Don't convert PC-relative REL relocations against absolute symbols to
section-relative references and retain the original symbol reference
instead. Offsets into the absolute section may overflow the limited
range of their in-place addend field, causing an assembly error, e.g.:
$ cat test.s
.text
.globl foo
.ent foo
foo:
b bar
.end foo
.set bar, 0x12345678
$ as -EB -32 -o test.o test.s
test.s: Assembler messages:
test.s:3: Error: relocation overflow
$
With the original reference retained the source can now be assembled and
linked successfully:
$ as -EB -32 -o test.o test.s
$ objdump -dr test.o
test.o: file format elf32-tradbigmips
Disassembly of section .text:
00000000 <foo>:
0: 1000ffff b 0 <foo>
0: R_MIPS_PC16 bar
4: 00000000 nop
...
$ ld -melf32btsmip -Ttext 0x12340000 -e foo -o test test.o
$ objdump -dr test
test: file format elf32-tradbigmips
Disassembly of section .text:
12340000 <foo>:
12340000: 1000159d b 12345678 <bar>
12340004: 00000000 nop
...
$
For simplicity always retain the original symbol reference, even if it
would indeed fit.
Making TC_FORCE_RELOCATION_ABS separate from TC_FORCE_RELOCATION causes
R_MICROMIPS_PC7_S1, R_MICROMIPS_PC10_S1 and R_MICROMIPS_PC16_S1 branch
relocations against absolute symbols to be converted on RELA targets to
section-relative references. This is an intended effect of this change.
Absolute symbols carry no ISA annotation in their `st_other' field and
their value is not going to change with linker relaxation, so it is safe
to discard the original reference and keep the calculated final symbol
value only in the relocation's addend.
Similarly R6 R_MIPS_PCHI16 and R_MIPS_PCLO16 relocations referring
absolute symbols can be safely converted even on REL targets, as there
the in-place addend of these relocations covers the entire 32-bit
address space so it can hold the calculated final symbol value, and
likewise the value referred won't be affected by any linker relaxation.
Add a set of suitable test cases and enable REL linker tests which now
work and were previously used as dump patterns for RELA tests only.
gas/
* config/tc-mips.h (TC_FORCE_RELOCATION_ABS): New macro.
(mips_force_relocation_abs): New prototype.
* config/tc-mips.c (mips_force_relocation_abs): New function.
* testsuite/gas/mips/branch-absolute.d: Adjust dump patterns.
* testsuite/gas/mips/mips16-branch-absolute.d: Likewise.
* testsuite/gas/mips/micromips-branch-absolute-n32.d: Likewise.
* testsuite/gas/mips/micromips-branch-absolute-n64.d: Likewise.
* testsuite/gas/mips/micromips-branch-absolute-addend-n32.d:
Likewise.
* testsuite/gas/mips/micromips-branch-absolute-addend-n64.d:
Likewise.
* testsuite/gas/mips/branch-absolute-addend.d: New test.
* testsuite/gas/mips/mips16-branch-absolute-addend.d: New test.
* testsuite/gas/mips/micromips-branch-absolute-addend.d: New
test.
* testsuite/gas/mips/mips.exp: Run the new tests.
ld/
* testsuite/ld-mips-elf/mips-elf.exp: Run
`branch-absolute-addend', `mips16-branch-absolute',
`mips16-branch-absolute-addend' and
`micromips-branch-absolute-addend'.
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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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