[browser][coreCLR] Loading WebCIL - 2nd attempt

[pavelsavara]

Enable Webcil loading in CoreCLR for Browser/WASM

Summary

Adds native Webcil container format support to the CoreCLR runtime, enabling CoreCLR-on-WASM to load .wasm-wrapped assemblies directly — previously only supported by the Mono runtime. Removes the WasmEnableWebcil=false override that was forcing CoreCLR browser builds to use raw .dll files.

Changes

CoreCLR Webcil decoder (src/coreclr/)

• New WebcilDecoder class (webcildecoder.h, webcildecoder.cpp) — standalone reader for the Webcil container format with full RVA/offset translation, COR header resolution, metadata access, section validation, IL method checking, debug directory support, and DAC enumeration.
• FEATURE_WEBCIL cmake gate enabled for CLR_CMAKE_TARGET_BROWSER (clrfeatures.cmake, clrdefinitions.cmake).

PEImageLayout composition refactor (src/coreclr/vm/)

• PEImageLayout no longer inherits from PEDecoder; instead holds m_peDecoder (and conditionally m_webcilDecoder) as members with an ImageFormat discriminator (FORMAT_PE/FORMAT_WEBCIL).
• ~160 inline forwarding methods in peimagelayout.inl dispatch to the active decoder via DECODER_DISPATCH/DECODER_CHECK/PE_OR_WEBCIL macros.
• PEDecoder public API split: methods needed by PEImageLayout forwarding stay public; PE-internal helpers (GetHeaders, GetDirectoryEntry, CheckDirectoryEntry, relocation/TLS/strong-name internals, etc.) moved to a private section accessible only via friend class PEImageLayout.
• FlatImageLayout constructor detects Webcil magic and initializes both decoders (Webcil for format operations, PE decoder for base/size/flags used by cDAC).
• New HasHeaders() abstraction on PEImageLayout and PEImage — returns HasWebcilHeaders() or HasNTHeaders() depending on format. Callers in peassembly.cpp, peimage.cpp, eventtrace.cpp updated from HasNTHeaders() to HasHeaders().
• debugdebugger.cpp: switched from PEDecoder* to PEImageLayout* and uses format-agnostic GetDirectoryEntryData instead of raw GetDirectoryEntry+GetDirectoryData.
• ceeload.cpp: same PEDecoder* → PEImageLayout* fix for IJW host lookup.
• peassembly.cpp: accept IMAGE_FILE_MACHINE_UNKNOWN (Webcil machine type) for IL-only validation; guard 32-bit NT header check with HasNTHeaders().
• assemblybindercommon.cpp: treat IMAGE_FILE_MACHINE_UNKNOWN as processor-agnostic MSIL.

cDAC diagnostics (src/native/managed/cdac/)

• PEImageLayout data descriptor gains Format field (datadescriptor.inc, PEImageLayout.cs).
• Loader_1.cs: Webcil-aware RvaToOffset path that reads the Webcil section table directly from the target memory when IsWebcilFormat is set.

Build/infrastructure

• Removed WasmEnableWebcil=false from CoreCLR browser build properties (WasmApp.InTree.props, tests.browser.targets).
• MSBuild task renames: WebCilCandidates→WebcilCandidates, IsWebCilEnabled→IsWebcilEnabled, _WasmBuildWebCilPath→_WasmBuildWebcilPath and related properties.
• Test infrastructure: BuildEnvironment.cs removes CoreCLR Webcil exclusion; env var WasmEnableWebCil→WasmEnableWebcil.

[dotnet-policy-service]

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[Copilot]

Pull request overview

Enables CoreCLR-on-Browser/WASM to load assemblies packaged in the Webcil container format (i.e., .wasm-wrapped assemblies), aligning CoreCLR behavior with existing Mono Webcil support and removing prior build/test overrides that forced raw .dll usage.

Changes:

• Adds CoreCLR-side Webcil decoding and wires it into PEImageLayout via format-dispatched forwarding to either PEDecoder (PE) or WebcilDecoder (Webcil).
• Updates the Webcil tooling pipeline (converter/reader/wrapper + MSBuild tasks/targets) including 16-byte section alignment and property renames (WebCil* → Webcil*).
• Extends cDAC contracts/readers and WASM test infrastructure to understand and exercise Webcil images.

