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Apply a workaround to mitigate a quadratic performance hit in the linker when writing out secondary reloc sections.

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PR 26406
	* elf-bfd.h (struct bfd_elf_section_data): Add
	has_secondary_relocs field.
	* elf.c (_bfd_elf_copy_special_section_fields): Set the
	has_secondary_relocs field for sections which have associated
	secondary relocs.
	* elfcode.h (elf_write_relocs): Only call write_secondary_relocs
	on sections which have associated secondary relocs.
This commit is contained in:
Nick Clifton
2020-08-20 10:19:47 +01:00
parent c2fd7faea8
commit 44466e45c5
4 changed files with 34 additions and 7 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
bfd/ChangeLog
View File

@ -1,3 +1,14 @@
2020-08-20 Nick Clifton <nickc@redhat.com>
PR 26406
* elf-bfd.h (struct bfd_elf_section_data): Add
has_secondary_relocs field.
* elf.c (_bfd_elf_copy_special_section_fields): Set the
has_secondary_relocs field for sections which have associated
secondary relocs.
* elfcode.h (elf_write_relocs): Only call write_secondary_relocs
on sections which have associated secondary relocs.
2020-08-15 Alan Modra <amodra@gmail.com>
* elf32-frv.c (elf32_frv_add_symbol_hook): Set SEC_SMALL_DATA on

5
bfd/elf-bfd.h
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@ -1756,6 +1756,11 @@ struct bfd_elf_section_data
/* Link from a text section to its .eh_frame_entry section. */
asection *eh_frame_entry;
/* TRUE if the section has secondary reloc sections associated with it.
FIXME: In the future it might be better to change this into a list
of secondary reloc sections, making lookup easier and faster. */
bfd_boolean has_secondary_relocs;
/* A pointer used for various section optimizations. */
void *sec_info;
};

22
bfd/elf.c
View File

@ -12714,6 +12714,7 @@ _bfd_elf_copy_special_section_fields (const bfd * ibfd ATTRIBUTE_UNUSED,
{
asection * isec;
asection * osec;
struct bfd_elf_section_data * esd;
if (isection == NULL)
return FALSE;
@ -12729,8 +12730,9 @@ _bfd_elf_copy_special_section_fields (const bfd * ibfd ATTRIBUTE_UNUSED,
if (osec == NULL)
return FALSE;
BFD_ASSERT (elf_section_data (osec)->sec_info == NULL);
elf_section_data (osec)->sec_info = elf_section_data (isec)->sec_info;
esd = elf_section_data (osec);
BFD_ASSERT (esd->sec_info == NULL);
esd->sec_info = elf_section_data (isec)->sec_info;
osection->sh_type = SHT_RELA;
osection->sh_link = elf_onesymtab (obfd);
if (osection->sh_link == 0)
@ -12770,18 +12772,26 @@ _bfd_elf_copy_special_section_fields (const bfd * ibfd ATTRIBUTE_UNUSED,
return FALSE;
}
osection->sh_info =
elf_section_data (isection->bfd_section->output_section)->this_idx;
esd = elf_section_data (isection->bfd_section->output_section);
BFD_ASSERT (esd != NULL);
osection->sh_info = esd->this_idx;
esd->has_secondary_relocs = TRUE;
#if DEBUG_SECONDARY_RELOCS
fprintf (stderr, "update header of %s, sh_link = %u, sh_info = %u\n",
osec->name, osection->sh_link, osection->sh_info);
fprintf (stderr, "mark section %s as having secondary relocs\n",
bfd_section_name (isection->bfd_section->output_section));
#endif
return TRUE;
}
/* Write out a secondary reloc section. */
/* Write out a secondary reloc section.
FIXME: Currently this function can result in a serious performance penalty
for files with secondary relocs and lots of sections. The proper way to
fix this is for _bfd_elf_copy_special_section_fields() to chain secondary
relocs together and then to have this function just walk that chain. */
bfd_boolean
_bfd_elf_write_secondary_reloc_section (bfd *abfd, asection *sec)

3
bfd/elfcode.h
View File

@ -999,7 +999,8 @@ elf_write_relocs (bfd *abfd, asection *sec, void *data)
(*swap_out) (abfd, &src_rela, dst_rela);
}
if (!bed->write_secondary_relocs (abfd, sec))
if (elf_section_data (sec)->has_secondary_relocs
&& !bed->write_secondary_relocs (abfd, sec))
{
*failedp = TRUE;
return;