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         $self->{value} =~ s/\b(0b[0-1]+)/oct($1)/eig;
 199         if ($gas) {
 200             # Solaris /usr/ccs/bin/as can't handle multiplications
 201             # in $self->{value}
 202             my $value = $self->{value};
 203             $value =~ s/(?<![\w\$\.])(0x?[0-9a-f]+)/oct($1)/egi;
 204             if ($value =~ s/([0-9]+\s*[\*\/\%]\s*[0-9]+)/eval($1)/eg) {
 205                 $self->{value} = $value;
 206             }
 207             sprintf "\$%s",$self->{value};
 208         } else {
 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}...
 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
 258         # Some assemblers insist on signed presentation of 32-bit
 259         # offsets, but sign extension is a tricky business in perl...
 260         if ((1<<31)<<1) {
 261             $self->{label} =~ s/\b([0-9]+)\b/$1<<32>>32/eg;
 262         } else {
 263             $self->{label} =~ s/\b([0-9]+)\b/$1>>0/eg;
 264         }
 265
 266         if (!$self->{label} && $self->{index} && $self->{scale}==1 &&
 267             $self->{base} =~ /(rbp|r13)/) {
 268                 $self->{base} = $self->{index}; $self->{index} = $1;
 269         }
 270
 271         if ($gas) {
 272             $self->{label} =~ s/^___imp_/__imp__/   if ($flavour eq "mingw64");
 273
 274             if (defined($self->{index})) {
 275                 sprintf "%s%s(%s,%%%s,%d)",$self->{asterisk},
 276                                         $self->{label},
 277                                         $self->{base}?"%$self->{base}":"",
 278                                         $self->{index},$self->{scale};
 279             } else {
 280                 sprintf "%s%s(%%%s)",   $self->{asterisk},$self->{label},$self->{base};
 281             }
 282         } else {
 283             %szmap = (  b=>"BYTE$PTR",  w=>"WORD$PTR",
 284                         l=>"DWORD$PTR", d=>"DWORD$PTR",
 285                         q=>"QWORD$PTR", o=>"OWORD$PTR",
 286                         x=>"XMMWORD$PTR", y=>"YMMWORD$PTR", z=>"ZMMWORD$PTR" );
 287
 288             $self->{label} =~ s/\./\$/g;
 289             $self->{label} =~ s/(?<![\w\$\.])0x([0-9a-f]+)/0$1h/ig;
 290             $self->{label} = "($self->{label})" if ($self->{label} =~ /[\*\+\-\/]/);
 291
 292             ($self->{asterisk})                                 && ($sz="q") ||
 293             (opcode->mnemonic() =~ /^v?mov([qd])$/)             && ($sz=$1)  ||
 294             (opcode->mnemonic() =~ /^v?pinsr([qdwb])$/)         && ($sz=$1)  ||
 295             (opcode->mnemonic() =~ /^vpbroadcast([qdwb])$/)     && ($sz=$1)  ||
 296             (opcode->mnemonic() =~ /^vinsert[fi]128$/)          && ($sz="x");
 297
 298             if (defined($self->{index})) {
 299                 sprintf "%s[%s%s*%d%s]",$szmap{$sz},
 300                                         $self->{label}?"$self->{label}+":"",
 301                                         $self->{index},$self->{scale},
 302                                         $self->{base}?"+$self->{base}":"";
 303             } elsif ($self->{base} eq "rip") {
 304                 sprintf "%s[%s]",$szmap{$sz},$self->{label};
 305             } else {
 306                 sprintf "%s[%s%s]",$szmap{$sz},
 307                                         $self->{label}?"$self->{label}+":"",
 308                                         $self->{base};
 309             }
 310         }
 311     }
 312 }
 313 { package register;     # pick up registers, which start with %.
 314     sub re {
 315         my      $class = shift; # muliple instances...
 316         my      $self = {};
 317         local   *line = shift;
 318         undef   $ret;
 319
 320         # optional * ---vvv--- appears in indirect jmp/call
 321         if ($line =~ /^(\*?)%(\w+)/) {
 322             bless $self,$class;
 323             $self->{asterisk} = $1;
 324             $self->{value} = $2;
 325             $ret = $self;
 326             $line = substr($line,@+[0]); $line =~ s/^\s+//;
 327         }
 328         $ret;
 329     }
 330     sub size {
 331         my      $self = shift;
 332         undef   $ret;
 333
 334         if    ($self->{value} =~ /^r[\d]+b$/i)  { $ret="b"; }
 335         elsif ($self->{value} =~ /^r[\d]+w$/i)  { $ret="w"; }
 336         elsif ($self->{value} =~ /^r[\d]+d$/i)  { $ret="l"; }
 337         elsif ($self->{value} =~ /^r[\w]+$/i)   { $ret="q"; }
 338         elsif ($self->{value} =~ /^[a-d][hl]$/i){ $ret="b"; }
 339         elsif ($self->{value} =~ /^[\w]{2}l$/i) { $ret="b"; }
 340         elsif ($self->{value} =~ /^[\w]{2}$/i)  { $ret="w"; }
 341         elsif ($self->{value} =~ /^e[a-z]{2}$/i){ $ret="l"; }
 342
 343         $ret;
 344     }
 345     sub out {
 346         my $self = shift;
 347         if ($gas)       { sprintf "%s%%%s",$self->{asterisk},$self->{value}; }
 348         else            { $self->{value}; }
 349     }
 350 }
 351 { package label;        # pick up labels, which end with :
 352     sub re {
 353         my      $self = shift;  # single instance is enough...
