crypto/perlasm/x86_64-xlate.pl

   1 #! /usr/bin/env perl
   2 # Copyright 2005-2016 The OpenSSL Project Authors. All Rights Reserved.
   3 #
   4 # Licensed under the OpenSSL license (the "License").  You may not use
   5 # this file except in compliance with the License.  You can obtain a copy
   6 # in the file LICENSE in the source distribution or at
   7 # https://www.openssl.org/source/license.html
   8
   9
  10 # Ascetic x86_64 AT&T to MASM/NASM assembler translator by <appro>.
  11 #
  12 # Why AT&T to MASM and not vice versa? Several reasons. Because AT&T
  13 # format is way easier to parse. Because it's simpler to "gear" from
  14 # Unix ABI to Windows one [see cross-reference "card" at the end of
  15 # file]. Because Linux targets were available first...
  16 #
  17 # In addition the script also "distills" code suitable for GNU
  18 # assembler, so that it can be compiled with more rigid assemblers,
  19 # such as Solaris /usr/ccs/bin/as.
  20 #
  21 # This translator is not designed to convert *arbitrary* assembler
  22 # code from AT&T format to MASM one. It's designed to convert just
  23 # enough to provide for dual-ABI OpenSSL modules development...
  24 # There *are* limitations and you might have to modify your assembler
  25 # code or this script to achieve the desired result...
  26 #
  27 # Currently recognized limitations:
  28 #
  29 # - can't use multiple ops per line;
  30 #
  31 # Dual-ABI styling rules.
  32 #
  33 # 1. Adhere to Unix register and stack layout [see cross-reference
  34 #    ABI "card" at the end for explanation].
  35 # 2. Forget about "red zone," stick to more traditional blended
  36 #    stack frame allocation. If volatile storage is actually required
  37 #    that is. If not, just leave the stack as is.
  38 # 3. Functions tagged with ".type name,@function" get crafted with
  39 #    unified Win64 prologue and epilogue automatically. If you want
  40 #    to take care of ABI differences yourself, tag functions as
  41 #    ".type name,@abi-omnipotent" instead.
  42 # 4. To optimize the Win64 prologue you can specify number of input
  43 #    arguments as ".type name,@function,N." Keep in mind that if N is
  44 #    larger than 6, then you *have to* write "abi-omnipotent" code,
  45 #    because >6 cases can't be addressed with unified prologue.
  46 # 5. Name local labels as .L*, do *not* use dynamic labels such as 1:
  47 #    (sorry about latter).
  48 # 6. Don't use [or hand-code with .byte] "rep ret." "ret" mnemonic is
  49 #    required to identify the spots, where to inject Win64 epilogue!
  50 #    But on the pros, it's then prefixed with rep automatically:-)
  51 # 7. Stick to explicit ip-relative addressing. If you have to use
  52 #    GOTPCREL addressing, stick to mov symbol@GOTPCREL(%rip),%r??.
  53 #    Both are recognized and translated to proper Win64 addressing
  54 #    modes. To support legacy code a synthetic directive, .picmeup,
  55 #    is implemented. It puts address of the *next* instruction into
  56 #    target register, e.g.:
  57 #
  58 #               .picmeup        %rax
  59 #               lea             .Label-.(%rax),%rax
  60 #
  61 # 8. In order to provide for structured exception handling unified
  62 #    Win64 prologue copies %rsp value to %rax. For further details
  63 #    see SEH paragraph at the end.
  64 # 9. .init segment is allowed to contain calls to functions only.
  65 # a. If function accepts more than 4 arguments *and* >4th argument
  66 #    is declared as non 64-bit value, do clear its upper part.
  67 \f
  68
  69 use strict;
  70
  71 my $flavour = shift;
  72 my $output  = shift;
  73 if ($flavour =~ /\./) { $output = $flavour; undef $flavour; }
  74
  75 open STDOUT,">$output" || die "can't open $output: $!"
  76         if (defined($output));
  77
  78 my $gas=1;      $gas=0 if ($output =~ /\.asm$/);
  79 my $elf=1;      $elf=0 if (!$gas);
  80 my $win64=0;
  81 my $prefix="";
  82 my $decor=".L";
  83
  84 my $masmref=8 + 50727*2**-32;   # 8.00.50727 shipped with VS2005
  85 my $masm=0;
  86 my $PTR=" PTR";
  87
  88 my $nasmref=2.03;
  89 my $nasm=0;
  90
  91 if    ($flavour eq "mingw64")   { $gas=1; $elf=0; $win64=1;
  92                                   $prefix=`echo __USER_LABEL_PREFIX__ | $ENV{CC} -E -P -`;
  93                                   $prefix =~ s|\R$||; # Better chomp
  94                                 }
  95 elsif ($flavour eq "macosx")    { $gas=1; $elf=0; $prefix="_"; $decor="L\$"; }
  96 elsif ($flavour eq "masm")      { $gas=0; $elf=0; $masm=$masmref; $win64=1; $decor="\$L\$"; }
  97 elsif ($flavour eq "nasm")      { $gas=0; $elf=0; $nasm=$nasmref; $win64=1; $decor="\$L\$"; $PTR=""; }
  98 elsif (!$gas)
  99 {   if ($ENV{ASM} =~ m/nasm/ && `nasm -v` =~ m/version ([0-9]+)\.([0-9]+)/i)
 100     {   $nasm = $1 + $2*0.01; $PTR="";  }
 101     elsif (`ml64 2>&1` =~ m/Version ([0-9]+)\.([0-9]+)(\.([0-9]+))?/)
 102     {   $masm = $1 + $2*2**-16 + $4*2**-32;   }
 103     die "no assembler found on %PATH" if (!($nasm || $masm));
 104     $win64=1;
 105     $elf=0;
 106     $decor="\$L\$";
 107 }
 108
 109 my $current_segment;
 110 my $current_function;
 111 my %globals;
 112
 113 { package opcode;       # pick up opcodes
 114     sub re {
 115         my      ($class, $line) = @_;
 116         my      $self = {};
 117         my      $ret;
 118
 119         if ($$line =~ /^([a-z][a-z0-9]*)/i) {
 120             bless $self,$class;
 121             $self->{op} = $1;
 122             $ret = $self;
 123             $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 124
 125             undef $self->{sz};
 126             if ($self->{op} =~ /^(movz)x?([bw]).*/) {   # movz is pain...
