Optimize account copies and use RefCell to handle duplicate accounts in BPF programs (#7958)

programs/bpf/c/src/dup_accounts/dup_accounts.c

@@ -0,0 +1,57 @@
+/**
+ * @brief Example C-based BPF program that exercises duplicate keyed ka
+ * passed to it
+ */
+#include <solana_sdk.h>
+
+/**
+ * Custom error for when input serialization fails
+ */
+
+extern uint32_t entrypoint(const uint8_t *input) {
+  #define FAILURE 1
+  #define INVALID_INPUT 2
+
+  SolKeyedAccount ka[4];
+  SolParameters params = (SolParameters) { .ka = ka };
+
+  if (!sol_deserialize(input, &params, SOL_ARRAY_SIZE(ka))) {
+    return INVALID_INPUT;
+  }
+
+  switch (params.data[0]) {
+      case(1):
+          sol_log("modify first account userdata");
+          ka[2].userdata[0] = 1;
+          break;
+      case(2):
+          sol_log("modify first account userdata");
+          ka[3].userdata[0] = 2;
+          break;
+      case(3):
+          sol_log("modify both account userdata");
+          ka[2].userdata[0] += 1;
+          ka[3].userdata[0] += 2;
+          break;
+      case(4):
+          sol_log("modify first account lamports");
+          *ka[1].lamports -= 1;
+          *ka[2].lamports += 1;
+          break;
+      case(5):
+          sol_log("modify first account lamports");
+          *ka[1].lamports -= 2;
+          *ka[3].lamports += 2;
+          break;
+      case(6):
+          sol_log("modify both account lamports");
+          *ka[1].lamports -= 3;
+          *ka[2].lamports += 1;
+          *ka[3].lamports += 2;
+          break;
+      default:
+          sol_log("Unrecognized command");
+          return FAILURE;
+  }
+  return SUCCESS;
+}

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

@@ -12,32 +12,32 @@ fn process_instruction(_program_id: &Pubkey, accounts: &mut [AccountInfo], data:
     match data[0] {
         1 => {
             info!("modify first account data");
-            accounts[2].data[0] = 1;
+            accounts[2].m.borrow_mut().data[0] = 1;
         }
         2 => {
             info!("modify first account data");
-            accounts[3].data[0] = 2;
+            accounts[3].m.borrow_mut().data[0] = 2;
         }
         3 => {
-            info!("modify both account data, should fail");
-            accounts[2].data[0] = 1;
-            accounts[3].data[0] = 2;
+            info!("modify both account data");
+            accounts[2].m.borrow_mut().data[0] += 1;
+            accounts[3].m.borrow_mut().data[0] += 2;
         }
         4 => {
             info!("modify first account lamports");
-            *accounts[1].lamports -= 1;
-            *accounts[2].lamports += 1;
+            *accounts[1].m.borrow_mut().lamports -= 1;
+            *accounts[2].m.borrow_mut().lamports += 1;
         }
         5 => {
             info!("modify first account lamports");
-            *accounts[1].lamports -= 2;
-            *accounts[3].lamports += 2;
+            *accounts[1].m.borrow_mut().lamports -= 2;
+            *accounts[3].m.borrow_mut().lamports += 2;
         }
         6 => {
-            info!("modify both account lamports, should fail");
-            *accounts[1].lamports -= 1;
-            *accounts[2].lamports += 1;
-            *accounts[3].lamports += 2;
+            info!("modify both account lamports");
+            *accounts[1].m.borrow_mut().lamports -= 3;
+            *accounts[2].m.borrow_mut().lamports += 1;
+            *accounts[3].m.borrow_mut().lamports += 2;
         }
         _ => {
             info!("Unrecognized command");

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

@@ -8,7 +8,7 @@ fn process_instruction(_program_id: &Pubkey, accounts: &mut [AccountInfo], _data
     // account 0 is the mint and not owned by this program, any debit of its lamports
     // should result in a failed program execution.  Test to ensure that this debit
     // is seen by the runtime and fails as expected
-    *accounts[0].lamports -= 1;
+    *accounts[0].m.borrow_mut().lamports -= 1;
 
