[cDAC] Remove DT_CONTEXT from DBI layer

[rcj1]

In order to encapsulate the target-specific knowledge within the DacDbi and therefore within the cDAC, it is necessary to remove the DT_CONTEXT struct, which represents the target context, from the DBI layer. This PR accomplishes this by:

• Creating 10 new DacDbi APIs that provide target-specific information especially pertaining to contexts

    int GetTargetContextSize(ContextSizeFlags flags, uint* pSize);
    int WriteRegistersToContext(byte* ctxBuf, uint cb, CorDebugRegister* regs, uint nRegs, ulong* values);
    int ReadRegistersFromContext(byte* ctxBuf, uint cb, CorDebugRegister* regs, uint nRegs, ulong* pValues);
    int GetAvailableRegistersMask(Interop.BOOL fActive, Interop.BOOL fQuickUnwind, uint regCount, byte* pAvailable);
    int ConvertJitRegNumToCorDebugRegister(uint jitRegNum, CorDebugRegister* pReg);
    int ReadFloatRegistersFromContext(byte* ctxBuf, uint cb, uint maxValues, double* values, uint* pValuesCount, int* pFirstFloatReg, uint* pFloatStackTop);
    int GetTargetInfo(TargetInfo* pTargetInfo);
    int ContextHasExtendedRegisters(byte* ctxBuf, uint cb, Interop.BOOL* pResult);
    int CompareControlRegisters(byte* ctxBuf1, uint cb1, byte* ctxBuf2, uint cb2, Interop.BOOL* pResult);
    int CopyContext(byte* dstCtxBuf, uint cbDst, byte* srcCtxBuf, uint cbSrc, uint flags);

• Using said new DacDbi APIs to replace the architecture-specific reading in (arch)/cordbregisterset.cpp
• Implementing DacDbi APIs in cDAC
• Where we are interop live debugging, that is where we know the host is the same as the target, replacing DT_CONTEXT with T_CONTEXT
• Where target and host context may vary, switching from context structs to opaque byte buffers that are queried through DacDbi

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[Copilot]

Pull request overview

This PR refactors the DBI / cDAC boundary so the DBI layer no longer depends on a DT_CONTEXT struct, moving context-layout knowledge behind new IDacDbiInterface APIs and using opaque target-sized byte buffers where host/target layouts may differ.

Changes:

• Extends IDacDbiInterface (IDL + managed projection) with new context/query/register APIs and switches multiple stackwalk/context entrypoints from DT_CONTEXT* to BYTE*.
• Updates CoreCLR debugger right-side stackwalking and register-set plumbing to work over opaque context buffers and DAC-provided helpers (e.g., CopyContext, Read/WriteRegistersFromContext).
• Updates managed contract context models to describe register copy sets/spans and adds an “Extended” register category.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/IDacDbiInterface.cs	Updates STRData ctx to BYTE* and adds new DacDbi APIs + related enums/structs for context/register operations.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/X86Context.cs	Adds scalar/wide register copy metadata; adjusts register classifications and extended-reg handling.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/RISCV64Context.cs	Adds scalar/wide register copy metadata; adjusts control/general register typing.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/RegisterAttribute.cs	Adds RegisterType.Extended.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/LoongArch64Context.cs	Updates context sizing and floating-point layout; adds scalar/wide register copy metadata and register typing changes.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/IPlatformContext.cs	Adds default properties for extended-register sizing and new register copy metadata accessors.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/IPlatformAgnosticContext.cs	Adds abstract extended-register properties and register copy metadata accessors used for flag-gated copies.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/ContextHolder.cs	Forwards new extended-register properties and register copy metadata accessors.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/ARMContext.cs	Adds scalar/wide register copy metadata; adjusts register typing.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/ARM64Context.cs	Adds scalar/wide register copy metadata; adjusts register typing.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/AMD64Context.cs	Adds scalar/wide register copy metadata and explicit XMM span; adjusts register typing and FP/debug tagging.
src/coreclr/inc/dacdbi.idl	Removes DT_CONTEXT typedef; switches context parameters to BYTE*; adds new DacDbi context/register APIs and TargetInfo.
src/coreclr/debug/shared/riscv64/primitives.cpp	Switches CORDbgCopyThreadContext to T_CONTEXT and uses CONTEXT_* flags.
src/coreclr/debug/shared/loongarch64/primitives.cpp	Switches CORDbgCopyThreadContext to T_CONTEXT and uses CONTEXT_* flags; updates FP span sizing.
src/coreclr/debug/shared/i386/primitives.cpp	Switches CORDbgCopyThreadContext to T_CONTEXT and uses CONTEXT_* flags.
src/coreclr/debug/shared/arm64/primitives.cpp	Switches CORDbgCopyThreadContext to T_CONTEXT and uses CONTEXT_* flags.
src/coreclr/debug/shared/arm/primitives.cpp	Switches CORDbgCopyThreadContext to T_CONTEXT and uses CONTEXT_* flags; updates debug span constant.
src/coreclr/debug/shared/amd64/primitives.cpp	Switches CORDbgCopyThreadContext to T_CONTEXT.
src/coreclr/debug/inc/riscv64/primitives.h	Switches helpers to T_CONTEXT.
src/coreclr/debug/inc/loongarch64/primitives.h	Switches helpers to T_CONTEXT.
src/coreclr/debug/inc/i386/primitives.h	Switches helpers to T_CONTEXT.
src/coreclr/debug/inc/dbgipcevents.h	Removes arch-specific float count and SP/FP address helpers; introduces CORDB_MAX_FLOAT_REGISTERS.
src/coreclr/debug/inc/dacdbistructures.h	Changes Debugger_STRData::ctx to BYTE* and documents as opaque target context bytes.
src/coreclr/debug/inc/dacdbiinterface.h	Switches various context params to BYTE*; adds new DacDbi context/register APIs and target info enums/struct.
src/coreclr/debug/inc/common.h	Updates CORDbgCopyThreadContext signature to T_CONTEXT.
src/coreclr/debug/inc/arm64/primitives.h	Switches helpers to T_CONTEXT; removes unused typedef.
src/coreclr/debug/inc/arm/primitives.h	Switches helpers to T_CONTEXT; removes unused typedef.
src/coreclr/debug/inc/arm_primitives.h	Switches helpers to T_CONTEXT and adjusts breakpoint-PC logic preprocessor condition.
src/coreclr/debug/inc/amd64/primitives.h	Switches helpers to T_CONTEXT; removes unused typedef.
src/coreclr/debug/ee/debugger.cpp	Removes DT_CONTEXT casts when calling breakpoint-PC and SS-flag helpers.
src/coreclr/debug/ee/controller.cpp	Removes DT_CONTEXT casts when calling SS-flag and IP helpers.
src/coreclr/debug/di/valuehome.cpp	Replaces architecture-specific context/register mutations with DAC register read/write and target-sized buffers.
src/coreclr/debug/di/stdafx.h	Replaces per-arch thread-context macros with unified DbiGet/SetThreadContext(T_CONTEXT*) declarations.
src/coreclr/debug/di/shimstackwalk.cpp	Uses DAC register reads for SP and converts shim contexts to opaque target-sized buffers.
src/coreclr/debug/di/shimpriv.h	Updates shim stackwalk state to own target-sized context buffers and passes sizes through.
src/coreclr/debug/di/shimlocaldatatarget.cpp	Switches local datatarget thread-context casts from DT_CONTEXT to T_CONTEXT.
src/coreclr/debug/di/rsstackwalk.cpp	Converts stackwalk internal state from DT_CONTEXT to opaque buffers and uses DAC CopyContext.
src/coreclr/debug/di/rsregsetcommon.cpp	Converts register-set state from cached DT_CONTEXT to opaque buffers and uses DAC CopyContext.
src/coreclr/debug/di/rspriv.h	Updates many signatures/fields from DT_CONTEXT to BYTE*/T_CONTEXT; adds context-size caching and DAC register helpers.
src/coreclr/debug/di/process.cpp	Adds target-context-size caching via DAC; switches SafeRead/WriteThreadContext to operate on opaque buffers and target info queries.
src/coreclr/debug/di/platformspecific.cpp	Stops including per-arch cordbregisterset.cpp implementations; keeps per-arch primitives.
src/coreclr/debug/di/module.cpp	Routes JIT-reg-num → CorDebugRegister mapping through DAC-backed helper on CordbProcess.
src/coreclr/debug/di/cordb.cpp	Unifies DbiGet/SetThreadContext implementation around T_CONTEXT and updated alignment logic.
src/coreclr/debug/di/CMakeLists.txt	Adds a shared cordbregisterset.cpp (new common register-set impl) and removes floatconversion ASM wiring.
src/coreclr/debug/daccess/dacdbiimplstackwalk.cpp	Switches DacDbi stackwalk context entrypoints to BYTE* but reinterprets to DT_CONTEXT internally.
src/coreclr/debug/daccess/dacdbiimpl.h	Updates interface signatures for BYTE* contexts and declares new DacDbi context/register APIs.
src/coreclr/debug/di/riscv64/floatconversion.S	Removes unused float conversion assembly.
src/coreclr/debug/di/riscv64/cordbregisterset.cpp	Removes per-arch register-set implementation.
src/coreclr/debug/di/loongarch64/floatconversion.S	Removes unused float conversion assembly.
src/coreclr/debug/di/loongarch64/cordbregisterset.cpp	Removes per-arch register-set implementation.
src/coreclr/debug/di/i386/cordbregisterset.cpp	Removes per-arch register-set implementation.
src/coreclr/debug/di/arm64/floatconversion.S	Removes unused float conversion assembly.
src/coreclr/debug/di/arm64/floatconversion.asm	Removes unused float conversion assembly.
src/coreclr/debug/di/arm64/cordbregisterset.cpp	Removes per-arch register-set implementation.
src/coreclr/debug/di/arm/floatconversion.S	Removes unused float conversion assembly.
src/coreclr/debug/di/arm/cordbregisterset.cpp	Removes per-arch register-set implementation.
src/coreclr/debug/di/amd64/floatconversion.S	Removes unused float conversion assembly.
src/coreclr/debug/di/amd64/FloatConversion.asm	Removes unused float conversion assembly.
src/coreclr/debug/di/amd64/cordbregisterset.cpp	Removes per-arch register-set implementation.

