Add source info to perfmap/jitdump by a74nh · Pull Request #126836 · dotnet/runtime

a74nh · 2026-04-13T14:09:12Z

Add PerfMapSymbolReader and GetInfoForMethod in System.Private.CoreLib to read PDB/embedded PDB sequence points for perfmap/jitdump.
Retarget the native delegate creation to System.Diagnostics.StackTrace from SOS.NETCore
Add JIT_CODE_DEBUG_INFO records using managed debug info, gated behind config variable

* Add PerfMapSymbolReader and GetInfoForMethod in System.Private.CoreLib to read PDB/embedded PDB sequence points for perfmap/jitdump. * Retarget the native delegate creation to System.Diagnostics.StackTrace from SOS.NETCore * Add JIT_CODE_DEBUG_INFO records using managed debug info, gated behind config variable

dotnet-policy-service · 2026-04-13T14:10:26Z

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Copilot

Pull request overview

This PR adds source/line debug-info support to perfmap/jitdump by introducing a managed PDB sequence-point reader and wiring CoreCLR’s perfmap/jitdump pipeline to emit JIT_CODE_DEBUG_INFO records (gated by a new config knob).

Changes:

Add PerfMapSymbolReader (System.Diagnostics.StackTrace) to read sequence points from associated/embedded Portable PDBs for a given method token.
Retarget native delegate creation to System.Diagnostics.StackTrace.GetInfoForMethod in System.Private.CoreLib and add re-entrancy guards.
Extend jitdump logging to optionally emit JIT_CODE_DEBUG_INFO records and plumb debug-info payloads from perfmap.cpp into PAL_PerfJitDump_LogMethod.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
src/libraries/System.Diagnostics.StackTrace/src/System/Diagnostics/PerfMapSymbolReader.cs	New managed helper to read sequence points from associated/embedded PDBs into a native buffer.
src/libraries/System.Diagnostics.StackTrace/src/System.Diagnostics.StackTrace.csproj	Include new source file in the StackTrace library build.
src/libraries/System.Diagnostics.StackTrace/src/ILLink/ILLink.Descriptors.LibraryBuild.xml	Preserve `PerfMapSymbolReader` for trimming scenarios.
src/coreclr/vm/perfmap.h	Add `s_EmitDebugInfo` toggle for debug-info emission.
src/coreclr/vm/perfmap.cpp	Build/emit serialized jitdump debug-info payload from managed sequence points when enabled.
src/coreclr/vm/gdbjithelpers.h	Update debug-info delegate signature to return `int` and take `MethodDebugInfo*`.
src/coreclr/vm/gdbjit.cpp	Add re-entrancy guard and update delegate invocation for new signature.
src/coreclr/pal/src/misc/perfjitdump.cpp	Add `JIT_CODE_DEBUG_INFO` record support and extend logging API to accept debug/unwind payloads + sizes.
src/coreclr/pal/inc/pal.h	Update `PAL_PerfJitDump_LogMethod` signature to include debug/unwind payload sizes and const pointers.
src/coreclr/inc/clrconfigvalues.h	Add `PerfMapEmitDebugInfo` config knob.
src/coreclr/dlls/mscoree/exports.cpp	Create the native delegate against `System.Private.CoreLib` / `System.Diagnostics.StackTrace.GetInfoForMethod`.

src/coreclr/vm/perfmap.cpp

src/libraries/System.Diagnostics.StackTrace/src/System/Diagnostics/PerfMapSymbolReader.cs

+        /// <summary>
+        /// Populate a native buffer with sequence points for the specified method token using the assembly's associated or embedded PDB.
+        /// </summary>
+        /// <returns>true if at least one sequence point was written; otherwise false.</returns>
+        internal static bool GetInfoForMethod([MarshalAs(UnmanagedType.LPUTF8Str)] string assemblyPath, int methodToken, IntPtr points, int size)
+        {
+            if (string.IsNullOrEmpty(assemblyPath) || points == IntPtr.Zero || size <= 0)
+            {
+                return false;
+            }


a74nh · 2026-04-13T14:22:14Z

This PR is useful for any tool or developer that uses linux perf to analyse .NET applications. Specifically, support is being added for use by Arm Performix, with the aim of using this to help migrate users.

Example output of perf annotate showing the line numbers from an example C# that was run through perf:

This PR was entirely written by codex. I've spent some time testing and reviewing the code. It looks sensible and works for me, however I don't claim to be familiar with some of these areas of CoreCLR.

