os: implement File.Chmod on Windows

Fixes: #39606

Change-Id: I4def67ef18bd3ff866b140f6e76cdabe5d51a1c5
Reviewed-on: https://go-review.googlesource.com/c/go/+/250077
Run-TryBot: Alex Brainman <alex.brainman@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>

5 files changed, 60 insertions, 11 deletions

diff --git a/src/internal/poll/fd_posix.go b/src/internal/poll/fd_posix.go
index e5fb05c9c2..4edfa953a4 100644
--- a/src/internal/poll/fd_posix.go
+++ b/src/internal/poll/fd_posix.go
@@ -29,17 +29,6 @@ func (fd *FD) Shutdown(how int) error {
 	return syscall.Shutdown(fd.Sysfd, how)
 }
 
-// Fchmod wraps syscall.Fchmod.
-func (fd *FD) Fchmod(mode uint32) error {
-	if err := fd.incref(); err != nil {
-		return err
-	}
-	defer fd.decref()
-	return ignoringEINTR(func() error {
-		return syscall.Fchmod(fd.Sysfd, mode)
-	})
-}
-
 // Fchown wraps syscall.Fchown.
 func (fd *FD) Fchown(uid, gid int) error {
 	if err := fd.incref(); err != nil {
diff --git a/src/internal/poll/fd_unix.go b/src/internal/poll/fd_unix.go
index 1d5101eac3..f6f6c52f31 100644
--- a/src/internal/poll/fd_unix.go
+++ b/src/internal/poll/fd_unix.go
@@ -437,6 +437,17 @@ func (fd *FD) ReadDirent(buf []byte) (int, error) {
 	}
 }
 
+// Fchmod wraps syscall.Fchmod.
+func (fd *FD) Fchmod(mode uint32) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+	return ignoringEINTR(func() error {
+		return syscall.Fchmod(fd.Sysfd, mode)
+	})
+}
+
 // Fchdir wraps syscall.Fchdir.
 func (fd *FD) Fchdir() error {
 	if err := fd.incref(); err != nil {
diff --git a/src/internal/poll/fd_windows.go b/src/internal/poll/fd_windows.go
index e1ef6199b3..d8c834f929 100644
--- a/src/internal/poll/fd_windows.go
+++ b/src/internal/poll/fd_windows.go
@@ -886,6 +886,33 @@ func (fd *FD) FindNextFile(data *syscall.Win32finddata) error {
 	return syscall.FindNextFile(fd.Sysfd, data)
 }
 
+// Fchmod updates syscall.ByHandleFileInformation.Fileattributes when needed.
+func (fd *FD) Fchmod(mode uint32) error {
+	if err := fd.incref(); err != nil {
+		return err
+	}
+	defer fd.decref()
+
+	var d syscall.ByHandleFileInformation
+	if err := syscall.GetFileInformationByHandle(fd.Sysfd, &d); err != nil {
+		return err
+	}
+	attrs := d.FileAttributes
+	if mode&syscall.S_IWRITE != 0 {
+		attrs &^= syscall.FILE_ATTRIBUTE_READONLY
+	} else {
+		attrs |= syscall.FILE_ATTRIBUTE_READONLY
+	}
+	if attrs == d.FileAttributes {
+		return nil
+	}
+
+	var du windows.FILE_BASIC_INFO
+	du.FileAttributes = attrs
+	l := uint32(unsafe.Sizeof(d))
+	return windows.SetFileInformationByHandle(fd.Sysfd, windows.FileBasicInfo, uintptr(unsafe.Pointer(&du)), l)
+}
+
 // Fchdir wraps syscall.Fchdir.
 func (fd *FD) Fchdir() error {
 	if err := fd.incref(); err != nil {
diff --git a/src/internal/syscall/windows/syscall_windows.go b/src/internal/syscall/windows/syscall_windows.go
index edf0b5a40b..1f40c11820 100644
--- a/src/internal/syscall/windows/syscall_windows.go
+++ b/src/internal/syscall/windows/syscall_windows.go
@@ -131,6 +131,14 @@ type IpAdapterAddresses struct {
 	/* more fields might be present here. */
 }
 
+type FILE_BASIC_INFO struct {
+	CreationTime   syscall.Filetime
+	LastAccessTime syscall.Filetime
+	LastWriteTime  syscall.Filetime
+	ChangedTime    syscall.Filetime
+	FileAttributes uint32
+}
+
 const (
 	IfOperStatusUp             = 1
 	IfOperStatusDown           = 2
@@ -145,6 +153,7 @@ const (
 //sys	GetComputerNameEx(nameformat uint32, buf *uint16, n *uint32) (err error) = GetComputerNameExW
 //sys	MoveFileEx(from *uint16, to *uint16, flags uint32) (err error) = MoveFileExW
 //sys	GetModuleFileName(module syscall.Handle, fn *uint16, len uint32) (n uint32, err error) = kernel32.GetModuleFileNameW
+//sys	SetFileInformationByHandle(handle syscall.Handle, fileInformationClass uint32, buf uintptr, bufsize uint32) (err error) = kernel32.SetFileInformationByHandle
 
 const (
 	WSA_FLAG_OVERLAPPED        = 0x01
diff --git a/src/internal/syscall/windows/zsyscall_windows.go b/src/internal/syscall/windows/zsyscall_windows.go
index ca5b4e6f16..0840dc283a 100644
--- a/src/internal/syscall/windows/zsyscall_windows.go
+++ b/src/internal/syscall/windows/zsyscall_windows.go
@@ -71,6 +71,7 @@ var (
 	procNetUserGetLocalGroups        = modnetapi32.NewProc("NetUserGetLocalGroups")
 	procGetProcessMemoryInfo         = modpsapi.NewProc("GetProcessMemoryInfo")
 	procGetFileInformationByHandleEx = modkernel32.NewProc("GetFileInformationByHandleEx")
+	procSetFileInformationByHandle   = modkernel32.NewProc("SetFileInformationByHandle")
 )
 
 func GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapterAddresses *IpAdapterAddresses, sizePointer *uint32) (errcode error) {
@@ -81,6 +82,18 @@ func GetAdaptersAddresses(family uint32, flags uint32, reserved uintptr, adapter
 	return
 }
 
+func SetFileInformationByHandle(handle syscall.Handle, fileInformationClass uint32, buf uintptr, bufsize uint32) (err error) {
+	r1, _, e1 := syscall.Syscall6(procSetFileInformationByHandle.Addr(), 4, uintptr(handle), uintptr(fileInformationClass), uintptr(buf), uintptr(bufsize), 0, 0)
+	if r1 == 0 {
+		if e1 != 0 {
+			err = errnoErr(e1)
+		} else {
+			err = syscall.EINVAL
+		}
+	}
+	return
+}
+
 func GetComputerNameEx(nameformat uint32, buf *uint16, n *uint32) (err error) {
 	r1, _, e1 := syscall.Syscall(procGetComputerNameExW.Addr(), 3, uintptr(nameformat), uintptr(unsafe.Pointer(buf)), uintptr(unsafe.Pointer(n)))
 	if r1 == 0 {