 354         local   *line = shift;
 355         undef   $ret;
 356
 357         if ($line =~ /(^[\.\w]+)\:/) {
 358             $self->{value} = $1;
 359             $ret = $self;
 360             $line = substr($line,@+[0]); $line =~ s/^\s+//;
 361
 362             $self->{value} =~ s/^\.L/$decor/;
 363         }
 364         $ret;
 365     }
 366     sub out {
 367         my $self = shift;
 368
 369         if ($gas) {
 370             my $func = ($globals{$self->{value}} or $self->{value}) . ":";
 371             if ($win64  &&
 372                         $current_function->{name} eq $self->{value} &&
 373                         $current_function->{abi} eq "svr4") {
 374                 $func .= "\n";
 375                 $func .= "      movq    %rdi,8(%rsp)\n";
 376                 $func .= "      movq    %rsi,16(%rsp)\n";
 377                 $func .= "      movq    %rsp,%rax\n";
 378                 $func .= "${decor}SEH_begin_$current_function->{name}:\n";
 379                 my $narg = $current_function->{narg};
 380                 $narg=6 if (!defined($narg));
 381                 $func .= "      movq    %rcx,%rdi\n" if ($narg>0);
 382                 $func .= "      movq    %rdx,%rsi\n" if ($narg>1);
 383                 $func .= "      movq    %r8,%rdx\n"  if ($narg>2);
 384                 $func .= "      movq    %r9,%rcx\n"  if ($narg>3);
 385                 $func .= "      movq    40(%rsp),%r8\n" if ($narg>4);
 386                 $func .= "      movq    48(%rsp),%r9\n" if ($narg>5);
 387             }
 388             $func;
 389         } elsif ($self->{value} ne "$current_function->{name}") {
 390             $self->{value} .= ":" if ($masm && $ret!~m/^\$/);
 391             $self->{value} . ":";
 392         } elsif ($win64 && $current_function->{abi} eq "svr4") {
 393             my $func =  "$current_function->{name}" .
 394                         ($nasm ? ":" : "\tPROC $current_function->{scope}") .
 395                         "\n";
 396             $func .= "  mov     QWORD${PTR}[8+rsp],rdi\t;WIN64 prologue\n";
 397             $func .= "  mov     QWORD${PTR}[16+rsp],rsi\n";
 398             $func .= "  mov     rax,rsp\n";
 399             $func .= "${decor}SEH_begin_$current_function->{name}:";
 400             $func .= ":" if ($masm);
 401             $func .= "\n";
 402             my $narg = $current_function->{narg};
 403             $narg=6 if (!defined($narg));
 404             $func .= "  mov     rdi,rcx\n" if ($narg>0);
 405             $func .= "  mov     rsi,rdx\n" if ($narg>1);
 406             $func .= "  mov     rdx,r8\n"  if ($narg>2);
 407             $func .= "  mov     rcx,r9\n"  if ($narg>3);
 408             $func .= "  mov     r8,QWORD${PTR}[40+rsp]\n" if ($narg>4);
 409             $func .= "  mov     r9,QWORD${PTR}[48+rsp]\n" if ($narg>5);
 410             $func .= "\n";
 411         } else {
 412            "$current_function->{name}".
 413                         ($nasm ? ":" : "\tPROC $current_function->{scope}");
 414         }
 415     }
 416 }
 417 { package expr;         # pick up expressioins
 418     sub re {
 419         my      $self = shift;  # single instance is enough...
 420         local   *line = shift;
 421         undef   $ret;
 422
 423         if ($line =~ /(^[^,]+)/) {
 424             $self->{value} = $1;
 425             $ret = $self;
 426             $line = substr($line,@+[0]); $line =~ s/^\s+//;
 427
 428             $self->{value} =~ s/\@PLT// if (!$elf);
 429             $self->{value} =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
 430             $self->{value} =~ s/\.L/$decor/g;
 431         }
 432         $ret;
 433     }
 434     sub out {
 435         my $self = shift;
 436         if ($nasm && opcode->mnemonic()=~m/^j(?![re]cxz)/) {
 437             "NEAR ".$self->{value};
 438         } else {
 439             $self->{value};
 440         }
 441     }
 442 }
 443 { package directive;    # pick up directives, which start with .
 444     sub re {
 445         my      $self = shift;  # single instance is enough...
