Deobfuscate stacktraces in log messages using a RewriteAppender and a custom RewritePolicy (#5926)

Also replace a couple calls to `System.err` with logger usages, as traces printed with the former do not get deobfuscated.

patches/server/0026-Prevent-tile-entity-and-entity-crashes.patch

@@ -5,7 +5,7 @@ Subject: [PATCH] Prevent tile entity and entity crashes
 
 
 diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
-index d29334b5dee6fe3f292f774442304b7dc6b0e2f0..d6ed061e36668ea1cbaee44c06575534336008fc 100644
+index d29334b5dee6fe3f292f774442304b7dc6b0e2f0..939f88ab37eca30e8ad08cbe2045b66ee64aa952 100644
 --- a/src/main/java/net/minecraft/world/level/Level.java
 +++ b/src/main/java/net/minecraft/world/level/Level.java
 @@ -729,11 +729,11 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
@@ -18,8 +18,8 @@ index d29334b5dee6fe3f292f774442304b7dc6b0e2f0..d6ed061e36668ea1cbaee44c06575534
 -            entity.fillCrashReportCategory(crashreportsystemdetails);
 -            throw new ReportedException(crashreport);
 +            // Paper start - Prevent tile entity and entity crashes
-+            System.err.println("Entity threw exception at " + entity.level.getWorld().getName() + ":" + entity.getX() + "," + entity.getY() + "," + entity.getZ());
++            final String msg = String.format("Entity threw exception at %s:%s,%s,%s", entity.level.getWorld().getName(), entity.getX(), entity.getY(), entity.getZ());
-+            throwable.printStackTrace();
++            MinecraftServer.LOGGER.error(msg, throwable);
 +            entity.discard();
 +            // Paper end
          }
@@ -44,7 +44,7 @@ index 7b333e2d6884b272abefbc820bcce8026a4cdf7e..66ab4deedd177f507d170a61ceca4c3e
          }
      }
 diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
-index 743aafec1f1c819846813688355dd90534dddb3e..21f613b8d7785b996866b5059f3cb1bc87533d2e 100644
+index 743aafec1f1c819846813688355dd90534dddb3e..5bd2172a88c95722b86959e42442e8a3ab76879c 100644
 --- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
 +++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
 @@ -1241,11 +1241,11 @@ public class LevelChunk implements ChunkAccess {
@@ -57,8 +57,8 @@ index 743aafec1f1c819846813688355dd90534dddb3e..21f613b8d7785b996866b5059f3cb1bc
 -                        this.blockEntity.fillCrashReportCategory(crashreportsystemdetails);
 -                        throw new ReportedException(crashreport);
 +                        // Paper start - Prevent tile entity and entity crashes
-+                        System.err.println("TileEntity threw exception at " + LevelChunk.this.getLevel().getWorld().getName() + ":" + this.getPos().getX() + "," + this.getPos().getY() + "," + this.getPos().getZ());
++                        final String msg = String.format("BlockEntity threw exception at %s:%s,%s,%s", LevelChunk.this.getLevel().getWorld().getName(), this.getPos().getX(), this.getPos().getY(), this.getPos().getZ());
-+                        throwable.printStackTrace();
++                        net.minecraft.server.MinecraftServer.LOGGER.error(msg, throwable);
 +                        LevelChunk.this.removeBlockEntity(this.getPos());
 +                        // Paper end
                          // Spigot start

patches/server/0053-Add-exception-reporting-event.patch

@@ -108,7 +108,7 @@ index 08c5f6fd1a307c89cf8365f56314a0c6d3e89e4b..26e0f03f2e736ed6ba86e2510a7962de
              }
  
 diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
-index da8e6f5b48a83ca4178c0de439200b7952f409d9..969a5ed2484036103834dc23b57b33c11896d72f 100644
+index 718f31b74207c7ef06c1861fbc58de01cf67be3b..dda9ac55bd7b8cce055eac1f067d7ab70ed4dca7 100644
 --- a/src/main/java/net/minecraft/world/level/Level.java
 +++ b/src/main/java/net/minecraft/world/level/Level.java
 @@ -1,5 +1,10 @@
@@ -122,14 +122,10 @@ index da8e6f5b48a83ca4178c0de439200b7952f409d9..969a5ed2484036103834dc23b57b33c1
  import com.google.common.collect.Lists;
  import com.mojang.serialization.Codec;
  import java.io.IOException;
-@@ -729,8 +734,10 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
+@@ -731,6 +736,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
-             tickConsumer.accept(entity);
-         } catch (Throwable throwable) {
              // Paper start - Prevent tile entity and entity crashes
--            System.err.println("Entity threw exception at " + entity.level.getWorld().getName() + ":" + entity.getX() + "," + entity.getY() + "," + entity.getZ());
+             final String msg = String.format("Entity threw exception at %s:%s,%s,%s", entity.level.getWorld().getName(), entity.getX(), entity.getY(), entity.getZ());
-+            String msg = "Entity threw exception at " + entity.level.getWorld().getName() + ":" + entity.getX() + "," + entity.getY() + "," + entity.getZ();
+             MinecraftServer.LOGGER.error(msg, throwable);
-+            System.err.println(msg);
-             throwable.printStackTrace();
 +            getCraftServer().getPluginManager().callEvent(new ServerExceptionEvent(new ServerInternalException(msg, throwable)));
              entity.discard();
              // Paper end
@@ -155,7 +151,7 @@ index b4a7776ba9486bbca42ffb596c8a8bcdf6471ce3..59fae60116167baf989e85596334824e
                                  }
  
 diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
-index 21f613b8d7785b996866b5059f3cb1bc87533d2e..249f39bc0c5820e313cad7813bd1087cb2e09ed6 100644
+index 5bd2172a88c95722b86959e42442e8a3ab76879c..bf5a039553a31ed6e9d9bfa64cbd435b3e551a08 100644
 --- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
 +++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
 @@ -1,6 +1,7 @@
@@ -186,14 +182,10 @@ index 21f613b8d7785b996866b5059f3cb1bc87533d2e..249f39bc0c5820e313cad7813bd1087c
              // CraftBukkit end
          }
      }
-@@ -1242,8 +1248,10 @@ public class LevelChunk implements ChunkAccess {
+@@ -1244,6 +1250,7 @@ public class LevelChunk implements ChunkAccess {
-                         gameprofilerfiller.pop();
-                     } catch (Throwable throwable) {
                          // Paper start - Prevent tile entity and entity crashes
--                        System.err.println("TileEntity threw exception at " + LevelChunk.this.getLevel().getWorld().getName() + ":" + this.getPos().getX() + "," + this.getPos().getY() + "," + this.getPos().getZ());
+                         final String msg = String.format("BlockEntity threw exception at %s:%s,%s,%s", LevelChunk.this.getLevel().getWorld().getName(), this.getPos().getX(), this.getPos().getY(), this.getPos().getZ());
-+                        String msg = "TileEntity threw exception at " + LevelChunk.this.getLevel().getWorld().getName() + ":" + this.getPos().getX() + "," + this.getPos().getY() + "," + this.getPos().getZ();
+                         net.minecraft.server.MinecraftServer.LOGGER.error(msg, throwable);
-+                        System.err.println(msg);
-                         throwable.printStackTrace();
 +                        net.minecraft.world.level.chunk.LevelChunk.this.level.getCraftServer().getPluginManager().callEvent(new com.destroystokyo.paper.event.server.ServerExceptionEvent(new ServerInternalException(msg, throwable)));
                          LevelChunk.this.removeBlockEntity(this.getPos());
                          // Paper end

patches/server/0232-Option-to-prevent-armor-stands-from-doing-entity-loo.patch

@@ -31,10 +31,10 @@ index 6d717d3852afb3a3a4bef30c68980c402bdfefff..b47b1215e685c453c3496439bb350a91
  
          for (int i = 0; i < list.size(); ++i) {
 diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
-index 08f612b7d2e861ef7e8b91e622c7a278542809f0..00e5672f4d302d5ccfe3942e61fe0c0beb782b82 100644
+index 45a9c7d5b8999d1abd7f5ef805f068f5b532dcfa..00e6ad6ce3bc8e4542284f426fd601abb669b57d 100644
 --- a/src/main/java/net/minecraft/world/level/Level.java
 +++ b/src/main/java/net/minecraft/world/level/Level.java
-@@ -768,6 +768,13 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
+@@ -767,6 +767,13 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
              // Paper end
          }
      }

patches/server/0323-Optimize-Captured-TileEntity-Lookup.patch

@@ -10,10 +10,10 @@ Optimize to check if the captured list even has values in it, and also to
 just do a get call since the value can never be null.
 
 diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
-index c85f6fedfaf756f8b17b554bcb2d94d0f00f01f1..5d021fbaeeb2655a775053225a9614d7881331c4 100644
+index 8076ad15b67d86b38ba61d701df921b0f615fd80..5b06aa23191d5e78cee7ac167ea39446c6c25b95 100644
 --- a/src/main/java/net/minecraft/world/level/Level.java
 +++ b/src/main/java/net/minecraft/world/level/Level.java
-@@ -871,9 +871,12 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
+@@ -870,9 +870,12 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
  
      @Nullable
      public BlockEntity getTileEntity(BlockPos blockposition, boolean validate) {

patches/server/0367-Anti-Xray.patch

@@ -1118,7 +1118,7 @@ index badac53382c776eba3efccfda42283912d07b99a..06e581bc0c0ea4e8141f7b9610cc5a7e
          }
  
 diff --git a/src/main/java/net/minecraft/server/level/ServerLevel.java b/src/main/java/net/minecraft/server/level/ServerLevel.java
-index 22db34272c6635438d11f525fb4f08e2aa631f55..fcf5c7b28e927db977ad5b851edaf68e59de8d5b 100644
+index 39997c5028fe51e2fefbd2d50353575080d92f3c..950182275f2e95c5d2ac5e715b968e86c3bdeb93 100644
 --- a/src/main/java/net/minecraft/server/level/ServerLevel.java
 +++ b/src/main/java/net/minecraft/server/level/ServerLevel.java
 @@ -292,7 +292,7 @@ public class ServerLevel extends net.minecraft.world.level.Level implements Worl
@@ -1153,7 +1153,7 @@ index f4a056185990181e486f452960159a5287947382..a695e5a0c2e8846333ccb9aea499b565
  
      public void destroyAndAck(BlockPos pos, ServerboundPlayerActionPacket.Action action, String reason) {
 diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
-index 580b3d7d993751e7c04e6b7d5d4d8fa9d150d383..83673e66aab4988e912d78fb8d1a45f807e38bd9 100644
+index 6d9c74595cd8883167554e8b52008a99d6e113c3..afdbec2365db55ab968b15368ae9ce239b63f373 100644
 --- a/src/main/java/net/minecraft/world/level/Level.java
 +++ b/src/main/java/net/minecraft/world/level/Level.java
 @@ -164,6 +164,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
@@ -1229,7 +1229,7 @@ index 69c2454533e6f21c70792b555ec02c6bc6d169b3..2607c7ba5cf1aca5f3e5c22be2e4e8b3
  
          @Override
 diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
-index 8cc0f2a74191357ab52f30439a515709f8ab80d1..fbb82d344f654b90809582916442c520f344aa39 100644
+index 0530de6e9167419b180a3fd6e890d27d9d86c04c..2accbda808b485fa75011b7493567138b0945096 100644
 --- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
 +++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
 @@ -456,7 +456,7 @@ public class LevelChunk implements ChunkAccess {
@@ -1241,7 +1241,7 @@ index 8cc0f2a74191357ab52f30439a515709f8ab80d1..fbb82d344f654b90809582916442c520
              this.sections[j] = chunksection;
          }
  
-@@ -1307,4 +1307,11 @@ public class LevelChunk implements ChunkAccess {
+@@ -1306,4 +1306,11 @@ public class LevelChunk implements ChunkAccess {
              return "Level ticker for " + s + "@" + this.getPos();
          }
      }
@@ -1448,7 +1448,7 @@ index 64cb0658021866c3875d145cc4266896e57c081e..f0c537e1d6b32ecde52b3d456f0f3889
      @Override
      public FluidState getFluidIfLoaded(BlockPos blockposition) {
 diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
-index c131f6093c395b4d9e401d3c447e7fb13c631ecf..c09a1c640075bde9f656b11258f5adbd2daa4b0b 100644
+index abd02d88911cbbbe6f770039aa0649cff85d85ee..9db83a8f2eceac41f6b86430e719bad1a12471b5 100644
 --- a/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
 +++ b/src/main/java/net/minecraft/world/level/chunk/storage/ChunkSerializer.java
 @@ -136,7 +136,7 @@ public class ChunkSerializer {

patches/server/0373-Avoid-hopper-searches-if-there-are-no-items.patch

@@ -14,10 +14,10 @@ And since minecart hoppers are used _very_ rarely near we can avoid alot of sear
 Combined, this adds up a lot.
 
 diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
-index d58a7adb58abc91f66fc893ee7a7a7bded3619a8..af1cee79e27667b78413760286f517c91d1517cb 100644
+index 864b3efc014bf1c499257d01a7e8bce910ae85d0..7ffe9718188ba57cb2a7b934a40d5f893543a63a 100644
 --- a/src/main/java/net/minecraft/world/level/Level.java
 +++ b/src/main/java/net/minecraft/world/level/Level.java
-@@ -990,7 +990,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
+@@ -989,7 +989,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
                  }
              }
  

patches/server/0404-Improved-Watchdog-Support.patch

@@ -299,7 +299,7 @@ index 7bf4bf5cb2c1b54a7e2733091f48f3a824336d36..dcce05d2f4ab16424db4ab103a12188e
          }
  
 diff --git a/src/main/java/net/minecraft/world/level/Level.java b/src/main/java/net/minecraft/world/level/Level.java
-index af1cee79e27667b78413760286f517c91d1517cb..c84070d05d325a8f49c3918cc112087b9c1074e9 100644
+index 7ffe9718188ba57cb2a7b934a40d5f893543a63a..c407e85bd16b8f91b262bd6528253f902cbf9af6 100644
 --- a/src/main/java/net/minecraft/world/level/Level.java
 +++ b/src/main/java/net/minecraft/world/level/Level.java
 @@ -843,6 +843,7 @@ public abstract class Level implements LevelAccessor, AutoCloseable {
@@ -308,10 +308,10 @@ index af1cee79e27667b78413760286f517c91d1517cb..c84070d05d325a8f49c3918cc112087b
          } catch (Throwable throwable) {
 +            if (throwable instanceof ThreadDeath) throw throwable; // Paper
              // Paper start - Prevent tile entity and entity crashes
-             String msg = "Entity threw exception at " + entity.level.getWorld().getName() + ":" + entity.getX() + "," + entity.getY() + "," + entity.getZ();
+             final String msg = String.format("Entity threw exception at %s:%s,%s,%s", entity.level.getWorld().getName(), entity.getX(), entity.getY(), entity.getZ());
-             System.err.println(msg);
+             MinecraftServer.LOGGER.error(msg, throwable);
 diff --git a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
-index e19f5d5d58a8b2e4f35907e1c88224cac7f20e57..61c70e17401ec85c0a7e6e1793f6689506b8059a 100644
+index a1f763536d77065e1ce779733a505df43be225ae..5c83bc6e5fbf10989f72c7210d3528daa9966f04 100644
 --- a/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
 +++ b/src/main/java/net/minecraft/world/level/chunk/LevelChunk.java
 @@ -1319,6 +1319,7 @@ public class LevelChunk implements ChunkAccess {
@@ -320,8 +320,8 @@ index e19f5d5d58a8b2e4f35907e1c88224cac7f20e57..61c70e17401ec85c0a7e6e1793f66895
                      } catch (Throwable throwable) {
 +                        if (throwable instanceof ThreadDeath) throw throwable; // Paper
                          // Paper start - Prevent tile entity and entity crashes
-                         String msg = "TileEntity threw exception at " + LevelChunk.this.getLevel().getWorld().getName() + ":" + this.getPos().getX() + "," + this.getPos().getY() + "," + this.getPos().getZ();
+                         final String msg = String.format("BlockEntity threw exception at %s:%s,%s,%s", LevelChunk.this.getLevel().getWorld().getName(), this.getPos().getX(), this.getPos().getY(), this.getPos().getZ());
-                         System.err.println(msg);
+                         net.minecraft.server.MinecraftServer.LOGGER.error(msg, throwable);
 diff --git a/src/main/java/org/bukkit/craftbukkit/CraftServer.java b/src/main/java/org/bukkit/craftbukkit/CraftServer.java
 index 2f7ab3142f44c657f3585c8f8a6872fbfac81768..a7d087875ec2d493ef6ed0fcdc03d89445d9008b 100644
 --- a/src/main/java/org/bukkit/craftbukkit/CraftServer.java

