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Support SHF_GNU_RETAIN ELF section flag

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The SHF_GNU_RETAIN section flag is an extension to the GNU ELF OSABI.
It is defined as follows:

=========================================================
Section Attribute Flags
+-------------------------------------+
| Name           | Value              |
+-------------------------------------+
| SHF_GNU_RETAIN | 0x200000 (1 << 21) |
+-------------------------------------+

SHF_GNU_RETAIN
  The link editor should not garbage collect the section.
=========================================================

The .section directive accepts the "R" flag, which indicates
SHF_GNU_RETAIN should be applied to the section.

There is not a direct mapping of SHF_GNU_RETAIN to the BFD
section flag SEC_KEEP. Keeping these flags distinct allows
SHF_GNU_RETAIN sections to be explicitly removed by placing them in
/DISCARD/.

bfd/ChangeLog:

	* elf-bfd.h (enum elf_gnu_osabi): Add elf_gnu_osabi_retain.
	(struct elf_obj_tdata): Increase has_gnu_osabi to 4 bits.
	* elf.c (_bfd_elf_make_section_from_shdr): Set elf_gnu_osabi_retain
	for SHF_GNU_RETAIN.
	(_bfd_elf_final_write_processing): Report if SHF_GNU_RETAIN is
	not supported by the OSABI.
	Adjust error messages.
	* elflink.c (elf_link_input_bfd): Copy enabled has_gnu_osabi bits from
	input BFD to output BFD.
	(bfd_elf_gc_sections): gc_mark the section if SHF_GNU_RETAIN is set.

binutils/ChangeLog:

	* NEWS: Announce SHF_GNU_RETAIN support.
	* readelf.c (get_elf_section_flags): Handle SHF_GNU_RETAIN.
	Recognize SHF_GNU_RETAIN and SHF_GNU_MBIND only for supported OSABIs.
	* testsuite/binutils-all/readelf.exp: Run new tests.
	Don't run run_dump_test when there isn't an assembler available.
	* testsuite/lib/binutils-common.exp (supports_gnu_osabi): Adjust
	comment.
	* testsuite/binutils-all/readelf-maskos-1a.d: New test.
	* testsuite/binutils-all/readelf-maskos-1b.d: New test.
	* testsuite/binutils-all/readelf-maskos.s: New test.
	* testsuite/binutils-all/retain1.s: New test.
	* testsuite/binutils-all/retain1a.d: New test.
	* testsuite/binutils-all/retain1b.d: New test.

gas/ChangeLog:

	* NEWS: Announce SHF_GNU_RETAIN support.
	* config/obj-elf.c (obj_elf_change_section): Merge SHF_GNU_RETAIN bit
	between section declarations.
	(obj_elf_parse_section_letters): Handle 'R' flag.
	Handle numeric flag values within the SHF_MASKOS range.
	(obj_elf_section): Validate SHF_GNU_RETAIN usage.
	* doc/as.texi: Document 'R' flag to .section directive.
	* testsuite/gas/elf/elf.exp: Run new tests.
	* testsuite/gas/elf/section10.d: Unset SHF_GNU_RETAIN bit.
	* testsuite/gas/elf/section10.s: Likewise.
	* testsuite/gas/elf/section22.d: New test.
	* testsuite/gas/elf/section22.s: New test.
	* testsuite/gas/elf/section23.s: New test.
	* testsuite/gas/elf/section23a.d: New test.
	* testsuite/gas/elf/section23b.d: New test.
	* testsuite/gas/elf/section23b.err: New test.
	* testsuite/gas/elf/section24.l: New test.
	* testsuite/gas/elf/section24.s: New test.
	* testsuite/gas/elf/section24a.d: New test.
	* testsuite/gas/elf/section24b.d: New test.

include/ChangeLog:

	* elf/common.h (SHF_GNU_RETAIN): Define.

ld/ChangeLog:

	* NEWS: Announce support for SHF_GNU_RETAIN.
	* ld.texi (garbage collection): Document SHF_GNU_RETAIN.
	(Output Section Discarding): Likewise.
	* testsuite/ld-elf/elf.exp: Run new tests.
	* testsuite/ld-elf/retain1.s: New test.
	* testsuite/ld-elf/retain1a.d: New test.
	* testsuite/ld-elf/retain1b.d: New test.
	* testsuite/ld-elf/retain2.d: New test.
	* testsuite/ld-elf/retain2.ld: New test.
	* testsuite/ld-elf/retain2.map: New test.
	* testsuite/ld-elf/retain3.d: New test.
	* testsuite/ld-elf/retain3.s: New test.
	* testsuite/ld-elf/retain4.d: New test.
	* testsuite/ld-elf/retain4.s: New test.
	* testsuite/ld-elf/retain5.d: New test.
	* testsuite/ld-elf/retain5.map: New test.
	* testsuite/ld-elf/retain5lib.s: New test.
	* testsuite/ld-elf/retain5main.s: New test.
	* testsuite/ld-elf/retain6a.d: New test.
	* testsuite/ld-elf/retain6b.d: New test.
	* testsuite/ld-elf/retain6lib.s: New test.
	* testsuite/ld-elf/retain6main.s: New test.
This commit is contained in:
Jozef Lawrynowicz 2020-11-18 11:51:13 +00:00
parent 40d9d2fd79
commit 99fabbc973
55 changed files with 944 additions and 42 deletions
Download patch file Download diff file Expand all files Collapse all files

12
bfd/elflink.c
View file

@ -10746,6 +10746,14 @@ elf_link_input_bfd (struct elf_final_link_info *flinfo, bfd *input_bfd)
extsymoff = symtab_hdr->sh_info;
}
/* Enable GNU OSABI features in the output BFD that are used in the input
BFD. */
if (bed->elf_osabi == ELFOSABI_NONE
|| bed->elf_osabi == ELFOSABI_GNU
|| bed->elf_osabi == ELFOSABI_FREEBSD)
elf_tdata (output_bfd)->has_gnu_osabi
|= elf_tdata (input_bfd)->has_gnu_osabi;
/* Read the local symbols. */
isymbuf = (Elf_Internal_Sym *) symtab_hdr->contents;
if (isymbuf == NULL && locsymcount != 0)
@ -14116,7 +14124,9 @@ bfd_elf_gc_sections (bfd *abfd, struct bfd_link_info *info)
== SHT_FINI_ARRAY)))
|| (elf_section_data (o)->this_hdr.sh_type == SHT_NOTE
&& elf_next_in_group (o) == NULL
&& elf_linked_to_section (o) == NULL)))
&& elf_linked_to_section (o) == NULL)
|| ((elf_tdata (sub)->has_gnu_osabi & elf_gnu_osabi_retain)
&& (elf_section_flags (o) & SHF_GNU_RETAIN))))
{
if (!_bfd_elf_gc_mark (info, o, gc_mark_hook))
return FALSE;