF_GLOBAL
| BSF_LOCAL
| BSF_WEAK
358 struct minimal_symbol
*msym
;
360 /* Select global/local/weak symbols. Note that bfd puts abs
361 symbols in their own section, so all symbols we are
362 interested in will have a section. */
363 /* Bfd symbols are section relative. */
364 symaddr
= sym
->value
+ sym
->section
->vma
;
365 /* For non-absolute symbols, use the type of the section
366 they are relative to, to intuit text/data. Bfd provides
367 no way of figuring this out for absolute symbols. */
368 if (sym
->section
== bfd_abs_section_ptr
)
370 /* This is a hack to get the minimal symbol type
371 right for Irix 5, which has absolute addresses
372 with special section indices for dynamic symbols.
374 NOTE: uweigand-20071112: Synthetic symbols do not
375 have an ELF-private part, so do not touch those. */
376 unsigned int shndx
= type
== ST_SYNTHETIC
? 0 :
377 elf_sym
->internal_elf_sym
.st_shndx
;
387 case SHN_MIPS_ACOMMON
:
394 /* If it is an Irix dynamic symbol, skip section name
395 symbols, relocate all others by section offset. */
396 if (ms_type
!= mst_abs
)
398 if (sym
->name
[0] == '.')
402 else if (sym
->section
->flags
& SEC_CODE
)
404 if (sym
->flags
& (BSF_GLOBAL
| BSF_WEAK
| BSF_GNU_UNIQUE
))
406 if (sym
->flags
& BSF_GNU_INDIRECT_FUNCTION
)
407 ms_type
= mst_text_gnu_ifunc
;
411 /* The BSF_SYNTHETIC check is there to omit ppc64 function
412 descriptors mistaken for static functions starting with 'L'.
414 else if ((sym
->name
[0] == '.' && sym
->name
[1] == 'L'
415 && (sym
->flags
& BSF_SYNTHETIC
) == 0)
416 || ((sym
->flags
& BSF_LOCAL
)
417 && sym
->name
[0] == '$'
418 && sym
->name
[1] == 'L'))
419 /* Looks like a compiler-generated label. Skip
420 it. The assembler should be skipping these (to
421 keep executables small), but apparently with
422 gcc on the (deleted) delta m88k SVR4, it loses.
423 So to have us check too should be harmless (but
424 I encourage people to fix this in the assembler
425 instead of adding checks here). */
429 ms_type
= mst_file_text
;
432 else if (sym
->section
->flags
& SEC_ALLOC
)
434 if (sym
->flags
& (BSF_GLOBAL
| BSF_WEAK
| BSF_GNU_UNIQUE
))
436 if (sym
->flags
& BSF_GNU_INDIRECT_FUNCTION
)
438 ms_type
= mst_data_gnu_ifunc
;
440 else if (sym
->section
->flags
& SEC_LOAD
)
449 else if (sym
->flags
& BSF_LOCAL
)
451 if (sym
->section
->flags
& SEC_LOAD
)
453 ms_type
= mst_file_data
;
457 ms_type
= mst_file_bss
;
462 ms_type
= mst_unknown
;
467 /* FIXME: Solaris2 shared libraries include lots of
468 odd "absolute" and "undefined" symbols, that play
469 hob with actions like finding what function the PC
470 is in. Ignore them if they aren't text, data, or bss. */
471 /* ms_type = mst_unknown; */
472 continue; /* Skip this symbol. */
474 msym
= record_minimal_symbol
475 (reader
, sym
->name
, copy_names
, unrelocated_addr (symaddr
),
476 ms_type
, sym
->section
, objfile
);
480 /* NOTE: uweigand-20071112: A synthetic symbol does not have an
482 if (type
!= ST_SYNTHETIC
)
484 /* Pass symbol size field in via BFD. FIXME!!! */
485 msym
->set_size (elf_sym
->internal_elf_sym
.st_size
);
488 msym
->filename
= filesymname
;
489 if (elf_make_msymbol_special_p
)
490 gdbarch_elf_make_msymbol_special (gdbarch
, sym
, msym
);
493 /* If we see a default versioned symbol, install it under
494 its version-less name. */
497 const char *atsign
= strchr (sym
->name
, '@');
498 bool is_at_symbol
= atsign
!= nullptr && atsign
> sym
->name
;
499 bool is_plt
= is_at_symbol
&& strcmp (atsign
, "@plt") == 0;
500 int len
= is_at_symbol
? atsign
- sym
->name
: 0;
504 && (elf_sym
->version
& VERSYM_HIDDEN
) == 0)
505 record_minimal_symbol (reader
,
506 std::string_view (sym
->name
, len
),
507 true, unrelocated_addr (symaddr
),
508 ms_type
, sym
->section
, objfile
);