 446         local   *line = shift;
 447         undef   $ret;
 448         my      $dir;
 449         my      %opcode =       # lea 2f-1f(%rip),%dst; 1: nop; 2:
 450                 (       "%rax"=>0x01058d48,     "%rcx"=>0x010d8d48,
 451                         "%rdx"=>0x01158d48,     "%rbx"=>0x011d8d48,
 452                         "%rsp"=>0x01258d48,     "%rbp"=>0x012d8d48,
 453                         "%rsi"=>0x01358d48,     "%rdi"=>0x013d8d48,
 454                         "%r8" =>0x01058d4c,     "%r9" =>0x010d8d4c,
 455                         "%r10"=>0x01158d4c,     "%r11"=>0x011d8d4c,
 456                         "%r12"=>0x01258d4c,     "%r13"=>0x012d8d4c,
 457                         "%r14"=>0x01358d4c,     "%r15"=>0x013d8d4c      );
 458
 459         if ($line =~ /^\s*(\.\w+)/) {
 460             $dir = $1;
 461             $ret = $self;
 462             undef $self->{value};
 463             $line = substr($line,@+[0]); $line =~ s/^\s+//;
 464
 465             SWITCH: for ($dir) {
 466                 /\.picmeup/ && do { if ($line =~ /(%r[\w]+)/i) {
 467                                         $dir="\t.long";
 468                                         $line=sprintf "0x%x,0x90000000",$opcode{$1};
 469                                     }
 470                                     last;
 471                                   };
 472                 /\.global|\.globl|\.extern/
 473                             && do { $globals{$line} = $prefix . $line;
 474                                     $line = $globals{$line} if ($prefix);
 475                                     last;
 476                                   };
 477                 /\.type/    && do { ($sym,$type,$narg) = split(',',$line);
 478                                     if ($type eq "\@function") {
 479                                         undef $current_function;
 480                                         $current_function->{name} = $sym;
 481                                         $current_function->{abi}  = "svr4";
 482                                         $current_function->{narg} = $narg;
 483                                         $current_function->{scope} = defined($globals{$sym})?"PUBLIC":"PRIVATE";
 484                                     } elsif ($type eq "\@abi-omnipotent") {
 485                                         undef $current_function;
 486                                         $current_function->{name} = $sym;
 487                                         $current_function->{scope} = defined($globals{$sym})?"PUBLIC":"PRIVATE";
 488                                     }
 489                                     $line =~ s/\@abi\-omnipotent/\@function/;
 490                                     $line =~ s/\@function.*/\@function/;
 491                                     last;
 492                                   };
 493                 /\.asciz/   && do { if ($line =~ /^"(.*)"$/) {
 494                                         $dir  = ".byte";
 495                                         $line = join(",",unpack("C*",$1),0);
 496                                     }
 497                                     last;
 498                                   };
 499                 /\.rva|\.long|\.quad/
 500                             && do { $line =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
 501                                     $line =~ s/\.L/$decor/g;
 502                                     last;
 503                                   };
 504             }
 505
 506             if ($gas) {
 507                 $self->{value} = $dir . "\t" . $line;
 508
 509                 if ($dir =~ /\.extern/) {
 510                     $self->{value} = ""; # swallow extern
 511                 } elsif (!$elf && $dir =~ /\.type/) {
 512                     $self->{value} = "";
 513                     $self->{value} = ".def\t" . ($globals{$1} or $1) . ";\t" .
 514                                 (defined($globals{$1})?".scl 2;":".scl 3;") .
 515                                 "\t.type 32;\t.endef"
 516                                 if ($win64 && $line =~ /([^,]+),\@function/);
 517                 } elsif (!$elf && $dir =~ /\.size/) {
 518                     $self->{value} = "";
 519                     if (defined($current_function)) {
 520                         $self->{value} .= "${decor}SEH_end_$current_function->{name}:"
 521                                 if ($win64 && $current_function->{abi} eq "svr4");
 522                         undef $current_function;
 523                     }
 524                 } elsif (!$elf && $dir =~ /\.align/) {
 525                     $self->{value} = ".p2align\t" . (log($line)/log(2));
 526                 } elsif ($dir eq ".section") {
 527                     $current_segment=$line;
 528                     if (!$elf && $current_segment eq ".init") {
 529                         if      ($flavour eq "macosx")  { $self->{value} = ".mod_init_func"; }
 530                         elsif   ($flavour eq "mingw64") { $self->{value} = ".section\t.ctors"; }
 531                     }
 532                 } elsif ($dir =~ /\.(text|data)/) {
 533                     $current_segment=".$1";
 534                 } elsif ($dir =~ /\.hidden/) {
 535                     if    ($flavour eq "macosx")  { $self->{value} = ".private_extern\t$prefix$line"; }
 536                     elsif ($flavour eq "mingw64") { $self->{value} = ""; }
 537                 } elsif ($dir =~ /\.comm/) {
 538                     $self->{value} = "$dir\t$prefix$line";
 539                     $self->{value} =~ s|,([0-9]+),([0-9]+)$|",$1,".log($2)/log(2)|e if ($flavour eq "macosx");
 540                 }
 541                 $line = "";
 542                 return $self;
 543             }
 544
