Add ISOSDacInterface17 for StressLog enumeration via cDAC by max-charlamb · Pull Request #129272 · dotnet/runtime

max-charlamb · 2026-06-11T02:29:19Z

Note

This PR was created with assistance from GitHub Copilot.

Summary

Add a new ISOSDacInterface17 COM interface that exposes the cDAC's IStressLog contract to SOS and clrmd consumers. This enables reading stress logs from both CoreCLR and NativeAOT processes without hardcoded struct offsets.

Motivation

SOS (!DumpLog) and clrmd currently read stress logs via raw memory reads with hardcoded struct offsets matching the CoreCLR layout. NativeAOT's StressLog struct has a different layout (different lock type, no module table, no padding sentinel), so these tools cannot read NativeAOT stress logs.

The cDAC already has a working IStressLog contract (StressLog_1/StressLog_2) that reads stress logs from both runtimes using datadescriptor.inc field offsets. This PR bridges that contract to the COM interface layer so SOS and clrmd can consume it.

Changes

cDAC contract updates

Add StartTime (wall-clock FILETIME) to data descriptors (CoreCLR + NativeAOT), Data/StressLog.cs, StressLogData record, and contract implementation
Add Address field to ThreadStressLogData for thread identification across the COM boundary
Add StressLog to ContractRegistry

ISOSDacInterface17 definition

Data structs: SOSStressLogData, SOSThreadStressLogData, SOSStressMsgData (defined inline in IDL following modern convention)
Enumerator interfaces: ISOSStressLogThreadEnum, ISOSStressLogMsgEnum
ISOSDacInterface17: GetStressLogData, GetStressLogThreadEnumerator, GetStressLogMessageEnumerator
All APIs return S_FALSE when stress log is not enabled (no separate availability check needed)

SOSDacImpl bridge

Thread enumerator: materialized array with try/catch COM boundary protection
Message enumerator: eagerly materialized with full Reset/GetCount support and GetArguments for per-batch arg retrieval
The native DAC does not implement this interface -- QueryInterface for the IID will fail on the legacy DAC, and only the cDAC handles it

IDL + testing

Full IDL definitions in sospriv.idl
StressLog debuggee + dump-based integration tests validating the contract and the COM interface layer

Test Results

All dump tests pass:

StressLogIsAvailable -- PASSED
StressLogDataIsValid -- PASSED
CanEnumerateThreadsAndMessages -- PASSED

Related PRs

Diagnostics: Use ISOSDacInterface17 for DumpLog when available diagnostics#5873 -- SOS !DumpLog updated to use ISOSDacInterface17 with fallback
CI run: runtime-diagnostics build 1458939

Add a new ISOSDacInterface17 COM interface that exposes the cDAC's IStressLog contract to SOS and clrmd consumers. This enables reading stress logs from both CoreCLR and NativeAOT without hardcoded struct offsets. Changes: - Add StartTime (wall-clock FILETIME) field to cDAC data descriptors, Data/StressLog.cs, StressLogData record, and contract implementation - Add StressLog to ContractRegistry - Add Address field to ThreadStressLogData for thread identification - Define ISOSDacInterface17 with IsStressLogAvailable, GetStressLogData, GetStressLogThreadEnumerator, GetStressLogMessageEnumerator, and GetStressLogMemoryRanges - Define ISOSStressLogThreadEnum, ISOSStressLogMsgEnum, and ISOSStressLogMemoryEnum enumerator interfaces - Implement SOSDacImpl bridge delegating to _target.Contracts.StressLog - Add IDL definitions in sospriv.idl (native DAC does not implement this interface; QueryInterface for the IID will fail on the legacy DAC) - Add StressLog debuggee and StressLogDumpTests for dump-based validation - Add design document explaining the architecture and migration path Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR extends the cDAC stress log support by (1) enriching the StressLog contract data model (notably adding StartTime and thread-log address identity) and (2) introducing a new ISOSDacInterface17 COM surface (IDL + managed declarations + SOSDacImpl bridge) intended to let SOS/clrmd enumerate stress logs without hardcoded layout offsets. It also adds a new dump-test debuggee plus contract-level dump tests and a detailed design document.

Changes:

Add StartTime to StressLog data descriptors (CoreCLR + NativeAOT) and flow it through the managed contract types.
Add ISOSDacInterface17 + related StressLog enumerator interfaces/structs and implement the bridge in SOSDacImpl.
Add StressLog dump debuggee and dump-based integration tests for the StressLog contract, plus a design doc.

Reviewed changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 8 comments.

