[isaacdoidge]

Summary

• cfg::BlockHashSource selects where Host::block_hash reads from. Database is the default and calls Database::block_hash, as upstream does. HistoryContract { floor } reads slot n % HISTORY_SERVE_WINDOW of the EIP-2935 history contract at HISTORY_STORAGE_ADDRESS. Cfg gains block_hash_source(), and CfgEnv gains the field plus set_block_hash_source / with_block_hash_source.
• With HistoryContract { floor }:
  • a non-zero slot is the hash;
  • a zero slot below floor returns zero, because no EVM block recorded that height;
  • a zero slot at or above floor is a height the contract should hold but does not, and is referred to Database::block_hash, whose result or error is the answer. A database error is stored as ContextError::Db and surfaces as EVMError::Database. The node's database serves no block hashes, so on SupraEVM this fails the block, as every database error does.
• JournalTr::storage_value_unwarmed returns a slot's present value without loading or warming the account or slot and without a journal entry. It reads the journal's state first, then treats an account created in the journal as having empty storage (as sload does), then falls back to the database. The journal is read first because the current block's history write stays in the journal until the block's state is finalized.
• The blockhash opcode, its 256-block range and its 20 gas are unchanged. The read does not warm the slot, so later accesses to the history contract are priced as before. This keeps Ethereum mainnet's BLOCKHASH cost rather than EIP-7709's (Draft) extra storage charge.

Motivation

smr-moonshot#4887: serve BLOCKHASH from the history ring that smr-moonshot#4885 writes before every block, so that the opcode no longer depends on the node's certified-block table and its pruning floor. The node selects HistoryContract with the height of the block that applied the EVM genesis as floor. The node-side change is smr-moonshot#5001, which pins this branch; its pin moves to the tag this PR is released in.

Notes for review

• JournalTr::storage_value_unwarmed is a required method. It is implemented for Journal and for the Backend in examples/cheatcode_inspector.
• history_storage.rs helpers are now pub(crate) so the new test module can reuse them.

Test plan

• cargo fmt --all --check
• RUSTFLAGS=-Dwarnings cargo clippy --workspace --all-targets --all-features
• cargo check --target riscv32imac-unknown-none-elf --no-default-features (and -p op-revm)
• cargo check --no-default-features -p revm --features=serde
• RUSTDOCFLAGS="--cfg docsrs -D warnings" cargo doc --workspace --all-features --no-deps --document-private-items
• cargo nextest run --workspace: all-features 569 passed; default features 567; --no-default-features 567
• cargo test --workspace --all-features --doc
• New ee-tests (history_block_hash):
  • a hash written by the System write earlier in the same journal is served while the database holds a different value for that slot;
  • a database-only hash is served;
  • after BLOCKHASH, the history contract's account and slot are still cold (the first get costs 4500 gas more than the second);
  • zero below the floor succeeds;
  • zero at or above the floor returns the database's hash, or EVMError::Database when the database's block_hash fails, including across the slot wrap;
  • the default source still calls Database::block_hash;
  • the current block, future blocks, distance 257 and block 0 do not reach the host.
• Journal unit tests for each case of storage_value_unwarmed.
• Mutation checks: a database-only read fails the same-journal test; reading with load_account + sload fails both not-warming checks.
• Not run locally: cargo hack --feature-powerset, zepter, the kzg-rs no_std entry, forge/genesis-bytecode jobs (no features or Solidity changed).

🤖 Generated with Claude Code

[aregng]

if requested_number < floor { can be done early to avoid journal read.

[isaacdoidge]

Closed unmerged. Entropy-Foundation/smr-moonshot#5001 serves BLOCKHASH from the EIP-2935 history contract through the existing Database::block_hash hook in smr-moonshot's EvmDB, so no revm change is needed.