Add RedundantGotoTransformer

Removes GOTO instructions that point to the next instruction, typically
left over from stripping exceptions inserted by the obfuscator.

Although modern decompilers can handle such GOTOs fine, removing them
makes for a nicer IR representation.

Signed-off-by: Major <major@emulate.rs>
bzip2
Major 5 years ago
parent dc36c7835c
commit 7b92ccb244
  1. 2
      deob/src/main/java/dev/openrs2/deob/Deobfuscator.kt
  2. 53
      deob/src/main/java/dev/openrs2/deob/transform/RedundantGotoTransformer.kt

@ -28,6 +28,7 @@ import dev.openrs2.deob.transform.OriginalNameTransformer
import dev.openrs2.deob.transform.OriginalPcRestoreTransformer import dev.openrs2.deob.transform.OriginalPcRestoreTransformer
import dev.openrs2.deob.transform.OriginalPcSaveTransformer import dev.openrs2.deob.transform.OriginalPcSaveTransformer
import dev.openrs2.deob.transform.OverrideTransformer import dev.openrs2.deob.transform.OverrideTransformer
import dev.openrs2.deob.transform.RedundantGotoTransformer
import dev.openrs2.deob.transform.RemapTransformer import dev.openrs2.deob.transform.RemapTransformer
import dev.openrs2.deob.transform.ResetTransformer import dev.openrs2.deob.transform.ResetTransformer
import dev.openrs2.deob.transform.StaticScramblingTransformer import dev.openrs2.deob.transform.StaticScramblingTransformer
@ -180,6 +181,7 @@ class Deobfuscator(private val input: Path, private val output: Path) {
VisibilityTransformer(), VisibilityTransformer(),
FinalTransformer(), FinalTransformer(),
OverrideTransformer(), OverrideTransformer(),
RedundantGotoTransformer(),
OriginalPcRestoreTransformer(), OriginalPcRestoreTransformer(),
FernflowerExceptionTransformer() FernflowerExceptionTransformer()
) )

@ -0,0 +1,53 @@
package dev.openrs2.deob.transform
import com.github.michaelbull.logging.InlineLogger
import dev.openrs2.asm.classpath.ClassPath
import dev.openrs2.asm.classpath.Library
import dev.openrs2.asm.nextReal
import dev.openrs2.asm.removeDeadCode
import dev.openrs2.asm.transform.Transformer
import org.objectweb.asm.Opcodes
import org.objectweb.asm.tree.ClassNode
import org.objectweb.asm.tree.JumpInsnNode
import org.objectweb.asm.tree.MethodNode
class RedundantGotoTransformer : Transformer() {
private var removed = 0
override fun preTransform(classPath: ClassPath) {
removed = 0
}
override fun preTransformMethod(
classPath: ClassPath,
library: Library,
clazz: ClassNode,
method: MethodNode
): Boolean {
method.removeDeadCode(clazz.name)
return false
}
override fun transformCode(classPath: ClassPath, library: Library, clazz: ClassNode, method: MethodNode): Boolean {
for (instruction in method.instructions) {
if (instruction.opcode == Opcodes.GOTO) {
instruction as JumpInsnNode
if (instruction.nextReal === instruction.label.nextReal) {
method.instructions.remove(instruction)
removed++
}
}
}
return false
}
override fun postTransform(classPath: ClassPath) {
logger.info { "Removed $removed redundant GOTO instructions" }
}
private companion object {
private val logger = InlineLogger()
}
}
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