rust/pvimg: Add a Secure Execution header library and an example how to use

The new Rust port of genprotimg will have the name 'pvimg' as it has
more functionalities than the original genprotimg tool. As preparation
add a Secure Execution header library and an example how to use it. The
example can be used by the KVM-Unit-Tests for creating the Secure
Execution headers needed by the tests [1].

[1] See https://gitlab.com/kvm-unit-tests/kvm-unit-tests/-/commit/dc4f7106f363b27f57549d5d039b4804bbb6e67f
more information how to use.

Acked-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

rust/pv/src/crypto.rs

@@ -28,7 +28,6 @@ pub type Aes256GcmKey = Confidential<[u8; SymKeyType::AES_256_GCM_KEY_LEN]>;
 pub type Aes256XtsKey = Confidential<[u8; SymKeyType::AES_256_XTS_KEY_LEN]>;
 
 /// SHA-512 digest length (in bytes)
-#[allow(unused)]
 pub const SHA_512_HASH_LEN: usize = 64;
 
 #[allow(dead_code)]

rust/pv/src/lib.rs

@@ -90,7 +90,7 @@ pub mod request {
         crypto::{
             decrypt_aead, derive_aes256_gcm_key, encrypt_aead, gen_ec_key, random_array,
             AeadDecryptionResult, AeadEncryptionResult, Aes256GcmKey, Aes256XtsKey, SymKey,
-            SymKeyType,
+            SymKeyType, SHA_512_HASH_LEN,
         },
         req::{EcPubKeyCoord, Encrypt, Keyslot, ReqEncrCtx, Request},
         verify::{CertVerifier, HkdVerifier, NoVerifyHkd},