test: integrate riscv64im-unknown-openvm-elf target into build system

benchmarks/guest/base64_json/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/bincode/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/bubblesort/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

benchmarks/guest/ecrecover/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/fibonacci/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use openvm::io::{read, reveal_u64};

benchmarks/guest/fibonacci_iterative/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/fibonacci_recursive/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/keccak256/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

benchmarks/guest/keccak256_iter/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

benchmarks/guest/kitchen-sink/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/pairing/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

benchmarks/guest/quicksort/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

benchmarks/guest/regex/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/revm_snailtracer/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/revm_transfer/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 //! Program to match the workload of <https://github.com/bluealloy/revm/blob/900409f134c1cbd4489d370a6b037f354afa4a5c/crates/revm/benches/bench.rs#L68>

benchmarks/guest/rkyv/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/sha256/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

benchmarks/guest/sha256_iter/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

benchmarks/guest/sha2_bench/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

crates/cli/templates/main.rs

@@ -1,5 +1,5 @@
 // src/main.rs
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use openvm::io::{read, reveal_u64};

crates/cli/tests/programs/fibonacci/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

crates/cli/tests/programs/multi/calculator/examples/fibonacci.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

crates/cli/tests/programs/multi/calculator/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use calculator::count_primes;

crates/cli/tests/programs/multi/string-utils/examples/palindrome.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

crates/cli/tests/programs/multi/string-utils/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

crates/continuations/programs/examples/fibonacci.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use openvm::io::{read, reveal_u64};

crates/continuations/programs/examples/multiple.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use openvm::io::read;

crates/sdk/guest/fib/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 openvm::entry!(main);

crates/sdk/guest/little/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

crates/sdk/guest/p256/src/main.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

crates/sdk/programs/examples/fibonacci.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use openvm::io::{read, reveal_u64};

crates/sdk/programs/examples/verify-stark.rs

@@ -1,4 +1,4 @@
-#![cfg_attr(target_os = "none", no_main)]
+#![cfg_attr(any(target_os = "none", target_os = "openvm"), no_main)]
 #![cfg_attr(not(feature = "std"), no_std)]
 
 extern crate alloc;

crates/toolchain/build/src/lib.rs

@@ -19,16 +19,15 @@ pub use self::config::GuestOptions;
 
 mod config;
 
-/// Custom rustc target for the openvm guest. The JSON spec lives at
-/// `<RUSTC_TARGET>.json` next to this crate.
-pub const RUSTC_TARGET: &str = "riscv64im-openvm-none-elf";
+/// Custom rustc target for the openvm guest.
+pub const RUSTC_TARGET: &str = "riscv64im-unknown-openvm-elf";
 
 /// Directory containing the target JSON; passed to cargo as `RUST_TARGET_PATH`.
 pub fn rustc_target_spec_dir() -> &'static Path {
     Path::new(env!("CARGO_MANIFEST_DIR"))
 }
 /// The default Rust toolchain name to use if OPENVM_RUST_TOOLCHAIN is not set
-pub const DEFAULT_RUSTUP_TOOLCHAIN_NAME: &str = "nightly-2026-01-18";
+pub const DEFAULT_RUSTUP_TOOLCHAIN_NAME: &str = "openvm-rv64";
 
 /// Get the Rust toolchain name from environment variable or default
 pub fn get_rustup_toolchain_name() -> String {
@@ -251,7 +250,8 @@ fn sanitized_cmd(tool: &str) -> Command {
 
 /// Creates a std::process::Command to execute the given cargo
 /// command in an environment suitable for targeting the zkvm guest.
-pub fn cargo_command(subcmd: &str, rust_flags: &[&str]) -> Command {
+/// If `with_std` is true, `std` is added to the `-Zbuild-std` crate list.
+pub fn cargo_command(subcmd: &str, rust_flags: &[&str], with_std: bool) -> Command {
     let toolchain = format!("+{}", get_rustup_toolchain_name());
 
     let rustc = sanitized_cmd("rustup")
@@ -271,12 +271,12 @@ pub fn cargo_command(subcmd: &str, rust_flags: &[&str]) -> Command {
         args.push("--locked");
     }
 
-    args.extend_from_slice(&[
-        "-Z",
-        "build-std=alloc,core,panic_abort",
-        "-Z",
-        "build-std-features=compiler-builtins-mem",
-    ]);
+    let build_std = if with_std {
+        "build-std=alloc,core,panic_abort,std"
+    } else {
+        "build-std=alloc,core,panic_abort"
+    };
+    args.extend_from_slice(&["-Z", build_std, "-Z", "build-std-features=compiler-builtins-mem"]);
 
     println!("Building guest package: cargo {}", args.join(" "));
 
@@ -398,16 +398,23 @@ pub fn build_generic(guest_opts: &GuestOptions) -> Result<PathBuf, Option<i32>>
 
     // Check if the required toolchain and rust-src component are installed, and if not, install
     // them. This requires that `rustup` is installed.
-    if let Err(code) = ensure_toolchain_installed(&get_rustup_toolchain_name(), &["rust-src"]) {
-        eprintln!("rustup toolchain commands failed. Please ensure rustup is installed (https://www.rust-lang.org/tools/install)");
-        return Err(Some(code));
+    // Skip for linked toolchains (e.g. custom-built rustc) where rustup component commands
+    // don't apply — the toolchain is expected to already include rust-src.
+    let toolchain_name = get_rustup_toolchain_name();
+    let is_linked_toolchain = !toolchain_name.contains("nightly") && !toolchain_name.contains("stable") && !toolchain_name.contains("beta");
+    if !is_linked_toolchain {
+        if let Err(code) = ensure_toolchain_installed(&toolchain_name, &["rust-src"]) {
+            eprintln!("rustup toolchain commands failed. Please ensure rustup is installed (https://www.rust-lang.org/tools/install)");
+            return Err(Some(code));
+        }
     }
 
     let target_dir = guest_opts.target_dir.as_ref().unwrap();
     fs::create_dir_all(target_dir).unwrap();
     let rust_flags: Vec<_> = guest_opts.rustc_flags.iter().map(|s| s.as_str()).collect();
 
-    let mut cmd = cargo_command("build", &rust_flags);
+    let with_std = guest_opts.features.iter().any(|f| f == "std");
+    let mut cmd = cargo_command("build", &rust_flags, with_std);
 
     if !guest_opts.features.is_empty() {
         cmd.args(["--features", guest_opts.features.join(",").as_str()]);

crates/toolchain/openvm/src/lib.rs

@@ -20,6 +20,8 @@ pub use openvm_riscv_guest::*;
 
 #[cfg(openvm_intrinsics)]
 mod getrandom;
+#[cfg(openvm_intrinsics)]
+mod pal_abi;
 pub mod io;
 pub mod process;
 pub mod serde;
@@ -71,7 +73,7 @@ fn _fault() -> ! {
 ///
 /// fn main() { }
 /// ```
-#[cfg(all(not(feature = "std"), openvm_intrinsics))]
+#[cfg(openvm_intrinsics)]
 #[macro_export]
 macro_rules! entry {
     ($path:path) => {
@@ -88,9 +90,8 @@ macro_rules! entry {
         }
     };
 }
-/// This macro does nothing. You should name the function `main` so that the normal rust main
-/// function setup is used.
-#[cfg(any(feature = "std", not(openvm_intrinsics)))]
+/// This macro does nothing when not compiling for the guest target.
+#[cfg(not(openvm_intrinsics))]
 #[macro_export]
 macro_rules! entry {
     ($path:path) => {};