Show a summary per file

File	Description
src/native/managed/cdac/tests/DumpTests/StressLogDumpTests.cs	Adds dump-based integration tests for the StressLog contract (availability, header data, basic enumeration).
src/native/managed/cdac/tests/DumpTests/Debuggees/StressLog/StressLog.csproj	New debuggee project enabling stress logging via environment variables.
src/native/managed/cdac/tests/DumpTests/Debuggees/StressLog/Program.cs	New debuggee that generates allocations/GC activity then `FailFast`s to produce a dump.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs	Implements `ISOSDacInterface17` and new StressLog enumerator implementations bridging to the cDAC `IStressLog` contract.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ISOSDacInterface.cs	Adds public COM interface/struct declarations for `ISOSDacInterface17` and StressLog enumerators.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/StressLog.cs	Adds `[Field] StartTime` to the StressLog data model.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StressLog.cs	Plumbs `StartTime` into `StressLogData` and includes thread-log address in `ThreadStressLogData`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IStressLog.cs	Extends `StressLogData` with `StartTime` and `ThreadStressLogData` with `Address`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/ContractRegistry.cs	Exposes `StressLog` via `Target.Contracts.StressLog`.
src/coreclr/vm/datadescriptor/datadescriptor.inc	Exports `StressLog.StartTime` for CoreCLR via data descriptors.
src/coreclr/nativeaot/Runtime/datadescriptor/datadescriptor.inc	Exports `StressLog.StartTime` for NativeAOT via data descriptors.
src/coreclr/inc/sospriv.idl	Adds IDL definitions for `ISOSDacInterface17` and associated StressLog structs/enumerator interfaces.
docs/design/datacontracts/stresslog-isosinterface-design.md	Design rationale and planned consumer migration strategy for exposing StressLog via SOS DAC interface.

jkotas · 2026-06-11T03:26:18Z

Is there a specific reason that regular CoreCLR and NativeAOT stress logs must be different?

- Add [GeneratedComClass] to all three enumerator classes - Use ToTargetPointer for ClrDataAddress comparison - Shrink _lastBatchRaw to actual fetched size - Return ex.HResult instead of E_FAIL in IsStressLogAvailable Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 5 comments.

jkotas · 2026-06-11T22:09:43Z

We should be able to delete https://github.com/max-charlamb/runtime/blob/bd3de83c6195bdbda612e67672fb1248a1014d28/src/coreclr/inc/stresslog.h#L225 once this is in place. (It does not have to be done in this PR.)

- Remove DacpStressLogMemoryRange, ISOSStressLogMemoryEnum, and GetStressLogMemoryRanges from IDL, managed interface, and impl since no SOS consumer uses them. - Refactor SOSStressLogMsgEnum to eagerly materialize messages into an array, enabling Reset and GetCount support consistent with other ISOSEnum implementations. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Rename DacpStressLogData -> SOSStressLogData, DacpThreadStressLogData -> SOSThreadStressLogData, DacpStressMsgData -> SOSStressMsgData - Define structs inline in sospriv.idl with typedef struct and cpp_quote guards, following the SOSMethodData/SOSMemoryRegion convention used by newer interfaces - Remove Dacp forward declarations and dacprivate.h definitions - Put ISOSDacInterface16, ISOSDacInterface17 on same line in class decl Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Use 'written < count' pattern for S_FALSE (standard COM IEnumXxx convention matching SOSMethodEnum/SOSMemoryEnum) - Return E_POINTER directly for null output in GetStressLogData Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

StressMsgHeaderSize, ChunkSize, MaxMessageSize, and PointerSize are implementation details for raw memory walking that the message enumerator now abstracts away. Consumers no longer need them. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Callers can just call GetStressLogData/GetStressLogThreadEnumerator directly -- they return S_FALSE when stress log is not enabled. No need for a separate availability check method. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (1)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IStressLog.cs:28

StressLogData and ThreadStressLogData are public record structs. Adding new positional parameters (StartTime, Address) changes the synthesized primary constructor and Deconstruct, which is source/binary breaking for any consumers. If this assembly has any external consumers, consider keeping the existing primary constructor stable and adding the new data as additional properties (or introducing new types) instead.

public record struct StressLogData(
    uint LoggedFacilities,
    uint Level,
    uint MaxSizePerThread,
    uint MaxSizeTotal,
    int TotalChunks,
    ulong TickFrequency,
    ulong StartTimestamp,
    ulong StartTime,
    TargetPointer Logs);

public record struct ThreadStressLogData(
    TargetPointer Address,
    TargetPointer NextPointer,
    ulong ThreadId,
    bool WriteHasWrapped,
    TargetPointer CurrentPointer,
    TargetPointer ChunkListHead,
    TargetPointer ChunkListTail,
    TargetPointer CurrentWriteChunk);

- Initialize *data = default early in GetStressLogData for clean output on all failure paths - Wrap enumerator Next methods in try/catch to avoid leaking exceptions across the COM boundary - Add ISOSDacInterface17 dump tests exercising GetStressLogData, GetStressLogThreadEnumerator, GetStressLogMessageEnumerator, and GetArguments through the SOSDacImpl COM bridge Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 4 comments.

