1148 lines
35 KiB
Perl
Executable file
1148 lines
35 KiB
Perl
Executable file
#!/usr/bin/env perl
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# Ascetic x86_64 AT&T to MASM/NASM assembler translator by <appro>.
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#
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# Why AT&T to MASM and not vice versa? Several reasons. Because AT&T
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# format is way easier to parse. Because it's simpler to "gear" from
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# Unix ABI to Windows one [see cross-reference "card" at the end of
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# file]. Because Linux targets were available first...
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#
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# In addition the script also "distills" code suitable for GNU
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# assembler, so that it can be compiled with more rigid assemblers,
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# such as Solaris /usr/ccs/bin/as.
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#
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# This translator is not designed to convert *arbitrary* assembler
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# code from AT&T format to MASM one. It's designed to convert just
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# enough to provide for dual-ABI OpenSSL modules development...
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# There *are* limitations and you might have to modify your assembler
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# code or this script to achieve the desired result...
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#
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# Currently recognized limitations:
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#
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# - can't use multiple ops per line;
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#
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# Dual-ABI styling rules.
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#
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# 1. Adhere to Unix register and stack layout [see cross-reference
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# ABI "card" at the end for explanation].
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# 2. Forget about "red zone," stick to more traditional blended
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# stack frame allocation. If volatile storage is actually required
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# that is. If not, just leave the stack as is.
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# 3. Functions tagged with ".type name,@function" get crafted with
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# unified Win64 prologue and epilogue automatically. If you want
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# to take care of ABI differences yourself, tag functions as
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# ".type name,@abi-omnipotent" instead.
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# 4. To optimize the Win64 prologue you can specify number of input
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# arguments as ".type name,@function,N." Keep in mind that if N is
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# larger than 6, then you *have to* write "abi-omnipotent" code,
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# because >6 cases can't be addressed with unified prologue.
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# 5. Name local labels as .L*, do *not* use dynamic labels such as 1:
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# (sorry about latter).
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# 6. Don't use [or hand-code with .byte] "rep ret." "ret" mnemonic is
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# required to identify the spots, where to inject Win64 epilogue!
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# But on the pros, it's then prefixed with rep automatically:-)
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# 7. Stick to explicit ip-relative addressing. If you have to use
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# GOTPCREL addressing, stick to mov symbol@GOTPCREL(%rip),%r??.
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# Both are recognized and translated to proper Win64 addressing
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# modes. To support legacy code a synthetic directive, .picmeup,
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# is implemented. It puts address of the *next* instruction into
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# target register, e.g.:
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#
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# .picmeup %rax
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# lea .Label-.(%rax),%rax
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#
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# 8. In order to provide for structured exception handling unified
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# Win64 prologue copies %rsp value to %rax. For further details
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# see SEH paragraph at the end.
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# 9. .init segment is allowed to contain calls to functions only.
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# a. If function accepts more than 4 arguments *and* >4th argument
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# is declared as non 64-bit value, do clear its upper part.
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my $flavour = shift;
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my $output = shift;
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if ($flavour =~ /\./) { $output = $flavour; undef $flavour; }
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open STDOUT,">$output" || die "can't open $output: $!"
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if (defined($output));
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my $gas=1; $gas=0 if ($output =~ /\.asm$/);
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my $elf=1; $elf=0 if (!$gas);
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my $win64=0;
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my $prefix="";
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my $decor=".L";
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my $masmref=8 + 50727*2**-32; # 8.00.50727 shipped with VS2005
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my $masm=0;
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my $PTR=" PTR";
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my $nasmref=2.03;
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my $nasm=0;
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if ($flavour eq "mingw64") { $gas=1; $elf=0; $win64=1;
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$prefix=`echo __USER_LABEL_PREFIX__ | $ENV{CC} -E -P -`;
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chomp($prefix);
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}
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elsif ($flavour eq "macosx") { $gas=1; $elf=0; $prefix="_"; $decor="L\$"; }
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elsif ($flavour eq "masm") { $gas=0; $elf=0; $masm=$masmref; $win64=1; $decor="\$L\$"; }
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elsif ($flavour eq "nasm") { $gas=0; $elf=0; $nasm=$nasmref; $win64=1; $decor="\$L\$"; $PTR=""; }
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elsif (!$gas)
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{ if ($ENV{ASM} =~ m/nasm/ && `nasm -v` =~ m/version ([0-9]+)\.([0-9]+)/i)
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{ $nasm = $1 + $2*0.01; $PTR=""; }
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elsif (`ml64 2>&1` =~ m/Version ([0-9]+)\.([0-9]+)(\.([0-9]+))?/)
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{ $masm = $1 + $2*2**-16 + $4*2**-32; }
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die "no assembler found on %PATH" if (!($nasm || $masm));
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$win64=1;
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$elf=0;
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$decor="\$L\$";
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}
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my $current_segment;
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my $current_function;
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my %globals;
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{ package opcode; # pick up opcodes
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sub re {
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my $self = shift; # single instance in enough...
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local *line = shift;
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undef $ret;
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if ($line =~ /^([a-z][a-z0-9]*)/i) {
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$self->{op} = $1;
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$ret = $self;
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$line = substr($line,@+[0]); $line =~ s/^\s+//;
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undef $self->{sz};
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if ($self->{op} =~ /^(movz)x?([bw]).*/) { # movz is pain...
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$self->{op} = $1;
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$self->{sz} = $2;
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} elsif ($self->{op} =~ /call|jmp/) {
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$self->{sz} = "";
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} elsif ($self->{op} =~ /^p/ && $' !~ /^(ush|op|insrw)/) { # SSEn
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$self->{sz} = "";
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} elsif ($self->{op} =~ /^v/) { # VEX
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$self->{sz} = "";
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} elsif ($self->{op} =~ /mov[dq]/ && $line =~ /%xmm/) {
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$self->{sz} = "";
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} elsif ($self->{op} =~ /([a-z]{3,})([qlwb])$/) {
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$self->{op} = $1;
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$self->{sz} = $2;
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}
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}
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$ret;
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}
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sub size {
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my $self = shift;
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my $sz = shift;
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$self->{sz} = $sz if (defined($sz) && !defined($self->{sz}));
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$self->{sz};
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}
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sub out {
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my $self = shift;
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if ($gas) {
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if ($self->{op} eq "movz") { # movz is pain...
