Zkevm allow jumpdest in push n (#1011)

* fix jumpn

* hack

* add docs

---------

Co-authored-by: Igor Mandrigin <[email protected]>

core/vm/common.go

@@ -67,6 +67,14 @@ func getData(data []byte, start uint64, size uint64) []byte {
 // getDataBig returns a slice from the data based on the start and size and pads
 // up to size with zero's. This function is overflow safe.
 func getDataBig(data []byte, start *uint256.Int, size uint64) []byte {
+	/*
+	* zkEVM hack: we need to limit the size of the memory to 1GB
+	* for witness generation purpose we execute opcodes even if they are out of gas.
+	* that could lead to a huge memory allocation (in the reported case 400GB)
+	 */
+	if size >= 1*1024*1024*1024 {
+		size = 1 * 1024 * 1024 * 1024
+	}
 	start64, overflow := start.Uint64WithOverflow()
 	if overflow {
 		start64 = ^uint64(0)

core/vm/contract.go

@@ -102,7 +102,10 @@ func (c *Contract) validJumpdest(dest *uint256.Int) (bool, bool) {
 	if c.skipAnalysis {
 		return true, false
 	}
-	return c.isCode(udest), true
+	/*
+	* zkEVM doesn't do dynamic jumpdest analysis. So PUSHN is not considered.
+	 */
+	return true, false
 }
 
 func isCodeFromAnalysis(analysis []uint64, udest uint64) bool {