Fix access lists pointers check #217
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4l0n50
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Nashtare
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May 6, 2024
Co-authored-by: Robin Salen <30937548+Nashtare@users.noreply.github.com>
Nashtare
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May 20, 2024
* Fix access lists pointers * Update evm_arithmetization/src/cpu/kernel/asm/core/access_lists.asm Co-authored-by: Robin Salen <30937548+Nashtare@users.noreply.github.com> * Address reviews --------- Co-authored-by: Robin Salen <30937548+Nashtare@users.noreply.github.com>
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For inserting/deleting in the access lists, the prover guesses the predecessor pointer divided by the list node size so that
node_size*guessed_valalways point the beginning of a valid node. In order to do so, it checked thatnode_size * guessed_val - SEGMENT_SCALLING < UNSCALED_LIST_LEN. This is not correct because the guessed value is the scaled pointer divided bynode_size(prover_input.rs:348), so it shouldn't be unscaled. Additionally, the comparison was done against the address ofUNSCALED_LIST_LENistead of the actual value.On the other hand, I find clearer to check that
guessed_val < UNSCALED_LIST_LEN/node_sizebecause for somenode_sizeit's possible to havenode_size * guessed_val mod 2^256 != 0 mod node_size(even though this is not possible becausenode_size = 2, 4).I'm also fixing macro
assert_gt, which wasn't a problem because it was never used.