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x86_64-xlate.pl update: refine SEH support.
This commit is contained in:
Andy Polyakov
parent
ab7e09f59b
commit
80aa9cc985
@ -1,6 +1,6 @@
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#!/usr/bin/env perl
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# Ascetic x86_64 AT&T to MASM assembler translator by <appro>.
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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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@ -23,8 +23,8 @@
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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 the end for
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# explanation].
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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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@ -54,7 +54,11 @@
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# .Lpic_point:
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# ...
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# lea .Label-.Lpic_point(%rcx),%rbp
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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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my $output = shift;
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{ my ($stddev,$stdino,@junk)=stat(STDOUT);
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@ -137,6 +141,9 @@ my %globals;
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}
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$self->{op} .= "DB\t0F3h,0C3h\t\t;repret";
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}
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elsif ($self->{op} =~ /^(pop|push)f/) {
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$self->{op} .= $self->{sz};
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}
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$self->{op};
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}
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}
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@ -217,6 +224,7 @@ my %globals;
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} else {
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%szmap = ( b=>"BYTE$PTR", w=>"WORD$PTR", l=>"DWORD$PTR", q=>"QWORD$PTR" );
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$self->{label} =~ s/\.L/\$L\$/g;
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$self->{label} =~ s/\./\$/g;
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$self->{label} =~ s/0x([0-9a-f]+)/0$1h/ig;
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$self->{label} = "($self->{label})" if ($self->{label} =~ /[\*\+\-\/]/);
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@ -286,7 +294,7 @@ my %globals;
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$ret = $self;
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$line = substr($line,@+[0]); $line =~ s/^\s+//;
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$self->{value} =~ s/\.L/\$L/ if ($win64);
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$self->{value} =~ s/\.L/\$L\$/ if ($win64);
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}
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$ret;
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}
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@ -304,6 +312,10 @@ my %globals;
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"\n";
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$func .= " mov QWORD${PTR}[8+rsp],rdi\t;WIN64 prologue\n";
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$func .= " mov QWORD${PTR}[16+rsp],rsi\n";
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$func .= " mov rax,rsp\n";
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$func .= "\$L\$SEH_begin_$current_function->{name}:";
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$func .= ":" if ($masm);
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$func .= "\n";
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my $narg = $current_function->{narg};
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$narg=6 if (!defined($narg));
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$func .= " mov rdi,rcx\n" if ($narg>0);
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@ -330,7 +342,7 @@ my %globals;
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$ret = $self;
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$line = substr($line,@+[0]); $line =~ s/^\s+//;
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$self->{value} =~ s/\.L/\$L/g if ($win64);
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$self->{value} =~ s/\.L/\$L\$/g if ($win64);
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}
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$ret;
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}
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@ -429,7 +441,9 @@ my %globals;
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$self->{value} .= ":NEAR" if ($masm);
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last;
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};
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/\.globl/ && do { $self->{value} = "PUBLIC\t".$line;
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/\.globl|.global/
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&& do { $self->{value} = $masm?"PUBLIC":"global";
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$self->{value} .= "\t".$line;
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$globals{$line} = $line;
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last;
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};
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@ -448,20 +462,22 @@ my %globals;
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last;
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};
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/\.size/ && do { if (defined($current_function)) {
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$self->{value}="$current_function->{name}\tENDP" if(!$nasm);
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$self->{value}="\$L\$SEH_end_$current_function->{name}:";
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$self->{value}.=":\n$current_function->{name}\tENDP" if($masm);
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undef $current_function;
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}
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last;
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};
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/\.align/ && do { $self->{value} = "ALIGN\t".$line; last; };
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/\.(byte|value|long|quad)/
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&& do { my @arr = split(',',$line);
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my $sz = substr($1,0,1);
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&& do { my $sz = substr($1,0,1);
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my @arr = split(',',$line);
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my $last = pop(@arr);
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my $conv = sub { my $var=shift;
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$var=~s/0x([0-9a-f]+)/0$1h/ig;
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$var=~s/\.L/\$L\$/g;
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if ($current_segment=~/.[px]data/)
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{ $var=~s/\b([_a-z\$\@][_a-z0-9\$\@]*)/$nasm?"$1 wrt ..imagebase":"imagerel $1"/egi; }
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{ $var=~s/([_a-z\$\@][_a-z0-9\$\@]*)/$nasm?"$1 wrt ..imagebase":"imagerel $1"/egi; }
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$var;
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};
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@ -502,7 +518,6 @@ my %globals;
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if ($nasm) {
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print <<___;
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default rel
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%define PUBLIC global
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___
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} elsif ($masm) {
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print <<___;
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@ -569,7 +584,7 @@ print "\n$current_segment\tENDS\nEND\n" if ($current_segment && $masm);
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close STDOUT;
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#################################################
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#################################################
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# Cross-reference x86_64 ABI "card"
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#
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# Unix Win64
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@ -634,7 +649,9 @@ close STDOUT;
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# endif
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# ret
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#
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#################################################
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#################################################
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# Win64 SEH, Structured Exception Handling.