511 /* For @plt symbols, also record a trampoline to the
512 destination symbol. The @plt symbol will be used
513 in disassembly, and the trampoline will be used
514 when we are trying to find the target. */
515 if (ms_type
== mst_text
&& type
== ST_SYNTHETIC
)
517 struct minimal_symbol
*mtramp
;
519 mtramp
= record_minimal_symbol
520 (reader
, std::string_view (sym
->name
, len
), true,
521 unrelocated_addr (symaddr
),
522 mst_solib_trampoline
, sym
->section
, objfile
);
525 mtramp
->set_size (msym
->size());
526 mtramp
->created_by_gdb
= 1;
527 mtramp
->filename
= filesymname
;
528 if (elf_make_msymbol_special_p
)
529 gdbarch_elf_make_msymbol_special (gdbarch
,
539 /* Build minimal symbols named `function@got.plt' (see SYMBOL_GOT_PLT_SUFFIX)
540 for later look ups of which function to call when user requests
541 a STT_GNU_IFUNC function. As the STT_GNU_IFUNC type is found at the target
542 library defining `function' we cannot yet know while reading OBJFILE which
543 of the SYMBOL_GOT_PLT_SUFFIX entries will be needed and later
544 DYN_SYMBOL_TABLE is no longer easily available for OBJFILE. */
547 elf_rel_plt_read (minimal_symbol_reader
&reader
,
548 struct objfile
*objfile
, asymbol
**dyn_symbol_table
)
550 bfd
*obfd
= objfile
->obfd
.get ();
551 const struct elf_backend_data
*bed
= get_elf_backend_data (obfd
);
552 asection
*relplt
, *got_plt
;
553 bfd_size_type reloc_count
, reloc
;
554 struct gdbarch
*gdbarch
= objfile
->arch ();
555 struct type
*ptr_type
= builtin_type (gdbarch
)->builtin_data_ptr
;
556 size_t ptr_size
= ptr_type
->length ();
558 if (objfile
->separate_debug_objfile_backlink
)
561 got_plt
= bfd_get_section_by_name (obfd
, ".got.plt");
564 /* For platforms where there is no separate .got.plt. */
565 got_plt
= bfd_get_section_by_name (obfd
, ".got");
570 /* Depending on system, we may find jump slots in a relocation
571 section for either .got.plt or .plt. */
572 asection
*plt
= bfd_get_section_by_name (obfd
, ".plt");
573 int plt_elf_idx
= (plt
!= NULL
) ? elf_section_data (plt
)->this_idx
: -1;
575 int got_plt_elf_idx
= elf_section_data (got_plt
)->this_idx
;
577 /* This search algorithm is from _bfd_elf_canonicalize_dynamic_reloc. */
578 for (relplt
= obfd
->sections
; relplt
!= NULL
; relplt
= relplt
->next
)
580 const auto &this_hdr
= elf_section_data (relplt
)->this_hdr
;
582 if (this_hdr
.sh_type
== SHT_REL
|| this_hdr
.sh_type
== SHT_RELA
)
584 if (this_hdr
.sh_info
== plt_elf_idx
585 || this_hdr
.sh_info
== got_plt_elf_idx
)
592 if (! bed
->s
->slurp_reloc_table (obfd
, relplt
, dyn_symbol_table
, TRUE
))
595 std::string string_buffer
;
597 /* Does ADDRESS reside in SECTION of OBFD? */
598 auto within_section
= [obfd
] (asection
*section
, CORE_ADDR address
)
603 return (bfd_section_vma (section
) <= address
604 && (address
< bfd_section_vma (section
)
605 + bfd_section_size (section
)));
608 reloc_count
= relplt
->size
/ elf_section_data (relplt
)->this_hdr
.sh_entsize
;
609 for (reloc
= 0; reloc
< reloc_count
; reloc
++)
612 struct minimal_symbol
*msym
;
614 const char *got_suffix
= SYMBOL_GOT_PLT_SUFFIX
;
615 const size_t got_suffix_len
= strlen (SYMBOL_GOT_PLT_SUFFIX
);
617 name
= bfd_asymbol_name (*relplt
->relocation
[reloc
].sym_ptr_ptr
);
618 address
= relplt
->relocation
[reloc
].address
;
620 asection
*msym_section
;
622 /* Does the pointer reside in either the .got.plt or .plt
624 if (within_section (got_plt
, address
))
625 msym_section
= got_plt
;
626 else if (within_section (plt
, address
))
631 /* We cannot check if NAME is a reference to
632 mst_text_gnu_ifunc/mst_data_gnu_ifunc as in OBJFILE the
633 symbol is undefined and the objfile having NAME defined may
634 not yet have been loaded. */
636 string_buffer
.assign (name
);
637 string_buffer
