Add Per-assembly Load Native Library callbacks

This Change implements the Native Library resolution
Call-backs proposed in https://github.com/dotnet/corefx/issues/32015

Author: swaroop-sridhar

src/System.Private.CoreLib/src/System/Runtime/InteropServices/NativeLibrary.cs

@@ -12,6 +12,22 @@
 
 namespace System.Runtime.InteropServices
 {
+
+    /// <summary>
+    /// A delegate used to resolve native libraries via callback.
+    /// </summary>
+    /// <param name="libraryName">The native library to resolve</param>
+    /// <param name="assembly">The assembly requesting the resolution</param>
+    /// <param name="DllImportSearchPath?">
+    ///     The DllImportSearchPathsAttribute on the PInvoke, if any. 
+    ///     Otherwise, the DllImportSearchPathsAttribute on the assembly, if any. 
+    ///     Otherwise null.
+    /// </param>
+    /// <returns>The handle for the loaded native library on success, null on failure</returns>  
+    public delegate IntPtr DllImportResolver(string libraryName,
+                                             Assembly assembly,
+                                             DllImportSearchPath? searchPath);
+
     /// <summary>
     /// APIs for managing Native Libraries 
     /// </summary>
@@ -58,7 +74,9 @@ public static bool TryLoad(string libraryPath, out IntPtr handle)
         /// Otherwise, the flags specified by the DefaultDllImportSearchPaths attribute on the 
         /// calling assembly (if any) are used. 
         /// This LoadLibrary() method does not invoke the managed call-backs for native library resolution: 
+        /// * The per-assembly registered callback 
         /// * AssemblyLoadContext.LoadUnmanagedDll()
+        /// * AssemblyLoadContext.ResolvingUnmanagedDllEvent
         /// </summary>
         /// <param name="libraryName">The name of the native library to be loaded</param>
         /// <param name="assembly">The assembly loading the native library</param>
@@ -117,7 +135,6 @@ public static bool TryLoad(string libraryName, Assembly assembly, DllImportSearc
         /// No action if the input handle is null.
         /// </summary>
         /// <param name="handle">The native library handle to be freed</param>
-        /// <exception cref="System.InvalidOperationException">If the operation fails</exception>
         public static void Free(IntPtr handle)
         {
             FreeLib(handle);
@@ -161,6 +178,74 @@ public static bool TryGetExport(IntPtr handle, string name, out IntPtr address)
             return address != IntPtr.Zero;
         }
 
+        /// <summary>
+        /// Map from assembly to native-library resolver.
+        /// Interop specific fields and properties are generally not added to Assembly class.
+        /// Therefore, this table uses weak assembly pointers to indirectly achieve 
+        /// similar behavior.
+        /// </summary>
+        public static ConditionalWeakTable<Assembly, DllImportResolver> s_nativeDllResolveMap = null;
+
+        /// <summary>
+        /// Set a callback for resolving native library imports from an assembly.
+        /// This per-assembly resolver is the first attempt to resolve native library loads 
+        /// initiated by this assembly.
+        ///
+        /// Only one resolver can be registered per assembly. 
+        /// Trying to register a second resolver fails with InvalidOperationException.
+        /// </summary>
+        /// <param name="assembly">The assembly for which the resolver is registered</param>
+        /// <param name="resolver">The resolver callback to register</param>
+        /// <exception cref="System.ArgumentNullException">If assembly or resolver is null</exception>
+        /// <exception cref="System.ArgumentException">If a resolver is already set for this assembly</exception>
+        public static void SetDllImportResolver(Assembly assembly, DllImportResolver resolver)
+        {
+            if (assembly == null)
+                throw new ArgumentNullException(nameof(assembly));
+            if (resolver == null)
+                throw new ArgumentNullException(nameof(resolver));
+            if (!(assembly is RuntimeAssembly))
+                throw new ArgumentException(SR.Argument_MustBeRuntimeAssembly);
+
+            if (s_nativeDllResolveMap == null)
+            {
+                s_nativeDllResolveMap = new ConditionalWeakTable<Assembly, DllImportResolver>();
+            }
+
+            try
+            {
+                s_nativeDllResolveMap.Add(assembly, resolver);
+            }
+            catch (ArgumentException e)
+            {
+                // ConditionalWealTable throws ArgumentException if the Key already exists
+                throw new InvalidOperationException("Resolver is alerady Set for the Assembly");
+            }
+        }
+
+        /// <summary>
+        /// The helper function that calls the per-assembly native-library resolver 
+        /// if one is registered for this assembly.
+        /// </summary>
+        /// <param name="libraryName">The native library to load</param>
+        /// <param name="assembly">The assembly trying load the native library</param>
+        /// <param name="hasDllImportSearchPathFlags">If the pInvoke has DefaultDllImportSearchPathAttribute</param>
+        /// <param name="dllImportSearchPathFlags">If hasdllImportSearchPathFlags is true, the flags in 
+        ///                                       DefaultDllImportSearchPathAttribute; meaningless otherwise </param>
+        /// <returns>The handle for the loaded library on success. Null on failure.</returns>  
+        internal static IntPtr LoadLibraryCallbackStub(string libraryName, Assembly assembly,
+                                                       bool hasDllImportSearchPathFlags, uint dllImportSearchPathFlags)
+        {
+            DllImportResolver resolver;
+
+            if (!s_nativeDllResolveMap.TryGetValue(assembly, out resolver))
+            {
+                return IntPtr.Zero;
+            }
+
+            return resolver(libraryName, assembly, hasDllImportSearchPathFlags ? (DllImportSearchPath?)dllImportSearchPathFlags : null);
+        }
+
         /// External functions that implement the NativeLibrary interface
 