Copilot's findings

• Files reviewed: 62/62 changed files
• Comments generated: 5

[Copilot]

Copilot's findings

• Files reviewed: 65/65 changed files
• Comments generated: 5

[Copilot]

Copilot's findings

• Files reviewed: 65/65 changed files
• Comments generated: 3

[Copilot]

Copilot's findings

• Files reviewed: 69/69 changed files
• Comments generated: 3

[Copilot]

Copilot's findings

• Files reviewed: 69/69 changed files
• Comments generated: 2

[Copilot]

Copilot's findings

• Files reviewed: 70/70 changed files
• Comments generated: 2

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (1)

src/coreclr/debug/inc/common.h:64

• The comment claims the buffers "only need to be at least sizeof(DT_CONTEXT)", but the helper APIs below (ContextSizeForFlags/CheckContextSizeForFlags) and the x86 implementation allow smaller buffers when CONTEXT_EXTENDED_REGISTERS isn’t requested. This comment should describe the actual contract (size is flag-dependent) so future callers don’t over-allocate or assume a hard minimum of sizeof(DT_CONTEXT).

• Files reviewed: 74/74 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (2)

src/coreclr/debug/di/rsstackwalk.cpp:357

• The destination ContextFlags are not being merged with the incoming context's ContextFlags before calling CopyContext. With flags==0, CopyContext preserves the destination's existing flags and the chunk-wise copy only updates chunks where (dstFlags & srcFlags) contains the chunk flag. This differs from the previous logic that OR'ed the flags (tmpCtx.ContextFlags |= pSrcContext->ContextFlags), and can silently skip applying updates from the incoming context when the cached context lacks those flags.

    memcpy(tmpCtx, m_pContextBuffer, cbCtx);
    // flags == 0: tmpCtx already carries the desired ContextFlags (copied above).
    ContextBuffer temporaryContext = { tmpCtx, cbCtx };
    ContextBuffer sourceContext = { context, contextSize };
    IfFailThrow(pDAC->CopyContext(temporaryContext, sourceContext, 0));

src/coreclr/debug/inc/common.h:65

• This comment says the buffers must be at least sizeof(DT_CONTEXT), but the implementation (e.g. i386 CopyThreadContext) explicitly allows smaller buffers when ContextFlags do not include extended register state. The doc here should match the actual size contract (ContextFlags + the regions selected by those flags).

• Files reviewed: 74/74 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (3)

src/coreclr/debug/di/rsstackwalk.cpp:357

• SetContextWorker no longer ORs the destination ContextFlags with the incoming context's flags before copying, so CopyContext(..., flags: 0) may skip copying chunks that are present in the incoming context but not already enabled in the cached context flags. The old code explicitly did tmpCtx.ContextFlags |= pSrcContext->ContextFlags before copying. Consider stamping the destination flags when calling CopyContext so the copy doesn't depend on the cached ContextFlags value.

    ULONG32 cbCtx = GetProcess()->GetTargetContextSize();
    NewArrayHolder<BYTE> tmpCtx(new BYTE[cbCtx]);
    memcpy(tmpCtx, m_pContextBuffer, cbCtx);
    // flags == 0: tmpCtx already carries the desired ContextFlags (copied above).
    ContextBuffer temporaryContext = { tmpCtx, cbCtx };
    ContextBuffer sourceContext = { context, contextSize };
    IfFailThrow(pDAC->CopyContext(temporaryContext, sourceContext, 0));

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/X86Context.cs:220

• TryWriteFloatingPointRegister assumes any value length other than 4 bytes is an 8-byte double and calls ReadInt64LittleEndian(value). If a caller passes an unexpected size (e.g. 0, 2, 10), this will throw instead of returning false. Add an explicit length check for 4/8 bytes before decoding.
  src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/X86Context.cs:231
• TryGetX87SlotOffset reads StatusWord via context.Slice(statusWordOffset) without checking context length first. If the caller passes a truncated context buffer, this will throw. Other platform implementations return false on undersized spans; this helper should do the same.