.append (got_suffix
, got_suffix
+ got_suffix_len
);
639 msym
= record_minimal_symbol (reader
, string_buffer
,
640 true, unrelocated_addr (address
),
641 mst_slot_got_plt
, msym_section
, objfile
);
643 msym
->set_size (ptr_size
);
647 /* The data pointer is htab_t for gnu_ifunc_record_cache_unchecked. */
649 static const registry
<objfile
>::key
<htab
, htab_deleter
>
650 elf_objfile_gnu_ifunc_cache_data
;
652 /* Map function names to CORE_ADDR in elf_objfile_gnu_ifunc_cache_data. */
654 struct elf_gnu_ifunc_cache
656 /* This is always a function entry address, not a function descriptor. */
662 /* htab_hash for elf_objfile_gnu_ifunc_cache_data. */
665 elf_gnu_ifunc_cache_hash (const void *a_voidp
)
667 const struct elf_gnu_ifunc_cache
*a
668 = (const struct elf_gnu_ifunc_cache
*) a_voidp
;
670 return htab_hash_string (a
->name
);
673 /* htab_eq for elf_objfile_gnu_ifunc_cache_data. */
676 elf_gnu_ifunc_cache_eq (const void *a_voidp
, const void *b_voidp
)
678 const struct elf_gnu_ifunc_cache
*a
679 = (const struct elf_gnu_ifunc_cache
*) a_voidp
;
680 const struct elf_gnu_ifunc_cache
*b
681 = (const struct elf_gnu_ifunc_cache
*) b_voidp
;
683 return strcmp (a
->name
, b
->name
) == 0;
686 /* Record the target function address of a STT_GNU_IFUNC function NAME is the
687 function entry address ADDR. Return 1 if NAME and ADDR are considered as
688 valid and therefore they were successfully recorded, return 0 otherwise.
690 Function does not expect a duplicate entry. Use
691 elf_gnu_ifunc_resolve_by_cache first to check if the entry for NAME already
695 elf_gnu_ifunc_record_cache (const char *name
, CORE_ADDR addr
)
697 struct bound_minimal_symbol msym
;
698 struct objfile
*objfile
;
700 struct elf_gnu_ifunc_cache entry_local
, *entry_p
;
703 msym
= lookup_minimal_symbol_by_pc (addr
);
704 if (msym
.minsym
== NULL
)
706 if (msym
.value_address () != addr
)
708 objfile
= msym
.objfile
;
710 /* If .plt jumps back to .plt the symbol is still deferred for later
711 resolution and it has no use for GDB. */
712 const char *target_name
= msym
.minsym
->linkage_name ();
713 size_t len
= strlen (target_name
);
715 /* Note we check the symbol's name instead of checking whether the
716 symbol is in the .plt section because some systems have @plt
717 symbols in the .text section. */
718 if (len
> 4 && strcmp (target_name
+ len
- 4, "@plt") == 0)
721 if (strcmp (target_name
, "_PROCEDURE_LINKAGE_TABLE_") == 0)
724 htab
= elf_objfile_gnu_ifunc_cache_data
.get (objfile
);
727 htab
= htab_create_alloc (1, elf_gnu_ifunc_cache_hash
,
728 elf_gnu_ifunc_cache_eq
,
729 NULL
, xcalloc
, xfree
);
730 elf_objfile_gnu_ifunc_cache_data
.set (objfile
, htab
);
733 entry_local
.addr
= addr
;
734 obstack_grow (&objfile
->objfile_obstack
, &entry_local
,
735 offsetof (struct elf_gnu_ifunc_cache
, name
));
736 obstack_grow_str0 (&objfile
->objfile_obstack
, name
);
738 = (struct elf_gnu_ifunc_cache
*) obstack_finish (&objfile
->objfile_obstack
);
740 slot
= htab_find_slot (htab
, entry_p
, INSERT
);
743 struct elf_gnu_ifunc_cache
*entry_found_p
744 = (struct elf_gnu_ifunc_cache
*) *slot
;
745 struct gdbarch
*gdbarch
= objfile
->arch ();
747 if (entry_found_p
->addr
!= addr
)
749 /* This case indicates buggy inferior program, the resolved address
750 should never change. */
752 warning (_("gnu-indirect-function \"%s\" has changed its resolved "
753 "function_address from %s to %s"),
754 name
, paddress (gdbarch
, entry_found_p
->addr
),
755 paddress (gdbarch
, addr
));
758 /* New ENTRY_P is here leaked/duplicate in the OBJFILE obstack. */
765 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
766 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
767 is not NULL) and the function returns 1. It returns 0 otherwise.