 127                 $self->{op} = $1;
 128                 $self->{sz} = $2;
 129             } elsif ($self->{op} =~ /call|jmp/) {
 130                 $self->{sz} = "";
 131             } elsif ($self->{op} =~ /^p/ && $' !~ /^(ush|op|insrw)/) { # SSEn
 132                 $self->{sz} = "";
 133             } elsif ($self->{op} =~ /^v/) { # VEX
 134                 $self->{sz} = "";
 135             } elsif ($self->{op} =~ /mov[dq]/ && $$line =~ /%xmm/) {
 136                 $self->{sz} = "";
 137             } elsif ($self->{op} =~ /([a-z]{3,})([qlwb])$/) {
 138                 $self->{op} = $1;
 139                 $self->{sz} = $2;
 140             }
 141         }
 142         $ret;
 143     }
 144     sub size {
 145         my ($self, $sz) = @_;
 146         $self->{sz} = $sz if (defined($sz) && !defined($self->{sz}));
 147         $self->{sz};
 148     }
 149     sub out {
 150         my $self = shift;
 151         if ($gas) {
 152             if ($self->{op} eq "movz") {        # movz is pain...
 153                 sprintf "%s%s%s",$self->{op},$self->{sz},shift;
 154             } elsif ($self->{op} =~ /^set/) {
 155                 "$self->{op}";
 156             } elsif ($self->{op} eq "ret") {
 157                 my $epilogue = "";
 158                 if ($win64 && $current_function->{abi} eq "svr4") {
 159                     $epilogue = "movq   8(%rsp),%rdi\n\t" .
 160                                 "movq   16(%rsp),%rsi\n\t";
 161                 }
 162                 $epilogue . ".byte      0xf3,0xc3";
 163             } elsif ($self->{op} eq "call" && !$elf && $current_segment eq ".init") {
 164                 ".p2align\t3\n\t.quad";
 165             } else {
 166                 "$self->{op}$self->{sz}";
 167             }
 168         } else {
 169             $self->{op} =~ s/^movz/movzx/;
 170             if ($self->{op} eq "ret") {
 171                 $self->{op} = "";
 172                 if ($win64 && $current_function->{abi} eq "svr4") {
 173                     $self->{op} = "mov  rdi,QWORD$PTR\[8+rsp\]\t;WIN64 epilogue\n\t".
 174                                   "mov  rsi,QWORD$PTR\[16+rsp\]\n\t";
 175                 }
 176                 $self->{op} .= "DB\t0F3h,0C3h\t\t;repret";
 177             } elsif ($self->{op} =~ /^(pop|push)f/) {
 178                 $self->{op} .= $self->{sz};
 179             } elsif ($self->{op} eq "call" && $current_segment eq ".CRT\$XCU") {
 180                 $self->{op} = "\tDQ";
 181             }
 182             $self->{op};
 183         }
 184     }
 185     sub mnemonic {
 186         my ($self, $op) = @_;
 187         $self->{op}=$op if (defined($op));
 188         $self->{op};
 189     }
 190 }
 191 { package const;        # pick up constants, which start with $
 192     sub re {
 193         my      ($class, $line) = @_;
 194         my      $self = {};
 195         my      $ret;
 196
 197         if ($$line =~ /^\$([^,]+)/) {
 198             bless $self, $class;
 199             $self->{value} = $1;
 200             $ret = $self;
 201             $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 202         }
 203         $ret;
 204     }
 205     sub out {
 206         my $self = shift;
 207
 208         $self->{value} =~ s/\b(0b[0-1]+)/oct($1)/eig;
 209         if ($gas) {
 210             # Solaris /usr/ccs/bin/as can't handle multiplications
 211             # in $self->{value}
 212             my $value = $self->{value};
 213             no warnings;    # oct might complain about overflow, ignore here...
 214             $value =~ s/(?<![\w\$\.])(0x?[0-9a-f]+)/oct($1)/egi;
 215             if ($value =~ s/([0-9]+\s*[\*\/\%]\s*[0-9]+)/eval($1)/eg) {
 216                 $self->{value} = $value;
 217             }
 218             sprintf "\$%s",$self->{value};
 219         } else {
 220             $self->{value} =~ s/0x([0-9a-f]+)/0$1h/ig if ($masm);
 221             sprintf "%s",$self->{value};
 222         }
 223     }
 224 }
 225 { package ea;           # pick up effective addresses: expr(%reg,%reg,scale)
 226     sub re {
 227         my      ($class, $line, $opcode) = @_;
 228         my      $self = {};
 229         my      $ret;
 230
 231         # optional * ----vvv--- appears in indirect jmp/call
 232         if ($$line =~ /^(\*?)([^\(,]*)\(([%\w,]+)\)/) {
 233             bless $self, $class;
 234             $self->{asterisk} = $1;
 235             $self->{label} = $2;
 236             ($self->{base},$self->{index},$self->{scale})=split(/,/,$3);
 237             $self->{scale} = 1 if (!defined($self->{scale}));
 238             $ret = $self;
 239             $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 240
 241             if ($win64 && $self->{label} =~ s/\@GOTPCREL//) {
 242                 die if ($opcode->mnemonic() ne "mov");
 243                 $opcode->mnemonic("lea");
 244             }
 245             $self->{base}  =~ s/^%//;
 246             $self->{index} =~ s/^%// if (defined($self->{index}));
 247             $self->{opcode} = $opcode;
 248         }
 249         $ret;
 250     }
 251     sub size {}
 252     sub out {
 253         my ($self, $sz) = @_;
 254
 255         $self->{label} =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
 256         $self->{label} =~ s/\.L/$decor/g;
 257
 258         # Silently convert all EAs to 64-bit. This is required for
 259         # elder GNU assembler and results in more compact code,
 260         # *but* most importantly AES module depends on this feature!
 261         $self->{index} =~ s/^[er](.?[0-9xpi])[d]?$/r\1/;
 262         $self->{base}  =~ s/^[er](.?[0-9xpi])[d]?$/r\1/;
 263
 264         # Solaris /usr/ccs/bin/as can't handle multiplications
 265         # in $self->{label}...
 266         use integer;
 267         $self->{label} =~ s/(?<![\w\$\.])(0x?[0-9a-f]+)/oct($1)/egi;
 268         $self->{label} =~ s/\b([0-9]+\s*[\*\/\%]\s*[0-9]+)\b/eval($1)/eg;
 269
 270         # Some assemblers insist on signed presentation of 32-bit
 271         # offsets, but sign extension is a tricky business in perl...
