Add capabilities command to ROM.

Currently reports just a single bit representing functionality present in v1.0 of ROM.

common/Cargo.toml

@@ -8,6 +8,7 @@ edition = "2021"
 
 [dependencies]
 bitfield.workspace = true
+bitflags.workspace = true
 caliptra-drivers.workspace = true
 caliptra-image-types = { workspace = true, default-features = false }
 caliptra-registers.workspace = true

common/src/capabilities.rs

@@ -0,0 +1,40 @@
+/*++
+
+Licensed under the Apache-2.0 license.
+
+File Name:
+
+    capabilities.rs
+
+Abstract:
+
+    Capability bits
+
+--*/
+
+bitflags::bitflags! {
+    #[derive(Default, Copy, Clone, Debug)]
+    pub struct Capabilities : u128 {
+        // Represents base capabilities present in Caliptra ROM v1.0
+        const ROM_BASE = 0b0001;
+    }
+}
+
+impl Capabilities {
+    pub fn to_bytes(&self) -> [u8; 16] {
+        self.bits().to_be_bytes()
+    }
+}
+
+impl TryFrom<&[u8]> for Capabilities {
+    type Error = ();
+    fn try_from(value: &[u8]) -> Result<Self, Self::Error> {
+        if value.len() != 16 {
+            Err(())
+        } else {
+            let capabilities = u128::from_be_bytes(value.try_into().unwrap());
+            let caps = Capabilities::from_bits(capabilities);
+            caps.ok_or(())
+        }
+    }
+}

common/src/lib.rs

@@ -3,6 +3,7 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 pub mod boot_status;
+pub mod capabilities;
 pub mod checksum;
 pub mod crypto;
 pub mod dice;

common/src/mailbox_api.rs

@@ -28,6 +28,9 @@ impl CommandId {
     pub const SELF_TEST: Self = Self(0x4650_4C54); // "FPST"
     /// The shutdown command.
     pub const SHUTDOWN: Self = Self(0x4650_5344); // "FPSD"
+
+    // The capabilities command.
+    pub const CAPABILITIES: Self = Self(0x4341_5053); // "CAPS"
 }
 
 impl From<u32> for CommandId {

rom/dev/src/flow/cold_reset/fw_processor.rs

@@ -19,6 +19,7 @@ use crate::{cprintln, verifier::RomImageVerificationEnv};
 use crate::{pcr, wdt};
 use caliptra_cfi_derive::cfi_impl_fn;
 use caliptra_cfi_lib::{cfi_assert, cfi_assert_eq, cfi_launder};
+use caliptra_common::capabilities::Capabilities;
 use caliptra_common::mailbox_api::CommandId;
 use caliptra_common::{cprint, memory_layout::MAN1_ORG, FuseLogEntryId, RomBootStatus::*};
 use caliptra_drivers::*;
@@ -137,6 +138,13 @@ impl FirmwareProcessor {
                         txn.start_txn().complete(false)?;
                         continue;
                     }
+                    CommandId::CAPABILITIES => {
+                        let mut capabilities = Capabilities::default();
+                        capabilities |= Capabilities::ROM_BASE;
+
+                        txn.start_txn().send_response(&capabilities.to_bytes())?;
+                        continue;
+                    }
                     CommandId::FIRMWARE_LOAD => {
                         // Re-borrow mailbox to work around https://github.com/rust-lang/rust/issues/54663
                         let txn = mbox

rom/dev/tests/test_capabilities.rs

@@ -0,0 +1,23 @@
+// Licensed under the Apache-2.0 license
+
+use caliptra_builder::ImageOptions;
+use caliptra_common::{capabilities::Capabilities, mailbox_api::CommandId};
+use caliptra_hw_model::{Fuses, HwModel};
+use zerocopy::AsBytes;
+
+pub mod helpers;
+
+#[test]
+fn test_capabilities() {
+    let (mut hw, _image_bundle) =
+        helpers::build_hw_model_and_image_bundle(Fuses::default(), ImageOptions::default());
+
+    let response = hw
+        .mailbox_execute(CommandId::CAPABILITIES.into(), &[])
+        .unwrap()
+        .unwrap();
+
+    let caps = Capabilities::try_from(response.as_bytes()).unwrap();
+
+    assert!(caps.contains(Capabilities::ROM_BASE));
+}