[cDAC] Implement SetJITCompilerFlags for cDAC by barosiak · Pull Request #126595 · dotnet/runtime

barosiak · 2026-04-07T01:20:22Z

Summary

Implement SetJITCompilerFlags on IXCLRDataModule2 in the cDAC.

Changes

ClrDataModule.cs - SetJITCompilerFlags implementation
ILoader.cs / Loader_1.cs - added GetDebuggerInfoBits and SetDebuggerInfoBits contract methods with direct target memory read/write
IXCLRData.cs - added DebuggerAssemblyControlFlags enum mirroring cordbpriv.h
Tests - new tests covering get/set/flag-preservation

Copilot

Pull request overview

Implements IXCLRDataModule2.SetJITCompilerFlags for the managed cDAC by wiring it to the Loader contract’s module transient-flag debugger bits, adding the necessary contract surface and tests to validate read/write behavior.

Changes:

Implement IXCLRDataModule2.SetJITCompilerFlags in ClrDataModule by updating module debugger control bits via ILoader.
Extend ILoader/Loader_1 with GetDebuggerInfoBits and SetDebuggerInfoBits, and document the new contract surface/constants.
Update cDAC test infrastructure to support target-memory writes and add Loader tests for debugger-bit get/set and flag preservation.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataModule.cs	Implements `SetJITCompilerFlags` using Loader debugger-info bits.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/IXCLRData.cs	Adds managed `DebuggerAssemblyControlFlags` enum mirroring `cordbpriv.h`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/ILoader.cs	Adds `GetDebuggerInfoBits` / `SetDebuggerInfoBits` to the Loader contract.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs	Implements debugger-info bit get/set by reading/writing `Module::Flags`.
src/native/managed/cdac/tests/TestPlaceholderTarget.cs	Adds write-capable target support for tests.
src/native/managed/cdac/tests/MockDescriptors/MockDescriptors.Loader.cs	Allows initializing module transient flags in mocks.
src/native/managed/cdac/tests/LoaderTests.cs	Adds new tests for debugger-info bit behavior.
docs/design/datacontracts/Loader.md	Documents new Loader contract methods and constants.
src/coreclr/vm/ceeload.h	Notes cDAC Loader contract dependency on debugger-info mask/shift constants.
src/coreclr/inc/cordbpriv.h	Adds explicit comment that cDAC depends on flag values.

src/native/managed/cdac/tests/TestPlaceholderTarget.cs

...native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot

Pull request overview

Copilot reviewed 10 out of 10 changed files in this pull request and generated 2 comments.

Copilot · 2026-04-07T17:59:14Z

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataModule.cs

+        int hr = HResults.S_OK;
+        try
+        {
+            if ((flags != CORDEBUG_JIT_DEFAULT) && (flags != CORDEBUG_JIT_DISABLE_OPTIMIZATION))
+                throw new ArgumentException();
+


IXCLRDataModule2.SetJITCompilerFlags is now implemented, but there doesn’t appear to be any unit/integration test that exercises this COM entrypoint (argument validation and the expected updates to Module::m_dwTransientFlags via Loader.Get/SetDebuggerInfoBits). Adding a focused test that constructs a ClrDataModule over a mock Module, calls SetJITCompilerFlags with both supported values (and an invalid value), and then asserts the shifted debugger bits in target memory would help prevent regressions.

Suggested change

int hr = HResults.S_OK;

try

{

if ((flags != CORDEBUG_JIT_DEFAULT) && (flags != CORDEBUG_JIT_DISABLE_OPTIMIZATION))

throw new ArgumentException();

if ((flags != CORDEBUG_JIT_DEFAULT) && (flags != CORDEBUG_JIT_DISABLE_OPTIMIZATION))

{

return HResults.E_INVALIDARG;

}

int hr = HResults.S_OK;

try

{

Copilot · 2026-04-07T17:59:14Z

docs/design/datacontracts/Loader.md

+void SetDebuggerInfoBits(ModuleHandle handle, uint newBits)
+{
+    uint currentFlags = // read Module::Flags (uint32) at handle.Address + Flags offset
+    uint updated = (currentFlags & ~DebuggerInfoMask) | (newBits << DebuggerInfoShift);


The SetDebuggerInfoBits pseudocode writes (newBits << DebuggerInfoShift) without masking to the available bit-range, but the contract implementation masks newBits to (DebuggerInfoMask >> DebuggerInfoShift) before shifting. Please update the documentation snippet to reflect the masking behavior so callers don’t assume higher bits will be preserved/written.