 272         if ((1<<31)<<1) {
 273             $self->{label} =~ s/\b([0-9]+)\b/$1<<32>>32/eg;
 274         } else {
 275             $self->{label} =~ s/\b([0-9]+)\b/$1>>0/eg;
 276         }
 277
 278         if (!$self->{label} && $self->{index} && $self->{scale}==1 &&
 279             $self->{base} =~ /(rbp|r13)/) {
 280                 $self->{base} = $self->{index}; $self->{index} = $1;
 281         }
 282
 283         if ($gas) {
 284             $self->{label} =~ s/^___imp_/__imp__/   if ($flavour eq "mingw64");
 285
 286             if (defined($self->{index})) {
 287                 sprintf "%s%s(%s,%%%s,%d)",$self->{asterisk},
 288                                         $self->{label},
 289                                         $self->{base}?"%$self->{base}":"",
 290                                         $self->{index},$self->{scale};
 291             } else {
 292                 sprintf "%s%s(%%%s)",   $self->{asterisk},$self->{label},$self->{base};
 293             }
 294         } else {
 295             my %szmap = (       b=>"BYTE$PTR",  w=>"WORD$PTR",
 296                         l=>"DWORD$PTR", d=>"DWORD$PTR",
 297                         q=>"QWORD$PTR", o=>"OWORD$PTR",
 298                         x=>"XMMWORD$PTR", y=>"YMMWORD$PTR", z=>"ZMMWORD$PTR" );
 299
 300             $self->{label} =~ s/\./\$/g;
 301             $self->{label} =~ s/(?<![\w\$\.])0x([0-9a-f]+)/0$1h/ig;
 302             $self->{label} = "($self->{label})" if ($self->{label} =~ /[\*\+\-\/]/);
 303
 304             my $mnemonic = $self->{opcode}->mnemonic();
 305             ($self->{asterisk})                         && ($sz="q") ||
 306             ($mnemonic =~ /^v?mov([qd])$/)              && ($sz=$1)  ||
 307             ($mnemonic =~ /^v?pinsr([qdwb])$/)          && ($sz=$1)  ||
 308             ($mnemonic =~ /^vpbroadcast([qdwb])$/)      && ($sz=$1)  ||
 309             ($mnemonic =~ /^v(?!perm)[a-z]+[fi]128$/)   && ($sz="x");
 310
 311             if (defined($self->{index})) {
 312                 sprintf "%s[%s%s*%d%s]",$szmap{$sz},
 313                                         $self->{label}?"$self->{label}+":"",
 314                                         $self->{index},$self->{scale},
 315                                         $self->{base}?"+$self->{base}":"";
 316             } elsif ($self->{base} eq "rip") {
 317                 sprintf "%s[%s]",$szmap{$sz},$self->{label};
 318             } else {
 319                 sprintf "%s[%s%s]",$szmap{$sz},
 320                                         $self->{label}?"$self->{label}+":"",
 321                                         $self->{base};
 322             }
 323         }
 324     }
 325 }
 326 { package register;     # pick up registers, which start with %.
 327     sub re {
 328         my      ($class, $line, $opcode) = @_;
 329         my      $self = {};
 330         my      $ret;
 331
 332         # optional * ----vvv--- appears in indirect jmp/call
 333         if ($$line =~ /^(\*?)%(\w+)/) {
 334             bless $self,$class;
 335             $self->{asterisk} = $1;
 336             $self->{value} = $2;
 337             $opcode->size($self->size());
 338             $ret = $self;
 339             $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 340         }
 341         $ret;
 342     }
 343     sub size {
 344         my      $self = shift;
 345         my      $ret;
 346
 347         if    ($self->{value} =~ /^r[\d]+b$/i)  { $ret="b"; }
 348         elsif ($self->{value} =~ /^r[\d]+w$/i)  { $ret="w"; }
 349         elsif ($self->{value} =~ /^r[\d]+d$/i)  { $ret="l"; }
 350         elsif ($self->{value} =~ /^r[\w]+$/i)   { $ret="q"; }
 351         elsif ($self->{value} =~ /^[a-d][hl]$/i){ $ret="b"; }
 352         elsif ($self->{value} =~ /^[\w]{2}l$/i) { $ret="b"; }
 353         elsif ($self->{value} =~ /^[\w]{2}$/i)  { $ret="w"; }
 354         elsif ($self->{value} =~ /^e[a-z]{2}$/i){ $ret="l"; }
 355
 356         $ret;
 357     }
 358     sub out {
 359         my $self = shift;
 360         if ($gas)       { sprintf "%s%%%s",$self->{asterisk},$self->{value}; }
 361         else            { $self->{value}; }
 362     }
 363 }
 364 { package label;        # pick up labels, which end with :
 365     sub re {
 366         my      ($class, $line) = @_;
 367         my      $self = {};
 368         my      $ret;
 369
 370         if ($$line =~ /(^[\.\w]+)\:/) {
 371             bless $self,$class;
 372             $self->{value} = $1;
 373             $ret = $self;
 374             $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 375
 376             $self->{value} =~ s/^\.L/$decor/;
 377         }
 378         $ret;
 379     }
 380     sub out {
 381         my $self = shift;
 382
 383         if ($gas) {
 384             my $func = ($globals{$self->{value}} or $self->{value}) . ":";
 385             if ($win64  &&
 386                         $current_function->{name} eq $self->{value} &&
 387                         $current_function->{abi} eq "svr4") {
 388                 $func .= "\n";
 389                 $func .= "      movq    %rdi,8(%rsp)\n";
 390                 $func .= "      movq    %rsi,16(%rsp)\n";
 391                 $func .= "      movq    %rsp,%rax\n";
 392                 $func .= "${decor}SEH_begin_$current_function->{name}:\n";
 393                 my $narg = $current_function->{narg};
 394                 $narg=6 if (!defined($narg));
 395                 $func .= "      movq    %rcx,%rdi\n" if ($narg>0);
 396                 $func .= "      movq    %rdx,%rsi\n" if ($narg>1);
 397                 $func .= "      movq    %r8,%rdx\n"  if ($narg>2);
 398                 $func .= "      movq    %r9,%rcx\n"  if ($narg>3);
 399                 $func .= "      movq    40(%rsp),%r8\n" if ($narg>4);
 400                 $func .= "      movq    48(%rsp),%r9\n" if ($narg>5);
 401             }
 402             $func;
 403         } elsif ($self->{value} ne "$current_function->{name}") {
 404             # Make all labels in masm global.
 405             $self->{value} .= ":" if ($masm);
 406             $self->{value} . ":";
 407         } elsif ($win64 && $current_function->{abi} eq "svr4") {
 408             my $func =  "$current_function->{name}" .
 409                         ($nasm ? ":" : "\tPROC $current_function->{scope}") .
 410                         "\n";
 411             $func .= "  mov     QWORD$PTR\[8+rsp\],rdi\t;WIN64 prologue\n";
 412             $func .= "  mov     QWORD$PTR\[16+rsp\],rsi\n";
 413             $func .= "  mov     rax,rsp\n";
 414             $func .= "${decor}SEH_begin_$current_function->{name}:";
 415             $func .= ":" if ($masm);
 416             $func .= "\n";
 417             my $narg = $current_function->{narg};
 418             $narg=6 if (!defined($narg));
 419             $func .= "  mov     rdi,rcx\n" if ($narg>0);
 420             $func .= "  mov     rsi,rdx\n" if ($narg>1);
 421             $func .= "  mov     rdx,r8\n"  if ($narg>2);
 422             $func .= "  mov     rcx,r9\n"  if ($narg>3);
 423             $func .= "  mov     r8,QWORD$PTR\[40+rsp\]\n" if ($narg>4);
 424             $func .= "  mov     r9,QWORD$PTR\[48+rsp\]\n" if ($narg>5);
 425             $func .= "\n";
 426         } else {
 427            "$current_function->{name}".
