Wasm name section output format (#388)

Author: thegu5

Cpp2IL.Core/Cpp2IlCorePlugin.cs

@@ -49,6 +49,7 @@ public override void OnLoad()
         OutputFormatRegistry.Register<DiffableCsOutputFormat>();
         OutputFormatRegistry.Register<IsilDumpOutputFormat>();
         OutputFormatRegistry.Register<WasmMappingOutputFormat>();
+        OutputFormatRegistry.Register<WasmNameSectionOutputFormat>();
 
         Logger.VerboseNewline("\tRegistering built-in processing layers", "Core Plugin");
 

Cpp2IL.Core/OutputFormats/WasmNameSectionOutputFormat.cs

@@ -0,0 +1,146 @@
+using System;
+using System.IO;
+using System.Linq;
+using System.Text;
+using Cpp2IL.Core.Api;
+using Cpp2IL.Core.Logging;
+using Cpp2IL.Core.Model.Contexts;
+using Cpp2IL.Core.Utils;
+using LibCpp2IL;
+using LibCpp2IL.Wasm;
+
+namespace Cpp2IL.Core.OutputFormats;
+
+public class WasmNameSectionOutputFormat : Cpp2IlOutputFormat
+{
+    public override string OutputFormatId => "wasm_name_section";
+    public override string OutputFormatName => "Webassembly name section";
+
+    public override void DoOutput(ApplicationAnalysisContext context, string outputRoot)
+    {
+        // Outputs a binary file matching the standardized "name" WebAssembly custom section.
+        // If the game's binary doesn't already have the same type of section (which is practically always),
+        // all that's needed to combine the two is a simple `cat main.wasm section.dat > out.wasm`.
+        // Using this modified binary in place of the original one provides extra information for debuggers.
+
+        // The spec can be found here: https://webassembly.github.io/spec/core/appendix/custom.html#name-section
+        // Some additional subsections have been proposed (already implemented in v8 & spidermonkey), but they don't seem to be helpful as of now.
+        // The proposal overview can be found here: https://github.com/WebAssembly/extended-name-section/blob/main/proposals/extended-name-section/Overview.md
+
+        if (context.Binary.GetType() != typeof(WasmFile))
+            throw new Exception("This output format only works with WebAssembly files");
+
+        if (!Directory.Exists(outputRoot))
+            Directory.CreateDirectory(outputRoot);
+
+        var outputFile = File.Create(Path.Combine(outputRoot, "namesection.dat"));
+
+        var section =
+            new MemoryStream(); // This stream is separate from outputFile because we need to know the size of the section before writing it
+        section.WriteName("name"); // The section's name (`name`)
+
+        var moduleNameSubsection = new MemoryStream();
+        moduleNameSubsection.WriteName("Unity");
+        section.WriteSizedData(moduleNameSubsection, 0x0); // Subsection id 0
+        moduleNameSubsection.Dispose();
+
+        var paramSuccessCount = 0;
+        var paramFailCount = 0;
+
+        var functionData = context.AllTypes.SelectMany(t => t.Methods)
+            .Select(method => (method, definition: WasmUtils.TryGetWasmDefinition(method)))
+            .Where(v => v.definition is not null)
+            .Select(v =>
+            {
+                var trueParamCount = v.definition!.GetType((WasmFile)LibCpp2IlMain.Binary!).ParamTypes.Length;
+
+                // Also see WasmUtils.BuildSignature
+                var parameters = v.method.Parameters.Select(param => param.Name).ToList();
+
+                if (!v.method.IsStatic)
+                    parameters.Insert(0, "this");
+
+                if (v.method.ReturnTypeContext is
+                    { IsValueType: true, IsPrimitive: true, Definition: null or { Size: > 8 } })
+                    parameters.Insert(0, "out");
+
+                parameters.Add("methodInfo"); // Only for some methods...?
+
+                if (trueParamCount != parameters.Count)
+                {
+                    // Logger.WarnNewline($"Failed param matching for {v.method.FullNameWithSignature}, calculated {parameters.Count} with there actually being {trueParamCount} ({string.Join(" ", parameters)})");
+                    parameters.Clear();
+                    paramFailCount++;
+                }
+                else
+                {
+                    paramSuccessCount++;
+                }
+
+                return (
+                    Index: v.definition!.FunctionTableIndex,
+                    Name: v.method.FullName,
+                    Parameters: parameters
+                );
+            })
+            .GroupBy(v => v.Index)
+            .OrderBy(grouping => grouping.Key)
+            .ToDictionary(
+                grouping => grouping.Key,
+                grouping => grouping.Select(v => (v.Name, v.Parameters)).ToList()
+            );
+        
+        Logger.InfoNewline(
+            $"Estimated parameter naming success rate: {(float)paramSuccessCount / (paramSuccessCount + paramFailCount) * 100:N2}%");
+
+        var functionNameSubsection = new MemoryStream();
+        functionNameSubsection.WriteLEB128Unsigned((ulong)functionData.Count); // vector length
+
+        var localNameSubsection = new MemoryStream();
+        localNameSubsection.WriteLEB128Unsigned((ulong)functionData.Count); // vector length
+
+        foreach (var (idx, data) in functionData)
+        {
+            functionNameSubsection.WriteLEB128Unsigned((ulong)idx);
+            localNameSubsection.WriteLEB128Unsigned((ulong)idx);
+
+            functionNameSubsection.WriteName(data.Count == 1 ? data[0].Name : $"multiple_{data.Count}_{data[0].Name}");
+
+            localNameSubsection.WriteLEB128Unsigned((ulong)data[0].Parameters.Count); // vector length
+            for (var i = 0; i < data[0].Parameters.Count; i++)
+            {
+                localNameSubsection.WriteLEB128Unsigned((ulong)i);
+                // Possible to include type here, but may make names excessively long
+                localNameSubsection.WriteName(data.Count == 1
+                    ? data[0].Parameters[i]
+                    : $"multiple_{data.Count}_{data[0].Parameters[i]}");
+            }
+        }
+
+        section.WriteSizedData(functionNameSubsection, 0x1); // Subsection id 1
+        section.WriteSizedData(localNameSubsection, 0x2); // Subsection id 2
+
+        outputFile.WriteSizedData(section, 0x0); // Section id 0 - custom
+    }
+}
+
+public static class Extensions
+{
+    public static void WriteName(this Stream memoryStream, string name)
+    {
+        var bytes = Encoding.Default.GetBytes(name);
+        memoryStream.WriteLEB128Unsigned((ulong)bytes.Length);
+        memoryStream.Write(bytes, 0, bytes.Length);
+    }
+
+    public static void WriteSizedData(this Stream memoryStream, MemoryStream data, byte? prependByte = null)
+    {
+        if (prependByte.HasValue)
+        {
+            memoryStream.WriteByte(prependByte.Value);
+        }
+
+        memoryStream.WriteLEB128Unsigned((ulong)data.Length);
+        data.WriteTo(memoryStream);
+    }
+}