Selfdestruct gas and set (#947)

* Add new segment and global metadata

* Insert into self-destruct set

* Implement sys_selfdestruct

* PR feedback

* Fix stack underflow

* Forgot that NOT 1 ≠ 0. Added %not_bit macro for that.

evm/src/cpu/kernel/aggregator.rs

@@ -37,6 +37,7 @@ pub(crate) fn combined_kernel() -> Kernel {
         include_str!("asm/core/transfer.asm"),
         include_str!("asm/core/util.asm"),
         include_str!("asm/core/access_lists.asm"),
+        include_str!("asm/core/selfdestruct_set.asm"),
         include_str!("asm/curve/bls381/util.asm"),
         include_str!("asm/curve/bn254/curve_arithmetic/constants.asm"),
         include_str!("asm/curve/bn254/curve_arithmetic/curve_add.asm"),

evm/src/cpu/kernel/asm/core/selfdestruct_set.asm

@@ -0,0 +1,43 @@
+/// Self-destruct set.
+/// Essentially the same code as in `access_lists.asm`, with the exception that the insert function doesn't return anything.
+/// TODO: Would it make sense to merge this with `access_lists.asm`?
+/// TODO: Look into using a more efficient data structure.
+
+%macro insert_selfdestruct_set
+    %stack (addr) -> (addr, %%after)
+    %jump(insert_selfdestruct_set)
+%%after:
+    // stack: (empty)
+%endmacro
+
+/// Inserts the address into the self-destruct set if it is not already present.
+global insert_selfdestruct_set:
+    // stack: addr, retdest
+    %mload_global_metadata(@GLOBAL_METADATA_SELFDESTRUCT_SET_LEN)
+    // stack: len, addr, retdest
+    PUSH 0
+insert_selfdestruct_set_loop:
+    %stack (i, len, addr, retdest) -> (i, len, i, len, addr, retdest)
+    EQ %jumpi(insert_address)
+    // stack: i, len, addr, retdest
+    DUP1 %mload_kernel(@SEGMENT_SELFDESTRUCT_SET)
+    // stack: loaded_addr, i, len, addr, retdest
+    DUP4
+    // stack: addr, loaded_addr, i, len, addr, retdest
+    EQ %jumpi(insert_address_found)
+    // stack: i, len, addr, retdest
+    %increment
+    %jump(insert_selfdestruct_set_loop)
+
+insert_address:
+    %stack (i, len, addr, retdest) -> (i, addr, len, retdest)
+    %mstore_kernel(@SEGMENT_SELFDESTRUCT_SET) // Store new address at the end of the array.
+    // stack: len, retdest
+    %increment
+    %mstore_global_metadata(@GLOBAL_METADATA_SELFDESTRUCT_SET_LEN) // Store new length.
+    JUMP
+
+insert_address_found:
+    // stack: i, len, addr, retdest
+    %pop3
+    JUMP

evm/src/cpu/kernel/asm/core/terminate.asm

@@ -22,17 +22,60 @@ global sys_return:
     %jump(terminate_common)
 
