Keys: KEYCTL_SESSION_TO_PARENT needs TIF_NOTIFY_RESUME architecture support

As of commit ee18d64c ("KEYS: Add a keyctl to
install a process's session keyring on its parent [try #6]"), CONFIG_KEYS=y
fails to build on architectures that haven't implemented TIF_NOTIFY_RESUME yet:

security/keys/keyctl.c: In function 'keyctl_session_to_parent':
security/keys/keyctl.c:1312: error: 'TIF_NOTIFY_RESUME' undeclared (first use in this function)
security/keys/keyctl.c:1312: error: (Each undeclared identifier is reported only once
security/keys/keyctl.c:1312: error: for each function it appears in.)

Make KEYCTL_SESSION_TO_PARENT depend on TIF_NOTIFY_RESUME until
m68k, and xtensa have implemented it.
Signed-off-by: NGeert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: NJames Morris <jmorris@namei.org>
Acked-by: NMike Frysinger <vapier@gentoo.org>

security/keys/keyctl.c

@@ -1236,6 +1236,7 @@ long keyctl_get_security(key_serial_t keyid,
  */
 long keyctl_session_to_parent(void)
 {
+#ifdef TIF_NOTIFY_RESUME
 	struct task_struct *me, *parent;
 	const struct cred *mycred, *pcred;
 	struct cred *cred, *oldcred;
@@ -1326,6 +1327,15 @@ long keyctl_session_to_parent(void)
 error_keyring:
 	key_ref_put(keyring_r);
 	return ret;
+
+#else /* !TIF_NOTIFY_RESUME */
+	/*
+	 * To be removed when TIF_NOTIFY_RESUME has been implemented on
+	 * m68k/xtensa
+	 */
+#warning TIF_NOTIFY_RESUME not implemented
+	return -EOPNOTSUPP;
+#endif /* !TIF_NOTIFY_RESUME */
 }
 
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