         [DllImport(JitHelpers.QCall, CharSet = CharSet.Unicode)]

src/vm/callhelpers.h

@@ -566,6 +566,7 @@ enum DispatchCallSimpleFlags
 #define STRINGREF_TO_ARGHOLDER(x) (LPVOID)STRINGREFToObject(x)
 #define PTR_TO_ARGHOLDER(x) (LPVOID)x
 #define DWORD_TO_ARGHOLDER(x)   (LPVOID)(SIZE_T)x
+#define BOOL_TO_ARGHOLDER(x) DWORD_TO_ARGHOLDER(!!(x))   
 
 #define INIT_VARIABLES(count)                               \
         DWORD   __numArgs = count;                          \

src/vm/dllimport.cpp

@@ -51,11 +51,6 @@
 #include "clr/fs/path.h"
 using namespace clr::fs;
 
-// The Bit 0x2 has different semantics in DllImportSearchPath and LoadLibraryExA flags.
-// In DllImportSearchPath enum, bit 0x2 represents SearchAssemblyDirectory -- which is performed by CLR.
-// Unlike other bits in this enum, this bit shouldn't be directly passed on to LoadLibrary()
-#define DLLIMPORTSEARCHPATH_ASSEMBLYDIRECTORY 0x2
-
 // remove when we get an updated SDK
 #define LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR 0x00000100
 #define LOAD_LIBRARY_SEARCH_DEFAULT_DIRS 0x00001000
@@ -6127,6 +6122,57 @@ bool         NDirect::s_fSecureLoadLibrarySupported = false;
 #define PLATFORM_SHARED_LIB_PREFIX_W W("")
 #endif // !FEATURE_PAL
 