Suggested change

uint updated = (currentFlags & ~DebuggerInfoMask) | (newBits << DebuggerInfoShift);

uint updated = (currentFlags & ~DebuggerInfoMask) | ((newBits & (DebuggerInfoMask >> DebuggerInfoShift)) << DebuggerInfoShift);

noahfalk · 2026-04-08T06:31:55Z

docs/design/datacontracts/Loader.md

 IReadOnlyDictionary<string, TargetPointer> GetLoaderAllocatorHeaps(TargetPointer loaderAllocatorPointer);
+
+uint GetDebuggerInfoBits(ModuleHandle handle);
+void SetDebuggerInfoBits(ModuleHandle handle, uint newBits);


Rather than expose all the bits I'd suggest only exposing DACF_ALLOW_JIT_OPTS and DACF_ENC_ENABLED for now. Later I think we might need to add read-only for DACF_IGNORE_PDBS as part of DBI ENC support.

DACF_USER_OVERRIDE doesn't look like it serves any purpose and could be removed from the runtime. The one place I see in the runtime that reads it is unreachable.

noahfalk · 2026-04-08T06:35:52Z

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/IXCLRData.cs

 }

+[Flags]
+public enum DebuggerAssemblyControlFlags : uint


I'd treat this enum as part of the contract (document it in the markdown, define it in DataContractReader, and use it as the input/output type for the Get/SetDebuggerBits functions).

max-charlamb · 2026-04-08T16:48:57Z

...native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs

+        Target.TypeInfo type = _target.GetTypeInfo(DataType.Module);
+        ulong flagsAddr = handle.Address + (ulong)type.Fields[nameof(Data.Module.Flags)].Offset;
+        uint flags = _target.Read<uint>(flagsAddr);


Can use Data.Module.Flags to get this value.

max-charlamb · 2026-04-08T16:50:40Z

...native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs

+        Target.TypeInfo type = _target.GetTypeInfo(DataType.Module);
+        ulong flagsAddr = handle.Address + (ulong)type.Fields[nameof(Data.Module.Flags)].Offset;
+        uint currentFlags = _target.Read<uint>(flagsAddr);
+        uint debuggerInfoBitsMask = DebuggerInfoMask >> DebuggerInfoShift;
+        uint updated = (currentFlags & ~DebuggerInfoMask) | ((newBits & debuggerInfoBitsMask) << DebuggerInfoShift);
+        _target.Write<uint>(flagsAddr, updated);


We should make sure to update the in memory Data.Module class. Otherwise anyone else that looks at the Module.Flags field will get outdated data (IData classes are cached). Not sure if we have an existing pattern for this, but I wouldn't be opposed to adding support for writing back in the Module class directly.

rcj1 · 2026-04-10T03:19:44Z

src/coreclr/inc/cordbpriv.h

    DACF_ENC_ENABLED                = 0x08,
    DACF_IGNORE_PDBS                = 0x20,
-    DACF_CONTROL_FLAGS_MASK         = 0x2F,
+    DACF_CONTROL_FLAGS_MASK         = 0x2E,


unintentional?

rcj1 · 2026-04-10T03:40:22Z

...native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs

+        }
+
+        Target.TypeInfo type = _target.GetTypeInfo(DataType.Module);
+        ulong flagsAddr = handle.Address + (ulong)type.Fields[nameof(Data.Module.Flags)].Offset;


belongs in Module IData

rcj1 · 2026-04-10T14:44:26Z

docs/design/datacontracts/Loader.md

 | `MaxWebcilSections` | ushort | Maximum number of COFF sections supported in a Webcil image (must stay in sync with native `WEBCIL_MAX_SECTIONS`) | `16` |
+| `DebuggerInfoMask` | uint | Mask for the debugger info bits within the Module's transient flags | `0x0000Fc00` |
+| `DebuggerInfoShift` | int | Bit shift for the debugger info bits within the Module's transient flags | `10` |
+| `IS_JIT_OPTIMIZATION_DISABLED` | uint | Cached flag: JIT optimizations are disabled | `0x00000002` |


These four that are on the module flags belong in the module flags enum

Copilot

Pull request overview

Copilot reviewed 293 out of 664 changed files in this pull request and generated 6 comments.