Comments suppressed due to low confidence (1)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IStressLog.cs:28

StressLogData and ThreadStressLogData are public positional record structs. Adding new parameters (StartTime, Address) is a source+binary breaking change for any downstream consumers (constructor signature + synthesized members change). If these are consumed outside the repo, consider versioning the contract shape (e.g., new record types or additive properties) rather than changing existing positional parameters, or ensure the package versioning/compat story accounts for this break.

public record struct StressLogData(
    uint LoggedFacilities,
    uint Level,
    uint MaxSizePerThread,
    uint MaxSizeTotal,
    int TotalChunks,
    ulong TickFrequency,
    ulong StartTimestamp,
    ulong StartTime,
    TargetPointer Logs);

public record struct ThreadStressLogData(
    TargetPointer Address,
    TargetPointer NextPointer,
    ulong ThreadId,
    bool WriteHasWrapped,
    TargetPointer CurrentPointer,
    TargetPointer ChunkListHead,
    TargetPointer ChunkListTail,
    TargetPointer CurrentWriteChunk);

+        int ISOSEnum.Reset()
+        {
+            _index = 0;
+            return HResults.S_OK;
+        }


+        uint threadCount;
+        ppThreadEnum.Interface!.GetCount(&threadCount);
+
+        SOSThreadStressLogData[] threads = new SOSThreadStressLogData[threadCount];
+        uint fetched;
+        ppThreadEnum.Interface!.Next(threadCount, threads, &fetched);


CoreCLR datadescriptor.inc declared TotalChunks as T_UINT32 but the actual C++ field is Volatile<LONG> (signed int32). NativeAOT already had the correct T_INT32. Fix CoreCLR to match. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 6 comments.

+            Contracts.IStressLog stressLogContract = _target.Contracts.StressLog;
+            if (!stressLogContract.HasStressLog())
+                return HResults.S_FALSE;


+            Contracts.IStressLog stressLogContract = _target.Contracts.StressLog;
+            if (!stressLogContract.HasStressLog())
+                return HResults.S_FALSE;


+        uint threadCount;
+        threadEnum.GetCount(&threadCount);
+
+        SOSThreadStressLogData[] threads = new SOSThreadStressLogData[threadCount];
+        uint fetched;
+        threadEnum.Next(threadCount, threads, &fetched);
+


- SOSStressLogMsgEnum.Reset() now clears _lastBatchStart and _lastBatchCount to prevent stale GetArguments after Reset - Assert HRESULT return values from GetCount/Next in the message enumerator test for actionable failure messages Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

noahfalk · 2026-06-17T21:23:58Z

+    unsigned int Level;
+    unsigned int MaxSizePerThread;
+    unsigned int MaxSizeTotal;
+    int TotalChunks;


Does SOS need fields like 'TotalChunks' or 'Logs'? Those seem like internal implementation details of the data structure and not info we'd need to include in the interface.

Removed everything that isn't used by the SOS implementation: dotnet/diagnostics#5873

Logs is not used, but TotalChunks is used to print data in the !dumplog header.

noahfalk · 2026-06-17T21:25:13Z

+    CLRDATA_ADDRESS CurrentPointer;
+    CLRDATA_ADDRESS ChunkListHead;
+    CLRDATA_ADDRESS ChunkListTail;
+    CLRDATA_ADDRESS CurrentWriteChunk;


Other than ThreadId, does SOS need anything else in this structure? It looks like implementation details of the data structure that SOS wouldn't need to know. If we need something to act as an opaque identifier when refering to a specific ThreadStressLog the address field also seems fine.

noahfalk · 2026-06-17T21:31:02Z

+    CLRDATA_ADDRESS FormatString;
+    UINT64 Timestamp;
+    unsigned int ArgumentCount;
+    CLRDATA_ADDRESS MessageAddress;


Do we need this MessageAddress field in the interface for something?

Remove fields not consumed by the SOS DumpLog PR: - SOSStressLogData: Logs (callers use enumerator, not raw pointer) - SOSThreadStressLogData: WriteHasWrapped, CurrentPointer, ChunkListHead, ChunkListTail, CurrentWriteChunk (raw chunk-walking details abstracted by the message enumerator) - SOSStressMsgData: MessageAddress (was always 0) Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 6 comments.

