From 2862b305c50061d3d98a63b2caca05d6e36d262a Mon Sep 17 00:00:00 2001 From: Graham Date: Sun, 29 Mar 2020 22:10:19 +0100 Subject: [PATCH] Convert Java 1.1-style synchronized blocks to a more modern style The non-HD client appears to have been compiled with javac 1.1 or 1.2, which compiles synchronized blocks differently to modern versions of Java. For example, it uses a single try/catch block (modern versions use two, the latter of which is recursive), subroutines (modern versions do not) and the range of the try block is narrower. Fernflower doesn't understand this old style of bytecode, and produces empty synchronized blocks that do not cover the correct range. The MONITORENTER sequence is also slightly different: it uses ASTORE ALOAD MONITORENTER after pushing the monitor variable, rather than DUP ASTORE MONITORENTER. This doesn't break Fernflower, but does make it introduce a pointless assignment to a variable only used in the synchronized() statement, rather than inlining the expression. This commit introduces a transformer which fixes up Java 1.1-style synchronized blocks just enough for Fernflower to be able to decompile them cleanly. (It doesn't add a recursive try/catch, as Fernflower ignores them.) Signed-off-by: Graham --- .../java/dev/openrs2/deob/Deobfuscator.kt | 2 + .../deob/transform/MonitorTransformer.kt | 115 ++++++++++++++++++ 2 files changed, 117 insertions(+) create mode 100644 deob/src/main/java/dev/openrs2/deob/transform/MonitorTransformer.kt diff --git a/deob/src/main/java/dev/openrs2/deob/Deobfuscator.kt b/deob/src/main/java/dev/openrs2/deob/Deobfuscator.kt index 88392415..6c4a2e6c 100644 --- a/deob/src/main/java/dev/openrs2/deob/Deobfuscator.kt +++ b/deob/src/main/java/dev/openrs2/deob/Deobfuscator.kt @@ -23,6 +23,7 @@ import dev.openrs2.deob.transform.FieldOrderTransformer import dev.openrs2.deob.transform.FinalTransformer import dev.openrs2.deob.transform.InvokeSpecialTransformer import dev.openrs2.deob.transform.MethodOrderTransformer +import dev.openrs2.deob.transform.MonitorTransformer import dev.openrs2.deob.transform.OpaquePredicateTransformer import dev.openrs2.deob.transform.OriginalNameTransformer import dev.openrs2.deob.transform.OriginalPcRestoreTransformer @@ -154,6 +155,7 @@ class Deobfuscator(private val input: Path, private val output: Path) { ResourceTransformer(), OpaquePredicateTransformer(), ExceptionTracingTransformer(), + MonitorTransformer(), BitShiftTransformer(), CanvasTransformer(), FieldOrderTransformer(), diff --git a/deob/src/main/java/dev/openrs2/deob/transform/MonitorTransformer.kt b/deob/src/main/java/dev/openrs2/deob/transform/MonitorTransformer.kt new file mode 100644 index 00000000..f137c845 --- /dev/null +++ b/deob/src/main/java/dev/openrs2/deob/transform/MonitorTransformer.kt @@ -0,0 +1,115 @@ +package dev.openrs2.deob.transform + +import com.github.michaelbull.logging.InlineLogger +import dev.openrs2.asm.InsnMatcher +import dev.openrs2.asm.classpath.ClassPath +import dev.openrs2.asm.classpath.Library +import dev.openrs2.asm.nextReal +import dev.openrs2.asm.previousReal +import dev.openrs2.asm.transform.Transformer +import org.objectweb.asm.Opcodes +import org.objectweb.asm.tree.AbstractInsnNode +import org.objectweb.asm.tree.ClassNode +import org.objectweb.asm.tree.InsnNode +import org.objectweb.asm.tree.JumpInsnNode +import org.objectweb.asm.tree.LabelNode +import org.objectweb.asm.tree.MethodNode + +class MonitorTransformer : Transformer() { + private var subroutinesInlined = 0 + private var tryRangesExtended = 0 + private var loadsReplaced = 0 + + override fun preTransform(classPath: ClassPath) { + subroutinesInlined = 0 + tryRangesExtended = 0 + loadsReplaced = 0 + } + + override fun transformCode(classPath: ClassPath, library: Library, clazz: ClassNode, method: MethodNode): Boolean { + inlineSubroutines(method) + extendTryRanges(method) + replaceLoadWithDup(method) + return false + } + + private fun inlineSubroutines(method: MethodNode) { + val subroutines = mutableMapOf>() + for (match in SUBROUTINE_MATCHER.match(method.instructions)) { + subroutines[match[0]] = match + } + + for (match in JSR_MATCHER.match(method.instructions)) { + val jsr = match[1] as JumpInsnNode + val subroutine = subroutines[jsr.label.nextReal] ?: continue + + val ret = subroutine[3] as JumpInsnNode + if (ret.label.nextReal != jsr.nextReal) { + continue + } + + val clonedLabels = emptyMap() + method.instructions.set(match[0], subroutine[1].clone(clonedLabels)) + method.instructions.set(match[1], subroutine[2].clone(clonedLabels)) + + subroutinesInlined++ + } + } + + private fun extendTryRanges(method: MethodNode) { + for (tryCatch in method.tryCatchBlocks) { + if (tryCatch.type != null) { + continue + } + + val monitorenter = tryCatch.start.previousReal ?: continue + if (monitorenter.opcode != Opcodes.MONITORENTER) { + continue + } + + // extend the try to cover the ALOAD and MONTITOREXIT instructions + val aload = tryCatch.end.nextReal ?: continue + if (aload.opcode != Opcodes.ALOAD) { + continue + } + + val monitorexit = aload.nextReal ?: continue + if (monitorexit.opcode != Opcodes.MONITOREXIT) { + continue + } + + val end = monitorexit.nextReal ?: continue + + val label = LabelNode() + method.instructions.insertBefore(end, label) + tryCatch.end = label + + tryRangesExtended++ + } + } + + private fun replaceLoadWithDup(method: MethodNode) { + for (match in LOAD_MATCHER.match(method.instructions)) { + method.instructions.insertBefore(match[0], InsnNode(Opcodes.DUP)) + method.instructions.remove(match[1]) + + loadsReplaced++ + } + } + + override fun postTransform(classPath: ClassPath) { + logger.info { "Inlined $subroutinesInlined MONITOREXIT subroutines" } + logger.info { "Extended $tryRangesExtended try ranges to cover MONITOREXIT instructions" } + logger.info { "Replaced $loadsReplaced ASTORE ALOAD sequences with DUP ASTORE" } + } + + companion object { + private val logger = InlineLogger() + + // these regexes rely on JSRInlinerAdapter running first + private val JSR_MATCHER = InsnMatcher.compile("ACONST_NULL GOTO") + private val SUBROUTINE_MATCHER = InsnMatcher.compile("ASTORE ALOAD MONITOREXIT GOTO") + + private val LOAD_MATCHER = InsnMatcher.compile("ASTORE ALOAD MONITORENTER") + } +}