769 Only the elf_objfile_gnu_ifunc_cache_data hash table is searched by this
773 elf_gnu_ifunc_resolve_by_cache (const char *name
, CORE_ADDR
*addr_p
)
777 /* FIXME: we only search the initial namespace.
779 To search other namespaces, we would need to provide context, e.g. in
780 form of an objfile in that namespace. */
781 gdbarch_iterate_over_objfiles_in_search_order
782 (current_inferior ()->arch (),
783 [name
, &addr_p
, &found
] (struct objfile
*objfile
)
786 elf_gnu_ifunc_cache
*entry_p
;
789 htab
= elf_objfile_gnu_ifunc_cache_data
.get (objfile
);
793 entry_p
= ((elf_gnu_ifunc_cache
*)
794 alloca (sizeof (*entry_p
) + strlen (name
)));
795 strcpy (entry_p
->name
, name
);
797 slot
= htab_find_slot (htab
, entry_p
, NO_INSERT
);
800 entry_p
= (elf_gnu_ifunc_cache
*) *slot
;
801 gdb_assert (entry_p
!= NULL
);
804 *addr_p
= entry_p
->addr
;
813 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
814 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
815 is not NULL) and the function returns 1. It returns 0 otherwise.
817 Only the SYMBOL_GOT_PLT_SUFFIX locations are searched by this function.
818 elf_gnu_ifunc_resolve_by_cache must have been already called for NAME to
819 prevent cache entries duplicates. */
822 elf_gnu_ifunc_resolve_by_got (const char *name
, CORE_ADDR
*addr_p
)
825 const size_t got_suffix_len
= strlen (SYMBOL_GOT_PLT_SUFFIX
);
828 name_got_plt
= (char *) alloca (strlen (name
) + got_suffix_len
+ 1);
829 sprintf (name_got_plt
, "%s" SYMBOL_GOT_PLT_SUFFIX
, name
);
831 /* FIXME: we only search the initial namespace.
833 To search other namespaces, we would need to provide context, e.g. in
834 form of an objfile in that namespace. */
835 gdbarch_iterate_over_objfiles_in_search_order
836 (current_inferior ()->arch (),
837 [name
, name_got_plt
, &addr_p
, &found
] (struct objfile
*objfile
)
839 bfd
*obfd
= objfile
->obfd
.get ();
840 struct gdbarch
*gdbarch
= objfile
->arch ();
841 type
*ptr_type
= builtin_type (gdbarch
)->builtin_data_ptr
;
842 size_t ptr_size
= ptr_type
->length ();
843 CORE_ADDR pointer_address
, addr
;
845 gdb_byte
*buf
= (gdb_byte
*) alloca (ptr_size
);
846 bound_minimal_symbol msym
;
848 msym
= lookup_minimal_symbol (name_got_plt
, NULL
, objfile
);
849 if (msym
.minsym
== NULL
)
851 if (msym
.minsym
->type () != mst_slot_got_plt
)
853 pointer_address
= msym
.value_address ();
855 plt
= bfd_get_section_by_name (obfd
, ".plt");
859 if (msym
.minsym
->size () != ptr_size
)
861 if (target_read_memory (pointer_address
, buf
, ptr_size
) != 0)
863 addr
= extract_typed_address (buf
, ptr_type
);
864 addr
= gdbarch_convert_from_func_ptr_addr
865 (gdbarch
, addr
, current_inferior ()->top_target ());
866 addr
= gdbarch_addr_bits_remove (gdbarch
, addr
);
868 if (elf_gnu_ifunc_record_cache (name
, addr
))
883 /* Try to find the target resolved function entry address of a STT_GNU_IFUNC
884 function NAME. If the address is found it is stored to *ADDR_P (if ADDR_P
885 is not NULL) and the function returns true. It returns false otherwise.
887 Both the elf_objfile_gnu_ifunc_cache_data hash table and
888 SYMBOL_GOT_PLT_SUFFIX locations are searched by this function. */
891 elf_gnu_ifunc_resolve_name (const char *name
, CORE_ADDR
*addr_p
)
893 if (elf_gnu_ifunc_resolve_by_cache (name
, addr_p
))
896 if (elf_gnu_ifunc_resolve_by_got (name
, addr_p
))
902 /* Call STT_GNU_IFUNC - a function returning addresss of a real function to
903 call. PC is theSTT_GNU_IFUNC resolving function entry. The value returned
904 is the entry point of the resolved STT_GNU_IFUNC target function to call.
