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windows/svc: rewrite in Go

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The old service management code was written in assembly and communicated
over Windows events, which resulted in non-obvious control flow.
NewCallback makes it possible to rewrite all of this in vanilla Go. This
also enables the service test on the Go builders, as modifying system
services shouldn't be an issue there.

Change-Id: I8003b57d11d4469f762058c648a4b7733530eeb8
Reviewed-on: https://go-review.googlesource.com/c/sys/+/330010
Trust: Jason A. Donenfeld <Jason@zx2c4.com>
Trust: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Jason A. Donenfeld
2021-10-20 06:40:51 +00:00
parent 9d821ace86
commit 0ec99a608a
12 changed files with 64 additions and 435 deletions
Download Patch File Download Diff File Expand all files Collapse all files
windows/svc/service.go
+52 -140
View File
@@ -10,8 +10,7 @@ package svc
import (
"errors"
"runtime"
"syscall"
"sync"
"unsafe"
"golang.org/x/sys/internal/unsafeheader"
@@ -91,7 +90,6 @@ type ChangeRequest struct {
// Handler is the interface that must be implemented to build Windows service.
type Handler interface {
// Execute will be called by the package code at the start of
// the service, and the service will exit once Execute completes.
// Inside Execute you must read service change requests from r and
@@ -106,28 +104,6 @@ type Handler interface {
Execute(args []string, r <-chan ChangeRequest, s chan<- Status) (svcSpecificEC bool, exitCode uint32)
}
var (
// These are used by asm code.
goWaitsH uintptr
cWaitsH uintptr
ssHandle uintptr
sName *uint16
sArgc uintptr
sArgv **uint16
ctlHandlerExProc uintptr
cSetEvent uintptr
cWaitForSingleObject uintptr
cRegisterServiceCtrlHandlerExW uintptr
)
func init() {
k := windows.NewLazySystemDLL("kernel32.dll")
cSetEvent = k.NewProc("SetEvent").Addr()
cWaitForSingleObject = k.NewProc("WaitForSingleObject").Addr()
a := windows.NewLazySystemDLL("advapi32.dll")
cRegisterServiceCtrlHandlerExW = a.NewProc("RegisterServiceCtrlHandlerExW").Addr()
}
type ctlEvent struct {
cmd Cmd
eventType uint32
@@ -140,36 +116,10 @@ type ctlEvent struct {
type service struct {
name string
h windows.Handle
cWaits *event
goWaits *event
c chan ctlEvent
handler Handler
}
func newService(name string, handler Handler) (*service, error) {
var s service
var err error
s.name = name
s.c = make(chan ctlEvent)
s.handler = handler
s.cWaits, err = newEvent()
if err != nil {
return nil, err
}
s.goWaits, err = newEvent()
if err != nil {
s.cWaits.Close()
return nil, err
}
return &s, nil
}
func (s *service) close() error {
s.cWaits.Close()
s.goWaits.Close()
return nil
}
type exitCode struct {
isSvcSpecific bool
errno uint32
@@ -224,23 +174,43 @@ func (s *service) updateStatus(status *Status, ec *exitCode) error {
return windows.SetServiceStatus(s.h, &t)
}
const (
sysErrSetServiceStatusFailed = uint32(syscall.APPLICATION_ERROR) + iota
sysErrNewThreadInCallback
var (
initCallbacks sync.Once
ctlHandlerCallback uintptr
serviceMainCallback uintptr
)
func (s *service) run() {
s.goWaits.Wait()
s.h = windows.Handle(ssHandle)
func ctlHandler(ctl, evtype, evdata, context uintptr) uintptr {
s := (*service)(unsafe.Pointer(context))
e := ctlEvent{cmd: Cmd(ctl), eventType: uint32(evtype), eventData: evdata, context: 123456} // Set context to 123456 to test issue #25660.
s.c <- e
return 0
}
var argv []*uint16
hdr := (*unsafeheader.Slice)(unsafe.Pointer(&argv))
hdr.Data = unsafe.Pointer(sArgv)
hdr.Len = int(sArgc)
hdr.Cap = int(sArgc)
var theService service // This is, unfortunately, a global, which means only one service per process.
args := make([]string, len(argv))
for i, a := range argv {
// serviceMain is the entry point called by the service manager, registered earlier by
// the call to StartServiceCtrlDispatcher.
