KEYS: Add an iovec version of KEYCTL_INSTANTIATE

Add a keyctl op (KEYCTL_INSTANTIATE_IOV) that is like KEYCTL_INSTANTIATE, but
takes an iovec array and concatenates the data in-kernel into one buffer.
Since the KEYCTL_INSTANTIATE copies the data anyway, this isn't too much of a
problem.

Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <jmorris@namei.org>
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index d5ed94d..b46b75b 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2138,6 +2138,11 @@
 	def_bool y
 	depends on COMPAT && SYSVIPC
 
+config KEYS_COMPAT
+	bool
+	depends on COMPAT && KEYS
+	default y
+
 endmenu