908 elf_gnu_ifunc_resolve_addr (struct gdbarch
*gdbarch
, CORE_ADDR pc
)
910 const char *name_at_pc
;
911 CORE_ADDR start_at_pc
, address
;
912 struct type
*func_func_type
= builtin_type (gdbarch
)->builtin_func_func
;
913 struct value
*function
, *address_val
;
915 struct value
*hwcap_val
;
917 /* Try first any non-intrusive methods without an inferior call. */
919 if (find_pc_partial_function (pc
, &name_at_pc
, &start_at_pc
, NULL
)
920 && start_at_pc
== pc
)
922 if (elf_gnu_ifunc_resolve_name (name_at_pc
, &address
))
928 function
= value::allocate (func_func_type
);
929 function
->set_lval (lval_memory
);
930 function
->set_address (pc
);
932 /* STT_GNU_IFUNC resolver functions usually receive the HWCAP vector as
933 parameter. FUNCTION is the function entry address. ADDRESS may be a
934 function descriptor. */
936 target_auxv_search (AT_HWCAP
, &hwcap
);
937 hwcap_val
= value_from_longest (builtin_type (gdbarch
)
938 ->builtin_unsigned_long
, hwcap
);
939 address_val
= call_function_by_hand (function
, NULL
, hwcap_val
);
940 address
= value_as_address (address_val
);
941 address
= gdbarch_convert_from_func_ptr_addr
942 (gdbarch
, address
, current_inferior ()->top_target ());
943 address
= gdbarch_addr_bits_remove (gdbarch
, address
);
946 elf_gnu_ifunc_record_cache (name_at_pc
, address
);
951 /* Handle inferior hit of bp_gnu_ifunc_resolver, see its definition. */
954 elf_gnu_ifunc_resolver_stop (code_breakpoint
*b
)
956 struct breakpoint
*b_return
;
957 frame_info_ptr prev_frame
= get_prev_frame (get_current_frame ());
958 struct frame_id prev_frame_id
= get_stack_frame_id (prev_frame
);
959 CORE_ADDR prev_pc
= get_frame_pc (prev_frame
);
960 int thread_id
= inferior_thread ()->global_num
;
962 gdb_assert (b
->type
== bp_gnu_ifunc_resolver
);
964 for (b_return
= b
->related_breakpoint
; b_return
!= b
;
965 b_return
= b_return
->related_breakpoint
)
967 gdb_assert (b_return
->type
== bp_gnu_ifunc_resolver_return
);
968 gdb_assert (b_return
->has_single_location ());
969 gdb_assert (frame_id_p (b_return
->frame_id
));
971 if (b_return
->thread
== thread_id
972 && b_return
->first_loc ().requested_address
== prev_pc
973 && b_return
->frame_id
== prev_frame_id
)
979 /* No need to call find_pc_line for symbols resolving as this is only
980 a helper breakpointer never shown to the user. */
983 sal
.pspace
= current_inferior ()->pspace
;
985 sal
.section
= find_pc_overlay (sal
.pc
);
988 = set_momentary_breakpoint (get_frame_arch (prev_frame
), sal
,
990 bp_gnu_ifunc_resolver_return
).release ();
993 /* Add new b_return to the ring list b->related_breakpoint. */
994 gdb_assert (b_return
->related_breakpoint
== b_return
);
995 b_return
->related_breakpoint
= b
->related_breakpoint
;
996 b
->related_breakpoint
= b_return
;
1000 /* Handle inferior hit of bp_gnu_ifunc_resolver_return, see its definition. */
1003 elf_gnu_ifunc_resolver_return_stop (code_breakpoint
*b
)
1005 thread_info
*thread
= inferior_thread ();
1006 struct gdbarch
*gdbarch
= get_frame_arch (get_current_frame ());
1007 struct type
*func_func_type
= builtin_type (gdbarch
)->builtin_func_func
;
1008 struct type
*value_type
= func_func_type
->target_type ();
1009 struct regcache
*regcache
= get_thread_regcache (thread
);
1010 struct value
*func_func
;
1011 struct value
*value
;
1012 CORE_ADDR resolved_address
, resolved_pc
;
1014 gdb_assert (b
->type
== bp_gnu_ifunc_resolver_return
);
1016 while (b
->related_breakpoint
!= b
)
1018 struct breakpoint
*b_next
= b
->related_breakpoint
;
1022 case bp_gnu_ifunc_resolver
:
1024 case bp_gnu_ifunc_resolver_return
:
1025 delete_breakpoint (b
);
1028 internal_error (_("handle_inferior_event: Invalid "
1029 "gnu-indirect-function breakpoint type %d"),
1032 b
= gdb::checked_static_cast
<code_breakpoint
*> (b_next
);
1034 gdb_assert (b
->type
== bp_gnu_ifunc_resolver
);
1035 gdb_assert (b
->has_single_location ());
1037 func_func
= value::allocate (func_func_type
);
1038 func_func
->set_lval (lval_memory
);
1039 func_func
->set_address (b
->first_loc ().related_address
);
1041 value
= value::allocate (value_type
