[release/6.0-rc1] [hot_reload] Don't look at delta method table rows (#…

…57799)

* Add test case

Call a method for the first time after an update has been applied to it.

This will check that the interpreter or JIT does not have to rely on cached
information from the baseline (about the method signature, for example) and
that it can compute it from the delta.

* [hot_reload] Don't look at delta method table rows

The issue is that the ParamList column in EnC deltas is a "suppressed column"
that has the value 0.  So when a method is updated if we use the value
directly, we will break, for example - `mono_metadata_get_param_attrs` which
expects a non-zero index in that column.

CoreCLR solves this by having a set of suppressed columns that are never
updated by deltas.  (CoreCLR's model is to directly mutate the tables of the
baseline image).  In Mono we can eventually do the same thing by writing the
value from the previous generation into the current delta's row.  But right now
since we don't allow parameter modifications, and the only column on a Method
table that we allow to be modified is the RVA - which we look up specially - we
can just always return the baseline image row for the method table.

Fixes #57643

Co-authored-by: Aleksey Kliger <alklig@microsoft.com>

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/FirstCallAfterUpdate.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Reflection.Metadata.ApplyUpdate.Test
+{
+    public class FirstCallAfterUpdate {
+        public FirstCallAfterUpdate() {}
+        public string Method1 (string s) {
+            return s + " STRING";
+        }
+    }
+}

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/FirstCallAfterUpdate_v1.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Reflection.Metadata.ApplyUpdate.Test
+{
+    public class FirstCallAfterUpdate {
+        public FirstCallAfterUpdate() {}
+        public string Method1(string s) {
+            return "NEW " + s;
+        }
+    }
+}

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/FirstCallAfterUpdate_v2.cs

@@ -0,0 +1,12 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+namespace System.Reflection.Metadata.ApplyUpdate.Test
+{
+    public class FirstCallAfterUpdate {
+        public FirstCallAfterUpdate() {}
+        public string Method1(string s) {
+            return s + "EST STRING";
+        }
+    }
+}

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <RootNamespace>System.Runtime.Loader.Tests</RootNamespace>
+    <TargetFrameworks>$(NetCoreAppCurrent)</TargetFrameworks>
+    <TestRuntime>true</TestRuntime>
+    <DeltaScript>deltascript.json</DeltaScript>
+    <SkipTestUtilitiesReference>true</SkipTestUtilitiesReference>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="FirstCallAfterUpdate.cs" />
+  </ItemGroup>
+</Project>

src/libraries/System.Runtime.Loader/tests/ApplyUpdate/System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate/deltascript.json

@@ -0,0 +1,7 @@
+{
+    "changes": [
+        {"document": "FirstCallAfterUpdate.cs", "update": "FirstCallAfterUpdate_v1.cs"},
+       {"document": "FirstCallAfterUpdate.cs", "update": "FirstCallAfterUpdate_v2.cs"},
+    ]
+}
+

src/libraries/System.Runtime.Loader/tests/ApplyUpdateTest.cs

@@ -94,6 +94,26 @@ void LambdaCapturesThis()
             });
         }
 
+        [ConditionalFact(typeof(ApplyUpdateUtil), nameof (ApplyUpdateUtil.IsSupported))]
+        [ActiveIssue("https://github.com/dotnet/runtime/issues/54617", typeof(PlatformDetection), nameof(PlatformDetection.IsBrowser), nameof(PlatformDetection.IsMonoAOT))] 
+        void FirstCallAfterUpdate()
+        {
+            /* Tests that updating a method that has not been called before works correctly and that
+             * the JIT/interpreter doesn't have to rely on cached baseline data. */
+            ApplyUpdateUtil.TestCase(static () =>
+            {
+                var assm = typeof (ApplyUpdate.Test.FirstCallAfterUpdate).Assembly;
+
+                var o = new ApplyUpdate.Test.FirstCallAfterUpdate ();
+
+                ApplyUpdateUtil.ApplyUpdate(assm);
+                ApplyUpdateUtil.ApplyUpdate(assm);
+
+                string r = o.Method1("NEW");
+
+                Assert.Equal("NEWEST STRING", r);
+            });
+        }
 
