mirror of https://github.com/status-im/EIPs.git
122 lines
4.2 KiB
Markdown
122 lines
4.2 KiB
Markdown
---
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eip: 1985
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title: Sane limits for certain EVM parameters
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author: Alex Beregszaszi (@axic), Paweł Bylica (@chfast)
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discussions-to: https://ethereum-magicians.org/t/eip-1985-sane-limits-for-certain-evm-parameters/3224
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status: Draft
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type: Standards Track
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category: Core
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created: 2018-08-01
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---
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## Abstract
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Introduce an explicit value range for certain EVM parameters
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(such as gas limit, block number, block timestamp, size field when returning/copying data within EVM).
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Some of these already have an implicit value range due to various (practical) reasons.
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## Motivation
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Having such an explicit value range can help in creating compatible client implementations,
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in certain cases it can also offer minor speed improvements,
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and can reduce the effort needed to create consensus critical test cases
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by eliminating unrealistic edge cases.
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## Specification
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If `block.number >= {FORK_BLOCK}`, the following value ranges are introduced.
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They restrict the results (i.e. values pushed to the stack) of the opcodes listed below.
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1. *gas*, *gas limit*, *block gas limit*
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is a range between `0` and `9223372036854775807` (`2**63 - 1`).
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It affects following the opcodes:
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- `GASLIMIT` (`0x45`),
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- `GAS` (`0x5a`).
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2. *block number*, *timestamp*
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is a range between `0` and `9223372036854775807` (`2**63 - 1`).
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It affects the following opcodes:
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- `TIMESTAMP` (`0x42`),
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- `NUMBER` (`0x43`).
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3. *account address*
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is a range between `0` and `1461501637330902918203684832716283019655932542975` (`2**160 - 1`).
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It affects the following opcodes:
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- `ADDRESS` (`0x30`),
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- `ORIGIN` (`0x32`),
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- `CALLER` (`0x33`),
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- `COINBASE` (`0x41`),
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- `CREATE` (`0xf0`),
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- `CREATE2` (`0xf5`).
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4. *buffer size*
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is a range between `0` and `4294967295` (`2**32 - 1`).
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It affects the following opcodes:
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- `CALLDATASIZE` (`0x36`),
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- `CODESIZE` (`0x38`),
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- `EXTCODESIZE` (`0x3b`),
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- `RETURNDATASIZE` (`0x3d`),
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- `MSIZE` (`0x59`).
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## Rationale
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These limits have been:
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- proposed by [EVMC]
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- implemented partially by certain clients, such as [Aleth], [geth], [Parity] and [ethereumjs]
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- allowed by certain test cases in the [Ethereum testing suite]
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- and implicitly also allowed by certain assumptions, such as due to gas limits some of these values cannot grow past a certain limit
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Most of the limits proposed in this document have been previously explored and tested in [EVMC].
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Using the `2**63 - 1` constant to limit some of the ranges:
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- allows using signed 64-bit integer type to represent it,
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what helps programming languages not having unsigned types,
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- makes arithmetic simpler (e.g. checking out-of-gas conditions is simple as `gas_counter < 0`).
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### Timestamp
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The [Yellow Paper] defines the timestamp in block as "A scalar value equal to the reasonable output of Unix’s time() at this block’s inception".
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IEEE Std 1003.1-2001 (POSIX.1) leaves that definition implementation defined.
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### Addresses
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The size of addresses is specified in the [Yellow Paper] as 20 bytes.
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E.g. the `COINBASE` instruction is specified to return *H*<sub>c</sub> ∈ 𝔹<sub>20</sub> which has 20 bytes.
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### Comparing current implementations
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- Timestamp is implemented as a 64-bit value in [Aleth], [geth] and [Parity]
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- Block gas limit is implemented as a 64-bit in [Aleth] and [geth]
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## Backwards Compatibility
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All of these limits are already enforced mostly through the block gas limit. Since the out of range case results in a transaction failure, there should not be a change in behaviour.
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## Test Cases
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TBA
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## Implementation
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TBA
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## References
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[EIP-106](https://github.com/ethereum/EIPs/issues/106) proposed the block gas limit to be limited at `2**63 - 1`.
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## TODO
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1. Does the gas limit apply to the gas argument for call instructions?
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## Copyright
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Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).
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[EVMC]: https://github.com/ethereum/evmc
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[Aleth]: https://github.com/ethereum/aleth
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[geth]: https://github.com/ethereum/go-ethereum
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[Parity]: https://github.com/paritytech/parity-ethereum
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[ethereumjs]: https://github.com/ethereumjs
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[Ethereum testing suite]: https://github.com/ethereum/tests
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[Yellow Paper]: https://github.com/ethereum/yellowpaper
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