);
1042 gdbarch_return_value_as_value (gdbarch
, func_func
, value_type
, regcache
,
1044 resolved_address
= value_as_address (value
);
1045 resolved_pc
= gdbarch_convert_from_func_ptr_addr
1046 (gdbarch
, resolved_address
, current_inferior ()->top_target ());
1047 resolved_pc
= gdbarch_addr_bits_remove (gdbarch
, resolved_pc
);
1049 gdb_assert (current_program_space
== b
->pspace
|| b
->pspace
== NULL
);
1050 elf_gnu_ifunc_record_cache (b
->locspec
->to_string (), resolved_pc
);
1052 b
->type
= bp_breakpoint
;
1053 update_breakpoint_locations (b
, current_program_space
,
1054 find_function_start_sal (resolved_pc
, NULL
, true),
1058 /* A helper function for elf_symfile_read that reads the minimal
1062 elf_read_minimal_symbols (struct objfile
*objfile
, int symfile_flags
,
1063 const struct elfinfo
*ei
)
1065 bfd
*synth_abfd
, *abfd
= objfile
->obfd
.get ();
1066 long symcount
= 0, dynsymcount
= 0, synthcount
, storage_needed
;
1067 asymbol
**symbol_table
= NULL
, **dyn_symbol_table
= NULL
;
1070 symtab_create_debug_printf ("reading minimal symbols of objfile %s",
1071 objfile_name (objfile
));
1073 /* If we already have minsyms, then we can skip some work here.
1074 However, if there were stabs or mdebug sections, we go ahead and
1075 redo all the work anyway, because the psym readers for those
1076 kinds of debuginfo need extra information found here. This can
1077 go away once all types of symbols are in the per-BFD object. */
1078 if (objfile
->per_bfd
->minsyms_read
1079 && ei
->stabsect
== NULL
1080 && ei
->mdebugsect
== NULL
1081 && ei
->ctfsect
== NULL
)
1083 symtab_create_debug_printf ("minimal symbols were previously read");
1087 minimal_symbol_reader
reader (objfile
);
1089 /* Process the normal ELF symbol table first. */
1091 storage_needed
= bfd_get_symtab_upper_bound (objfile
->obfd
.get ());
1092 if (storage_needed
< 0)
1093 error (_("Can't read symbols from %s: %s"),
1094 bfd_get_filename (objfile
->obfd
.get ()),
1095 bfd_errmsg (bfd_get_error ()));
1097 if (storage_needed
> 0)
1099 /* Memory gets permanently referenced from ABFD after
1100 bfd_canonicalize_symtab so it must not get freed before ABFD gets. */
1102 symbol_table
= (asymbol
**) bfd_alloc (abfd
, storage_needed
);
1103 symcount
= bfd_canonicalize_symtab (objfile
->obfd
.get (), symbol_table
);
1106 error (_("Can't read symbols from %s: %s"),
1107 bfd_get_filename (objfile
->obfd
.get ()),
1108 bfd_errmsg (bfd_get_error ()));
1110 elf_symtab_read (reader
, objfile
, ST_REGULAR
, symcount
, symbol_table
,
1114 /* Add the dynamic symbols. */
1116 storage_needed
= bfd_get_dynamic_symtab_upper_bound (objfile
->obfd
.get ());
1118 if (storage_needed
> 0)
1120 /* Memory gets permanently referenced from ABFD after
1121 bfd_get_synthetic_symtab so it must not get freed before ABFD gets.
1122 It happens only in the case when elf_slurp_reloc_table sees
1123 asection->relocation NULL. Determining which section is asection is
1124 done by _bfd_elf_get_synthetic_symtab which is all a bfd
1125 implementation detail, though. */
1127 dyn_symbol_table
= (asymbol
**) bfd_alloc (abfd
, storage_needed
);
1128 dynsymcount
= bfd_canonicalize_dynamic_symtab (objfile
->obfd
.get (),
1131 if (dynsymcount
< 0)
1132 error (_("Can't read symbols from %s: %s"),
1133 bfd_get_filename (objfile
->obfd
.get ()),
1134 bfd_errmsg (bfd_get_error ()));
1136 elf_symtab_read (reader
, objfile
, ST_DYNAMIC
, dynsymcount
,
1137 dyn_symbol_table
, false);
1139 elf_rel_plt_read (reader
, objfile
, dyn_symbol_table
);
1142 /* Contrary to binutils --strip-debug/--only-keep-debug the strip command from
1143 elfutils (eu-strip) moves even the .symtab section into the .debug file.
1145 bfd_get_synthetic_symtab on ppc64 for each function descriptor ELF symbol
1146 'name' creates a new BSF_SYNTHETIC ELF symbol '.name' with its code
1147 address. But with eu-strip files bfd_get_synthetic_symtab would fail to
1148 read the code address from .opd while it reads the .symtab section from
1149 a separate debug info file as the .opd section is SHT_NOBITS there.
