rust/pv_core: Retrieve Secret UVC

Create the uvdevice-IOCTL functionality for the new Retrieve Secret UVC.

Reviewed-by: Christoph Schlameuss <schlameuss@linux.ibm.com>
Acked-by: Marc Hartmayer <marc@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

rust/pv_core/src/error.rs

@@ -4,6 +4,8 @@
 
 use std::path::PathBuf;
 
+use crate::uv::SecretId;
+
 /// Result type for this crate
 pub type Result<T, E = Error> = std::result::Result<T, E>;
 
@@ -70,6 +72,11 @@ pub enum Error {
     #[error("The attestation request does not specify a measurement size or measurement data.")]
     BinArcbNoMeasurement,
 
+    #[error(
+        "The secret with the ID {id} cannot be retrieved. The requested size is too large ({size})"
+    )]
+    InvalidRetrievableSecretType { id: SecretId, size: usize },
+
     // errors from other crates
     #[error(transparent)]
     Io(#[from] std::io::Error),