SIMD-0490

TL;DR

This SIMD will upgrade the Core BPF Stake Program to v5.0.0.

Summary

This SIMD will upgrade the Core BPF Stake Program to v5.0.0.

Motivation

The BPF Stake Program is under active development and requires feature-gated releases to upgrade to new versions. This proposal is not in and of itself a new feature. Aside from the general desire to improve and maintain the BPF Stake Program, this SIMD is necessary to activate the [Incremental Reduction of lamports_per_byte](https://github.com/solana-foundation/solana-improvement-documents/pull/437) feature gates.

Key Changes

• Raise minimum delegation from 1 lamport to 1 sol. This is a medium-firm
• Use the Rent sysvar in preference to Meta.rent_exempt_reserve. This is a
• Make all sysvar account inputs optional. The Stake Program will continue to
• Rewrite the implementation of Split to fix several longstanding bugs. Other

Impact

* Creating new stake accounts whose delegation is below 1 sol will no longer be possible. Dapps which create stake accounts must account for minimum delegation. Ultimately the Stake Program is the arbiter of correctness and will safely reject invalid state transitions. Merging stake accounts is always allowed, even if the merge destination does not rise above 1 sol. * `Meta.rent_exempt_reserve` is now deprecated and dapps should calculate rent- exemption via `Rent`. This is a consequence of rent reduction itself rather than this SIMD specifically. * Sysvars no longer need to be provided for Stake Program operations, reducing transaction size and allowing CPI callers to also no longer require these accounts in their own interfaces. Updated Stake Program instruction builders will be released after BPF Stake v5.0.0 is live on all networks. * The old version of `Split` treated initialized stakes and deactivated stakes differently due to a longstanding bug with the side-effect that deactivated stakes could sometimes not be `Split` from. This is now fixed and `Split` should always work under the rules of its operation. * When calling `Merge` on two activating stakes, only the source delegation and `rent_exempt_reserve` would be merged into the destination delegation. We now merge all lamports from the source account.

Backwards Compatibility

Minimum delegation will rise above 1 lamport. Tooling or onchain programs that assume `Rent.minimum_balance(200) + 1` is sufficient to create a stake account may break for very small balances. Splitting a stake account into itself is now an error. There is no valid usecase for such an act and as such we expect no breakage.

Security Considerations

BPF Stake v5.0.0 will undergo security audit before deployment is allowed.