internal/poll: don't call SetFilePointerEx in Seek for overlapped handles

Overlapped handles don't have the file pointer updated when performing
I/O operations, so there is no need to call syscall.SetFilePointerEx in
FD.Seek. Updating the in-memory offset is sufficient.

Updates #74951 (provides a more complete fix)

Change-Id: Ibede6625cdbd501fc92cfdf8ce2782ec291af2b6
Reviewed-on: https://go-review.googlesource.com/c/go/+/698035
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Damien Neil <dneil@google.com>

3 files changed, 34 insertions, 5 deletions

diff --git a/src/internal/poll/fd_windows.go b/src/internal/poll/fd_windows.go
index 23500d3e39..4d466e5b64 100644
--- a/src/internal/poll/fd_windows.go
+++ b/src/internal/poll/fd_windows.go
@@ -1165,11 +1165,29 @@ func (fd *FD) Seek(offset int64, whence int) (int64, error) {
 	}
 	defer fd.readWriteUnlock()
 
-	if !fd.isBlocking && whence == io.SeekCurrent {
-		// Windows doesn't keep the file pointer for overlapped file handles.
-		// We do it ourselves in case to account for any read or write
-		// operations that may have occurred.
-		offset += fd.offset
+	if !fd.isBlocking {
+		// Windows doesn't use the file pointer for overlapped file handles,
+		// there is no point on calling syscall.Seek.
+		var newOffset int64
+		switch whence {
+		case io.SeekStart:
+			newOffset = offset
+		case io.SeekCurrent:
+			newOffset = fd.offset + offset
+		case io.SeekEnd:
+			var size int64
+			if err := windows.GetFileSizeEx(fd.Sysfd, &size); err != nil {
+				return 0, err
+			}
+			newOffset = size + offset
+		default:
+			return 0, windows.ERROR_INVALID_PARAMETER
+		}
+		if newOffset < 0 {
+			return 0, windows.ERROR_NEGATIVE_SEEK
+		}
+		fd.setOffset(newOffset)
+		return newOffset, nil
 	}
 	n, err := syscall.Seek(fd.Sysfd, offset, whence)
 	fd.setOffset(n)
diff --git a/src/internal/syscall/windows/syscall_windows.go b/src/internal/syscall/windows/syscall_windows.go
index 905cabc81e..b60648ea29 100644
--- a/src/internal/syscall/windows/syscall_windows.go
+++ b/src/internal/syscall/windows/syscall_windows.go
@@ -39,6 +39,7 @@ const (
 	ERROR_NOT_SUPPORTED          syscall.Errno = 50
 	ERROR_CALL_NOT_IMPLEMENTED   syscall.Errno = 120
 	ERROR_INVALID_NAME           syscall.Errno = 123
+	ERROR_NEGATIVE_SEEK          syscall.Errno = 131
 	ERROR_LOCK_FAILED            syscall.Errno = 167
 	ERROR_IO_INCOMPLETE          syscall.Errno = 996
 	ERROR_NO_TOKEN               syscall.Errno = 1008
@@ -195,6 +196,7 @@ const (
 //sys	SetFileInformationByHandle(handle syscall.Handle, fileInformationClass uint32, buf unsafe.Pointer, bufsize uint32) (err error) = kernel32.SetFileInformationByHandle
 //sys	VirtualQuery(address uintptr, buffer *MemoryBasicInformation, length uintptr) (err error) = kernel32.VirtualQuery
 //sys	GetTempPath2(buflen uint32, buf *uint16) (n uint32, err error) = GetTempPath2W
+//sys	GetFileSizeEx(handle syscall.Handle, size *int64) (err error) = kernel32.GetFileSizeEx
 
 const (
 	// flags for CreateToolhelp32Snapshot
diff --git a/src/internal/syscall/windows/zsyscall_windows.go b/src/internal/syscall/windows/zsyscall_windows.go
index 53f456c5cf..fb8bc80629 100644
--- a/src/internal/syscall/windows/zsyscall_windows.go
+++ b/src/internal/syscall/windows/zsyscall_windows.go
@@ -73,6 +73,7 @@ var (
 	procGetConsoleCP                      = modkernel32.NewProc("GetConsoleCP")
 	procGetCurrentThread                  = modkernel32.NewProc("GetCurrentThread")
 	procGetFileInformationByHandleEx      = modkernel32.NewProc("GetFileInformationByHandleEx")
+	procGetFileSizeEx                     = modkernel32.NewProc("GetFileSizeEx")
 	procGetFinalPathNameByHandleW         = modkernel32.NewProc("GetFinalPathNameByHandleW")
 	procGetModuleFileNameW                = modkernel32.NewProc("GetModuleFileNameW")
 	procGetModuleHandleW                  = modkernel32.NewProc("GetModuleHandleW")
@@ -326,6 +327,14 @@ func GetFileInformationByHandleEx(handle syscall.Handle, class uint32, info *byt
 	return
 }
 
+func GetFileSizeEx(handle syscall.Handle, size *int64) (err error) {
+	r1, _, e1 := syscall.Syscall(procGetFileSizeEx.Addr(), 2, uintptr(handle), uintptr(unsafe.Pointer(size)), 0)
+	if r1 == 0 {
+		err = errnoErr(e1)
+	}
+	return
+}
+
 func GetFinalPathNameByHandle(file syscall.Handle, filePath *uint16, filePathSize uint32, flags uint32) (n uint32, err error) {
 	r0, _, e1 := syscall.SyscallN(procGetFinalPathNameByHandleW.Addr(), uintptr(file), uintptr(unsafe.Pointer(filePath)), uintptr(filePathSize), uintptr(flags))
 	n = uint32(r0)