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llvm-valida v0.5.0-alpha
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@morganthomas morganthomas released this 12 Nov 01:32
· 13 commits to main since this release
v0.5.0-alpha
f61a96b

System requirements

This toolchain supports x86-64 Linux based on glibc-2.9 or newer glibc. rustup is required. Arch Linux and Ubuntu 24.04 LTS are specifically supported, with other platforms possibly requiring some tinkering to make work.

Download

Download the toolchain

Installation

Run:

sudo ./install.sh

Usage instructions

Entering the Valida shell

Upon having installed the toolchain, the Valida shell should be on your PATH, and if you run which valida-shell, you should see:

$ which valida-shell
/usr/local/bin/valida-shell

If the result is something else, then either the installation did not complete successfully, or you had another valida-shell executable somewhere on your PATH.

If you run valida-shell, then you should see a shell prompt that reads valida> . You should then have on your PATH all of the executables from the Valida toolchain needed to follow the instructions below.

Compiling and running Rust programs

For examples of how to build a Rust program which compiles and runs on Valida, see lita-xyz/rust-examples on GitHub. You can use any of these examples as a starting point for developing your own programs using the Valida toolchain. Here are steps for doing so:

  1. Clone the project template:
$ git clone https://github.com/lita-xyz/fibonacci.git
  1. cd into the project template:
$ cd fibonacci
  1. Enter the Valida shell:
$ valida-shell
  1. Build the project:
valida> cargo +valida build
  1. Run the code (taking input from stdin):
valida> valida run --fast target/delendum-unknown-baremetal-gnu/debug/fibonacci log
  1. Prove the execution (taking input from stdin):
valida> valida prove target/delendum-unknown-baremetal-gnu/debug/fibonacci proof
  1. Verify the proof:
valida> valida verify target/delendum-unknown-baremetal-gnu/debug/fibonacci proof

Writing Rust programs to run on Valida

The Valida Rust compiler can currently compile in no_std mode, I.E. it cannot yet provide access to the std library, but can compile Rust programs which only use functionality contained within core, and which are annotated as #![no_std].

We do not (yet) support a main function signature that takes any arguments, so it's not possible to follow the normal method of specifying a main function in a #![no_std] program. The following is a demonstration of a simple program that shows how the main function must be declared instead:

#![no_main]

valida_rs::entrypoint!main(main);

#[no_mangle]
fn main() {
   ...
}

For a starting point to build a project using the Rust Valida toolchain, please take a look at
the template project. You can clone this repo and use
it as a starting point for your project.

The template project depends on the valida-rs crate. This contains a macro for generating an entry point, and some custom versions of standard library functions.

For projects with dependencies on io or rand, make sure your main and Cargo.toml include the code in this template. Also, make sure you have the same .cargo/config.toml in your project. If you want to build the project not targeting Valida, remove the [build] section in .cargo/config.toml and cargo will build the project targeting the host machine, unless otherwise specified.

We edited some functions to make them compatible with the Valida VM. When using these, the default Rust functions won't work. We call the Valida version with the entrypoint:: prefix.

  • io: Valida only supports standard io to the extent of stdin and stdout. To use println in Valida, one needs to call entrypoint::io::println as in my-project. A better io library will be added later.
  • rand: to ensure the VM can prove the calculation of a given random number, we use our own function to generate a random byte with a specific seed.

These implementations are in valida-rs/src/io.rs and valida-rs/src/rand.rs.

Compiling and running C programs

To enter the Valida shell, run:

valida-shell

See the lita-xyz/valida-c-examples repo on Github for some examples of C programs which can be compiled and run on Valida. Here is an example C program from this repo, called cat.c:

const unsigned EOF = 0xFFFFFFFF;

int main() {
    unsigned c = 0;
    while (1) {
        c = __builtin_delendum_read_advice();
        if (c == EOF) {
            break;
        } else {
            __builtin_delendum_write(c);
        }
    }
}

To compile, for example, the cat.c example, from within the Valida shell:

clang -target delendum ./cat.c -o cat
valida run cat log

Once running, the cat example will wait for input. After you are done providing input, press ctrl+D. The program should echo back what you wrote, writing its output to log.

