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MIT/Apache

7KB

PolkaVM

PolkaVM is a general purpose user-level RISC-V based virtual machine.

This project is still unfinished and is a very heavy work-in-progress! Do not use it in production!

See current benchmark results here.

Design goals

(Note: not all of these are currently true!)

  • Secure and sandboxed by default. The code running in the VM should run in a separate process, and should not be able to access the host system, even in the presence of an attacker with full remote code execution privileges inside of the VM.
  • Fast to execute. The runtime performance of the code running in the VM should be competitive with state-of-art WebAssembly VMs, at least within the same order of magnitude.
  • Fast to compile, with guaranteed single-pass O(n) compilation. Loading new code into the VM should be near instanteneous.
  • Low memory footprint. Each concurrent instance of the VM should have a baseline memory overhead of no more than 128KB.
  • Small binaries. Programs compiled for this VM should take up as little space as possible.
  • No wasted virtual address space. The VM should not preallocate gigabytes of virtual address space for sandboxing purposes.
  • Fully deterministic. Given the same inputs and the same code the execution should always return exactly the same output.
  • Support for high performance asynchronous gas metering. Gas metering should be cheap, deterministic, and reasonably accurate.
  • Simple. It should be possible for a single programmer to write an interpreter fully compatible with this VM in less than a week.
  • Versioned operational semantics. Any future changes to the semantics that are observable by a guest program will be versioned, and will be explicitly opt-in.
  • Standardized. There should be a spec fully describing the guest-observable operational semantics of this VM.
  • Cross-platform. On unsupported OSes and platforms the VM will run in an interpreted mode.
  • Minimum external dependencies. The VM should be mostly self-contained, fast to compile, and resistant to supply-chain attacks.
  • Built-in tooling for debugging and performance profiling.

Non-goals

  • System level emulation. This VM will never be able to run a normal operating system.
  • Full support for architectures other than amd64 (also known as x86_64) and aarch64 (also known as arm64). Anything else will run in an interpreted mode.
  • Full support for operating systems other than Linux, macOS and Windows. On any other OS the VM will run in an interpreted mode.
  • Floating point support, SIMD, and other more niche RISC-V extensions. These could be added as an opt-in feature in the future if necessary, but this is not currently planned.
  • Support for full 32-register RISC-V ISA. This VM currently only targets the RV32EM.

License

Licensed under either of

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Dependencies

~0.5–1MB
~23K SLoC