Decrease size of ModelEmulated from ~50k to 192 bytes.

This should cut back on stack consumption and reduce memcpy bloat
when running tests.

Cargo.toml

@@ -112,7 +112,7 @@ caliptra-emu-cpu = { path = "sw-emulator/lib/cpu" }
 caliptra-emu-crypto = { path = "sw-emulator/lib/crypto" }
 caliptra-emu-derive = { path = "sw-emulator/lib/derive" }
 caliptra-emu-periph = { path = "sw-emulator/lib/periph" }
-caliptra-emu-types = { path = "sw-emulator/lib/types" }
+caliptra-emu-types = { path = "sw-emulator/lib/types", features = ["std"] }
 caliptra-error = { path = "error", default-features = false }
 caliptra-fpga-boss = { path = "ci-tools/fpga-boss" }
 caliptra-gen-linker-scripts = { path = "cpu/gen" }

hw-model/src/model_emulated.rs

@@ -54,7 +54,7 @@ impl<'a> Bus for EmulatedApbBus<'a> {
 
 /// Emulated model
 pub struct ModelEmulated {
-    cpu: Cpu<BusLogger<CaliptraRootBus>>,
+    cpu: Box<Cpu<BusLogger<CaliptraRootBus>>>,
     soc_to_caliptra_bus: SocToCaliptraBus,
     output: Output,
     trace_fn: Option<Box<InstrTracer<'static>>>,
@@ -187,7 +187,7 @@ impl HwModel for ModelEmulated {
             dccm_dest.copy_from_slice(params.dccm);
         }
         let soc_to_caliptra_bus = root_bus.soc_to_caliptra_bus();
-        let cpu = Cpu::new(BusLogger::new(root_bus), clock);
+        let cpu = Box::new(Cpu::new(BusLogger::new(root_bus), clock));
 
         let mut hasher = DefaultHasher::new();
         std::hash::Hash::hash_slice(params.rom, &mut hasher);

sw-emulator/lib/cpu/src/csr_file.rs

@@ -102,7 +102,7 @@ impl Csr {
 /// Configuration and status register file
 pub struct CsrFile {
     /// CSRS
-    csrs: [Csr; CsrFile::CSR_COUNT],
+    csrs: Box<[Csr; CsrFile::CSR_COUNT]>,
     /// Timer
     timer: Timer,
 }
@@ -114,7 +114,10 @@ impl CsrFile {
     /// Create a new Configuration and status register file
     pub fn new(clock: &Clock) -> Self {
         let mut csrs = Self {
-            csrs: [Csr::new(0, 0); CsrFile::CSR_COUNT],
+            csrs: vec![Csr::new(0, 0); CsrFile::CSR_COUNT]
+                .try_into()
+                .map_err(|_| ())
+                .unwrap(),
             timer: Timer::new(clock),
         };
 

sw-emulator/lib/periph/src/root_bus.rs

@@ -268,7 +268,7 @@ pub struct CaliptraRootBus {
     pub sha256: HashSha256,
 
     #[peripheral(offset = 0x1003_0000, mask = 0x0000_7fff)] // TODO update when known
-    pub ml_dsa87: MlDsa87,
+    pub ml_dsa87: Box<MlDsa87>,
 
     #[peripheral(offset = 0x4000_0000, mask = 0x0fff_ffff)]
     pub iccm: Iccm,
@@ -331,7 +331,7 @@ impl CaliptraRootBus {
             key_vault: key_vault.clone(),
             sha512,
             sha256: HashSha256::new(clock),
-            ml_dsa87: MlDsa87::new(clock),
+            ml_dsa87: Box::new(MlDsa87::new(clock)),
             iccm,
             dccm: Ram::new(vec![0; Self::DCCM_SIZE]),
             uart: Uart::new(),

sw-emulator/lib/types/Cargo.toml

@@ -8,3 +8,6 @@ edition = "2021"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
+
+[features]
+std = []

sw-emulator/lib/types/src/bus.rs

@@ -75,3 +75,26 @@ pub trait Bus {
         // By default, do nothing
     }
 }
+
+#[cfg(feature = "std")]
+impl<T: Bus> Bus for Box<T> {
+    fn read(&mut self, size: RvSize, addr: RvAddr) -> Result<RvData, BusError> {
+        T::read(self, size, addr)
+    }
+
+    fn write(&mut self, size: RvSize, addr: RvAddr, val: RvData) -> Result<(), BusError> {
+        T::write(self, size, addr, val)
+    }
+
+    fn poll(&mut self) {
+        T::poll(self)
+    }
+
+    fn warm_reset(&mut self) {
+        T::warm_reset(self)
+    }
+
+    fn update_reset(&mut self) {
+        T::update_reset(self)
+    }
+}

sw-emulator/lib/types/src/lib.rs

@@ -11,7 +11,7 @@ Abstract:
     File contains exports for for Caliptra Emulator Types library.
 
 --*/
-#![cfg_attr(not(test), no_std)]
+#![cfg_attr(not(any(test, feature = "std")), no_std)]
 
 pub mod bus;
 mod exception;