headers: call per-scrape native functions with SyscallN (#2746)

Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

internal/headers/wtsapi32/wtsapi32.go

@@ -20,6 +20,7 @@ package wtsapi32
 import (
 	"fmt"
 	"log/slog"
+	"syscall"
 	"unsafe"
 
 	"github.com/prometheus-community/windows_exporter/internal/headers/lazyproc"
@@ -141,7 +142,7 @@ func WTSOpenServer(server string) (windows.Handle, error) {
 		}
 	}
 
-	r1, _, err := procWTSOpenServerEx.Call(uintptr(unsafe.Pointer(serverName)))
+	r1, _, err := syscall.SyscallN(procWTSOpenServerEx.Addr(), uintptr(unsafe.Pointer(serverName)))
 	serverHandle := windows.Handle(r1)
 
 	if serverHandle == windows.InvalidHandle {
@@ -154,11 +155,12 @@ func WTSOpenServer(server string) (windows.Handle, error) {
 // WTSCloseServer closes a handle opened by WTSOpenServer. The function returns
 // void, so neither r1 nor the last error say whether it failed.
 func WTSCloseServer(server windows.Handle) {
-	_, _, _ = procWTSCloseServer.Call(uintptr(server))
+	_, _, _ = syscall.SyscallN(procWTSCloseServer.Addr(), uintptr(server))
 }
 
 func WTSFreeMemoryEx(class WTSTypeClass, pMemory uintptr, numberOfEntries uint32) error {
-	r1, _, err := procWTSFreeMemoryEx.Call(
+	r1, _, err := syscall.SyscallN(
+		procWTSFreeMemoryEx.Addr(),
 		uintptr(class),
 		pMemory,
 		uintptr(numberOfEntries),
@@ -177,7 +179,8 @@ func WTSEnumerateSessionsEx(server windows.Handle, logger *slog.Logger) ([]WTSSe
 	var count uint32
 
 	pLevel := uint32(1)
-	r1, _, err := procWTSEnumerateSessionsEx.Call(
+	r1, _, err := syscall.SyscallN(
+		procWTSEnumerateSessionsEx.Addr(),
 		uintptr(server),
 		uintptr(unsafe.Pointer(&pLevel)),
 		uintptr(0),

internal/headers/wtsapi32/wtsapi32_test.go

@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: Apache-2.0
+//
+// Copyright The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//go:build windows
+
+package wtsapi32_test
+
+import (
+	"log/slog"
+	"testing"
+
+	"github.com/prometheus-community/windows_exporter/internal/headers/wtsapi32"
+	"github.com/stretchr/testify/require"
+)
+
+func TestWTSEnumerateSessionsEx(t *testing.T) {
+	t.Parallel()
+
+	server, err := wtsapi32.WTSOpenServer("")
+	require.NoError(t, err)
+
+	t.Cleanup(func() { wtsapi32.WTSCloseServer(server) })
+
+	sessions, err := wtsapi32.WTSEnumerateSessionsEx(server, slog.New(slog.DiscardHandler))
+	require.NoError(t, err)
+	require.NotEmpty(t, sessions, "session 0 always exists")
+}
+
+func BenchmarkWTSEnumerateSessionsEx(b *testing.B) {
+	server, err := wtsapi32.WTSOpenServer("")
+	require.NoError(b, err)
+
+	b.Cleanup(func() { wtsapi32.WTSCloseServer(server) })
+
+	logger := slog.New(slog.DiscardHandler)
+
+	b.ReportAllocs()
+
+	for b.Loop() {
+		_, _ = wtsapi32.WTSEnumerateSessionsEx(server, logger)
+	}
+}