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