7bdf4127c3
This commit adds a new linker feature: the ability to resolve section groups as part of a relocatable link. Currently section groups are automatically resolved when performing a final link, and are carried through when performing a relocatable link. By carried through this means that one copy of each section group (from all the copies that might be found in all the input files) is placed into the output file. Sections that are part of a section group will not match input section specifiers within a linker script and are forcibly kept as separate sections. There is a slight resemblance between section groups and common section. Like section groups, common sections are carried through when performing a relocatable link, and resolved (allocated actual space) only at final link time. However, with common sections there is an ability to force the linker to allocate space for the common sections when performing a relocatable link, there's currently no such ability for section groups. This commit adds such a mechanism. This new facility can be accessed in two ways, first there's a command line switch --force-group-allocation, second, there's a new linker script command FORCE_GROUP_ALLOCATION. If one of these is used when performing a relocatable link then the linker will resolve the section groups as though it were performing a final link, the section group will be deleted, and the members of the group will be placed like normal input sections. If there are multiple copies of the group (from multiple input files) then only one copy of the group members will be placed, the duplicate copies will be discarded. Unlike common sections that have the --no-define-common command line flag, and INHIBIT_COMMON_ALLOCATION linker script command there is no way to prevent group resolution during a final link, this is because the ELF gABI specifically prohibits the presence of SHT_GROUP sections in a fully linked executable. However, the code as written should make adding such a feature trivial, setting the new resolve_section_groups flag to false during a final link should work as you'd expect. bfd/ChangeLog: * elf.c (_bfd_elf_make_section_from_shdr): Don't initially mark SEC_GROUP sections as SEC_EXCLUDE. (bfd_elf_set_group_contents): Replace use of abort with an assert. (assign_section_numbers): Use resolve_section_groups flag instead of relocatable link type. (_bfd_elf_init_private_section_data): Use resolve_section_groups flag instead of checking the final_link flag for part of the checks in here. Fix white space as a result. * elflink.c (elf_link_input_bfd): Use resolve_section_groups flag instead of relocatable link type. (bfd_elf_final_link): Likewise. include/ChangeLog: * bfdlink.h (struct bfd_link_info): Add new resolve_section_groups flag. ld/ChangeLog: * ld.h (struct args_type): Add force_group_allocation field. * ldgram.y: Add support for FORCE_GROUP_ALLOCATION. * ldlex.h: Likewise. * ldlex.l: Likewise. * lexsup.c: Likewise. * ldlang.c (unique_section_p): Check resolve_section_groups flag not the relaxable link flag. (lang_add_section): Discard section groups when we're resolving groups. Clear the SEC_LINK_ONCE flag if we're resolving section groups. * ldmain.c (main): Initialise resolve_section_groups flag in link_info based on command line flags. * testsuite/ld-elf/group11.d: New file. * testsuite/ld-elf/group12.d: New file. * testsuite/ld-elf/group12.ld: New file. * NEWS: Mention new features. * ld.texinfo (Options): Document --force-group-allocation. (Miscellaneous Commands): Document FORCE_GROUP_ALLOCATION. |
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| .. | ||
| emulparams | ||
| emultempl | ||
| po | ||
| scripttempl | ||
| testsuite | ||
| .gitignore | ||
| aclocal.m4 | ||
| ChangeLog | ||
| ChangeLog-0001 | ||
| ChangeLog-0203 | ||
| ChangeLog-2004 | ||
| 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-9197 | ||
| ChangeLog-9899 | ||
| config.in | ||
| configure | ||
| configure.ac | ||
| configure.host | ||
| configure.tgt | ||
| 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.texinfo | ||
| ldbuildid.c | ||
| ldbuildid.h | ||
| ldcref.c | ||
| ldctor.c | ||
| ldctor.h | ||
| ldemul.c | ||
| ldemul.h | ||
| ldexp.c | ||
| ldexp.h | ||
| ldfile.c | ||
| ldfile.h | ||
| ldgram.y | ||
| ldint.texinfo | ||
| ldlang.c | ||
| ldlang.h | ||
| ldlex-wrapper.c | ||
| ldlex.h | ||
| ldlex.l | ||
| ldmain.c | ||
| ldmain.h | ||
| ldmisc.c | ||
| ldmisc.h | ||
| ldver.c | ||
| ldver.h | ||
| ldwrite.c | ||
| ldwrite.h | ||
| lexsup.c | ||
| MAINTAINERS | ||
| Makefile.am | ||
| Makefile.in | ||
| mri.c | ||
| mri.h | ||
| NEWS | ||
| pe-dll.c | ||
| pe-dll.h | ||
| pep-dll.c | ||
| pep-dll.h | ||
| plugin.c | ||
| plugin.h | ||
| README | ||
| stamp-h.in | ||
| sysdep.h | ||
| testplug2.c | ||
| testplug3.c | ||
| testplug4.c | ||
| testplug.c | ||
| TODO | ||
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.texinfo), as well as the
beginnings of an internals manual (ldint.texinfo).
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.texinfo 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) 2012-2017 Free Software Foundation, Inc.
Copying and distribution of this file, with or without modification,
are permitted in any medium without royalty provided the copyright
notice and this notice are preserved.