+// The Bit 0x2 has different semantics in DllImportSearchPath and LoadLibraryExA flags.
+// In DllImportSearchPath enum, bit 0x2 represents SearchAssemblyDirectory -- which is performed by CLR.
+// Unlike other bits in this enum, this bit shouldn't be directly passed on to LoadLibrary()
+#define DLLIMPORTSEARCHPATH_ASSEMBLYDIRECTORY 0x2
+
+// DllImportSearchPathFlags is a special enumeration, whose values are tied closely with LoadLibrary flags.
+// There is no "default" value DllImportSearchPathFlags. In the absence of DllImportSearchPath attribute, 
+// CoreCLR's LoadLibrary implementation uses the following defaults.
+// Other implementations of LoadLibrary callbacks/events are free to use other default conventions.
+void GetDefaultDllImportSearchPathFlags(DWORD *dllImportSearchPathFlags, BOOL *searchAssemblyDirectory)
+{
+    STANDARD_VM_CONTRACT;
+
+    *searchAssemblyDirectory = TRUE;
+    *dllImportSearchPathFlags = 0;
+}
+
+// If a module has the DllImportSearchPathAttribute, get DllImportSearchPathFlags from it, and return true.
+// Otherwise, get the default value for the flags, and return false.
+BOOL GetDllImportSearchPathFlags(Module *pModule, DWORD *dllImportSearchPathFlags, BOOL *searchAssemblyDirectory)
+{
+    STANDARD_VM_CONTRACT;
+
+    if (pModule->HasDefaultDllImportSearchPathsAttribute())
+    {
+        *dllImportSearchPathFlags = pModule->DefaultDllImportSearchPathsAttributeCachedValue();
+        *searchAssemblyDirectory = pModule->DllImportSearchAssemblyDirectory();
+        return true;
+    }
+
+    GetDefaultDllImportSearchPathFlags(dllImportSearchPathFlags, searchAssemblyDirectory);
+    return false;
+}
+
+// If a pInvoke has DllImportSearchPathAttribute, get DllImportSearchPathFlags from it, and returns true.
+// Otherwise, if the containing assembly has the DllImportSearchPathAttribute, get DllImportSearchPathFlags from it, and returns true.
+// Otherwise, return false (out parameters are untouched).
+BOOL GetDllImportSearchPathFlags(NDirectMethodDesc * pMD, DWORD *dllImportSearchPathFlags, BOOL *searchAssemblyDirectory)
+{
+    STANDARD_VM_CONTRACT;
+
+    if (pMD->HasDefaultDllImportSearchPathsAttribute())
+    {
+        *dllImportSearchPathFlags = pMD->DefaultDllImportSearchPathsAttributeCachedValue();
+        *searchAssemblyDirectory = pMD->DllImportSearchAssemblyDirectory();
+        return true;
+    }
+
+    return GetDllImportSearchPathFlags(pMD->GetModule(), dllImportSearchPathFlags, searchAssemblyDirectory);
+}
+
 // static
 NATIVE_LIBRARY_HANDLE NDirect::LoadLibraryFromPath(LPCWSTR libraryPath, BOOL throwOnError)
 {
@@ -6165,25 +6211,21 @@ NATIVE_LIBRARY_HANDLE NDirect::LoadLibraryByName(LPCWSTR libraryName, Assembly *
     LoadLibErrorTracker errorTracker;
 
     // First checks if a default dllImportSearchPathFlags was passed in, if so, use that value.
-    // Otherwise checks if the assembly has the DefaultDllImportSearchPathsAttribute attribute. If so, use that value.
-    BOOL searchAssemblyDirectory = TRUE;
-    DWORD dllImportSearchPathFlags = 0;
+    // Otherwise checks if the assembly has the DefaultDllImportSearchPathsAttribute attribute. 
+    // If so, use that value.
+    BOOL searchAssemblyDirectory;
+    DWORD dllImportSearchPathFlags;
 
     if (hasDllImportSearchFlags)
     {
         dllImportSearchPathFlags = dllImportSearchFlags & ~DLLIMPORTSEARCHPATH_ASSEMBLYDIRECTORY;
         searchAssemblyDirectory = dllImportSearchFlags & DLLIMPORTSEARCHPATH_ASSEMBLYDIRECTORY;
 
     }
-    else 
+    else
     {
-        Module * pModule = callingAssembly->GetManifestModule();
-
-        if (pModule->HasDefaultDllImportSearchPathsAttribute())
-        {
-            dllImportSearchPathFlags = pModule->DefaultDllImportSearchPathsAttributeCachedValue();
-            searchAssemblyDirectory = pModule->DllImportSearchAssemblyDirectory();
-        }
+        GetDllImportSearchPathFlags(callingAssembly->GetManifestModule(),
+                                    &dllImportSearchPathFlags, &searchAssemblyDirectory);
     }
 
     NATIVE_LIBRARY_HANDLE hmod = 
@@ -6203,26 +6245,10 @@ NATIVE_LIBRARY_HANDLE NDirect::LoadLibraryModuleBySearch(NDirectMethodDesc * pMD
 {
     STANDARD_VM_CONTRACT;
 
