Add test for external assembly probe mechanism (#113007)

- Only try to convert to a loaded layout by file mapping for images that are files
- Add test that uses corerun with external assembly probe

src/coreclr/hosts/corerun/corerun.cpp

@@ -70,6 +70,12 @@ namespace envvar
 
     // Variable used to preload a mock hostpolicy for testing.
     const char_t* mockHostPolicy = W("MOCK_HOSTPOLICY");
+
+    // Variable used to indicate how app assemblies should be provided to the runtime
+    // - PROPERTY: corerun will pass the paths vias the TRUSTED_PLATFORM_ASSEMBLIES property
+    // - EXTERNAL: corerun will pass an external assembly probe to the runtime for app assemblies
+    // - Not set: same as PROPERTY
+    const char_t* appAssemblies = W("APP_ASSEMBLIES");
 }
 
 static void wait_for_debugger()
@@ -242,6 +248,37 @@ size_t HOST_CONTRACT_CALLTYPE get_runtime_property(
     return -1;
 }
 
+// Paths for external assembly probe
+static char* s_core_libs_path = nullptr;
+static char* s_core_root_path = nullptr;
+
+static bool HOST_CONTRACT_CALLTYPE external_assembly_probe(
+    const char* path,
+    void** data_start,
+    int64_t* size)
+{
+    // Get just the file name
+    const char* name = path;
+    const char* pos = strrchr(name, '/');
+    if (pos != NULL)
+        name = pos + 1;
+
+    // Try to map the file from our known app assembly paths
+    for (const char* dir : { s_core_libs_path, s_core_root_path })
+    {
+        if (dir == nullptr)
+            continue;
+
+        std::string full_path = dir;
+        assert(full_path.back() == pal::dir_delim);
+        full_path.append(name);
+        if (pal::try_map_file_readonly(full_path.c_str(), data_start, size))
+            return true;
+    }
+
+    return false;
+}
+
 static int run(const configuration& config)
 {
     platform_specific_actions actions;
@@ -295,7 +332,37 @@ static int run(const configuration& config)
         native_search_dirs << core_root << pal::env_path_delim;
     }
 
-    string_t tpa_list = build_tpa(core_root, core_libs);
+    string_t tpa_list;
+    string_t app_assemblies_env = pal::getenv(envvar::appAssemblies);
+    bool use_external_assembly_probe = false;
+    if (app_assemblies_env.empty() || app_assemblies_env == W("PROPERTY"))
+    {
+        // Use the TRUSTED_PLATFORM_ASSEMBLIES property to pass the app assemblies to the runtime.
+        tpa_list = build_tpa(core_root, core_libs);
+    }
+    else if (app_assemblies_env == W("EXTERNAL"))
+    {
+        // Use the external assembly probe to load assemblies from the app assembly paths.
+        use_external_assembly_probe = true;
+        if (!core_libs.empty())
+        {
+            pal::string_utf8_t core_libs_utf8 = pal::convert_to_utf8(core_libs.c_str());
+            s_core_libs_path = (char*)::malloc(core_libs_utf8.length() + 1);
+            ::strcpy(s_core_libs_path, core_libs_utf8.c_str());
+        }
+
+        if (!core_root.empty())
+        {
+            pal::string_utf8_t core_root_utf8 = pal::convert_to_utf8(core_root.c_str());
+            s_core_root_path = (char*)::malloc(core_root_utf8.length() + 1);
+            ::strcpy(s_core_root_path, core_root_utf8.c_str());
+        }
+    }
+    else
+    {
+        pal::fprintf(stderr, W("Unknown value for APP_ASSEMBLIES environment variable: %s\n"), app_assemblies_env.c_str());
+        return -1;
+    }
 
     {
         // Load hostpolicy if requested.
@@ -376,7 +443,8 @@ static int run(const configuration& config)
         (void*)&config,
         &get_runtime_property,
         nullptr,
-        nullptr };
+        nullptr,
+        use_external_assembly_probe ? &external_assembly_probe : nullptr };
     propertyKeys.push_back(HOST_PROPERTY_RUNTIME_CONTRACT);
     std::stringstream ss;
     ss << "0x" << std::hex << (size_t)(&host_contract);
@@ -457,6 +525,8 @@ static int run(const configuration& config)
     if (exit_code != -1)
         exit_code = latched_exit_code;
 
+    ::free((void*)s_core_libs_path);
+    ::free((void*)s_core_root_path);
     return exit_code;
 }
 

src/coreclr/hosts/corerun/corerun.hpp

@@ -134,6 +134,34 @@ namespace pal
         return INVALID_FILE_ATTRIBUTES != ::GetFileAttributesW(file_path.c_str());
     }
 
