os: add Root.Remove

For #67002

Change-Id: Ibbf44c0bf62f53695a7399ba0dae5b84d5efd374
Reviewed-on: https://go-review.googlesource.com/c/go/+/627076
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

5 files changed, 138 insertions, 0 deletions

diff --git a/src/internal/syscall/unix/at_wasip1.go b/src/internal/syscall/unix/at_wasip1.go
index 45ae22afcc..2be7ef3630 100644
--- a/src/internal/syscall/unix/at_wasip1.go
+++ b/src/internal/syscall/unix/at_wasip1.go
@@ -17,8 +17,34 @@ const (
 	// to avoid changing AccessTime or ModifiedTime.
 	// Its value must match syscall/fs_wasip1.go
 	UTIME_OMIT = -0x2
+
+	AT_REMOVEDIR = 0x200
 )
 
+func Unlinkat(dirfd int, path string, flags int) error {
+	if flags&AT_REMOVEDIR == 0 {
+		return errnoErr(path_unlink_file(
+			int32(dirfd),
+			unsafe.StringData(path),
+			size(len(path)),
+		))
+	} else {
+		return errnoErr(path_remove_directory(
+			int32(dirfd),
+			unsafe.StringData(path),
+			size(len(path)),
+		))
+	}
+}
+
+//go:wasmimport wasi_snapshot_preview1 path_unlink_file
+//go:noescape
+func path_unlink_file(fd int32, path *byte, pathLen size) syscall.Errno
+
+//go:wasmimport wasi_snapshot_preview1 path_remove_directory
+//go:noescape
+func path_remove_directory(fd int32, path *byte, pathLen size) syscall.Errno
+
 func Openat(dirfd int, path string, flags int, perm uint32) (int, error) {
 	return syscall.Openat(dirfd, path, flags, perm)
 }
diff --git a/src/internal/syscall/windows/at_windows.go b/src/internal/syscall/windows/at_windows.go
index af8167dd06..72780139a0 100644
--- a/src/internal/syscall/windows/at_windows.go
+++ b/src/internal/syscall/windows/at_windows.go
@@ -6,6 +6,7 @@ package windows
 
 import (
 	"syscall"
+	"unsafe"
 )
 
 // Openat flags not supported by syscall.Open.
@@ -171,3 +172,72 @@ func Mkdirat(dirfd syscall.Handle, name string, mode uint32) error {
 	syscall.CloseHandle(h)
 	return nil
 }
+
+func Deleteat(dirfd syscall.Handle, name string) error {
+	objAttrs := &OBJECT_ATTRIBUTES{}
+	if err := objAttrs.init(dirfd, name); err != nil {
+		return err
+	}
+	var h syscall.Handle
+	err := NtOpenFile(
+		&h,
+		DELETE,
+		objAttrs,
+		&IO_STATUS_BLOCK{},
+		FILE_SHARE_DELETE|FILE_SHARE_READ|FILE_SHARE_WRITE,
+		FILE_OPEN_REPARSE_POINT|FILE_OPEN_FOR_BACKUP_INTENT,
+	)
+	if err != nil {
+		return ntCreateFileError(err, 0)
+	}
+	defer syscall.CloseHandle(h)
+
+	const (
+		FileDispositionInformation   = 13
+		FileDispositionInformationEx = 64
+	)
+
+	// First, attempt to delete the file using POSIX semantics
+	// (which permit a file to be deleted while it is still open).
+	// This matches the behavior of DeleteFileW.
+	err = NtSetInformationFile(
+		h,
+		&IO_STATUS_BLOCK{},
+		uintptr(unsafe.Pointer(&FILE_DISPOSITION_INFORMATION_EX{
+			Flags: FILE_DISPOSITION_DELETE |
+				FILE_DISPOSITION_FORCE_IMAGE_SECTION_CHECK |
+				FILE_DISPOSITION_POSIX_SEMANTICS |
+				// This differs from DeleteFileW, but matches os.Remove's
+				// behavior on Unix platforms of permitting deletion of
+				// read-only files.
+				FILE_DISPOSITION_IGNORE_READONLY_ATTRIBUTE,
+		})),
+		uint32(unsafe.Sizeof(FILE_DISPOSITION_INFORMATION_EX{})),
+		FileDispositionInformationEx,
+	)
+	switch err {
+	case nil:
+		return nil
+	case STATUS_CANNOT_DELETE, STATUS_DIRECTORY_NOT_EMPTY:
+		return err.(NTStatus).Errno()
+	}
+
+	// If the prior deletion failed, the filesystem either doesn't support
+	// POSIX semantics (for example, FAT), or hasn't implemented
+	// FILE_DISPOSITION_INFORMATION_EX.
+	//
+	// Try again.
+	err = NtSetInformationFile(
+		h,
+		&IO_STATUS_BLOCK{},
+		uintptr(unsafe.Pointer(&FILE_DISPOSITION_INFORMATION{
+			DeleteFile: true,
+		})),
+		uint32(unsafe.Sizeof(FILE_DISPOSITION_INFORMATION{})),
+		FileDispositionInformation,
+	)
+	if st, ok := err.(NTStatus); ok {
+		return st.Errno()
+	}
+	return err
+}
diff --git a/src/internal/syscall/windows/syscall_windows.go b/src/internal/syscall/windows/syscall_windows.go
index 924f4951e7..f6fbf199bf 100644
--- a/src/internal/syscall/windows/syscall_windows.go
+++ b/src/internal/syscall/windows/syscall_windows.go
@@ -523,10 +523,14 @@ func (s NTStatus) Error() string {
 // If this list starts getting long, we should consider generating the full set.
 const (
 	STATUS_FILE_IS_A_DIRECTORY       NTStatus = 0xC00000BA
+	STATUS_DIRECTORY_NOT_EMPTY       NTStatus = 0xC0000101
 	STATUS_NOT_A_DIRECTORY           NTStatus = 0xC0000103
+	STATUS_CANNOT_DELETE             NTStatus = 0xC0000121
 	STATUS_REPARSE_POINT_ENCOUNTERED NTStatus = 0xC000050B
 )
 
 // NT Native APIs
 //sys   NtCreateFile(handle *syscall.Handle, access uint32, oa *OBJECT_ATTRIBUTES, iosb *IO_STATUS_BLOCK, allocationSize *int64, attributes uint32, share uint32, disposition uint32, options uint32, eabuffer uintptr, ealength uint32) (ntstatus error) = ntdll.NtCreateFile
+//sys   NtOpenFile(handle *syscall.Handle, access uint32, oa *OBJECT_ATTRIBUTES, iosb *IO_STATUS_BLOCK, share uint32, options uint32) (ntstatus error) = ntdll.NtOpenFile
 //sys   rtlNtStatusToDosErrorNoTeb(ntstatus NTStatus) (ret syscall.Errno) = ntdll.RtlNtStatusToDosErrorNoTeb
+//sys   NtSetInformationFile(handle syscall.Handle, iosb *IO_STATUS_BLOCK, inBuffer uintptr, inBufferLen uint32, class uint32) (ntstatus error) = ntdll.NtSetInformationFile
diff --git a/src/internal/syscall/windows/types_windows.go b/src/internal/syscall/windows/types_windows.go
index 514feafae4..6ae37afff8 100644
--- a/src/internal/syscall/windows/types_windows.go
+++ b/src/internal/syscall/windows/types_windows.go
@@ -196,3 +196,23 @@ const (
 	FILE_OPEN_NO_RECALL            = 0x00400000
 	FILE_OPEN_FOR_FREE_SPACE_QUERY = 0x00800000
 )
+
+// https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntddk/ns-ntddk-_file_disposition_information
+type FILE_DISPOSITION_INFORMATION struct {
+	DeleteFile bool
+}
+
+// https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntddk/ns-ntddk-_file_disposition_information_ex
+type FILE_DISPOSITION_INFORMATION_EX struct {
+	Flags uint32
+}
+
+// https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/ntddk/ns-ntddk-_file_disposition_information_ex
+const (
+	FILE_DISPOSITION_DO_NOT_DELETE             = 0x00000000
+	FILE_DISPOSITION_DELETE                    = 0x00000001
+	FILE_DISPOSITION_POSIX_SEMANTICS           = 0x00000002
+	FILE_DISPOSITION_FORCE_IMAGE_SECTION_CHECK = 0x00000004
+	FILE_DISPOSITION_ON_CLOSE                  = 0x00000008
+	FILE_DISPOSITION_IGNORE_READONLY_ATTRIBUTE = 0x00000010
+)
diff --git a/src/internal/syscall/windows/zsyscall_windows.go b/src/internal/syscall/windows/zsyscall_windows.go
index c81bc399ff..6a6ea7bdc0 100644
--- a/src/internal/syscall/windows/zsyscall_windows.go
+++ b/src/internal/syscall/windows/zsyscall_windows.go
@@ -93,6 +93,8 @@ var (
 	procNetUserDel                        = modnetapi32.NewProc("NetUserDel")
 	procNetUserGetLocalGroups             = modnetapi32.NewProc("NetUserGetLocalGroups")
 	procNtCreateFile                      = modntdll.NewProc("NtCreateFile")
+	procNtOpenFile                        = modntdll.NewProc("NtOpenFile")
+	procNtSetInformationFile              = modntdll.NewProc("NtSetInformationFile")
 	procRtlGetVersion                     = modntdll.NewProc("RtlGetVersion")
 	procRtlNtStatusToDosErrorNoTeb        = modntdll.NewProc("RtlNtStatusToDosErrorNoTeb")
 	procGetProcessMemoryInfo              = modpsapi.NewProc("GetProcessMemoryInfo")
@@ -477,6 +479,22 @@ func NtCreateFile(handle *syscall.Handle, access uint32, oa *OBJECT_ATTRIBUTES,
 	return
 }
 
+func NtOpenFile(handle *syscall.Handle, access uint32, oa *OBJECT_ATTRIBUTES, iosb *IO_STATUS_BLOCK, share uint32, options uint32) (ntstatus error) {
+	r0, _, _ := syscall.Syscall6(procNtOpenFile.Addr(), 6, uintptr(unsafe.Pointer(handle)), uintptr(access), uintptr(unsafe.Pointer(oa)), uintptr(unsafe.Pointer(iosb)), uintptr(share), uintptr(options))
+	if r0 != 0 {
+		ntstatus = NTStatus(r0)
+	}
+	return
+}
+
+func NtSetInformationFile(handle syscall.Handle, iosb *IO_STATUS_BLOCK, inBuffer uintptr, inBufferLen uint32, class uint32) (ntstatus error) {
+	r0, _, _ := syscall.Syscall6(procNtSetInformationFile.Addr(), 5, uintptr(handle), uintptr(unsafe.Pointer(iosb)), uintptr(inBuffer), uintptr(inBufferLen), uintptr(class), 0)
+	if r0 != 0 {
+		ntstatus = NTStatus(r0)
+	}
+	return
+}
+
 func rtlGetVersion(info *_OSVERSIONINFOW) {
 	syscall.Syscall(procRtlGetVersion.Addr(), 1, uintptr(unsafe.Pointer(info)), 0, 0)
 	return