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sprintf "%s%s%s",$self->{op},$self->{sz},shift;
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} elsif ($self->{op} =~ /^set/) {
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"$self->{op}";
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} elsif ($self->{op} eq "ret") {
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my $epilogue = "";
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if ($win64 && $current_function->{abi} eq "svr4") {
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$epilogue = "movq 8(%rsp),%rdi\n\t" .
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"movq 16(%rsp),%rsi\n\t";
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}
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$epilogue . ".byte 0xf3,0xc3";
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} elsif ($self->{op} eq "call" && !$elf && $current_segment eq ".init") {
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".p2align\t3\n\t.quad";
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} else {
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"$self->{op}$self->{sz}";
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}
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} else {
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$self->{op} =~ s/^movz/movzx/;
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if ($self->{op} eq "ret") {
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$self->{op} = "";
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if ($win64 && $current_function->{abi} eq "svr4") {
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$self->{op} = "mov rdi,QWORD${PTR}[8+rsp]\t;WIN64 epilogue\n\t".
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"mov rsi,QWORD${PTR}[16+rsp]\n\t";
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}
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$self->{op} .= "DB\t0F3h,0C3h\t\t;repret";
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} elsif ($self->{op} =~ /^(pop|push)f/) {
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$self->{op} .= $self->{sz};
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} elsif ($self->{op} eq "call" && $current_segment eq ".CRT\$XCU") {
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$self->{op} = "\tDQ";
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}
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$self->{op};
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}
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}
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sub mnemonic {
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my $self=shift;
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my $op=shift;
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$self->{op}=$op if (defined($op));
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$self->{op};
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}
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}
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{ package const; # pick up constants, which start with $
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sub re {
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my $self = shift; # single instance in enough...
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local *line = shift;
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undef $ret;
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if ($line =~ /^\$([^,]+)/) {
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$self->{value} = $1;
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$ret = $self;
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$line = substr($line,@+[0]); $line =~ s/^\s+//;
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}
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$ret;
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}
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sub out {
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my $self = shift;
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if ($gas) {
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# Solaris /usr/ccs/bin/as can't handle multiplications
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# in $self->{value}
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$self->{value} =~ s/(?<![\w\$\.])(0x?[0-9a-f]+)/oct($1)/egi;
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$self->{value} =~ s/([0-9]+\s*[\*\/\%]\s*[0-9]+)/eval($1)/eg;
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sprintf "\$%s",$self->{value};
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} else {
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$self->{value} =~ s/(0b[0-1]+)/oct($1)/eig;
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$self->{value} =~ s/0x([0-9a-f]+)/0$1h/ig if ($masm);
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sprintf "%s",$self->{value};
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}
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}
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}
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{ package ea; # pick up effective addresses: expr(%reg,%reg,scale)
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sub re {
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my $self = shift; # single instance in enough...
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local *line = shift;
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undef $ret;
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# optional * ---vvv--- appears in indirect jmp/call
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if ($line =~ /^(\*?)([^\(,]*)\(([%\w,]+)\)/) {
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$self->{asterisk} = $1;
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$self->{label} = $2;
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($self->{base},$self->{index},$self->{scale})=split(/,/,$3);
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$self->{scale} = 1 if (!defined($self->{scale}));
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$ret = $self;
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$line = substr($line,@+[0]); $line =~ s/^\s+//;
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if ($win64 && $self->{label} =~ s/\@GOTPCREL//) {
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die if (opcode->mnemonic() ne "mov");
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opcode->mnemonic("lea");
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}
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$self->{base} =~ s/^%//;
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$self->{index} =~ s/^%// if (defined($self->{index}));
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}
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$ret;
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}
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sub size {}
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sub out {
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my $self = shift;
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my $sz = shift;
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$self->{label} =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
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$self->{label} =~ s/\.L/$decor/g;
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# Silently convert all EAs to 64-bit. This is required for
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# elder GNU assembler and results in more compact code,
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# *but* most importantly AES module depends on this feature!
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$self->{index} =~ s/^[er](.?[0-9xpi])[d]?$/r\1/;
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$self->{base} =~ s/^[er](.?[0-9xpi])[d]?$/r\1/;
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# Solaris /usr/ccs/bin/as can't handle multiplications
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# in $self->{label}, new gas requires sign extension...
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use integer;
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$self->{label} =~ s/(?<![\w\$\.])(0x?[0-9a-f]+)/oct($1)/egi;
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$self->{label} =~ s/\b([0-9]+\s*[\*\/\%]\s*[0-9]+)\b/eval($1)/eg;
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$self->{label} =~ s/\b([0-9]+)\b/$1<<32>>32/eg;
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if (!$self->{label} && $self->{index} && $self->{scale}==1 &&
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$self->{base} =~ /(rbp|r13)/) {
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$self->{base} = $self->{index}; $self->{index} = $1;
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}
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if ($gas) {
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$self->{label} =~ s/^___imp_/__imp__/ if ($flavour eq "mingw64");
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if (defined($self->{index})) {
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sprintf "%s%s(%s,%%%s,%d)",$self->{asterisk},
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$self->{label},
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$self->{base}?"%$self->{base}":"",
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$self->{index},$self->{scale};
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} else {
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sprintf "%s%s(%%%s)", $self->{asterisk},$self->{label},$self->{base};
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}
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} else {
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%szmap = ( b=>"BYTE$PTR", w=>"WORD$PTR",
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l=>"DWORD$PTR", d=>"DWORD$PTR",
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q=>"QWORD$PTR", o=>"OWORD$PTR",
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x=>"XMMWORD$PTR", y=>"YMMWORD$PTR", z=>"ZMMWORD$PTR" );
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$self->{label} =~ s/\./\$/g;
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$self->{label} =~ s/(?<![\w\$\.])0x([0-9a-f]+)/0$1h/ig;
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$self->{label} = "($self->{label})" if ($self->{label} =~ /[\*\+\-\/]/);
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($self->{asterisk}) && ($sz="q") ||
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(opcode->mnemonic() =~ /^v?mov([qd])$/) && ($sz=$1) ||
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(opcode->mnemonic() =~ /^v?pinsr([qdwb])$/) && ($sz=$1) ||
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(opcode->mnemonic() =~ /^vpbroadcast([qdwb])$/) && ($sz=$1) ||
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(opcode->mnemonic() =~ /^vinsert[fi]128$/) && ($sz="x");
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if (defined($self->{index})) {
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sprintf "%s[%s%s*%d%s]",$szmap{$sz},
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$self->{label}?"$self->{label}+":"",
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$self->{index},$self->{scale},
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$self->{base}?"+$self->{base}":"";
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} elsif ($self->{base} eq "rip") {
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sprintf "%s[%s]",$szmap{$sz},$self->{label};
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} else {
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sprintf "%s[%s%s]",$szmap{$sz},
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$self->{label}?"$self->{label}+":"",
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$self->{base};
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}
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}
|
||
}
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||
}
|
||
{ package register; # pick up registers, which start with %.
