Reduce stack usage for DPE command input structures

Use zerocopy to pass references to DPE command structures, using the
input slice as backing storage. This saves a few hundred bytes over
copying these values to structs on the stack.

dpe/src/commands/certify_key.rs

@@ -355,7 +355,7 @@ mod tests {
  .to_vec();
  command.extend(TEST_CERTIFY_KEY_CMD.as_bytes());
  assert_eq!(
- Ok(Command::CertifyKey(TEST_CERTIFY_KEY_CMD)),
+ Ok(Command::CertifyKey(&TEST_CERTIFY_KEY_CMD)),
  Command::deserialize(&command)
  );
  }

dpe/src/commands/derive_context.rs

@@ -390,7 +390,7 @@ mod tests {
  .to_vec();
  command.extend(TEST_DERIVE_CONTEXT_CMD.as_bytes());
  assert_eq!(
- Ok(Command::DeriveContext(TEST_DERIVE_CONTEXT_CMD)),
+ Ok(Command::DeriveContext(&TEST_DERIVE_CONTEXT_CMD)),
  Command::deserialize(&command)
  );
  }

dpe/src/commands/destroy_context.rs

@@ -119,7 +119,7 @@ mod tests {
  .to_vec();
  command.extend(TEST_DESTROY_CTX_CMD.as_bytes());
  assert_eq!(
- Ok(Command::DestroyCtx(TEST_DESTROY_CTX_CMD)),
+ Ok(Command::DestroyCtx(&TEST_DESTROY_CTX_CMD)),
  Command::deserialize(&command)
  );
  }

dpe/src/commands/get_certificate_chain.rs

@@ -74,7 +74,9 @@ mod tests {
  .to_vec();
  command.extend(TEST_GET_CERTIFICATE_CHAIN_CMD.as_bytes());
  assert_eq!(
- Ok(Command::GetCertificateChain(TEST_GET_CERTIFICATE_CHAIN_CMD)),
+ Ok(Command::GetCertificateChain(
+ &TEST_GET_CERTIFICATE_CHAIN_CMD
+ )),
  Command::deserialize(&command)
  );
  }

dpe/src/commands/initialize_context.rs

@@ -132,7 +132,7 @@ mod tests {
  .to_vec();
  command.extend(TEST_INIT_CTX_CMD.as_bytes());
  assert_eq!(
- Ok(Command::InitCtx(TEST_INIT_CTX_CMD)),
+ Ok(Command::InitCtx(&TEST_INIT_CTX_CMD)),
  Command::deserialize(&command)
  );
  }

dpe/src/commands/mod.rs

@@ -20,7 +20,7 @@ use crate::{
  DPE_PROFILE,
 };
 use core::mem::size_of;
-use zerocopy::FromBytes;
+use zerocopy::{FromBytes, Immutable, KnownLayout};
 
 mod certify_key;
 mod derive_context;
@@ -32,19 +32,19 @@ mod rotate_context;
 mod sign;
 
 #[derive(Debug, PartialEq, Eq)]
-pub enum Command {
+pub enum Command<'a> {
  GetProfile,
- InitCtx(InitCtxCmd),
- DeriveContext(DeriveContextCmd),
- CertifyKey(CertifyKeyCmd),
- Sign(SignCmd),
+ InitCtx(&'a InitCtxCmd),
+ DeriveContext(&'a DeriveContextCmd),
+ CertifyKey(&'a CertifyKeyCmd),
+ Sign(&'a SignCmd),
  #[cfg(not(feature = "disable_rotate_context"))]
- RotateCtx(RotateCtxCmd),
- DestroyCtx(DestroyCtxCmd),
- GetCertificateChain(GetCertificateChainCmd),
+ RotateCtx(&'a RotateCtxCmd),
+ DestroyCtx(&'a DestroyCtxCmd),
+ GetCertificateChain(&'a GetCertificateChainCmd),
 }
 
-impl Command {
+impl Command<'_> {
  pub const GET_PROFILE: u32 = 0x01;
  pub const INITIALIZE_CONTEXT: u32 = 0x07;
  pub const DERIVE_CONTEXT: u32 = 0x08;
@@ -80,17 +80,17 @@ impl Command {
  }
  }
 
- fn parse_command<T: FromBytes>(
- build: impl FnOnce(T) -> Command,
- bytes: &[u8],
+ fn parse_command<'a, T: FromBytes + KnownLayout + Immutable + 'a>(
+ build: impl FnOnce(&'a T) -> Command,
+ bytes: &'a [u8],
  ) -> Result<Command, DpeErrorCode> {
  let (prefix, _remaining_bytes) =
- T::read_from_prefix(bytes).map_err(|_| DpeErrorCode::InvalidArgument)?;
+ T::ref_from_prefix(bytes).map_err(|_| DpeErrorCode::InvalidArgument)?;
  Ok(build(prefix))
  }
 }
 
-impl From<Command> for u32 {
+impl From<Command<'_>> for u32 {
  fn from(cmd: Command) -> u32 {
  match cmd {
  Command::GetProfile => Command::GET_PROFILE,

dpe/src/commands/rotate_context.rs

@@ -151,7 +151,7 @@ mod tests {
  .to_vec();
  command.extend(TEST_ROTATE_CTX_CMD.as_bytes());
  assert_eq!(
- Ok(Command::RotateCtx(TEST_ROTATE_CTX_CMD)),
+ Ok(Command::RotateCtx(&TEST_ROTATE_CTX_CMD)),
  Command::deserialize(&command)
  );
  }

dpe/src/commands/sign.rs

@@ -230,7 +230,7 @@ mod tests {
  let mut command = CommandHdr::new_for_test(Command::SIGN).as_bytes().to_vec();
  command.extend(TEST_SIGN_CMD.as_bytes());
  assert_eq!(
- Ok(Command::Sign(TEST_SIGN_CMD)),
+ Ok(Command::Sign(&TEST_SIGN_CMD)),
  Command::deserialize(&command)
  );
  }