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[NativeAOT] Add cDAC data descriptor infrastructure - #127024
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Add the native cDAC data descriptor for NativeAOT, enabling diagnostic tools (cDAC reader, SOS) to inspect NativeAOT runtime state through the same contract-based mechanism used by CoreCLR. Includes: - datadescriptor.inc with Thread, ThreadStore, MethodTable, ExInfo, EEAllocContext, GCAllocContext, RuntimeInstance types and globals - CMake integration using shared clrdatadescriptors.cmake infrastructure - GC sub-descriptor for workstation and server GC - Contract declarations: Thread (1001), Exception (1), RuntimeTypeSystem (1001) - Symbol export via --export-dynamic-symbol in build targets Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
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Pull request overview
Adds NativeAOT-side cDAC data descriptor generation so diagnostic tools can inspect NativeAOT runtime state via the shared contract-descriptor mechanism (similar to CoreCLR), including build integration and symbol export.
Changes:
- Introduces a NativeAOT
datadescriptor.incdescribing key runtime types/globals and supported contracts (plus GC sub-descriptor hook). - Adds
cdac_data<T>friend-based offset exposure for NativeAOT runtime types (e.g.,MethodTable,ThreadStore,RuntimeInstance). - Integrates descriptor generation into NativeAOT CMake builds and exports the
DotNetRuntimeContractDescriptorsymbol from ILC output.
Reviewed changes
Copilot reviewed 9 out of 9 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| src/coreclr/nativeaot/Runtime/threadstore.h | Exposes ThreadStore offsets for descriptor generation via cdac_data<ThreadStore>. |
| src/coreclr/nativeaot/Runtime/inc/MethodTable.h | Exposes MethodTable field offsets + flag constants via cdac_data<MethodTable>. |
| src/coreclr/nativeaot/Runtime/datadescriptor/datadescriptor.inc | New NativeAOT data descriptor defining types/globals/contracts and GC sub-descriptor pointer. |
| src/coreclr/nativeaot/Runtime/datadescriptor/datadescriptor.h | New include aggregator to support offsetof() use in datadescriptor.inc. |
| src/coreclr/nativeaot/Runtime/datadescriptor/CMakeLists.txt | Adds CMake targets that generate contract descriptors and GC descriptors. |
| src/coreclr/nativeaot/Runtime/RuntimeInstance.h | Exposes RuntimeInstance offsets via cdac_data<RuntimeInstance>. |
| src/coreclr/nativeaot/Runtime/Full/CMakeLists.txt | Links the generated descriptor object libraries into Runtime.*GC. |
| src/coreclr/nativeaot/Runtime/CMakeLists.txt | Adds the new datadescriptor/ subdirectory to the NativeAOT runtime build. |
| src/coreclr/nativeaot/BuildIntegration/Microsoft.NETCore.Native.targets | Exports DotNetRuntimeContractDescriptor from produced binaries when debugger support is enabled. |
| CDAC_TYPE_FIELD(Thread, T_POINTER, ExceptionTracker, offsetof(RuntimeThreadLocals, m_pExInfoStackHead)) | ||
| CDAC_TYPE_FIELD(Thread, T_POINTER, CachedStackBase, offsetof(RuntimeThreadLocals, m_pStackHigh)) | ||
| CDAC_TYPE_FIELD(Thread, T_POINTER, CachedStackLimit, offsetof(RuntimeThreadLocals, m_pStackLow)) | ||
| CDAC_TYPE_FIELD(Thread, TYPE(RuntimeThreadLocals), RuntimeThreadLocals, offsetof(RuntimeThreadLocals, m_eeAllocContext)) |
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Thread.RuntimeThreadLocals is declared as TYPE(RuntimeThreadLocals) but the offset used is offsetof(RuntimeThreadLocals, m_eeAllocContext), which points into the middle of the RuntimeThreadLocals layout (the alloc context) rather than to the start of the RuntimeThreadLocals subobject. Since Thread is class Thread : private RuntimeThreadLocals, the runtime locals base is at offset 0; this field should be a pointer to that base (typically T_POINTER with offset 0, similar to CoreCLR), otherwise tools will interpret the wrong address as a RuntimeThreadLocals instance.