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sub re {
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my $class = shift; # muliple instances...
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||
my $self = {};
|
||
local *line = shift;
|
||
undef $ret;
|
||
|
||
# optional * ---vvv--- appears in indirect jmp/call
|
||
if ($line =~ /^(\*?)%(\w+)/) {
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bless $self,$class;
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$self->{asterisk} = $1;
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$self->{value} = $2;
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$ret = $self;
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$line = substr($line,@+[0]); $line =~ s/^\s+//;
|
||
}
|
||
$ret;
|
||
}
|
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sub size {
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my $self = shift;
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undef $ret;
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||
|
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if ($self->{value} =~ /^r[\d]+b$/i) { $ret="b"; }
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elsif ($self->{value} =~ /^r[\d]+w$/i) { $ret="w"; }
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elsif ($self->{value} =~ /^r[\d]+d$/i) { $ret="l"; }
|
||
elsif ($self->{value} =~ /^r[\w]+$/i) { $ret="q"; }
|
||
elsif ($self->{value} =~ /^[a-d][hl]$/i){ $ret="b"; }
|
||
elsif ($self->{value} =~ /^[\w]{2}l$/i) { $ret="b"; }
|
||
elsif ($self->{value} =~ /^[\w]{2}$/i) { $ret="w"; }
|
||
elsif ($self->{value} =~ /^e[a-z]{2}$/i){ $ret="l"; }
|
||
|
||
$ret;
|
||
}
|
||
sub out {
|
||
my $self = shift;
|
||
if ($gas) { sprintf "%s%%%s",$self->{asterisk},$self->{value}; }
|
||
else { $self->{value}; }
|
||
}
|
||
}
|
||
{ package label; # pick up labels, which end with :
|
||
sub re {
|
||
my $self = shift; # single instance is enough...
|
||
local *line = shift;
|
||
undef $ret;
|
||
|
||
if ($line =~ /(^[\.\w]+)\:/) {
|
||
$self->{value} = $1;
|
||
$ret = $self;
|
||
$line = substr($line,@+[0]); $line =~ s/^\s+//;
|
||
|
||
$self->{value} =~ s/^\.L/$decor/;
|
||
}
|
||
$ret;
|
||
}
|
||
sub out {
|
||
my $self = shift;
|
||
|
||
if ($gas) {
|
||
my $func = ($globals{$self->{value}} or $self->{value}) . ":";
|
||
if ($win64 &&
|
||
$current_function->{name} eq $self->{value} &&
|
||
$current_function->{abi} eq "svr4") {
|
||
$func .= "\n";
|
||
$func .= " movq %rdi,8(%rsp)\n";
|
||
$func .= " movq %rsi,16(%rsp)\n";
|
||
$func .= " movq %rsp,%rax\n";
|
||
$func .= "${decor}SEH_begin_$current_function->{name}:\n";
|
||
my $narg = $current_function->{narg};
|
||
$narg=6 if (!defined($narg));
|
||
$func .= " movq %rcx,%rdi\n" if ($narg>0);
|
||
$func .= " movq %rdx,%rsi\n" if ($narg>1);
|
||
$func .= " movq %r8,%rdx\n" if ($narg>2);
|
||
$func .= " movq %r9,%rcx\n" if ($narg>3);
|
||
$func .= " movq 40(%rsp),%r8\n" if ($narg>4);
|
||
$func .= " movq 48(%rsp),%r9\n" if ($narg>5);
|
||
}
|
||
$func;
|
||
} elsif ($self->{value} ne "$current_function->{name}") {
|
||
$self->{value} .= ":" if ($masm && $ret!~m/^\$/);
|
||
$self->{value} . ":";
|
||
} elsif ($win64 && $current_function->{abi} eq "svr4") {
|
||
my $func = "$current_function->{name}" .
|
||
($nasm ? ":" : "\tPROC $current_function->{scope}") .
|
||
"\n";
|
||
$func .= " mov QWORD${PTR}[8+rsp],rdi\t;WIN64 prologue\n";
|
||
$func .= " mov QWORD${PTR}[16+rsp],rsi\n";
|
||
$func .= " mov rax,rsp\n";
|
||
$func .= "${decor}SEH_begin_$current_function->{name}:";
|
||
$func .= ":" if ($masm);
|
||
$func .= "\n";
|
||
my $narg = $current_function->{narg};
|
||
$narg=6 if (!defined($narg));
|
||
$func .= " mov rdi,rcx\n" if ($narg>0);
|
||
$func .= " mov rsi,rdx\n" if ($narg>1);
|
||
$func .= " mov rdx,r8\n" if ($narg>2);
|
||
$func .= " mov rcx,r9\n" if ($narg>3);
|
||
$func .= " mov r8,QWORD${PTR}[40+rsp]\n" if ($narg>4);
|
||
$func .= " mov r9,QWORD${PTR}[48+rsp]\n" if ($narg>5);
|
||
$func .= "\n";
|
||
} else {
|
||
"$current_function->{name}".
|
||
($nasm ? ":" : "\tPROC $current_function->{scope}");
|
||
}
|
||
}
|
||
}
|
||
{ package expr; # pick up expressioins
|
||
sub re {
|
||
my $self = shift; # single instance is enough...
|
||
local *line = shift;
|
||
undef $ret;
|
||
|
||
if ($line =~ /(^[^,]+)/) {
|
||
$self->{value} = $1;
|
||
$ret = $self;
|
||
$line = substr($line,@+[0]); $line =~ s/^\s+//;
|
||
|
||
$self->{value} =~ s/\@PLT// if (!$elf);
|
||
$self->{value} =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
|
||
$self->{value} =~ s/\.L/$decor/g;
|
||
}
|
||
$ret;
|
||
}
|
||
sub out {
|
||
my $self = shift;
|
||
if ($nasm && opcode->mnemonic()=~m/^j(?![re]cxz)/) {
|
||
"NEAR ".$self->{value};
|
||
} else {
|
||
$self->{value};
|
||
}
|
||
}
|
||
}
|
||
{ package directive; # pick up directives, which start with .
