crypto/perlasm/x86_64-xlate.pl

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