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The linker merges all the input .sframe sections. When merging, the linker verifies that all the input .sframe sections have the same abi/arch. The linker uses libsframe library to perform key actions on the .sframe sections - decode, read, and create output data. This implies buildsystem changes to make and install libsframe before libbfd. The linker places the output .sframe section in a new segment of its own: PT_GNU_SFRAME. A new segment is not added, however, if the generated .sframe section is empty. When a section is discarded from the final link, the corresponding entries in the .sframe section for those functions are also deleted. The linker sorts the SFrame FDEs on start address by default and sets the SFRAME_F_FDE_SORTED flag in the .sframe section. This patch also adds support for generation of SFrame unwind information for the .plt* sections on x86_64. SFrame unwind info is generated for IBT enabled PLT, lazy/non-lazy PLT. The existing linker option --no-ld-generated-unwind-info has been adapted to include the control of whether .sframe unwind information will be generated for the linker generated sections like PLT. Changes to the linker script have been made as necessary. ChangeLog: * Makefile.def: Add install dependency on libsframe for libbfd. * Makefile.in: Regenerated. * bfd/Makefile.am: Add elf-sframe.c * bfd/Makefile.in: Regenerated. * bfd/bfd-in2.h (SEC_INFO_TYPE_SFRAME): Regenerated. * bfd/configure: Regenerate. * bfd/configure.ac: Add elf-sframe.lo. * bfd/elf-bfd.h (struct sframe_func_bfdinfo): New struct. (struct sframe_dec_info): Likewise. (struct sframe_enc_info): Likewise. (struct elf_link_hash_table): New member for encoded .sframe object. (struct output_elf_obj_tdata): New member. (elf_sframe): New access macro. (_bfd_elf_set_section_sframe): New declaration. * bfd/elf.c (get_segment_type): Handle new segment PT_GNU_SFRAME. (bfd_section_from_phdr): Likewise. (get_program_header_size): Likewise. (_bfd_elf_map_sections_to_segments): Likewise. * bfd/elf64-x86-64.c (elf_x86_64_link_setup_gnu_properties): Add contents to the .sframe sections or .plt* entries. * bfd/elflink.c (elf_section_ignore_discarded_relocs): Handle SEC_INFO_TYPE_SFRAME. (_bfd_elf_default_action_discarded): Handle .sframe section. (elf_link_input_bfd): Merge .sframe section. (bfd_elf_final_link): Write the output .sframe section. (bfd_elf_discard_info): Handle discarding .sframe section. * bfd/elfxx-x86.c (_bfd_x86_elf_size_dynamic_sections): Create .sframe section for .plt and .plt.sec. (_bfd_x86_elf_finish_dynamic_sections): Handle .sframe from .plt* sections. * bfd/elfxx-x86.h (PLT_SFRAME_FDE_START_OFFSET): New definition. (SFRAME_PLT0_MAX_NUM_FRES): Likewise. (SFRAME_PLTN_MAX_NUM_FRES): Likewise. (struct elf_x86_sframe_plt): New structure. (struct elf_x86_link_hash_table): New member. (struct elf_x86_init_table): New members for .sframe creation. * bfd/section.c: Add new definition SEC_INFO_TYPE_SFRAME. * binutils/readelf.c (get_segment_type): Handle new segment PT_GNU_SFRAME. * ld/ld.texi: Update documentation for --no-ld-generated-unwind-info. * ld/scripttempl/elf.sc: Support .sframe sections. * ld/Makefile.am (TESTSFRAMELIB): Use it. (check-DEJAGNU): Likewise. * ld/Makefile.in: Regenerated. * ld/configure.ac (TESTSFRAMELIB): Set to the .so or .a like TESTBFDLIB. * ld/configure: Regenerated. * bfd/elf-sframe.c: New file. include/ChangeLog: * elf/common.h (PT_GNU_SFRAME): New definition. * elf/internal.h (struct elf_segment_map): Handle new segment type PT_GNU_SFRAME. ld/testsuite/ChangeLog: * ld/testsuite/ld-bootstrap/bootstrap.exp: Add SFRAMELIB. * ld/testsuite/ld-aarch64/aarch64-elf.exp: Add new test sframe-simple-1. * ld/testsuite/ld-aarch64/sframe-bar.s: New file. * ld/testsuite/ld-aarch64/sframe-foo.s: Likewise. * ld/testsuite/ld-aarch64/sframe-simple-1.d: Likewise. * ld/testsuite/ld-sframe/sframe-empty.d: New test. * ld/testsuite/ld-sframe/sframe-empty.s: New file. * ld/testsuite/ld-sframe/sframe.exp: New testsuite. * ld/testsuite/ld-x86-64/sframe-bar.s: New file. * ld/testsuite/ld-x86-64/sframe-foo.s: Likewise. * ld/testsuite/ld-x86-64/sframe-simple-1.d: Likewise. * ld/testsuite/ld-x86-64/sframe-plt-1.d: Likewise. * ld/testsuite/ld-x86-64/sframe-simple-1.d: Likewise. * ld/testsuite/ld-x86-64/x86-64.exp: Add new tests - sframe-simple-1, sframe-plt-1. * ld/testsuite/lib/ld-lib.exp: Add new proc to check if assembler supports SFrame section. * ld/testsuite/ld-sframe/discard.d: New file. * ld/testsuite/ld-sframe/discard.ld: Likewise. * ld/testsuite/ld-sframe/discard.s: Likewise. |
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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-2017 | ||
ChangeLog-2018 | ||
ChangeLog-2019 | ||
ChangeLog-2020 | ||
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.texi | ||
ldbuildid.c | ||
ldbuildid.h | ||
ldcref.c | ||
ldctor.c | ||
ldctor.h | ||
ldelf.c | ||
ldelf.h | ||
ldelfgen.c | ||
ldelfgen.h | ||
ldemul.c | ||
ldemul.h | ||
ldexp.c | ||
ldexp.h | ||
ldfile.c | ||
ldfile.h | ||
ldgram.y | ||
ldint.texi | ||
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 | ||
libdep_plugin.c | ||
MAINTAINERS | ||
Makefile.am | ||
Makefile.in | ||
mri.c | ||
mri.h | ||
NEWS | ||
pdb.c | ||
pdb.h | ||
pe-dll.c | ||
pe-dll.h | ||
pep-dll-aarch64.c | ||
pep-dll-x86_64.c | ||
pep-dll.c | ||
pep-dll.h | ||
plugin.c | ||
plugin.h | ||
README | ||
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.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) 2012-2022 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.