     SUCCESS
 }

programs/bpf/tests/programs.rs

@@ -27,10 +27,14 @@ mod bpf {
     mod bpf_c {
         use super::*;
         use solana_runtime::loader_utils::create_invoke_instruction;
+        use solana_sdk::account::Account;
         use solana_sdk::bpf_loader;
         use solana_sdk::client::SyncClient;
+        use solana_sdk::instruction::{AccountMeta, Instruction};
         use solana_sdk::signature::KeypairUtil;
         use std::io::Read;
+        use std::sync::Arc;
+        use solana_sdk::pubkey::Pubkey;
 
         #[test]
         fn test_program_bpf_c() {
@@ -72,6 +76,81 @@ mod bpf {
                 }
             }
         }
+
+        #[test]
+        fn test_program_bpf_c_duplicate_accounts() {
+            solana_logger::setup();
+
+            let filename = create_bpf_path("dup_accounts");
+            let mut file = File::open(filename).unwrap();
+            let mut elf = Vec::new();
+            file.read_to_end(&mut elf).unwrap();
+
+            let GenesisConfigInfo {
+                genesis_config,
+                mint_keypair,
+                ..
+            } = create_genesis_config(50);
+
+            let bank = Arc::new(Bank::new(&genesis_config));
+            let bank_client = BankClient::new_shared(&bank);
+            let program_id = load_program(&bank_client, &mint_keypair, &bpf_loader::id(), elf);
+
+            let payee_account = Account::new(10, 1, &program_id);
+            let payee_pubkey = Pubkey::new_rand();
+            bank.store_account(&payee_pubkey, &payee_account);
+
+            let account = Account::new(10, 1, &program_id);
+            let pubkey = Pubkey::new_rand();
+            let account_metas = vec![
+                AccountMeta::new(mint_keypair.pubkey(), true),
+                AccountMeta::new(payee_pubkey, false),
+                AccountMeta::new(pubkey, false),
+                AccountMeta::new(pubkey, false),
+            ];
+
+            bank.store_account(&pubkey, &account);
+            let instruction = Instruction::new(program_id, &1u8, account_metas.clone());
+            let result = bank_client.send_instruction(&mint_keypair, instruction);
+            let data = bank_client.get_account_data(&pubkey).unwrap().unwrap();
+            assert!(result.is_ok());
+            assert_eq!(data[0], 1);
+
+            bank.store_account(&pubkey, &account);
+            let instruction = Instruction::new(program_id, &2u8, account_metas.clone());
+            let result = bank_client.send_instruction(&mint_keypair, instruction);
+            let data = bank_client.get_account_data(&pubkey).unwrap().unwrap();
+            assert!(result.is_ok());
+            assert_eq!(data[0], 2);
+
+            bank.store_account(&pubkey, &account);
+            let instruction = Instruction::new(program_id, &3u8, account_metas.clone());
+            let result = bank_client.send_instruction(&mint_keypair, instruction);
+            let data = bank_client.get_account_data(&pubkey).unwrap().unwrap();
+            assert!(result.is_ok());
+            assert_eq!(data[0], 3);
+
+            bank.store_account(&pubkey, &account);
+            let instruction = Instruction::new(program_id, &4u8, account_metas.clone());
+            let result = bank_client.send_instruction(&mint_keypair, instruction);
+            let lamports = bank_client.get_balance(&pubkey).unwrap();
+            assert!(result.is_ok());
+            assert_eq!(lamports, 11);
+
+            bank.store_account(&pubkey, &account);
+            let instruction = Instruction::new(program_id, &5u8, account_metas.clone());
+            let result = bank_client.send_instruction(&mint_keypair, instruction);
+            let lamports = bank_client.get_balance(&pubkey).unwrap();
+            assert!(result.is_ok());
+            assert_eq!(lamports, 12);
+
+            bank.store_account(&pubkey, &account);
+            let instruction = Instruction::new(program_id, &6u8, account_metas.clone());
+            let result = bank_client.send_instruction(&mint_keypair, instruction);
+            let lamports = bank_client.get_balance(&pubkey).unwrap();
+            assert!(result.is_ok());
+            assert_eq!(lamports, 13);
+        }
     }
 