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#
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# Unlike on Unix systems(*) lack of Win64 stack unwinding information
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# has undesired side-effect at run-time: if an exception is raised in
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# assembler subroutine such as those in question (basically we're
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@ -649,6 +666,7 @@ close STDOUT;
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# doable, though requires certain coding convention. Consider following
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# snippet:
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#
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# .type function,@function
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# function:
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# movq %rsp,%rax # copy rsp to volatile register
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# pushq %r15 # save non-volatile registers
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@ -668,6 +686,7 @@ close STDOUT;
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# movq -8(%rcx),%r15
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# movq %rcx,%rsp # restore original rsp
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# ret
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# .size function,.-function
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#
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# The key is that up to magic_point copy of original rsp value remains
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# in chosen volatile register and no non-volatile register, except for
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@ -677,10 +696,8 @@ close STDOUT;
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#
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# EXCEPTION_DISPOSITION handler (EXCEPTION_RECORD *rec,ULONG64 frame,
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# CONTEXT *context,DISPATCHER_CONTEXT *disp)
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# { ULONG64 *rsp;
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# if (context->Rip<magic_point)
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# rsp = (ULONG64 *)context->Rax;
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# else
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# { ULONG64 *rsp = (ULONG64 *)context->Rax;
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# if (context->Rip >= magic_point)
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# { rsp = ((ULONG64 **)context->Rsp)[0];
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# context->Rbp = rsp[-3];
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# context->Rbx = rsp[-2];
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@ -731,19 +748,57 @@ close STDOUT;
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# UNW_FLAG_NHANDLER 0
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# ExceptionContinueSearch 1
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#
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# UNWIND_INFO structure for .xdata segment would be
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# DB 9,0,0,0
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# DD imagerel handler
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# denoting exception handler for a function with zero-length prologue,
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# no stack frame or frame register.
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# In order to tie the handler to the function one has to compose
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# couple of structures: one for .xdata segment and one for .pdata.
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#
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# P.S. Attentive reader can notice that effectively no exceptions are
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# expected in "gear" prologue and epilogue [discussed in "ABI
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# cross-reference" above]. No, there are not. This is because if
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# memory area used by them was subject to segmentation violation,
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# then exception would be raised upon call to our function and be
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# accounted to caller and unwound from its frame, which is not a
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# problem.
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# UNWIND_INFO structure for .xdata segment would be
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#
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# function_unwind_info:
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# .byte 9,0,0,0
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# .long handler
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#
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# This structure designates exception handler for a function with
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# zero-length prologue, no stack frame or frame register.
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#
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# To facilitate composing of .pdata structures, auto-generated "gear"
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# prologue copies rsp value to rax and denotes next instruction with
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# $L$SEH_begin_{function_name} label. This essentially defines the SEH
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# styling rule mentioned in the beginning. Position of this label is
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# chosen in such manner that possible exceptions raised in the "gear"
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# prologue would be accounted to caller and unwound from latter's frame.
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# End of function is marked with respective $L$SEH_end_{function_name}
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# label. To summarize, .pdata segment would contain
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#
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# .long $L$SEH_begin_function
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# .long $L$SEH_end_function
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# .long function_unwind_info
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#
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# Reference to functon_unwind_info from .xdata segment is the anchor.
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# In case you wonder why references are 32-bit .longs and not 64-bit
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# .quads. References put into these two segments are required to be
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# *relative* to the base address of the current binary module, a.k.a.
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# image base. No Win64 module, be it .exe or .dll, can be larger than
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# 2GB and thus such relative references can be and are accommodated in
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# 32 bits.
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#
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# Having reviewed the example function code, one can argue that "movq
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# %rsp,%rax" above is redundant. It is not! Keep in mind that on Unix
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# rax would contain an undefined value. If this "offends" you, use
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# another register and refrain from modifying rax till magic_point is
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# reached, i.e. as if it was a non-volatile register. If more registers
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# are required prior [variable] frame setup is completed, note that
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# nobody says that you can have only one "magic point." You can
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# "liberate" non-volatile registers by denoting last stack off-load
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# instruction and reflecting it in finer grade unwind logic in handler.
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# After all, isn't it why it's called *language-specific* handler...
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#
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# Attentive reader can notice that exceptions would be mishandled in
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# auto-generated "gear" epilogue. Well, exception effectively can't
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# occur there, because if memory area used by it was subject to
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# segmentation violation, then it would be raised upon call to the
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# function (and as already mentioned be accounted to caller, which is
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# not a problem). If you're still not comfortable, then define tail
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# "magic point" just prior ret instruction and have handler treat it...
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#
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# (*) Note that we're talking about run-time, not debug-time. Lack of
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# unwind information makes debugging hard on both Windows and
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