 545             # non-gas case or nasm/masm
 546             SWITCH: for ($dir) {
 547                 /\.text/    && do { my $v=undef;
 548                                     if ($nasm) {
 549                                         $v="section     .text code align=64\n";
 550                                     } else {
 551                                         $v="$current_segment\tENDS\n" if ($current_segment);
 552                                         $current_segment = ".text\$";
 553                                         $v.="$current_segment\tSEGMENT ";
 554                                         $v.=$masm>=$masmref ? "ALIGN(256)" : "PAGE";
 555                                         $v.=" 'CODE'";
 556                                     }
 557                                     $self->{value} = $v;
 558                                     last;
 559                                   };
 560                 /\.data/    && do { my $v=undef;
 561                                     if ($nasm) {
 562                                         $v="section     .data data align=8\n";
 563                                     } else {
 564                                         $v="$current_segment\tENDS\n" if ($current_segment);
 565                                         $current_segment = "_DATA";
 566                                         $v.="$current_segment\tSEGMENT";
 567                                     }
 568                                     $self->{value} = $v;
 569                                     last;
 570                                   };
 571                 /\.section/ && do { my $v=undef;
 572                                     $line =~ s/([^,]*).*/$1/;
 573                                     $line = ".CRT\$XCU" if ($line eq ".init");
 574                                     if ($nasm) {
 575                                         $v="section     $line";
 576                                         if ($line=~/\.([px])data/) {
 577                                             $v.=" rdata align=";
 578                                             $v.=$1 eq "p"? 4 : 8;
 579                                         } elsif ($line=~/\.CRT\$/i) {
 580                                             $v.=" rdata align=8";
 581                                         }
 582                                     } else {
 583                                         $v="$current_segment\tENDS\n" if ($current_segment);
 584                                         $v.="$line\tSEGMENT";
 585                                         if ($line=~/\.([px])data/) {
 586                                             $v.=" READONLY";
 587                                             $v.=" ALIGN(".($1 eq "p" ? 4 : 8).")" if ($masm>=$masmref);
 588                                         } elsif ($line=~/\.CRT\$/i) {
 589                                             $v.=" READONLY ";
 590                                             $v.=$masm>=$masmref ? "ALIGN(8)" : "DWORD";
 591                                         }
 592                                     }
 593                                     $current_segment = $line;
 594                                     $self->{value} = $v;
 595                                     last;
 596                                   };
 597                 /\.extern/  && do { $self->{value}  = "EXTERN\t".$line;
 598                                     $self->{value} .= ":NEAR" if ($masm);
 599                                     last;
 600                                   };
 601                 /\.globl|.global/
 602                             && do { $self->{value}  = $masm?"PUBLIC":"global";
 603                                     $self->{value} .= "\t".$line;
 604                                     last;
 605                                   };
 606                 /\.size/    && do { if (defined($current_function)) {
 607                                         undef $self->{value};
 608                                         if ($current_function->{abi} eq "svr4") {
 609                                             $self->{value}="${decor}SEH_end_$current_function->{name}:";
 610                                             $self->{value}.=":\n" if($masm);
 611                                         }
 612                                         $self->{value}.="$current_function->{name}\tENDP" if($masm && $current_function->{name});
 613                                         undef $current_function;
 614                                     }
 615                                     last;
 616                                   };
 617                 /\.align/   && do { $self->{value} = "ALIGN\t".$line; last; };
 618                 /\.(value|long|rva|quad)/
 619                             && do { my $sz  = substr($1,0,1);
 620                                     my @arr = split(/,\s*/,$line);
 621                                     my $last = pop(@arr);
 622                                     my $conv = sub  {   my $var=shift;
 623                                                         $var=~s/^(0b[0-1]+)/oct($1)/eig;
 624                                                         $var=~s/^0x([0-9a-f]+)/0$1h/ig if ($masm);
 625                                                         if ($sz eq "D" && ($current_segment=~/.[px]data/ || $dir eq ".rva"))
 626                                                         { $var=~s/([_a-z\$\@][_a-z0-9\$\@]*)/$nasm?"$1 wrt ..imagebase":"imagerel $1"/egi; }
 627                                                         $var;
 628                                                     };
 629
 630                                     $sz =~ tr/bvlrq/BWDDQ/;
 631                                     $self->{value} = "\tD$sz\t";
