BEP-214: BASEFEE opcode

BEP214.md

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+# BEP-214: BASEFEE opcode
+
+
+
+## Summary
+Adds an opcode that gives the EVM access to the block's base fee. This BEP is dependent on BEP-213 (EIP-1559 with base fee of 0).
+
+## Abstract
+
+Add a `BASEFEE (0x48)` that returns the value of the base fee of the current block it is executing in.
+
+Status
+This BEP is a draft. The code for this BEP has already been merged from upstream go-ethereum codebase into BSC node codebase. The work entails enabling EIP-3198 for BSC network configurations and perform hard fork.
+
+## Rationale
+The intended use case would be for contracts to get the value of the base fee (introduced by EIP-1559 (BEP-213)).
+
+## Specification
+Add a `BASEFEE` opcode at `(0x48)`, with gas cost `G_base`.
+
+|  Op  	| Input 	| Output 	| Cost 	|
+|:----:	|:-----:	|:------:	|:----:	|
+| 0x48 	|   0   	|    1   	|   2  	|
+
+## Rationale
+
+### Gas cost
+The value of the base fee is needed to process transactions. That means it's value is already available before running the EVM code.
+The opcode does not add extra complexity and additional read/write operations, hence the choice of `G_base` gas cost.
+
+## Backwards Compatibility
+There are no known backward compatibility issues with this opcode.
+
+## Test Cases
+
+### Nominal case
+Assuming current block base fee is `7 wei`.
+This should push the value `7` (left padded byte32) to the stack.
+
+Bytecode: `0x4800` (`BASEFEE, STOP`)
+
+|  Pc   |      Op     | Cost |   Stack   |   RStack  |
+|-------|-------------|------|-----------|-----------|
+|    0  |    BASEFEE  |    2 |        [] |        [] |
+|    1  |    STOP     |    0 |       [7] |        [] |
+
+Output: 0x
+Consumed gas: `2`
+
+## Security Considerations
+The value of the base fee is not sensitive and is publicly accessible in the block header. There are no known security implications with this opcode.
+
+## Copyright
+The content is licensed under [CC0](https://creativecommons.org/publicdomain/zero/1.0/).