Fix wrong decompilation on same jump target optmization (#248)

david942j · Dec 25, 2023 · 4f35cf8 · 4f35cf8
1 parent afed5cf
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diff --git a/lib/seccomp-tools/asm/compiler.rb b/lib/seccomp-tools/asm/compiler.rb
@@ -178,7 +178,7 @@ def emit_ret(val)
 
       def emit_cmp(cmp, jt, jf)
         jop, jt, jf = convert_jmp_op(cmp, jt, jf)
-        return emit(:jmp, jop, 0, jt: 0, jf: 0, k: jt) if jop == :ja || jt == jf
+        return emit(:jmp, :none, 0, jt: 0, jf: 0, k: jt) if jop == :ja || jt == jf
 
         val = cmp[1]
         src = val.x? ? :x : :k

diff --git a/spec/asm/compiler_spec.rb b/spec/asm/compiler_spec.rb
@@ -186,6 +186,25 @@
 A = arch
       EOS
     end
+
+    it 'optimizes jump targets' do
+      compiler = described_class.new(<<-EOS, nil, :amd64)
+A = args[0]
+X = A
+if (A == X) goto out
+else goto out
+A = X
+out: return ALLOW
+      EOS
+
+      expect(compiler.compile!.map(&:decompile).join("\n")).to eq <<-EOS.strip
+A = args[0]
+X = A
+goto 0004
+A = X
+return ALLOW
+      EOS
+    end
   end
 
   describe 'label' do