BFD's bfd_get_mach () function returns a bfd specific value representing
the architecture of the target which is populated from the Tag_CPU_arch
build attribute value of that target. Among other users of that
interfacem, objdump which uses it to print the architecture version of
the binary being examinated and to decide what instruction is available
if run with "-m arm" via its own mapping from bfd_mach_arm_X values to
feature bits available.
However, both BFD and objdump's most recent known architecture is
Armv5TE. When encountering a newer architecture bfd_get_mach will return
bfd_mach_arm_unknown. This is unfortunate since objdump uses that value
to allow all instructions on all architectures which is already what it
does by default, making the "-m arm" trick useless.
This patch updates BFD and objdump's knowledge of Arm architecture
versions up to the latest Armv8-M Baseline and Mainline, Armv8-R and
Armv8.4-A architectures. Since several architecture versions (eg. 8.X-A)
share the same Tag_CPU_arch build attribute value and
bfd_mach_arm values, the mapping from bfd machine value to feature bits
need to return the most featureful feature bits that would yield the
given bfd machine value otherwise some instruction would not disassemble
under "-m arm" mode. The patch rework that mapping to make this clearer
and simplify writing the mapping rules. In particular, for simplicity
all FPU instructions are allowed in all cases.
Finally, the patch also rewrite the cpu_arch_ver table in GAS to use the
TAG_CPU_ARCH_X macros rather than hardcode their value.
2018-07-02 Thomas Preud'homme <thomas.preudhomme@arm.com>
bfd/
* archures.c (bfd_mach_arm_5TEJ, bfd_mach_arm_6, bfd_mach_arm_6KZ,
bfd_mach_arm_6T2, bfd_mach_arm_6K, bfd_mach_arm_7, bfd_mach_arm_6M,
bfd_mach_arm_6SM, bfd_mach_arm_7EM, bfd_mach_arm_8, bfd_mach_arm_8R,
bfd_mach_arm_8M_BASE, bfd_mach_arm_8M_MAIN): Define.
* bfd-in2.h: Regenerate.
* cpu-arm.c (arch_info_struct): Add entries for above new
bfd_mach_arm values.
* elf32-arm.c (bfd_arm_get_mach_from_attributes): Add Tag_CPU_arch to
bfd_mach_arm mapping logic for pre Armv4 and Armv5TEJ and later
architectures. Force assert failure for any new Tag_CPU_arch value.
gas/
* config/tc-arm.c (cpu_arch_ver): Use symbolic TAG_CPU_ARCH macros
rather than hardcode their values.
ld/
* arm-dis.c (select_arm_features): Fix typo in heading comment. Allow
all FPU features and add mapping from new bfd_mach_arm values to
allowed CPU feature bits.
opcodes/
* testsuite/ld-arm/tls-descrelax-be8.d: Add architecture version in
expected result.
* testsuite/ld-arm/tls-descrelax-v7.d: Likewise.
* testsuite/ld-arm/tls-longplt-lib.d: Likewise.
* testsuite/ld-arm/tls-longplt.d: Likewise.
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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.
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.
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