patches/server/0717-Deobfuscate-stacktraces-in-log-messages-using-a-Rewr.patch

@@ -0,0 +1,384 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
+Date: Sun, 20 Jun 2021 18:19:09 -0700
+Subject: [PATCH] Deobfuscate stacktraces in log messages using a
+ RewriteAppender and a custom RewritePolicy
+
+
+diff --git a/build.gradle.kts b/build.gradle.kts
+index 04938bb10c35d2e424043adb7ed8fec2e42bb816..f427c6f5adf20f9e1b1fa4ab56041506d8240c92 100644
+--- a/build.gradle.kts
++++ b/build.gradle.kts
+@@ -1,8 +1,12 @@
+ import com.github.jengelman.gradle.plugins.shadow.transformers.Log4j2PluginsCacheFileTransformer
+ import com.github.jengelman.gradle.plugins.shadow.transformers.Transformer
++import io.papermc.paperweight.tasks.BaseTask
+ import io.papermc.paperweight.util.Git
++import io.papermc.paperweight.util.defaultOutput
++import io.papermc.paperweight.util.openZip
+ import io.papermc.paperweight.util.path
+ import shadow.org.apache.logging.log4j.core.config.plugins.processor.PluginProcessor.PLUGIN_CACHE_FILE
++import java.nio.file.Files
+ import java.text.SimpleDateFormat
+ import java.util.Date
+ import java.util.Locale
+@@ -15,6 +19,14 @@ plugins {
+ 
+ repositories {
+     maven("https://libraries.minecraft.net/")
++    // Paper start
++    maven("https://maven.quiltmc.org/repository/release/") {
++        mavenContent {
++            releasesOnly()
++            includeModule("org.quiltmc", "tiny-mappings-parser")
++        }
++    }
++    // Paper end
+ }
+ 
+ dependencies {
+@@ -52,6 +64,8 @@ dependencies {
+ 
+     implementation("com.github.oshi:oshi-core:5.7.5") // Paper - fix startup delay and warning
+ 
++    implementation("org.quiltmc:tiny-mappings-parser:0.3.0") // Paper - needed to read mappings for stacktrace deobfuscation
++
+     testImplementation("io.github.classgraph:classgraph:4.8.47") // Paper - mob goal test
+     testImplementation("junit:junit:4.13.1")
+     testImplementation("org.hamcrest:hamcrest-library:1.3")
+@@ -115,6 +129,44 @@ tasks.shadowJar {
+     transform(ModifiedLog4j2PluginsCacheFileTransformer::class.java)
+ }
+ 
++// Paper start - include reobf mappings in jar for stacktrace deobfuscation
++abstract class IncludeMappings : BaseTask() {
++    @get:InputFile
++    abstract val inputJar: RegularFileProperty
++
++    @get:InputFile
++    abstract val mappings: RegularFileProperty
++
++    @get:OutputFile
++    abstract val outputJar: RegularFileProperty
++
++    override fun init() {
++        outputJar.convention(defaultOutput())
++    }
++
++    @TaskAction
++    private fun addMappings() {
++        outputJar.get().asFile.parentFile.mkdirs()
++        inputJar.get().asFile.copyTo(outputJar.get().asFile, overwrite = true)
++        outputJar.get().path.openZip().use { fs ->
++            val dir = fs.getPath("META-INF/mappings/")
++            Files.createDirectories(dir)
++            val target = dir.resolve("reobf.tiny")
++            Files.copy(mappings.path, target)
++        }
++    }
++}
++
++val includeMappings = tasks.register<IncludeMappings>("includeMappings") {
++    inputJar.set(tasks.shadowJar.flatMap { it.archiveFile })
++    mappings.set(tasks.reobfJar.flatMap { it.mappingsFile })
++}
++
++tasks.reobfJar {
++    inputJar.set(includeMappings.flatMap { it.outputJar })
++}
++// Paper end - include reobf mappings in jar for stacktrace deobfuscation
++
+ tasks.test {
+     exclude("org/bukkit/craftbukkit/inventory/ItemStack*Test.class")
+ }
+diff --git a/src/main/java/com/destroystokyo/paper/PaperConfig.java b/src/main/java/com/destroystokyo/paper/PaperConfig.java
+index 7acf077bc131af718c7548cc29deef558c04e463..73652e403eaa419fb5b4b54bd506f246c0aa4e99 100644
+--- a/src/main/java/com/destroystokyo/paper/PaperConfig.java
++++ b/src/main/java/com/destroystokyo/paper/PaperConfig.java
+@@ -487,6 +487,11 @@ public class PaperConfig {
+         enableBrigadierConsoleCompletions = getBoolean("settings.console.enable-brigadier-completions", enableBrigadierConsoleCompletions);
+     }
+ 
