Revert "runtime: remove slow time compatibility hacks for wine"

This reverts CL 191759.

Reason for revert: broke most Go programs using the time package on Wine,
including on 4.15, the latest stable version. Only wine-staging (with
experimental patches) contains an upstream fix we could rely on.

Change-Id: Ic8ba126022e54f412174042fbb9abed82d5eb318
Reviewed-on: https://go-review.googlesource.com/c/go/+/192622
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

1 files changed, 78 insertions, 0 deletions

diff --git a/src/runtime/os_windows.go b/src/runtime/os_windows.go
index 2a2b5fa122..cd9e98914c 100644
--- a/src/runtime/os_windows.go
+++ b/src/runtime/os_windows.go
@@ -76,10 +76,12 @@ var (
 	_GetStdHandle,
 	_GetSystemDirectoryA,
 	_GetSystemInfo,
+	_GetSystemTimeAsFileTime,
 	_GetThreadContext,
 	_LoadLibraryW,
 	_LoadLibraryA,
 	_QueryPerformanceCounter,
+	_QueryPerformanceFrequency,
 	_ResumeThread,
 	_SetConsoleCtrlHandler,
 	_SetErrorMode,
@@ -252,6 +254,11 @@ func loadOptionalSyscalls() {
 	if _WSAGetOverlappedResult == nil {
 		throw("WSAGetOverlappedResult not found")
 	}
+
+	if windowsFindfunc(n32, []byte("wine_get_version\000")) != nil {
+		// running on Wine
+		initWine(k32)
+	}
 }
 
 func monitorSuspendResume() {
@@ -411,6 +418,77 @@ func osinit() {
 
 func nanotime() int64
 
+// useQPCTime controls whether time.now and nanotime use QueryPerformanceCounter.
+// This is only set to 1 when running under Wine.
+var useQPCTime uint8
+
+var qpcStartCounter int64
+var qpcMultiplier int64
+
+//go:nosplit
+func nanotimeQPC() int64 {
+	var counter int64 = 0
+	stdcall1(_QueryPerformanceCounter, uintptr(unsafe.Pointer(&counter)))
+
+	// returns number of nanoseconds
+	return (counter - qpcStartCounter) * qpcMultiplier
+}
+
+//go:nosplit
+func nowQPC() (sec int64, nsec int32, mono int64) {
+	var ft int64
+	stdcall1(_GetSystemTimeAsFileTime, uintptr(unsafe.Pointer(&ft)))
+
+	t := (ft - 116444736000000000) * 100
+
+	sec = t / 1000000000
+	nsec = int32(t - sec*1000000000)
+
+	mono = nanotimeQPC()
+	return
+}
+
+func initWine(k32 uintptr) {
+	_GetSystemTimeAsFileTime = windowsFindfunc(k32, []byte("GetSystemTimeAsFileTime\000"))
+	if _GetSystemTimeAsFileTime == nil {
+		throw("could not find GetSystemTimeAsFileTime() syscall")
+	}
+
+	_QueryPerformanceCounter = windowsFindfunc(k32, []byte("QueryPerformanceCounter\000"))
+	_QueryPerformanceFrequency = windowsFindfunc(k32, []byte("QueryPerformanceFrequency\000"))
+	if _QueryPerformanceCounter == nil || _QueryPerformanceFrequency == nil {
+		throw("could not find QPC syscalls")
+	}
+
+	// We can not simply fallback to GetSystemTimeAsFileTime() syscall, since its time is not monotonic,
+	// instead we use QueryPerformanceCounter family of syscalls to implement monotonic timer
+	// https://msdn.microsoft.com/en-us/library/windows/desktop/dn553408(v=vs.85).aspx
+
+	var tmp int64
+	stdcall1(_QueryPerformanceFrequency, uintptr(unsafe.Pointer(&tmp)))
+	if tmp == 0 {
+		throw("QueryPerformanceFrequency syscall returned zero, running on unsupported hardware")
+	}
+
+	// This should not overflow, it is a number of ticks of the performance counter per second,
+	// its resolution is at most 10 per usecond (on Wine, even smaller on real hardware), so it will be at most 10 millions here,
+	// panic if overflows.
+	if tmp > (1<<31 - 1) {
+		throw("QueryPerformanceFrequency overflow 32 bit divider, check nosplit discussion to proceed")
+	}
+	qpcFrequency := int32(tmp)
+	stdcall1(_QueryPerformanceCounter, uintptr(unsafe.Pointer(&qpcStartCounter)))
+
+	// Since we are supposed to run this time calls only on Wine, it does not lose precision,
+	// since Wine's timer is kind of emulated at 10 Mhz, so it will be a nice round multiplier of 100
+	// but for general purpose system (like 3.3 Mhz timer on i7) it will not be very precise.
+	// We have to do it this way (or similar), since multiplying QPC counter by 100 millions overflows
+	// int64 and resulted time will always be invalid.
+	qpcMultiplier = int64(timediv(1000000000, qpcFrequency, nil))
+
+	useQPCTime = 1
+}
+
 //go:nosplit
 func getRandomData(r []byte) {
 	n := 0