Add return data implementation

This consists of:
 - syscalls
 - passing return data from invoked to invoker
 - printing to stable log
 - rust and C SDK changes

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

@@ -10,7 +10,7 @@ use solana_program::{
     entrypoint,
     entrypoint::{ProgramResult, MAX_PERMITTED_DATA_INCREASE},
     msg,
-    program::{invoke, invoke_signed},
+    program::{get_return_data, invoke, invoke_signed, set_return_data},
     program_error::ProgramError,
     pubkey::{Pubkey, PubkeyError},
     system_instruction,
@@ -394,6 +394,27 @@ fn process_instruction(
                     assert_eq!(data[i], i as u8);
                 }
             }
+
+            msg!("Test return data via invoked");
+            {
+                // this should be cleared on entry, the invoked tests for this
+                set_return_data(b"x");
+
+                let instruction = create_instruction(
+                    *accounts[INVOKED_PROGRAM_INDEX].key,
+                    &[(accounts[ARGUMENT_INDEX].key, false, true)],
+                    vec![SET_RETURN_DATA],
+                );
+                let _ = invoke(&instruction, accounts);
+
+                assert_eq!(
+                    get_return_data(),
+                    Some((
+                        *accounts[INVOKED_PROGRAM_INDEX].key,
+                        b"Set by invoked".to_vec()
+                    ))
+                );
+            }
         }
         TEST_PRIVILEGE_ESCALATION_SIGNER => {
             msg!("Test privilege escalation signer");

programs/bpf/rust/invoked/src/instruction.rs

@@ -18,6 +18,7 @@ pub const VERIFY_PRIVILEGE_DEESCALATION_ESCALATION_SIGNER: u8 = 9;
 pub const VERIFY_PRIVILEGE_DEESCALATION_ESCALATION_WRITABLE: u8 = 10;
 pub const WRITE_ACCOUNT: u8 = 11;
 pub const CREATE_AND_INIT: u8 = 12;
+pub const SET_RETURN_DATA: u8 = 13;
 
 pub fn create_instruction(
     program_id: Pubkey,

programs/bpf/rust/invoked/src/processor.rs

@@ -8,7 +8,7 @@ use solana_program::{
     bpf_loader, entrypoint,
     entrypoint::{ProgramResult, MAX_PERMITTED_DATA_INCREASE},
     msg,
-    program::{invoke, invoke_signed},
+    program::{get_return_data, invoke, invoke_signed, set_return_data},
     program_error::ProgramError,
     pubkey::Pubkey,
     system_instruction,
@@ -27,6 +27,8 @@ fn process_instruction(
         return Ok(());
     }
 
+    assert_eq!(get_return_data(), None);
+
     match instruction_data[0] {
         VERIFY_TRANSLATIONS => {
             msg!("verify data translations");
@@ -286,6 +288,11 @@ fn process_instruction(
                 }
             }
         }
+        SET_RETURN_DATA => {
+            msg!("Set return data");
+
+            set_return_data(b"Set by invoked");
+        }
         _ => panic!(),
     }