-    // First checks if the method has DefaultDllImportSearchPathsAttribute. If so, use that value.
-    // Otherwise checks if the assembly has the attribute. If so, use that value.
-    BOOL searchAssemblyDirectory = TRUE;
-    DWORD dllImportSearchPathFlags = 0;
+    BOOL searchAssemblyDirectory;
+    DWORD dllImportSearchPathFlags;
 
-    if (pMD->HasDefaultDllImportSearchPathsAttribute())
-    {
-        dllImportSearchPathFlags = pMD->DefaultDllImportSearchPathsAttributeCachedValue();
-        searchAssemblyDirectory = pMD->DllImportSearchAssemblyDirectory();
-    }
-    else 
-    {
-        Module * pModule = pMD->GetModule();
-
-        if (pModule->HasDefaultDllImportSearchPathsAttribute())
-        {
-            dllImportSearchPathFlags = pModule->DefaultDllImportSearchPathsAttributeCachedValue();
-            searchAssemblyDirectory = pModule->DllImportSearchAssemblyDirectory();
-        }
-    }
+    GetDllImportSearchPathFlags(pMD, &dllImportSearchPathFlags, &searchAssemblyDirectory);
 
     Assembly* pAssembly = pMD->GetMethodTable()->GetAssembly();
     return LoadLibraryModuleBySearch(pAssembly, searchAssemblyDirectory, dllImportSearchPathFlags, pErrorTracker, wszLibName);
@@ -6452,18 +6478,20 @@ NATIVE_LIBRARY_HANDLE NDirect::LoadLibraryModuleViaCallback(NDirectMethodDesc *
 {
     STANDARD_VM_CONTRACT;
 
-    NATIVE_LIBRARY_HANDLE handle = NULL;
-
-    DWORD dllImportSearchPathFlags = 0;
-    BOOL hasDllImportSearchPathFlags = pMD->HasDefaultDllImportSearchPathsAttribute();
-    if (hasDllImportSearchPathFlags)
+    if (pMD->GetModule()->IsSystem())
     {
-        dllImportSearchPathFlags = pMD->DefaultDllImportSearchPathsAttributeCachedValue();
-        if (pMD->DllImportSearchAssemblyDirectory())
-            dllImportSearchPathFlags |= DLLIMPORTSEARCHPATH_ASSEMBLYDIRECTORY;
+        // Don't attempt to callback on Corelib itself.
+        // The LoadLibrary callback stub is managed code that requires CoreLib 
+        return NULL;
     }
 
+    DWORD dllImportSearchPathFlags;
+    BOOL searchAssemblyDirectory;
+    BOOL hasDllImportSearchPathFlags = GetDllImportSearchPathFlags(pMD, &dllImportSearchPathFlags, &searchAssemblyDirectory);
+    dllImportSearchPathFlags |= searchAssemblyDirectory ? DLLIMPORTSEARCHPATH_ASSEMBLYDIRECTORY : 0;
+
     Assembly* pAssembly = pMD->GetMethodTable()->GetAssembly();
+    NATIVE_LIBRARY_HANDLE handle = NULL;
 
     GCX_COOP();
 
@@ -6491,87 +6519,6 @@ NATIVE_LIBRARY_HANDLE NDirect::LoadLibraryModuleViaCallback(NDirectMethodDesc *
     return handle;
 }
 