 global sys_selfdestruct:
-    // stack: kexit_info, address
+    // stack: kexit_info, recipient
     SWAP1 %u256_to_addr
-    DUP1 %insert_accessed_addresses_no_return // TODO: Use return value in gas calculation.
-    // stack: address, kexit_info
-    POP // TODO: Transfer balance to address.
+    %address DUP1 %balance
+
+    // Insert recipient into the accessed addresses list.
+    // stack: balance, address, recipient, kexit_info
+    DUP3 %insert_accessed_addresses
+
+    // Compute gas.
+    // stack: cold_access, balance, address, recipient, kexit_info
+    %mul_const(@GAS_COLDACCOUNTACCESS)
+    DUP2
+    // stack: balance, gas_coldaccess, balance, address, recipient, kexit_info
+    ISZERO %not_bit
+    // stack: balance!=0, gas_coldaccess, balance, address, recipient, kexit_info
+    DUP5 %is_dead MUL %mul_const(@GAS_NEWACCOUNT)
+    // stack: gas_newaccount, gas_coldaccess, balance, address, recipient, kexit_info
+    ADD %add_const(@GAS_SELFDESTRUCT)
+    %stack (gas, balance, address, recipient, kexit_info) -> (gas, kexit_info, balance, address, recipient)
+    %charge_gas
+    %stack (kexit_info, balance, address, recipient) -> (balance, address, recipient, kexit_info)
+
+    // Insert address into the selfdestruct set.
+    // stack: balance, address, recipient, kexit_info
+    DUP2 %insert_selfdestruct_set
+
+    // Set the balance of the address to 0.
+    // stack: balance, address, recipient, kexit_info
+    PUSH 0
+    // stack: 0, balance, address, recipient, kexit_info
+    DUP3 %mpt_read_state_trie
+    // stack: account_ptr, 0, balance, address, recipient, kexit_info
+    %add_const(1)
+    // stack: balance_ptr, 0, balance, address, recipient, kexit_info
+    %mstore_trie_data // TODO: This should be a copy-on-write operation.
+
+    // If the recipient is the same as the address, then we're done.
+    // Otherwise, send the balance to the recipient.
+    %stack (balance, address, recipient, kexit_info) -> (address, recipient, recipient, balance, kexit_info)
+    EQ %jumpi(sys_selfdestruct_same_addr)
+    // stack: recipient, balance, kexit_info
+    %add_eth
+
     // stack: kexit_info
-    // TODO: Add address to the access list.
-    %charge_gas_const(@GAS_SELFDESTRUCT)
     %leftover_gas
     // stack: leftover_gas
-    // TODO: Destroy account.
+    PUSH 1 // success
+    %jump(terminate_common)
+
+sys_selfdestruct_same_addr:
+    // stack: recipient, balance, kexit_info
+    %pop2
+    %leftover_gas
+    // stack: leftover_gas
     PUSH 1 // success
     %jump(terminate_common)
 

evm/src/cpu/kernel/asm/core/transfer.asm

@@ -81,9 +81,10 @@ global add_eth:
     // stack: retdest
     JUMP
 global add_eth_new_account:
-    // TODO: Skip creation if amount == 0?
     // stack: null_account_ptr, addr, amount, retdest
     POP
+    // stack: addr, amount, retdest
+    DUP2 ISZERO %jumpi(add_eth_new_account_zero)
     %get_trie_data_size // pointer to new account we're about to create
     // stack: new_account_ptr, addr, amount, retdest
     SWAP2
@@ -98,6 +99,10 @@ global add_eth_new_account:
     // stack: key, new_account_ptr, retdest
     %jump(mpt_insert_state_trie)
 
+add_eth_new_account_zero:
+    // stack: addr, amount, retdest
+    %pop2 JUMP
+
 // Convenience macro to call add_eth and return where we left off.
 %macro add_eth
     %stack (addr, amount) -> (addr, amount, %%after)

evm/src/cpu/kernel/asm/core/util.asm

@@ -30,3 +30,43 @@
     // If there is no "to" field, then this is a contract creation.
     // stack: to == 0
 %endmacro
+
+// Returns 1 if the account is non-existent, 0 otherwise.
+%macro is_non_existent
+    // stack: addr
+    %mpt_read_state_trie
+    ISZERO
+%endmacro
+
+// Returns 1 if the account is empty, 0 otherwise.
+%macro is_empty
+    // stack: addr
+    %mpt_read_state_trie
+    // stack: account_ptr
+    DUP1 ISZERO %jumpi(%%false)
+    // stack: account_ptr
+    DUP1 %mload_trie_data
+    // stack: nonce, account_ptr
+    ISZERO %not_bit %jumpi(%%false)
+    %increment DUP1 %mload_trie_data
+    // stack: balance, balance_ptr
+    ISZERO %not_bit %jumpi(%%false)
+    %add_const(2) %mload_trie_data
+    // stack: code_hash
+    PUSH @EMPTY_STRING_HASH
+    EQ
+    %jump(%%after)
+%%false:
+    // stack: account_ptr
+    POP
+    PUSH 0
+%%after:
+%endmacro
+
+// Returns 1 if the account is dead (i.e., empty or non-existent), 0 otherwise.
+%macro is_dead
+    // stack: addr
+    DUP1 %is_non_existent
+    SWAP1 %is_empty
+    ADD // OR
+%endmacro

