Add ISOSDacInterface18 for GCInfo inspection APIs

[max-charlamb]

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ISOSDacInterface18 for GCInfo inspection APIs

Add ISOSDacInterface18 with 4 COM methods exposing GC info data through the cDAC for the SOS !GCInfo command:

• GetGCInfoHeader -- header fields (version, code size, prolog, stack base register, GS cookie, PSP sym, generics context)
• GetGCInfoInterruptibleRanges -- code regions where GC can interrupt execution
• GetGCInfoSafePoints -- specific offsets with point-in-time GC slot liveness
• GetGCInfoSlotLifetimes -- unified slot lifetime ranges (register + stack combined via SOSGCSlotLifetime with IsRegister discriminator)

IGCInfo contract changes

• Add GetHeader, GetSafePoints, GetSlotLifetimes to IGCInfo/IGCInfoDecoder
• Consolidate GetStackBaseRegister and GetSizeOfStackParameterArea into GCInfoHeader (accessed via GetHeader()). These fields require the same decode depth (DecodePoints.ReversePInvoke) as the rest of the header, so there's no performance benefit to keeping them separate.
• Keep GetCodeLength as a standalone method -- it only decodes to DecodePoints.CodeLength, which is significantly cheaper than the full header decode. Used on the hot path by EEJitManager/InterpreterJitManager/ReadyToRunJitManager for method size lookups.
• Keep GetCalleePoppedArgumentsSize as a standalone method -- it returns 0 via a default interface method on non-x86 platforms without any decoding. Only x86 reads the ArgCount header field.
• Eagerly decode safe points in DecodeSafePoints, stored denormalized
• Single-pass chunk decoder for interruptible slot lifetimes (O(transitions), not O(codeLength))
• Safe-point-only methods emit [safePointOffset, safePointOffset+1) per live slot per safe point
• Implement x86 GCInfo support (GetHeader/GetSafePoints/GetSlotLifetimes)
• Add GenericsContextKind.None as default enum value
• Fix GSCookieValidRange -- only set when GSCookie is present
• Native DAC returns E_NOINTERFACE for ISOSDacInterface18 (cDAC-only interface)

Bug fix: ARM thumb bit in relative offset computation

EEJitManager.GetMethodInfo and InterpreterJitManager.GetMethodInfo computed relativeOffset as jittedCodeAddress.Value - codeStart.Value. On ARM (Thumb-2), TargetCodePointer.Value includes the thumb bit (bit 0 = 1), but codeStart (a TargetPointer from the nibble map) does not. This produced a relative offset that was off by 1, causing FindSafePoint and EnumerateLiveSlots to look up the wrong offset.

Fixed by stripping the thumb bit via CodePointerUtils.AddressFromCodePointer before computing the difference. ReadyToRunJitManager was already doing this correctly.

Companion PR

• WIP: Update SOS for unified ISOSDacInterface18 GCInfo API diagnostics#5898 -- SOS !GCInfo command updated to use ISOSDacInterface18 with legacy-compatible timeline output format

[Copilot]

Pull request overview

This PR introduces a new SOS-DAC COM interface (ISOSDacInterface18) intended to expose GCInfo inspection APIs (header, safe points, interruptible ranges, and slot lifetimes), alongside expanding the managed cDAC IGCInfo contract and decoder surface to project the same data.

Changes:

• Add ISOSDacInterface18 (IDL + prebuilt headers + C# GeneratedComInterface) and wire it up through DAC QueryInterface.
• Implement GCInfo inspection entrypoints in the native DAC (ClrDataAccess) using GcInfoDecoder / GcInfoDumper, and extend the managed GCInfo decoder/contracts with header/safe point/lifetime APIs.
• Extend GCInfo platform traits to include PSP symbol encoding base across architectures; add placeholder (E_NOTIMPL) stubs in the managed legacy SOS DAC implementation.

Reviewed changes

Copilot reviewed 20 out of 20 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs	Adds ISOSDacInterface18 exposure but currently returns E_NOTIMPL for all new methods.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ISOSDacInterface.cs	Defines GCInfo structs and ISOSDacInterface18 managed COM declarations.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/X86/GCInfo.cs	Implements newly added IGCInfoDecoder members on x86 by throwing NotSupportedException.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/PlatformTraits/RISCV64GCInfoTraits.cs	Adds PSP symbol stack-slot encoding base.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/PlatformTraits/LoongArch64GCInfoTraits.cs	Adds PSP symbol stack-slot encoding base.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/PlatformTraits/InterpreterGCInfoTraits.cs	Adds PSP symbol stack-slot encoding base.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/PlatformTraits/IGCInfoTraits.cs	Extends traits interface with PSP_SYM_STACK_SLOT_ENCBASE.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/PlatformTraits/ARMGCInfoTraits.cs	Adds PSP symbol stack-slot encoding base.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/PlatformTraits/ARM64GCInfoTraits.cs	Adds PSP symbol stack-slot encoding base.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/PlatformTraits/AMD64GCInfoTraits.cs	Adds PSP symbol stack-slot encoding base.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/IGCInfoDecoder.cs	Expands decoder interface to include header/safe points/lifetimes.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/GCInfoDecoder.cs	Adds decoding/projection for header/safe points/lifetimes (includes a correctness issue in safe-point lookup and a potentially expensive lifetime algorithm).
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/GCInfo_1.cs	Plumbs new IGCInfo contract methods to the decoder implementation.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IGCInfo.cs	Adds public contract types (header/lifetime records) and new IGCInfo methods.
src/coreclr/pal/prebuilt/inc/sospriv.h	Updates prebuilt SOS-DAC header with new interface and structs.
src/coreclr/pal/prebuilt/idl/sospriv_i.cpp	Adds GUID definitions for new SOS-DAC interfaces/enums.
src/coreclr/inc/sospriv.idl	Adds IDL definitions for GCInfo structs and ISOSDacInterface18.
src/coreclr/debug/daccess/request.cpp	Implements ClrDataAccess::GetGCInfo* methods and supporting helpers.
src/coreclr/debug/daccess/dacimpl.h	Extends ClrDataAccess inheritance and declares ISOSDacInterface17/18 methods.
src/coreclr/debug/daccess/daccess.cpp	Extends QueryInterface to support ISOSDacInterface17/18.

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Comments suppressed due to low confidence (1)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GCInfo/GCInfoX86_1.cs:41

• GCInfoX86_1 doesn’t implement the new IGCInfo members (GetHeader/GetSafePoints/GetSlotLifetimes). Since these are default interface methods, calls will fall back to the interface default (throwing NotImplementedException) on x86, which will break GcScanner now that it calls GetHeader().

    uint IGCInfo.GetCodeLength(IGCInfoHandle gcInfoHandle)
        => AssertCorrectHandle(gcInfoHandle).GetCodeLength();

    uint IGCInfo.GetCalleePoppedArgumentsSize(IGCInfoHandle gcInfoHandle)
        => AssertCorrectHandle(gcInfoHandle).GetCalleePoppedArgumentsSize();

    IReadOnlyList<InterruptibleRange> IGCInfo.GetInterruptibleRanges(IGCInfoHandle gcInfoHandle)
        => AssertCorrectHandle(gcInfoHandle).GetInterruptibleRanges();

    IReadOnlyList<LiveSlot> IGCInfo.EnumerateLiveSlots(IGCInfoHandle gcInfoHandle, uint instructionOffset, GcSlotEnumerationOptions options)
        => AssertCorrectHandle(gcInfoHandle).EnumerateLiveSlots(instructionOffset, options);

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Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

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Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

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

[Copilot]

Pull request overview

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.