H.J. Lu 0a59decbb8 elf: Add PT_GNU_PROPERTY segment type
Linkers group input note sections with the same name into one output
note section with the same name.  One output note section is placed in
one PT_NOTE segment.  New linkers merge all input .note.gnu.property
sections into one output .note.gnu.property section with a single
NT_GNU_PROPERTY_TYPE_0 note in a single PT_NOTE segment.  Since older
linkers treat input .note.gnu.property section as a generic note section
and just concatenate all input .note.gnu.property sections into one
output .note.gnu.property section without merging them, we may
see one or more NT_GNU_PROPERTY_TYPE_0 notes in PT_NOTE segment, which
are invalid.

GNU_PROPERTY_X86_UINT32_VALID was defined to address this issue such
that linker sets the bit for non-relocatable outputs.  But it isn't
sufficient:

1. It doesn't cover generic properties.
2. When -mx86-used-note=yes is passed to x86 assembler, the
GNU_PROPERTY_X86_UINT32_VALID bit is set in GNU_PROPERTY_X86_ISA_1_USED
property in object file and older linkers generate invalid
NT_GNU_PROPERTY_TYPE_0 notes with the GNU_PROPERTY_X86_UINT32_VALID bit
set.

I am proposing the following changes:

1. Add PT_GNU_PROPERTY segment type:

 # define PT_GNU_PROPERTY (PT_LOOS + 0x474e553)

which covers .note.gnu.property section.
2. Remove GNU_PROPERTY_X86_UINT32_VALID.

bfd/

	PR ld/23900
	* elf.c (get_program_header_size): Add a PT_GNU_PROPERTY
	segment for NOTE_GNU_PROPERTY_SECTION_NAME.
	(_bfd_elf_map_sections_to_segments): Create a PT_GNU_PROPERTY
	segment for NOTE_GNU_PROPERTY_SECTION_NAME.
	* elfxx-x86.c (_bfd_elf_link_setup_gnu_properties): Don't set
	GNU_PROPERTY_X86_UINT32_VALID.

binutils/

	PR ld/23900
	* readelf.c (get_segment_type): Support PT_GNU_PROPERTY.
	(decode_x86_isa): Don't check GNU_PROPERTY_X86_UINT32_VALID.
	(decode_x86_feature_1): Likewise.
	(decode_x86_feature_2): Likewise.
	(print_gnu_property_note): Remove GNU_PROPERTY_X86_UINT32_VALID
	check.
	* testsuite/binutils-all/i386/empty.d: Updated.
	* testsuite/binutils-all/x86-64/empty-x32.d: Likewise.
	* testsuite/binutils-all/x86-64/empty.d: Likewise.
	* testsuite/binutils-all/i386/pr21231b.s: Change
	GNU_PROPERTY_X86_ISA_1_USED bits to 0x7fffffff.
	* testsuite/binutils-all/x86-64/pr21231b.s: Likewise.

gas/

	PR ld/23900
	* config/tc-i386.c (x86_cleanup): Don't set
	GNU_PROPERTY_X86_UINT32_VALID.
	* testsuite/gas/i386/property-1.s: Change
	GNU_PROPERTY_X86_ISA_1_USED bits to 0.

include/

	PR ld/23900
	* elf/common.h (PT_GNU_PROPERTY): New.
	(GNU_PROPERTY_X86_UINT32_VALID): Removed.

ld/

	PR ld/23900
	* testsuite/ld-elf/elf.exp: Run PR ld/23900 test.
	* testsuite/ld-elf/pr23900-1-32.rd: New file.
	* testsuite/ld-elf/pr23900-1-64.rd: Likewise.
	* testsuite/ld-elf/pr23900-1.d: Likewise.
	* testsuite/ld-elf/pr23900-1.s: Likewise.
	* testsuite/ld-elf/pr23900-2.s: Likewise.
	* testsuite/ld-elf/pr23900-2a.d: Likewise.
	* testsuite/ld-elf/pr23900-2b.d: Likewise.
	* testsuite/ld-i386/ibt-plt-1.d: Adjusted.
	* testsuite/ld-i386/ibt-plt-2c.d: Likewise.
	* testsuite/ld-i386/ibt-plt-2d.d: Likewise.
	* testsuite/ld-i386/ibt-plt-3d.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-1-x32.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-1.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-2c-x32.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-2c.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-2d-x32.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-2c.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-3c-x32.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-3c.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-3d-x32.d: Likewise.
	* testsuite/ld-x86-64/ibt-plt-3d.d: Likewise.
	* testsuite/ld-i386/pr23372c.d: Expect <None>
	for GNU_PROPERTY_X86_ISA_1_USED.
	* testsuite/ld-x86-64/pr23372c-x32.d: Likewise.
	* testsuite/ld-x86-64/pr23372c.d: Likewise.
	* testsuite/ld-x86-64/pr23372d-x32.d: Likewise.
	* testsuite/ld-x86-64/pr23372d.d: Likewise.
	* testsuite/ld-x86-64/property-x86-5a.s: Change
	GNU_PROPERTY_X86_ISA_1_USED bits to 0.
	* testsuite/ld-x86-64/property-x86-5b.s: Likewise.
2018-12-14 04:55:34 -08:00
..
2018-04-17 14:47:13 -07:00
2018-10-29 17:50:40 +10:30
2018-10-29 17:50:40 +10:30
2018-04-16 20:29:05 +09:30

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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.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) 2012-2018 Free Software Foundation, Inc.

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