This is a follow-up to #29520, and a preparatory PR to a more thorough
change in the journalling system.
### API methods instead of `append` operations
This PR hides the journal-implementation details away, so that the
statedb invokes methods like `JournalCreate`, instead of explicitly
appending journal-events in a list. This means that it's up to the
journal whether to implement it as a sequence of events or
aggregate/merge events.
### Snapshot-management inside the journal
This PR also makes it so that management of valid snapshots is moved
inside the journal, exposed via the methods `Snapshot() int` and
`RevertToSnapshot(revid int, s *StateDB)`.
### SetCode
JournalSetCode journals the setting of code: it is implicit that the
previous values were "no code" and emptyCodeHash. Therefore, we can
simplify the setCode journal.
### Selfdestruct
The self-destruct journalling is a bit strange: we allow the
selfdestruct operation to be journalled several times. This makes it so
that we also are forced to store whether the account was already
destructed.
What we can do instead, is to only journal the first destruction, and
after that only journal balance-changes, but not journal the
selfdestruct itself.
This simplifies the journalling, so that internals about state
management does not leak into the journal-API.
### Preimages
Preimages were, for some reason, integrated into the journal management,
despite not being a consensus-critical data structure. This PR undoes
that.
---------
Co-authored-by: Gary Rong <garyrong0905@gmail.com>
Currently our state journal tracks each storage update to a contract, having the ability to revert those changes to the previously set value.
For the very first modification however, it behaves a bit wonky. Reverting the update doesn't actually remove the dirty-ness of the slot, rather leaves it as "change this slot to it's original value". This can cause issues down the line with for example write witnesses needing to gather an unneeded proof.
This PR modifies the storageChange journal entry to not only track the previous value of a slot, but also whether there was any previous value at all set in the current execution context. In essence, the PR changes the semantic of storageChange so it does not simply track storage changes, rather it tracks dirty storage changes, an important distinction for being able to cleanly revert the journal item.
This change makes use of uin256 to represent balance in state. It touches primarily upon statedb, stateobject and state processing, trying to avoid changes in transaction pools, core types, rpc and tracers.
This change makes the StateDB track the state key value diff of a block transition.
We already tracked current account and storage values for the purpose of updating
the state snapshot. With this PR, we now also track the original (pre-transition) values
of accounts and storage slots.
This changes the journal logic to mark the state object dirty immediately when it
is reset.
We're mostly adding this change to appease the fuzzer. Marking it dirty immediately
makes no difference in practice because accounts will always be modified by EVM
right after creation.
This changes moves the tracking of "deleted in this block" out from snap-only domain, so that it happens regardless of whether the execution is snapshot-backed or trie-backed.
In `touch` operation, only `touched` filed has been changed. Therefore
in the related undo function, only `touched` field should be reverted.
In addition, whether remove this obj from dirty map should depend on
prevDirty flag.
This commit replaces the deep-copy based state revert mechanism with a
linear complexity journal. This commit also hides several internal
StateDB methods to limit the number of ways in which calling code can
use the journal incorrectly.
As usual consultation and bug fixes to the initial implementation were
provided by @karalabe, @obscuren and @Arachnid. Thank you!