     #[cfg(feature = "bpf_rust")]
@@ -193,7 +272,9 @@ mod bpf {
             bank.store_account(&pubkey, &account);
             let instruction = Instruction::new(program_id, &3u8, account_metas.clone());
             let result = bank_client.send_instruction(&mint_keypair, instruction);
-            assert!(!result.is_ok());
+            let data = bank_client.get_account_data(&pubkey).unwrap().unwrap();
+            assert!(result.is_ok());
+            assert_eq!(data[0], 3);
 
             bank.store_account(&pubkey, &account);
             let instruction = Instruction::new(program_id, &4u8, account_metas.clone());
@@ -212,7 +293,9 @@ mod bpf {
             bank.store_account(&pubkey, &account);
             let instruction = Instruction::new(program_id, &6u8, account_metas.clone());
             let result = bank_client.send_instruction(&mint_keypair, instruction);
-            assert!(!result.is_ok());
+            let lamports = bank_client.get_balance(&pubkey).unwrap();
+            assert!(result.is_ok());
+            assert_eq!(lamports, 13);
         }
     }
 }

programs/bpf_loader/src/lib.rs

@@ -8,7 +8,6 @@ use log::*;
 use solana_rbpf::{memory_region::MemoryRegion, EbpfVm};
 use solana_sdk::{
     account::KeyedAccount,
-    hash::{Hash, Hasher},
     instruction::InstructionError,
     instruction_processor_utils::{is_executable, limited_deserialize, next_keyed_account},
     loader_instruction::LoaderInstruction,
@@ -16,7 +15,6 @@ use solana_sdk::{
     sysvar::rent,
 };
 use std::{
-    collections::HashMap,
     convert::TryFrom,
     io::{prelude::*, Error},
     mem,
@@ -46,6 +44,16 @@ pub fn check_elf(prog: &[u8]) -> Result<(), Error> {
     Ok(())
 }
 
+/// Look for a duplicate account and return its position if found
+pub fn is_dup(accounts: &[KeyedAccount], keyed_account: &KeyedAccount) -> (bool, usize) {
+    for (i, account) in accounts.iter().enumerate() {
+        if account == keyed_account {
+            return (true, i);
+        }
+    }
+    (false, 0)
+}
+
 pub fn serialize_parameters(
     program_id: &Pubkey,
     keyed_accounts: &[KeyedAccount],
@@ -56,16 +64,22 @@ pub fn serialize_parameters(
     let mut v: Vec<u8> = Vec::new();
     v.write_u64::<LittleEndian>(keyed_accounts.len() as u64)
         .unwrap();
-    for keyed_account in keyed_accounts.iter() {
-        v.write_u64::<LittleEndian>(keyed_account.signer_key().is_some() as u64)
-            .unwrap();
-        v.write_all(keyed_account.unsigned_key().as_ref()).unwrap();
-        v.write_u64::<LittleEndian>(keyed_account.lamports()?)
-            .unwrap();
-        v.write_u64::<LittleEndian>(keyed_account.data_len()? as u64)
-            .unwrap();
-        v.write_all(&keyed_account.try_account_ref()?.data).unwrap();
-        v.write_all(keyed_account.owner()?.as_ref()).unwrap();
+    for (i, keyed_account) in keyed_accounts.iter().enumerate() {
+        let (is_dup, position) = is_dup(&keyed_accounts[..i], keyed_account);
+        if is_dup {
+            v.write_u8(position as u8).unwrap();
+        } else {
+            v.write_u8(0).unwrap();
+            v.write_u64::<LittleEndian>(keyed_account.signer_key().is_some() as u64)
+                .unwrap();
+            v.write_all(keyed_account.unsigned_key().as_ref()).unwrap();
+            v.write_u64::<LittleEndian>(keyed_account.lamports()?)
+                .unwrap();
+            v.write_u64::<LittleEndian>(keyed_account.data_len()? as u64)
+                .unwrap();
+            v.write_all(&keyed_account.try_account_ref()?.data).unwrap();
+            v.write_all(keyed_account.owner()?.as_ref()).unwrap();
+        }
     }
     v.write_u64::<LittleEndian>(data.len() as u64).unwrap();
     v.write_all(data).unwrap();
@@ -79,63 +93,25 @@ pub fn deserialize_parameters(
 ) -> Result<(), InstructionError> {
     assert_eq!(32, mem::size_of::<Pubkey>());
 
