binutils-gdb/ld
Jozef Lawrynowicz 99fabbc973 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.
2020-11-18 11:51:13 +00:00
..
emulparams Fix compile time warning 2020-11-03 08:56:27 +00:00
emultempl After preventing creating an import library for an exe when there are no exports, to avoid a crash, it turned out that some projects expected to be able to create an import library for a dll with no exports, so more closely match the condition to the condition around initializing the dll name. 2020-09-30 10:50:46 +01:00
po Update the Spanish translation for the ld/ subdirectory. 2020-11-16 12:32:06 +00:00
scripttempl MSP430: Fix alignment of __*_array_start symbols in default linker script 2020-08-28 14:01:10 +01:00
testsuite Support SHF_GNU_RETAIN ELF section flag 2020-11-18 11:51:13 +00:00
.gitignore
aclocal.m4
ChangeLog Support SHF_GNU_RETAIN ELF section flag 2020-11-18 11:51:13 +00:00
ChangeLog-0001
ChangeLog-0203 Add copyright notices 2012-12-10 12:48:03 +00:00
ChangeLog-2004 Add copyright notices 2012-12-10 12:48:03 +00:00
ChangeLog-2005
ChangeLog-2006
ChangeLog-2007
ChangeLog-2008
ChangeLog-2009
ChangeLog-2010
ChangeLog-2011
ChangeLog-2012
ChangeLog-2013
ChangeLog-2014
ChangeLog-2015
ChangeLog-2016
ChangeLog-2017
ChangeLog-2018
ChangeLog-2019
ChangeLog-9197
ChangeLog-9899
config.in Add a new option to the linker: --error-handling-script=<NAME>. Run the script <NAME> if an undefined symbol or unfound library error is encountered. 2020-10-16 11:37:26 +01:00
configure Add a new option to the linker: --error-handling-script=<NAME>. Run the script <NAME> if an undefined symbol or unfound library error is encountered. 2020-10-16 11:37:26 +01:00
configure.ac Add a new option to the linker: --error-handling-script=<NAME>. Run the script <NAME> if an undefined symbol or unfound library error is encountered. 2020-10-16 11:37:26 +01:00
configure.host
configure.tgt PR26667, Add powerpc64le-*-freebsd* support 2020-10-06 17:09:27 +10:30
deffile.h
deffilep.y
dep-in.sed
elf-hints-local.h
fdl.texi
gen-doc.texi
genscrba.sh
genscripts.sh
h8-doc.texi
ld.h ld: new options --ctf-variables and --ctf-share-types 2020-07-22 18:03:57 +01:00
ld.texi Support SHF_GNU_RETAIN ELF section flag 2020-11-18 11:51:13 +00:00
ldbuildid.c
ldbuildid.h
ldcref.c Update year range in copyright notice of binutils files 2020-01-01 18:42:54 +10:30
ldctor.c
ldctor.h
ldelf.c elf: Set rel_from_abs to 1 for __ehdr_start 2020-11-13 15:44:47 -08:00
ldelf.h
ldelfgen.c
ldelfgen.h Update year range in copyright notice of binutils files 2020-01-01 18:42:54 +10:30
ldemul.c
ldemul.h
ldexp.c
ldexp.h
ldfile.c Add a new option to the linker: --error-handling-script=<NAME>. Run the script <NAME> if an undefined symbol or unfound library error is encountered. 2020-10-16 11:37:26 +01:00
ldfile.h
ldgram.y
ldint.texi
ldlang.c ld: Allow symbols from PROVIDE to be use in MEMORY regions 2020-10-16 13:43:49 +01:00
ldlang.h
ldlex-wrapper.c
ldlex.h Add a new option to the linker: --error-handling-script=<NAME>. Run the script <NAME> if an undefined symbol or unfound library error is encountered. 2020-10-16 11:37:26 +01:00
ldlex.l Use xmalloc rather than malloc 2020-08-03 10:59:38 +09:30
ldmain.c Invoke the linker's error handling script with the keyword "undefined-symbol" when using it to help with undefined symbol errors. 2020-10-26 12:39:50 +00:00
ldmain.h Add a new option to the linker: --error-handling-script=<NAME>. Run the script <NAME> if an undefined symbol or unfound library error is encountered. 2020-10-16 11:37:26 +01:00
ldmisc.c LD: Add new %pU vfinfo format for printing linker script name 2020-08-28 14:00:54 +01:00
ldmisc.h
ldver.c
ldver.h Update year range in copyright notice of binutils files 2020-01-01 18:42:54 +10:30
ldwrite.c
ldwrite.h
lexsup.c Extend ld's -Map=<dir> functionality by allowing '%' to be replaced with the output file path. 2020-11-06 14:36:45 +00:00
MAINTAINERS
Makefile.am Fix regexp for development.exp 2020-11-09 12:05:39 +01:00
Makefile.in Fix regexp for development.exp 2020-11-09 12:05:39 +01:00
mri.c
mri.h
NEWS Support SHF_GNU_RETAIN ELF section flag 2020-11-18 11:51:13 +00:00
pe-dll.c Change the default characteristics of DLLs built by the linker to more secure settings. 2020-08-27 12:58:27 +01:00
pe-dll.h
pep-dll.c
pep-dll.h
plugin.c ld: Override the IR definition for non-ELF targets 2020-09-30 05:23:35 -07:00
plugin.h
README
stamp-h.in
sysdep.h
testplug2.c
testplug3.c
testplug4.c
testplug.c Do without ld ENABLE_PLUGINS 2020-06-21 22:16:10 +09:30
TODO

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		README for LD

This is the GNU linker.  It is distributed with other "binary
utilities" which should be in ../binutils.  See ../binutils/README for
more general notes, including where to send bug reports.

There are many features of the linker:

* The linker uses a Binary File Descriptor library (../bfd)
  that it uses to read and write object files.  This helps
  insulate the linker itself from the format of object files.

* The linker supports a number of different object file
  formats.  It can even handle multiple formats at once:
  Read two input formats and write a third.

* The linker can be configured for cross-linking.

* The linker supports a control language.

* There is a user manual (ld.texi), as well as the
  beginnings of an internals manual (ldint.texi).

Installation
============

See ../binutils/README.

If you want to make a cross-linker, you may want to specify
a different search path of -lfoo libraries than the default.
You can do this by setting the LIB_PATH variable in ./Makefile
or using the --with-lib-path configure switch.

To build just the linker, make the target all-ld from the top level
directory (one directory above this one).

Porting to a new target
=======================

See the ldint.texi manual.

Reporting bugs etc
===========================

See ../binutils/README.

Known problems
==============

The Solaris linker normally exports all dynamic symbols from an
executable.  The GNU linker does not do this by default.  This is
because the GNU linker tries to present the same interface for all
similar targets (in this case, all native ELF targets).  This does not
matter for normal programs, but it can make a difference for programs
which try to dlopen an executable, such as PERL or Tcl.  You can make
the GNU linker export all dynamic symbols with the -E or
--export-dynamic command line option.

HP/UX 9.01 has a shell bug that causes the linker scripts to be
generated incorrectly.  The symptom of this appears to be "fatal error
- scanner input buffer overflow" error messages.  There are various
workarounds to this:
  * Build and install bash, and build with "make SHELL=bash".
  * Update to a version of HP/UX with a working shell (e.g., 9.05).
  * Replace "(. ${srcdir}/scripttempl/${SCRIPT_NAME}.sc)" in
    genscripts.sh with "sh ${srcdir}..." (no parens) and make sure the
    emulparams script used exports any shell variables it sets.

Copyright (C) 2012-2020 Free Software Foundation, Inc.

Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
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