++    public static boolean deobfuscateStacktraces = true;
++    private static void loggerSettings() {
++        deobfuscateStacktraces = getBoolean("settings.loggers.deobfuscate-stacktraces", deobfuscateStacktraces);
++    }
++
+     public static int itemValidationDisplayNameLength = 8192;
+     public static int itemValidationLocNameLength = 8192;
+     public static int itemValidationLoreLineLength = 8192;
+diff --git a/src/main/java/io/papermc/paper/logging/StacktraceDeobfuscatingRewritePolicy.java b/src/main/java/io/papermc/paper/logging/StacktraceDeobfuscatingRewritePolicy.java
+new file mode 100644
+index 0000000000000000000000000000000000000000..5293a59d17eeb711694965816857e66481ff0277
+--- /dev/null
++++ b/src/main/java/io/papermc/paper/logging/StacktraceDeobfuscatingRewritePolicy.java
+@@ -0,0 +1,242 @@
++package io.papermc.paper.logging;
++
++import com.destroystokyo.paper.PaperConfig;
++import com.google.common.base.Charsets;
++import com.google.common.collect.ImmutableMap;
++import com.mojang.datafixers.util.Pair;
++import it.unimi.dsi.fastutil.ints.IntArrayList;
++import it.unimi.dsi.fastutil.ints.IntList;
++import java.io.BufferedReader;
++import java.io.IOException;
++import java.io.InputStream;
++import java.io.InputStreamReader;
++import java.util.Collections;
++import java.util.HashMap;
++import java.util.LinkedHashMap;
++import java.util.Map;
++import net.fabricmc.mapping.tree.ClassDef;
++import net.fabricmc.mapping.tree.MethodDef;
++import net.fabricmc.mapping.tree.TinyMappingFactory;
++import net.fabricmc.mapping.tree.TinyTree;
++import org.apache.logging.log4j.core.Core;
++import org.apache.logging.log4j.core.LogEvent;
++import org.apache.logging.log4j.core.appender.rewrite.RewritePolicy;
++import org.apache.logging.log4j.core.config.plugins.Plugin;
++import org.apache.logging.log4j.core.config.plugins.PluginFactory;
++import org.jetbrains.annotations.NotNull;
++import org.jetbrains.annotations.Nullable;
++import org.objectweb.asm.ClassReader;
++import org.objectweb.asm.ClassVisitor;
++import org.objectweb.asm.Label;
++import org.objectweb.asm.MethodVisitor;
++import org.objectweb.asm.Opcodes;
++
++@Plugin(
++    name = "StacktraceDeobfuscatingRewritePolicy",
++    category = Core.CATEGORY_NAME,
++    elementType = "rewritePolicy",
++    printObject = true
++)
++public final class StacktraceDeobfuscatingRewritePolicy implements RewritePolicy {
++    private static final String MOJANG_PLUS_YARN_NAMESPACE = "mojang+yarn";
++    private static final String SPIGOT_NAMESPACE = "spigot";
++
++    private final @Nullable Map<String, ClassMapping> mappings;
++    private final Map<Class<?>, Map<Pair<String, String>, IntList>> lineMapCache = Collections.synchronizedMap(new LinkedHashMap<>(64, 0.75f, true) {
++        @Override
++        protected boolean removeEldestEntry(final Map.Entry<Class<?>, Map<Pair<String, String>, IntList>> eldest) {
++            return this.size() > 63;
++        }
++    });
++
++    StacktraceDeobfuscatingRewritePolicy() {
++        this.mappings = loadMappingsIfPresent();
++    }
++
++    private static @Nullable Map<String, ClassMapping> loadMappingsIfPresent() {
++        try (final InputStream mappingsInputStream = StacktraceDeobfuscatingRewritePolicy.class.getClassLoader().getResourceAsStream("mappings/reobf.tiny")) {
++            if (mappingsInputStream == null) {
++                return null;
++            }
++            final TinyTree tree = TinyMappingFactory.loadWithDetection(new BufferedReader(new InputStreamReader(mappingsInputStream, Charsets.UTF_8)));
++            final var builder = ImmutableMap.<String, ClassMapping>builder();
++
++            for (final ClassDef classDef : tree.getClasses()) {
++                final String obfClassName = classDef.getName(SPIGOT_NAMESPACE).replace('/', '.');
++                final var methodMappings = ImmutableMap.<Pair<String, String>, MethodMapping>builder();
++
++                for (final MethodDef methodDef : classDef.getMethods()) {
