binutils-gdb/ld
Alan Modra f378ab099d PPC64_OPT_LOCALENTRY
ELFv2 functions with localentry:0 are those with a single entry point,
ie. global entry == local entry, and that have no requirement on r2 or
r12, and guarantee r2 is unchanged on return.  Such an external
function can be called via the PLT without saving r2 or restoring it
on return, avoiding a common load-hit-store for small functions.   The
optimization is attractive.  The TOC pointer load-hit-store is a major
reason why calls to small functions that need no register saves, or
with shrink-wrap, no register saves on a fast path, are slow on
powerpc64le.

To be safe, this optimization needs ld.so support to check that the
run-time matches link-time function implementation.  If a function
in a shared library with st_other localentry non-zero is called
without saving and restoring r2, r2 will be trashed on return, leading
to segfaults.  For that reason the optimization does not happen for
weak functions since a weak definition is a fairly solid hint that the
function will likely be overridden.  I'm also not enabling the
optimization by default unless glibc-2.26 is detected, which should
have the ld.so checks implemented.

bfd/
	* elf64-ppc.c (struct ppc_link_hash_table): Add has_plt_localentry0.
	(ppc64_elf_merge_symbol_attribute): Merge localentry bits from
	dynamic objects.
	(is_elfv2_localentry0): New function.
	(ppc64_elf_tls_setup): Default params->plt_localentry0.
	(plt_stub_size): Adjust size for tls_get_addr_opt stub.
	(build_tls_get_addr_stub): Use a simpler stub when r2 is not saved.
	(ppc64_elf_size_stubs): Leave stub_type as ppc_stub_plt_call for
	optimized localentry:0 stubs.
	(ppc64_elf_build_stubs): Save r2 in ELFv2 __glink_PLTresolve.
	(ppc64_elf_relocate_section): Leave nop unchanged for optimized
	localentry:0 stubs.
	(ppc64_elf_finish_dynamic_sections): Set PPC64_OPT_LOCALENTRY in
	DT_PPC64_OPT.
	* elf64-ppc.h (struct ppc64_elf_params): Add plt_localentry0.
include/
	* elf/ppc64.h (PPC64_OPT_LOCALENTRY): Define.
ld/
	* emultempl/ppc64elf.em (params): Init plt_localentry0 field.
	(enum ppc64_opt): New, replacing OPTION_* defines.  Add
	OPTION_PLT_LOCALENTRY, and OPTION_NO_PLT_LOCALENTRY.
	(PARSE_AND_LIST_*): Support --plt-localentry and --no-plt-localentry.
	* testsuite/ld-powerpc/elfv2so.d: Update.
	* testsuite/ld-powerpc/powerpc.exp (TLS opt 5): Use --no-plt-localentry.
	* testsuite/ld-powerpc/tlsopt5.d: Update.
2017-06-01 22:47:32 +09:30
..
emulparams Update avrxmega3 linker emulation to support avrxmega2 devices with flash memory visible in the SRAM address range. 2017-05-19 15:06:33 +01:00
emultempl PPC64_OPT_LOCALENTRY 2017-06-01 22:47:32 +09:30
po Add Serbian translation for the LD directory. 2017-01-27 11:27:50 +00:00
scripttempl Update avrxmega3 linker emulation to support avrxmega2 devices with flash memory visible in the SRAM address range. 2017-05-19 15:06:33 +01:00
testsuite PPC64_OPT_LOCALENTRY 2017-06-01 22:47:32 +09:30
.gitignore
aclocal.m4
ChangeLog PPC64_OPT_LOCALENTRY 2017-06-01 22:47:32 +09:30
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 Add Serbian translation for the LD directory. 2017-01-27 11:27:50 +00:00
configure.ac Add Serbian translation for the LD directory. 2017-01-27 11:27:50 +00:00
configure.host
configure.tgt [AArch64, ld] Support ILP32 triplet aarch64*-linux-gnu_ilp32 2017-05-22 13:27:56 +01:00
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 Treat a prefix of "$SYSROOT" in the same way as "=" when parsing linker search paths. 2017-05-18 15:07:59 +01:00
ldbuildid.c
ldbuildid.h
ldcref.c
ldctor.c
ldctor.h
ldemul.c
ldemul.h
ldexp.c
ldexp.h
ldfile.c Treat a prefix of "$SYSROOT" in the same way as "=" when parsing linker search paths. 2017-05-18 15:07:59 +01:00
ldfile.h
ldgram.y
ldint.texinfo
ldlang.c Treat a prefix of "$SYSROOT" in the same way as "=" when parsing linker search paths. 2017-05-18 15:07:59 +01:00
ldlang.h
ldlex-wrapper.c
ldlex.h
ldlex.l Treat a prefix of "$SYSROOT" in the same way as "=" when parsing linker search paths. 2017-05-18 15:07:59 +01:00
ldmain.c Fix buffer overflows in ld when printing translated strings. 2017-01-31 12:07:04 +00:00
ldmain.h
ldmisc.c LD: vfinfo: Make clever formatters consistent WRT function name reporting 2017-02-15 13:41:51 +00:00
ldmisc.h
ldver.c
ldver.h
ldwrite.c
ldwrite.h
lexsup.c
MAINTAINERS
Makefile.am Implement -z dynamic-undefined-weak 2017-04-19 20:39:52 +09:30
Makefile.in Implement -z dynamic-undefined-weak 2017-04-19 20:39:52 +09:30
mri.c
mri.h
NEWS Support ELF SHF_GNU_MBIND and PT_GNU_MBIND_XXX 2017-04-04 09:06:04 -07:00
pe-dll.c Support pe-bigobj-x86-64 as an output format in 64-bit PE based linkers. 2017-05-09 14:42:43 +01:00
pe-dll.h PR 21274, ld segfaults linking PE DLL 2017-04-11 19:49:13 +09:30
pep-dll.c
pep-dll.h PR 21274, ld segfaults linking PE DLL 2017-04-11 19:49:13 +09:30
plugin.c Rename non_ir_ref to non_ir_ref_regular 2017-05-16 10:35:02 +09:30
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) 2012-2017 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.