+    inline bool try_map_file_readonly(const char* path, void** mapped, int64_t* size)
+    {
+        HANDLE file = ::CreateFileA(path, GENERIC_READ, FILE_SHARE_READ, nullptr, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, nullptr);
+        if (file == INVALID_HANDLE_VALUE)
+            return false;
+
+        HANDLE file_mapping = ::CreateFileMappingA(file, nullptr, PAGE_READONLY, 0, 0, nullptr);
+        if (file_mapping  == nullptr)
+        {
+            ::CloseHandle(file);
+            return false;
+        }
+
+        void* mapped_local = ::MapViewOfFile(file_mapping, FILE_MAP_READ, 0, 0, 0);
+        if (mapped_local == nullptr)
+        {
+            ::CloseHandle(file);
+            ::CloseHandle(file_mapping);
+            return false;
+        }
+
+        *size = ::GetFileSize(file, nullptr);
+        *mapped = mapped_local;
+        ::CloseHandle(file_mapping);
+        ::CloseHandle(file);
+        return true;
+    }
+
     // Forward declaration
     void ensure_trailing_delimiter(pal::string_t& dir);
 
@@ -300,7 +328,9 @@ class platform_specific_actions final
 #else // !TARGET_WINDOWS
 #include <dirent.h>
 #include <dlfcn.h>
+#include <fcntl.h>
 #include <limits.h>
+#include <sys/mman.h>
 #include <sys/stat.h>
 #include <unistd.h>
 
@@ -309,7 +339,6 @@ class platform_specific_actions final
 #include <sys/sysctl.h>
 #include <sys/types.h>
 #else // !__APPLE__
-#include <fcntl.h>
 #include <ctype.h>
 #endif // !__APPLE__
 
@@ -434,6 +463,33 @@ namespace pal
         return true;
     }
 
+    inline bool try_map_file_readonly(const char* path, void** mapped, int64_t* size)
+    {
+        int fd = open(path, O_RDONLY);
+        if (fd == -1)
+            return false;
+
+        struct stat buf;
+        if (fstat(fd, &buf) == -1)
+        {
+            close(fd);
+            return false;
+        }
+
+        int64_t size_local = buf.st_size;
+        void* mapped_local = mmap(NULL, size_local, PROT_READ, MAP_PRIVATE, fd, 0);
+        if (mapped == MAP_FAILED)
+        {
+            close(fd);
+            return false;
+        }
+
+        *mapped = mapped_local;
+        *size = size_local;
+        close(fd);
+        return true;
+    }
+
     // Forward declaration
     template<size_t LEN>
     bool string_ends_with(const string_t& str, const char_t(&suffix)[LEN]);

src/coreclr/vm/peimagelayout.cpp

@@ -456,7 +456,9 @@ ConvertedImageLayout::ConvertedImageLayout(FlatImageLayout* source, bool disable
     LOG((LF_LOADER, LL_INFO100, "PEImage: Opening manually mapped stream\n"));
 
 #ifdef TARGET_WINDOWS
-    if (!disableMapping)
+    // LoadImageByMappingParts assumes the source has a file mapping handle created/managed by the runtime.
+    // This is not the case for non-file images (for example, external data). Only try to load by mapping for files.
+    if (!disableMapping && m_pOwner->IsFile())
     {
         loadedImage = source->LoadImageByMappingParts(this->m_imageParts);
         if (loadedImage == NULL)

src/tests/Loader/ExternalAssemblyProbe/ExternalAssemblyProbe.cs

@@ -0,0 +1,17 @@
+// 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 Xunit;
+
+public unsafe class ExternalAssemblyProbe
+{
+    [Fact]
+    public static void ExternalAppAssemblies()
+    {
+        // In order to get to this point, the runtime must have been able to find the app assemblies
+        // Check that the TPA is indeed empty - that is, the runtime is not relying on that property.
+        string tpa = AppContext.GetData("TRUSTED_PLATFORM_ASSEMBLIES") as string;
+        Assert.True(string.IsNullOrEmpty(tpa), "TRUSTED_PLATFORM_ASSEMBLIES should be empty");
+    }
+}

src/tests/Loader/ExternalAssemblyProbe/ExternalAssemblyProbe.csproj

@@ -0,0 +1,15 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <!-- Needed for CLRTestEnvironmentVariable -->
+    <RequiresProcessIsolation>true</RequiresProcessIsolation>
+    <NativeAotIncompatible>true</NativeAotIncompatible>
+    <!-- External assembly probe via host-runtime contract is not implemented.
+         The test uses probing to start at all, so it needs to be disabled in the project, not via an attribute -->
+    <CLRTestTargetUnsupported Condition="'$(RuntimeFlavor)' != 'coreclr'">true</CLRTestTargetUnsupported>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="ExternalAssemblyProbe.cs" />
+
+    <CLRTestEnvironmentVariable Include="APP_ASSEMBLIES" Value="EXTERNAL" />
+  </ItemGroup>
+</Project>