spec for write protection error (#365)

* hackmd for write protection error * fix typo ready --> read * Update specs/error_state/error_write_protection.md Co-authored-by: adria0.eth <[email protected]> --------- Co-authored-by: adria0.eth <[email protected]>
privacy-scaling-explorations · May 12, 2023 · 29f1c2d · 29f1c2d
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+# ErrorWriteProtection state
+
+## Procedure
+there are some op codes which modify state. there are `[SSTORE, CREATE, CREATE2, 
+CALL, SELFDESTRUCT, LOG0, LOG1, LOG2, LOG3, LOG4]`
+when execution call context is read only (static call), these op codes running will encounter
+write protection error. See [EIP-214](https://eips.ethereum.org/EIPS/eip-214)
+### EVM behavior
+in above op codes which modify state, `CALL` is somewhat special. for non call op codes(SSTORE, CREATE, etc)
+first check if running in read only call context, if yes, throw write protection error.
+for `CALL` op code, it will also check `value` is not zero. only both non zero value & read only call context, then
+throw write protection error.
+
+### Constraints
+1. constrain this error happens in one of op codes `[SSTORE, CREATE, CREATE2, 
+CALL, SELFDESTRUCT, LOG0, LOG1, LOG2, LOG3, LOG4]`
+2. current call context must be readonly & internal call(since requires at least one `staticcall` earlier).
+3. for `CALL` op code, do stack read & check `value` is not zero.
+4. common error steps constraints:
+  - current call must be failed.
+  - rw_counter_end_of_reversion constraint
+  - it restores caller's context by reading to `rw_table`, then does step state transition to it.
+
+## Code
+    TODO: after circuit merge!