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| author | Jozef Lawrynowicz <jozef.l@mittosystems.com> | 2020-11-18 11:51:13 +0000 |
|---|---|---|
| committer | Jozef Lawrynowicz <jozef.l@mittosystems.com> | 2020-11-18 11:51:13 +0000 |
| commit | 99fabbc9739a87ba3433e66792e93b773896790e (patch) | |
| tree | 6a52b12cc648532f3b38fd102cec221a207188ba /ld/ld.texi | |
| parent | 40d9d2fd796a184f04a83ca4442fd78034b5e00b (diff) | |
| download | fsf-binutils-gdb-99fabbc9739a87ba3433e66792e93b773896790e.zip fsf-binutils-gdb-99fabbc9739a87ba3433e66792e93b773896790e.tar.gz fsf-binutils-gdb-99fabbc9739a87ba3433e66792e93b773896790e.tar.bz2 | |
Support SHF_GNU_RETAIN ELF section flag
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.
Diffstat (limited to 'ld/ld.texi')
| -rw-r--r-- | ld/ld.texi | 7 |
1 files changed, 7 insertions, 0 deletions
@@ -1807,6 +1807,9 @@ specified either by one of the options @samp{--entry}, @samp{--undefined}, or @samp{--gc-keep-exported} or by a @code{ENTRY} command in the linker script. +As a GNU extension, ELF input sections marked with the +@code{SHF_GNU_RETAIN} flag will not be garbage collected. + @kindex --print-gc-sections @kindex --no-print-gc-sections @cindex garbage collection @@ -5291,6 +5294,10 @@ The special output section name @samp{/DISCARD/} may be used to discard input sections. Any input sections which are assigned to an output section named @samp{/DISCARD/} are not included in the output file. +This can be used to discard input sections marked with the ELF flag +@code{SHF_GNU_RETAIN}, which would otherwise have been saved from linker +garbage collection. + Note, sections that match the @samp{/DISCARD/} output section will be discarded even if they are in an ELF section group which has other members which are not being discarded. This is deliberate. |