-    let calculate_hash = |lamports: u64, data: &[u8]| -> Hash {
-        let mut hasher = Hasher::default();
-        let mut buf = [0u8; 8];
-        LittleEndian::write_u64(&mut buf[..], lamports);
-        hasher.hash(&buf);
-        hasher.hash(data);
-        hasher.result()
-    };
-
-    // remember any duplicate accounts
-    let mut map: HashMap<Pubkey, (Hash, bool)> = HashMap::new();
-    for (i, keyed_account) in keyed_accounts.iter().enumerate() {
-        if keyed_accounts[i + 1..].contains(keyed_account)
-            && !map.contains_key(keyed_account.unsigned_key())
-        {
-            let hash = calculate_hash(
-                keyed_account.lamports()?,
-                &keyed_account.try_account_ref()?.data,
-            );
-            map.insert(*keyed_account.unsigned_key(), (hash, false));
-        }
-    }
-
-    let mut start = mem::size_of::<u64>();
+    let mut start = mem::size_of::<u64>(); // number of accounts
     for keyed_account in keyed_accounts.iter() {
-        start += mem::size_of::<u64>() // signer_key boolean
-            + mem::size_of::<Pubkey>(); // pubkey
-        let lamports = LittleEndian::read_u64(&buffer[start..]);
-        start += mem::size_of::<u64>() // lamports
-            + mem::size_of::<u64>(); // length tag
-        let end = start + keyed_account.data_len()?;
-        let data_start = start;
-        let data_end = end;
-
-        // if duplicate, modified, and dirty, then bail
-        let mut do_update = true;
-        if let Some((hash, is_dirty)) = map.get_mut(keyed_account.unsigned_key()) {
-            let new_hash = calculate_hash(lamports, &buffer[data_start..data_end]);
-            if *hash != new_hash {
-                if *is_dirty {
-                    return Err(InstructionError::DuplicateAccountOutOfSync);
-                }
-                *is_dirty = true; // fail if modified again
-            } else {
-                do_update = false; // no changes, don't need to update account
-            }
-        }
-        if do_update {
-            keyed_account.try_account_ref_mut()?.lamports = lamports;
+        let duplicate = buffer[start] != 0; // duplicate info
+        start += 1;
+        if !duplicate {
+            start += mem::size_of::<u64>(); // is_signer
+            start += mem::size_of::<Pubkey>(); // pubkey
+            keyed_account.try_account_ref_mut()?.lamports =
+                LittleEndian::read_u64(&buffer[start..]);
+            start += mem::size_of::<u64>() // lamports
+                + mem::size_of::<u64>(); // data length
+            let end = start + keyed_account.data_len()?;
             keyed_account
                 .try_account_ref_mut()?
                 .data
-                .clone_from_slice(&buffer[data_start..data_end]);
+                .clone_from_slice(&buffer[start..end]);
+            start += keyed_account.data_len()? // data
+                + mem::size_of::<Pubkey>(); // owner
         }
-
-        start += keyed_account.data_len()? // data
-            + mem::size_of::<Pubkey>(); // owner
     }
     Ok(())
 }

sdk/bpf/c/inc/solana_sdk.h

@@ -226,31 +226,42 @@ SOL_FN_PREFIX bool sol_deserialize(
     return false;
   }
   params->ka_num = *(uint64_t *) input;
-  if (ka_num < *(uint64_t *) input) {
+  input += sizeof(uint64_t);
+  if (ka_num < params->ka_num) {
     return false;
   }
 
-  input += sizeof(uint64_t);
   for (int i = 0; i < params->ka_num; i++) {
-    // key
-    params->ka[i].is_signer = *(uint64_t *) input != 0;
-    input += sizeof(uint64_t);
-    params->ka[i].key = (SolPubkey *) input;
-    input += sizeof(SolPubkey);
+    uint8_t dup_info = input[0];
+    input += sizeof(uint8_t);
+    if (dup_info == 0) {
+      // key
+      params->ka[i].is_signer = *(uint64_t *) input != 0;
+      input += sizeof(uint64_t);
+      params->ka[i].key = (SolPubkey *) input;
+      input += sizeof(SolPubkey);
 
-    // lamports
-    params->ka[i].lamports = (uint64_t *) input;
-    input += sizeof(uint64_t);
+      // lamports
+      params->ka[i].lamports = (uint64_t *) input;
+      input += sizeof(uint64_t);
 
