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[cDAC] Tolerate missing WKS card-table slot in reduced dumps #132938

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[cDAC] Tolerate missing WKS card-table slot in reduced dumps #132938

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5 changes: 4 additions & 1 deletion ...managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/GC/GCHeapWKS.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -17,7 +17,10 @@ public GCHeapWKS(Target target)
BackgroundMaxSavedAddr = target.ReadPointer(bgMaxPtr.Value);
AllocAllocated = target.ReadPointer(target.ReadGlobalPointer(Constants.Globals.GCHeapAllocAllocated));
EphemeralHeapSegment = target.ReadPointer(target.ReadGlobalPointer(Constants.Globals.GCHeapEphemeralHeapSegment));
CardTable = target.ReadPointer(target.ReadGlobalPointer(Constants.Globals.GCHeapCardTable));
TargetPointer cardTablePtr = target.ReadGlobalPointer(Constants.Globals.GCHeapCardTable);
CardTable = target.TryReadPointer(cardTablePtr, out TargetPointer cardTable)
? cardTable
: TargetPointer.Null;
FinalizeQueue = target.ReadPointer(target.ReadGlobalPointer(Constants.Globals.GCHeapFinalizeQueue));
GenerationTable = target.ReadGlobalPointer(Constants.Globals.GCHeapGenerationTable);

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3 changes: 2 additions & 1 deletion src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs
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Expand Up @@ -1640,7 +1640,8 @@ int ISOSDacInterface.GetGCHeapStaticData(DacpGcHeapDetails* details)

Debug.Assert(details->lowest_address == detailsLocal.lowest_address, $"cDAC: {details->lowest_address:x}, DAC: {detailsLocal.lowest_address:x}");
Debug.Assert(details->highest_address == detailsLocal.highest_address, $"cDAC: {details->highest_address:x}, DAC: {detailsLocal.highest_address:x}");
Debug.Assert(details->card_table == detailsLocal.card_table, $"cDAC: {details->card_table:x}, DAC: {detailsLocal.card_table:x}");
// Reduced dumps may omit the cDAC card-table slot while retaining the legacy VM mirror.
Debug.Assert(details->card_table == 0 || details->card_table == detailsLocal.card_table, $"cDAC: {details->card_table:x}, DAC: {detailsLocal.card_table:x}");
}
}
#endif
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72 changes: 72 additions & 0 deletions src/native/managed/cdac/tests/UnitTests/GCTests.cs
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Expand Up @@ -4,13 +4,62 @@
using System;
using System.Collections.Generic;
using Microsoft.Diagnostics.DataContractReader.Contracts;
using Microsoft.Diagnostics.DataContractReader.Legacy;
using Microsoft.Diagnostics.DataContractReader.TestInfrastructure;
using Xunit;

namespace Microsoft.Diagnostics.DataContractReader.Tests;

public class GCTests
{
private const ulong CardTableAddress = 0x1234_5000;

private static readonly MockGCBuilder.Generation[] s_cardTableGenerations =
[
new() { StartSegment = 0x1A00_0000, AllocationStart = 0x1A00_1000, AllocContextPointer = 0x1A00_2000, AllocContextLimit = 0x1A00_3000 },
new() { StartSegment = 0x1B00_0000, AllocationStart = 0x1B00_1000, AllocContextPointer = 0, AllocContextLimit = 0 },
new() { StartSegment = 0x1C00_0000, AllocationStart = 0x1C00_1000, AllocContextPointer = 0, AllocContextLimit = 0 },
new() { StartSegment = 0x1D00_0000, AllocationStart = 0x1D00_1000, AllocContextPointer = 0, AllocContextLimit = 0 },
];

[Theory]
[ClassData(typeof(MockTarget.StdArch))]
public void GetHeapData_ReadableCardTableSlot_ReturnsCardTable(MockTarget.Architecture arch)
{
Target target = CreateWksTargetWithCardTable(arch, cardTableSlotReadable: true);

GCHeapData heapData = target.Contracts.GC.GetHeapData();

Assert.Equal(CardTableAddress, (ulong)heapData.CardTable);
}

[Theory]
[ClassData(typeof(MockTarget.StdArch))]
public void GetHeapData_UnreadableCardTableSlot_ReturnsHeapDataWithNullCardTable(MockTarget.Architecture arch)
{
Target target = CreateWksTargetWithCardTable(arch, cardTableSlotReadable: false);

GCHeapData heapData = target.Contracts.GC.GetHeapData();

Assert.Equal(TargetPointer.Null, heapData.CardTable);
Assert.Equal(s_cardTableGenerations.Length, heapData.GenerationTable.Count);
Assert.Equal(s_cardTableGenerations[0].StartSegment, (ulong)heapData.GenerationTable[0].StartSegment);
}

[Theory]
[ClassData(typeof(MockTarget.StdArch))]
public unsafe void GetGCHeapStaticData_UnreadableCardTableSlot_ReturnsHeapDataWithNullCardTable(MockTarget.Architecture arch)
{
Target target = CreateWksTargetWithCardTable(arch, cardTableSlotReadable: false);

ISOSDacInterface sosDac = new SOSDacImpl(target, legacyObj: null, new());
DacpGcHeapDetails details = default;

Assert.Equal(0, sosDac.GetGCHeapStaticData(&details));
Assert.Equal(0UL, details.card_table.Value);
Assert.Equal(s_cardTableGenerations[0].StartSegment, details.generation_table[0].start_segment.Value);
}

[Theory]
[ClassData(typeof(MockTarget.StdArch))]
public void GetHeapData_ReturnsCorrectGenerationTable(MockTarget.Architecture arch)
Expand Down Expand Up @@ -120,6 +169,29 @@ public void GetHeapData_WithFiveGenerations(MockTarget.Architecture arch)

private sealed record CapturedSegment(ulong Start, ulong End, GCSegmentClassification Generation);

private static Target CreateWksTargetWithCardTable(MockTarget.Architecture arch, bool cardTableSlotReadable)
{
ulong cardTableGlobalAddress = 0;
var builder = new TestPlaceholderTarget.Builder(arch);
builder.AddGCHeapWks(gc =>
{
gc.Generations = s_cardTableGenerations;
gc.ConfigureMemory = gcBuilder =>
{
cardTableGlobalAddress = gcBuilder.CardTableGlobalAddress;
gcBuilder.WritePointerGlobal(cardTableGlobalAddress, CardTableAddress);
};
});

if (!cardTableSlotReadable)
{
TestPlaceholderTarget.ReadFromTargetDelegate reader = builder.MemoryBuilder.GetMemoryContext().ReadFromTarget;
builder.UseReader((address, buffer) => address == cardTableGlobalAddress ? -1 : reader(address, buffer));
}

return builder.Build();
}

private static MockGCBuilder.Generation[] MakeGenerations(ulong gen0Seg, ulong gen0Start, ulong gen1Seg, ulong gen1Start, ulong gen2Seg, ulong lohSeg, ulong pohSeg)
=>
[
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