binutils-gdb/ld
Palmer Dabbelt ff6f4d9b2d RISC-V: Add R_RISCV_DELETE, which marks bytes for deletion
We currently delete bytes by shifting an entire BFD backwards to
overwrite the bytes we no longer need.  The result is that relaxing a
BFD is quadratic time.

This patch adds an additional relocation that specifies a byte range
that will be deleted from the final object file, and adds a relaxation
pass (between the existing passes that delete bytes and the alignment
pass) that actually deletes the bytes.  Note that deletion is still
quadratic time, and nothing uses R_RISCV_DELETE yet.

I've been meaning to go convert all the other relaxations to use
R_RISCV_DELETE and then make it faster, but this patch has been sitting
around for months so it looks like that won't happen for a bit.  The
PCREL->GPREL relaxation that comes next uses this, and since we've been
using these two patches out of tree since I wrote them months ago I
figure it's better to just get them in now.  I (or someone else :)) can
convert all the relocations later...

R_RISCV_DELETE will never be emitted into ELF objects, so therefor isn't
exposed to the rest of binutils.  As such, we're not considering this as
part of the ABI.

bfd/ChangeLog

2017-10-19  Palmer Dabbelt  <palmer@dabbelt.com>

        * elfnn-riscv (R_RISCV_DELETE): New define.
        (_bfd_riscv_relax_delete): New function.
        (perform_relocation): Handle R_RISCV_DELETE.
        (_bfd_riscv_relax_section): Likewise.

ld/ChangeLog

2017-10-19  Palmer Dabbelt  <palmer@dabbelt.com>

        * emultempl/riscvelf.em (riscv_elf_before_allocation): Add a
        third relaxation pass.
2017-10-19 09:19:32 -07:00
..
emulparams ELF: Call check_relocs after opening all inputs 2017-10-16 03:50:13 -07:00
emultempl RISC-V: Add R_RISCV_DELETE, which marks bytes for deletion 2017-10-19 09:19:32 -07:00
po ld whitespace fixes 2017-10-12 23:30:43 +10:30
scripttempl ld whitespace fixes 2017-10-12 23:30:43 +10:30
testsuite ELF: Call check_relocs after opening all inputs 2017-10-16 03:50:13 -07:00
.gitignore
aclocal.m4
ChangeLog RISC-V: Add R_RISCV_DELETE, which marks bytes for deletion 2017-10-19 09:19:32 -07:00
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-9197
ChangeLog-9899
config.in
configure ld whitespace fixes 2017-10-12 23:30:43 +10:30
configure.ac ld whitespace fixes 2017-10-12 23:30:43 +10:30
configure.host
configure.tgt ld whitespace fixes 2017-10-12 23:30:43 +10:30
deffile.h
deffilep.y ld whitespace fixes 2017-10-12 23:30:43 +10:30
dep-in.sed
elf-hints-local.h
fdl.texi
gen-doc.texi
genscrba.sh
genscripts.sh ld whitespace fixes 2017-10-12 23:30:43 +10:30
h8-doc.texi
ld.h
ld.texinfo Correct -z text and other -z documentation 2017-10-17 16:47:05 +10:30
ldbuildid.c
ldbuildid.h
ldcref.c ld internationalization fixes 2017-10-11 15:04:59 +10:30
ldctor.c
ldctor.h
ldemul.c ELF: Call check_relocs after opening all inputs 2017-10-16 03:50:13 -07:00
ldemul.h ELF: Call check_relocs after opening all inputs 2017-10-16 03:50:13 -07:00
ldexp.c
ldexp.h
ldfile.c
ldfile.h
ldgram.y ld whitespace fixes 2017-10-12 23:30:43 +10:30
ldint.texinfo
ldlang.c ELF: Call check_relocs after opening all inputs 2017-10-16 03:50:13 -07:00
ldlang.h
ldlex-wrapper.c
ldlex.h
ldlex.l ld whitespace fixes 2017-10-12 23:30:43 +10:30
ldmain.c ld internationalization fixes 2017-10-11 15:04:59 +10:30
ldmain.h
ldmisc.c
ldmisc.h
ldver.c
ldver.h
ldwrite.c
ldwrite.h
lexsup.c ld whitespace fixes 2017-10-12 23:30:43 +10:30
MAINTAINERS
Makefile.am Correct ld/Makefile earmelfb_fuchsia dependencies 2017-10-10 14:44:58 +10:30
Makefile.in Correct ld/Makefile earmelfb_fuchsia dependencies 2017-10-10 14:44:58 +10:30
mri.c
mri.h
NEWS ld whitespace fixes 2017-10-12 23:30:43 +10:30
pe-dll.c ld whitespace fixes 2017-10-12 23:30:43 +10:30
pe-dll.h
pep-dll.c
pep-dll.h
plugin.c ld whitespace fixes 2017-10-12 23:30:43 +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) 2012-2017 Free Software Foundation, Inc.

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