++                    final MethodMapping method = new MethodMapping(
++                        methodDef.getName(SPIGOT_NAMESPACE),
++                        methodDef.getName(MOJANG_PLUS_YARN_NAMESPACE),
++                        methodDef.getDescriptor(SPIGOT_NAMESPACE)
++                    );
++                    methodMappings.put(
++                        new Pair<>(method.obfName(), method.descriptor()),
++                        method
++                    );
++                }
++
++                final ClassMapping map = new ClassMapping(
++                    obfClassName,
++                    classDef.getName(MOJANG_PLUS_YARN_NAMESPACE).replace('/', '.'),
++                    methodMappings.build()
++                );
++                builder.put(map.obfName(), map);
++            }
++
++            return builder.build();
++        } catch (final IOException ex) {
++            System.err.println("Failed to load mappings for stacktrace deobfuscation.");
++            ex.printStackTrace();
++            return null;
++        }
++    }
++
++    @Override
++    public @NotNull LogEvent rewrite(final @NotNull LogEvent rewrite) {
++        if (!PaperConfig.deobfuscateStacktraces) {
++            return rewrite;
++        }
++
++        final Throwable thrown = rewrite.getThrown();
++        if (thrown != null) {
++            this.deobfuscateThrowable(thrown);
++        }
++        return rewrite;
++    }
++
++    public void deobfuscateThrowable(final Throwable throwable) {
++        throwable.setStackTrace(this.deobfuscateStacktrace(throwable.getStackTrace()));
++        final Throwable cause = throwable.getCause();
++        if (cause != null) {
++            this.deobfuscateThrowable(cause);
++        }
++        for (final Throwable suppressed : throwable.getSuppressed()) {
++            this.deobfuscateThrowable(suppressed);
++        }
++    }
++
++    public StackTraceElement[] deobfuscateStacktrace(final StackTraceElement[] traceElements) {
++        if (this.mappings == null || traceElements.length == 0) {
++            return traceElements;
++        }
++        final StackTraceElement[] result = new StackTraceElement[traceElements.length];
++        for (int i = 0; i < traceElements.length; i++) {
++            final StackTraceElement element = traceElements[i];
++
++            final String className = element.getClassName();
++            final String methodName = element.getMethodName();
++
++            final ClassMapping classMapping = this.mappings.get(className);
++            if (classMapping == null) {
++                result[i] = element;
++                continue;
++            }
++
++            final Pair<String, String> nameDescriptorPair;
++            try {
++                final Class<?> clazz = Class.forName(className);
++                nameDescriptorPair = this.determineMethodForLine(clazz, element.getLineNumber());
++            } catch (final ReflectiveOperationException ex) {
++                throw new RuntimeException(ex);
++            }
++
++            final MethodMapping methodMapping = classMapping.methodMappings().get(nameDescriptorPair);
++
++            result[i] = new StackTraceElement(
++                element.getClassLoaderName(),
++                element.getModuleName(),
++                element.getModuleVersion(),
++                classMapping.mojangName(),
++                methodMapping != null ? methodMapping.mojangName() : methodName,
++                this.mappedFileName(classMapping.mojangName()),
++                element.getLineNumber()
++            );
++        }
++        return result;
++    }
++
++    private static @NotNull Map<Pair<String, String>, IntList> buildLineMap(final @NotNull Class<?> key) {
++        final Map<Pair<String, String>, IntList> lineMap = new HashMap<>();
++        final class LineCollectingMethodVisitor extends MethodVisitor {
++            private final IntList lines = new IntArrayList();
++            private final String name;