 428                         ($nasm ? ":" : "\tPROC $current_function->{scope}");
 429         }
 430     }
 431 }
 432 { package expr;         # pick up expressioins
 433     sub re {
 434         my      ($class, $line, $opcode) = @_;
 435         my      $self = {};
 436         my      $ret;
 437
 438         if ($$line =~ /(^[^,]+)/) {
 439             bless $self,$class;
 440             $self->{value} = $1;
 441             $ret = $self;
 442             $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 443
 444             $self->{value} =~ s/\@PLT// if (!$elf);
 445             $self->{value} =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
 446             $self->{value} =~ s/\.L/$decor/g;
 447             $self->{opcode} = $opcode;
 448         }
 449         $ret;
 450     }
 451     sub out {
 452         my $self = shift;
 453         if ($nasm && $self->{opcode}->mnemonic()=~m/^j(?![re]cxz)/) {
 454             "NEAR ".$self->{value};
 455         } else {
 456             $self->{value};
 457         }
 458     }
 459 }
 460 { package directive;    # pick up directives, which start with .
 461     sub re {
 462         my      ($class, $line) = @_;
 463         my      $self = {};
 464         my      $ret;
 465         my      $dir;
 466         my      %opcode =       # lea 2f-1f(%rip),%dst; 1: nop; 2:
 467                 (       "%rax"=>0x01058d48,     "%rcx"=>0x010d8d48,
 468                         "%rdx"=>0x01158d48,     "%rbx"=>0x011d8d48,
 469                         "%rsp"=>0x01258d48,     "%rbp"=>0x012d8d48,
 470                         "%rsi"=>0x01358d48,     "%rdi"=>0x013d8d48,
 471                         "%r8" =>0x01058d4c,     "%r9" =>0x010d8d4c,
 472                         "%r10"=>0x01158d4c,     "%r11"=>0x011d8d4c,
 473                         "%r12"=>0x01258d4c,     "%r13"=>0x012d8d4c,
 474                         "%r14"=>0x01358d4c,     "%r15"=>0x013d8d4c      );
 475
 476         if ($$line =~ /^\s*(\.\w+)/) {
 477             bless $self,$class;
 478             $dir = $1;
 479             $ret = $self;
 480             undef $self->{value};
 481             $$line = substr($$line,@+[0]); $$line =~ s/^\s+//;
 482
 483             SWITCH: for ($dir) {
 484                 /\.picmeup/ && do { if ($$line =~ /(%r[\w]+)/i) {
 485                                         $dir="\t.long";
 486                                         $$line=sprintf "0x%x,0x90000000",$opcode{$1};
 487                                     }
 488                                     last;
 489                                   };
 490                 /\.global|\.globl|\.extern/
 491                             && do { $globals{$$line} = $prefix . $$line;
 492                                     $$line = $globals{$$line} if ($prefix);
 493                                     last;
 494                                   };
 495                 /\.type/    && do { my ($sym,$type,$narg) = split(',',$$line);
 496                                     if ($type eq "\@function") {
 497                                         undef $current_function;
 498                                         $current_function->{name} = $sym;
 499                                         $current_function->{abi}  = "svr4";
 500                                         $current_function->{narg} = $narg;
 501                                         $current_function->{scope} = defined($globals{$sym})?"PUBLIC":"PRIVATE";
 502                                     } elsif ($type eq "\@abi-omnipotent") {
 503                                         undef $current_function;
 504                                         $current_function->{name} = $sym;
 505                                         $current_function->{scope} = defined($globals{$sym})?"PUBLIC":"PRIVATE";
 506                                     }
 507                                     $$line =~ s/\@abi\-omnipotent/\@function/;
 508                                     $$line =~ s/\@function.*/\@function/;
 509                                     last;
 510                                   };
 511                 /\.asciz/   && do { if ($$line =~ /^"(.*)"$/) {
 512                                         $dir  = ".byte";
 513                                         $$line = join(",",unpack("C*",$1),0);
 514                                     }
 515                                     last;
 516                                   };
 517                 /\.rva|\.long|\.quad/
 518                             && do { $$line =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
 519                                     $$line =~ s/\.L/$decor/g;
 520                                     last;
 521                                   };
 522             }
 523
 524             if ($gas) {
 525                 $self->{value} = $dir . "\t" . $$line;
 526
 527                 if ($dir =~ /\.extern/) {
 528                     $self->{value} = ""; # swallow extern
 529                 } elsif (!$elf && $dir =~ /\.type/) {
 530                     $self->{value} = "";
 531                     $self->{value} = ".def\t" . ($globals{$1} or $1) . ";\t" .
 532                                 (defined($globals{$1})?".scl 2;":".scl 3;") .
