The microMIPS JALX instruction shares the R_MICROMIPS_26_S1 relocation
with microMIPS J/JAL/JALS instructions, however unlike the latters its
encoded immediate argument is unusually shifted left by 2 rather than 1
in calculating the value used for the operation requested.
We already handle this exception in `mips_elf_calculate_relocation' in
LD, in a scenario where JALX is produced as a result of relaxing JAL for
the purpose of making a cross-mode jump. We also get it right in the
disassembler in `decode_micromips_operand'.
What we don't correctly do however is processing microMIPS JALX produced
by GAS from an assembly source, where a non-zero constant argument or a
symbol reference with a non-zero in-place addend has been used. In this
case the same calculation is made as for microMIPS J/JAL/JALS, causing
the wrong encoding to be produced by GAS on making an object file, and
then again by LD in the final link. The latter in particular causes the
calculation, where the addend fits in the relocatable field, to produce
different final addresses for the same source code depending on whether
REL or RELA relocations are used.
Correct these issues by special-casing microMIPS JALX in the places that
have been previously missed.
bfd/
* elfxx-mips.c (mips_elf_read_rel_addend): Adjust the addend for
microMIPS JALX.
gas/
* config/tc-mips.c (append_insn): Correct the encoding of a
constant argument for microMIPS JALX.
(tc_gen_reloc): Correct the encoding of an in-place addend for
microMIPS JALX.
* testsuite/gas/mips/jalx-addend.d: New test.
* testsuite/gas/mips/jalx-addend-n32.d: New test.
* testsuite/gas/mips/jalx-addend-n64.d: New test.
* testsuite/gas/mips/jalx-imm.d: New test.
* testsuite/gas/mips/jalx-imm-n32.d: New test.
* testsuite/gas/mips/jalx-imm-n64.d: New test.
* testsuite/gas/mips/jalx-addend.s: New test source.
* testsuite/gas/mips/jalx-imm.s: New test source.
* testsuite/gas/mips/mips.exp: Run the new tests.
ld/
* testsuite/ld-mips-elf/jalx-addend.d: New test.
* testsuite/ld-mips-elf/jalx-addend-n32.d: New test.
* testsuite/ld-mips-elf/jalx-addend-n64.d: New test.
* testsuite/ld-mips-elf/mips-elf.exp: Run the new tests.
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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) 2012-2016 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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