• Files reviewed: 74/74 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (2)

src/coreclr/debug/inc/common.h:64

• The comment says the buffers only need to be at least sizeof(DT_CONTEXT), but the codebase also supports smaller CONTEXT buffers when ContextFlags omits trailing regions (e.g., x86 without CONTEXT_EXTENDED_REGISTERS via ContextSizeForFlags / CheckContextSizeForBuffer). Please update the comment to reflect the actual minimum size requirement so callers don’t assume they must always allocate sizeof(DT_CONTEXT).
  src/coreclr/debug/di/rsstackwalk.cpp:357
• SetContextWorker no longer merges the incoming ContextFlags into the temporary context before calling CopyContext with flags==0 (which preserves the destination flags). If the current cached context has fewer flags than the incoming context, CopyContext will skip copying those requested chunks, changing behavior vs the previous tmpCtx.ContextFlags |= pSrcContext->ContextFlags logic.

    ULONG32 cbCtx = GetProcess()->GetTargetContextSize();
    NewArrayHolder<BYTE> tmpCtx(new BYTE[cbCtx]);
    memcpy(tmpCtx, m_pContextBuffer, cbCtx);
    // flags == 0: tmpCtx already carries the desired ContextFlags (copied above).
    ContextBuffer temporaryContext = { tmpCtx, cbCtx };
    ContextBuffer sourceContext = { context, contextSize };
    IfFailThrow(pDAC->CopyContext(temporaryContext, sourceContext, 0));

• Files reviewed: 74/74 changed files
• Comments generated: 0 new

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (2)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/X86Context.cs:221

• TryWriteFloatingPointRegister assumes the incoming byte payload is either 4 or 8 bytes, but it doesn't validate this. Any other length will currently fall into the 8-byte path and can throw (e.g. ReadInt64LittleEndian on a short span) or encode garbage, which is risky given this helper sits underneath the DacDbi register-write path. Consider explicitly rejecting non-(4|8) sized inputs and returning false.
  src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/SimdRegisterAccess.cs:44
• SimdRegisterAccess.TryWriteRegister advertises writing a scalar value that is "(4 or 8 bytes)", but it currently accepts any length and will blindly copy it into the register slot. Since this helper feeds the DacDbi float/SIMD scalar register write path, it's safer to enforce the documented 4/8-byte contract and reject other sizes to avoid corrupting the CONTEXT image.

• Files reviewed: 74/74 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (2)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/X86Context.cs:220

• TryWriteFloatingPointRegister assumes the value span is either 4 or 8 bytes; any other length will throw from BinaryPrimitives.ReadInt64LittleEndian instead of returning false. Since this is exposed via IPlatformContext/IPlatformAgnosticContext, it should validate input length and fail gracefully.
  src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/X86Context.cs:238
• TryGetX87SlotOffset reads StatusWord via context.Slice(...) without checking the span length first. If an undersized context buffer is ever passed in, this will throw instead of returning false. Add a bounds check before reading the status word so the helper fails gracefully.

• Files reviewed: 74/74 changed files
• Comments generated: 1

[Copilot]

Copilot's findings

Comments suppressed due to low confidence (4)

src/coreclr/debug/di/rsthread.cpp:5531

• CordbNativeFrame::GetRegisterSet creates a CordbRegisterSet that holds a raw pointer to the frame’s context buffer (GetContext()) but does not take ownership / make a copy. If the caller releases the ICorDebugFrame but keeps the ICorDebugRegisterSet alive (legal COM usage), the frame’s context buffer can be freed while the register set still uses it, leading to use-after-free when reading registers.

        // allocate a new CordbRegisterSet object
        RSInitHolder<CordbRegisterSet> pRegisterSet(new CordbRegisterSet(GetContext(),
                                                                         m_pThread,
                                                                         IsLeafFrame(),
                                                                         false));

src/coreclr/debug/inc/common.h:64

• The comment claims the context buffers must be at least sizeof(DT_CONTEXT), but the helpers below (ContextSizeForFlags / CheckContextSizeForBuffer) and the x86 copy logic allow smaller buffers when trailing regions (e.g., extended registers) are not requested via ContextFlags. The documentation should match the actual size contract.
  src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/X86Context.cs:220
• TryWriteFloatingPointRegister treats any value length other than 4 as an 8-byte double and then reads with ReadInt64LittleEndian, which will throw for unexpected lengths. Since the API contract is 4 or 8 bytes, this should validate the input length and return false for anything else.
  src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/Context/X86Context.cs:232
• TryGetX87SlotOffset reads the StatusWord using context.Slice(offset) without validating that the buffer is large enough. If an undersized context span is passed, this will throw instead of returning false.

• Files reviewed: 74/74 changed files
• Comments generated: 0 new