-// Return the AssemblyLoadContext for an assembly
-INT_PTR GetManagedAssemblyLoadContext(Assembly* pAssembly)
-{
-    STANDARD_VM_CONTRACT;
-
-    PTR_ICLRPrivBinder pBindingContext = pAssembly->GetManifestFile()->GetBindingContext();
-    if (pBindingContext == NULL)
-    {
-        // GetBindingContext() returns NULL for System.Private.CoreLib
-        return NULL;
-    }
-
-    UINT_PTR assemblyBinderID = 0;
-    IfFailThrow(pBindingContext->GetBinderID(&assemblyBinderID));
-
-    AppDomain *pDomain = GetAppDomain();
-    ICLRPrivBinder *pCurrentBinder = reinterpret_cast<ICLRPrivBinder *>(assemblyBinderID);
-
-#ifdef FEATURE_COMINTEROP
-    if (AreSameBinderInstance(pCurrentBinder, pDomain->GetWinRtBinder()))
-    {
-        // No ALC associated handle with WinRT Binders.
-        return NULL;
-    }
-#endif // FEATURE_COMINTEROP
-
-    // The code here deals with two implementations of ICLRPrivBinder interface: 
-    //    - CLRPrivBinderCoreCLR for the TPA binder in the default ALC, and 
-    //    - CLRPrivBinderAssemblyLoadContext for custom ALCs.
-    // in order obtain the associated ALC handle.
-    INT_PTR ptrManagedAssemblyLoadContext = AreSameBinderInstance(pCurrentBinder, pDomain->GetTPABinderContext())
-        ? ((CLRPrivBinderCoreCLR *)pCurrentBinder)->GetManagedAssemblyLoadContext() 
-        : ((CLRPrivBinderAssemblyLoadContext *)pCurrentBinder)->GetManagedAssemblyLoadContext();
-
-    return ptrManagedAssemblyLoadContext;
-}
-
-// static
-NATIVE_LIBRARY_HANDLE NDirect::LoadLibraryModuleViaEvent(NDirectMethodDesc * pMD, PCWSTR wszLibName)
-{
-    STANDARD_VM_CONTRACT;
-
-    NATIVE_LIBRARY_HANDLE hmod = NULL;
-    Assembly* pAssembly = pMD->GetMethodTable()->GetAssembly();
-    INT_PTR ptrManagedAssemblyLoadContext = GetManagedAssemblyLoadContext(pAssembly);
-
-    if (ptrManagedAssemblyLoadContext == NULL)
-    {
-        return NULL;
-    }
-
-    GCX_COOP();
-
-    struct {
-        STRINGREF DllName;
-        OBJECTREF AssemblyRef;
-    } gc = { NULL, NULL };
-
-    GCPROTECT_BEGIN(gc);
-
-    gc.DllName = StringObject::NewString(wszLibName);
-    gc.AssemblyRef = pAssembly->GetExposedObject();
-
-    // Prepare to invoke  System.Runtime.Loader.AssemblyLoadContext.ResolveUnmanagedDllUsingEvent method
-    // While ResolveUnmanagedDllUsingEvent() could compute the AssemblyLoadContext using the AssemblyRef
-    // argument, it will involve another pInvoke to the runtime. So AssemblyLoadContext is passed in 
-    // as an additional argument.
-    PREPARE_NONVIRTUAL_CALLSITE(METHOD__ASSEMBLYLOADCONTEXT__RESOLVEUNMANAGEDDLLUSINGEVENT);
-    DECLARE_ARGHOLDER_ARRAY(args, 3);
-    args[ARGNUM_0] = STRINGREF_TO_ARGHOLDER(gc.DllName);
-    args[ARGNUM_1] = OBJECTREF_TO_ARGHOLDER(gc.AssemblyRef);
-    args[ARGNUM_2] = PTR_TO_ARGHOLDER(ptrManagedAssemblyLoadContext);
-
-    // Make the call
-    CALL_MANAGED_METHOD(hmod, NATIVE_LIBRARY_HANDLE, args);
-
-    GCPROTECT_END();
-
-    return hmod;
-}
-
 // Try to load the module alongside the assembly where the PInvoke was declared.
 NATIVE_LIBRARY_HANDLE NDirect::LoadFromPInvokeAssemblyDirectory(Assembly *pAssembly, LPCWSTR libName, DWORD flags, LoadLibErrorTracker *pErrorTracker)
 {
@@ -6842,7 +6789,7 @@ HINSTANCE NDirect::LoadLibraryModule(NDirectMethodDesc * pMD, LoadLibErrorTracke
     if ( !name || !*name )
         return NULL;
 
-   PREFIX_ASSUME( name != NULL );
+    PREFIX_ASSUME( name != NULL );
     MAKE_WIDEPTR_FROMUTF8( wszLibName, name );
 
     ModuleHandleHolder hmod = LoadLibraryModuleViaCallback(pMD, wszLibName);