unix: add API for fsconfig system call

Fixes golang/go#59537

Change-Id: I8d806ace3adad423c633813455d8f758706cee1d
Reviewed-on: https://go-review.googlesource.com/c/sys/+/484995
Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>

Author: IlyaHanov

unix/linux/types.go

@@ -989,6 +989,15 @@ const (
 	FSPICK_EMPTY_PATH       = C.FSPICK_EMPTY_PATH
 
 	FSMOUNT_CLOEXEC = C.FSMOUNT_CLOEXEC
+
+	FSCONFIG_SET_FLAG        = C.FSCONFIG_SET_FLAG
+	FSCONFIG_SET_STRING      = C.FSCONFIG_SET_STRING
+	FSCONFIG_SET_BINARY      = C.FSCONFIG_SET_BINARY
+	FSCONFIG_SET_PATH        = C.FSCONFIG_SET_PATH
+	FSCONFIG_SET_PATH_EMPTY  = C.FSCONFIG_SET_PATH_EMPTY
+	FSCONFIG_SET_FD          = C.FSCONFIG_SET_FD
+	FSCONFIG_CMD_CREATE      = C.FSCONFIG_CMD_CREATE
+	FSCONFIG_CMD_RECONFIGURE = C.FSCONFIG_CMD_RECONFIGURE
 )
 
 type OpenHow C.struct_open_how

unix/syscall_linux.go

@@ -1849,6 +1849,105 @@ func Dup2(oldfd, newfd int) error {
 //sys	Fsmount(fd int, flags int, mountAttrs int) (fsfd int, err error)
 //sys	Fsopen(fsName string, flags int) (fd int, err error)
 //sys	Fspick(dirfd int, pathName string, flags int) (fd int, err error)
+
+//sys	fsconfig(fd int, cmd uint, key *byte, value *byte, aux int) (err error)
+
+func fsconfigCommon(fd int, cmd uint, key string, value *byte, aux int) (err error) {
+	var keyp *byte
+	if keyp, err = BytePtrFromString(key); err != nil {
+		return
+	}
+	return fsconfig(fd, cmd, keyp, value, aux)
+}
+
+// FsconfigSetFlag is equivalent to fsconfig(2) called
+// with cmd == FSCONFIG_SET_FLAG.
+//
+// fd is the filesystem context to act upon.
+// key the parameter key to set.
+func FsconfigSetFlag(fd int, key string) (err error) {
+	return fsconfigCommon(fd, FSCONFIG_SET_FLAG, key, nil, 0)
+}
+
+// FsconfigSetString is equivalent to fsconfig(2) called
+// with cmd == FSCONFIG_SET_STRING.
+//
+// fd is the filesystem context to act upon.
+// key the parameter key to set.
+// value is the parameter value to set.
+func FsconfigSetString(fd int, key string, value string) (err error) {
+	var valuep *byte
+	if valuep, err = BytePtrFromString(value); err != nil {
+		return
+	}
+	return fsconfigCommon(fd, FSCONFIG_SET_STRING, key, valuep, 0)
+}
+
+// FsconfigSetBinary is equivalent to fsconfig(2) called
+// with cmd == FSCONFIG_SET_BINARY.
+//
+// fd is the filesystem context to act upon.
+// key the parameter key to set.
+// value is the parameter value to set.
+func FsconfigSetBinary(fd int, key string, value []byte) (err error) {
+	if len(value) == 0 {
+		return EINVAL
+	}
+	return fsconfigCommon(fd, FSCONFIG_SET_BINARY, key, &value[0], len(value))
+}
+
+// FsconfigSetPath is equivalent to fsconfig(2) called
+// with cmd == FSCONFIG_SET_PATH.
+//
+// fd is the filesystem context to act upon.
+// key the parameter key to set.
+// path is a non-empty path for specified key.
+// atfd is a file descriptor at which to start lookup from or AT_FDCWD.
+func FsconfigSetPath(fd int, key string, path string, atfd int) (err error) {
+	var valuep *byte
+	if valuep, err = BytePtrFromString(path); err != nil {
+		return
+	}
+	return fsconfigCommon(fd, FSCONFIG_SET_PATH, key, valuep, atfd)
+}
+
+// FsconfigSetPathEmpty is equivalent to fsconfig(2) called
+// with cmd == FSCONFIG_SET_PATH_EMPTY. The same as
+// FconfigSetPath but with AT_PATH_EMPTY implied.
+func FsconfigSetPathEmpty(fd int, key string, path string, atfd int) (err error) {
+	var valuep *byte
+	if valuep, err = BytePtrFromString(path); err != nil {
+		return
+	}
+	return fsconfigCommon(fd, FSCONFIG_SET_PATH_EMPTY, key, valuep, atfd)
+}
+
+// FsconfigSetFd is equivalent to fsconfig(2) called
+// with cmd == FSCONFIG_SET_FD.
+//
+// fd is the filesystem context to act upon.
+// key the parameter key to set.
+// value is a file descriptor to be assigned to specified key.
+func FsconfigSetFd(fd int, key string, value int) (err error) {
+	return fsconfigCommon(fd, FSCONFIG_SET_FD, key, nil, value)
+}
+
+// FsconfigCreate is equivalent to fsconfig(2) called
+// with cmd == FSCONFIG_CMD_CREATE.
+//
+// fd is the filesystem context to act upon.
+func FsconfigCreate(fd int) (err error) {
+	return fsconfig(fd, FSCONFIG_CMD_CREATE, nil, nil, 0)
+}
+
+// FsconfigReconfigure is equivalent to fsconfig(2) called
+// with cmd == FSCONFIG_CMD_RECONFIGURE.
+//
+// fd is the filesystem context to act upon.
+func FsconfigReconfigure(fd int) (err error) {
+	return fsconfig(fd, FSCONFIG_CMD_RECONFIGURE, nil, nil, 0)
+}
+
 //sys	Getdents(fd int, buf []byte) (n int, err error) = SYS_GETDENTS64
 //sysnb	Getpgid(pid int) (pgid int, err error)