@JulieLeeMSFT @dhartglassMSFT

a74nh · 2026-04-13T15:43:18Z

Still need to add tests. But, taking this out of draft to get some comments to see if this is in the right direction

Copilot

Pull request overview

This PR adds managed symbol-reading support to enrich perfmap/jitdump output with source/line information by reading Portable PDB sequence points, and wires the runtime to use this new managed helper when emitting perfmap/jitdump data.

Changes:

Add PerfMapSymbolReader (System.Diagnostics.StackTrace) and a CoreLib StackTrace.GetInfoForMethod unmanaged callback to retrieve sequence points from associated/embedded Portable PDBs.
Extend perfmap/jitdump plumbing to optionally emit JIT_CODE_DEBUG_INFO records (gated by PerfMapEmitDebugInfo) and update PAL jitdump logging to accept a debug-info payload.
Retarget the runtime delegate creation from SOS to System.Private.CoreLib / System.Diagnostics.StackTrace for debug-info retrieval.

Reviewed changes

Copilot reviewed 12 out of 12 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/libraries/System.Diagnostics.StackTrace/src/System/Diagnostics/PerfMapSymbolReader.cs	New managed helper to read Portable PDB sequence points and fill a native buffer.
src/libraries/System.Diagnostics.StackTrace/src/System.Diagnostics.StackTrace.csproj	Includes the new `PerfMapSymbolReader.cs` in the build.
src/libraries/System.Diagnostics.StackTrace/src/ILLink/ILLink.Descriptors.LibraryBuild.xml	Preserves `PerfMapSymbolReader` for trimming scenarios.
src/coreclr/vm/perfmap.h	Adds `s_EmitDebugInfo` configuration flag.
src/coreclr/vm/perfmap.cpp	Emits optional jitdump debug-info payload and passes it to PAL jitdump logging.
src/coreclr/vm/gdbjithelpers.h	Updates the managed debug-info delegate signature to use a pointer and `int` return.
src/coreclr/vm/gdbjit.cpp	Adds re-entrancy guard and updates delegate invocation to new signature.
src/coreclr/System.Private.CoreLib/src/System/Diagnostics/StackTrace.CoreCLR.cs	Adds unmanaged callback (`GetInfoForMethod`) and UnsafeAccessor bridge into System.Diagnostics.StackTrace.
src/coreclr/pal/src/misc/perfjitdump.cpp	Adds `JIT_CODE_DEBUG_INFO` record support and extends `LogMethod` parameters.
src/coreclr/pal/inc/pal.h	Updates `PAL_PerfJitDump_LogMethod` signature to include debug/unwind buffers + sizes.
src/coreclr/inc/clrconfigvalues.h	Adds `PerfMapEmitDebugInfo` config value.
src/coreclr/dlls/mscoree/exports.cpp	Retargets delegate creation to `System.Diagnostics.StackTrace.GetInfoForMethod` and enables it for FEATURE_PERFMAP too.

src/coreclr/System.Private.CoreLib/src/System/Diagnostics/StackTrace.CoreCLR.cs

+            {
+                return 0;
+            }
+


src/coreclr/System.Private.CoreLib/src/System/Diagnostics/StackTrace.CoreCLR.cs

+            if (assemblyPath == null || methodDebugInfo == null || methodDebugInfo->points == null || methodDebugInfo->size <= 0)
+            {
+                return 0;
+            }
+
+            string? assemblyPathString = Marshal.PtrToStringUTF8((IntPtr)assemblyPath);
+            if (string.IsNullOrEmpty(assemblyPathString))
+            {
+                return 0;
+            }
+
+            return GetPerfMapInfoForMethodFromReader(null, assemblyPathString, unchecked((int)methodToken), (IntPtr)methodDebugInfo->points, methodDebugInfo->size) ? 1 : 0;


src/libraries/System.Diagnostics.StackTrace/src/System/Diagnostics/PerfMapSymbolReader.cs