func serviceMain(argc uint32, argv **uint16) uintptr {
handle, err := windows.RegisterServiceCtrlHandlerEx(windows.StringToUTF16Ptr(theService.name), ctlHandlerCallback, uintptr(unsafe.Pointer(&theService)))
if sysErr, ok := err.(windows.Errno); ok {
return uintptr(sysErr)
} else if err != nil {
return uintptr(windows.ERROR_UNKNOWN_EXCEPTION)
}
theService.h = handle
defer func() {
theService.h = 0
windows.CloseHandle(handle)
}()
var args16 []*uint16
hdr := (*unsafeheader.Slice)(unsafe.Pointer(&args16))
hdr.Data = unsafe.Pointer(argv)
hdr.Len = int(argc)
hdr.Cap = int(argc)
args := make([]string, len(args16))
for i, a := range args16 {
args[i] = windows.UTF16PtrToString(a)
}
@@ -249,7 +219,7 @@ func (s *service) run() {
exitFromHandler := make(chan exitCode)
go func() {
ss, errno := s.handler.Execute(args, cmdsToHandler, changesFromHandler)
ss, errno := theService.handler.Execute(args, cmdsToHandler, changesFromHandler)
exitFromHandler <- exitCode{ss, errno}
}()
@@ -258,7 +228,7 @@ func (s *service) run() {
CurrentStatus: Status{State: Stopped},
}
var outch chan ChangeRequest
inch := s.c
inch := theService.c
loop:
for {
select {
@@ -274,14 +244,13 @@ loop:
outcr.EventData = r.eventData
outcr.Context = r.context
case outch <- outcr:
inch = s.c
inch = theService.c
outch = nil
case c := <-changesFromHandler:
err := s.updateStatus(&c, &ec)
err := theService.updateStatus(&c, &ec)
if err != nil {
// best suitable error number
ec.errno = sysErrSetServiceStatusFailed
if err2, ok := err.(syscall.Errno); ok {
ec.errno = uint32(windows.ERROR_EXCEPTION_IN_SERVICE)
if err2, ok := err.(windows.Errno); ok {
ec.errno = uint32(err2)
}
break loop
@@ -292,87 +261,30 @@ loop:
}
}
s.updateStatus(&Status{State: Stopped}, &ec)
s.cWaits.Set()
}
theService.updateStatus(&Status{State: Stopped}, &ec)
func newCallback(fn interface{}) (cb uintptr, err error) {
defer func() {
r := recover()
if r == nil {
return
}
cb = 0
switch v := r.(type) {
case string:
err = errors.New(v)
case error:
err = v
default:
err = errors.New("unexpected panic in syscall.NewCallback")
}
}()
return syscall.NewCallback(fn), nil
return windows.NO_ERROR
}
// BUG(brainman): There is no mechanism to run multiple services
// inside one single executable. Perhaps, it can be overcome by
// using RegisterServiceCtrlHandlerEx Windows api.
// Run executes service name by calling appropriate handler function.
func Run(name string, handler Handler) error {
runtime.LockOSThread()
tid := windows.GetCurrentThreadId()
s, err := newService(name, handler)
if err != nil {
return err
}
ctlHandler := func(ctl, evtype, evdata, context uintptr) uintptr {
e := ctlEvent{cmd: Cmd(ctl), eventType: uint32(evtype), eventData: evdata, context: context}
// We assume that this callback function is running on
// the same thread as Run. Nowhere in MS documentation
// I could find statement to guarantee that. So putting
// check here to verify, otherwise things will go bad
// quickly, if ignored.
i := windows.GetCurrentThreadId()
if i != tid {
e.errno = sysErrNewThreadInCallback
}
s.c <- e
// Always return NO_ERROR (0) for now.
return windows.NO_ERROR
}
var svcmain uintptr
getServiceMain(&svcmain)
initCallbacks.Do(func() {
ctlHandlerCallback = windows.NewCallback(ctlHandler)
serviceMainCallback = windows.NewCallback(serviceMain)
})
theService.name = name
theService.handler = handler
theService.c = make(chan ctlEvent)
t := []windows.SERVICE_TABLE_ENTRY{
{ServiceName: syscall.StringToUTF16Ptr(s.name), ServiceProc: svcmain},
{ServiceName: windows.StringToUTF16Ptr(theService.name), ServiceProc: serviceMainCallback},
{ServiceName: nil, ServiceProc: 0},
}
goWaitsH = uintptr(s.goWaits.h)
cWaitsH = uintptr(s.cWaits.h)
sName = t[0].ServiceName
ctlHandlerExProc, err = newCallback(ctlHandler)
if err != nil {
return err
}
go s.run()
err = windows.StartServiceCtrlDispatcher(&t[0])
if err != nil {
return err
}
return nil
return windows.StartServiceCtrlDispatcher(&t[0])
}
// StatusHandle returns service status handle. It is safe to call this function
// from inside the Handler.Execute because then it is guaranteed to be set.
// This code will have to change once multiple services are possible per process.
func StatusHandle() windows.Handle {
return windows.Handle(ssHandle)
return theService.h
}