-    // account userdata
-    params->ka[i].userdata_len = *(uint64_t *) input;
-    input += sizeof(uint64_t);
-    params->ka[i].userdata = (uint8_t *) input;
-    input += params->ka[i].userdata_len;
+      // account userdata
+      params->ka[i].userdata_len = *(uint64_t *) input;
+      input += sizeof(uint64_t);
+      params->ka[i].userdata = (uint8_t *) input;
+      input += params->ka[i].userdata_len;
 
-    // owner
-    params->ka[i].owner = (SolPubkey *) input;
-    input += sizeof(SolPubkey);
+      // owner
+      params->ka[i].owner = (SolPubkey *) input;
+      input += sizeof(SolPubkey);
+    } else {
+      params->ka[i].is_signer = params->ka[dup_info].is_signer;
+      params->ka[i].key = params->ka[dup_info].key;
+      params->ka[i].lamports = params->ka[dup_info].lamports;
+      params->ka[i].userdata_len = params->ka[dup_info].userdata_len;
+      params->ka[i].userdata = params->ka[dup_info].userdata;
+      params->ka[i].owner = params->ka[dup_info].owner;
+    }
   }
 
   params->data_len = *(uint64_t *) input;

sdk/src/account_info.rs

@@ -1,33 +1,46 @@
 use crate::{account::Account, pubkey::Pubkey};
-use std::{cmp, fmt};
+use std::{
+    cell::{Ref, RefCell, RefMut},
+    cmp, fmt,
+    rc::Rc,
+};
 
-/// AccountInfo
-pub struct AccountInfo<'a> {
-    /// Public key of the account
-    pub key: &'a Pubkey,
-    /// Was the transaction signed by this account's public key?
-    pub is_signer: bool,
+/// Account information that is mutable by a program
+pub struct AccountInfoMut<'a> {
     /// Number of lamports owned by this account
     pub lamports: &'a mut u64,
     /// On-chain data within this account
     pub data: &'a mut [u8],
+}
+/// Account information
+#[derive(Clone)]
+pub struct AccountInfo<'a> {
+    /// Public key of the account
+    pub key: &'a Pubkey,
+    // Was the transaction signed by this account's public key?
+    pub is_signer: bool,
+    /// Account members that are mutable by the program
+    pub m: Rc<RefCell<AccountInfoMut<'a>>>,
     /// Program that owns this account
     pub owner: &'a Pubkey,
 }
 
 impl<'a> fmt::Debug for AccountInfo<'a> {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        let data_len = cmp::min(64, self.data.len());
+        let data_len = cmp::min(64, self.m.borrow().data.len());
         let data_str = if data_len > 0 {
-            format!(" data: {}", hex::encode(self.data[..data_len].to_vec()))
+            format!(
+                " data: {}",
+                hex::encode(self.m.borrow().data[..data_len].to_vec())
+            )
         } else {
             "".to_string()
         };
         write!(
             f,
             "AccountInfo {{ lamports: {} data.len: {} owner: {} {} }}",
-            self.lamports,
-            self.data.len(),
+            self.m.borrow().lamports,
+            self.m.borrow().data.len(),
             self.owner,
             data_str,
         )
@@ -47,6 +60,22 @@ impl<'a> AccountInfo<'a> {
         self.key
     }
 
+    pub fn try_account_ref(&'a self) -> Result<Ref<AccountInfoMut>, u32> {
+        self.try_borrow()
+    }
+
+    pub fn try_account_ref_mut(&'a self) -> Result<RefMut<'a, AccountInfoMut>, u32> {
+        self.try_borrow_mut()
+    }
+
+    fn try_borrow(&self) -> Result<Ref<AccountInfoMut>, u32> {
+        self.m.try_borrow().map_err(|_| std::u32::MAX)
+    }
+
+    fn try_borrow_mut(&self) -> Result<RefMut<'a, AccountInfoMut>, u32> {
+        self.m.try_borrow_mut().map_err(|_| std::u32::MAX)
+    }
+
     pub fn new(
         key: &'a Pubkey,
         is_signer: bool,
@@ -57,57 +86,56 @@ impl<'a> AccountInfo<'a> {
         Self {
             key,
             is_signer,
-            lamports,
-            data,
+            m: Rc::new(RefCell::new(AccountInfoMut { lamports, data })),
             owner,
         }
     }
 
