cannon: Allow EOF pre-image reads

This patch fixes a discrepancy in the Go and Solidity FPVM implementations.
The set of states, wherein their pre-image offsets are at the pre-image
EOF, is considered valid. The transition for these states is a zero-byte
pre-image read.
This behavior is similar to the way Linux handles read(2) syscalls where
reading at an EOF stream yields zero bytes read.

PreimageOracle.sol is updated to accommodate this by allowing pre-image
parts to be loaded at the pre-image EOF.

cannon/mipsevm/open_mips_tests/test/oracle.asm

@@ -69,6 +69,10 @@ $readloop:
   addiu $t0, $t0, -1
   bnez $t0, $readloop
   nop
+# reading the pre-image stream at EOF should have no effect
+  li $a1, 0x31000008
+  li $v0, 4003
+  syscall
 
 # length at 0x31000000. We also check that the lower 32 bits are zero
   lui $s1, 0x3100

op-bindings/bindings/preimageoracle.go

@@ -31,7 +31,7 @@ var (
 // PreimageOracleMetaData contains all meta data concerning the PreimageOracle contract.
 var PreimageOracleMetaData = &bind.MetaData{
 	ABI: "[{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"partOffset\",\"type\":\"uint256\"},{\"internalType\":\"bytes32\",\"name\":\"key\",\"type\":\"bytes32\"},{\"internalType\":\"bytes32\",\"name\":\"part\",\"type\":\"bytes32\"},{\"internalType\":\"uint256\",\"name\":\"size\",\"type\":\"uint256\"}],\"name\":\"cheat\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"uint256\",\"name\":\"partOffset\",\"type\":\"uint256\"},{\"internalType\":\"bytes\",\"name\":\"preimage\",\"type\":\"bytes\"}],\"name\":\"loadKeccak256PreimagePart\",\"outputs\":[],\"stateMutability\":\"nonpayable\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"bytes32\",\"name\":\"\",\"type\":\"bytes32\"}],\"name\":\"preimageLengths\",\"outputs\":[{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"bytes32\",\"name\":\"\",\"type\":\"bytes32\"},{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"name\":\"preimagePartOk\",\"outputs\":[{\"internalType\":\"bool\",\"name\":\"\",\"type\":\"bool\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"bytes32\",\"name\":\"\",\"type\":\"bytes32\"},{\"internalType\":\"uint256\",\"name\":\"\",\"type\":\"uint256\"}],\"name\":\"preimageParts\",\"outputs\":[{\"internalType\":\"bytes32\",\"name\":\"\",\"type\":\"bytes32\"}],\"stateMutability\":\"view\",\"type\":\"function\"},{\"inputs\":[{\"internalType\":\"bytes32\",\"name\":\"key\",\"type\":\"bytes32\"},{\"internalType\":\"uint256\",\"name\":\"offset\",\"type\":\"uint256\"}],\"name\":\"readPreimage\",\"outputs\":[{\"internalType\":\"bytes32\",\"name\":\"dat\",\"type\":\"bytes32\"},{\"internalType\":\"uint256\",\"name\":\"datLen\",\"type\":\"uint256\"}],\"stateMutability\":\"view\",\"type\":\"function\"}]",
-	Bin: "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",
+	Bin: "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",
 }
 
 // PreimageOracleABI is the input ABI used to generate the binding from.

packages/contracts-bedrock/contracts/cannon/PreimageOracle.sol

@@ -46,8 +46,8 @@ contract PreimageOracle {
         assembly {
             // len(sig) + len(partOffset) + len(preimage offset) = 4 + 32 + 32 = 0x44
             size := calldataload(0x44)
-            // revert if part offset >= size+8 (i.e. parts must be within bounds)
-            if iszero(lt(partOffset, add(size, 8))) {
+            // revert if part offset > size+8 (i.e. parts must be within bounds)
+            if gt(partOffset, add(size, 8)) {
                 revert(0, 0)
             }
             // we leave solidity slots 0x40 and 0x60 untouched,