forked from Imagelibrary/binutils-gdb
7d81bc937c
Link-time relaxations of branches are common for MSP430, given that GCC
can generate pessimal branch instructions, and the
-mcode-region=either/-mdata-region=either options to shuffle sections
can further change the type of branch instruction required.
These relaxations can result in invalid code when .uleb128
directives, used in the .gcc_except_table section, are used to calculate
the distance between two labels. A value for the .uleb128 directive is
calculated at assembly-time, and can't be updated at link-time, even if
relaxation causes the distance between the labels to change.
This patch adds relocations for subtract expressions in .uleb128
directives, to allow the linker to re-calculate the value of these
expressions after relaxation has been performed.
bfd/ChangeLog:
* bfd-in2.h (bfd_reloc_code_real): Add
BFD_RELOC_MSP430_{SET,SUB}_ULEB128.
* elf32-msp430.c (msp430_elf_ignore_reloc): New.
(elf_msp430_howto_table): Add R_MSP430{,X}_GNU_{SET,SUB}_ULEB128.
(msp430_reloc_map): Add R_MSP430_GNU_{SET,SUB}_ULEB128.
(msp430x_reloc_map): Add R_MSP430X_GNU_{SET,SUB}_ULEB128.
(write_uleb128): New.
(msp430_final_link_relocate): Handle R_MSP430{,X}_GNU_{SET,SUB}_ULEB128.
* libbfd.c (_bfd_write_unsigned_leb128): New.
* libbfd.h (_bfd_write_unsigned_leb128): New prototype.
Add BFD_RELOC_MSP430_{SET,SUB}_ULEB128.
* reloc.c: Document BFD_RELOC_MSP430_{SET,SUB}_ULEB128.
binutils/ChangeLog:
* readelf.c (target_specific_reloc_handling): Handle
R_MSP430{,X}_GNU_{SET,SUB}_ULEB128.
gas/ChangeLog:
* config/tc-msp430.c (msp430_insert_uleb128_fixes): New.
(msp430_md_end): Call msp430_insert_uleb128_fixes.
include/ChangeLog:
* elf/msp430.h (elf_msp430_reloc_type): Add
R_MSP430_GNU_{SET,SUB}_ULEB128.
(elf_msp430x_reloc_type): Add R_MSP430X_GNU_{SET,SUB}_ULEB128.
ld/ChangeLog:
* testsuite/ld-msp430-elf/msp430-elf.exp: Run new tests.
* testsuite/ld-msp430-elf/uleb128.s: New test.
* testsuite/ld-msp430-elf/uleb128_430.d: New test.
* testsuite/ld-msp430-elf/uleb128_430x.d: New test.
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) 2012-2020 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.