evm/src/cpu/kernel/asm/util/basic_macros.asm

@@ -345,3 +345,11 @@
     // stack: x
     %mod_const(0x10000000000000000000000000000000000000000) // 2^160
 %endmacro
+
+%macro not_bit
+    // stack: b
+    PUSH 1
+    // stack: 1, b
+    SUB
+    // stack: 1 - b
+%endmacro

evm/src/cpu/kernel/constants/global_metadata.rs

@@ -49,10 +49,12 @@ pub(crate) enum GlobalMetadata {
     AccessedAddressesLen = 23,
     /// Length of the storage keys access list.
     AccessedStorageKeysLen = 24,
+    /// Length of the self-destruct set.
+    SelfDestructSetLen = 25,
 }
 
 impl GlobalMetadata {
-    pub(crate) const COUNT: usize = 24;
+    pub(crate) const COUNT: usize = 25;
 
     pub(crate) fn all() -> [Self; Self::COUNT] {
         [
@@ -80,6 +82,7 @@ impl GlobalMetadata {
             Self::RefundCounter,
             Self::AccessedAddressesLen,
             Self::AccessedStorageKeysLen,
+            Self::SelfDestructSetLen,
         ]
     }
 
@@ -110,6 +113,7 @@ impl GlobalMetadata {
             Self::RefundCounter => "GLOBAL_METADATA_REFUND_COUNTER",
             Self::AccessedAddressesLen => "GLOBAL_METADATA_ACCESSED_ADDRESSES_LEN",
             Self::AccessedStorageKeysLen => "GLOBAL_METADATA_ACCESSED_STORAGE_KEYS_LEN",
+            Self::SelfDestructSetLen => "GLOBAL_METADATA_SELFDESTRUCT_SET_LEN",
         }
     }
 }

evm/src/memory/segments.rs

@@ -48,10 +48,12 @@ pub enum Segment {
     AccessedAddresses = 23,
     /// List of storage keys that have been accessed in the current transaction.
     AccessedStorageKeys = 24,
+    /// List of addresses that have called SELFDESTRUCT in the current transaction.
+    SelfDestructSet = 25,
 }
 
 impl Segment {
-    pub(crate) const COUNT: usize = 25;
+    pub(crate) const COUNT: usize = 26;
 
     pub(crate) fn all() -> [Self; Self::COUNT] {
         [
@@ -80,6 +82,7 @@ impl Segment {
             Self::BnPairing,
             Self::AccessedAddresses,
             Self::AccessedStorageKeys,
+            Self::SelfDestructSet,
         ]
     }
 
@@ -111,6 +114,7 @@ impl Segment {
             Segment::BnPairing => "SEGMENT_KERNEL_BN_PAIRING",
             Segment::AccessedAddresses => "SEGMENT_ACCESSED_ADDRESSES",
             Segment::AccessedStorageKeys => "SEGMENT_ACCESSED_STORAGE_KEYS",
+            Segment::SelfDestructSet => "SEGMENT_SELFDESTRUCT_SET",
         }
     }
 
@@ -142,6 +146,7 @@ impl Segment {
             Segment::BnPairing => 256,
             Segment::AccessedAddresses => 256,
             Segment::AccessedStorageKeys => 256,
+            Segment::SelfDestructSet => 256,
         }
     }
 }