[Qemu-devel] [RISU PATCH v3 04/18] risugen_x86_constraints: add module

[Jan Bobek <jan.bobek@gmail.com>]

The module risugen_x86_constraints.pm provides environment for
evaluating x86 "!constraints" blocks. This is facilitated by the
single exported function eval_constraints_block.

Signed-off-by: Jan Bobek <jan.bobek@gmail.com>
---
 risugen_x86_constraints.pm | 154 +++++++++++++++++++++++++++++++++++++
 1 file changed, 154 insertions(+)
 create mode 100644 risugen_x86_constraints.pm

diff --git a/risugen_x86_constraints.pm b/risugen_x86_constraints.pm
new file mode 100644
index 0000000..a4ee687
--- /dev/null
+++ b/risugen_x86_constraints.pm
@@ -0,0 +1,154 @@
+#!/usr/bin/perl -w
+###############################################################################
+# Copyright (c) 2019 Jan Bobek
+# All rights reserved. This program and the accompanying materials
+# are made available under the terms of the Eclipse Public License v1.0
+# which accompanies this distribution, and is available at
+# http://www.eclipse.org/legal/epl-v10.html
+#
+# Contributors:
+#     Jan Bobek - initial implementation
+###############################################################################
+
+# risugen_x86_constraints -- risugen_x86's helper module for "!constraints" blocks
+package risugen_x86_constraints;
+
+use strict;
+use warnings;
+
+use risugen_common;
+use risugen_x86_asm;
+
+our @ISA    = qw(Exporter);
+our @EXPORT = qw(eval_constraints_block);
+
+my $is_x86_64;
+
+sub data16($%)
+{
+    my ($insn, %data16) = @_;
+    $insn->{data16} = \%data16;
+}
+
+sub rep($%)
+{
+    my ($insn, %rep) = @_;
+    $insn->{rep} = \%rep;
+}
+
+sub repne($%)
+{
+    my ($insn, %repne) = @_;
+    $insn->{repne} = \%repne;
+}
+
+sub rex($%)
+{
+    my ($insn, %rex) = @_;
+    # It doesn't make sense to randomize any REX fields, since REX.W
+    # is opcode-like and REX.R/.X/.B are encoded automatically by
+    # risugen_x86_asm.
+    $insn->{rex} = \%rex;
+}
+
+sub vex($%)
+{
+    my ($insn, %vex) = @_;
+    my $regidw = $is_x86_64 ? 4 : 3;
+
+    # There is no point in randomizing other VEX fields, since
+    # VEX.R/.X/.B are encoded automatically by risugen_x86_asm, and
+    # VEX.M/.P are opcodes.
+    $vex{l} = randint(width => 1) ? 256 : 128 unless defined $vex{l};
+    $vex{v} = randint(width => $regidw)       unless defined $vex{v};
+    $vex{w} = randint(width => 1)             unless defined $vex{w};
+    $insn->{vex} = \%vex;
+}
+
+sub modrm_($%)
+{
+    my ($insn, %args) = @_;
+    my $regidw = $is_x86_64 ? 4 : 3;
+
+    my %modrm = ();
+    if (defined $args{reg}) {
+        # This makes the config file syntax a bit more accommodating
+        # in cases where MODRM.REG is an opcode extension field.
+        $modrm{reg} = $args{reg};
+    } else {
+        $modrm{reg} = randint(width => $regidw);
+    }
+
+    # There is also a displacement-only form, but we don't know
+    # absolute address of the memblock, so we cannot test it.
+    my $form = int(rand(4));
+    if ($form == 0) {
+        $modrm{reg2} = randint(width => $regidw);
+    } else {
+        $modrm{base} = randint(width => $regidw);
+
+        if ($form == 2) {
+            $modrm{base}        = randint(width => $regidw);
+            $modrm{disp}{value} = randint(width => 8, signed => 1);
+            $modrm{disp}{width} = 8;
+        } elsif ($form == 3) {
+            $modrm{base}        = randint(width => $regidw);
+            $modrm{disp}{value} = randint(width => 32, signed => 1);
+            $modrm{disp}{width} = 32;
+        }
+
+        my $have_index = int(rand(2));
+        if ($have_index) {
+            my $indexk      = $args{indexk};
+            $modrm{ss}      = randint(width => 2);
+            $modrm{$indexk} = randint(width => $regidw);
+        }
+    }
+
+    $insn->{modrm} = \%modrm;
+}
+
+sub modrm($%)
+{
+    my ($insn, %args) = @_;
+    modrm_($insn, indexk => 'index', %args);
+}
+
+sub modrm_vsib($%)
+{
+    my ($insn, %args) = @_;
+    modrm_($insn, indexk => 'vindex', %args);
+}
+
+sub imm($%)
+{
+    my ($insn, %args) = @_;
+    $insn->{imm}{value} = randint(%args);
+    $insn->{imm}{width} = $args{width};
+}
+
+sub eval_constraints_block(%)
+{
+    my (%args) = @_;
+    my $rec = $args{rec};
+    my $insn = $args{insn};
+    my $insnname = $rec->{name};
+    my $opcode = $insn->{opcode}{value};
+
+    $is_x86_64 = $args{is_x86_64};
+
+    my $constraint = $rec->{blocks}{"constraints"};
+    if (defined $constraint) {
+        # user-specified constraint: evaluate in an environment
+        # with variables set corresponding to the variable fields.
+        my %env = extract_fields($opcode, $rec);
+        # set the variable $_ to the instruction in question
+        $env{_} = $insn;
+
+        return eval_block($insnname, "constraints", $constraint, \%env);
+    } else {
+        return 1;
+    }
+}
+
+1;
-- 
2.20.1