|
||
sub re {
|
||
my $self = shift; # single instance is enough...
|
||
local *line = shift;
|
||
undef $ret;
|
||
my $dir;
|
||
my %opcode = # lea 2f-1f(%rip),%dst; 1: nop; 2:
|
||
( "%rax"=>0x01058d48, "%rcx"=>0x010d8d48,
|
||
"%rdx"=>0x01158d48, "%rbx"=>0x011d8d48,
|
||
"%rsp"=>0x01258d48, "%rbp"=>0x012d8d48,
|
||
"%rsi"=>0x01358d48, "%rdi"=>0x013d8d48,
|
||
"%r8" =>0x01058d4c, "%r9" =>0x010d8d4c,
|
||
"%r10"=>0x01158d4c, "%r11"=>0x011d8d4c,
|
||
"%r12"=>0x01258d4c, "%r13"=>0x012d8d4c,
|
||
"%r14"=>0x01358d4c, "%r15"=>0x013d8d4c );
|
||
|
||
if ($line =~ /^\s*(\.\w+)/) {
|
||
$dir = $1;
|
||
$ret = $self;
|
||
undef $self->{value};
|
||
$line = substr($line,@+[0]); $line =~ s/^\s+//;
|
||
|
||
SWITCH: for ($dir) {
|
||
/\.picmeup/ && do { if ($line =~ /(%r[\w]+)/i) {
|
||
$dir="\t.long";
|
||
$line=sprintf "0x%x,0x90000000",$opcode{$1};
|
||
}
|
||
last;
|
||
};
|
||
/\.global|\.globl|\.extern/
|
||
&& do { $globals{$line} = $prefix . $line;
|
||
$line = $globals{$line} if ($prefix);
|
||
last;
|
||
};
|
||
/\.type/ && do { ($sym,$type,$narg) = split(',',$line);
|
||
if ($type eq "\@function") {
|
||
undef $current_function;
|
||
$current_function->{name} = $sym;
|
||
$current_function->{abi} = "svr4";
|
||
$current_function->{narg} = $narg;
|
||
$current_function->{scope} = defined($globals{$sym})?"PUBLIC":"PRIVATE";
|
||
} elsif ($type eq "\@abi-omnipotent") {
|
||
undef $current_function;
|
||
$current_function->{name} = $sym;
|
||
$current_function->{scope} = defined($globals{$sym})?"PUBLIC":"PRIVATE";
|
||
}
|
||
$line =~ s/\@abi\-omnipotent/\@function/;
|
||
$line =~ s/\@function.*/\@function/;
|
||
last;
|
||
};
|
||
/\.asciz/ && do { if ($line =~ /^"(.*)"$/) {
|
||
$dir = ".byte";
|
||
$line = join(",",unpack("C*",$1),0);
|
||
}
|
||
last;
|
||
};
|
||
/\.rva|\.long|\.quad/
|
||
&& do { $line =~ s/([_a-z][_a-z0-9]*)/$globals{$1} or $1/gei;
|
||
$line =~ s/\.L/$decor/g;
|
||
last;
|
||
};
|
||
}
|
||
|
||
if ($gas) {
|
||
$self->{value} = $dir . "\t" . $line;
|
||
|
||
if ($dir =~ /\.extern/) {
|
||
$self->{value} = ""; # swallow extern
|
||
} elsif (!$elf && $dir =~ /\.type/) {
|
||
$self->{value} = "";
|
||
$self->{value} = ".def\t" . ($globals{$1} or $1) . ";\t" .
|
||
(defined($globals{$1})?".scl 2;":".scl 3;") .
|
||
"\t.type 32;\t.endef"
|
||
if ($win64 && $line =~ /([^,]+),\@function/);
|
||
} elsif (!$elf && $dir =~ /\.size/) {
|
||
$self->{value} = "";
|
||
if (defined($current_function)) {
|
||
$self->{value} .= "${decor}SEH_end_$current_function->{name}:"
|
||
if ($win64 && $current_function->{abi} eq "svr4");
|
||
undef $current_function;
|
||
}
|
||
} elsif (!$elf && $dir =~ /\.align/) {
|
||
$self->{value} = ".p2align\t" . (log($line)/log(2));
|
||
} elsif ($dir eq ".section") {
|
||
$current_segment=$line;
|
||
if (!$elf && $current_segment eq ".init") {
|
||
if ($flavour eq "macosx") { $self->{value} = ".mod_init_func"; }
|
||
elsif ($flavour eq "mingw64") { $self->{value} = ".section\t.ctors"; }
|
||
}
|
||
} elsif ($dir =~ /\.(text|data)/) {
|
||
$current_segment=".$1";
|
||
} elsif ($dir =~ /\.hidden/) {
|
||
if ($flavour eq "macosx") { $self->{value} = ".private_extern\t$prefix$line"; }
|
||
elsif ($flavour eq "mingw64") { $self->{value} = ""; }
|
||
} elsif ($dir =~ /\.comm/) {
|
||
$self->{value} = "$dir\t$prefix$line";
|
||
$self->{value} =~ s|,([0-9]+),([0-9]+)$|",$1,".log($2)/log(2)|e if ($flavour eq "macosx");
|
||
}
|
||
$line = "";
|
||
return $self;
|
||
}
|
||
|
||
# non-gas case or nasm/masm
|
||
SWITCH: for ($dir) {
|
||
/\.text/ && do { my $v=undef;
|
||
if ($nasm) {
|
||
$v="section .text code align=64\n";
|
||
} else {
|
||
$v="$current_segment\tENDS\n" if ($current_segment);
|
||
$current_segment = ".text\$";
|
||
$v.="$current_segment\tSEGMENT ";
|
||
$v.=$masm>=$masmref ? "ALIGN(256)" : "PAGE";
|
||
$v.=" 'CODE'";
|
||
}
|
||
$self->{value} = $v;
|
||
last;
|
||
};
|
||
/\.data/ && do { my $v=undef;
|
||
if ($nasm) {
|
||
$v="section .data data align=8\n";
|
||
} else {
|
||
$v="$current_segment\tENDS\n" if ($current_segment);
|
||
$current_segment = "_DATA";
|
||
$v.="$current_segment\tSEGMENT";
|
||
}
|
||
$self->{value} = $v;
|
||
last;
|
||
};
|
||
/\.section/ && do { my $v=undef;
|
||
$line =~ s/([^,]*).*/$1/;
|
||
$line = ".CRT\$XCU" if ($line eq ".init");
|
||
if ($nasm) {
|
||
$v="section $line";
|
||