Compiling and running the other examples follows the same procedure, substituting $NAME for the name of the example:

clang -target delendum ./examples/${NAME}.c -o ${NAME}
valida run ${NAME} log

Some other examples that are provided in the valida-c-examples repo:

  • reverse.c will output its reversed input.
  • checksum.c will output a checksum, i.e., a sum of the characters, of its input.
  • merkle-path.c will verify an opening proof for a SHA256 binary Merkle tree
    • For an example proof you can use as input, see examples/example-merkle-proof
  • sha256.c will output a SHA-256 hash of the first 256 bytes of its input.
  • sha256_32byte_in.c will output the SHA-256 hash of a constant array of 32 bytes. This is used as a benchmark.

Reporting issues

If you have any issues to report, please report them at the llvm-valida-releases issue tracker. Please include the following elements in your bug report: what release version you encountered the bug on, steps to reproduce, expected behavior, and actual behavior.

Known issues

  • The prover is unsound, which means that verifying a proof does not provide completely convincing evidence that the statement being proven is true. This will be resolved once some missing constraints are added.
  • Code which assumes that memory is initialized to zero might not work properly. This includes realloc in the C standard library. This will be resolved by updating the VM to treat uninitialized memory as having a value of zero.
  • The compiler might emit incorrect code for some 64-bit arithmetic operations. This will be resolved by adding appropriate tests and fixing any issues that come up.

Changelog

v0.5.0-alpha

Valida zk-VM

  • Resolves all known issues with prover completeness
    • Executions that are shorter than the segment size can be proven.
    • Proofs of execution can be verified.
  • Adds or fixes STARK constraints for MULHS, bit shifts, and single-byte memory operations
  • Enables proving subtractions with borrowing
  • Fixes a bug in the execution engine which incorrectly resulted in non-termination for programs using division opcodes

Compiler toolchain

  • Improvements to valida-rs Rust support crate
    • Additional I/O functions: read, write, and read_and_deserialize
    • Use little endian for serialization / deserialization
  • Passes an expanded Rust test suite

v0.4.0-alpha

Valida zk-VM

  • Passes an expanded test suite
  • Makes valida run much faster, and enables arbitrary length executions in valida run
  • Adds a mostly-complete memory argument
  • Checks consistency of fetched instructions with program ROM
  • Change order of reads during STORE instruction to match STARK constraints
  • Improved ELF executable file loader
  • The verifier no longer attempts to re-execute the program
  • Uses little endian consistently
  • Fixes STARK constraints for many ALU instructions
  • Supports the ability for the program to be included in the instance data or not
  • Adds missing STARK constraints for the program counter
  • Adds a separate preprocessing stage and the ability to read setup data from a file
  • Execution engine supports reading memory which has not been previously written, which results in zero
  • Exposes initial register values as instance data

Compiler toolchain

  • Passes an expanded test suite
  • Supports building Rust projects via cargo build
  • Supports dynamic memory management in C: malloc, free, calloc, realloc, aligned_alloc
  • Enables use of -O3
  • Supports variadic arguments
  • Uses stack allocation to lower constant pool nodes
  • Fixed bugs in the disassembler
  • Corrected calling convention when returning 64-bit integers
  • Fixes to 64-bit arithmetic
  • Enables DAGCombiner
  • Fixed truncload / extstore handling when addr is FPMemOpnd
  • Strips atomics and thread local storage attributes
  • Enables operand folder for some opcodes
  • Fixes by value argument passing in calling convention
  • Emits IMM32 instructions to represent immediate operands outside the field size
  • Improves linker script

v0.3.0-alpha

Valida

  • Completed the output chip, resulting in more executions being provable
  • Added support for public / instance data in the prover and verifier
  • Completed the 8-bit range check chip and used it in some relevant places
  • Added a general-purpose lookup argument, which is used in the range check chip
  • Fixed loading of .bss sections in ELF executable files
  • Pre-compute the preprocessed traces, instead of computing them each time the prover or verifier runs

LLVM-Valida

  • Added partial Rust support, including:
  • Added partial LLVM libc support, including:
    • A subset of libc header files, bundled with the release and customized for the LLVM Valida compiler backend
    • A linkable object code library (libc.a) compiled to run on Valida
    • An example program using isalpha
  • Bugfixes in the code generation backend, including:
    • Removed a pattern that prevented insertion of loadfp
    • Refined type legalization
    • Disabled tail call optimization
    • Fixed endianness related issues
    • Disabled branch analysis
    • Fixed FP alignment
    • Disabled generating jump tables
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