From 6d4fc1ad4725ca4cc77214b93bc1d37a6fa3553d Mon Sep 17 00:00:00 2001
From: Filip Navara <filip.navara@gmail.com>
Date: Sat, 17 Feb 2024 17:02:29 +0100
Subject: [PATCH] [NativeAOT] Add null checks into memcpy/memset helpers
 (#98547)

---
 .../Runtime/CompilerHelpers/MemoryHelpers.cs  | 33 +++++++++++++++++++
 .../src/System.Private.CoreLib.csproj         |  1 +
 .../ILCompiler.Compiler/Compiler/JitHelper.cs |  4 +--
 3 files changed, 36 insertions(+), 2 deletions(-)
 create mode 100644 src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Runtime/CompilerHelpers/MemoryHelpers.cs

diff --git a/src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Runtime/CompilerHelpers/MemoryHelpers.cs b/src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Runtime/CompilerHelpers/MemoryHelpers.cs
new file mode 100644
index 0000000000000..644fcf1a59940
--- /dev/null
+++ b/src/coreclr/nativeaot/System.Private.CoreLib/src/Internal/Runtime/CompilerHelpers/MemoryHelpers.cs
@@ -0,0 +1,33 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System;
+using System.Runtime;
+
+namespace Internal.Runtime.CompilerHelpers
+{
+    /// <summary>
+    /// These methods are used to implement memcpy and memset intrinsics with null checks.
+    /// </summary>
+    internal static class MemoryHelpers
+    {
+        private static unsafe void MemSet(ref byte dest, byte value, nuint size)
+        {
+            if (size > 0)
+            {
+                _ = dest;
+                SpanHelpers.Fill(ref dest, size, value);
+            }
+        }
+
+        private static unsafe void MemCopy(ref byte dest, ref byte src, nuint size)
+        {
+            if (size > 0)
+            {
+                _ = dest;
+                _ = src;
+                Buffer.Memmove(ref dest, ref src, size);
+            }
+        }
+    }
+}
diff --git a/src/coreclr/nativeaot/System.Private.CoreLib/src/System.Private.CoreLib.csproj b/src/coreclr/nativeaot/System.Private.CoreLib/src/System.Private.CoreLib.csproj
index 4ca91458c70e7..d6e8c3a7e9027 100644
--- a/src/coreclr/nativeaot/System.Private.CoreLib/src/System.Private.CoreLib.csproj
+++ b/src/coreclr/nativeaot/System.Private.CoreLib/src/System.Private.CoreLib.csproj
@@ -100,6 +100,7 @@
     <Compile Include="Internal\Runtime\CompilerHelpers\ArrayHelpers.cs" />
     <Compile Include="Internal\Runtime\CompilerHelpers\InteropHelpers.cs" />
     <Compile Include="Internal\Runtime\CompilerHelpers\LdTokenHelpers.cs" />
+    <Compile Include="Internal\Runtime\CompilerHelpers\MemoryHelpers.cs" />
     <Compile Include="Internal\Runtime\CompilerHelpers\RuntimeInteropData.cs" />
     <Compile Include="Internal\Runtime\CompilerHelpers\SynchronizedMethodHelpers.cs" />
     <Compile Include="Internal\Runtime\CompilerHelpers\TypedReferenceHelpers.cs" />
diff --git a/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/JitHelper.cs b/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/JitHelper.cs
index 9e7285b751a3d..c55dc58175b05 100644
--- a/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/JitHelper.cs
+++ b/src/coreclr/tools/aot/ILCompiler.Compiler/Compiler/JitHelper.cs
@@ -134,10 +134,10 @@ public static void GetEntryPoint(TypeSystemContext context, ReadyToRunHelper id,
                     break;
 
                 case ReadyToRunHelper.MemCpy:
-                    mangledName = "memcpy"; // TODO: Null reference handling
+                    methodDesc = context.GetHelperEntryPoint("MemoryHelpers", "MemCopy");
                     break;
                 case ReadyToRunHelper.MemSet:
-                    mangledName = "memset"; // TODO: Null reference handling
+                    methodDesc = context.GetHelperEntryPoint("MemoryHelpers", "MemSet");
                     break;
 
                 case ReadyToRunHelper.GetRuntimeTypeHandle: