pico: Guest program compilation with stock rust compiler. (#118)

Co-authored-by: kevaundray <kevtheappdev@gmail.com>
Co-authored-by: Han <tinghan0110@gmail.com>

Cargo.lock

@@ -2337,8 +2337,10 @@ dependencies = [
 name = "ere-pico"
 version = "0.0.11"
 dependencies = [
+ "anyhow",
  "bincode",
  "build-utils",
+ "cargo_metadata 0.19.2",
  "pico-sdk",
  "pico-vm",
  "serde",

crates/ere-pico/Cargo.toml

@@ -6,7 +6,9 @@ rust-version.workspace = true
 license.workspace = true
 
 [dependencies]
+anyhow.workspace = true
 bincode.workspace = true
+cargo_metadata.workspace = true
 serde.workspace = true
 thiserror.workspace = true
 

crates/ere-pico/src/compile_stock_rust.rs

@@ -0,0 +1,111 @@
+use crate::error::PicoError;
+use cargo_metadata::MetadataCommand;
+use std::fs;
+use std::path::Path;
+use std::process::Command;
+
+static CARGO_ENCODED_RUSTFLAGS_SEPARATOR: &str = "\x1f";
+
+const TARGET_TRIPLE: &str = "riscv32ima-unknown-none-elf";
+// According to https://github.com/brevis-network/pico/blob/v1.1.7/sdk/cli/src/build/build.rs#L104
+const RUSTFLAGS: &[&str] = &[
+    // Replace atomic ops with nonatomic versions since the guest is single threaded.
+    "-C",
+    "passes=lower-atomic",
+    // Specify where to start loading the program in
+    // memory.  The clang linker understands the same
+    // command line arguments as the GNU linker does; see
+    // https://ftp.gnu.org/old-gnu/Manuals/ld-2.9.1/html_mono/ld.html#SEC3
+    // for details.
+    "-C",
+    "link-arg=-Ttext=0x00200800",
+    // Apparently not having an entry point is only a linker warning(!), so
+    // error out in this case.
+    "-C",
+    "link-arg=--fatal-warnings",
+    "-C",
+    "panic=abort",
+];
+const CARGO_ARGS: &[&str] = &[
+    "build",
+    "--target",
+    TARGET_TRIPLE,
+    "--release",
+    // For bare metal we have to build core and alloc
+    "-Zbuild-std=core,alloc",
+];
+
+pub fn compile_pico_program_stock_rust(
+    guest_directory: &Path,
+    toolchain: &String,
+) -> Result<Vec<u8>, PicoError> {
+    compile_program_stock_rust(guest_directory, toolchain)
+}
+
+fn compile_program_stock_rust(
+    guest_directory: &Path,
+    toolchain: &String,
+) -> Result<Vec<u8>, PicoError> {
+    let metadata = MetadataCommand::new().current_dir(guest_directory).exec()?;
+    let package = metadata
+        .root_package()
+        .ok_or_else(|| PicoError::MissingPackageName {
+            path: guest_directory.to_path_buf(),
+        })?;
+
+    let plus_toolchain = format!("+{}", toolchain);
+    let mut cargo_args = [plus_toolchain.as_str()].to_vec();
+    cargo_args.append(&mut CARGO_ARGS.to_vec());
+
+    let encoded_rust_flags = RUSTFLAGS.to_vec().join(CARGO_ENCODED_RUSTFLAGS_SEPARATOR);
+
+    let target_direcotry = guest_directory
+        .join("target")
+        .join(TARGET_TRIPLE)
+        .join("release");
+
+    // Remove target directory.
+    if target_direcotry.exists() {
+        fs::remove_dir_all(&target_direcotry).unwrap();
+    }
+
+    let result = Command::new("cargo")
+        .current_dir(guest_directory)
+        .env("CARGO_ENCODED_RUSTFLAGS", &encoded_rust_flags)
+        .args(cargo_args)
+        .stdout(std::process::Stdio::inherit())
+        .stderr(std::process::Stdio::inherit())
+        .status()
+        .map_err(|source| PicoError::BuildFailure {
+            source: source.into(),
+            crate_path: guest_directory.to_path_buf(),
+        });
+
+    if result.is_err() {
+        return Err(result.err().unwrap());
+    }
+
+    let elf_path = target_direcotry.join(&package.name);
+
+    fs::read(&elf_path).map_err(|e| PicoError::ReadFile {
+        path: elf_path,
+        source: e,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::compile_stock_rust::compile_pico_program_stock_rust;
+    use test_utils::host::testing_guest_directory;
+
+    #[test]
+    fn test_stock_compiler_impl() {
+        let guest_directory = testing_guest_directory("pico", "stock_nightly_no_std");
+        let result = compile_pico_program_stock_rust(&guest_directory, &"nightly".to_string());
+        assert!(result.is_ok(), "Pico guest program compilation failure.");
+        assert!(
+            !result.unwrap().is_empty(),
+            "ELF bytes should not be empty."
+        );
+    }
+}

crates/ere-pico/src/error.rs

@@ -33,4 +33,20 @@ pub enum PicoError {
         #[source]
         source: io::Error,
     },
+    #[error("Pico build failure for {crate_path} failed: {source}")]
+    BuildFailure {
+        #[source]
+        source: anyhow::Error,
+        crate_path: PathBuf,
+    },
+    #[error("Could not find `[package].name` in guest Cargo.toml at {path}")]
+    MissingPackageName { path: PathBuf },
+    #[error("Failed to read file at {path}: {source}")]
+    ReadFile {
+        path: PathBuf,
+        #[source]
+        source: std::io::Error,
+    },
+    #[error("`cargo metadata` failed: {0}")]
+    MetadataCommand(#[from] cargo_metadata::Error),
 }

crates/ere-pico/src/lib.rs

@@ -1,14 +1,17 @@
 #![cfg_attr(not(test), warn(unused_crate_dependencies))]
 
+use compile_stock_rust::compile_pico_program_stock_rust;
 use pico_sdk::client::DefaultProverClient;
 use pico_vm::{configs::stark_config::KoalaBearPoseidon2, emulator::stdin::EmulatorStdinBuilder};
 use serde::de::DeserializeOwned;
-use std::{io::Read, path::Path, process::Command, time::Instant};
+use std::{env, io::Read, path::Path, process::Command, time::Instant};
 use zkvm_interface::{
     Compiler, Input, InputItem, ProgramExecutionReport, ProgramProvingReport, Proof,
     ProverResourceType, PublicValues, zkVM, zkVMError,
 };
 
+mod compile_stock_rust;
+
 include!(concat!(env!("OUT_DIR"), "/name_and_sdk_version.rs"));
 mod error;
 use error::PicoError;
@@ -21,40 +24,51 @@ impl Compiler for PICO_TARGET {
 
     type Program = Vec<u8>;
 
-    fn compile(&self, guest_path: &Path) -> Result<Self::Program, Self::Error> {
-        // 1. Check guest path
-        if !guest_path.exists() {
-            return Err(PicoError::PathNotFound(guest_path.to_path_buf()));
+    fn compile(&self, guest_directory: &Path) -> Result<Self::Program, Self::Error> {
+        let toolchain = env::var("ERE_GUEST_TOOLCHAIN").unwrap_or_else(|_error| "pico".into());
+        match toolchain.as_str() {
+            "pico" => Ok(compile_pico_program(guest_directory)?),
+            _ => Ok(compile_pico_program_stock_rust(
+                guest_directory,
+                &toolchain,
+            )?),
         }
-
-        // 2. Run `cargo pico build`
-        let status = Command::new("cargo")
-            .current_dir(guest_path)
-            .env("RUST_LOG", "info")
-            .args(["pico", "build"])
-            .status()?; // From<io::Error> → Spawn
-
-        if !status.success() {
-            return Err(PicoError::CargoFailed { status });
-        }
-
-        // 3. Locate the ELF file
-        let elf_path = guest_path.join("elf/riscv32im-pico-zkvm-elf");
-
-        if !elf_path.exists() {
-            return Err(PicoError::ElfNotFound(elf_path));
-        }
-
-        // 4. Read the ELF file
-        let elf_bytes = std::fs::read(&elf_path).map_err(|e| PicoError::ReadElf {
-            path: elf_path,
-            source: e,
-        })?;
-
-        Ok(elf_bytes)
     }
 }
 
