[wasm] Endian fix for Webcil

'dotnet new blazorwasm' command failed on s390x and was throwing a not implemented exception

The issue was with with the WebCil writer and reader, specific endianness conversions relating to the webcil payload were not implemented for big endian machines.

We considered fixing the generic implementation, but there were only two structures in use: WebcilHeader and WebcilSectionHeader, so it was easier to handle them explicitly.

Author: saitama951

src/tasks/Microsoft.NET.WebAssembly.Webcil/Microsoft.NET.WebAssembly.Webcil.csproj

@@ -16,6 +16,7 @@
 
   <ItemGroup>
     <!-- we need to keep the version of System.Reflection.Metadata in sync with dotnet/msbuild and dotnet/sdk -->
+    <PackageReference Include="System.Memory" Version="$(SystemMemoryVersion)" /> 
     <PackageReference Include="System.Reflection.Metadata" Version="$(SystemReflectionMetadataVersion)" />
     <PackageReference Include="System.Collections.Immutable" Version="$(SystemCollectionsImmutableVersion)" />
   </ItemGroup>

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilConverter.cs

@@ -2,6 +2,7 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 using System;
+using System.Buffers.Binary;
 using System.IO;
 using System.Collections.Immutable;
 using System.Reflection.PortableExecutable;
@@ -181,9 +182,6 @@ private static void WriteHeader(Stream s, WebcilHeader header)
 
     private static void WriteSectionHeaders(Stream s, ImmutableArray<WebcilSectionHeader> sectionsHeaders)
     {
-        // FIXME: fixup endianness
-        if (!BitConverter.IsLittleEndian)
-            throw new NotImplementedException();
         foreach (var sectionHeader in sectionsHeaders)
         {
             WriteSectionHeader(s, sectionHeader);
@@ -192,16 +190,38 @@ private static void WriteSectionHeaders(Stream s, ImmutableArray<WebcilSectionHe
 
     private static void WriteSectionHeader(Stream s, WebcilSectionHeader sectionHeader)
     {
+        if (!BitConverter.IsLittleEndian)
+        {
+            sectionHeader = new WebcilSectionHeader
+            (
+                virtualSize: BinaryPrimitives.ReverseEndianness(sectionHeader.VirtualSize),
+                virtualAddress: BinaryPrimitives.ReverseEndianness(sectionHeader.VirtualAddress),
+                sizeOfRawData: BinaryPrimitives.ReverseEndianness(sectionHeader.SizeOfRawData),
+                pointerToRawData: BinaryPrimitives.ReverseEndianness(sectionHeader.PointerToRawData)
+            );
+        }
         WriteStructure(s, sectionHeader);
     }
 
+    private static void WriteStructure(Stream s, WebcilHeader webcilHeader)
+    {
+        if (!BitConverter.IsLittleEndian)
+        {
+            webcilHeader.version_major = BinaryPrimitives.ReverseEndianness(webcilHeader.version_major);
+            webcilHeader.version_minor = BinaryPrimitives.ReverseEndianness(webcilHeader.version_minor);
+            webcilHeader.coff_sections = BinaryPrimitives.ReverseEndianness(webcilHeader.coff_sections);
+            webcilHeader.pe_cli_header_rva = BinaryPrimitives.ReverseEndianness(webcilHeader.pe_cli_header_rva);
+            webcilHeader.pe_cli_header_size = BinaryPrimitives.ReverseEndianness(webcilHeader.pe_cli_header_size);
+            webcilHeader.pe_debug_rva = BinaryPrimitives.ReverseEndianness(webcilHeader.pe_debug_rva);
+            webcilHeader.pe_debug_size = BinaryPrimitives.ReverseEndianness(webcilHeader.pe_debug_size);
+        }
+        WriteStructure(s, webcilHeader);
+    }
+
 #if NETCOREAPP2_1_OR_GREATER
     private static void WriteStructure<T>(Stream s, T structure)
         where T : unmanaged
     {
-        // FIXME: fixup endianness
-        if (!BitConverter.IsLittleEndian)
-            throw new NotImplementedException();
         unsafe
         {
             byte* p = (byte*)&structure;
@@ -212,9 +232,6 @@ private static void WriteStructure<T>(Stream s, T structure)
     private static void WriteStructure<T>(Stream s, T structure)
         where T : unmanaged
     {
-        // FIXME: fixup endianness
-        if (!BitConverter.IsLittleEndian)
-            throw new NotImplementedException();
         int size = Marshal.SizeOf<T>();
         byte[] buffer = new byte[size];
         IntPtr ptr = IntPtr.Zero;

