[cDAC] Fix context alignment and content on debug validation paths#129720
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rcj1 wants to merge 1 commit into
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[cDAC] Fix context alignment and content on debug validation paths#129720rcj1 wants to merge 1 commit into
rcj1 wants to merge 1 commit into
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rcj1
requested review from
barosiak,
Copilot,
hoyosjs,
max-charlamb and
noahfalk
rcj1
changed the title
max-charlamb
approved these changes
Jun 22, 2026
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Tagging subscribers to this area: @steveisok, @tommcdon, @dotnet/dotnet-diag |
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Pull request overview
This PR adjusts cDAC interop/debug-validation code paths to (1) ensure thread/context buffers are 16-byte aligned before being passed to callbacks/legacy implementations and (2) clear native buffers before they’re written/compared, reducing the chance of alignment faults and spurious diffs from uninitialized bytes.
Changes:
- Zero-initialize the temporary aligned buffer used when calling the
readThreadContextdelegate inmscordaccore_universal. - Replace
byte[] + fixedwithNativeMemory.AlignedAlloc(..., 16)in legacy stack-walk validation paths, and clear the native buffer before calling legacy APIs.
Show a summary per file
| File | Description |
|---|---|
src/native/managed/cdac/mscordaccore_universal/Entrypoints.cs |
Clears the temporary aligned buffer before invoking readThreadContext. |
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs |
Uses 16-byte-aligned native buffers (and clears them) when calling legacy stack-walk APIs for validation. |
Copilot's findings
- Files reviewed: 2/2 changed files
- Comments generated: 5
Comment on lines
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| uint contextSize = IPlatformAgnosticContext.GetContextForPlatform(_target).Size; | ||
| byte[] localContextBuf = new byte[contextSize]; | ||
| nuint legacyHandle = 0; | ||
| fixed (byte* pLocal = localContextBuf) | ||
| byte* pLocal = (byte*)NativeMemory.AlignedAlloc(contextSize, 16); |
| byte* pLocal = (byte*)NativeMemory.AlignedAlloc(contextSize, 16); | ||
| try | ||
| { | ||
| new Span<byte>(pLocal, (int)contextSize).Clear(); |
| { | ||
| byte[] localContextBuf = new byte[contextSize]; | ||
| fixed (byte* pLocal = localContextBuf) | ||
| byte* pLocal = (byte*)NativeMemory.AlignedAlloc(contextSize, 16); |
| byte* pLocal = (byte*)NativeMemory.AlignedAlloc(contextSize, 16); | ||
| try | ||
| { | ||
| new Span<byte>(pLocal, (int)contextSize).Clear(); |
Comment on lines
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+1348
| if (_legacy is not null && LegacyFallbackHelper.CanFallback()) | ||
| { | ||
| uint contextSize = IPlatformAgnosticContext.GetContextForPlatform(_target).Size; | ||
| byte[] localContextBuf = new byte[contextSize]; | ||
| nuint legacyHandle = 0; | ||
| fixed (byte* pLocal = localContextBuf) | ||
| byte* pLocal = (byte*)NativeMemory.AlignedAlloc(contextSize, 16); |
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Ensure that buffers passed into debug validation are 16-aligned. Also ensure that native memory is cleared before writing into it.