9d862524f6
Verify that the ISA mode of branch targets is the same as the referring relocation, so that an attempt to produce a branch between instructions encoded in different ISA modes each causes an error rather than silently producing non-functional code. Make sure that no symbol or addend bits are silently truncated: terminate with an error if the relocation value calculated cannot be encoded in the relocatable field of a branch; for REL targets also applying to any intermediate addend. Also make jump target's alignment verification consistent with that for branches. This change will require an update to some obscure handcoded assembly sources which make branches to labels placed at data objects, however for microMIPS code only. These labels will have to be updated with the `.insn' directive for containing code to assemble and link successfully. Such code is broken as any such labels have always been required by the microMIPS architecture specification[1][2] to be annotated this way for correct interpretation, and with our old code missing `.insn' directives caused labels to present different semantics depending on whether they were referred with branch (ISA bit ignored) or other relocations (ISA bit respected). Enforcing these checks however will ensure errors in building software, like mixed regular MIPS and microMIPS code links with branches between, will be diagnosed at the build time rather than causing odd run-time errors such as intermittent crashes. It will also let cross-mode BAL instructions be converted to JALX instructions, with a separate change. References: [1] "MIPS Architecture for Programmers, Volume II-B: The microMIPS32 Instruction Set", MIPS Technologies, Inc., Document Number: MD00582, Revision 5.04, January 15, 2014, Section 7.1 "Assembly-Level Compatibility", p. 533 [2] "MIPS Architecture for Programmers, Volume II-B: The microMIPS64 Instruction Set", MIPS Technologies, Inc., Document Number: MD00594, Revision 5.04, January 15, 2014, Section 8.1 "Assembly-Level Compatibility", p. 623 bfd/ * elfxx-mips.c (b_reloc_p): Add R_MICROMIPS_PC16_S1, R_MICROMIPS_PC10_S1 and R_MICROMIPS_PC7_S1. (branch_reloc_p): New function. (mips_elf_calculate_relocation): Handle ISA mode determination for relocations against section symbols, against absolute symbols and absolute relocations. Also set `*cross_mode_jump_p' for branches. <R_MIPS16_26, R_MIPS_26, R_MICROMIPS_26_S1>: Suppress alignment checks for weak undefined symbols. Also check target alignment within the same ISA mode. <R_MIPS_PC16, R_MIPS_GNU_REL16_S2>: Handle cross-mode branches in the alignment check. <R_MICROMIPS_PC7_S1>: Add an alignment check. <R_MICROMIPS_PC10_S1>: Likewise. <R_MICROMIPS_PC16_S1>: Likewise. (mips_elf_perform_relocation): Report a failure for unsupported same-mode JALX instructions and cross-mode branches. (_bfd_mips_elf_relocate_section) <bfd_reloc_outofrange>: Add error messages for jumps to misaligned addresses. gas/ * config/tc-mips.c (mips_force_relocation): Also retain branch relocations against MIPS16 and microMIPS symbols. (fix_bad_cross_mode_jump_p): New function. (fix_bad_same_mode_jalx_p): Likewise. (fix_bad_misaligned_jump_p): Likewise. (fix_bad_cross_mode_branch_p): Likewise. (fix_bad_misaligned_branch_p): Likewise. (fix_validate_branch): Likewise. (md_apply_fix) <BFD_RELOC_MIPS_JMP, BFD_RELOC_MIPS16_JMP> <BFD_RELOC_MICROMIPS_JMP>: Separate from BFD_RELOC_MIPS_SHIFT5, etc. Verify the ISA mode and alignment of the jump target. <BFD_RELOC_MIPS_21_PCREL_S2>: Replace the inline alignment check with a call to `fix_validate_branch'. <BFD_RELOC_MIPS_26_PCREL_S2>: Likewise. <BFD_RELOC_16_PCREL_S2>: Likewise. <BFD_RELOC_MICROMIPS_7_PCREL_S1, BFD_RELOC_MICROMIPS_10_PCREL_S1> <BFD_RELOC_MICROMIPS_16_PCREL_S1>: Retain the original addend. Verify the ISA mode and alignment of the branch target. (md_convert_frag): Verify the ISA mode and alignment of resolved MIPS16 branch targets. * testsuite/gas/mips/branch-misc-1.s: Annotate non-instruction branch targets with `.insn'. * testsuite/gas/mips/branch-misc-5.s: Likewise. * testsuite/gas/mips/micromips@branch-misc-5-64.d: Update accordingly. * testsuite/gas/mips/micromips@branch-misc-5pic-64.d: Likewise. * testsuite/gas/mips/micromips-branch-relax.s: Annotate non-instruction branch target with `.insn'. * testsuite/gas/mips/micromips.s: Replace microMIPS JALX targets with external symbols. * testsuite/gas/mips/micromips-insn32.d: Update accordingly. * testsuite/gas/mips/micromips-noinsn32.d: Likewise. * testsuite/gas/mips/micromips-trap.d: Likewise. * testsuite/gas/mips/micromips.d: Likewise. * testsuite/gas/mips/mips16.s: Annotate non-instruction branch targets with `.insn'. * testsuite/gas/mips/mips16.d: Update accordingly. * testsuite/gas/mips/mips16-64.d: Likewise. * testsuite/gas/mips/mips16-dwarf2.s: Annotate non-instruction branch target with `.insn'. * testsuite/gas/mips/relax-swap3.s: Likewise. * testsuite/gas/mips/branch-local-2.l: New list test. * testsuite/gas/mips/branch-local-3.l: New list test. * testsuite/gas/mips/branch-local-n32-2.l: New list test. * testsuite/gas/mips/branch-local-n32-3.l: New list test. * testsuite/gas/mips/branch-local-n64-2.l: New list test. * testsuite/gas/mips/branch-local-n64-3.l: New list test. * testsuite/gas/mips/unaligned-jump-1.l: New list test. * testsuite/gas/mips/unaligned-jump-2.l: New list test. * testsuite/gas/mips/unaligned-jump-3.d: New test. * testsuite/gas/mips/unaligned-jump-mips16-1.l: New list test. * testsuite/gas/mips/unaligned-jump-mips16-2.l: New list test. * testsuite/gas/mips/unaligned-jump-mips16-3.d: New test. * testsuite/gas/mips/unaligned-jump-micromips-1.l: New list test. * testsuite/gas/mips/unaligned-jump-micromips-2.l: New list test. * testsuite/gas/mips/unaligned-jump-micromips-3.d: New test. * testsuite/gas/mips/unaligned-branch-1.l: New list test. * testsuite/gas/mips/unaligned-branch-2.l: New list test. * testsuite/gas/mips/unaligned-branch-3.d: New test. * testsuite/gas/mips/unaligned-branch-r6-1.l: New list test. * testsuite/gas/mips/unaligned-branch-r6-2.l: New list test. * testsuite/gas/mips/unaligned-branch-r6-3.l: New list test. * testsuite/gas/mips/unaligned-branch-r6-4.l: New list test. * testsuite/gas/mips/unaligned-branch-r6-5.d: New test. * testsuite/gas/mips/unaligned-branch-r6-6.d: New test. * testsuite/gas/mips/unaligned-branch-mips16-1.l: New list test. * testsuite/gas/mips/unaligned-branch-mips16-2.l: New list test. * testsuite/gas/mips/unaligned-branch-mips16-3.d: New test. * testsuite/gas/mips/unaligned-branch-micromips-1.l: New list test. * testsuite/gas/mips/unaligned-branch-micromips-2.l: New list test. * testsuite/gas/mips/unaligned-branch-micromips-3.d: New test. * testsuite/gas/mips/branch-local-2.s: New test source. * testsuite/gas/mips/branch-local-3.s: New test source. * testsuite/gas/mips/branch-local-n32-2.s: New test source. * testsuite/gas/mips/branch-local-n32-3.s: New test source. * testsuite/gas/mips/branch-local-n64-2.s: New test source. * testsuite/gas/mips/branch-local-n64-3.s: New test source. * testsuite/gas/mips/unaligned-jump-1.s: New test source. * testsuite/gas/mips/unaligned-jump-2.s: New test source. * testsuite/gas/mips/unaligned-jump-mips16-1.s: New test source. * testsuite/gas/mips/unaligned-jump-mips16-2.s: New test source. * testsuite/gas/mips/unaligned-jump-micromips-1.s: New test source. * testsuite/gas/mips/unaligned-jump-micromips-2.s: New test source. * testsuite/gas/mips/unaligned-branch-1.s: New test