     pub fn deserialize_data<T: serde::de::DeserializeOwned>(&self) -> Result<T, bincode::Error> {
-        bincode::deserialize(&self.data)
+        bincode::deserialize(&self.m.borrow().data)
     }
 
     pub fn serialize_data<T: serde::Serialize>(&mut self, state: &T) -> Result<(), bincode::Error> {
-        if bincode::serialized_size(state)? > self.data.len() as u64 {
+        if bincode::serialized_size(state)? > self.m.borrow().data.len() as u64 {
             return Err(Box::new(bincode::ErrorKind::SizeLimit));
         }
-        bincode::serialize_into(&mut self.data[..], state)
+        bincode::serialize_into(&mut self.m.borrow_mut().data[..], state)
     }
 }
 
 impl<'a> From<(&'a Pubkey, &'a mut Account)> for AccountInfo<'a> {
     fn from((key, account): (&'a Pubkey, &'a mut Account)) -> Self {
-        Self {
+        Self::new(
             key,
-            is_signer: false,
-            lamports: &mut account.lamports,
-            data: &mut account.data,
-            owner: &account.owner,
-        }
+            false,
+            &mut account.lamports,
+            &mut account.data,
+            &account.owner,
+        )
     }
 }
 
 impl<'a> From<(&'a Pubkey, bool, &'a mut Account)> for AccountInfo<'a> {
     fn from((key, is_signer, account): (&'a Pubkey, bool, &'a mut Account)) -> Self {
-        Self {
+        Self::new(
             key,
             is_signer,
-            lamports: &mut account.lamports,
-            data: &mut account.data,
-            owner: &account.owner,
-        }
+            &mut account.lamports,
+            &mut account.data,
+            &account.owner,
+        )
     }
 }
 
 impl<'a> From<&'a mut (Pubkey, Account)> for AccountInfo<'a> {
     fn from((key, account): &'a mut (Pubkey, Account)) -> Self {
-        Self {
+        Self::new(
             key,
-            is_signer: false,
-            lamports: &mut account.lamports,
-            data: &mut account.data,
-            owner: &account.owner,
-        }
+            false,
+            &mut account.lamports,
+            &mut account.data,
+            &account.owner,
+        )
     }
 }
 
@@ -120,12 +148,14 @@ pub fn create_is_signer_account_infos<'a>(
 ) -> Vec<AccountInfo<'a>> {
     accounts
         .iter_mut()
-        .map(|(key, is_signer, account)| AccountInfo {
-            key,
-            is_signer: *is_signer,
-            lamports: &mut account.lamports,
-            data: &mut account.data,
-            owner: &account.owner,
+        .map(|(key, is_signer, account)| {
+            AccountInfo::new(
+                key,
+                *is_signer,
+                &mut account.lamports,
+                &mut account.data,
+                &account.owner,
+            )
         })
         .collect()
 }

sdk/src/entrypoint.rs

@@ -4,10 +4,15 @@
 
 extern crate alloc;
 
-use crate::{account_info::AccountInfo, pubkey::Pubkey};
+use crate::{
+    account_info::{AccountInfo, AccountInfoMut},
+    pubkey::Pubkey,
+};
 use alloc::vec::Vec;
 use core::mem::size_of;
 use core::slice::{from_raw_parts, from_raw_parts_mut};
+use std::cell::RefCell;
+use std::rc::Rc;
 
 /// User implemented program entrypoint
 ///
@@ -15,7 +20,7 @@ use core::slice::{from_raw_parts, from_raw_parts_mut};
 /// accounts: Accounts passed as part of the instruction
 /// data: Instruction data
 pub type ProcessInstruction =
-    fn(program_id: &Pubkey, accounts: &mut [AccountInfo], data: &[u8]) -> bool;
+    fn(program_id: &Pubkey, accounts: &mut [AccountInfo], data: &[u8]) -> u32;
 