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs

@@ -6,7 +6,7 @@
 using System.IO;
 using System.Reflection;
 using System.Runtime.InteropServices;
-
+using System.Buffers.Binary;
 using System.Reflection.Metadata;
 using System.Reflection.PortableExecutable;
 
@@ -63,14 +63,20 @@ private unsafe bool ReadHeader()
         {
             return false;
         }
-        if (!BitConverter.IsLittleEndian)
-        {
-            throw new NotImplementedException("TODO: implement big endian support");
-        }
         fixed (byte* p = buffer)
         {
             header = *(WebcilHeader*)p;
         }
+        if (!BitConverter.IsLittleEndian)
+        {
+            header.version_major = BinaryPrimitives.ReverseEndianness(header.version_major);
+            header.version_minor = BinaryPrimitives.ReverseEndianness(header.version_minor);
+            header.coff_sections = BinaryPrimitives.ReverseEndianness(header.coff_sections);
+            header.pe_cli_header_rva = BinaryPrimitives.ReverseEndianness(header.pe_cli_header_rva);
+            header.pe_cli_header_size = BinaryPrimitives.ReverseEndianness(header.pe_cli_header_size);
+            header.pe_debug_rva = BinaryPrimitives.ReverseEndianness(header.pe_debug_rva);
+            header.pe_debug_rva = BinaryPrimitives.ReverseEndianness(header.pe_debug_size);
+        }
         if (header.id[0] != 'W' || header.id[1] != 'b'
             || header.id[2] != 'I' || header.id[3] != 'L'
             || header.version_major != Internal.Constants.WC_VERSION_MAJOR
@@ -346,6 +352,7 @@ private long TranslateRVA(uint rva)
 
     private unsafe ImmutableArray<WebcilSectionHeader> ReadSections()
     {
+        WebcilSectionHeader secheader;
         var sections = ImmutableArray.CreateBuilder<WebcilSectionHeader>(_header.coff_sections);
         var buffer = new byte[Marshal.SizeOf<WebcilSectionHeader>()];
         _stream.Seek(SectionDirectoryOffset + _webcilInWasmOffset, SeekOrigin.Begin);
@@ -357,8 +364,24 @@ private unsafe ImmutableArray<WebcilSectionHeader> ReadSections()
             }
             fixed (byte* p = buffer)
             {
-                // FIXME endianness
-                sections.Add(*(WebcilSectionHeader*)p);
+                secheader = (*(WebcilSectionHeader*)p);
+            }
+            if (!BitConverter.IsLittleEndian)
+            {
+                sections.Add
+                (
+                    new WebcilSectionHeader
+                    (
+                        virtualSize: BinaryPrimitives.ReverseEndianness(secheader.VirtualSize),
+                        virtualAddress: BinaryPrimitives.ReverseEndianness(secheader.VirtualAddress),
+                        sizeOfRawData: BinaryPrimitives.ReverseEndianness(secheader.SizeOfRawData),
+                        pointerToRawData: BinaryPrimitives.ReverseEndianness(secheader.PointerToRawData)
+                    )
+                );
+            }
+            else
+            {
+                sections.Add(secheader);
             }
         }
         return sections.MoveToImmutable();