 632                                     for (@arr) { $self->{value} .= &$conv($_).","; }
 633                                     $self->{value} .= &$conv($last);
 634                                     last;
 635                                   };
 636                 /\.byte/    && do { my @str=split(/,\s*/,$line);
 637                                     map(s/(0b[0-1]+)/oct($1)/eig,@str);
 638                                     map(s/0x([0-9a-f]+)/0$1h/ig,@str) if ($masm);
 639                                     while ($#str>15) {
 640                                         $self->{value}.="DB\t"
 641                                                 .join(",",@str[0..15])."\n";
 642                                         foreach (0..15) { shift @str; }
 643                                     }
 644                                     $self->{value}.="DB\t"
 645                                                 .join(",",@str) if (@str);
 646                                     last;
 647                                   };
 648                 /\.comm/    && do { my @str=split(/,\s*/,$line);
 649                                     my $v=undef;
 650                                     if ($nasm) {
 651                                         $v.="common     $prefix@str[0] @str[1]";
 652                                     } else {
 653                                         $v="$current_segment\tENDS\n" if ($current_segment);
 654                                         $current_segment = "_DATA";
 655                                         $v.="$current_segment\tSEGMENT\n";
 656                                         $v.="COMM       @str[0]:DWORD:".@str[1]/4;
 657                                     }
 658                                     $self->{value} = $v;
 659                                     last;
 660                                   };
 661             }
 662             $line = "";
 663         }
 664
 665         $ret;
 666     }
 667     sub out {
 668         my $self = shift;
 669         $self->{value};
 670     }
 671 }
 672
 673 sub rex {
 674  local *opcode=shift;
 675  my ($dst,$src,$rex)=@_;
 676
 677    $rex|=0x04 if($dst>=8);
 678    $rex|=0x01 if($src>=8);
 679    push @opcode,($rex|0x40) if ($rex);
 680 }
 681
 682 # older gas and ml64 don't handle SSE>2 instructions
 683 my %regrm = (   "%eax"=>0, "%ecx"=>1, "%edx"=>2, "%ebx"=>3,
 684                 "%esp"=>4, "%ebp"=>5, "%esi"=>6, "%edi"=>7      );
 685
 686 my $movq = sub {        # elderly gas can't handle inter-register movq
 687   my $arg = shift;
 688   my @opcode=(0x66);
 689     if ($arg =~ /%xmm([0-9]+),\s*%r(\w+)/) {
 690         my ($src,$dst)=($1,$2);
 691         if ($dst !~ /[0-9]+/)   { $dst = $regrm{"%e$dst"}; }
 692         rex(\@opcode,$src,$dst,0x8);
 693         push @opcode,0x0f,0x7e;
 694         push @opcode,0xc0|(($src&7)<<3)|($dst&7);       # ModR/M
 695         @opcode;
 696     } elsif ($arg =~ /%r(\w+),\s*%xmm([0-9]+)/) {
 697         my ($src,$dst)=($2,$1);
 698         if ($dst !~ /[0-9]+/)   { $dst = $regrm{"%e$dst"}; }
 699         rex(\@opcode,$src,$dst,0x8);
 700         push @opcode,0x0f,0x6e;
 701         push @opcode,0xc0|(($src&7)<<3)|($dst&7);       # ModR/M
 702         @opcode;
 703     } else {
 704         ();
 705     }
 706 };
 707
 708 my $pextrd = sub {
 709     if (shift =~ /\$([0-9]+),\s*%xmm([0-9]+),\s*(%\w+)/) {
 710       my @opcode=(0x66);
 711         $imm=$1;
 712         $src=$2;
 713         $dst=$3;
 714         if ($dst =~ /%r([0-9]+)d/)      { $dst = $1; }
 715         elsif ($dst =~ /%e/)            { $dst = $regrm{$dst}; }
 716         rex(\@opcode,$src,$dst);
 717         push @opcode,0x0f,0x3a,0x16;
 718         push @opcode,0xc0|(($src&7)<<3)|($dst&7);       # ModR/M
 719         push @opcode,$imm;
 720         @opcode;
 721     } else {
 722         ();
 723     }
 724 };
 725
 726 my $pinsrd = sub {
 727     if (shift =~ /\$([0-9]+),\s*(%\w+),\s*%xmm([0-9]+)/) {
 728       my @opcode=(0x66);
 729         $imm=$1;
 730         $src=$2;
 731         $dst=$3;
 732         if ($src =~ /%r([0-9]+)/)       { $src = $1; }
 733         elsif ($src =~ /%e/)            { $src = $regrm{$src}; }
 734         rex(\@opcode,$dst,$src);
 735         push @opcode,0x0f,0x3a,0x22;
 736         push @opcode,0xc0|(($dst&7)<<3)|($src&7);       # ModR/M
 737         push @opcode,$imm;
 738         @opcode;
 739     } else {
 740         ();
 741     }
 742 };
 743
 744 my $pshufb = sub {
 745     if (shift =~ /%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 746       my @opcode=(0x66);
 747         rex(\@opcode,$2,$1);
 748         push @opcode,0x0f,0x38,0x00;
 749         push @opcode,0xc0|($1&7)|(($2&7)<<3);           # ModR/M
 750         @opcode;
 751     } else {
 752         ();
 753     }
 754 };
 755
 756 my $palignr = sub {
 757     if (shift =~ /\$([0-9]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 758       my @opcode=(0x66);
 759         rex(\@opcode,$3,$2);
 760         push @opcode,0x0f,0x3a,0x0f;
 761         push @opcode,0xc0|($2&7)|(($3&7)<<3);           # ModR/M
 762         push @opcode,$1;
 763         @opcode;
 764     } else {
 765         ();
 766     }
 767 };
 768
 769 my $pclmulqdq = sub {
 770     if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 771       my @opcode=(0x66);
 772         rex(\@opcode,$3,$2);
 773         push @opcode,0x0f,0x3a,0x44;
 774         push @opcode,0xc0|($2&7)|(($3&7)<<3);           # ModR/M
 775         my $c=$1;
 776         push @opcode,$c=~/^0/?oct($c):$c;
 777         @opcode;
 778     } else {
 779         ();
 780     }
 781 };
 782
 783 my $rdrand = sub {
 784     if (shift =~ /%[er](\w+)/) {
 785       my @opcode=();
 786       my $dst=$1;
 787         if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
