[cDAC] X86 support HijackFrame (#116829)

* x86 hijackframe support

Author: max-charlamb

docs/design/datacontracts/StackWalk.md

@@ -56,7 +56,7 @@ This contract depends on the following descriptors:
 | `HijackFrame` | `HijackArgsPtr` | Pointer to the Frame's stored HijackArgs |
 | `HijackArgs` (amd64) | `CalleeSavedRegisters` | CalleeSavedRegisters data structure |
 | `HijackArgs` (amd64 Windows) | `Rsp` | Saved stack pointer |
-| `HijackArgs` (arm64) | For each register `r` saved in HijackArgs, `r` | Register names associated with stored register values |
+| `HijackArgs` (arm64/x86) | For each register `r` saved in HijackArgs, `r` | Register names associated with stored register values |
 | `CalleeSavedRegisters` | For each callee saved register `r`, `r` | Register names associated with stored register values |
 | `TailCallFrame` (x86 Windows) | `CalleeSavedRegisters` | CalleeSavedRegisters data structure |
 | `TailCallFrame` (x86 Windows) | `ReturnAddress` | Frame's stored instruction pointer |

src/coreclr/debug/runtimeinfo/datadescriptor.h

@@ -777,6 +777,17 @@ CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, X28, offsetof(HijackArgs, X28))
 CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Fp, offsetof(HijackArgs, X29))
 CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Lr, offsetof(HijackArgs, Lr))
 
+#elif defined(TARGET_X86)
+
+CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Edi, offsetof(HijackArgs, Edi))
+CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Esi, offsetof(HijackArgs, Esi))
+CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Ebx, offsetof(HijackArgs, Ebx))
+CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Edx, offsetof(HijackArgs, Edx))
+CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Ecx, offsetof(HijackArgs, Ecx))
+CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Eax, offsetof(HijackArgs, Eax))
+CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Ebp, offsetof(HijackArgs, Ebp))
+CDAC_TYPE_FIELD(HijackArgs, /*pointer*/, Eip, offsetof(HijackArgs, Eip))
+
 #endif // Platform switch
 CDAC_TYPE_END(HijackArgs)
 #endif // FEATURE_HIJACK

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/FrameHandling/ARM64FrameHandler.cs

@@ -28,7 +28,7 @@ void IPlatformFrameHandler.HandleHijackFrame(HijackFrame frame)
 
         _holder.InstructionPointer = frame.ReturnAddress;
 
-        // The stack pointer is the address immediately following HijacksArgs
+        // The stack pointer is the address immediately following HijackArgs
         uint hijackArgsSize = _target.GetTypeInfo(DataType.HijackArgs).Size ?? throw new InvalidOperationException("HijackArgs size is not set");
         Debug.Assert(hijackArgsSize % 8 == 0, "HijackArgs contains register values and should be a multiple of 8");
         // The stack must be multiple of 16. So if hijackArgsSize is not multiple of 16 then there must be padding of 8 bytes

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/StackWalk/FrameHandling/X86FrameHandler.cs

@@ -23,8 +23,13 @@ public void HandleFaultingExceptionFrame(FaultingExceptionFrame frame)
 
     public void HandleHijackFrame(HijackFrame frame)
     {
-        // TODO(cdacX86): Implement handling for HijackFrame
-        throw new NotImplementedException();
+        HijackArgsX86 args = _target.ProcessedData.GetOrAdd<HijackArgsX86>(frame.HijackArgsPtr);
+
+        // The stack pointer is the address immediately following HijackArgs
+        uint hijackArgsSize = _target.GetTypeInfo(DataType.HijackArgs).Size ?? throw new InvalidOperationException("HijackArgs size is not set");
+        _context.Context.Esp = (uint)frame.HijackArgsPtr + hijackArgsSize;
+
+        UpdateFromRegisterDict(args.Registers);
     }
 
     public override void HandleTailCallFrame(TailCallFrame frame)

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/Frames/HijackArgsX86.cs

@@ -0,0 +1,27 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Collections.Generic;
+
+namespace Microsoft.Diagnostics.DataContractReader.Data;
+
+internal class HijackArgsX86 : IData<HijackArgsX86>
+{
+    static HijackArgsX86 IData<HijackArgsX86>.Create(Target target, TargetPointer address)
+        => new HijackArgsX86(target, address);
+
+    public HijackArgsX86(Target target, TargetPointer address)
+    {
+        Target.TypeInfo type = target.GetTypeInfo(DataType.HijackArgs);
+
+        Dictionary<string, TargetNUInt> registers = new Dictionary<string, TargetNUInt>(type.Fields.Count);
+        foreach ((string name, Target.FieldInfo field) in type.Fields)
+        {
+            TargetNUInt value = target.ReadNUInt(address + (ulong)field.Offset);
+            registers.Add(name, value);
+        }
+        Registers = registers;
+    }
+
+    public IReadOnlyDictionary<string, TargetNUInt> Registers { get; }
+}