+fn compile_pico_program(guest_directory: &Path) -> Result<Vec<u8>, PicoError> {
+    // 1. Check guest path
+    if !guest_directory.exists() {
+        return Err(PicoError::PathNotFound(guest_directory.to_path_buf()));
+    }
+
+    // 2. Run `cargo pico build`
+    let status = Command::new("cargo")
+        .current_dir(guest_directory)
+        .env("RUST_LOG", "info")
+        .args(["pico", "build"])
+        .status()?; // From<io::Error> → Spawn
+
+    if !status.success() {
+        return Err(PicoError::CargoFailed { status });
+    }
+
+    // 3. Locate the ELF file
+    let elf_path = guest_directory.join("elf/riscv32im-pico-zkvm-elf");
+
+    if !elf_path.exists() {
+        return Err(PicoError::ElfNotFound(elf_path));
+    }
+
+    // 4. Read the ELF file
+    let elf_bytes = std::fs::read(&elf_path).map_err(|e| PicoError::ReadElf {
+        path: elf_path,
+        source: e,
+    })?;
+
+    Ok(elf_bytes)
+}
+
 pub struct ErePico {
     program: <PICO_TARGET as Compiler>::Program,
 }
@@ -193,6 +207,17 @@ mod tests {
         run_zkvm_execute(&zkvm, &io);
     }
 
+    #[test]
+    fn test_execute_nightly() {
+        let guest_directory = testing_guest_directory("pico", "stock_nightly_no_std");
+        let program =
+            compile_pico_program_stock_rust(&guest_directory, &"nightly".to_string()).unwrap();
+        let zkvm = ErePico::new(program, ProverResourceType::Cpu);
+
+        let result = zkvm.execute(&BasicProgramIo::empty());
+        assert!(result.is_ok(), "Pico execution failure");
+    }
+
     #[test]
     fn test_execute_invalid_inputs() {
         let program = basic_program();

docker/pico/Dockerfile

@@ -11,6 +11,9 @@ RUN chmod +x /tmp/install_pico_sdk.sh
 
 RUN rustup default nightly
 
+# Add `rust-src` component to enable std build for nightly rust.
+RUN rustup +nightly component add rust-src
+
 # Run the Pico SDK installation script.
 # This script installs the specific Rust toolchain (nightly-2025-08-04)
 # and installs pico-cli (as cargo-pico).

tests/pico/stock_nightly_no_std/Cargo.toml

@@ -0,0 +1,7 @@
+[package]
+name = "addition_no_std"
+edition = "2021"
+
+[dependencies]
+
+[workspace]

tests/pico/stock_nightly_no_std/src/main.rs

@@ -0,0 +1,26 @@
+#![no_std]
+#![no_main]
+extern crate alloc;
+
+use alloc::vec::Vec;
+use core::sync::atomic::Ordering;
+use core::sync::atomic::AtomicU16;
+
+mod pico_rt;
+
+fn main() {
+    let a: AtomicU16 = core::hint::black_box(AtomicU16::new(5));
+    let b: AtomicU16 = core::hint::black_box(AtomicU16::new(7));
+
+    if a.load(Ordering::SeqCst) + b.load(Ordering::SeqCst) != 12 {
+        panic!("Something went wrong!");
+    }
+
+    let mut v: Vec<AtomicU16> = Vec::new();
+    v.push(AtomicU16::new(5));
+    v.push(AtomicU16::new(7));
+
+    if v[0].load(Ordering::SeqCst) + v[1].load(Ordering::SeqCst) != 12 {
+        panic!("Something went wrong!");
+    }
+}

