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 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);

Initialize *pFetched = 0 early in Next and GetArguments so callers see a well-defined value on all failure paths. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

jkotas · 2026-06-17T23:31:27Z

Remove unused fields from SOS stress log structs

Should these unused field be deleted from the data contract as well?

max-charlamb · 2026-06-17T23:44:37Z

Remove unused fields from SOS stress log structs

Should these unused field be deleted from the data contract as well?

The datadescriptors are previously existing for the IStressLog when used by the StressLogAnalzer.csproj tool. I looked into the source there are we do seem to be leaking more data than we need in the contract.

I'm happy to remove the things we don't use, but I'd prefer to do so in a follow-up.

jkotas · 2026-06-17T23:48:26Z

I'm happy to remove the things we don't use, but I'd prefer to do so in a follow-up.

Sounds good

Messages with Timestamp==0 can appear at chunk boundaries on x86 with small stress log sizes. These represent unwritten/partial message slots and are valid contract output per the spec. Update tests to find the first message with a non-zero timestamp rather than assuming the first message is valid. 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 2 comments.

noahfalk

👍

Matches the convention used by other SOSDAC sized-buffer APIs where S_FALSE indicates fewer items returned than requested. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

On x86 with small stress logs, partially-written messages can have non-zero timestamps but null format strings due to chunk-boundary wrapping. Look for messages with both valid timestamp and format string. 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 3 comments.

Temporary diagnostics to understand why x86 can't find valid messages: prints thread count, pointer size, per-thread metadata, and per-message timestamp/format/facility/argcount. 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.

StressLog.modules is an inline array (ModuleDesc modules[MAX_MODULES]), not a pointer. Using [Field] reads the first bytes of the array as a pointer value, which on x86 happens to be the coreclr base address (from modules[0].baseAddress), causing GetFormatPointer's module table lookup to iterate from the PE header instead of the module descriptors. Using [FieldAddress] returns the address of the inline array itself, which is the correct base for iterating the ModuleDesc entries. Verified fix locally against CI x86 dump that previously failed. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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

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max-charlamb added area-Diagnostics-cdac and removed area-Diagnostics-coreclr labels Jun 11, 2026

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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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Zero out pFetched before error paths in enumerators

28d43da

Initialize *pFetched = 0 early in Next and GetArguments so callers see a well-defined value on all failure paths. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Comment thread src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs

Comment thread src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs

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[ci-scan] Test failure: cDAC stress test on Windows.11.Arm64.Open #129556

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slow macOS - "##[error]The job running on agent Azure Pipelines 9 ran longer than the maximum time of 60 minutes." dotnet/dnceng#1883

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Return S_FALSE from GetArguments when fewer args than requested

c8087f8

Matches the convention used by other SOSDAC sized-buffer APIs where S_FALSE indicates fewer items returned than requested. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

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Comment thread src/native/managed/cdac/tests/DumpTests/StressLogDumpTests.cs

Comment thread src/native/managed/cdac/tests/DumpTests/StressLogDumpTests.cs

Comment thread src/native/managed/cdac/tests/DumpTests/StressLogDumpTests.cs Outdated

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max-charlamb commented Jun 11, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Summary

Motivation

Changes

cDAC contract updates

ISOSDacInterface17 definition

SOSDacImpl bridge

IDL + testing

Test Results

Related PRs

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jkotas commented Jun 17, 2026

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max-charlamb commented Jun 11, 2026 •

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