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bfd: Improve nm and objdump without section header

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When there is no section header in an executable or shared library, we
reconstruct dynamic symbol table from the PT_DYNAMIC segment, which
contains DT_HASH/DT_GNU_HASH/DT_MIPS_XHASH, DT_STRTAB, DT_SYMTAB,
DT_STRSZ, and DT_SYMENT entries, to improve nm and objdump.  For DT_HASH,
the number of dynamic symbol table entries equals the number of chains.
For DT_GNU_HASH/DT_MIPS_XHASH, only defined symbols with non-STB_LOCAL
indings are in hash table.  Since DT_GNU_HASH/DT_MIPS_XHASH place all
symbols with STB_LOCAL binding before symbols with other bindings and
all undefined symbols defined ones in dynamic symbol table, the highest
symbol index in DT_GNU_HASH/DT_MIPS_XHASH is the highest dynamic symbol
table index.  We can also get symbol version from DT_VERSYM, DT_VERDEF
and DT_VERNEED entries.

dt_symtab, dt_versym, dt_verdef, dt_verneed, dt_symtab_count,
dt_verdef_count, dt_verneed_count and dt_strtab are added to
elf_obj_tdata to store dynamic symbol table information.

	PR ld/25617
	* elf-bfd.h (elf_obj_tdata): Add dt_symtab, dt_verdef, dt_verneed,
	dt_symtab_count, dt_verdef_count, dt_verneed_count and dt_strtab.
	(elf_use_dt_symtab_p): New.
	(_bfd_elf_get_dynamic_symbols): Likewise.
	(_bfd_elf_get_section_from_dynamic_symbol): Likewise.
	* elf.c (bfd_elf_get_elf_syms): Use dynamic symbol table if
	neeeded.
	(_bfd_elf_get_dynamic_symtab_upper_bound): Likewise.
	(_bfd_elf_slurp_version_tables): Likewise.
	(offset_from_vma): New function.
	(get_hash_table_data): Likewise.
	(_bfd_elf_get_dynamic_symbols): Likewise.
	(_bfd_elf_get_section_from_dynamic_symbol): Likewise.
	(_bfd_elf_get_symbol_version_name): Likewise.
	* elfcode.h (elf_object_p): Call _bfd_elf_get_dynamic_symbols
	to reconstruct dynamic symbol table from PT_DYNAMIC segment if
	there is no section header.
	(elf_slurp_symbol_table): Use dynamic symbol table if neeeded.
	Don't free isymbuf when dynamic symbol table is used.
	* elflink.c (elf_link_is_defined_archive_symbol): Return wrong
	format error when dynamic symbol table is used.
	(elf_link_add_object_symbols): Likewise.
This commit is contained in:
H.J. Lu
2020-03-04 20:32:35 -08:00
parent 02c1ba6c94
commit 46675b6b81
4 changed files with 748 additions and 67 deletions
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12
bfd/elflink.c
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@@ -3571,6 +3571,12 @@ elf_link_is_defined_archive_symbol (bfd * abfd, carsym * symdef)
if (! bfd_check_format (abfd, bfd_object))
return false;
if (elf_use_dt_symtab_p (abfd))
{
bfd_set_error (bfd_error_wrong_format);
return false;
}
/* Select the appropriate symbol table. If we don't know if the
object file is an IR object, give linker LTO plugin a chance to
get the correct symbol table. */
@@ -4233,6 +4239,12 @@ elf_link_add_object_symbols (bfd *abfd, struct bfd_link_info *info)
htab = elf_hash_table (info);
bed = get_elf_backend_data (abfd);
if (elf_use_dt_symtab_p (abfd))
{
bfd_set_error (bfd_error_wrong_format);
return false;
}
if ((abfd->flags & DYNAMIC) == 0)
dynamic = false;
else