 533                                 "\t.type 32;\t.endef"
 534                                 if ($win64 && $$line =~ /([^,]+),\@function/);
 535                 } elsif (!$elf && $dir =~ /\.size/) {
 536                     $self->{value} = "";
 537                     if (defined($current_function)) {
 538                         $self->{value} .= "${decor}SEH_end_$current_function->{name}:"
 539                                 if ($win64 && $current_function->{abi} eq "svr4");
 540                         undef $current_function;
 541                     }
 542                 } elsif (!$elf && $dir =~ /\.align/) {
 543                     $self->{value} = ".p2align\t" . (log($$line)/log(2));
 544                 } elsif ($dir eq ".section") {
 545                     $current_segment=$$line;
 546                     if (!$elf && $current_segment eq ".init") {
 547                         if      ($flavour eq "macosx")  { $self->{value} = ".mod_init_func"; }
 548                         elsif   ($flavour eq "mingw64") { $self->{value} = ".section\t.ctors"; }
 549                     }
 550                 } elsif ($dir =~ /\.(text|data)/) {
 551                     $current_segment=".$1";
 552                 } elsif ($dir =~ /\.hidden/) {
 553                     if    ($flavour eq "macosx")  { $self->{value} = ".private_extern\t$prefix$$line"; }
 554                     elsif ($flavour eq "mingw64") { $self->{value} = ""; }
 555                 } elsif ($dir =~ /\.comm/) {
 556                     $self->{value} = "$dir\t$prefix$$line";
 557                     $self->{value} =~ s|,([0-9]+),([0-9]+)$|",$1,".log($2)/log(2)|e if ($flavour eq "macosx");
 558                 }
 559                 $$line = "";
 560                 return $self;
 561             }
 562
 563             # non-gas case or nasm/masm
 564             SWITCH: for ($dir) {
 565                 /\.text/    && do { my $v=undef;
 566                                     if ($nasm) {
 567                                         $v="section     .text code align=64\n";
 568                                     } else {
 569                                         $v="$current_segment\tENDS\n" if ($current_segment);
 570                                         $current_segment = ".text\$";
 571                                         $v.="$current_segment\tSEGMENT ";
 572                                         $v.=$masm>=$masmref ? "ALIGN(256)" : "PAGE";
 573                                         $v.=" 'CODE'";
 574                                     }
 575                                     $self->{value} = $v;
 576                                     last;
 577                                   };
 578                 /\.data/    && do { my $v=undef;
 579                                     if ($nasm) {
 580                                         $v="section     .data data align=8\n";
 581                                     } else {
 582                                         $v="$current_segment\tENDS\n" if ($current_segment);
 583                                         $current_segment = "_DATA";
 584                                         $v.="$current_segment\tSEGMENT";
 585                                     }
 586                                     $self->{value} = $v;
 587                                     last;
 588                                   };
 589                 /\.section/ && do { my $v=undef;
 590                                     $$line =~ s/([^,]*).*/$1/;
 591                                     $$line = ".CRT\$XCU" if ($$line eq ".init");
 592                                     if ($nasm) {
 593                                         $v="section     $$line";
 594                                         if ($$line=~/\.([px])data/) {
 595                                             $v.=" rdata align=";
 596                                             $v.=$1 eq "p"? 4 : 8;
 597                                         } elsif ($$line=~/\.CRT\$/i) {
 598                                             $v.=" rdata align=8";
 599                                         }
 600                                     } else {
 601                                         $v="$current_segment\tENDS\n" if ($current_segment);
 602                                         $v.="$$line\tSEGMENT";
 603                                         if ($$line=~/\.([px])data/) {
 604                                             $v.=" READONLY";
 605                                             $v.=" ALIGN(".($1 eq "p" ? 4 : 8).")" if ($masm>=$masmref);
 606                                         } elsif ($$line=~/\.CRT\$/i) {
 607                                             $v.=" READONLY ";
 608                                             $v.=$masm>=$masmref ? "ALIGN(8)" : "DWORD";
 609                                         }
 610                                     }
 611                                     $current_segment = $$line;
 612                                     $self->{value} = $v;
 613                                     last;
 614                                   };
 615                 /\.extern/  && do { $self->{value}  = "EXTERN\t".$$line;
 616                                     $self->{value} .= ":NEAR" if ($masm);
 617                                     last;
 618                                   };
 619                 /\.globl|.global/
 620                             && do { $self->{value}  = $masm?"PUBLIC":"global";
 621                                     $self->{value} .= "\t".$$line;
 622                                     last;
 623                                   };
 624                 /\.size/    && do { if (defined($current_function)) {
 625                                         undef $self->{value};
 626                                         if ($current_function->{abi} eq "svr4") {
 627                                             $self->{value}="${decor}SEH_end_$current_function->{name}:";
 628                                             $self->{value}.=":\n" if($masm);
 629                                         }
 630                                         $self->{value}.="$current_function->{name}\tENDP" if($masm && $current_function->{name});
 631                                         undef $current_function;
 632                                     }
 633                                     last;
 634                                   };
 635                 /\.align/   && do { my $max = ($masm && $masm>=$masmref) ? 256 : 4096;
 636                                     $self->{value} = "ALIGN\t".($$line>$max?$max:$$line);
 637                                     last;
 638                                   };
 639                 /\.(value|long|rva|quad)/
 640                             && do { my $sz  = substr($1,0,1);
 641                                     my @arr = split(/,\s*/,$$line);
 642                                     my $last = pop(@arr);
 643                                     my $conv = sub  {   my $var=shift;
 644                                                         $var=~s/^(0b[0-1]+)/oct($1)/eig;
 645                                                         $var=~s/^0x([0-9a-f]+)/0$1h/ig if ($masm);
 646                                                         if ($sz eq "D" && ($current_segment=~/.[px]data/ || $dir eq ".rva"))
 647                                                         { $var=~s/([_a-z\$\@][_a-z0-9\$\@]*)/$nasm?"$1 wrt ..imagebase":"imagerel $1"/egi; }
 648                                                         $var;
 649                                                     };
 650
 651                                     $sz =~ tr/bvlrq/BWDDQ/;
 652                                     $self->{value} = "\tD$sz\t";
 653                                     for (@arr) { $self->{value} .= &$conv($_).","; }
 654                                     $self->{value} .= &$conv($last);
 655                                     last;
 656                                   };
 657                 /\.byte/    && do { my @str=split(/,\s*/,$$line);
 658                                     map(s/(0b[0-1]+)/oct($1)/eig,@str);
 659                                     map(s/0x([0-9a-f]+)/0$1h/ig,@str) if ($masm);
 660                                     while ($#str>15) {
 661                                         $self->{value}.="DB\t"
 662                                                 .join(",",@str[0..15])."\n";
 663                                         foreach (0..15) { shift @str; }
 664                                     }
 665                                     $self->{value}.="DB\t"
 666                                                 .join(",",@str) if (@str);
 667                                     last;
 668                                   };
 669                 /\.comm/    && do { my @str=split(/,\s*/,$$line);
 670                                     my $v=undef;
 671                                     if ($nasm) {
 672                                         $v.="common     $prefix@str[0] @str[1]";
 673                                     } else {
 674                                         $v="$current_segment\tENDS\n" if ($current_segment);
 675                                         $current_segment = "_DATA";
 676                                         $v.="$current_segment\tSEGMENT\n";
 677                                         $v.="COMM       @str[0]:DWORD:".@str[1]/4;
 678                                     }
 679                                     $self->{value} = $v;
 680                                     last;
 681                                   };
 682             }
 683             $$line = "";
 684         }
 685
 686         $ret;
 687     }
 688     sub out {
 689         my $self = shift;
 690         $self->{value};
 691     }
 692 }
 693
 694 sub rex {
 695  my $opcode=shift;
 696  my ($dst,$src,$rex)=@_;
 697
 698    $rex|=0x04 if($dst>=8);
 699    $rex|=0x01 if($src>=8);
 700    push @$opcode,($rex|0x40) if ($rex);
 701 }
 702
 703 # Upon initial x86_64 introduction SSE>2 extensions were not introduced
 704 # yet. In order not to be bothered by tracing exact assembler versions,
 705 # but at the same time to provide a bare security minimum of AES-NI, we
 706 # hard-code some instructions. Extensions past AES-NI on the other hand
 707 # are traced by examining assembler version in individual perlasm
 708 # modules...