if ($line=~/\.([px])data/) {
|
||
$v.=" rdata align=";
|
||
$v.=$1 eq "p"? 4 : 8;
|
||
} elsif ($line=~/\.CRT\$/i) {
|
||
$v.=" rdata align=8";
|
||
}
|
||
} else {
|
||
$v="$current_segment\tENDS\n" if ($current_segment);
|
||
$v.="$line\tSEGMENT";
|
||
if ($line=~/\.([px])data/) {
|
||
$v.=" READONLY";
|
||
$v.=" ALIGN(".($1 eq "p" ? 4 : 8).")" if ($masm>=$masmref);
|
||
} elsif ($line=~/\.CRT\$/i) {
|
||
$v.=" READONLY ";
|
||
$v.=$masm>=$masmref ? "ALIGN(8)" : "DWORD";
|
||
}
|
||
}
|
||
$current_segment = $line;
|
||
$self->{value} = $v;
|
||
last;
|
||
};
|
||
/\.extern/ && do { $self->{value} = "EXTERN\t".$line;
|
||
$self->{value} .= ":NEAR" if ($masm);
|
||
last;
|
||
};
|
||
/\.globl|.global/
|
||
&& do { $self->{value} = $masm?"PUBLIC":"global";
|
||
$self->{value} .= "\t".$line;
|
||
last;
|
||
};
|
||
/\.size/ && do { if (defined($current_function)) {
|
||
undef $self->{value};
|
||
if ($current_function->{abi} eq "svr4") {
|
||
$self->{value}="${decor}SEH_end_$current_function->{name}:";
|
||
$self->{value}.=":\n" if($masm);
|
||
}
|
||
$self->{value}.="$current_function->{name}\tENDP" if($masm && $current_function->{name});
|
||
undef $current_function;
|
||
}
|
||
last;
|
||
};
|
||
/\.align/ && do { $self->{value} = "ALIGN\t".$line; last; };
|
||
/\.(value|long|rva|quad)/
|
||
&& do { my $sz = substr($1,0,1);
|
||
my @arr = split(/,\s*/,$line);
|
||
my $last = pop(@arr);
|
||
my $conv = sub { my $var=shift;
|
||
$var=~s/^(0b[0-1]+)/oct($1)/eig;
|
||
$var=~s/^0x([0-9a-f]+)/0$1h/ig if ($masm);
|
||
if ($sz eq "D" && ($current_segment=~/.[px]data/ || $dir eq ".rva"))
|
||
{ $var=~s/([_a-z\$\@][_a-z0-9\$\@]*)/$nasm?"$1 wrt ..imagebase":"imagerel $1"/egi; }
|
||
$var;
|
||
};
|
||
|
||
$sz =~ tr/bvlrq/BWDDQ/;
|
||
$self->{value} = "\tD$sz\t";
|
||
for (@arr) { $self->{value} .= &$conv($_).","; }
|
||
$self->{value} .= &$conv($last);
|
||
last;
|
||
};
|
||
/\.byte/ && do { my @str=split(/,\s*/,$line);
|
||
map(s/(0b[0-1]+)/oct($1)/eig,@str);
|
||
map(s/0x([0-9a-f]+)/0$1h/ig,@str) if ($masm);
|
||
while ($#str>15) {
|
||
$self->{value}.="DB\t"
|
||
.join(",",@str[0..15])."\n";
|
||
foreach (0..15) { shift @str; }
|
||
}
|
||
$self->{value}.="DB\t"
|
||
.join(",",@str) if (@str);
|
||
last;
|
||
};
|
||
/\.comm/ && do { my @str=split(/,\s*/,$line);
|
||
my $v=undef;
|
||
if ($nasm) {
|
||
$v.="common $prefix@str[0] @str[1]";
|
||
} else {
|
||
$v="$current_segment\tENDS\n" if ($current_segment);
|
||
$current_segment = "_DATA";
|
||
$v.="$current_segment\tSEGMENT\n";
|
||
$v.="COMM @str[0]:DWORD:".@str[1]/4;
|
||
}
|
||
$self->{value} = $v;
|
||
last;
|
||
};
|
||
}
|
||
$line = "";
|
||
}
|
||
|
||
$ret;
|
||
}
|
||
sub out {
|
||
my $self = shift;
|
||
$self->{value};
|
||
}
|
||
}
|
||
|
||
sub rex {
|
||
local *opcode=shift;
|
||
my ($dst,$src,$rex)=@_;
|
||
|
||
$rex|=0x04 if($dst>=8);
|
||
$rex|=0x01 if($src>=8);
|
||
push @opcode,($rex|0x40) if ($rex);
|
||
}
|
||
|
||
# older gas and ml64 don't handle SSE>2 instructions
|
||
my %regrm = ( "%eax"=>0, "%ecx"=>1, "%edx"=>2, "%ebx"=>3,
|
||
"%esp"=>4, "%ebp"=>5, "%esi"=>6, "%edi"=>7 );
|
||
|
||
my $movq = sub { # elderly gas can't handle inter-register movq
|
||
my $arg = shift;
|
||
my @opcode=(0x66);
|
||
if ($arg =~ /%xmm([0-9]+),\s*%r(\w+)/) {
|
||
my ($src,$dst)=($1,$2);
|
||
if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
|
||
rex(\@opcode,$src,$dst,0x8);
|
||
push @opcode,0x0f,0x7e;
|
||
push @opcode,0xc0|(($src&7)<<3)|($dst&7); # ModR/M
|
||
@opcode;
|
||
} elsif ($arg =~ /%r(\w+),\s*%xmm([0-9]+)/) {
|
||
my ($src,$dst)=($2,$1);
|
||
if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
|
||
rex(\@opcode,$src,$dst,0x8);
|
||
push @opcode,0x0f,0x6e;
|
||
push @opcode,0xc0|(($src&7)<<3)|($dst&7); # ModR/M
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
my $pextrd = sub {
|
||
if (shift =~ /\$([0-9]+),\s*%xmm([0-9]+),\s*(%\w+)/) {
|
||
my @opcode=(0x66);
|
||
$imm=$1;
|
||
$src=$2;
|
||
$dst=$3;
|
||
if ($dst =~ /%r([0-9]+)d/) { $dst = $1; }
|
||
elsif ($dst =~ /%e/) { $dst = $regrm{$dst}; }
|
||
rex(\@opcode,$src,$dst);
|
||
push @opcode,0x0f,0x3a,0x16;
|
||
push @opcode,0xc0|(($src&7)<<3)|($dst&7); # ModR/M
|
||
push @opcode,$imm;
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
my $pinsrd = sub {
|
||
if (shift =~ /\$([0-9]+),\s*(%\w+),\s*%xmm([0-9]+)/) {
|
||
my @opcode=(0x66);
|
