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[wasm][coreclr] Implement webcil V1 support in WebcilConverter and readers #126709

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Merged
radekdoulik merged 1 commit into from
Apr 9, 2026
Merged

[wasm][coreclr] Implement webcil V1 support in WebcilConverter and readers #126709

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2 changes: 2 additions & 0 deletions src/coreclr/tools/Common/Wasm/Webcil.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -40,6 +40,8 @@ public struct WebcilHeader
public uint PeDebugRva;
public uint PeDebugSize;
// 28 bytes
public uint TableBase;
// 32 bytes
}

/// <summary>
Expand Down
21 changes: 18 additions & 3 deletions src/mono/mono/metadata/webcil-loader.c
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,8 @@

/* keep in sync with webcil-writer */
enum {
MONO_WEBCIL_VERSION_MAJOR = 0,
MONO_WEBCIL_VERSION_MAJOR_0 = 0,
MONO_WEBCIL_VERSION_MAJOR_1 = 1,
MONO_WEBCIL_VERSION_MINOR = 0,
};

Expand All @@ -36,6 +37,13 @@ typedef struct MonoWebcilHeader {
// 28 bytes
} MonoWebcilHeader;

// Version 1 adds a TableBase field after the V0 header
typedef struct MonoWebcilHeader_1 {
MonoWebcilHeader base;
uint32_t table_base;
// 32 bytes
} MonoWebcilHeader_1;

static gboolean
find_webcil_in_wasm (const uint8_t *ptr, const uint8_t *boundp, const uint8_t **webcil_payload_start);

Expand Down Expand Up @@ -84,7 +92,8 @@ do_load_header (const char *raw_data, uint32_t raw_data_len, int32_t offset, Mon
memcpy (&wcheader, raw_data + offset, sizeof (wcheader));

if (!(wcheader.id [0] == 'W' && wcheader.id [1] == 'b' && wcheader.id[2] == 'I' && wcheader.id[3] == 'L' &&
GUINT16_FROM_LE (wcheader.version_major) == MONO_WEBCIL_VERSION_MAJOR && GUINT16_FROM_LE (wcheader.version_minor) == MONO_WEBCIL_VERSION_MINOR))
(GUINT16_FROM_LE (wcheader.version_major) == MONO_WEBCIL_VERSION_MAJOR_0 || GUINT16_FROM_LE (wcheader.version_major) == MONO_WEBCIL_VERSION_MAJOR_1) &&
GUINT16_FROM_LE (wcheader.version_minor) == MONO_WEBCIL_VERSION_MINOR))
return -1;

memset (header, 0, sizeof(MonoDotNetHeader));
Expand All @@ -94,7 +103,13 @@ do_load_header (const char *raw_data, uint32_t raw_data_len, int32_t offset, Mon
header->datadir.pe_debug.rva = GUINT32_FROM_LE (wcheader.pe_debug_rva);
header->datadir.pe_debug.size = GUINT32_FROM_LE (wcheader.pe_debug_size);

offset += sizeof (wcheader);
// V1 header is larger (32 bytes vs 28)
if (GUINT16_FROM_LE (wcheader.version_major) >= MONO_WEBCIL_VERSION_MAJOR_1) {
if (offset + sizeof (MonoWebcilHeader_1) > raw_data_len)
return -1;
offset += sizeof (MonoWebcilHeader_1);
} else
offset += sizeof (wcheader);
return offset;
}

Expand Down
63 changes: 55 additions & 8 deletions src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilConverter.cs
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Expand Up @@ -39,22 +39,28 @@ FilePosition SectionStart
);

private const int SectionAlignment = 16;
private const int V0HeaderSize = 28;
private const int V1HeaderSize = 32;

private readonly string _inputPath;
private readonly string _outputPath;
private readonly int _webcilVersion;

private string InputPath => _inputPath;

public bool WrapInWebAssembly { get; set; } = true;

private WebcilConverter(string inputPath, string outputPath)
private WebcilConverter(string inputPath, string outputPath, int webcilVersion)
{
if (webcilVersion != 0 && webcilVersion != 1)
throw new ArgumentOutOfRangeException(nameof(webcilVersion), webcilVersion, "Only webcil version 0 and 1 are supported");
_inputPath = inputPath;
_outputPath = outputPath;
_webcilVersion = webcilVersion;
}

