- `GET_STATE_ROOT` and `SET_STATE_ROOT` deal with the root of the state trie, and will be called from storage routines. Similarly `GET_RECEIPT_ROOT` and `SET_RECEIPT_ROOT` deal with the root of the receipt trie.
- `PANIC` enables an unsatisfiable constraint, so no proof can be generated.
- `GET_CONTEXT` and `SET_CONTEXT`, used when calling and returning
- `CONSUME_GAS` charges the sender gas; useful for cases where gas calculations are nontrivial and best implemented in assembly.
- `EXIT_KERNEL` simply clears the CPU flag indicating that we're in kernel mode; it would be used just before a jump to return to the (userspace) caller.
- `MLOAD_GENERAL` and `MSTORE_GENERAL` are for reading and writing memory, but they're not limited to the main memory segment of the current context; they can access any context and any segment. I added a couple macros to show how the they would typically be used.
There may be more later, but these are the ones I think we need for now. I tried to fill in smaller invalid sections of the decoder's tree, as Jacqui suggested, while keeping related opcodes together. We can fine tune it when the opcode list is more stable.
These are all intended to be priviledged, i.e. they will be treated as invalid if used from userspace, for compatibility as well as (in some cases) security reasons.
The kernel is hashed using a Keccak based sponge for now. We could switch to Poseidon later if our kernel grows too large.
Note that we use simple zero-padding (pad0*) instead of the standard pad10* rule. It's simpler, and we don't care that the prover can add extra 0s at the end of the code. The program counter can never reach those bytes, and even if it could, they'd be 0 anyway given the EVM's zero-initialization rule.
In one CPU row, we can do a whole Keccak hash (via the CTL), absorbing 136 bytes. But we can't actually bootstrap that many bytes of kernel code in one row, because we're also limited by memory bandwidth. Currently we can write 4 bytes of the kernel to memory in one row.
So we treat the `keccak_input_limbs` columns as a buffer. We gradually fill up this buffer, 4 bytes (one `u32` word) at a time. Every `136 / 4 = 34` rows, the buffer will be full, so at that point we activate the Keccak CTL to absorb the buffer.
* Memory naming tweaks
- Define the channel count and value limbs in a single place, so they're easy to adjust.
- Standardize on "channels" which I think is more explicit, since e.g. `num_mem_ops` used to mean either the channel count or total operation count in a trace.
* feedback
* tweaks
* fmt
* Parse and assemble kernel functions
Written in "EVM++" assembly. Later on we will add some priviledged opcodes (in unused opcode ordinals), making it an extension of EVM bytecode.
I don't think there's much of a standard for EVM assembly, but I loosely based the syntax on this [proposal](https://gist.github.com/axic/17ddbbce4738ccf4040d30cbb5de484e).
* PR feedback
* tweaks for consistency
* terminology tweaks
* Update evm/src/cpu/kernel/opcodes.rs
Co-authored-by: Jacqueline Nabaglo <jakub@mirprotocol.org>
* Update evm/src/cpu/kernel/opcodes.rs
Co-authored-by: Jacqueline Nabaglo <jakub@mirprotocol.org>
* Update evm/src/cpu/kernel/opcodes.rs
Co-authored-by: Jacqueline Nabaglo <jakub@mirprotocol.org>
Co-authored-by: Jacqueline Nabaglo <jakub@mirprotocol.org>