||
$imm=$1;
|
||
$src=$2;
|
||
$dst=$3;
|
||
if ($src =~ /%r([0-9]+)/) { $src = $1; }
|
||
elsif ($src =~ /%e/) { $src = $regrm{$src}; }
|
||
rex(\@opcode,$dst,$src);
|
||
push @opcode,0x0f,0x3a,0x22;
|
||
push @opcode,0xc0|(($dst&7)<<3)|($src&7); # ModR/M
|
||
push @opcode,$imm;
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
my $pshufb = sub {
|
||
if (shift =~ /%xmm([0-9]+),\s*%xmm([0-9]+)/) {
|
||
my @opcode=(0x66);
|
||
rex(\@opcode,$2,$1);
|
||
push @opcode,0x0f,0x38,0x00;
|
||
push @opcode,0xc0|($1&7)|(($2&7)<<3); # ModR/M
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
my $palignr = sub {
|
||
if (shift =~ /\$([0-9]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
|
||
my @opcode=(0x66);
|
||
rex(\@opcode,$3,$2);
|
||
push @opcode,0x0f,0x3a,0x0f;
|
||
push @opcode,0xc0|($2&7)|(($3&7)<<3); # ModR/M
|
||
push @opcode,$1;
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
my $pclmulqdq = sub {
|
||
if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
|
||
my @opcode=(0x66);
|
||
rex(\@opcode,$3,$2);
|
||
push @opcode,0x0f,0x3a,0x44;
|
||
push @opcode,0xc0|($2&7)|(($3&7)<<3); # ModR/M
|
||
my $c=$1;
|
||
push @opcode,$c=~/^0/?oct($c):$c;
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
my $rdrand = sub {
|
||
if (shift =~ /%[er](\w+)/) {
|
||
my @opcode=();
|
||
my $dst=$1;
|
||
if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
|
||
rex(\@opcode,0,$1,8);
|
||
push @opcode,0x0f,0xc7,0xf0|($dst&7);
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
my $rdseed = sub {
|
||
if (shift =~ /%[er](\w+)/) {
|
||
my @opcode=();
|
||
my $dst=$1;
|
||
if ($dst !~ /[0-9]+/) { $dst = $regrm{"%e$dst"}; }
|
||
rex(\@opcode,0,$1,8);
|
||
push @opcode,0x0f,0xc7,0xf8|($dst&7);
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
sub rxb {
|
||
local *opcode=shift;
|
||
my ($dst,$src1,$src2,$rxb)=@_;
|
||
|
||
$rxb|=0x7<<5;
|
||
$rxb&=~(0x04<<5) if($dst>=8);
|
||
$rxb&=~(0x01<<5) if($src1>=8);
|
||
$rxb&=~(0x02<<5) if($src2>=8);
|
||
push @opcode,$rxb;
|
||
}
|
||
|
||
my $vprotd = sub {
|
||
if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
|
||
my @opcode=(0x8f);
|
||
rxb(\@opcode,$3,$2,-1,0x08);
|
||
push @opcode,0x78,0xc2;
|
||
push @opcode,0xc0|($2&7)|(($3&7)<<3); # ModR/M
|
||
my $c=$1;
|
||
push @opcode,$c=~/^0/?oct($c):$c;
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
my $vprotq = sub {
|
||
if (shift =~ /\$([x0-9a-f]+),\s*%xmm([0-9]+),\s*%xmm([0-9]+)/) {
|
||
my @opcode=(0x8f);
|
||
rxb(\@opcode,$3,$2,-1,0x08);
|
||
push @opcode,0x78,0xc3;
|
||
push @opcode,0xc0|($2&7)|(($3&7)<<3); # ModR/M
|
||
my $c=$1;
|
||
push @opcode,$c=~/^0/?oct($c):$c;
|
||
@opcode;
|
||
} else {
|
||
();
|
||
}
|
||
};
|
||
|
||
if ($nasm) {
|
||
print <<___;
|
||
default rel
|
||
%define XMMWORD
|
||
%define YMMWORD
|
||
%define ZMMWORD
|
||
___
|
||
} elsif ($masm) {
|
||
print <<___;
|
||
OPTION DOTNAME
|
||
___
|
||
}
|
||
while($line=<>) {
|
||
|
||
chomp($line);
|
||
|
||
$line =~ s|[#!].*$||; # get rid of asm-style comments...
|
||
$line =~ s|/\*.*\*/||; # ... and C-style comments...
|
||
$line =~ s|^\s+||; # ... and skip white spaces in beginning
|
||
$line =~ s|\s+$||; # ... and at the end
|
||
|
||
undef $label;
|
||
undef $opcode;
|
||
undef @args;
|
||
|
||
if ($label=label->re(\$line)) { print $label->out(); }
|
||
|
||
if (directive->re(\$line)) {
|
||
printf "%s",directive->out();
|
||
} elsif ($opcode=opcode->re(\$line)) {
|
||
my $asm = eval("\$".$opcode->mnemonic());
|
||
undef @bytes;
|
||
|
||
if ((ref($asm) eq 'CODE') && scalar(@bytes=&$asm($line))) {
|
||
print $gas?".byte\t":"DB\t",join(',',@bytes),"\n";
|
||
next;
|
||
}
|
||
|
||
ARGUMENT: while (1) {
|
||
my $arg;
|
||
|
||
if ($arg=register->re(\$line)) { opcode->size($arg->size()); }
|
||
elsif ($arg=const->re(\$line)) { }
|
||
elsif ($arg=ea->re(\$line)) { }
|
||
elsif ($arg=expr->re(\$line)) { }
|
||
else { last ARGUMENT; }
|
||
|
||
push @args,$arg;
|
||
|
||
last ARGUMENT if ($line !~ /^,/);
|
||
|
||
$line =~ s/^,\s*//;
|
||
} # ARGUMENT:
|
||
|
||
if ($#args>=0) {
|
||
my $insn;
|
||
my $sz=opcode->size();
|
||
|
||
if ($gas) {
|
||
$insn = $opcode->out($#args>=1?$args[$#args]->size():$sz);
|
||
@args = map($_->out($sz),@args);
|
||
printf "\t%s\t%s",$insn,join(",",@args);
|
||
} else {
|
||
$insn = $opcode->out();
|
||
foreach (@args) {
|
||
my $arg = $_->out();
