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Update EIP-2935: bring up to date with sys contract impl #9144

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996724c
2935: bring up to date with sys contract impl
lightclient Dec 16, 2024
06493d5
2935: add rationale about ring buffer size
lightclient Dec 16, 2024
7180020
2935: correctly explain rationale for ring buffer size
lightclient Dec 16, 2024
d2e850e
Update EIPS/eip-2935.md
g11tech Jan 9, 2025
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Update EIPS/eip-2935.md
g11tech Jan 9, 2025
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93 changes: 34 additions & 59 deletions EIPS/eip-2935.md
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Original file line number Original file line Diff line number Diff line change
Expand Up @@ -26,10 +26,10 @@ A side benefit of this approach could be that it allows building/validating proo


| Parameter | Value | | Parameter | Value |
| - | - | | - | - |
| `BLOCKHASH_SERVE_WINDOW` | `256` | | `BLOCKHASH_SERVE_WINDOW` | `256` |
| `HISTORY_SERVE_WINDOW` | `8192` | | `HISTORY_SERVE_WINDOW` | `8191` |
| `SYSTEM_ADDRESS` | `0xfffffffffffffffffffffffffffffffffffffffe` | | `SYSTEM_ADDRESS` | `0xfffffffffffffffffffffffffffffffffffffffe` |
| `HISTORY_STORAGE_ADDRESS` | `0x0aae40965e6800cd9b1f4b05ff21581047e3f91e`| | `HISTORY_STORAGE_ADDRESS` | `0x0F792be4B0c0cb4DAE440Ef133E90C0eCD48CCCC` |


This EIP specifies for storing last `HISTORY_SERVE_WINDOW` block hashes in a ring buffer storage of `HISTORY_SERVE_WINDOW` length. Note that `HISTORY_SERVE_WINDOW` > `BLOCKHASH_SERVE_WINDOW` (which remains unchanged). This EIP specifies for storing last `HISTORY_SERVE_WINDOW` block hashes in a ring buffer storage of `HISTORY_SERVE_WINDOW` length. Note that `HISTORY_SERVE_WINDOW` > `BLOCKHASH_SERVE_WINDOW` (which remains unchanged).


Expand Down Expand Up @@ -60,8 +60,8 @@ The history contract has two operations: `get` and `set`. The `set` operation is
It is used from the EVM for looking up block hashes. It is used from the EVM for looking up block hashes.


* Callers provide the block number they are querying in a big-endian encoding. * Callers provide the block number they are querying in a big-endian encoding.
* If calldata is bigger than 2^64-1, revert. * If calldata is not 32 bytes, revert.
* For any output outside the range of [block.number-`HISTORY_SERVE_WINDOW`, block.number-1] return 0. * For any request outside the range of [block.number-`HISTORY_SERVE_WINDOW`, block.number-1], revert.
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@g11tech g11tech Dec 17, 2024 •
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this is not the current BLOCKHASH (with window 256) behavior so we are actually diverging from the behavior ?

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@lightclient lightclient Jan 6, 2025

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mentioned this elsewhere, but I think this divergence is okay because i) it matches other system contracts and ii) it is pretty straightforward to create an adapter around this system contract to mimic the BLOCKHASH behavior when it is used to back the actual op.



#### `set` #### `set`


Expand All @@ -73,89 +73,58 @@ It is used from the EVM for looking up block hashes.
Exact evm assembly that can be used for the history contract: Exact evm assembly that can be used for the history contract:


``` ```
// if system call then jump to the set operation // https://github.com/lightclient/sys-asm/blob/f1c13e285b6aeef2b19793995e00861bf0f32c9a/src/execution_hash/main.eas
caller caller
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push20 0xfffffffffffffffffffffffffffffffffffffffe push20 0xfffffffffffffffffffffffffffffffffffffffe
eq eq
push1 0x57 push1 0x46
jumpi
push1 0x20
calldatasize
sub
push1 0x42
jumpi jumpi

// check if input > 8 byte value and revert if this isn't the case
// the check is performed by comparing the biggest 8 byte number with
// the call data, which is a right-padded 32 byte number.
push8 0xffffffffffffffff
push0 push0
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@gballet gballet Dec 30, 2024

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Suggested change
push0
// Check if input is requesting a block hash greater than current block number
// minus 1.
push0

calldataload calldataload
gt push1 0x01
push1 0x53
jumpi

// check if input > blocknumber-1 then return 0
push1 0x1
number number
sub sub
push0 dup2
calldataload
gt gt
push1 0x4b push1 0x42
jumpi jumpi

push2 0x1fff
// check if blocknumber > input + 8192 then return 0, no overflow expected for input of < max 8 byte value dup2
Comment on lines +96 to +97
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Suggested change
push2 0x1fff
dup2
// Check if the input is requesting a block hash before the earliest available
// hash currently. Since we've verified that input <= number - 1, we know
// there will be no overflow during the subtraction of number - input.
push2 0x1fff
dup2

push0
calldataload
push2 0x2000
add
number number
sub
gt gt
push1 0x4b push1 0x42
jumpi jumpi

// mod 8192 and sload
push2 0x1fff push2 0x1fff
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@gballet gballet Dec 30, 2024

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Suggested change
push2 0x1fff
// Load the hash.
push2 0x1fff

push0 swap1
calldataload mod
and
sload sload

// load into mem and return 32 bytes
push0
mstore
push1 0x20
push0
return

// 0x4b: return 0
jumpdest
push0
push0 push0
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@gballet gballet Dec 30, 2024

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Suggested change
push0
// Load into memory and return.
push0

mstore mstore
push1 0x20 push1 0x20
push0 push0
return return

// 0x53: revert
jumpdest jumpdest
push0 push0
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@gballet gballet Dec 30, 2024

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Suggested change
push0
// Reverts current execution with no return data.
push0

push0 push0
revert revert

// 0x57: set op - sstore the input to number-1 mod 8192
Comment on lines -141 to -142
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@gballet gballet Dec 17, 2024

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any reason for removing the comments ?

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@lightclient lightclient Jan 6, 2025

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I removed all these comments because the assembled code comes from the command:

disease --code 0x$(geas src/consolidations/main.eas) | sed -E '/^[[:space:]]*$/d; s/^[[:space:]]*[0-9a-fA-F]+:[[:space:]]+//; s/[[:space:]]*# selector\(.*\)$//'

all the code info is in the sysasm: https://github.com/lightclient/sys-asm/blob/main/src/execution_hash/main.eas

I'd probably hold off on code comments in the eip until this is going to last call.

jumpdest jumpdest
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@gballet gballet Dec 30, 2024

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Suggested change
jumpdest
// sstore block hash
jumpdest

push0 push0
calldataload calldataload
push2 0x1fff push2 0x1fff
push1 0x1 push1 0x01
number number
sub sub
and mod
sstore sstore

stop stop
``` ```