source. * testsuite/gas/mips/unaligned-branch-2.s: New test source. * testsuite/gas/mips/unaligned-branch-r6-1.s: New test source. * testsuite/gas/mips/unaligned-branch-r6-2.s: New test source. * testsuite/gas/mips/unaligned-branch-r6-3.s: New test source. * testsuite/gas/mips/unaligned-branch-r6-4.s: New test source. * testsuite/gas/mips/unaligned-branch-mips16-1.s: New test source. * testsuite/gas/mips/unaligned-branch-mips16-2.s: New test source. * testsuite/gas/mips/unaligned-branch-micromips-1.s: New test source. * testsuite/gas/mips/unaligned-branch-micromips-2.s: New test source. * testsuite/gas/mips/mips.exp: Run the new tests. ld/ * testsuite/ld-mips-elf/unaligned-jalx-1.d: Update error message expected. * testsuite/ld-mips-elf/unaligned-jalx-addend-1.d: Likewise. * testsuite/ld-mips-elf/unaligned-jalx-addend-mips16-1.d: Likewise. * testsuite/ld-mips-elf/unaligned-jalx-addend-micromips-1.d: Likewise. * testsuite/ld-mips-elf/unaligned-jalx-mips16-1.d: Likewise. * testsuite/ld-mips-elf/unaligned-jalx-micromips-1.d: Likewise. * testsuite/ld-mips-elf/undefweak-overflow.s: Add jumps, microMIPS BAL and MIPS16 instructions. * testsuite/ld-mips-elf/undefweak-overflow.d: Update accordingly. * testsuite/ld-mips-elf/unaligned-branch-2.d: New test. * testsuite/ld-mips-elf/unaligned-branch-r6-1.d: New test. * testsuite/ld-mips-elf/unaligned-branch-r6-2.d: New test. * testsuite/ld-mips-elf/unaligned-branch-mips16.d: New test. * testsuite/ld-mips-elf/unaligned-branch-micromips.d: New test. * testsuite/ld-mips-elf/unaligned-jump-mips16.d: New test. * testsuite/ld-mips-elf/unaligned-jump-micromips.d: New test. * testsuite/ld-mips-elf/unaligned-jump.d: New test. * testsuite/ld-mips-elf/mips-elf.exp: Run the new tests. |
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.. | ||
config | ||
doc | ||
po | ||
testsuite | ||
.gitignore | ||
acinclude.m4 | ||
aclocal.m4 | ||
app.c | ||
as.c | ||
as.h | ||
asintl.h | ||
atof-generic.c | ||
bignum.h | ||
bit_fix.h | ||
cgen.c | ||
cgen.h | ||
ChangeLog | ||
ChangeLog-0001 | ||
ChangeLog-0203 | ||
ChangeLog-2004 | ||
ChangeLog-2005 | ||
ChangeLog-2006 | ||
ChangeLog-2007 | ||
ChangeLog-2008 | ||
ChangeLog-2009 | ||
ChangeLog-2010 | ||
ChangeLog-2011 | ||
ChangeLog-2012 | ||
ChangeLog-2013 | ||
ChangeLog-2014 | ||
ChangeLog-2015 | ||
ChangeLog-9295 | ||
ChangeLog-9697 | ||
ChangeLog-9899 | ||
compress-debug.c | ||
compress-debug.h | ||
cond.c | ||
config.in | ||
configure | ||
configure.ac | ||
configure.com | ||
configure.tgt | ||
CONTRIBUTORS | ||
COPYING | ||
debug.c | ||
dep-in.sed | ||
depend.c | ||
dw2gencfi.c | ||
dw2gencfi.h | ||
dwarf2dbg.c | ||
dwarf2dbg.h | ||
ecoff.c | ||
ecoff.h | ||
ehopt.c | ||
emul-target.h | ||
emul.h | ||
expr.c | ||
expr.h | ||
flonum-copy.c | ||
flonum-konst.c | ||
flonum-mult.c | ||
flonum.h | ||
frags.c | ||
frags.h | ||
gdbinit.in | ||
hash.c | ||
hash.h | ||
input-file.c | ||
input-file.h | ||
input-scrub.c | ||
itbl-lex-wrapper.c | ||
itbl-lex.h | ||
itbl-lex.l | ||
itbl-ops.c | ||
itbl-ops.h | ||
itbl-parse.y | ||
listing.c | ||
listing.h | ||
literal.c | ||
macro.c | ||
macro.h | ||
MAINTAINERS | ||
Makefile.am | ||
Makefile.in | ||
makefile.vms | ||
messages.c | ||
NEWS | ||
obj.h | ||
output-file.c | ||
output-file.h | ||
read.c | ||
read.h | ||
README | ||
remap.c | ||
sb.c | ||
sb.h | ||
stabs.c | ||
stamp-h.in | ||
struc-symbol.h | ||
subsegs.c | ||
subsegs.h | ||
symbols.c | ||
symbols.h | ||
tc.h | ||
write.c | ||
write.h |
README for GAS
A number of things have changed since version 1 and the wonderful
world of gas looks very different. There's still a lot of irrelevant
garbage lying around that will be cleaned up in time. Documentation
is scarce, as are logs of the changes made since the last gas release.