Comments suppressed due to low confidence (1)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IStressLog.cs:28

These are public positional record structs. Adding new positional parameters (StartTime / Address) is a breaking change for any consumer that constructs, deconstructs, or pattern-matches these records. If this API is intended to be compatible across versions, consider keeping the existing primary constructor shape and adding new members as additional properties (e.g., public ulong StartTime { get; init; }) instead.

public record struct StressLogData(
    uint LoggedFacilities,
    uint Level,
    uint MaxSizePerThread,
    uint MaxSizeTotal,
    int TotalChunks,
    ulong TickFrequency,
    ulong StartTimestamp,
    ulong StartTime,
    TargetPointer Logs);

public record struct ThreadStressLogData(
    TargetPointer Address,
    TargetPointer NextPointer,
    ulong ThreadId,
    bool WriteHasWrapped,
    TargetPointer CurrentPointer,
    TargetPointer ChunkListHead,
    TargetPointer ChunkListTail,
    TargetPointer CurrentWriteChunk);

+                if (pFetched is null || values is null)
+                    throw new NullReferenceException();
+
+                count = Math.Min(count, (uint)values.Length);


+        int ISOSEnum.Skip(uint count)
+        {
+            _index = Math.Min(_index + count, (uint)_threads.Length);
+            return HResults.S_OK;
+        }


+                if (pFetched is null || values is null)
+                    throw new NullReferenceException();
+
+                count = Math.Min(count, (uint)values.Length);


+        int ISOSStressLogMsgEnum.GetArguments(uint messageIndex, uint argCount, ClrDataAddress[] args, uint* pFetched)
+        {
+            if (pFetched is null || args is null)
+                return HResults.E_POINTER;
+
+            if (messageIndex >= _lastBatchCount)
+                return HResults.E_INVALIDARG;


+        int ISOSEnum.Skip(uint count)
+        {
+            _index = Math.Min(_index + count, (uint)_messages.Length);
+            return HResults.S_OK;
+        }


+// StressLog data structures for ISOSDacInterface17
+
+public struct SOSStressLogData
+{
+    public uint LoggedFacilities;
+    public uint Level;
+    public uint MaxSizePerThread;
+    public uint MaxSizeTotal;
+    public int TotalChunks;
+    public ulong TickFrequency;
+    public ulong StartTimestamp;
+    public ulong StartTime;
+}
+
+public struct SOSThreadStressLogData
+{
+    public ClrDataAddress ThreadLogAddress;
+    public ulong ThreadId;
+}
+
+public struct SOSStressMsgData
+{
+    public uint Facility;
+    public ClrDataAddress FormatString;
+    public ulong Timestamp;
+    public uint ArgumentCount;
+}
+
+[GeneratedComInterface]
+[Guid("94a2bd3d-ab3d-43bf-81d8-3ae96b8e33cd")]
+public unsafe partial interface ISOSStressLogThreadEnum : ISOSEnum
+{
+    [PreserveSig]
+    int Next(uint count,
+             [In, Out, MarshalUsing(CountElementName = nameof(count))]
+             SOSThreadStressLogData[] values,
+             uint* pFetched);
+}
+
+[GeneratedComInterface]
+[Guid("437cb033-afe7-4c0f-a4a7-82c891bc049e")]
+public unsafe partial interface ISOSStressLogMsgEnum : ISOSEnum
+{
+    [PreserveSig]
+    int Next(uint count,
+             [In, Out, MarshalUsing(CountElementName = nameof(count))]
+             SOSStressMsgData[] values,
+             uint* pFetched);
+
+    [PreserveSig]
+    int GetArguments(uint messageIndex,
+                     uint argCount,
+                     [In, Out, MarshalUsing(CountElementName = nameof(argCount))]
+                     ClrDataAddress[] args,
+                     uint* pFetched);
+}
+
+[GeneratedComInterface]
+[Guid("2f4bb585-ed50-479e-bbe0-10a95a5da3bb")]
+public unsafe partial interface ISOSDacInterface17
+{
+    [PreserveSig]
+    int GetStressLogData(SOSStressLogData* data);
+
+    [PreserveSig]
+    int GetStressLogThreadEnumerator(
+        DacComNullableByRef<ISOSStressLogThreadEnum> ppEnum);
+
+    [PreserveSig]
+    int GetStressLogMessageEnumerator(
+        ClrDataAddress threadStressLogAddress,
+        DacComNullableByRef<ISOSStressLogMsgEnum> ppEnum);
+
+}


Copilot AI review requested due to automatic review settings June 11, 2026 02:29

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max-charlamb force-pushed the maxcharlamb/stresslog-cdac-bridge branch from 1c1c89a to 714265b Compare June 11, 2026 02:33

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Use ISOSDacInterface17 for DumpLog when available dotnet/diagnostics#5873

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The Operation will be canceled. The next steps may not contain expected logs. dotnet/dnceng#3008

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[browser][coreCLR] Wasm.Console.Node.Sample - undefined symbol: SystemInteropJS_GetManagedStackTrace #129229

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Make NativeAOT StressLog binary-compatible with CoreCLR #129300

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Max Charlamb and others added 3 commits June 16, 2026 11:50

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