1 files changed, 29 insertions, 1 deletions

diff --git a/src/runtime/os1_windows.go b/src/runtime/os1_windows.go
index d0120347db..ab378b0730 100644
--- a/src/runtime/os1_windows.go
+++ b/src/runtime/os1_windows.go
@@ -88,8 +88,11 @@ var (
 
 	// Following syscalls are only available on some Windows PCs.
 	// We will load syscalls, if available, before using them.
+	_AddDllDirectory,
 	_AddVectoredContinueHandler,
-	_GetQueuedCompletionStatusEx stdFunction
+	_GetQueuedCompletionStatusEx,
+	_LoadLibraryExW,
+	_ stdFunction
 )
 
 // Call a Windows function with stdcall conventions,
@@ -110,8 +113,10 @@ func loadOptionalSyscalls() {
 		return stdFunction(unsafe.Pointer(f))
 	}
 	if l != 0 {
+		_AddDllDirectory = findfunc("AddDllDirectory")
 		_AddVectoredContinueHandler = findfunc("AddVectoredContinueHandler")
 		_GetQueuedCompletionStatusEx = findfunc("GetQueuedCompletionStatusEx")
+		_LoadLibraryExW = findfunc("LoadLibraryExW")
 	}
 }
 
@@ -121,6 +126,11 @@ func getLoadLibrary() uintptr {
 }
 
 //go:nosplit
+func getLoadLibraryEx() uintptr {
+	return uintptr(unsafe.Pointer(_LoadLibraryExW))
+}
+
+//go:nosplit
 func getGetProcAddress() uintptr {
 	return uintptr(unsafe.Pointer(_GetProcAddress))
 }
@@ -139,6 +149,22 @@ const (
 // in sys_windows_386.s and sys_windows_amd64.s
 func externalthreadhandler()
 
+// When loading DLLs, we prefer to use LoadLibraryEx with
+// LOAD_LIBRARY_SEARCH_* flags, if available. LoadLibraryEx is not
+// available on old Windows, though, and the LOAD_LIBRARY_SEARCH_*
+// flags are not available on some versions of Windows without a
+// security patch.
+//
+// https://msdn.microsoft.com/en-us/library/ms684179(v=vs.85).aspx says:
+// "Windows 7, Windows Server 2008 R2, Windows Vista, and Windows
+// Server 2008: The LOAD_LIBRARY_SEARCH_* flags are available on
+// systems that have KB2533623 installed. To determine whether the
+// flags are available, use GetProcAddress to get the address of the
+// AddDllDirectory, RemoveDllDirectory, or SetDefaultDllDirectories
+// function. If GetProcAddress succeeds, the LOAD_LIBRARY_SEARCH_*
+// flags can be used with LoadLibraryEx."
+var useLoadLibraryEx bool
+
 func osinit() {
 	asmstdcallAddr = unsafe.Pointer(funcPC(asmstdcall))
 
@@ -146,6 +172,8 @@ func osinit() {
 
 	loadOptionalSyscalls()
 
+	useLoadLibraryEx = (_LoadLibraryExW != nil && _AddDllDirectory != nil)
+
 	disableWER()
 
 	externalthreadhandlerp = funcPC(externalthreadhandler)