Use Box64 with muvm

crates/muvm/src/guest/bin/muvm-guest.rs

@@ -8,6 +8,7 @@ use log::debug;
 use muvm::env::find_muvm_exec;
 use muvm::guest::cli_options::options;
 use muvm::guest::fex::setup_fex;
+use muvm::guest::box64::setup_box;
 use muvm::guest::mount::mount_filesystems;
 use muvm::guest::net::configure_network;
 use muvm::guest::socket::setup_socket_proxy;
@@ -52,7 +53,7 @@ fn main() -> Result<()> {
 
     Command::new("/usr/lib/systemd/systemd-udevd").spawn()?;
 
-    setup_fex()?;
+    setup_fex().unwrap_or_else(|_error|setup_box().unwrap());
 
     configure_network()?;
 

crates/muvm/src/guest/box64.rs

@@ -0,0 +1,44 @@
+use std::fs::File;
+use std::io::Write;
+
+use anyhow::{Context, Result};
+
+use crate::utils::env::find_in_path;
+
+const BOX32_BINFMT_MISC_RULE: &str = ":BOX32:M:0:\\x7fELF\\x01\\x01\\x01\\x00\\x00\\x00\\x00\\\
+                                        x00\\x00\\x00\\x00\\x00\\x02\\x00\\x03\\x00:\\xff\\xff\\\
+                                        xff\\xff\\xff\\xfe\\xfe\\x00\\x00\\x00\\x00\\xff\\xff\\\
+                                        xff\\xff\\xff\\xfe\\xff\\xff\\xff:${BOX64}:POCF";
+const BOX64_BINFMT_MISC_RULE: &str =
+    ":BOX64:M:0:\\x7fELF\\x02\\x01\\x01\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x00\\x02\\\
+     x00\\x3e\\x00:\\xff\\xff\\xff\\xff\\xff\\xfe\\xfe\\x00\\x00\\x00\\x00\\xff\\xff\\xff\\xff\\\
+     xff\\xfe\\xff\\xff\\xff:${BOX64}:POCF";
+
+pub fn setup_box() -> Result<()> {
+    let box64_path =
+        find_in_path("box64").context("Failed to check existence of `box64`")?;
+    let Some(box64_path) = box64_path else {
+        return Ok(());
+    };
+    let box64_path = box64_path
+        .to_str()
+        .context("Failed to process `box64` path as it contains invalid UTF-8")?;
+
+    let mut file = File::options()
+        .write(true)
+        .open("/proc/sys/fs/binfmt_misc/register")
+        .context("Failed to open binfmt_misc/register for writing")?;
+
+    {
+        let rule = BOX32_BINFMT_MISC_RULE.replace("${BOX64}", box64_path);
+        file.write_all(rule.as_bytes())
+            .context("Failed to register `Box32` binfmt_misc rule")?;
+    }
+    {
+        let rule = BOX64_BINFMT_MISC_RULE.replace("${BOX64}", box64_path);
+        file.write_all(rule.as_bytes())
+            .context("Failed to register `Box64` binfmt_misc rule")?;
+    }
+
+    Ok(())
+}

crates/muvm/src/guest/mod.rs

@@ -1,5 +1,6 @@
 pub mod cli_options;
 pub mod fex;
+pub mod box64;
 pub mod mount;
 pub mod net;
 pub mod socket;