1151 With SYNTH_ABFD the .opd section will be read from the original
1152 backlinked binary where it is valid. */
1154 if (objfile
->separate_debug_objfile_backlink
)
1155 synth_abfd
= objfile
->separate_debug_objfile_backlink
->obfd
.get ();
1159 /* Add synthetic symbols - for instance, names for any PLT entries. */
1161 synthcount
= bfd_get_synthetic_symtab (synth_abfd
, symcount
, symbol_table
,
1162 dynsymcount
, dyn_symbol_table
,
1168 std::unique_ptr
<asymbol
*[]>
1169 synth_symbol_table (new asymbol
*[synthcount
]);
1170 for (i
= 0; i
< synthcount
; i
++)
1171 synth_symbol_table
[i
] = synthsyms
+ i
;
1172 elf_symtab_read (reader
, objfile
, ST_SYNTHETIC
, synthcount
,
1173 synth_symbol_table
.get (), true);
1179 /* Install any minimal symbols that have been collected as the current
1180 minimal symbols for this objfile. The debug readers below this point
1181 should not generate new minimal symbols; if they do it's their
1182 responsibility to install them. "mdebug" appears to be the only one
1183 which will do this. */
1187 symtab_create_debug_printf ("done reading minimal symbols");
1190 /* Dwarf-specific helper for elf_symfile_read. Return true if we managed to
1191 load dwarf debug info. */
1194 elf_symfile_read_dwarf2 (struct objfile
*objfile
,
1195 symfile_add_flags symfile_flags
)
1197 bool has_dwarf2
= true;
1199 if (dwarf2_initialize_objfile (objfile
, nullptr, true))
1203 /* If the file has its own symbol tables it has no separate debug
1204 info. `.dynsym'/`.symtab' go to MSYMBOLS, `.debug_info' goes to
1205 SYMTABS/PSYMTABS. `.gnu_debuglink' may no longer be present with
1206 `.note.gnu.build-id'.
1208 .gnu_debugdata is !objfile::has_partial_symbols because it contains only
1209 .symtab, not .debug_* section. But if we already added .gnu_debugdata as
1210 an objfile via find_separate_debug_file_in_section there was no separate
1211 debug info available. Therefore do not attempt to search for another one,
1212 objfile->separate_debug_objfile->separate_debug_objfile GDB guarantees to
1213 be NULL and we would possibly violate it. */
1215 else if (!objfile
->has_partial_symbols ()
1216 && objfile
->separate_debug_objfile
== NULL
1217 && objfile
->separate_debug_objfile_backlink
== NULL
)
1219 if (objfile
->find_and_add_separate_symbol_file (symfile_flags
))
1220 gdb_assert (objfile
->separate_debug_objfile
!= nullptr);
1228 /* Scan and build partial symbols for a symbol file.
1229 We have been initialized by a call to elf_symfile_init, which
1230 currently does nothing.
1232 This function only does the minimum work necessary for letting the
1233 user "name" things symbolically; it does not read the entire symtab.
1234 Instead, it reads the external and static symbols and puts them in partial
1235 symbol tables. When more extensive information is requested of a
1236 file, the corresponding partial symbol table is mutated into a full
1237 fledged symbol table by going back and reading the symbols
1240 We look for sections with specific names, to tell us what debug
1241 format to look for: FIXME!!!
1243 elfstab_build_psymtabs() handles STABS symbols;
1244 mdebug_build_psymtabs() handles ECOFF debugging information.
1246 Note that ELF files have a "minimal" symbol table, which looks a lot
1247 like a COFF symbol table, but has only the minimal information necessary
1248 for linking. We process this also, and use the information to
1249 build gdb's minimal symbol table. This gives us some minimal debugging
1250 capability even for files compiled without -g. */
1253 elf_symfile_read (struct objfile
*objfile
, symfile_add_flags symfile_flags
)
1255 bfd
*abfd
= objfile
->obfd
.get ();
1258 memset ((char *) &ei
, 0, sizeof (ei
));
1259 if (!(objfile
->flags
& OBJF_READNEVER
))
1261 for (asection
*sect
: gdb_bfd_sections (abfd
))
1262 elf_locate_sections (sect
, &ei
);
1265 elf_read_minimal_symbols (objfile
, symfile_flags
, &ei
);
1267 /* ELF debugging information is inserted into the psymtab in the
1268 order of least informative first - most informative last. Since
1269 the psymtab table is searched `most recent insertion first' this
1270 increases the probability that more detailed debug information
1271 for a section is found.
