system: read the boot time from the kernel on every scrape (#2690)

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

internal/headers/kernel32/kernel32.go

@@ -29,7 +29,6 @@ var (
 
 	procGetDynamicTimeZoneInformationSys = modkernel32.NewProc("GetDynamicTimeZoneInformation")
 	procKernelLocalFileTimeToFileTime    = modkernel32.NewProc("LocalFileTimeToFileTime")
-	procGetTickCount                     = modkernel32.NewProc("GetTickCount64")
 	procOpenJobObject                    = modkernel32.NewProc("OpenJobObjectW")
 	procIsProcessInJob                   = modkernel32.NewProc("IsProcessInJob")
 )
@@ -81,9 +80,3 @@ func LocalFileTimeToFileTime(localFileTime, utcFileTime *windows.Filetime) uint3
 
 	return uint32(ret)
 }
-
-func GetTickCount64() uint64 {
-	ret, _, _ := procGetTickCount.Call()
-
-	return uint64(ret)
-}

internal/headers/ntdll/time.go

@@ -0,0 +1,63 @@
+// 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 ntdll
+
+import (
+	"fmt"
+	"time"
+	"unsafe"
+
+	"golang.org/x/sys/windows"
+)
+
+// SystemTimeOfDayInformation is the SYSTEM_TIMEOFDAY_INFORMATION structure.
+// The times are in 100-nanosecond intervals since January 1, 1601 (UTC).
+type SystemTimeOfDayInformation struct {
+	BootTime      int64
+	CurrentTime   int64
+	TimeZoneBias  int64
+	TimeZoneID    uint32
+	Reserved      uint32
+	BootTimeBias  uint64
+	SleepTimeBias uint64
+}
+
+// BootTime returns the time the system booted.
+//
+// The kernel moves the boot time along when the system time is set, so it
+// stays correct after a clock correction.
+func BootTime() (time.Time, error) {
+	var info SystemTimeOfDayInformation
+
+	err := windows.NtQuerySystemInformation(
+		windows.SystemTimeOfDayInformation,
+		unsafe.Pointer(&info),
+		uint32(unsafe.Sizeof(info)),
+		nil,
+	)
+	if err != nil {
+		return time.Time{}, fmt.Errorf("NtQuerySystemInformation(SystemTimeOfDayInformation): %w", err)
+	}
+
+	ft := windows.Filetime{
+		LowDateTime:  uint32(info.BootTime),
+		HighDateTime: uint32(info.BootTime >> 32),
+	}
+
+	return time.Unix(0, ft.Nanoseconds()), nil
+}

internal/headers/ntdll/time_test.go

@@ -0,0 +1,42 @@
+// 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 ntdll_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/prometheus-community/windows_exporter/internal/headers/ntdll"
+	"github.com/stretchr/testify/require"
+)
+
+func TestBootTime(t *testing.T) {
+	t.Parallel()
+
+	bootTime, err := ntdll.BootTime()
+	require.NoError(t, err)
+
+	require.True(t, bootTime.Before(time.Now()), "boot time %s is in the future", bootTime)
+	require.True(t, bootTime.After(time.Date(2000, 1, 1, 0, 0, 0, 0, time.UTC)), "boot time %s is too old", bootTime)
+
+	// The boot time must not depend on when it is read. Allow for a clock
+	// correction between the two calls.
+	again, err := ntdll.BootTime()
+	require.NoError(t, err)
+	require.WithinDuration(t, bootTime, again, time.Second)
+}