 788         rex(\@opcode,0,$1,8);
 789         push @opcode,0x0f,0xc7,0xf0|($dst&7);
 790         @opcode;
 791     } else {
 792         ();
 793     }
 794 };
 795
 796 my $rdseed = sub {
 797     if (shift =~ /%[er](\w+)/) {
 798       my @opcode=();
 799       my $dst=$1;
 800         if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
 801         rex(\@opcode,0,$1,8);
 802         push @opcode,0x0f,0xc7,0xf8|($dst&7);
 803         @opcode;
 804     } else {
 805         ();
 806     }
 807 };
 808
 809 sub rxb {
 810  local *opcode=shift;
 811  my ($dst,$src1,$src2,$rxb)=@_;
 812
 813    $rxb|=0x7<<5;
 814    $rxb&=~(0x04<<5) if($dst>=8);
 815    $rxb&=~(0x01<<5) if($src1>=8);
 816    $rxb&=~(0x02<<5) if($src2>=8);
 817    push @opcode,$rxb;
 818 }
 819
 820 my $vprotd = sub {
 821     if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 822       my @opcode=(0x8f);
 823         rxb(\@opcode,$3,$2,-1,0x08);
 824         push @opcode,0x78,0xc2;
 825         push @opcode,0xc0|($2&7)|(($3&7)<<3);           # ModR/M
 826         my $c=$1;
 827         push @opcode,$c=~/^0/?oct($c):$c;
 828         @opcode;
 829     } else {
 830         ();
 831     }
 832 };
 833
 834 my $vprotq = sub {
 835     if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
 836       my @opcode=(0x8f);
 837         rxb(\@opcode,$3,$2,-1,0x08);
 838         push @opcode,0x78,0xc3;
 839         push @opcode,0xc0|($2&7)|(($3&7)<<3);           # ModR/M
 840         my $c=$1;
 841         push @opcode,$c=~/^0/?oct($c):$c;
 842         @opcode;
 843     } else {
 844         ();
 845     }
 846 };
 847
 848 if ($nasm) {
 849     print <<___;
 850 default rel
 851 %define XMMWORD
 852 %define YMMWORD
 853 %define ZMMWORD
 854 ___
 855 } elsif ($masm) {
 856     print <<___;
 857 OPTION  DOTNAME
 858 ___
 859 }
 860 while($line=<>) {
 861
 862     chomp($line);
 863
 864     $line =~ s|[#!].*$||;       # get rid of asm-style comments...
 865     $line =~ s|/\*.*\*/||;      # ... and C-style comments...
 866     $line =~ s|^\s+||;          # ... and skip white spaces in beginning
 867     $line =~ s|\s+$||;          # ... and at the end
 868
 869     undef $label;
 870     undef $opcode;
 871     undef @args;
 872
 873     if ($label=label->re(\$line))       { print $label->out(); }
 874
 875     if (directive->re(\$line)) {
 876         printf "%s",directive->out();
 877     } elsif ($opcode=opcode->re(\$line)) {
 878         my $asm = eval("\$".$opcode->mnemonic());
 879         undef @bytes;
 880
 881         if ((ref($asm) eq 'CODE') && scalar(@bytes=&$asm($line))) {
 882             print $gas?".byte\t":"DB\t",join(',',@bytes),"\n";
 883             next;
 884         }
 885
 886         ARGUMENT: while (1) {
 887         my $arg;
 888
 889         if ($arg=register->re(\$line))  { opcode->size($arg->size()); }
 890         elsif ($arg=const->re(\$line))  { }
 891         elsif ($arg=ea->re(\$line))     { }
 892         elsif ($arg=expr->re(\$line))   { }
 893         else                            { last ARGUMENT; }
 894
 895         push @args,$arg;
 896
 897         last ARGUMENT if ($line !~ /^,/);
 898
 899         $line =~ s/^,\s*//;
 900         } # ARGUMENT:
 901
 902         if ($#args>=0) {
 903             my $insn;
 904             my $sz=opcode->size();
 905
 906             if ($gas) {
 907                 $insn = $opcode->out($#args>=1?$args[$#args]->size():$sz);
 908                 @args = map($_->out($sz),@args);
 909                 printf "\t%s\t%s",$insn,join(",",@args);
 910             } else {
 911                 $insn = $opcode->out();
 912                 foreach (@args) {
 913                     my $arg = $_->out();
 914                     # $insn.=$sz compensates for movq, pinsrw, ...
 915                     if ($arg =~ /^xmm[0-9]+$/) { $insn.=$sz; $sz="x" if(!$sz); last; }
 916                     if ($arg =~ /^ymm[0-9]+$/) { $insn.=$sz; $sz="y" if(!$sz); last; }
 917                     if ($arg =~ /^zmm[0-9]+$/) { $insn.=$sz; $sz="z" if(!$sz); last; }
 918                     if ($arg =~ /^mm[0-9]+$/)  { $insn.=$sz; $sz="q" if(!$sz); last; }
 919                 }
 920                 @args = reverse(@args);
 921                 undef $sz if ($nasm && $opcode->mnemonic() eq "lea");
 922                 printf "\t%s\t%s",$insn,join(",",map($_->out($sz),@args));
 923             }
 924         } else {
 925             printf "\t%s",$opcode->out();
 926         }
 927     }
 928
 929     print $line,"\n";
 930 }
 931
 932 print "\n$current_segment\tENDS\n"      if ($current_segment && $masm);
 933 print "END\n"                           if ($masm);
 934
 935 close STDOUT;
 936
 937 \f#################################################
 938 # Cross-reference x86_64 ABI "card"
 939 #
 940 #               Unix            Win64
 941 # %rax          *               *
 942 # %rbx          -               -
 943 # %rcx          #4              #1
 944 # %rdx          #3              #2
 945 # %rsi          #2              -
 946 # %rdi          #1              -
 947 # %rbp          -               -
 948 # %rsp          -               -
 949 # %r8           #5              #3
 950 # %r9           #6              #4
 951 # %r10          *               *
 952 # %r11          *               *
 953 # %r12          -               -
 954 # %r13          -               -
 955 # %r14          -               -
 956 # %r15          -               -
 957 #
 958 # (*)   volatile register
 959 # (-)   preserved by callee
 960 # (#)   Nth argument, volatile
 961 #
 962 # In Unix terms top of stack is argument transfer area for arguments
 963 # which could not be accomodated in registers. Or in other words 7th
 964 # [integer] argument resides at 8(%rsp) upon function entry point.