tests/pico/stock_nightly_no_std/src/pico_rt.rs

@@ -0,0 +1,136 @@
+use core::alloc::{GlobalAlloc, Layout};
+// Import user `main` function
+use crate::main;
+
+// 1. Init global pointer (GP). It's used to optimize jumps by linker. Linker can change jumping from PC(Program Counter) based to GP based.
+// 2. Init stack pointer to the value STACK_TOP. It's stored in sp register.
+// 3. Call __start function defined below.
+// `__global_pointer$` is set by the linker. Its value depends on linker optimization. https://www.programmersought.com/article/77722901592/
+core::arch::global_asm!(
+    r#"
+.section .text._start;
+.globl _start;
+_start:
+    .option push;
+    .option norelax;
+    la gp, __global_pointer$;
+    .option pop;
+    la sp, {0}
+    lw sp, 0(sp)
+    call __start;
+"#,
+    sym STACK_TOP
+);
+
+static STACK_TOP: u32 = 0x0020_0400;
+
+// 1. Call `main` user function
+// 2. Call system halt environment function. It's defined by sp1 vm.
+#[unsafe(no_mangle)]
+fn __start(_argc: isize, _argv: *const *const u8) -> isize {
+    main();
+
+    syscall_halt(0);
+    unreachable!()
+}
+
+/// Halts the program with the given exit code.
+/// According to https://github.com/brevis-network/pico/blob/v1.1.7/sdk/sdk/src/riscv_ecalls/halt.rs#L15
+/// TODO: Check what `coprocessor` feature does and integrate here.
+/// Contex https://github.com/brevis-network/pico/blob/v1.1.7/sdk/sdk/src/riscv_ecalls/halt.rs#L18
+#[allow(unused_variables)]
+pub extern "C" fn syscall_halt(exit_code: u8) -> ! {
+    unsafe {
+        core::arch::asm!(
+            "ecall",
+            in("t0") 0x00_00_00_00,
+            in("a0") exit_code
+        );
+        unreachable!()
+    }
+}
+
+// Implement panic handling by calling undefined instruction. To be fixed. We need to support `fence` to be able to use e.i. `portable_atomic` lib.
+#[panic_handler]
+fn panic_impl(_panic_info: &core::panic::PanicInfo) -> ! {
+    unsafe {  core::arch::asm!("fence", options(noreturn)) };
+}
+
+/// A simple heap allocator.
+///
+/// Allocates memory from left to right, without any deallocation.
+struct SimpleAlloc;
+
+unsafe impl GlobalAlloc for SimpleAlloc {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        unsafe {
+            sys_alloc_aligned(layout.size(), layout.align())
+        }
+    }
+
+    unsafe fn dealloc(&self, _: *mut u8, _: Layout) {}
+}
+
+#[global_allocator]
+static HEAP: SimpleAlloc = SimpleAlloc;
+
+// https://docs.succinct.xyz/docs/sp1/security/rv32im-implementation#reserved-memory-regions
+pub const MAX_MEMORY: usize = 0x78000000;
+static mut HEAP_POS: usize = 0;
+#[allow(clippy::missing_safety_doc)]
+#[unsafe(no_mangle)]
+pub unsafe extern "C" fn sys_alloc_aligned(bytes: usize, align: usize) -> *mut u8 {
+    unsafe extern "C" {
+        // https://lld.llvm.org/ELF/linker_script.html#sections-command
+        // `_end` is the last global variable defined by the linker. Its address is the beginning of heap data.
+        unsafe static _end: u8;
+    }
+
+    // SAFETY: Single threaded, so nothing else can touch this while we're working.
+    let mut heap_pos = unsafe { HEAP_POS };
+
+    if heap_pos == 0 {
+        heap_pos = unsafe { (&_end) as *const u8 as usize };
+    }
+
+    let offset = heap_pos & (align - 1);
+    if offset != 0 {
+        heap_pos += align - offset;
+    }
+
+    let ptr = heap_pos as *mut u8;
+    let (heap_pos, overflowed) = heap_pos.overflowing_add(bytes);
+
+    if overflowed || MAX_MEMORY < heap_pos {
+        panic!("Memory limit exceeded (0x78000000)");
+    }
+
+    unsafe { HEAP_POS = heap_pos };
+    ptr
+}
+
+// Assume single-threaded.
+#[cfg(all(target_arch = "riscv32", target_feature = "a"))]
+#[unsafe(no_mangle)]
+fn _critical_section_1_0_acquire() -> u32
+{
+    return 0;
+}
+
+#[cfg(all(target_arch = "riscv32", target_feature = "a"))]
+#[unsafe(no_mangle)]
+fn _critical_section_1_0_release(_: u32)
+{}
+
+// Assume single-threaded.
+#[cfg(all(target_arch = "riscv64", target_feature = "a"))]
+#[unsafe(no_mangle)]
+fn _critical_section_1_0_acquire() -> u64
+{
+    return 0;
+}
+
+#[cfg(all(target_arch = "riscv64", target_feature = "a"))]
+#[unsafe(no_mangle)]
+fn _critical_section_1_0_release(_: u64)
+{}