binutils-gdb/ld
H.J. Lu f6aec96dce ld: Add --enable-separate-code
This patch adds --enable-separate-code to ld configure to turn on
-z separate-code by default and enables it by default for Linux/x86.
This avoids mixing code pages with data to improve cache performance
as well as security.

To reduce x86-64 executable and shared object sizes, the maximum page
size is reduced from 2MB to 4KB when -z separate-code is turned on by
default.  Note: -z max-page-size= can be used to set the maximum page
size.

We compared SPEC CPU 2017 performance before and after this change on
Skylake server.  There are no any significant performance changes.
Everything is mostly below +/-1%.

bfd/

	* config.in: Regenerated.
	* configure: Likewise.
	* configure.ac: Add --enable-separate-code.
	(DEFAULT_LD_Z_SEPARATE_CODE): New AC_DEFINE_UNQUOTED.  Default
	to 1 for Linux/x86 targets,
	* elf64-x86-64.c (ELF_MAXPAGESIZE): Set to 0x1000 if
	DEFAULT_LD_Z_SEPARATE_CODE is 1.

ld/

	* NEWS: Mention --enable-separate-code.
	* configure.ac: Add --enable-separate-code.
	(DEFAULT_LD_Z_SEPARATE_CODE): New AC_DEFINE_UNQUOTED.
	* configure.tgt: Default ac_default_ld_z_separate_code to 1 for
	Linux/x86 targets.
	* config.in: Regenerated.
	* configure: Likewise.
	* emultempl/elf32.em (gld${EMULATION_NAME}_before_parse): Set
	link_info.separate_code DEFAULT_LD_Z_SEPARATE_CODE.
2018-02-27 11:34:29 -08:00
..
emulparams ld error/warning messages 2018-02-26 10:51:12 +10:30
emultempl ld: Add --enable-separate-code 2018-02-27 11:34:29 -08:00
po ld message translation for emultempl and emulparams 2018-02-26 10:51:12 +10:30
scripttempl
testsuite ld error/warning messages 2018-02-26 10:51:12 +10:30
.gitignore
aclocal.m4
ChangeLog ld: Add --enable-separate-code 2018-02-27 11:34:29 -08:00
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-9197
ChangeLog-9899
config.in ld: Add --enable-separate-code 2018-02-27 11:34:29 -08:00
configure ld: Add --enable-separate-code 2018-02-27 11:34:29 -08:00
configure.ac ld: Add --enable-separate-code 2018-02-27 11:34:29 -08:00
configure.host
configure.tgt ld: Add --enable-separate-code 2018-02-27 11:34:29 -08:00
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 ld error/warning messages 2018-02-26 10:51:12 +10:30
ldctor.c ld error/warning messages 2018-02-26 10:51:12 +10:30
ldctor.h
ldemul.c
ldemul.h
ldexp.c ld error/warning messages 2018-02-26 10:51:12 +10:30
ldexp.h
ldfile.c ld error/warning messages 2018-02-26 10:51:12 +10:30
ldfile.h
ldgram.y ld error/warning messages 2018-02-26 10:51:12 +10:30
ldint.texinfo
ldlang.c ld error/warning messages 2018-02-26 10:51:12 +10:30
ldlang.h
ldlex-wrapper.c
ldlex.h
ldlex.l
ldmain.c ld error/warning messages 2018-02-26 10:51:12 +10:30
ldmain.h
ldmisc.c ld error/warning messages 2018-02-26 10:51:12 +10:30
ldmisc.h
ldver.c
ldver.h
ldwrite.c ld error/warning messages 2018-02-26 10:51:12 +10:30
ldwrite.h
lexsup.c ld error/warning messages 2018-02-26 10:51:12 +10:30
MAINTAINERS
Makefile.am ld message translation for emultempl and emulparams 2018-02-26 10:51:12 +10:30
Makefile.in ld message translation for emultempl and emulparams 2018-02-26 10:51:12 +10:30
mri.c ld error/warning messages 2018-02-26 10:51:12 +10:30
mri.h
NEWS ld: Add --enable-separate-code 2018-02-27 11:34:29 -08:00
pe-dll.c ld error/warning messages 2018-02-26 10:51:12 +10:30
pe-dll.h
pep-dll.c
pep-dll.h
plugin.c ld error/warning messages 2018-02-26 10:51:12 +10:30
plugin.h
README
stamp-h.in
sysdep.h
testplug2.c
testplug3.c
testplug4.c
testplug.c
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.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) 2012-2018 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.