[cDAC] Adding IsLeafFrame and GetContext DacDbi APIs#127195
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rcj1 wants to merge 5 commits intodotnet:mainfrom
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[cDAC] Adding IsLeafFrame and GetContext DacDbi APIs#127195rcj1 wants to merge 5 commits intodotnet:mainfrom
rcj1 wants to merge 5 commits intodotnet:mainfrom
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Pull request overview
This PR adds support for new stack-walk related APIs across the cDAC contracts layer and the legacy DacDbi surface, focusing on retrieving thread contexts and determining leaf frames, and updates dump-based tests accordingly. It also removes the native DAC fallback behavior when the data target doesn’t implement GetThreadContext, aligning with the PR’s stated assumption.
Changes:
- Add
IThread.GetContext(...)andIStackWalk.AreContextsEqual(...)contract APIs and use them from stack walking and DacDbi implementations. - Implement
DacDbiImpl.GetContext/DacDbiImpl.IsLeafFramein managed cDAC and add dump tests for these APIs. - Update native DAC
GetContext/IsLeafFrameto always rely onGetThreadContext(noE_NOTIMPLfallback).
Reviewed changes
Copilot reviewed 20 out of 20 changed files in this pull request and generated 2 comments.
Show a summary per file
| File | Description |
|---|---|
| src/native/managed/cdac/tests/DumpTests/StackWalkDumpTests.cs | Adds dump tests for Thread.GetContext and StackWalk.AreContextsEqual. |
| src/native/managed/cdac/tests/DumpTests/DacDbi/DacDbiStackWalkDumpTests.cs | New dump tests validating DacDbiImpl GetContext and IsLeafFrame. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/IDacDbiInterface.cs | Updates interop signatures to use byte* context buffers. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs | Implements IsLeafFrame and GetContext via contracts (with DEBUG cross-validation). |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Thread_1.cs | Implements IThread.GetContext using filter contexts or TryGetThreadContext. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/StackWalk_1.cs | Adds AreContextsEqual and routes stackwalk thread-context acquisition through Thread.GetContext. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/*.cs | Splits context flags into FullContextFlags vs AllContextFlags across supported architectures. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/IPlatformContext.cs | Renames/expands context-flag properties to FullContextFlags and AllContextFlags. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/IPlatformAgnosticContext.cs | Same flag-property updates at platform-agnostic level. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/ContextHolder.cs | Plumbs new context-flag properties through the holder type. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IThread.cs | Adds ThreadContextSource and the GetContext contract API. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IStackWalk.cs | Adds AreContextsEqual to the StackWalk contract surface. |
| src/coreclr/debug/daccess/dacdbiimplstackwalk.cpp | Updates native IsLeafFrame to always use GetThreadContext directly. |
| src/coreclr/debug/daccess/dacdbiimpl.cpp | Removes E_NOTIMPL fallback path from native GetContext. |
| docs/design/datacontracts/StackWalk.md | Documents new AreContextsEqual API behavior. |
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
jkotas
reviewed
Apr 21, 2026
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| // Compares two raw thread contexts for equality of the architecture's control registers. | ||
| // Typically this means stack pointer, frame pointer, and instruction pointer; however, on ARM32 | ||
| // the native DAC compares only SP and IP/PC and does not require frame pointer equality. |
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Frame pointer is optional. Method does not have to have one.
Is the frame pointer equality actually needed for what it does (on all architectures)? I would expect SP + IP to be enough to detect the leaf frame.
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yes, this should work.
jkotas
reviewed
Apr 21, 2026
| byte[] givenContext = new byte[leafContext.Length]; | ||
| new Span<byte>(pContext, givenContext.Length).CopyTo(givenContext); | ||
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| *pResult = sw.AreContextsEqual(givenContext, leafContext) ? Interop.BOOL.TRUE : Interop.BOOL.FALSE; |
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Would it make more sense to just compare IP and SP here instead of behind IStackWalk contract?
…er.Contracts/Contracts/StackWalk/StackWalk_1.cs Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
jkotas
reviewed
Apr 21, 2026
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| *pResult = givenCtx.StackPointer == leafCtx.StackPointer | ||
| && givenCtx.InstructionPointer == leafCtx.InstructionPointer | ||
| ? Interop.BOOL.TRUE : Interop.BOOL.FALSE; |
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Fix the unmanaged implementation of the IsLeafFrame to match?
Comment on lines
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| Assert.NotNull(nonLeafContext); | ||
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| Interop.BOOL result; | ||
| fixed (byte* pContext = nonLeafContext) | ||
| { |
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nonLeafContext is declared as byte[]?, and after Assert.NotNull(nonLeafContext) the compiler may still treat it as nullable for subsequent uses (e.g., the fixed statement), depending on nullable annotations on xUnit. To avoid nullable warnings/errors (and make the non-null assumption explicit), assign the non-null value back (e.g., nonLeafContext = Assert.NotNull(nonLeafContext);) or otherwise cast/throw so the type is byte[] before the fixed block.
This was referenced Apr 22, 2026
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Assuming we don't care about datatargets that don't implement
GetThreadContext.