| CDAC_TYPE_FIELD(Thread, TYPE(RuntimeThreadLocals), RuntimeThreadLocals, offsetof(RuntimeThreadLocals, m_eeAllocContext)) | |
| CDAC_TYPE_FIELD(Thread, T_POINTER, RuntimeThreadLocals, 0) |
| template<> struct cdac_data<ThreadStore> | ||
| { | ||
| static constexpr size_t FirstThreadLink = offsetof(ThreadStore, m_ThreadList); | ||
| }; |
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cdac_data<ThreadStore>::FirstThreadLink is set to offsetof(ThreadStore, m_ThreadList), but m_ThreadList is an SList<Thread> object whose head pointer is the private SList::m_pHead. Using the address of the SList object as though it were the head link relies on m_pHead being at offset 0 (and on empty-base layout), which is a fragile ABI contract for diagnostics. Consider exposing the offset of m_ThreadList.m_pHead explicitly (e.g., by adding a cdac_data<SList<...>>/friend hook or an explicit Thread* head field) so the descriptor doesn't depend on SList layout details.
| add_library(nativeaot_descriptor_interface INTERFACE) | ||
| target_include_directories(nativeaot_descriptor_interface INTERFACE | ||
| ${CMAKE_CURRENT_SOURCE_DIR}) | ||
| add_dependencies(nativeaot_descriptor_interface Runtime.WorkstationGC) | ||
| generate_data_descriptors( | ||
| LIBRARY_NAME nativeaot_cdac_contract_descriptor | ||
| CONTRACT_NAME "DotNetRuntimeContractDescriptor" | ||
| INTERFACE_TARGET nativeaot_descriptor_interface | ||
| EXPORT_VISIBLE) |
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add_dependencies(... Runtime.WorkstationGC) is added in this subdirectory before Runtime.WorkstationGC is defined (it’s created in Runtime/Full/CMakeLists.txt, which is added after this subdir). This will fail CMake configure, and it also risks creating a circular dependency since Runtime.WorkstationGC links against the generated descriptor libraries. Drop these explicit dependencies (linking the descriptor targets into Runtime.*GC is sufficient), or move dependency wiring to a scope where Runtime.WorkstationGC already exists.
| ${GC_DESCRIPTOR_DIR} | ||
| ${GC_DIR}) | ||
| add_dependencies(nativeaot_gc_svr_descriptor_interface Runtime.WorkstationGC) | ||
| target_compile_definitions(nativeaot_gc_svr_descriptor_interface INTERFACE -DSERVER_GC) |
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target_compile_definitions(... INTERFACE -DSERVER_GC) passes a definition string that already includes -D. CMake will add -D itself, producing an invalid define on some generators (e.g., -D-DSERVER_GC). Use SERVER_GC (without the -D prefix).
| target_compile_definitions(nativeaot_gc_svr_descriptor_interface INTERFACE -DSERVER_GC) | |
| target_compile_definitions(nativeaot_gc_svr_descriptor_interface INTERFACE SERVER_GC) |
Note
This PR was created with assistance from GitHub Copilot.
Summary
Adds the native cDAC data descriptor infrastructure for NativeAOT, enabling diagnostic tools (cDAC reader, SOS) to inspect NativeAOT runtime state through the same contract-based mechanism used by CoreCLR.
This is the first PR in a stacked pair. The second PR (#126972 replacement) adds the managed type sub-descriptor on top.
Changes
Native data descriptor (
datadescriptor.inc)cdac_data<>friend patternBuild integration
clrdatadescriptors.cmakeinfrastructure--export-dynamic-symbolinMicrosoft.NETCore.Native.targets