 709
 710 my %regrm = (   "%eax"=>0, "%ecx"=>1, "%edx"=>2, "%ebx"=>3,
 711                 "%esp"=>4, "%ebp"=>5, "%esi"=>6, "%edi"=>7      );
 712
 713 my $movq = sub {        # elderly gas can't handle inter-register movq
 714   my $arg = shift;
 715   my @opcode=(0x66);
 716     if ($arg =~ /%xmm([0-9]+),\s*%r(\w+)/) {
 717         my ($src,$dst)=($1,$2);
 718         if ($dst !~ /[0-9]+/)   { $dst = $regrm{"%e$dst"}; }
 719         rex(\@opcode,$src,$dst,0x8);
 720         push @opcode,0x0f,0x7e;
 721         push @opcode,0xc0|(($src&7)<<3)|($dst&7);       # ModR/M
 722         @opcode;
 723     } elsif ($arg =~ /%r(\w+),\s*%xmm([0-9]+)/) {
 724         my ($src,$dst)=($2,$1);
 725         if ($dst !~ /[0-9]+/)   { $dst = $regrm{"%e$dst"}; }
 726         rex(\@opcode,$src,$dst,0x8);
 727         push @opcode,0x0f,0x6e;
 728         push @opcode,0xc0|(($src&7)<<3)|($dst&7);       # ModR/M
 729         @opcode;
 730     } else {
 731         ();
 732     }
 733 };
 734
 735 my $pextrd = sub {
 736     if (shift =~ /\$([0-9]+),\s*%xmm([0-9]+),\s*(%\w+)/) {
 737       my @opcode=(0x66);
 738         my $imm=$1;
 739         my $src=$2;
 740         my $dst=$3;
 741         if ($dst =~ /%r([0-9]+)d/)      { $dst = $1; }
 742         elsif ($dst =~ /%e/)            { $dst = $regrm{$dst}; }
 743         rex(\@opcode,$src,$dst);
 744         push @opcode,0x0f,0x3a,0x16;
 745         push @opcode,0xc0|(($src&7)<<3)|($dst&7);       # ModR/M
 746         push @opcode,$imm;
 747         @opcode;
 748     } else {
 749         ();
 750     }
 751 };
 752
 753 my $pinsrd = sub {
 754     if (shift =~ /\$([0-9]+),\s*(%\w+),\s*%xmm([0-9]+)/) {
 755       my @opcode=(0x66);
 756         my $imm=$1;
 757         my $src=$2;
 758         my $dst=$3;
 759         if ($src =~ /%r([0-9]+)/)       { $src = $1; }
 760         elsif ($src =~ /%e/)            { $src = $regrm{$src}; }
 761         rex(\@opcode,$dst,$src);
 762         push @opcode,0x0f,0x3a,0x22;
 763         push @opcode,0xc0|(($dst&7)<<3)|($src&7);       # ModR/M
 764         push @opcode,$imm;
 765         @opcode;
 766     } else {
 767         ();
 768     }
 769 };
 770
 771 my $pshufb = sub {
 772     if (shift =~ /%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 773       my @opcode=(0x66);
 774         rex(\@opcode,$2,$1);
 775         push @opcode,0x0f,0x38,0x00;
 776         push @opcode,0xc0|($1&7)|(($2&7)<<3);           # ModR/M
 777         @opcode;
 778     } else {
 779         ();
 780     }
 781 };
 782
 783 my $palignr = sub {
 784     if (shift =~ /\$([0-9]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 785       my @opcode=(0x66);
 786         rex(\@opcode,$3,$2);
 787         push @opcode,0x0f,0x3a,0x0f;
 788         push @opcode,0xc0|($2&7)|(($3&7)<<3);           # ModR/M
 789         push @opcode,$1;
 790         @opcode;
 791     } else {
 792         ();
 793     }
 794 };
 795
 796 my $pclmulqdq = sub {
 797     if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 798       my @opcode=(0x66);
 799         rex(\@opcode,$3,$2);
 800         push @opcode,0x0f,0x3a,0x44;
 801         push @opcode,0xc0|($2&7)|(($3&7)<<3);           # ModR/M
 802         my $c=$1;
 803         push @opcode,$c=~/^0/?oct($c):$c;
 804         @opcode;
 805     } else {
 806         ();
 807     }
 808 };
 809
 810 my $rdrand = sub {
 811     if (shift =~ /%[er](\w+)/) {
 812       my @opcode=();
 813       my $dst=$1;
 814         if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
 815         rex(\@opcode,0,$dst,8);
 816         push @opcode,0x0f,0xc7,0xf0|($dst&7);
 817         @opcode;
 818     } else {
 819         ();
 820     }
 821 };
 822
 823 my $rdseed = sub {
 824     if (shift =~ /%[er](\w+)/) {
 825       my @opcode=();
 826       my $dst=$1;
 827         if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
 828         rex(\@opcode,0,$dst,8);
 829         push @opcode,0x0f,0xc7,0xf8|($dst&7);
 830         @opcode;
 831     } else {
 832         ();
 833     }
 834 };
 835
 836 sub rxb {
 837  my $opcode=shift;
 838  my ($dst,$src1,$src2,$rxb)=@_;
 839
 840    $rxb|=0x7<<5;
 841    $rxb&=~(0x04<<5) if($dst>=8);
 842    $rxb&=~(0x01<<5) if($src1>=8);
 843    $rxb&=~(0x02<<5) if($src2>=8);
 844    push @$opcode,$rxb;
 845 }
 846
 847 my $vprotd = sub {
 848     if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 849       my @opcode=(0x8f);
 850         rxb(\@opcode,$3,$2,-1,0x08);
 851         push @opcode,0x78,0xc2;
 852         push @opcode,0xc0|($2&7)|(($3&7)<<3);           # ModR/M
 853         my $c=$1;
 854         push @opcode,$c=~/^0/?oct($c):$c;
 855         @opcode;
 856     } else {
 857         ();
 858     }
 859 };
 860
 861 my $vprotq = sub {
 862     if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 863       my @opcode=(0x8f);
 864         rxb(\@opcode,$3,$2,-1,0x08);
 865         push @opcode,0x78,0xc3;
 866         push @opcode,0xc0|($2&7)|(($3&7)<<3);           # ModR/M
 867         my $c=$1;
 868         push @opcode,$c=~/^0/?oct($c):$c;
 869         @opcode;
 870     } else {
 871         ();
 872     }
 873 };
 874
 875 my $endbranch = sub {
 876     (0xf3,0x0f,0x1e,0xfa);
 877 };
 878
 879 if ($nasm) {
 880     print <<___;
 881 default rel
 882 %define XMMWORD
 883 %define YMMWORD
 884 %define ZMMWORD
 885 ___
 886 } elsif ($masm) {
 887     print <<___;
 888 OPTION  DOTNAME
 889 ___
 890 }
 891 while(defined(my $line=<>)) {
 892
 893     $line =~ s|\R$||;           # Better chomp
 894
 895     $line =~ s|[#!].*$||;       # get rid of asm-style comments...
 896     $line =~ s|/\*.*\*/||;      # ... and C-style comments...