Corresponding bytecode:
`0x3373fffffffffffffffffffffffffffffffffffffffe1460575767ffffffffffffffff5f3511605357600143035f3511604b575f35612000014311604b57611fff5f3516545f5260205ff35b5f5f5260205ff35b5f5ffd5b5f35611fff60014303165500`

#### Deployment #### Deployment


A special synthetic address is generated by working backwards from the desired deployment transaction: A special synthetic address is generated by working backwards from the desired deployment transaction:
Expand All @@ -170,17 +139,17 @@ A special synthetic address is generated by working backwards from the desired d
"maxPriorityFeePerGas": null, "maxPriorityFeePerGas": null,
"maxFeePerGas": null, "maxFeePerGas": null,
"value": "0x0", "value": "0x0",
"input": "0x60648060095f395ff33373fffffffffffffffffffffffffffffffffffffffe1460575767ffffffffffffffff5f3511605357600143035f3511604b575f35612000014311604b57611fff5f3516545f5260205ff35b5f5f5260205ff35b5f5ffd5b5f35611fff60014303165500", "input": "0x60538060095f395ff33373fffffffffffffffffffffffffffffffffffffffe14604657602036036042575f35600143038111604257611fff81430311604257611fff9006545f5260205ff35b5f5ffd5b5f35611fff60014303065500",
"v": "0x1b", "v": "0x1b",
"r": "0x539", "r": "0x539",
"s": "0x1b9b6eb1f0", "s": "0xbaefe09f0109759",
"hash": "0x3c769a03d6e2212f1d26ab59ba797dce0900df29ffd23c1dd391fd6b217973ad", "hash": "0x8c7bd2d3713a0b2bb693463d2a78c4d612ac47dd38ecb74f8996a4b6fc96f03c"
} }
``` ```


Note, the input in the transaction has a simple constructor prefixing the desired runtime code. Note, the input in the transaction has a simple constructor prefixing the desired runtime code.


The sender of the transaction can be calculated as `0xe473f7e92ba2490e9fcbbe8bb9c3be3adbb74efc`. The address of the first contract deployed from the account is `rlp([sender, 0])` which equals `0x0aae40965e6800cd9b1f4b05ff21581047e3f91e`. This is how `HISTORY_STORAGE_ADDRESS` is determined. Although this style of contract creation is not tied to any specific initcode like create2 is, the synthetic address is cryptographically bound to the input data of the transaction (e.g. the initcode). The sender of the transaction can be calculated as `0xE9f0662359Bb2c8111840eFFD73B9AFA77CbDE10`. The address of the first contract deployed from the account is `rlp([sender, 0])` which equals `0x0F792be4B0c0cb4DAE440Ef133E90C0eCD48CCCC`. This is how `HISTORY_STORAGE_ADDRESS` is determined. Although this style of contract creation is not tied to any specific initcode like create2 is, the synthetic address is cryptographically bound to the input data of the transaction (e.g. the initcode).




Some activation scenarios: Some activation scenarios:
Expand Down Expand Up @@ -233,6 +202,12 @@ def process_block_hash_history(block: Block, state: State):


The first option is recommended until the Verkle fork, to stay consistent with [EIP-4788](./eip-4788.md) and to issues for misconfigured networks where this EIP is activated but history contract hasn't been deployed. The recommendation may be reconsidered at the Verkle fork if filtering the system contract code chunks is deemed too complex. The first option is recommended until the Verkle fork, to stay consistent with [EIP-4788](./eip-4788.md) and to issues for misconfigured networks where this EIP is activated but history contract hasn't been deployed. The recommendation may be reconsidered at the Verkle fork if filtering the system contract code chunks is deemed too complex.


### Size of ring buffers

The ring buffer data structure is sized to hold 8191 hashes. In other system contracts a prime ring buffer size is chosen in because using a prime as the modulus ensures that no value is overwritten until the entire ring buffer has been saturated and thereafter, each value will be updated once per iteration, regardless of if some slot are missing or the slot time changes. However, in this EIP the block number is the value in the modulo operation and it only ever increases by 1 each iteration. Which means we can be confident that the ring buffer will always remain saturated.
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For consistency with other system contracts, we have decided to retain the buffer size of 8191. Given the current mainnet values, 8191 roots provides about a day of coverage. This also gives users plenty of time to make a transaction with a verification against a specific hash and get the transaction included on-chain.
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## Backwards Compatibility ## Backwards Compatibility


This EIP introduces backwards incompatible changes to the block validation rule set. But neither of these changes break anything related to current user activity and experience. This EIP introduces backwards incompatible changes to the block validation rule set. But neither of these changes break anything related to current user activity and experience.
Expand Down