Direct entrypoint for execution (#7746)

sdk/src/instruction_processor_utils.rs

@@ -113,6 +113,12 @@ pub fn next_keyed_account<I: Iterator>(iter: &mut I) -> Result<I::Item, Instruct
     iter.next().ok_or(InstructionError::NotEnoughAccountKeys)
 }
 
+/// Return true if the first keyed_account is executable, used to determine if
+/// the loader should call a program's 'main'
+pub fn is_executable(keyed_accounts: &[KeyedAccount]) -> bool {
+    !keyed_accounts.is_empty() && keyed_accounts[0].account.executable
+}
+
 pub fn limited_deserialize<T>(data: &[u8]) -> Result<T, InstructionError>
 where
     T: serde::de::DeserializeOwned,

sdk/src/loader_instruction.rs

@@ -24,14 +24,6 @@ pub enum LoaderInstruction {
     ///
     /// The transaction must be signed by key[0]
     Finalize,
-
-    /// Invoke the "main" entrypoint with the given data.
-    ///
-    /// * key[0] - an executable account
-    InvokeMain {
-        #[serde(with = "serde_bytes")]
-        data: Vec<u8>,
-    },
 }
 
 pub fn write(