public static WebcilConverter FromPortableExecutable(string inputPath, string outputPath)
=> new WebcilConverter(inputPath, outputPath);
public static WebcilConverter FromPortableExecutable(string inputPath, string outputPath, int webcilVersion = 0)
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=> new WebcilConverter(inputPath, outputPath, webcilVersion);

public void ConvertToWebcil()
{
Expand Down Expand Up @@ -104,9 +110,9 @@ public record struct FilePosition(int Position)
public static FilePosition operator +(FilePosition left, int right) => new(left.Position + right);
}

private static unsafe int SizeOfHeader()
private int SizeOfHeader()
{
return sizeof(WebcilHeader);
return _webcilVersion >= 1 ? V1HeaderSize : V0HeaderSize;
}

public unsafe void GatherInfo(PEReader peReader, out WCFileInfo wcInfo, out PEFileInfo peInfo)
Expand All @@ -117,14 +123,18 @@ public unsafe void GatherInfo(PEReader peReader, out WCFileInfo wcInfo, out PEFi
var sections = headers.SectionHeaders;
WebcilHeader header = default;
header.Id = WebcilConstants.WEBCIL_MAGIC;
header.VersionMajor = WebcilConstants.WC_VERSION_MAJOR;
header.VersionMajor = (ushort)_webcilVersion;
header.VersionMinor = WebcilConstants.WC_VERSION_MINOR;
header.CoffSections = (ushort)coffHeader.NumberOfSections;
header.Reserved0 = 0;
header.PeCliHeaderRva = (uint)peHeader.CorHeaderTableDirectory.RelativeVirtualAddress;
header.PeCliHeaderSize = (uint)peHeader.CorHeaderTableDirectory.Size;
header.PeDebugRva = (uint)peHeader.DebugTableDirectory.RelativeVirtualAddress;
header.PeDebugSize = (uint)peHeader.DebugTableDirectory.Size;
if (_webcilVersion >= 1)
{
header.TableBase = uint.MaxValue;
}

// current logical position in the output file
FilePosition pos = SizeOfHeader();
Expand Down Expand Up @@ -174,7 +184,7 @@ public unsafe void GatherInfo(PEReader peReader, out WCFileInfo wcInfo, out PEFi
SectionStart: firstWCSection);
}

private static void WriteHeader(Stream s, WebcilHeader webcilHeader)
private void WriteHeader(Stream s, WebcilHeader webcilHeader)
{
if (!BitConverter.IsLittleEndian)
{
Expand All @@ -186,8 +196,12 @@ private static void WriteHeader(Stream s, WebcilHeader webcilHeader)
webcilHeader.PeCliHeaderSize = BinaryPrimitives.ReverseEndianness(webcilHeader.PeCliHeaderSize);
webcilHeader.PeDebugRva = BinaryPrimitives.ReverseEndianness(webcilHeader.PeDebugRva);
webcilHeader.PeDebugSize = BinaryPrimitives.ReverseEndianness(webcilHeader.PeDebugSize);
if (_webcilVersion >= 1)
{
webcilHeader.TableBase = BinaryPrimitives.ReverseEndianness(webcilHeader.TableBase);
}
}
WriteStructure(s, webcilHeader);
WriteStructure(s, webcilHeader, SizeOfHeader());
}

private static void WriteSectionHeaders(Stream s, ImmutableArray<WebcilSectionHeader> sectionsHeaders)
Expand Down Expand Up @@ -223,6 +237,18 @@ private static void WriteStructure<T>(Stream s, T structure)
s.Write(new ReadOnlySpan<byte>(p, sizeof(T)));
}
}

private static void WriteStructure<T>(Stream s, T structure, int size)
where T : unmanaged
{
unsafe
{
if (size > sizeof(T))
throw new ArgumentOutOfRangeException(nameof(size), size, $"size exceeds struct size {sizeof(T)}");
byte* p = (byte*)&structure;
s.Write(new ReadOnlySpan<byte>(p, size));
}
}
#else
private static void WriteStructure<T>(Stream s, T structure)
where T : unmanaged
Expand All @@ -242,6 +268,27 @@ private static void WriteStructure<T>(Stream s, T structure)
}
s.Write(buffer, 0, size);
}