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ClrDataModule.cs

...native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs

+        Data.Module module = _target.ProcessedData.GetOrAdd<Data.Module>(handle.Address);
+        uint currentFlags = module.Flags;
+        uint debuggerInfoBitsMask = DebuggerInfoMask >> DebuggerInfoShift;
+        uint updatedFlags = (currentFlags & ~DebuggerInfoMask) | (((uint)newBits & debuggerInfoBitsMask) << DebuggerInfoShift);


...native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/Loader_1.cs

+        if ((updatedFlags & IS_ENC_CAPABLE) != 0)
+        {
+            TargetPointer configPtr = _target.ReadGlobalPointer(Constants.Globals.EEConfig);
+            Data.EEConfig config = _target.ProcessedData.GetOrAdd<Data.EEConfig>(configPtr);
+            ClrModifiableAssemblies modifiableAssemblies = (ClrModifiableAssemblies)config.ModifiableAssemblies;
+
+            if (modifiableAssemblies != ClrModifiableAssemblies.None)
+            {
+                bool encRequested = (newBits & DebuggerAssemblyControlFlags.DACF_ENC_ENABLED) != 0;
+                bool jitOptsDisabledForEnc = (updatedFlags & IS_JIT_OPTIMIZATION_DISABLED) != 0;
+                bool setEnC = encRequested || (modifiableAssemblies == ClrModifiableAssemblies.Debug && jitOptsDisabledForEnc);
+
+                if (setEnC)
+                    updatedFlags |= IS_EDIT_AND_CONTINUE;
+            }
+        }


...tive/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/ILoader.cs

+[Flags]
+public enum DebuggerAssemblyControlFlags : uint
+{
+    DACF_NONE = 0x00,
+    DACF_ALLOW_JIT_OPTS = 0x02,
+    DACF_ENC_ENABLED = 0x08,
+    DACF_CONTROL_FLAGS_MASK = 0x2E,
+}


docs/design/datacontracts/Loader.md

+    DACF_ALLOW_JIT_OPTS = 0x02,
+    DACF_ENC_ENABLED = 0x08,


src/native/managed/cdac/tests/TestPlaceholderTarget.cs

+        if (_dataWriter(address, buffer) < 0)
+            throw new InvalidOperationException($"Failed to write {buffer.Length} bytes at 0x{address:x8}.");


Implement SetJITCompilerFlags for cDAC

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barosiak requested review from max-charlamb and rcj1 April 7, 2026 01:20

barosiak self-assigned this Apr 7, 2026

Copilot AI review requested due to automatic review settings April 7, 2026 01:20

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Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Copilot AI review requested due to automatic review settings April 7, 2026 17:53

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max-charlamb reviewed Apr 8, 2026

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Address pr comments, add EnC logic, simplify flags

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rcj1 reviewed Apr 10, 2026

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Copilot AI review requested due to automatic review settings April 10, 2026 21:53

barosiak requested review from BrzVlad, MichalStrehovsky, akoeplinger, janvorli, kg, maraf, sbomer, steveisok, thaystg and vitek-karas as code owners April 10, 2026 21:53

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Merge branch 'main' into barosiak/SetJITCompilerFlags

d0c1fe4

barosiak force-pushed the barosiak/SetJITCompilerFlags branch from f37b5e7 to d0c1fe4 Compare April 10, 2026 22:37

build-analysis bot mentioned this pull request Apr 11, 2026

System.Net.NameResolution.Tests DNS failures: Name or service not known #126641

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	uint updated = (currentFlags & ~DebuggerInfoMask) \| (newBits << DebuggerInfoShift);
	uint updated = (currentFlags & ~DebuggerInfoMask) \| ((newBits & (DebuggerInfoMask >> DebuggerInfoShift)) << DebuggerInfoShift);

		if (_dataWriter(address, buffer) < 0)
		throw new InvalidOperationException($"Failed to write {buffer.Length} bytes at 0x{address:x8}.");

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barosiak commented Apr 7, 2026

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