+                MetadataReader reader = provider.GetMetadataReader();
+                Handle handle = MetadataTokens.Handle(methodToken);
+                if (handle.IsNil || handle.Kind != HandleKind.MethodDefinition)
+                {
+                    return false;
+                }
+
+                MethodDebugInformationHandle methodDebugHandle = ((MethodDefinitionHandle)handle).ToDebugInformationHandle();
+                MethodDebugInformation methodInfo = reader.GetMethodDebugInformation(methodDebugHandle);
+                if (methodInfo.SequencePointsBlob.IsNil)
+                {
+                    return false;
+                }
+
+                int count = 0;
+                foreach (SequencePoint _ in methodInfo.GetSequencePoints())
+                {
+                    count++;
+                }
+
+                if (count == 0)
+                {
+                    return false;
+                }
+
+                SequencePointInfoNative* nativePoints = (SequencePointInfoNative*)points;
+                int writeIndex = 0;
+                foreach (SequencePoint point in methodInfo.GetSequencePoints())
+                {
+                    if (writeIndex >= size)
+                    {
+                        break;
+                    }
+
+                    string? documentName = null;
+                    if (!point.Document.IsNil)
+                    {
+                        documentName = reader.GetString(reader.GetDocument(point.Document).Name);
+                    }
+
+                    nativePoints[writeIndex].ilOffset = point.Offset;
+                    nativePoints[writeIndex].lineNumber = point.StartLine == SequencePoint.HiddenLine ? HiddenLineNumber : point.StartLine;
+                    nativePoints[writeIndex].fileName = documentName is null ? null : (char*)Marshal.StringToCoTaskMemUni(documentName);
+                    writeIndex++;
+                }
+
+                for (int i = writeIndex; i < size; i++)
+                {
+                    nativePoints[i].ilOffset = int.MaxValue;
+                    nativePoints[i].lineNumber = HiddenLineNumber;
+                    nativePoints[i].fileName = null;
+                }
+
+                return writeIndex > 0;


src/coreclr/vm/gdbjit.cpp

    MethodDebugInfo methodDebugInfo(numMap, locals.countVars);

-    if (getInfoForMethodDelegate(szModName, methodDescPtr->GetMemberDef(), methodDebugInfo) == FALSE)
+    t_gdbJitDebugInfoCallbackDepth = 1;
+    if (getInfoForMethodDelegate(szModName, methodDescPtr->GetMemberDef(), &methodDebugInfo) == 0)
+    {
+        t_gdbJitDebugInfoCallbackDepth = 0;
        return E_FAIL;
+    }
+    t_gdbJitDebugInfoCallbackDepth = 0;


src/coreclr/vm/perfmap.cpp

+        for (ULONG32 nativeMapIndex = 0; nativeMapIndex < nativeMapCount; nativeMapIndex++)
+        {
+            const ULONG32 ilOffset = nativeMap[nativeMapIndex].ilOffset;
+
+            if ((ilOffset == (ULONG32)ICorDebugInfo::NO_MAPPING) ||
+                (ilOffset == (ULONG32)ICorDebugInfo::PROLOG) ||
+                (ilOffset == (ULONG32)ICorDebugInfo::EPILOG))
+            {
+                continue;
+            }
+
+            int sequencePointIndex = 0;
+            for (; sequencePointIndex < methodDebugInfo.size; sequencePointIndex++)
+            {
+                if ((ULONG32)methodDebugInfo.points[sequencePointIndex].ilOffset >= ilOffset)
+                {
+                    if (((ULONG32)methodDebugInfo.points[sequencePointIndex].ilOffset > ilOffset) && (sequencePointIndex > 0))
+                    {
+                        sequencePointIndex--;
+                    }
+
+                    break;
+                }
+            }


JulieLeeMSFT · 2026-04-13T17:12:32Z

@noahfalk, @brianrob, @steveisok, PTAL if it aligns with our diagnostics story. This change is related to the Performix tool supporting source annotation.

Copilot AI review requested due to automatic review settings April 13, 2026 14:09

github-actions bot added the area-VM-coreclr label Apr 13, 2026

dotnet-policy-service bot added linkable-framework Issues associated with delivering a linker friendly framework community-contribution Indicates that the PR has been added by a community member labels Apr 13, 2026

Copilot started reviewing on behalf of a74nh April 13, 2026 14:10 View session

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a74nh added 2 commits April 13, 2026 15:23

array safe allocation for IL native map data

1c8baa5

fill the unused slots with a sentinel ilOffset

260baa0

a74nh marked this pull request as ready for review April 13, 2026 15:43

Copilot AI review requested due to automatic review settings April 13, 2026 15:43

Copilot started reviewing on behalf of a74nh April 13, 2026 15:44 View session

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JulieLeeMSFT requested review from brianrob, noahfalk and steveisok April 13, 2026 17:10

JulieLeeMSFT assigned a74nh and noahfalk Apr 13, 2026

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Add source info to perfmap/jitdump#126836

Add source info to perfmap/jitdump#126836
a74nh wants to merge 3 commits intodotnet:mainfrom
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