Support loading cDAC from SOS installations by hoyosjs · Pull Request #5874 · dotnet/diagnostics

hoyosjs · 2026-06-11T11:31:36Z

Bundle the cDAC into diagnostics tool packages and implement interim loading policy for DAC/cDAC:

.NET 11+ defaults to cDAC unless DOTNET_ENABLE_CDAC is set to allow for runtime-diagnostics pipeline to still do dac/cdac diffing.
Bundle the cDAC into diagnostics tool packages and implement interim loading policy for DAC/cDAC as specified above/
Runtimes command now has a tri-state UseCDac (null= default policy described above, true=force, false=never) with --usecdac true|false|policy**
DataTarget implements ICLRContractLocator and stores resolved contract descriptor address for cDAC initialization
sos-packaging.props cleanup to allow any arch packaging; PackageWithCDac=true by default on main branch so all platforms (win-x64/x86/arm64, linux-*, osx-*) bundle cDAC alongside sos.

…in CLRMD for cdac + dac scenarios

…ntract (#129456) > [!NOTE] > This PR was authored with assistance from GitHub Copilot. ## Summary Fixes a cDAC `GetCodeHeaderData` failure that surfaced as `Unable to get codeHeader information` when SOS ran `!clru` against an IL stub MethodDesc on **Windows x86** with cDAC enabled (the new default behavior on .NET 11 introduced by [dotnet/diagnostics#5874](dotnet/diagnostics#5874)). The CI failure that motivated this is `SOSMethodTests.VarargPInvokeInteropMD` on x86 in dotnet/diagnostics: `!IP2MD` returned the IL stub MethodDesc correctly, but the immediate follow-up `!clru <MD>` printed only `Unable to get codeHeader information`. x64 / arm64 / .NET 8/9/10 were unaffected. ## Root cause x86 uses a fundamentally different GC info encoding from every other architecture: the legacy bit-packed `InfoHdr` byte-stream format from [`src/coreclr/vm/gc_unwind_x86.inl`](https://github.com/dotnet/runtime/blob/main/src/coreclr/vm/gc_unwind_x86.inl) and [`src/coreclr/inc/gcdecoder.cpp`](https://github.com/dotnet/runtime/blob/main/src/coreclr/inc/gcdecoder.cpp) (`USE_GC_INFO_DECODER` is defined for every target except x86, see `eetwain.h:34`). The cDAC `GCInfo` contract registered IGCInfo implementations for X64/Arm64/Arm/LoongArch64/RiscV64 but **not** X86 -- so on x86 it fell through to `default(GCInfo)` and threw `NotImplementedException` from the interface's default `DecodePlatformSpecificGCInfo`. Any SOS path that needed method size on x86 (`!clru`, `GetCodeHeaderData`, `GetMethodRegionInfo`) failed. ## Approach The cDAC already had a substantial x86 `InfoHdr` decoder under `Contracts/StackWalk/Context/X86/GCInfoDecoding/`, used by the x86 stack walker. Rather than write a parallel decoder, this PR **relocates** that existing decoder under the `GCInfo` contract so there is **one canonical x86 GC info implementation** shared between SOS callers and the stack walker -- mirroring how the other architectures' decoders are structured. ## Changes * **Move** `Contracts/StackWalk/Context/X86/GCInfoDecoding/*` → `Contracts/GCInfo/X86/*` (6 files, tracked as renames). Rename namespace `StackWalkHelpers.X86` → `GCInfoHelpers.X86`. * **Rename** the moved class `GCInfo` → `X86GCInfo` to avoid collision with the empty `Contracts.GCInfo` IGCInfo fallback struct. * Make `relativeOffset` ctor arg optional. Implement `IGCInfoDecoder` directly on `X86GCInfo`: `GetCodeLength` / `GetStackBaseRegister` / `GetSizeOfStackParameterArea` are wired up. `GetInterruptibleRanges` and `EnumerateLiveSlots` throw `NotSupportedException` (future work, needed for `!gcroot` / `!clrstack -l` etc.). * Add `GCInfoX86_1` IGCInfo for x86; register it in `CoreCLRContracts.cs` for `RuntimeInfoArchitecture.X86`. * Update `ExecutionManagerCore.GetStackParameterSize` to delegate to `IGCInfo.GetSizeOfStackParameterArea` (one source of truth). * `X86Unwinder` continues to construct `X86GCInfo` directly because it needs offset-bound state (`IsInProlog` / `IsInEpilog` / `PushedArgSize`) not exposed through `IGCInfoDecoder`. ## Tests * New `VarargPInvoke_GetCodeHeaderDataForILStub_ReturnsMethodSize` regression test in `cdac/tests/DumpTests/StackWalkDumpTests.cs` -- asserts the IL stub path returns S_OK with non-zero `MethodSize`. Runs against the existing cdac-dump-helix `windows_x86` matrix on every PR (no pipeline changes needed). * Existing 2509 cDAC unit tests still pass. * Validated end-to-end against `SOSMethodTests.VarargPInvokeInteropMD` x86 .NET 11prev6 cDAC: 4/4 pass after this fix; failed before. ## Docs * `docs/design/datacontracts/GCInfo.md` -- intro now reflects partial x86 support; `GetSizeOfStackParameterArea` API documented; per-method status notes for x86. * `docs/design/datacontracts/StackWalk.md` -- x86 section points at the consolidated decoder location and explains how it's shared. ## Out of scope (future work) * `GetInterruptibleRanges` and `EnumerateLiveSlots` for x86. The underlying transition data is decoded but the adapter to the cDAC `IGCInfoDecoder` shape is not wired up yet. This is what's needed to unblock `!gcroot`, `!clrstack -l`, `!pe` on x86 cDAC. The two pre-existing `[SkipOnArch("x86", "GCInfo decoder does not support x86")]` markers in `StackReferenceDumpTests.cs` should become removable once that lands. --------- Co-authored-by: Max Charlamb <maxcharlamb@microsoft.com> Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com> Co-authored-by: Copilot Autofix powered by AI <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR updates SOS/tool packaging and runtime-loading behavior to bundle and preferentially load the cDAC (mscordaccore_universal) from diagnostics tool installations, with a default policy for .NET 11+ and a new tri-state user control surface.