My apologies, and I'll try to get something useful.
Unpacking and Installation - Summary
====================================
See ../binutils/README.
To build just the assembler, make the target all-gas.
Documentation
=============
The GAS release includes texinfo source for its manual, which can be processed
into `info' or `dvi' forms.
The DVI form is suitable for printing or displaying; the commands for doing
this vary from system to system. On many systems, `lpr -d' will print a DVI
file. On others, you may need to run a program such as `dvips' to convert the
DVI file into a form your system can print.
If you wish to build the DVI file, you will need to have TeX installed on your
system. You can rebuild it by typing:
cd gas/doc
make as.dvi
The Info form is viewable with the GNU Emacs `info' subsystem, or the
stand-alone `info' program, available as part of the GNU Texinfo distribution.
To build the info files, you will need the `makeinfo' program. Type:
cd gas/doc
make info
Specifying names for hosts and targets
======================================
The specifications used for hosts and targets in the `configure'
script are based on a three-part naming scheme, but some short
predefined aliases are also supported. The full naming scheme encodes
three pieces of information in the following pattern:
ARCHITECTURE-VENDOR-OS
For example, you can use the alias `sun4' as a HOST argument or in a
`--target=TARGET' option. The equivalent full name is
`sparc-sun-sunos4'.
The `configure' script accompanying GAS does not provide any query
facility to list all supported host and target names or aliases.
`configure' calls the Bourne shell script `config.sub' to map
abbreviations to full names; you can read the script, if you wish, or
you can use it to test your guesses on abbreviations--for example:
% sh config.sub i386v
i386-unknown-sysv
% sh config.sub i786v
Invalid configuration `i786v': machine `i786v' not recognized
`configure' options
===================
Here is a summary of the `configure' options and arguments that are
most often useful for building GAS. `configure' also has several other
options not listed here.
configure [--help]
[--prefix=DIR]
[--srcdir=PATH]
[--host=HOST]
[--target=TARGET]
[--with-OPTION]
[--enable-OPTION]
You may introduce options with a single `-' rather than `--' if you
prefer; but you may abbreviate option names if you use `--'.
`--help'
Print a summary of the options to `configure', and exit.
`-prefix=DIR'
Configure the source to install programs and files under directory
`DIR'.
`--srcdir=PATH'
Look for the package's source code in directory DIR. Usually
`configure' can determine that directory automatically.
`--host=HOST'
Configure GAS to run on the specified HOST. Normally the
configure script can figure this out automatically.
There is no convenient way to generate a list of all available
hosts.
`--target=TARGET'
Configure GAS for cross-assembling programs for the specified
TARGET. Without this option, GAS is configured to assemble .o files
that run on the same machine (HOST) as GAS itself.
There is no convenient way to generate a list of all available
targets.
`--enable-OPTION'
These flags tell the program or library being configured to
configure itself differently from the default for the specified
host/target combination. See below for a list of `--enable'
options recognized in the gas distribution.
`configure' accepts other options, for compatibility with configuring
other GNU tools recursively; but these are the only options that affect
GAS or its supporting libraries.
The `--enable' options recognized by software in the gas distribution are:
`--enable-targets=...'
This causes one or more specified configurations to be added to those for
which BFD support is compiled. Currently gas cannot use any format other
than its compiled-in default, so this option is not very useful.
`--enable-bfd-assembler'
This causes the assembler to use the new code being merged into it to use
BFD data structures internally, and use BFD for writing object files.
For most targets, this isn't supported yet. For most targets where it has
been done, it's already the default. So generally you won't need to use
this option.
Compiler Support Hacks
======================
On a few targets, the assembler has been modified to support a feature
that is potentially useful when assembling compiler output, but which
may confuse assembly language programmers. If assembler encounters a
.word pseudo-op of the form symbol1-symbol2 (the difference of two
symbols), and the difference of those two symbols will not fit in 16
bits, the assembler will create a branch around a long jump to
symbol1, and insert this into the output directly before the next
label: The .word will (instead of containing garbage, or giving an
error message) contain (the address of the long jump)-symbol2. This
allows the assembler to assemble jump tables that jump to locations
very far away into code that works properly. If the next label is
more than 32K away from the .word, you lose (silently); RMS claims
this will never happen. If the -K option is given, you will get a
warning message when this happens.
REPORTING BUGS IN GAS
=====================
Bugs in gas should be reported to:
bug-binutils@gnu.org.
They may be cross-posted to gcc-bugs@gnu.org if they affect the use of
gas with gcc. They should not be reported just to gcc-bugs, since not
all of the maintainers read that list.
See ../binutils/README for what we need in a bug report.
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.