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[cdac] Lazily read global string/object method table pointers #109093

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merged 2 commits into from
Oct 22, 2024
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[cdac] Lazily read global string/object method table pointers #109093

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66d4d28
[cdac] Lazily read global string/object method table pointers
elinor-fung Oct 22, 2024
8bedac5
Update src/native/managed/cdacreader/src/Legacy/SOSDacImpl.cs
elinor-fung Oct 22, 2024
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22 changes: 14 additions & 8 deletions src/native/managed/cdacreader/src/Legacy/SOSDacImpl.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -27,8 +27,11 @@ internal sealed unsafe partial class SOSDacImpl
ISOSDacInterface11, ISOSDacInterface12, ISOSDacInterface13, ISOSDacInterface14, ISOSDacInterface15
{
private readonly Target _target;
private readonly TargetPointer _stringMethodTable;
private readonly TargetPointer _objectMethodTable;

// When this class is created, the runtime may not have loaded the string and object method tables and set the global pointers.
// They should be set when actually requested via a DAC API, so we lazily read the global pointers.
private readonly Lazy<TargetPointer> _stringMethodTable;
private readonly Lazy<TargetPointer> _objectMethodTable;

private readonly ISOSDacInterface? _legacyImpl;
private readonly ISOSDacInterface2? _legacyImpl2;
Expand All @@ -52,8 +55,11 @@ internal sealed unsafe partial class SOSDacImpl
public SOSDacImpl(Target target, object? legacyObj)
{
_target = target;
_stringMethodTable = _target.ReadPointer(_target.ReadGlobalPointer(Constants.Globals.StringMethodTable));
_objectMethodTable = _target.ReadPointer(_target.ReadGlobalPointer(Constants.Globals.ObjectMethodTable));
_stringMethodTable = new Lazy<TargetPointer>(
() => _target.ReadPointer(_target.ReadGlobalPointer(Constants.Globals.StringMethodTable)));

_objectMethodTable = new Lazy<TargetPointer>(
() => _target.ReadPointer(_target.ReadGlobalPointer(Constants.Globals.ObjectMethodTable)));

// Get all the interfaces for delegating to the legacy DAC
if (legacyObj is not null)
Expand Down Expand Up @@ -619,14 +625,14 @@ int ISOSDacInterface.GetObjectData(ulong objAddr, DacpObjectData* data)
ulong numComponentsOffset = (ulong)_target.GetTypeInfo(DataType.Array).Fields[Data.Array.FieldNames.NumComponents].Offset;
data->Size += _target.Read<uint>(objAddr + numComponentsOffset) * data->dwComponentSize;
}
else if (mt == _stringMethodTable)
else if (mt == _stringMethodTable.Value)
{
data->ObjectType = DacpObjectType.OBJ_STRING;

// Update the size to include the string character components
data->Size += (uint)objectContract.GetStringValue(objAddr).Length * data->dwComponentSize;
}
else if (mt == _objectMethodTable)
else if (mt == _objectMethodTable.Value)
{
data->ObjectType = DacpObjectType.OBJ_OBJECT;
}
Expand Down Expand Up @@ -967,8 +973,8 @@ int ISOSDacInterface.GetUsefulGlobals(DacpUsefulGlobalsData* data)
{
data->ArrayMethodTable = _target.ReadPointer(
_target.ReadGlobalPointer(Constants.Globals.ObjectArrayMethodTable));
data->StringMethodTable = _stringMethodTable;
data->ObjectMethodTable = _objectMethodTable;
data->StringMethodTable = _stringMethodTable.Value;
data->ObjectMethodTable = _objectMethodTable.Value;
data->ExceptionMethodTable = _target.ReadPointer(
_target.ReadGlobalPointer(Constants.Globals.ExceptionMethodTable));
data->FreeMethodTable = _target.ReadPointer(
Expand Down
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