runtime,syscall: move loadlibrary and getprocaddress to syscall

There is no need for loadlibrary, loadsystemlibrary and getprocaddress
to be implemented in the runtime and linknamed from syscall.

Change-Id: Icefd53a8e8f7012ed0c94c356be4179d5e45a01b
Reviewed-on: https://go-review.googlesource.com/c/go/+/690516
Reviewed-by: Mark Freeman <mark@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

src/runtime/os_windows.go

@@ -41,7 +41,6 @@ const (
 //go:cgo_import_dynamic runtime._GetThreadContext GetThreadContext%2 "kernel32.dll"
 //go:cgo_import_dynamic runtime._SetThreadContext SetThreadContext%2 "kernel32.dll"
 //go:cgo_import_dynamic runtime._LoadLibraryExW LoadLibraryExW%3 "kernel32.dll"
-//go:cgo_import_dynamic runtime._LoadLibraryW LoadLibraryW%1 "kernel32.dll"
 //go:cgo_import_dynamic runtime._PostQueuedCompletionStatus PostQueuedCompletionStatus%4 "kernel32.dll"
 //go:cgo_import_dynamic runtime._QueryPerformanceCounter QueryPerformanceCounter%1 "kernel32.dll"
 //go:cgo_import_dynamic runtime._QueryPerformanceFrequency QueryPerformanceFrequency%1 "kernel32.dll"
@@ -99,7 +98,6 @@ var (
 	_GetThreadContext,
 	_SetThreadContext,
 	_LoadLibraryExW,
-	_LoadLibraryW,
 	_PostQueuedCompletionStatus,
 	_QueryPerformanceCounter,
 	_QueryPerformanceFrequency,
@@ -245,6 +243,7 @@ func windows_GetSystemDirectory() string {
 }
 
 func windowsLoadSystemLib(name []uint16) uintptr {
+	const _LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
 	return stdcall3(_LoadLibraryExW, uintptr(unsafe.Pointer(&name[0])), 0, _LOAD_LIBRARY_SEARCH_SYSTEM32)
 }
 

src/runtime/syscall_windows.go

@@ -412,48 +412,9 @@ func callbackWrap(a *callbackArgs) {
 	}
 }
 
-const _LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
-
-//go:linkname syscall_loadsystemlibrary syscall.loadsystemlibrary
-func syscall_loadsystemlibrary(filename *uint16) (handle, err uintptr) {
-	handle, _, err = syscall_syscalln(uintptr(unsafe.Pointer(_LoadLibraryExW)), 3, uintptr(unsafe.Pointer(filename)), 0, _LOAD_LIBRARY_SEARCH_SYSTEM32)
-	KeepAlive(filename)
-	if handle != 0 {
-		err = 0
-	}
-	return
-}
-
-// golang.org/x/sys linknames syscall.loadlibrary
-// (in addition to standard package syscall).
-// Do not remove or change the type signature.
-//
-//go:linkname syscall_loadlibrary syscall.loadlibrary
-func syscall_loadlibrary(filename *uint16) (handle, err uintptr) {
-	handle, _, err = syscall_syscalln(uintptr(unsafe.Pointer(_LoadLibraryW)), 1, uintptr(unsafe.Pointer(filename)))
-	KeepAlive(filename)
-	if handle != 0 {
-		err = 0
-	}
-	return
-}
-
-// golang.org/x/sys linknames syscall.getprocaddress
-// (in addition to standard package syscall).
-// Do not remove or change the type signature.
-//
-//go:linkname syscall_getprocaddress syscall.getprocaddress
-func syscall_getprocaddress(handle uintptr, procname *byte) (outhandle, err uintptr) {
-	outhandle, _, err = syscall_syscalln(uintptr(unsafe.Pointer(_GetProcAddress)), 2, handle, uintptr(unsafe.Pointer(procname)))
-	KeepAlive(procname)
-	if outhandle != 0 {
-		err = 0
-	}
-	return
-}
-
 //go:linkname syscall_syscalln syscall.syscalln
 //go:nosplit
+//go:uintptrkeepalive
 func syscall_syscalln(fn, n uintptr, args ...uintptr) (r1, r2, err uintptr) {
 	if n > uintptr(len(args)) {
 		panic("syscall: n > len(args)") // should not be reachable from user code

src/syscall/dll_windows.go

@@ -11,6 +11,15 @@ import (
 	"unsafe"
 )
 
+// Use double underscore to avoid name collision autogenerated functions.
+//go:cgo_import_dynamic syscall.__LoadLibraryExW LoadLibraryExW%3 "kernel32.dll"
+//go:cgo_import_dynamic syscall.__GetProcAddress GetProcAddress%2 "kernel32.dll"
+
+var (
+	__LoadLibraryExW unsafe.Pointer
+	__GetProcAddress unsafe.Pointer
+)
+
 // DLLError describes reasons for DLL load failures.
 type DLLError struct {
 	Err     error
@@ -94,9 +103,39 @@ func SyscallN(p uintptr, args ...uintptr) (r1, r2 uintptr, err Errno) {
 //
 //go:noescape
 func syscalln(fn, n uintptr, args ...uintptr) (r1, r2 uintptr, err Errno)
-func loadlibrary(filename *uint16) (handle uintptr, err Errno)
-func loadsystemlibrary(filename *uint16) (handle uintptr, err Errno)
-func getprocaddress(handle uintptr, procname *uint8) (proc uintptr, err Errno)
+
+// N.B. For the loadlibrary, loadlibrary, and getprocaddress functions below:
+//
+// //go:linkname to act as an allowlist for linker's -checklinkname, as
+// golang.org/x/sys/windows linknames these functions.
+
+//go:linkname loadlibrary
+func loadlibrary(filename *uint16) (uintptr, Errno) {
+	handle, _, err := SyscallN(uintptr(__LoadLibraryExW), uintptr(unsafe.Pointer(filename)), 0, 0)
+	if handle != 0 {
+		err = 0
+	}
+	return handle, err
+}
+
+//go:linkname loadsystemlibrary
+func loadsystemlibrary(filename *uint16) (uintptr, Errno) {
+	const _LOAD_LIBRARY_SEARCH_SYSTEM32 = 0x00000800
+	handle, _, err := SyscallN(uintptr(__LoadLibraryExW), uintptr(unsafe.Pointer(filename)), 0, _LOAD_LIBRARY_SEARCH_SYSTEM32)
+	if handle != 0 {
+		err = 0
+	}
+	return handle, err
+}
+
+//go:linkname getprocaddress
+func getprocaddress(handle uintptr, procname *uint8) (uintptr, Errno) {
+	proc, _, err := SyscallN(uintptr(__GetProcAddress), handle, uintptr(unsafe.Pointer(procname)))
+	if proc != 0 {
+		err = 0
+	}
+	return proc, err
+}
 
 // A DLL implements access to a single DLL.
 type DLL struct {