Changes:

Add cDAC discovery/loading paths across native SOS, SOS.Hosting, and ClrMD runtime creation (including contract descriptor plumbing via ICLRContractLocator).
Introduce an asset/layout resolver (IHostAssetResolver + SOSPackageLayout) so tools consistently locate native binaries (including bundled cDAC) regardless of host.
Update packaging/build logic to optionally bundle cDAC into tool packages and adjust tests/scripts for current SOS output differences.

Reviewed changes

Copilot reviewed 34 out of 34 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/tests/SOS.UnitTests/SOS.cs	Updates test skip conditions (notably Win-x86) for tracked regression coverage.
src/tests/SOS.UnitTests/Scripts/StackAndOtherTests.script	Makes stack verification tolerant to shifted source line numbers.
src/SOS/Strike/util.cpp	Requests cDAC-capable CLR data process in the main SOS load path; whitespace cleanup.
src/SOS/Strike/platform/runtimeimpl.h	Adds cDAC path/process members and policy/helpers to native `Runtime`.
src/SOS/Strike/platform/runtimeimpl.cpp	Implements cDAC path resolution (next to SOS), policy, IXCLRDataProcess creation, and contract descriptor lookup.
src/SOS/Strike/platform/datatarget.h	Extends DataTarget to implement `ICLRContractLocator`.
src/SOS/Strike/platform/datatarget.cpp	Implements `ICLRContractLocator::GetContractDescriptor` and QueryInterface wiring.
src/SOS/Strike/clrma/managedanalysis.cpp	Improves tracing when runtime-based DAC retrieval fails and falls back.
src/SOS/SOS.Package/SOS.Symbol.Package.csproj	Adds single-RID packing support via conditional symbol inclusion.
src/SOS/SOS.Package/SOS.Package.csproj	Ensures `dotnet run` for manifest generation uses the active configuration.
src/SOS/SOS.Package/GenerateManifest/Directory.Build.targets	Shields file-based app build by preventing repo targets import (intentionally empty).
src/SOS/SOS.Package/GenerateManifest/Directory.Build.props	Shields file-based app build by preventing repo props import (intentionally empty).
src/SOS/SOS.InstallHelper/SOS.InstallHelper.csproj	Links shared `SOSPackageLayout` implementation into InstallHelper.
src/SOS/SOS.InstallHelper/InstallHelper.cs	Switches native/managed source path resolution to `SOSPackageLayout`.
src/SOS/SOS.Hosting/SOSPackageLayout.cs	Defines package-relative layout rules for native vs managed SOS assets.
src/SOS/SOS.Hosting/SOSLibrary.cs	Uses `IHostAssetResolver` for native binary location; updates ISOSModule semantics/comments.
src/SOS/SOS.Hosting/SOS.Hosting.csproj	Removes InstallHelper project reference (no longer needed).
src/SOS/SOS.Hosting/RuntimeWrapper.cs	Prefers cDAC for IXCLRDataProcess path; refactors DAC/cDAC load handling.
src/SOS/SOS.Hosting/HostAssetResolver.cs	New global service that resolves native binaries directory and cDAC path.
src/SOS/SOS.Extensions/HostServices.cs	Removes unnecessary `unsafe` modifier; continues to expose ISOSModule data.
src/sos-packaging.props	Reworks packaging inputs/conditions, adds SingleTargetRidPackage/PackageWithCDac semantics.
src/Microsoft.Diagnostics.ExtensionCommands/Host/RuntimesCommand.cs	Replaces previous flags with tri-state `--usecdac true
src/Microsoft.Diagnostics.ExtensionCommands/Host/CommandFormatHelpers.cs	Updates settings output to reflect tri-state cDAC policy.
src/Microsoft.Diagnostics.DebugServices/ISettingsService.cs	Replaces prior cDAC flags with `bool? UseCDac` and documents policy semantics.
src/Microsoft.Diagnostics.DebugServices/IRuntime.cs	Clarifies DAC vs cDAC path responsibilities and nullability for cDAC.
src/Microsoft.Diagnostics.DebugServices/IHostAssetResolver.cs	New contract for resolving host-native asset locations (including cDAC).
src/Microsoft.Diagnostics.DebugServices.Implementation/ServiceManager.cs	Removes SOS.InstallHelper from default assemblies list for extension loading.
src/Microsoft.Diagnostics.DebugServices.Implementation/RuntimeProvider.cs	Adds signature-verification override for the trusted bundled cDAC path.
src/Microsoft.Diagnostics.DebugServices.Implementation/Runtime.cs	Implements cDAC policy, uses host resolver for cDAC path, and prefers cDAC for ClrMD runtime creation.
src/Microsoft.Diagnostics.DebugServices.Implementation/Host.cs	Updates settings storage to `bool? UseCDac`.
src/dbgshim/pkg/Microsoft.Diagnostics.DbgShim.props	Optionally packages cDAC next to dbgshim when enabled.
eng/Versions.props	Defaults `PackageWithCDac=true` on preview branches unless overridden.
eng/InstallNativePackages.targets	Downloads/stages cDAC transport pack content when `PackageWithCDac=true`.
eng/CdacPackageItems.props	Removes prior per-RID cDAC transport pack itemization (now in targets).