|
||
# $insn.=$sz compensates for movq, pinsrw, ...
|
||
if ($arg =~ /^xmm[0-9]+$/) { $insn.=$sz; $sz="x" if(!$sz); last; }
|
||
if ($arg =~ /^ymm[0-9]+$/) { $insn.=$sz; $sz="y" if(!$sz); last; }
|
||
if ($arg =~ /^zmm[0-9]+$/) { $insn.=$sz; $sz="z" if(!$sz); last; }
|
||
if ($arg =~ /^mm[0-9]+$/) { $insn.=$sz; $sz="q" if(!$sz); last; }
|
||
}
|
||
@args = reverse(@args);
|
||
undef $sz if ($nasm && $opcode->mnemonic() eq "lea");
|
||
printf "\t%s\t%s",$insn,join(",",map($_->out($sz),@args));
|
||
}
|
||
} else {
|
||
printf "\t%s",$opcode->out();
|
||
}
|
||
}
|
||
|
||
print $line,"\n";
|
||
}
|
||
|
||
print "\n$current_segment\tENDS\n" if ($current_segment && $masm);
|
||
print "END\n" if ($masm);
|
||
|
||
close STDOUT;
|
||
|
||
#################################################
|
||
# Cross-reference x86_64 ABI "card"
|
||
#
|
||
# Unix Win64
|
||
# %rax * *
|
||
# %rbx - -
|
||
# %rcx #4 #1
|
||
# %rdx #3 #2
|
||
# %rsi #2 -
|
||
# %rdi #1 -
|
||
# %rbp - -
|
||
# %rsp - -
|
||
# %r8 #5 #3
|
||
# %r9 #6 #4
|
||
# %r10 * *
|
||
# %r11 * *
|
||
# %r12 - -
|
||
# %r13 - -
|
||
# %r14 - -
|
||
# %r15 - -
|
||
#
|
||
# (*) volatile register
|
||
# (-) preserved by callee
|
||
# (#) Nth argument, volatile
|
||
#
|
||
# In Unix terms top of stack is argument transfer area for arguments
|
||
# which could not be accomodated in registers. Or in other words 7th
|
||
# [integer] argument resides at 8(%rsp) upon function entry point.
|
||
# 128 bytes above %rsp constitute a "red zone" which is not touched
|
||
# by signal handlers and can be used as temporal storage without
|
||
# allocating a frame.
|
||
#
|
||
# In Win64 terms N*8 bytes on top of stack is argument transfer area,
|
||
# which belongs to/can be overwritten by callee. N is the number of
|
||
# arguments passed to callee, *but* not less than 4! This means that
|
||
# upon function entry point 5th argument resides at 40(%rsp), as well
|
||
# as that 32 bytes from 8(%rsp) can always be used as temporal
|
||
# storage [without allocating a frame]. One can actually argue that
|
||
# one can assume a "red zone" above stack pointer under Win64 as well.
|
||
# Point is that at apparently no occasion Windows kernel would alter
|
||
# the area above user stack pointer in true asynchronous manner...
|
||
#
|
||
# All the above means that if assembler programmer adheres to Unix
|
||
# register and stack layout, but disregards the "red zone" existense,
|
||
# it's possible to use following prologue and epilogue to "gear" from
|
||
# Unix to Win64 ABI in leaf functions with not more than 6 arguments.
|
||
#
|
||
# omnipotent_function:
|
||
# ifdef WIN64
|
||
# movq %rdi,8(%rsp)
|
||
# movq %rsi,16(%rsp)
|
||
# movq %rcx,%rdi ; if 1st argument is actually present
|
||
# movq %rdx,%rsi ; if 2nd argument is actually ...
|
||
# movq %r8,%rdx ; if 3rd argument is ...
|
||
# movq %r9,%rcx ; if 4th argument ...
|
||
# movq 40(%rsp),%r8 ; if 5th ...
|
||
# movq 48(%rsp),%r9 ; if 6th ...
|
||
# endif
|
||
# ...
|
||
# ifdef WIN64
|
||
# movq 8(%rsp),%rdi
|
||
# movq 16(%rsp),%rsi
|
||
# endif
|
||
# ret
|
||
#
|
||
#################################################
|
||
# Win64 SEH, Structured Exception Handling.
|
||
#
|
||
# Unlike on Unix systems(*) lack of Win64 stack unwinding information
|
||
# has undesired side-effect at run-time: if an exception is raised in
|
||
# assembler subroutine such as those in question (basically we're
|
||
# referring to segmentation violations caused by malformed input
|
||
# parameters), the application is briskly terminated without invoking
|
||
# any exception handlers, most notably without generating memory dump
|
||
# or any user notification whatsoever. This poses a problem. It's
|
||
# possible to address it by registering custom language-specific
|
||
# handler that would restore processor context to the state at
|
||
# subroutine entry point and return "exception is not handled, keep
|
||
# unwinding" code. Writing such handler can be a challenge... But it's
|
||
# doable, though requires certain coding convention. Consider following
|
||
# snippet:
|
||
#
|
||
# .type function,@function
|
||
# function:
|
||
# movq %rsp,%rax # copy rsp to volatile register
|
||
# pushq %r15 # save non-volatile registers
|
||
# pushq %rbx
|
||
# pushq %rbp
|
||
# movq %rsp,%r11
|
||
# subq %rdi,%r11 # prepare [variable] stack frame
|
||
# andq $-64,%r11
|
||
# movq %rax,0(%r11) # check for exceptions
|
||
# movq %r11,%rsp # allocate [variable] stack frame
|
||
# movq %rax,0(%rsp) # save original rsp value
|
||
# magic_point:
|
||
# ...
|
||
# movq 0(%rsp),%rcx # pull original rsp value
|
||
# movq -24(%rcx),%rbp # restore non-volatile registers
|
||
# movq -16(%rcx),%rbx
|
||
# movq -8(%rcx),%r15
|
||
# movq %rcx,%rsp # restore original rsp
|
||
# ret
|
||
# .size function,.-function
|
||
#
|
||
# The key is that up to magic_point copy of original rsp value remains
|
||
# in chosen volatile register and no non-volatile register, except for
|
||
# rsp, is modified. While past magic_point rsp remains constant till
|
||
# the very end of the function. In this case custom language-specific
|