1273 For instance, an object file might contain both .mdebug (XCOFF)
1274 and .debug_info (DWARF2) sections then .mdebug is inserted first
1275 (searched last) and DWARF2 is inserted last (searched first). If
1276 we don't do this then the XCOFF info is found first - for code in
1277 an included file XCOFF info is useless. */
1281 const struct ecoff_debug_swap
*swap
;
1283 /* .mdebug section, presumably holding ECOFF debugging
1285 swap
= get_elf_backend_data (abfd
)->elf_backend_ecoff_debug_swap
;
1287 elfmdebug_build_psymtabs (objfile
, swap
, ei
.mdebugsect
);
1293 /* Stab sections have an associated string table that looks like
1294 a separate section. */
1295 str_sect
= bfd_get_section_by_name (abfd
, ".stabstr");
1297 /* FIXME should probably warn about a stab section without a stabstr. */
1299 elfstab_build_psymtabs (objfile
,
1302 bfd_section_size (str_sect
));
1305 /* Read the CTF section only if there is no DWARF info. */
1306 if (always_read_ctf
&& ei
.ctfsect
)
1308 elfctf_build_psymtabs (objfile
);
1311 bool has_dwarf2
= elf_symfile_read_dwarf2 (objfile
, symfile_flags
);
1313 /* Read the CTF section only if there is no DWARF info. */
1314 if (!always_read_ctf
&& !has_dwarf2
&& ei
.ctfsect
)
1316 elfctf_build_psymtabs (objfile
);
1319 /* Copy relocations are used by some ABIs using the ELF format, so
1320 set the objfile flag indicating this fact. */
1321 objfile
->object_format_has_copy_relocs
= true;
1324 /* Initialize anything that needs initializing when a completely new symbol
1325 file is specified (not just adding some symbols from another file, e.g. a
1329 elf_new_init (struct objfile
*ignore
)
1333 /* Perform any local cleanups required when we are done with a particular
1334 objfile. I.E, we are in the process of discarding all symbol information
1335 for an objfile, freeing up all memory held for it, and unlinking the
1336 objfile struct from the global list of known objfiles. */
1339 elf_symfile_finish (struct objfile
*objfile
)
1343 /* ELF specific initialization routine for reading symbols. */
1346 elf_symfile_init (struct objfile
*objfile
)
1350 /* Implementation of `sym_get_probes', as documented in symfile.h. */
1352 static const elfread_data
&
1353 elf_get_probes (struct objfile
*objfile
)
1355 elfread_data
*probes_per_bfd
= probe_key
.get (objfile
->obfd
.get ());
1357 if (probes_per_bfd
== NULL
)
1359 probes_per_bfd
= probe_key
.emplace (objfile
->obfd
.get ());
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
);
1367 return *probes_per_bfd
;
1372 /* Implementation `sym_probe_fns', as documented in symfile.h. */
1374 static const struct sym_probe_fns elf_probe_fns
=
1376 elf_get_probes
, /* sym_get_probes */
1379 /* Register that we are able to handle ELF object file formats. */
1381 static const struct sym_fns elf_sym_fns
=
1383 elf_new_init
, /* init anything gbl to entire symtab */
1384 elf_symfile_init
, /* read initial info, setup for sym_read() */
1385 elf_symfile_read
, /* read a symbol file into symtab */
1386 elf_symfile_finish
, /* finished with file, cleanup */
1387 default_symfile_offsets
, /* Translate ext. to int. relocation */
1388 elf_symfile_segments
, /* Get segment information from a file. */
1390 default_symfile_relocate
, /* Relocate a debug section. */
1391 &elf_probe_fns
, /* sym_probe_fns */
1394 /* STT_GNU_IFUNC resolver vector to be installed to gnu_ifunc_fns_p. */
1396 static const struct gnu_ifunc_fns elf_gnu_ifunc_fns
=
1398 elf_gnu_ifunc_resolve_addr
,
1399 elf_gnu_ifunc_resolve_name
,
1400 elf_gnu_ifunc_resolver_stop
,
1401 elf_gnu_ifunc_resolver_return_stop
1404 void _initialize_elfread ();
1406 _initialize_elfread ()
1408 add_symtab_fns (bfd_target_elf_flavour
, &elf_sym_fns
);
1410 gnu_ifunc_fns_p
= &elf_gnu_ifunc_fns
;
1412 /* Add "set always-read-ctf on/off". */
1413 add_setshow_boolean_cmd ("always-read-ctf", class_support
, &always_read_ctf
,
1415 Set whether CTF is always read."),
1417 Show whether CTF is always read."),
1419 When off, CTF is only read if DWARF is not present. When on, CTF is read\
1420 regardless of whether DWARF is present."),
1421 nullptr /* set_func */, nullptr /* show_func */,
1422 &setlist
, &showlist
);