Deterministic java virtual machine
A method and system are provided to support a decentralized distributed ledger in which transactions are recorded by parties to the transactions without the use of a blockchain. A distributed ledger system provides a protocol framework that supports the development of protocol flows. A protocol flow is computer code that controls the performance of a transaction by the party or parties to the transaction. Protocol flows can be developed for different types of transactions. The distributed ledger system allows transactions to be proposed, accepted, and notarized by a notary and stored without the use of a blockchain ledger. The distributed ledger system can avoid the expense of the computational and storage resources needed to redundantly verify a transaction and store evidence on the many nodes of a blockchain distributed ledger.
1. A method for modifying target code so that execution of the target code by a virtual machine is deterministic, the method comprising:
accessing, by a computing node, the target code;
disabling catching of an exception by the target code;
relinking, by the computing node, references of the target code from standard functions of a standard runtime library to shadow functions of a shadow runtime library, the shadow functions being deterministic versions of the standard functions; and
directing, by the computing node, use of a hardware-independent floating-point operation.
2. The method of claim 1 wherein the target code is contract code of a distributed ledger system and the virtual machine is a Java virtual machine.
3. The method of claim 2 wherein the contract code is fully pure.
4. The method of claim 2 wherein the directing of use of the hardware-independent floating-point operation includes adding a flag to a method of the target code.
5. The method of claim 2 wherein the relinking of references includes adjusting references in a constant pool.
6. The method of claim 1 further comprising prohibiting the target code from having finalizers and prohibiting calls to a native interface of the virtual machine.
7. The method of claim 1 further comprising prohibiting callbacks by a garbage collector of the virtual machine.
8. The method of claim 1 further comprising modifying calls to a hash code function so that a thread local random number generator of a thread is reseeded before execution begins.
9. A computing system for modifying target code so that execution of the target code by a virtual machine is deterministic, the computing system comprising:
one or more computer-readable storage mediums for storing computer-executable instructions for controlling the one or more computing systems to:
disable catching of an exception by the target code;
relink references of the target code from standard functions of a standard runtime library to shadow functions of a shadow runtime library, the shadow functions being deterministic versions of the standard functions; and
direct use of a hardware-independent floating-point operation; and
one or more processors for executing the computer-executable instructions stored in the one or more computer-readable storage mediums.
10. The computing system of claim 9 wherein the target code is contract code of a distributed ledger system and the virtual machine is a Java virtual machine.
11. The computing system of claim 9 wherein the computer-executable instructions for controlling the one or more computing systems further prohibit the target code from having finalizers and prohibiting calls to a native interface of the virtual machine.
12. The computing system of claim 9 wherein the computer-executable instructions for controlling the one or more computing systems further prohibit callbacks by a garbage collector of the virtual machine.
13. The computing system of claim 9 wherein the computer-executable instructions for controlling the one or more computing systems further modify calls to a hash code function so that a thread local random number generator of a thread is reseeded before execution begins.