         [ConditionalFact(typeof(ApplyUpdateUtil), nameof (ApplyUpdateUtil.IsSupported))]
         [ActiveIssue("https://github.com/dotnet/runtime/issues/52993", TestRuntimes.Mono)]

src/libraries/System.Runtime.Loader/tests/System.Runtime.Loader.Tests.csproj

@@ -38,6 +38,7 @@
     <ProjectReference Include="ApplyUpdate\System.Reflection.Metadata.ApplyUpdate.Test.CustomAttributeUpdate\System.Reflection.Metadata.ApplyUpdate.Test.CustomAttributeUpdate.csproj" />
     <ProjectReference Include="ApplyUpdate\System.Reflection.Metadata.ApplyUpdate.Test.LambdaBodyChange\System.Reflection.Metadata.ApplyUpdate.Test.LambdaBodyChange.csproj" />
     <ProjectReference Include="ApplyUpdate\System.Reflection.Metadata.ApplyUpdate.Test.LambdaCapturesThis\System.Reflection.Metadata.ApplyUpdate.Test.LambdaCapturesThis.csproj" />
+    <ProjectReference Include="ApplyUpdate\System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate\System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate.csproj" />
 
   </ItemGroup>
   <ItemGroup Condition="'$(TargetOS)' == 'Browser'">
@@ -54,6 +55,7 @@
       <TrimmerRootAssembly Condition="$([System.String]::Copy('%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)').EndsWith('System.Reflection.Metadata.ApplyUpdate.Test.CustomAttributeUpdate.dll'))" Include="%(ResolvedFileToPublish.FullPath)" />
       <TrimmerRootAssembly Condition="$([System.String]::Copy('%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)').EndsWith('System.Reflection.Metadata.ApplyUpdate.Test.LambdaBodyChange.dll'))" Include="%(ResolvedFileToPublish.FullPath)" />
       <TrimmerRootAssembly Condition="$([System.String]::Copy('%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)').EndsWith('System.Reflection.Metadata.ApplyUpdate.Test.LambdaCapturesThis.dll'))" Include="%(ResolvedFileToPublish.FullPath)" />
+      <TrimmerRootAssembly Condition="$([System.String]::Copy('%(ResolvedFileToPublish.FileName)%(ResolvedFileToPublish.Extension)').EndsWith('System.Reflection.Metadata.ApplyUpdate.Test.FirstCallAfterUpdate.dll'))" Include="%(ResolvedFileToPublish.FullPath)" />
     </ItemGroup>
   </Target>
 

src/mono/mono/component/hot_reload.c

@@ -793,6 +793,13 @@ hot_reload_effective_table_slow (const MonoTableInfo **t, int *idx)
 	if (G_LIKELY (*idx < table_info_get_rows (*t) && !any_modified))
 		return;
 
+	/* FIXME: when adding methods this won't work anymore.  We will need to update the delta
+	 * images' suppressed columns (see the Note in pass2 about
+	 * CMiniMdRW::m_SuppressedDeltaColumns) with the baseline values. */
+	/* The only column from the updates that matters the RVA, which is looked up elsewhere. */
+	if (tbl_index == MONO_TABLE_METHOD)
+		return;
+
 	GList *list = info->delta_image;
 	MonoImage *dmeta;
 	int ridx;
@@ -1272,6 +1279,29 @@ apply_enclog_pass2 (MonoImage *image_base, BaselineInfo *base_info, uint32_t gen
 	MonoTableInfo *table_enclog = &image_dmeta->tables [MONO_TABLE_ENCLOG];
 	int rows = table_info_get_rows (table_enclog);
 
+	/* NOTE: Suppressed colums
+	 *
+	 * Certain column values in some tables in the deltas are not meant to be applied over the
+	 * previous generation. See CMiniMdRW::m_SuppressedDeltaColumns in CoreCLR.  For example the
+	 * MONO_METHOD_PARAMLIST column in MONO_TABLE_METHOD is always 0 in an update - for modified
+	 * rows the previous value must be carried over. For added rows, it is supposed to be
+	 * initialized to the end of the param table and updated with the "Param create" func code
+	 * in subsequent EnCLog records.
+	 *
+	 * For mono's immutable model (where we don't change the baseline image data), we will need
+	 * to mutate the delta image tables to incorporate the suppressed column values from the
+	 * previous generation.
+	 *
+	 * For Baseline capabilities, the only suppressed column is MONO_METHOD_PARAMLIST - which we
+	 * can ignore because we don't do anything with param updates and the only column we care
+	 * about is MONO_METHOD_RVA which gets special case treatment with set_update_method().
+	 *
+	 * But when we implement additional capabilities (for example UpdateParameters), we will
+	 * need to start mutating the delta image tables to pick up the suppressed column values.
+	 * Fortunately whether we get the delta from the debugger or from the runtime API, we always
+	 * have it in writable memory (and not mmap-ed pages), so we can rewrite the table values.
+	 */
+
 	gboolean assemblyref_updated = FALSE;
 	for (int i = 0; i < rows ; ++i) {
 		guint32 cols [MONO_ENCLOG_SIZE];