Reviewed changes

Copilot reviewed 35 out of 35 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilWasmWrapper.cs	Improves wrapper error message for payload offset validation.
src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs	Updates to PascalCase header fields and adds bounds checking in RVA translation.
src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilHeader.cs	Renames Webcil header fields to PascalCase for consistency.
src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilConverter.cs	Implements 16-byte section alignment, debug directory translation, and related validations.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ConvertDllsToWebCil.cs	Renames output item list to WebcilCandidates.
src/tasks/Microsoft.NET.Sdk.WebAssembly.Pack.Tasks/ComputeWasmPublishAssets.cs	Renames task property to IsWebcilEnabled and updates usage.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/PEImageLayout.cs	Adds Format field to contract + helper to detect Webcil format.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs	Adds Webcil-aware RVA-to-offset logic by reading Webcil section table from target memory.
src/mono/wasm/features.md	Documentation update: “WebCIL” → “Webcil”.
src/mono/wasm/Wasm.Build.Tests/Common/BuildEnvironment.cs	Removes CoreCLR Webcil exclusion; renames env var WasmEnableWebcil.
src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.targets	Renames MSBuild properties/items/parameters from WebCil → Webcil.
src/mono/cmake/options.cmake	Documentation string update for ENABLE_WEBCIL.
src/mono/cmake/config.h.in	Comment update for ENABLE_WEBCIL.
src/mono/browser/debugger/BrowserDebugProxy/DebugStore.cs	Documentation wording update for Webcil handling.
src/mono/browser/build/WasmApp.InTree.props	Removes CoreCLR WasmEnableWebcil=false override.
src/coreclr/vm/peimagelayout.inl	Adds decoder-dispatch forwarding methods; introduces format-agnostic header checks.
src/coreclr/vm/peimagelayout.h	Refactors PEImageLayout to composition with PEDecoder/WebcilDecoder and ImageFormat discriminator.
src/coreclr/vm/peimagelayout.cpp	Initializes Webcil decoder on detection; updates PEDecoder init/reset call sites; DAC enumeration dispatch.
src/coreclr/vm/peimage.inl	Adds PEImage::HasHeaders() helper.
src/coreclr/vm/peimage.h	Declares HasHeaders() in PEImage.
src/coreclr/vm/peimage.cpp	Uses HasHeaders() instead of HasNTHeaders() in metadata/debug-directory paths.
src/coreclr/vm/peassembly.cpp	Accepts IMAGE_FILE_MACHINE_UNKNOWN for IL-only validation; guards 32-bit header check.
src/coreclr/vm/eventtrace.cpp	Switches checks from NT headers to format-agnostic headers.
src/coreclr/vm/debugdebugger.cpp	Switches from PEDecoder* to PEImageLayout* and uses GetDirectoryEntryData.
src/coreclr/vm/datadescriptor/datadescriptor.inc	Adds Format field to PEImageLayout’s cDAC data descriptor.
src/coreclr/vm/ceeload.cpp	Updates IJW lookup to use PEImageLayout* (post-inheritance refactor).
src/coreclr/utilcode/webcildecoder.cpp	Adds CoreCLR Webcil decoding/validation implementation and DAC enumeration support.
src/coreclr/utilcode/CMakeLists.txt	Adds webcildecoder.cpp to utilcode build.
src/coreclr/inc/webcildecoder.h	Adds Webcil structures and WebcilDecoder API.
src/coreclr/inc/pedecoder.h	Makes PEImageLayout a friend and restricts PE-internal APIs to PEImageLayout usage.
src/coreclr/clrfeatures.cmake	Enables FEATURE_WEBCIL for browser builds.
src/coreclr/clrdefinitions.cmake	Adds FEATURE_WEBCIL compile definition when enabled.
src/coreclr/binder/assemblybindercommon.cpp	Treats IMAGE_FILE_MACHINE_UNKNOWN as processor-agnostic MSIL in binder logic.
eng/testing/tests.browser.targets	Removes CoreCLR WasmEnableWebcil=false override for browser tests.
docs/design/mono/webcil.md	Updates spec text for alignment and PascalCase field names + naming consistency.

[Copilot]

Pull request overview

Copilot reviewed 35 out of 35 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (1)

src/tasks/Microsoft.NET.WebAssembly.Webcil/WebcilReader.cs:354

• New exceptions in TranslateRVA use nameof(_stream) as the parameter name. Since _stream is a private field (not a parameter), this produces a less helpful ParamName than nameof(stream) (constructor parameter) or omitting the param name entirely. Consider aligning with the earlier constructor exceptions which use nameof(stream).

[Copilot]

Pull request overview

Copilot reviewed 35 out of 35 changed files in this pull request and generated 2 comments.

[Copilot]

Pull request overview

Copilot reviewed 23 out of 23 changed files in this pull request and generated 5 comments.

[Copilot]

Pull request overview

Copilot reviewed 23 out of 23 changed files in this pull request and generated 1 comment.

[jkotas]

IL-only files have machine type IMAGE_FILE_MACHINE_I386 for historic reasons. I think it would make more sense to return it here so that we do not need to fix all callers.

[jkotas]

CorHeader is stored in webcil header as well, but this method does not return it.

It may be better to have concrete HasDebugDirectoryEntry / GetDebugDirectoryEntry methods and make the generic one unimplemented for webcil.

[jkotas]

This is duplicating a lot of non-trivial logic. Any way we can avoid it?