++            private final String descriptor;
++
++            LineCollectingMethodVisitor(String name, String descriptor) {
++                super(Opcodes.ASM9);
++                this.name = name;
++                this.descriptor = descriptor;
++            }
++
++            @Override
++            public void visitLineNumber(int line, Label start) {
++                super.visitLineNumber(line, start);
++                this.lines.add(line);
++            }
++
++            @Override
++            public void visitEnd() {
++                super.visitEnd();
++                lineMap.put(new Pair<>(this.name, this.descriptor), this.lines);
++            }
++        }
++        final ClassVisitor classVisitor = new ClassVisitor(Opcodes.ASM9) {
++            @Override
++            public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
++                return new LineCollectingMethodVisitor(name, descriptor);
++            }
++        };
++        try {
++            final ClassReader reader = new ClassReader(key.getName());
++            reader.accept(classVisitor, 0);
++        } catch (final IOException ex) {
++            throw new RuntimeException(ex);
++        }
++        return lineMap;
++    }
++
++    private @Nullable Pair<String, String> determineMethodForLine(final @NotNull Class<?> clazz, final int lineNumber) {
++        final Map<Pair<String, String>, IntList> lineMap = this.lineMapCache.computeIfAbsent(clazz, StacktraceDeobfuscatingRewritePolicy::buildLineMap);
++        for (final var entry : lineMap.entrySet()) {
++            final Pair<String, String> pair = entry.getKey();
++            final IntList lines = entry.getValue();
++            for (int i = 0, linesSize = lines.size(); i < linesSize; i++) {
++                final int num = lines.getInt(i);
++                if (num == lineNumber) {
++                    return pair;
++                }
++            }
++        }
++        return null;
++    }
++
++    private @NotNull String mappedFileName(final @NotNull String fullClassName) {
++        final int dot = fullClassName.lastIndexOf('.');
++        final String className = dot == -1
++            ? fullClassName
++            : fullClassName.substring(dot + 1);
++        final String rootClassName = className.split("\\$")[0];
++        return rootClassName + ".java";
++    }
++
++    @PluginFactory
++    public static @NotNull StacktraceDeobfuscatingRewritePolicy createPolicy() {
++        return new StacktraceDeobfuscatingRewritePolicy();
++    }
++
++    private record ClassMapping(
++        String obfName,
++        String mojangName,
++        Map<Pair<String, String>, MethodMapping> methodMappings
++    ) {
++    }
++
++    private record MethodMapping(
++        String obfName,
++        String mojangName,
++        String descriptor
++    ) {
++    }
++}
+diff --git a/src/main/resources/log4j2.xml b/src/main/resources/log4j2.xml
+index 67da1aa7a21622fb231d19dede3775a282a4a12e..f91d0df569b2f1d430ea5eee5f53779902a4f32c 100644
+--- a/src/main/resources/log4j2.xml
++++ b/src/main/resources/log4j2.xml
+@@ -29,15 +29,19 @@
+             </Policies>
+             <DefaultRolloverStrategy max="1000"/>
+         </RollingRandomAccessFile>
++        <Rewrite name="rewrite">
++            <StacktraceDeobfuscatingRewritePolicy />
++            <AppenderRef ref="File"/>
++            <AppenderRef ref="TerminalConsole" level="info"/>
++            <AppenderRef ref="ServerGuiConsole" level="info"/>
++        </Rewrite>
+     </Appenders>
+     <Loggers>
+         <Root level="info">
+             <filters>
+                 <MarkerFilter marker="NETWORK_PACKETS" onMatch="DENY" onMismatch="NEUTRAL" />
+             </filters>
+-            <AppenderRef ref="File"/>
+-            <AppenderRef ref="TerminalConsole" level="info"/>
+-            <AppenderRef ref="ServerGuiConsole" level="info"/>
++            <AppenderRef ref="rewrite"/>
+         </Root>
+     </Loggers>
+ </Configuration>