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+            ExtDbgOut("GetCDacFilePath: dladdr failed to locate the sos module\n");
+            return nullptr;
+        }
+        strcpy_s(szSOSModulePath.GetPtr(), MAX_LONGPATH, info.dli_fname);


+  <ItemGroup Condition="'$(PackageWithCDac)' == 'true'">
+    <PackageDownload Include="runtime.$(TargetRid).Microsoft.DotNet.Cdac.Transport"
+                     Version="[$(runtimewinx64MicrosoftDotNetCdacTransportVersion)]" />
+    <PackageSourceFiles Include="$(NuGetPackageRoot)runtime.$(TargetRid).microsoft.dotnet.cdac.transport\$(runtimewinx64MicrosoftDotNetCdacTransportVersion)\runtimes\$(TargetRid)\native\*" />
+  </ItemGroup>


+            // Prefer the cDAC for the data-access (IXCLRDataProcess) path when the runtime policy
+            // selects it (GetCDacFilePath returns non-null); fall back to the in-box DAC otherwise.
+            // The ICorDebug/DBI path (CreateCorDebugProcess) always uses the in-box DAC. The flags
+            // parameter is retained for the native IRuntime contract but no longer consulted here.
+            if (_cdacDataProcess == IntPtr.Zero)


max-charlamb · 2026-06-17T18:44:37Z

-        public bool UseContractReader { get; set; }
-
-        public bool ForceUseContractReader { get; set; }
+        public bool? UseCDac { get; set; }


nit: I'd prefer an enum here, something like:

enum CDacLoadPolicy { Default = 0, UseCDac, UseLegacyDac }

I don't mind in this layer. Do you think this should be surfaced to the command?

hoyosjs added 4 commits June 9, 2026 21:23

Basic packaging changes

51c1f2b

Change cDAC loading paths and policies

2b5f735

Implement ICLRContractLocator in native runtime and signing override …

ecdd2b4

…in CLRMD for cdac + dac scenarios

Merge branch 'main' into juhoyosa/bundle-cdac

f5889df

max-charlamb mentioned this pull request Jun 16, 2026

[cdac] Implement IGCInfo for x86; consolidate decoder under GCInfo contract dotnet/runtime#129456

Merged

hoyosjs mentioned this pull request Jun 17, 2026

Re-enable SOS tests on Windows x86 when dotnet/runtime#129456 is resolved #5883

Open

Disable tests failing from dotnet#5883

d0cf0f8

hoyosjs mentioned this pull request Jun 17, 2026

Fix StackAndOtherTests.script line number verification for .NET 11 and Windows x64 #5884

Open

Relax line number against issue dotnet#5884

6325034

hoyosjs marked this pull request as ready for review June 17, 2026 18:20

hoyosjs requested a review from a team as a code owner June 17, 2026 18:20

Copilot AI review requested due to automatic review settings June 17, 2026 18:20

Copilot started reviewing on behalf of hoyosjs June 17, 2026 18:21 View session

Copilot AI reviewed Jun 17, 2026

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steveisok approved these changes Jun 17, 2026

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max-charlamb approved these changes Jun 17, 2026

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Support loading cDAC from SOS installations#5874

Support loading cDAC from SOS installations#5874
hoyosjs wants to merge 6 commits into
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hoyosjs:juhoyosa/bundle-cdac

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