feat: runtime: Add read_only getter

runtime/src/runtime/fvm.rs

@@ -351,6 +351,10 @@ where
     fn base_fee(&self) -> TokenAmount {
         fvm::network::base_fee()
     }
+
+    fn read_only(&self) -> bool {
+        fvm::vm::read_only()
+    }
 }
 
 impl<B> Primitives for FvmRuntime<B>

runtime/src/runtime/mod.rs

@@ -245,6 +245,9 @@ pub trait Runtime: Primitives + Verifier + RuntimePolicy {
 
     /// Returns the gas base fee (cost per unit) for the current epoch.
     fn base_fee(&self) -> TokenAmount;
+
+    /// Returns true if the system is in read-only mode.
+    fn read_only(&self) -> bool;
 }
 
 /// Message information available to the actor about executing message.

runtime/src/test_utils.rs

@@ -1068,6 +1068,11 @@ impl<BS: Blockstore> Runtime for MockRuntime<BS> {
     fn base_fee(&self) -> TokenAmount {
         self.base_fee.clone()
     }
+
+    fn read_only(&self) -> bool {
+        // Unsupported for unit tests
+        false
+    }
 }
 
 impl<BS> Primitives for MockRuntime<BS> {

test_vm/src/lib.rs

@@ -447,6 +447,7 @@ impl<'bs> VM<'bs> {
             policy: &Policy::default(),
             subinvocations: RefCell::new(vec![]),
             actor_exit: RefCell::new(None),
+            read_only: false,
         };
         let res = new_ctx.invoke_actor();
 
@@ -576,6 +577,7 @@ pub struct InvocationCtx<'invocation, 'bs> {
     msg: InternalMessage,
     allow_side_effects: bool,
     caller_validated: bool,
+    read_only: bool,
     policy: &'invocation Policy,
     subinvocations: RefCell<Vec<InvocationTrace>>,
     actor_exit: RefCell<Option<ActorExit>>,
@@ -613,6 +615,14 @@ impl<'invocation, 'bs> InvocationCtx<'invocation, 'bs> {
             }
         };
 
+        // But only if we're not in read-only mode.
+        if self.read_only() {
+            return Err(ActorError::unchecked(
+                ExitCode::USR_READ_ONLY,
+                format!("cannot create actor {target} in read-only mode"),
+            ));
+        }
+
         let mut st = self.v.get_state::<InitState>(INIT_ACTOR_ADDR).unwrap();
         let (target_id, existing) = st.map_addresses_to_id(self.v.store, target, None).unwrap();
         assert!(!existing, "should never have existing actor when no f4 address is specified");
@@ -638,6 +648,7 @@ impl<'invocation, 'bs> InvocationCtx<'invocation, 'bs> {
                 policy: self.policy,
                 subinvocations: RefCell::new(vec![]),
                 actor_exit: RefCell::new(None),
+                read_only: false,
             };
             if is_account {
                 new_ctx.create_actor(*ACCOUNT_ACTOR_CODE_ID, target_id, None).unwrap();
@@ -892,8 +903,13 @@ impl<'invocation, 'bs> Runtime for InvocationCtx<'invocation, 'bs> {
         params: Option<IpldBlock>,
         value: TokenAmount,
         _gas_limit: Option<u64>,
-        _send_flags: SendFlags,
+        mut send_flags: SendFlags,
     ) -> Result<Response, ErrorNumber> {
+        // replicate FVM by silently propagating read only flag to subcalls
+        if self.read_only() {
+            send_flags.set(SendFlags::READ_ONLY, true)
+        }
+
         if !self.allow_side_effects {
             return Ok(Response { exit_code: ExitCode::SYS_ASSERTION_FAILED, return_data: None });
         }
@@ -908,6 +924,7 @@ impl<'invocation, 'bs> Runtime for InvocationCtx<'invocation, 'bs> {
             policy: self.policy,
             subinvocations: RefCell::new(vec![]),
             actor_exit: RefCell::new(None),
+            read_only: send_flags.read_only(),
         };
         let res = new_ctx.invoke_actor();
         let invoc = new_ctx.gather_trace(res.clone());
@@ -1031,6 +1048,10 @@ impl<'invocation, 'bs> Runtime for InvocationCtx<'invocation, 'bs> {
     fn base_fee(&self) -> TokenAmount {
         TokenAmount::zero()
     }
+
+    fn read_only(&self) -> bool {
+        self.read_only
+    }
 }
 
 impl Primitives for VM<'_> {