||
# exception handler would look like this:
|
||
#
|
||
# EXCEPTION_DISPOSITION handler (EXCEPTION_RECORD *rec,ULONG64 frame,
|
||
# CONTEXT *context,DISPATCHER_CONTEXT *disp)
|
||
# { ULONG64 *rsp = (ULONG64 *)context->Rax;
|
||
# if (context->Rip >= magic_point)
|
||
# { rsp = ((ULONG64 **)context->Rsp)[0];
|
||
# context->Rbp = rsp[-3];
|
||
# context->Rbx = rsp[-2];
|
||
# context->R15 = rsp[-1];
|
||
# }
|
||
# context->Rsp = (ULONG64)rsp;
|
||
# context->Rdi = rsp[1];
|
||
# context->Rsi = rsp[2];
|
||
#
|
||
# memcpy (disp->ContextRecord,context,sizeof(CONTEXT));
|
||
# RtlVirtualUnwind(UNW_FLAG_NHANDLER,disp->ImageBase,
|
||
# dips->ControlPc,disp->FunctionEntry,disp->ContextRecord,
|
||
# &disp->HandlerData,&disp->EstablisherFrame,NULL);
|
||
# return ExceptionContinueSearch;
|
||
# }
|
||
#
|
||
# It's appropriate to implement this handler in assembler, directly in
|
||
# function's module. In order to do that one has to know members'
|
||
# offsets in CONTEXT and DISPATCHER_CONTEXT structures and some constant
|
||
# values. Here they are:
|
||
#
|
||
# CONTEXT.Rax 120
|
||
# CONTEXT.Rcx 128
|
||
# CONTEXT.Rdx 136
|
||
# CONTEXT.Rbx 144
|
||
# CONTEXT.Rsp 152
|
||
# CONTEXT.Rbp 160
|
||
# CONTEXT.Rsi 168
|
||
# CONTEXT.Rdi 176
|
||
# CONTEXT.R8 184
|
||
# CONTEXT.R9 192
|
||
# CONTEXT.R10 200
|
||
# CONTEXT.R11 208
|
||
# CONTEXT.R12 216
|
||
# CONTEXT.R13 224
|
||
# CONTEXT.R14 232
|
||
# CONTEXT.R15 240
|
||
# CONTEXT.Rip 248
|
||
# CONTEXT.Xmm6 512
|
||
# sizeof(CONTEXT) 1232
|
||
# DISPATCHER_CONTEXT.ControlPc 0
|
||
# DISPATCHER_CONTEXT.ImageBase 8
|
||
# DISPATCHER_CONTEXT.FunctionEntry 16
|
||
# DISPATCHER_CONTEXT.EstablisherFrame 24
|
||
# DISPATCHER_CONTEXT.TargetIp 32
|
||
# DISPATCHER_CONTEXT.ContextRecord 40
|
||
# DISPATCHER_CONTEXT.LanguageHandler 48
|
||
# DISPATCHER_CONTEXT.HandlerData 56
|
||
# UNW_FLAG_NHANDLER 0
|
||
# ExceptionContinueSearch 1
|
||
#
|
||
# In order to tie the handler to the function one has to compose
|
||
# couple of structures: one for .xdata segment and one for .pdata.
|
||
#
|
||
# UNWIND_INFO structure for .xdata segment would be
|
||
#
|
||
# function_unwind_info:
|
||
# .byte 9,0,0,0
|
||
# .rva handler
|
||
#
|
||
# This structure designates exception handler for a function with
|
||
# zero-length prologue, no stack frame or frame register.
|
||
#
|
||
# To facilitate composing of .pdata structures, auto-generated "gear"
|
||
# prologue copies rsp value to rax and denotes next instruction with
|
||
# .LSEH_begin_{function_name} label. This essentially defines the SEH
|
||
# styling rule mentioned in the beginning. Position of this label is
|
||
# chosen in such manner that possible exceptions raised in the "gear"
|
||
# prologue would be accounted to caller and unwound from latter's frame.
|
||
# End of function is marked with respective .LSEH_end_{function_name}
|
||
# label. To summarize, .pdata segment would contain
|
||
#
|
||
# .rva .LSEH_begin_function
|
||
# .rva .LSEH_end_function
|
||
# .rva function_unwind_info
|
||
#
|
||
# Reference to functon_unwind_info from .xdata segment is the anchor.
|
||
# In case you wonder why references are 32-bit .rvas and not 64-bit
|
||
# .quads. References put into these two segments are required to be
|
||
# *relative* to the base address of the current binary module, a.k.a.
|
||
# image base. No Win64 module, be it .exe or .dll, can be larger than
|
||
# 2GB and thus such relative references can be and are accommodated in
|
||
# 32 bits.
|
||
#
|
||
# Having reviewed the example function code, one can argue that "movq
|
||
# %rsp,%rax" above is redundant. It is not! Keep in mind that on Unix
|
||
# rax would contain an undefined value. If this "offends" you, use
|
||
# another register and refrain from modifying rax till magic_point is
|
||
# reached, i.e. as if it was a non-volatile register. If more registers
|
||
# are required prior [variable] frame setup is completed, note that
|
||
# nobody says that you can have only one "magic point." You can
|
||
# "liberate" non-volatile registers by denoting last stack off-load
|
||
# instruction and reflecting it in finer grade unwind logic in handler.
|
||
# After all, isn't it why it's called *language-specific* handler...
|
||
#
|
||
# Attentive reader can notice that exceptions would be mishandled in
|
||
# auto-generated "gear" epilogue. Well, exception effectively can't
|
||
# occur there, because if memory area used by it was subject to
|
||
# segmentation violation, then it would be raised upon call to the
|
||
# function (and as already mentioned be accounted to caller, which is
|
||
# not a problem). If you're still not comfortable, then define tail
|
||
# "magic point" just prior ret instruction and have handler treat it...
|
||
#
|
||
# (*) Note that we're talking about run-time, not debug-time. Lack of
|
||
# unwind information makes debugging hard on both Windows and
|
||
# Unix. "Unlike" referes to the fact that on Unix signal handler
|
||
# will always be invoked, core dumped and appropriate exit code
|
||
# returned to parent (for user notification).
|