Fix field accessor for RVA field

src/coreclr/vm/reflectioninvocation.cpp

@@ -1246,14 +1246,16 @@ FCIMPL1(void*, RuntimeFieldHandle::GetStaticFieldAddress, ReflectFieldObject *pF
     // IsFastPathSupported needs to checked before calling this method.
     _ASSERTE(IsFastPathSupportedHelper(pFieldDesc));
 
-    PTR_BYTE base = 0;
-    if (!pFieldDesc->IsRVA())
+    if (pFieldDesc->IsRVA())
     {
-        // For RVA the base is ignored and offset is used.
-        base = pFieldDesc->GetBase();
+        Module* pModule = pFieldDesc->GetModule();
+        return pModule->GetRvaField(pFieldDesc->GetOffset());
+    }
+    else
+    {
+        PTR_BYTE base = pFieldDesc->GetBase();
+        return PTR_VOID(base + pFieldDesc->GetOffset());
     }
-
-    return PTR_VOID(base + pFieldDesc->GetOffset());
 }
 FCIMPLEND
 

src/libraries/System.Private.CoreLib/src/System/Reflection/FieldAccessor.cs

@@ -48,7 +48,12 @@ private void Initialize()
                 {
                     _addressOrOffset = RuntimeFieldHandle.GetStaticFieldAddress(_fieldInfo);
 
-                    if (fieldType.IsValueType)
+                    if ((_fieldInfo.Attributes & FieldAttributes.HasFieldRVA) != 0)
+                    {
+                        _methodTable = (MethodTable*)fieldType.TypeHandle.Value;
+                        _fieldAccessType = FieldAccessorType.StaticValueType;
+                    }
+                    else if (fieldType.IsValueType)
                     {
                         if (fieldType.IsEnum)
                         {

src/libraries/System.Runtime/tests/System.Reflection.Tests/FieldInfoTests.cs

@@ -5,6 +5,8 @@
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
 using Xunit;
 
 #pragma warning disable 0414
@@ -121,6 +123,30 @@ public void GetValueWithFunctionPointers(Type type, string name, object obj, obj
             Assert.Equal(expected, fieldInfo.GetValue(obj));
         }
 
+        // RVA field reflection is not supported in NativeAot
+        [ConditionalFact(typeof(PlatformDetection), nameof(PlatformDetection.IsNotNativeAot))]
+        public void GetValueFromRvaField()
+        {
+            byte[] valueArray = new byte[] { 1, 2, 3, 4, 5 };
+
+            // Roslyn uses SHA256 of raw data as data field name
+            FieldInfo fieldInfo = GetField(
+                typeof(FieldInfoTests).Assembly.GetType("<PrivateImplementationDetails>"),
+                "74F81FE167D99B4CB41D6D0CCDA82278CAEE9F3E2F25D5E5A3936FF3DCEC60D0");
+            Assert.NotNull(fieldInfo);
+            Assert.True(fieldInfo.IsStatic);
+            Assert.True((fieldInfo.Attributes & FieldAttributes.HasFieldRVA) != 0);
+
+            for (int i = 0; i < 5; i++)
+            {
+                // FieldAccessor uses slow path until the class is initialized.
+                // Make sure subsequent invocations also succeed.
+
+                object value = fieldInfo.GetValue(null);
+                Assert.Equal(valueArray, MemoryMarshal.CreateReadOnlySpan(ref Unsafe.As<object, RawData>(ref value).Data, valueArray.Length));
+            }
+        }
+
         [Fact]
         public void GetAndSetValueTypeFromStatic()
         {
@@ -839,5 +865,10 @@ public static class SettingsForMyTypeThatThrowsInClassInitializer
         {
             public static bool s_shouldThrow = true;
         }
+
+        private class RawData
+        {
+            public byte Data;
+        }
     }
 }