[tools] Support current and legacy assembly stores

[simonrozsival]

Summary

• locate CoreCLR assembly stores through the exported _assembly_store ELF symbol while retaining the MonoVM payload section fallback
• preserve compatibility with legacy v1 multi-file store sets, manifests, and architecture-agnostic assemblies
• read both v2 and v3 RID-specific stores under their historical and current APK/AAB names
• decode both XALZ/LZ4 and XAZS/Zstd compressed assemblies
• use the unified reader from decompress-assemblies without dropping direct DLL or individual-entry handling

This follows up on #12033 (comment).

Compatibility

The reader now detects the archive layout, ELF wrapper, store format, and compression format independently:

Layer	Supported formats
Store set	legacy v1 blobs + manifest; RID-specific v2/v3 stores
APK/AAB entry	assemblies/assemblies.blob; libassemblies.{abi}.blob.so; libassembly-store.so
Wrapper	raw blob; ELF payload section; exported _assembly_store symbol
Compression	uncompressed; XALZ/LZ4; XAZS/Zstd

Legacy common assemblies are included in each ABI-specific view, matching the original store-set behavior.

Follow-up

A separate stacked PR will simplify the standalone tool projects into .NET file-based apps and introduce skills that invoke them for customer APK inspection and extraction. The shared compatibility parser remains in the repository because build/device tests and external projects consume or track it.

Validation

• 10 standalone compatibility tests covering:
  • v1 filesystem, manifest, base-name, APK, common-store, LZ4, and Zstd cases
  • v2 historical archive names and index layout
  • v3 current archive names and index layout
• builds for the modern reader, legacy reader, decompressor, and tmt
• compatibility tests added to Windows CI

[Copilot]

Pull request overview

This PR updates the inspection/decompression tooling to support the current CoreCLR assembly-store layout by locating the store via the exported _assembly_store ELF symbol (with a fallback to the legacy payload section), and wires that into decompress-assemblies so it can correctly extract assemblies from modern APK/AAB layouts under lib/{ABI}/libassembly-store.so. It also factors the v2 reader into a reusable library and ensures decompression failures propagate via the tool exit code.

Changes:

• Add ELF _assembly_store symbol lookup (with payload section fallback) to the mk2 assembly-store reader.
• Split the mk2 reader into a reusable AssemblyStore library and consume it from both the mk2 CLI and decompress-assemblies.
• Update decompress-assemblies to handle both legacy assemblies/assemblies.blob and current lib/{ABI}/libassembly-store.so stores, and to return non-zero on failures.

Show a summary per file

File	Description
tools/decompress-assemblies/main.cs	Adds support for extracting from current lib/{ABI}/libassembly-store.so stores (plus better failure propagation), while keeping legacy store and individual-entry paths.
tools/decompress-assemblies/decompress-assemblies.csproj	Adds a project reference (with alias) to the mk2 AssemblyStore library and the Android SDK tools dependency needed for ABI/arch handling.
tools/assembly-store-reader-mk2/Main.cs	Removes redundant file-format/existence checks now handled by AssemblyStoreExplorer.Open.
tools/assembly-store-reader-mk2/Directory.Build.targets	Copies the launch script only for executable builds and makes the script path resolution robust via $(MSBuildThisFileDirectory).
tools/assembly-store-reader-mk2/AssemblyStore/Utils.cs	Implements _assembly_store dynamic symbol-based payload discovery with fallback to payload section scanning.
tools/assembly-store-reader-mk2/AssemblyStore/StoreReader_V2.cs	Uses the new ELF payload discovery API and improves the error message for invalid _assembly_store symbols.
tools/assembly-store-reader-mk2/AssemblyStore/ELFPayloadError.cs	Adds an error value for invalid payload symbols.
tools/assembly-store-reader-mk2/AssemblyStore/AssemblyStoreItem.cs	Makes AssemblyStoreItem public to support external consumers.
tools/assembly-store-reader-mk2/AssemblyStore/AssemblyStoreExplorer.cs	Makes AssemblyStoreExplorer public and updates the “no entries found” error message.
tools/assembly-store-reader-mk2/AssemblyStore/AssemblyStore.csproj	Introduces a dedicated reusable library project for the mk2 reader implementation.
tools/assembly-store-reader-mk2/assembly-store-reader.csproj	Switches the CLI to consume the new library project instead of compiling the sources directly.

Copilot's findings

• Files reviewed: 11/11 changed files
• Comments generated: 0

[jonathanpeppers]

/review

[github-actions]

✅ Android PR Reviewer completed successfully!

[github-actions]

⚠️ Needs Changes

Nice, well-structured follow-up that revives decompress-assemblies for symbol-based (libassembly-store.so) stores while preserving the legacy assemblies.blob and individual-entry paths, plus threading failures through the exit code. The ELF _assembly_store symbol resolution with a payload-section fallback is clean, and the 32/64-bit bounds checks are careful.

Issues (see inline comments):

• ⚠️ 1 error-handling: GetAndroidAbi can throw NotSupportedException for None/Mips/Other archs (which pass the HasValue guard), crashing the tool instead of propagating a non-zero exit code — the opposite of one of this PR's goals.
• 💡 2 suggestions: arch→ABI mapping duplicates MonoAndroidHelper; and a diagnostic log for the zero-size symbol fallback.

Verification notes:

• CI is still pending on the head commit — not green yet, so not mergeable until checks pass.
• The retained FindELFPayloadSectionOffsetAndSize wrapper is correctly kept for its build-task/test caller (ArchiveAssemblyHelper.cs), which now transparently gains symbol-based resolution.
• Re: the PR's open question about deleting decompress-assemblies — that's a reasonable call for maintainers; nothing in this diff blocks either decision.

No blocking correctness issues beyond the unhandled-exception path above.

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