 965 # 128 bytes above %rsp constitute a "red zone" which is not touched
 966 # by signal handlers and can be used as temporal storage without
 967 # allocating a frame.
 968 #
 969 # In Win64 terms N*8 bytes on top of stack is argument transfer area,
 970 # which belongs to/can be overwritten by callee. N is the number of
 971 # arguments passed to callee, *but* not less than 4! This means that
 972 # upon function entry point 5th argument resides at 40(%rsp), as well
 973 # as that 32 bytes from 8(%rsp) can always be used as temporal
 974 # storage [without allocating a frame]. One can actually argue that
 975 # one can assume a "red zone" above stack pointer under Win64 as well.
 976 # Point is that at apparently no occasion Windows kernel would alter
 977 # the area above user stack pointer in true asynchronous manner...
 978 #
 979 # All the above means that if assembler programmer adheres to Unix
 980 # register and stack layout, but disregards the "red zone" existense,
 981 # it's possible to use following prologue and epilogue to "gear" from
 982 # Unix to Win64 ABI in leaf functions with not more than 6 arguments.
 983 #
 984 # omnipotent_function:
 985 # ifdef WIN64
 986 #       movq    %rdi,8(%rsp)
 987 #       movq    %rsi,16(%rsp)
 988 #       movq    %rcx,%rdi       ; if 1st argument is actually present
 989 #       movq    %rdx,%rsi       ; if 2nd argument is actually ...
 990 #       movq    %r8,%rdx        ; if 3rd argument is ...
 991 #       movq    %r9,%rcx        ; if 4th argument ...
 992 #       movq    40(%rsp),%r8    ; if 5th ...
 993 #       movq    48(%rsp),%r9    ; if 6th ...
 994 # endif
 995 #       ...
 996 # ifdef WIN64
 997 #       movq    8(%rsp),%rdi
 998 #       movq    16(%rsp),%rsi
 999 # endif
1000 #       ret
1001 #
1002 \f#################################################
1003 # Win64 SEH, Structured Exception Handling.
1004 #
1005 # Unlike on Unix systems(*) lack of Win64 stack unwinding information
1006 # has undesired side-effect at run-time: if an exception is raised in
1007 # assembler subroutine such as those in question (basically we're
1008 # referring to segmentation violations caused by malformed input
1009 # parameters), the application is briskly terminated without invoking
1010 # any exception handlers, most notably without generating memory dump
1011 # or any user notification whatsoever. This poses a problem. It's
1012 # possible to address it by registering custom language-specific
1013 # handler that would restore processor context to the state at
1014 # subroutine entry point and return "exception is not handled, keep
1015 # unwinding" code. Writing such handler can be a challenge... But it's
1016 # doable, though requires certain coding convention. Consider following
1017 # snippet:
1018 #
1019 # .type function,@function
1020 # function:
1021 #       movq    %rsp,%rax       # copy rsp to volatile register
1022 #       pushq   %r15            # save non-volatile registers
1023 #       pushq   %rbx
1024 #       pushq   %rbp
1025 #       movq    %rsp,%r11
1026 #       subq    %rdi,%r11       # prepare [variable] stack frame
1027 #       andq    $-64,%r11
1028 #       movq    %rax,0(%r11)    # check for exceptions
1029 #       movq    %r11,%rsp       # allocate [variable] stack frame
1030 #       movq    %rax,0(%rsp)    # save original rsp value
1031 # magic_point:
1032 #       ...
