Upgradeable loader (#13689)

programs/bpf/rust/upgraded/src/lib.rs

@@ -0,0 +1,16 @@
+//! @brief Example Rust-based BPF upgraded program
+
+extern crate solana_program;
+use solana_program::{
+    account_info::AccountInfo, entrypoint, entrypoint::ProgramResult, msg, pubkey::Pubkey,
+};
+
+entrypoint!(process_instruction);
+fn process_instruction(
+    _program_id: &Pubkey,
+    _accounts: &[AccountInfo],
+    _instruction_data: &[u8],
+) -> ProgramResult {
+    msg!("Upgraded program");
+    Err(43.into())
+}