 897     $line =~ s|^\s+||;          # ... and skip white spaces in beginning
 898     $line =~ s|\s+$||;          # ... and at the end
 899
 900     if (my $label=label->re(\$line))    { print $label->out(); }
 901
 902     if (my $directive=directive->re(\$line)) {
 903         printf "%s",$directive->out();
 904     } elsif (my $opcode=opcode->re(\$line)) {
 905         my $asm = eval("\$".$opcode->mnemonic());
 906
 907         if ((ref($asm) eq 'CODE') && scalar(my @bytes=&$asm($line))) {
 908             print $gas?".byte\t":"DB\t",join(',',@bytes),"\n";
 909             next;
 910         }
 911
 912         my @args;
 913         ARGUMENT: while (1) {
 914             my $arg;
 915
 916             ($arg=register->re(\$line, $opcode))||
 917             ($arg=const->re(\$line))            ||
 918             ($arg=ea->re(\$line, $opcode))      ||
 919             ($arg=expr->re(\$line, $opcode))    ||
 920             last ARGUMENT;
 921
 922             push @args,$arg;
 923
 924             last ARGUMENT if ($line !~ /^,/);
 925
 926             $line =~ s/^,\s*//;
 927         } # ARGUMENT:
 928
 929         if ($#args>=0) {
 930             my $insn;
 931             my $sz=$opcode->size();
 932
 933             if ($gas) {
 934                 $insn = $opcode->out($#args>=1?$args[$#args]->size():$sz);
 935                 @args = map($_->out($sz),@args);
 936                 printf "\t%s\t%s",$insn,join(",",@args);
 937             } else {
 938                 $insn = $opcode->out();
 939                 foreach (@args) {
 940                     my $arg = $_->out();
 941                     # $insn.=$sz compensates for movq, pinsrw, ...
 942                     if ($arg =~ /^xmm[0-9]+$/) { $insn.=$sz; $sz="x" if(!$sz); last; }
 943                     if ($arg =~ /^ymm[0-9]+$/) { $insn.=$sz; $sz="y" if(!$sz); last; }
 944                     if ($arg =~ /^zmm[0-9]+$/) { $insn.=$sz; $sz="z" if(!$sz); last; }
 945                     if ($arg =~ /^mm[0-9]+$/)  { $insn.=$sz; $sz="q" if(!$sz); last; }
 946                 }
 947                 @args = reverse(@args);
 948                 undef $sz if ($nasm && $opcode->mnemonic() eq "lea");
 949                 printf "\t%s\t%s",$insn,join(",",map($_->out($sz),@args));
 950             }
 951         } else {
 952             printf "\t%s",$opcode->out();
 953         }
 954     }
 955
 956     print $line,"\n";
 957 }
 958
 959 print "\n$current_segment\tENDS\n"      if ($current_segment && $masm);
 960 print "END\n"                           if ($masm);
 961
 962 close STDOUT;
 963
 964 \f#################################################
 965 # Cross-reference x86_64 ABI "card"
 966 #
 967 #               Unix            Win64
 968 # %rax          *               *
 969 # %rbx          -               -
 970 # %rcx          #4              #1
 971 # %rdx          #3              #2
 972 # %rsi          #2              -
 973 # %rdi          #1              -
 974 # %rbp          -               -
 975 # %rsp          -               -
 976 # %r8           #5              #3
 977 # %r9           #6              #4
 978 # %r10          *               *
 979 # %r11          *               *
 980 # %r12          -               -
 981 # %r13          -               -
 982 # %r14          -               -
 983 # %r15          -               -
 984 #
 985 # (*)   volatile register
 986 # (-)   preserved by callee
 987 # (#)   Nth argument, volatile
 988 #
 989 # In Unix terms top of stack is argument transfer area for arguments
 990 # which could not be accommodated in registers. Or in other words 7th
 991 # [integer] argument resides at 8(%rsp) upon function entry point.
 992 # 128 bytes above %rsp constitute a "red zone" which is not touched
 993 # by signal handlers and can be used as temporal storage without
 994 # allocating a frame.
 995 #
 996 # In Win64 terms N*8 bytes on top of stack is argument transfer area,
 997 # which belongs to/can be overwritten by callee. N is the number of
 998 # arguments passed to callee, *but* not less than 4! This means that
 999 # upon function entry point 5th argument resides at 40(%rsp), as well
1000 # as that 32 bytes from 8(%rsp) can always be used as temporal
1001 # storage [without allocating a frame]. One can actually argue that
1002 # one can assume a "red zone" above stack pointer under Win64 as well.
1003 # Point is that at apparently no occasion Windows kernel would alter
1004 # the area above user stack pointer in true asynchronous manner...
1005 #
1006 # All the above means that if assembler programmer adheres to Unix
1007 # register and stack layout, but disregards the "red zone" existense,
1008 # it's possible to use following prologue and epilogue to "gear" from
1009 # Unix to Win64 ABI in leaf functions with not more than 6 arguments.
1010 #
1011 # omnipotent_function:
1012 # ifdef WIN64
1013 #       movq    %rdi,8(%rsp)
1014 #       movq    %rsi,16(%rsp)
1015 #       movq    %rcx,%rdi       ; if 1st argument is actually present
1016 #       movq    %rdx,%rsi       ; if 2nd argument is actually ...
1017 #       movq    %r8,%rdx        ; if 3rd argument is ...
1018 #       movq    %r9,%rcx        ; if 4th argument ...
1019 #       movq    40(%rsp),%r8    ; if 5th ...
1020 #       movq    48(%rsp),%r9    ; if 6th ...
1021 # endif
1022 #       ...
1023 # ifdef WIN64
1024 #       movq    8(%rsp),%rdi
1025 #       movq    16(%rsp),%rsi
1026 # endif
1027 #       ret
1028 #
1029 \f#################################################
1030 # Win64 SEH, Structured Exception Handling.
1031 #
1032 # Unlike on Unix systems(*) lack of Win64 stack unwinding information
1033 # has undesired side-effect at run-time: if an exception is raised in
1034 # assembler subroutine such as those in question (basically we're
1035 # referring to segmentation violations caused by malformed input
1036 # parameters), the application is briskly terminated without invoking
1037 # any exception handlers, most notably without generating memory dump
1038 # or any user notification whatsoever. This poses a problem. It's
1039 # possible to address it by registering custom language-specific
1040 # handler that would restore processor context to the state at
1041 # subroutine entry point and return "exception is not handled, keep
1042 # unwinding" code. Writing such handler can be a challenge... But it's
1043 # doable, though requires certain coding convention. Consider following
1044 # snippet:
1045 #
1046 # .type function,@function
1047 # function:
1048 #       movq    %rsp,%rax       # copy rsp to volatile register
1049 #       pushq   %r15            # save non-volatile registers
1050 #       pushq   %rbx
1051 #       pushq   %rbp
1052 #       movq    %rsp,%r11
1053 #       subq    %rdi,%r11       # prepare [variable] stack frame
1054 #       andq    $-64,%r11
1055 #       movq    %rax,0(%r11)    # check for exceptions
1056 #       movq    %r11,%rsp       # allocate [variable] stack frame
1057 #       movq    %rax,0(%rsp)    # save original rsp value
1058 # magic_point:
1059 #       ...