private static void WriteStructure<T>(Stream s, T structure, int size)
where T : unmanaged
{
int fullSize = Marshal.SizeOf<T>();
if (size > fullSize)
throw new ArgumentOutOfRangeException(nameof(size), size, $"size exceeds struct size {fullSize}");
byte[] buffer = new byte[fullSize];
IntPtr ptr = IntPtr.Zero;
try
{
ptr = Marshal.AllocHGlobal(fullSize);
Marshal.StructureToPtr(structure, ptr, false);
Marshal.Copy(ptr, buffer, 0, fullSize);
}
finally
{
Marshal.FreeHGlobal(ptr);
}
s.Write(buffer, 0, size);
}
#endif

private static void CopySections(Stream outStream, FileStream inputStream, ImmutableArray<SectionHeader> peSections, ImmutableArray<WebcilSectionHeader> wcSections)
Expand Down
37 changes: 32 additions & 5 deletions src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -55,17 +55,23 @@ public WebcilReader (Stream stream, string inputPath) : this(stream)
InputPath = inputPath;
}

// V0 header is 28 bytes, V1 adds a 4-byte TableBase field (32 bytes total)
private const int V0HeaderSize = 28;
private const int V1HeaderSize = 32;

private unsafe bool ReadHeader()
{
WebcilHeader header;
var buffer = new byte[Marshal.SizeOf<WebcilHeader>()];
// Read the V0 portion of the header first (28 bytes)
WebcilHeader header = default;
var buffer = new byte[V0HeaderSize];
if (_stream.Read(buffer, 0, buffer.Length) != buffer.Length)
{
return false;
}
fixed (byte* p = buffer)
{
header = *(WebcilHeader*)p;
// Copy V0 fields only (28 bytes) into the 32-byte struct
Buffer.MemoryCopy(p, &header, Marshal.SizeOf<WebcilHeader>(), V0HeaderSize);
}
if (!BitConverter.IsLittleEndian)
{
Expand All @@ -79,11 +85,29 @@ private unsafe bool ReadHeader()
header.PeDebugSize = BinaryPrimitives.ReverseEndianness(header.PeDebugSize);
}
if (header.Id != WebcilConstants.WEBCIL_MAGIC
|| header.VersionMajor != WebcilConstants.WC_VERSION_MAJOR
|| (header.VersionMajor != 0 && header.VersionMajor != 1)
|| header.VersionMinor != WebcilConstants.WC_VERSION_MINOR)
{
return false;
}
if (header.VersionMajor >= 1)
{
// V1 has an additional TableBase field
var extra = new byte[V1HeaderSize - V0HeaderSize];
if (_stream.Read(extra, 0, extra.Length) != extra.Length)
{
return false;
}
header.TableBase = BitConverter.ToUInt32(extra, 0);
if (!BitConverter.IsLittleEndian)
{
header.TableBase = BinaryPrimitives.ReverseEndianness(header.TableBase);
}
}
else
{
header.TableBase = uint.MaxValue;
}
_header = header;
return true;
}
Expand Down Expand Up @@ -353,7 +377,10 @@ private long TranslateRVA(uint rva)
throw new BadImageFormatException("RVA not found in any section", nameof(_stream));
}

private static long SectionDirectoryOffset => Marshal.SizeOf<WebcilHeader>();
// V0 header is 28 bytes (no TableBase), V1 is 32 bytes
private long SectionDirectoryOffset => _header.VersionMajor >= 1
? V1HeaderSize
: V0HeaderSize;

private unsafe ImmutableArray<WebcilSectionHeader> ReadSections()
{
Expand Down
4 changes: 2 additions & 2 deletions src/tasks/WasmAppBuilder/WebcilConverter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -31,9 +31,9 @@ private WebcilConverter(NET.WebAssembly.Webcil.WebcilConverter converter, string
Log = logger;
}

public static WebcilConverter FromPortableExecutable(string inputPath, string outputPath, LogAdapter logger)
public static WebcilConverter FromPortableExecutable(string inputPath, string outputPath, LogAdapter logger, int webcilVersion = 0)
{
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var converter = NET.WebAssembly.Webcil.WebcilConverter.FromPortableExecutable(inputPath, outputPath);
var converter = NET.WebAssembly.Webcil.WebcilConverter.FromPortableExecutable(inputPath, outputPath, webcilVersion);
return new WebcilConverter(converter, inputPath, outputPath, logger);
}

Expand Down
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