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#! /usr/bin/perl
# Copyright 2000, 2001 Free Software Foundation, Inc.
#
# This file is part of the GNU MP Library.
#
# The GNU MP Library is free software; you can redistribute it and/or modify
# it under the terms of either:
#
# * the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 3 of the License, or (at your
# option) any later version.
#
# or
#
# * the GNU General Public License as published by the Free Software
# Foundation; either version 2 of the License, or (at your option) any
# later version.
#
# or both in parallel, as here.
#
# The GNU MP Library is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
# for more details.
#
# You should have received copies of the GNU General Public License and the
# GNU Lesser General Public License along with the GNU MP Library. If not,
# see https://www.gnu.org/licenses/.
# Usage: cross.pl [filename.o]...
#
# Produce an annotated disassembly of the given object files, indicating
# certain code alignment and addressing mode problems afflicting K6 chips.
# "ZZ" is used on all annotations, so this can be searched for.
#
# With no arguments, all .o files corresponding to .asm files are processed.
# This is good in the mpn object directory of a k6*-*-* build.
#
# Code alignments of 8 bytes or more are handled. When 32 is used, cache
# line boundaries will fall in at offsets 0x20,0x40,etc and problems are
# flagged at those locations. When 16 is used, the line boundaries can also
# fall at offsets 0x10,0x30,0x50,etc, depending where the file is loaded, so
# problems are identified there too. Likewise when 8 byte alignment is used
# problems are flagged additionally at 0x08,0x18,0x28,etc.
#
# Usually 32 byte alignment is used for k6 routines, but less is certainly
# possible if through good luck, or a little tweaking, cache line crossing
# problems can be avoided at the extra locations.
#
# Bugs:
#
# Instructions without mod/rm bytes or which are already vector decoded are
# unaffected by cache line boundary crossing, but not all of these have yet
# been put in as exceptions. All that occur in practice in GMP are present
# though.
#
# There's no messages for using the vector decoded addressing mode (%esi),
# but that's easy to avoid when coding.
#
# Future:
#
# Warn about jump targets that are poorly aligned (less than 2 instructions
# before a cache line boundary).
use strict;
sub disassemble {
my ($file) = @_;
my ($addr,$b1,$b2,$b3, $prefix,$opcode,$modrm);
my $align;
open (IN, "objdump -Srfh $file |")
|| die "Cannot open pipe from objdump\n";
while (<IN>) {
print;
if (/^[ \t]*[0-9]+[ \t]+\.text[ \t]/ && /2\*\*([0-9]+)$/) {
$align = 1 << $1;
if ($align < 8) {
print "ZZ cross.pl cannot handle alignment < 2**3\n";
$align = 8
}
}
if (/^[ \t]*([0-9a-f]*):[ \t]*([0-9a-f]+)[ \t]+([0-9a-f]+)[ \t]+([0-9a-f]+)/) {
($addr,$b1,$b2,$b3) = ($1,$2,$3,$4);
} elsif (/^[ \t]*([0-9a-f]*):[ \t]*([0-9a-f]+)[ \t]+([0-9a-f]+)/) {
($addr,$b1,$b2,$b3) = ($1,$2,$3,'');
} elsif (/^[ \t]*([0-9a-f]*):[ \t]*([0-9a-f]+)/) {
($addr,$b1,$b2,$b3) = ($1,$2,'','');
} else {
next;
}
if ($b1 =~ /0f/) {
$prefix = $b1;
$opcode = $b2;
$modrm = $b3;
} else {
$prefix = '';
$opcode = $b1;
$modrm = $b2;
}
# modrm of the form 00-xxx-100 with an 0F prefix is the problem case
# for K6 and pre-CXT K6-2
if ($prefix =~ /0f/
&& $opcode !~ /^8/ # jcond disp32
&& $modrm =~ /^[0-3][4c]/) {
print "ZZ ($file) >3 bytes to determine instruction length [K6]\n";
}
# with just an opcode, starting 1f mod 20h
if (($align==32 && $addr =~ /[13579bdf]f$/
|| $align==16 && $addr =~ /f$/
|| $align==8 && $addr =~ /[7f]$/)
&& $prefix !~ /0f/
&& $opcode !~ /1[012345]/ # adc
&& $opcode !~ /1[89abcd]/ # sbb
&& $opcode !~ /^4/ # inc/dec reg
&& $opcode !~ /^5/ # push/pop reg
&& $opcode !~ /68/ # push $imm32
&& $opcode !~ /^7/ # jcond disp8
&& $opcode !~ /a[89]/ # test+imm
&& $opcode !~ /a[a-f]/ # stos/lods/scas
&& $opcode !~ /b8/ # movl $imm32,%eax
&& $opcode !~ /d[0123]/ # rcl
&& $opcode !~ /e[0123]/ # loop/loopz/loopnz/jcxz
&& $opcode !~ /e8/ # call disp32
&& $opcode !~ /e[9b]/ # jmp disp32/disp8
&& $opcode !~ /f[89abcd]/ # clc,stc,cli,sti,cld,std
&& !($opcode =~ /f[67]/ # grp 1
&& $modrm =~ /^[2367abef]/) # mul, imul, div, idiv
&& $modrm !~ /^$/) {
print "ZZ ($file) opcode/modrm cross 32-byte boundary\n";
}
# with an 0F prefix, anything starting at 1f mod 20h
if (($align==32 && $addr =~ /[13579bdf][f]$/
|| $align==16 && $addr =~ /f$/
|| $align==8 && $addr =~ /[7f]$/)
&& $prefix =~ /0f/
&& $opcode !~ /af/ # imul
&& $opcode !~ /a[45]/ # shldl
&& $opcode !~ /a[cd]/ # shrdl
) {
print "ZZ ($file) prefix/opcode cross 32-byte boundary\n";
}
# with an 0F prefix, anything with mod/rm starting at 1e mod 20h
if (($align==32 && $addr =~ /[13579bdf][e]$/
|| $align==16 && $addr =~ /[e]$/
|| $align==8 && $addr =~ /[6e]$/)
&& $prefix =~ /0f/
&& $opcode !~ /^8/ # jcond disp32
&& $opcode !~ /af/ # imull reg,reg
&& $opcode !~ /a[45]/ # shldl
&& $opcode !~ /a[cd]/ # shrdl
&& $modrm !~ /^$/) {
print "ZZ ($file) prefix/opcode/modrm cross 32-byte boundary\n";
}
}
close IN || die "Error from objdump (or objdump not available)\n";
}
my @files;
if ($#ARGV >= 0) {
@files = @ARGV;
} else {
@files = glob "*.asm";
map {s/.asm/.o/} @files;
}
foreach (@files) {
disassemble($_);
}
|