 /// Programs indicate success with a return value of 0
 pub const SUCCESS: u32 = 0;
@@ -57,37 +62,45 @@ pub unsafe fn deserialize<'a>(input: *mut u8) -> (&'a Pubkey, Vec<AccountInfo<'a
 
     let mut accounts = Vec::with_capacity(num_accounts);
     for _ in 0..num_accounts {
-        let is_signer = {
+        let dup_info = *(input.add(offset) as *const u8) as usize;
+        offset += size_of::<u8>();
+        if dup_info == 0 {
+            let is_signer = {
+                #[allow(clippy::cast_ptr_alignment)]
+                let is_signer_val = *(input.add(offset) as *const u64);
+                (is_signer_val != 0)
+            };
+            offset += size_of::<u64>();
+
+            let key: &Pubkey = &*(input.add(offset) as *const Pubkey);
+            offset += size_of::<Pubkey>();
+
             #[allow(clippy::cast_ptr_alignment)]
-            let is_signer_val = *(input.add(offset) as *const u64);
-            (is_signer_val != 0)
-        };
-        offset += size_of::<u64>();
+            let lamports = &mut *(input.add(offset) as *mut u64);
+            offset += size_of::<u64>();
 
-        let key: &Pubkey = &*(input.add(offset) as *const Pubkey);
-        offset += size_of::<Pubkey>();
+            #[allow(clippy::cast_ptr_alignment)]
+            let data_length = *(input.add(offset) as *const u64) as usize;
+            offset += size_of::<u64>();
 
-        #[allow(clippy::cast_ptr_alignment)]
-        let lamports = &mut *(input.add(offset) as *mut u64);
-        offset += size_of::<u64>();
+            let data = { from_raw_parts_mut(input.add(offset), data_length) };
+            offset += data_length;
 
-        #[allow(clippy::cast_ptr_alignment)]
-        let data_length = *(input.add(offset) as *const u64) as usize;
-        offset += size_of::<u64>();
+            let owner: &Pubkey = &*(input.add(offset) as *const Pubkey);
+            offset += size_of::<Pubkey>();
 
-        let data = { from_raw_parts_mut(input.add(offset), data_length) };
-        offset += data_length;
+            let m = Rc::new(RefCell::new(AccountInfoMut { lamports, data }));
 
-        let owner: &Pubkey = &*(input.add(offset) as *const Pubkey);
-        offset += size_of::<Pubkey>();
-
-        accounts.push(AccountInfo {
-            key,
-            is_signer,
-            lamports,
-            data,
-            owner,
-        });
+            accounts.push(AccountInfo {
+                key,
+                is_signer,
+                m,
+                owner,
+            });
+        } else {
+            // Duplicate account, clone the original
+            accounts.push(accounts[dup_info].clone());
+        }
     }
 
     // Instruction data

sdk/src/lib.rs

@@ -2,7 +2,6 @@
 extern crate self as solana_sdk;
 
 pub mod account;
-pub mod account_info;
 pub mod account_utils;
 pub mod bpf_loader;
 pub mod clock;
@@ -56,6 +55,7 @@ pub mod timing;
 pub use solana_sdk_macro::declare_id;
 
 // On-chain program specific modules
+pub mod account_info;
 pub mod entrypoint;
 pub mod log;
 

sdk/src/log.rs

@@ -89,9 +89,9 @@ pub fn sol_log_params(accounts: &[AccountInfo], data: &[u8]) {
         sol_log("- Key");
         account.key.log();
         sol_log("- Lamports");
-        sol_log_64(0, 0, 0, 0, *account.lamports);
+        sol_log_64(0, 0, 0, 0, *account.m.borrow().lamports);
         sol_log("- Account data length");
-        sol_log_64(0, 0, 0, 0, account.data.len() as u64);
+        sol_log_64(0, 0, 0, 0, account.m.borrow().data.len() as u64);
         sol_log("- Owner");
         account.owner.log();
     }

sdk/src/sysvar/mod.rs

@@ -71,10 +71,10 @@ pub trait Sysvar:
         bincode::serialize_into(&mut account.data[..], self).ok()
     }
     fn from_account_info(account_info: &AccountInfo) -> Option<Self> {
-        bincode::deserialize(&account_info.data).ok()
+        bincode::deserialize(&account_info.m.borrow().data).ok()
     }
     fn to_account_info(&self, account_info: &mut AccountInfo) -> Option<()> {
-        bincode::serialize_into(&mut account_info.data[..], self).ok()
+        bincode::serialize_into(&mut account_info.m.borrow_mut().data[..], self).ok()
     }
     fn from_keyed_account(keyed_account: &KeyedAccount) -> Result<Self, InstructionError> {
         if !Self::check_id(keyed_account.unsigned_key()) {