1060 #       movq    0(%rsp),%rcx    # pull original rsp value
1061 #       movq    -24(%rcx),%rbp  # restore non-volatile registers
1062 #       movq    -16(%rcx),%rbx
1063 #       movq    -8(%rcx),%r15
1064 #       movq    %rcx,%rsp       # restore original rsp
1065 #       ret
1066 # .size function,.-function
1067 #
1068 # The key is that up to magic_point copy of original rsp value remains
1069 # in chosen volatile register and no non-volatile register, except for
1070 # rsp, is modified. While past magic_point rsp remains constant till
1071 # the very end of the function. In this case custom language-specific
1072 # exception handler would look like this:
1073 #
1074 # EXCEPTION_DISPOSITION handler (EXCEPTION_RECORD *rec,ULONG64 frame,
1075 #               CONTEXT *context,DISPATCHER_CONTEXT *disp)
1076 # {     ULONG64 *rsp = (ULONG64 *)context->Rax;
1077 #       if (context->Rip >= magic_point)
1078 #       {   rsp = ((ULONG64 **)context->Rsp)[0];
1079 #           context->Rbp = rsp[-3];
1080 #           context->Rbx = rsp[-2];
1081 #           context->R15 = rsp[-1];
1082 #       }
1083 #       context->Rsp = (ULONG64)rsp;
1084 #       context->Rdi = rsp[1];
1085 #       context->Rsi = rsp[2];
1086 #
1087 #       memcpy (disp->ContextRecord,context,sizeof(CONTEXT));
1088 #       RtlVirtualUnwind(UNW_FLAG_NHANDLER,disp->ImageBase,
1089 #               dips->ControlPc,disp->FunctionEntry,disp->ContextRecord,
1090 #               &disp->HandlerData,&disp->EstablisherFrame,NULL);
1091 #       return ExceptionContinueSearch;
1092 # }
1093 #
1094 # It's appropriate to implement this handler in assembler, directly in
1095 # function's module. In order to do that one has to know members'
1096 # offsets in CONTEXT and DISPATCHER_CONTEXT structures and some constant
1097 # values. Here they are:
1098 #
1099 #       CONTEXT.Rax                             120
1100 #       CONTEXT.Rcx                             128
1101 #       CONTEXT.Rdx                             136
1102 #       CONTEXT.Rbx                             144
1103 #       CONTEXT.Rsp                             152
1104 #       CONTEXT.Rbp                             160
1105 #       CONTEXT.Rsi                             168
1106 #       CONTEXT.Rdi                             176
1107 #       CONTEXT.R8                              184
1108 #       CONTEXT.R9                              192
1109 #       CONTEXT.R10                             200
1110 #       CONTEXT.R11                             208
1111 #       CONTEXT.R12                             216
1112 #       CONTEXT.R13                             224
1113 #       CONTEXT.R14                             232
1114 #       CONTEXT.R15                             240
1115 #       CONTEXT.Rip                             248
1116 #       CONTEXT.Xmm6                            512
1117 #       sizeof(CONTEXT)                         1232
1118 #       DISPATCHER_CONTEXT.ControlPc            0
1119 #       DISPATCHER_CONTEXT.ImageBase            8
1120 #       DISPATCHER_CONTEXT.FunctionEntry        16
1121 #       DISPATCHER_CONTEXT.EstablisherFrame     24
1122 #       DISPATCHER_CONTEXT.TargetIp             32
1123 #       DISPATCHER_CONTEXT.ContextRecord        40
1124 #       DISPATCHER_CONTEXT.LanguageHandler      48
1125 #       DISPATCHER_CONTEXT.HandlerData          56
1126 #       UNW_FLAG_NHANDLER                       0
1127 #       ExceptionContinueSearch                 1
1128 #
1129 # In order to tie the handler to the function one has to compose
1130 # couple of structures: one for .xdata segment and one for .pdata.
1131 #
1132 # UNWIND_INFO structure for .xdata segment would be
1133 #
1134 # function_unwind_info:
1135 #       .byte   9,0,0,0
1136 #       .rva    handler
1137 #
1138 # This structure designates exception handler for a function with
1139 # zero-length prologue, no stack frame or frame register.
1140 #
1141 # To facilitate composing of .pdata structures, auto-generated "gear"
1142 # prologue copies rsp value to rax and denotes next instruction with
1143 # .LSEH_begin_{function_name} label. This essentially defines the SEH
1144 # styling rule mentioned in the beginning. Position of this label is
1145 # chosen in such manner that possible exceptions raised in the "gear"
1146 # prologue would be accounted to caller and unwound from latter's frame.
1147 # End of function is marked with respective .LSEH_end_{function_name}
1148 # label. To summarize, .pdata segment would contain
1149 #
1150 #       .rva    .LSEH_begin_function
1151 #       .rva    .LSEH_end_function
1152 #       .rva    function_unwind_info
1153 #
1154 # Reference to function_unwind_info from .xdata segment is the anchor.
1155 # In case you wonder why references are 32-bit .rvas and not 64-bit
1156 # .quads. References put into these two segments are required to be
1157 # *relative* to the base address of the current binary module, a.k.a.
1158 # image base. No Win64 module, be it .exe or .dll, can be larger than
1159 # 2GB and thus such relative references can be and are accommodated in
1160 # 32 bits.
1161 #
1162 # Having reviewed the example function code, one can argue that "movq
1163 # %rsp,%rax" above is redundant. It is not! Keep in mind that on Unix
1164 # rax would contain an undefined value. If this "offends" you, use
1165 # another register and refrain from modifying rax till magic_point is
1166 # reached, i.e. as if it was a non-volatile register. If more registers
1167 # are required prior [variable] frame setup is completed, note that
1168 # nobody says that you can have only one "magic point." You can
1169 # "liberate" non-volatile registers by denoting last stack off-load
1170 # instruction and reflecting it in finer grade unwind logic in handler.
1171 # After all, isn't it why it's called *language-specific* handler...
1172 #
1173 # Attentive reader can notice that exceptions would be mishandled in
1174 # auto-generated "gear" epilogue. Well, exception effectively can't
1175 # occur there, because if memory area used by it was subject to
1176 # segmentation violation, then it would be raised upon call to the
1177 # function (and as already mentioned be accounted to caller, which is
1178 # not a problem). If you're still not comfortable, then define tail
1179 # "magic point" just prior ret instruction and have handler treat it...
1180 #
1181 # (*)   Note that we're talking about run-time, not debug-time. Lack of
1182 #       unwind information makes debugging hard on both Windows and
1183 #       Unix. "Unlike" referes to the fact that on Unix signal handler
1184 #       will always be invoked, core dumped and appropriate exit code
1185 #       returned to parent (for user notification).