1033 #       movq    0(%rsp),%rcx    # pull original rsp value
1034 #       movq    -24(%rcx),%rbp  # restore non-volatile registers
1035 #       movq    -16(%rcx),%rbx
1036 #       movq    -8(%rcx),%r15
1037 #       movq    %rcx,%rsp       # restore original rsp
1038 #       ret
1039 # .size function,.-function
1040 #
1041 # The key is that up to magic_point copy of original rsp value remains
1042 # in chosen volatile register and no non-volatile register, except for
1043 # rsp, is modified. While past magic_point rsp remains constant till
1044 # the very end of the function. In this case custom language-specific
1045 # exception handler would look like this:
1046 #
1047 # EXCEPTION_DISPOSITION handler (EXCEPTION_RECORD *rec,ULONG64 frame,
1048 #               CONTEXT *context,DISPATCHER_CONTEXT *disp)
1049 # {     ULONG64 *rsp = (ULONG64 *)context->Rax;
1050 #       if (context->Rip >= magic_point)
1051 #       {   rsp = ((ULONG64 **)context->Rsp)[0];
1052 #           context->Rbp = rsp[-3];
1053 #           context->Rbx = rsp[-2];
1054 #           context->R15 = rsp[-1];
1055 #       }
1056 #       context->Rsp = (ULONG64)rsp;
1057 #       context->Rdi = rsp[1];
1058 #       context->Rsi = rsp[2];
1059 #
1060 #       memcpy (disp->ContextRecord,context,sizeof(CONTEXT));
1061 #       RtlVirtualUnwind(UNW_FLAG_NHANDLER,disp->ImageBase,
1062 #               dips->ControlPc,disp->FunctionEntry,disp->ContextRecord,
1063 #               &disp->HandlerData,&disp->EstablisherFrame,NULL);
1064 #       return ExceptionContinueSearch;
1065 # }
1066 #
1067 # It's appropriate to implement this handler in assembler, directly in
1068 # function's module. In order to do that one has to know members'
1069 # offsets in CONTEXT and DISPATCHER_CONTEXT structures and some constant
1070 # values. Here they are:
1071 #
1072 #       CONTEXT.Rax                             120
1073 #       CONTEXT.Rcx                             128
1074 #       CONTEXT.Rdx                             136
1075 #       CONTEXT.Rbx                             144
1076 #       CONTEXT.Rsp                             152
1077 #       CONTEXT.Rbp                             160
1078 #       CONTEXT.Rsi                             168
1079 #       CONTEXT.Rdi                             176
1080 #       CONTEXT.R8                              184
1081 #       CONTEXT.R9                              192
1082 #       CONTEXT.R10                             200
1083 #       CONTEXT.R11                             208
1084 #       CONTEXT.R12                             216
1085 #       CONTEXT.R13                             224
1086 #       CONTEXT.R14                             232
1087 #       CONTEXT.R15                             240
1088 #       CONTEXT.Rip                             248
1089 #       CONTEXT.Xmm6                            512
1090 #       sizeof(CONTEXT)                         1232
1091 #       DISPATCHER_CONTEXT.ControlPc            0
1092 #       DISPATCHER_CONTEXT.ImageBase            8
1093 #       DISPATCHER_CONTEXT.FunctionEntry        16
1094 #       DISPATCHER_CONTEXT.EstablisherFrame     24
1095 #       DISPATCHER_CONTEXT.TargetIp             32
1096 #       DISPATCHER_CONTEXT.ContextRecord        40
1097 #       DISPATCHER_CONTEXT.LanguageHandler      48
1098 #       DISPATCHER_CONTEXT.HandlerData          56
1099 #       UNW_FLAG_NHANDLER                       0
1100 #       ExceptionContinueSearch                 1
1101 #
1102 # In order to tie the handler to the function one has to compose
1103 # couple of structures: one for .xdata segment and one for .pdata.
1104 #
1105 # UNWIND_INFO structure for .xdata segment would be
1106 #
1107 # function_unwind_info:
1108 #       .byte   9,0,0,0
1109 #       .rva    handler
1110 #
1111 # This structure designates exception handler for a function with
1112 # zero-length prologue, no stack frame or frame register.
1113 #
1114 # To facilitate composing of .pdata structures, auto-generated "gear"
1115 # prologue copies rsp value to rax and denotes next instruction with
1116 # .LSEH_begin_{function_name} label. This essentially defines the SEH
1117 # styling rule mentioned in the beginning. Position of this label is
1118 # chosen in such manner that possible exceptions raised in the "gear"
1119 # prologue would be accounted to caller and unwound from latter's frame.
1120 # End of function is marked with respective .LSEH_end_{function_name}
1121 # label. To summarize, .pdata segment would contain
1122 #
1123 #       .rva    .LSEH_begin_function
1124 #       .rva    .LSEH_end_function
1125 #       .rva    function_unwind_info
1126 #
1127 # Reference to functon_unwind_info from .xdata segment is the anchor.
1128 # In case you wonder why references are 32-bit .rvas and not 64-bit
1129 # .quads. References put into these two segments are required to be
1130 # *relative* to the base address of the current binary module, a.k.a.
1131 # image base. No Win64 module, be it .exe or .dll, can be larger than
1132 # 2GB and thus such relative references can be and are accommodated in
1133 # 32 bits.
1134 #
1135 # Having reviewed the example function code, one can argue that "movq
1136 # %rsp,%rax" above is redundant. It is not! Keep in mind that on Unix
1137 # rax would contain an undefined value. If this "offends" you, use
1138 # another register and refrain from modifying rax till magic_point is
1139 # reached, i.e. as if it was a non-volatile register. If more registers
1140 # are required prior [variable] frame setup is completed, note that
1141 # nobody says that you can have only one "magic point." You can
1142 # "liberate" non-volatile registers by denoting last stack off-load
1143 # instruction and reflecting it in finer grade unwind logic in handler.
1144 # After all, isn't it why it's called *language-specific* handler...
1145 #
1146 # Attentive reader can notice that exceptions would be mishandled in
1147 # auto-generated "gear" epilogue. Well, exception effectively can't
1148 # occur there, because if memory area used by it was subject to
1149 # segmentation violation, then it would be raised upon call to the
1150 # function (and as already mentioned be accounted to caller, which is
1151 # not a problem). If you're still not comfortable, then define tail
1152 # "magic point" just prior ret instruction and have handler treat it...
1153 #
1154 # (*)   Note that we're talking about run-time, not debug-time. Lack of
1155 #       unwind information makes debugging hard on both Windows and
1156 #       Unix. "Unlike" referes to the fact that on Unix signal handler
1157 #       will always be invoked, core dumped and appropriate exit code
1158 #       returned to parent (for user notification).