krun_set_exec now also preserves raw argv (passed as base64-encoded variables) which is needed when booting FreeBSD

Signed-off-by: Jan Noha <nohajc@gmail.com>

Author: nohajc

Cargo.lock

@@ -33,6 +33,7 @@ polly = { path = "../polly" }
 utils = { path = "../utils" }
 vmm = { path = "../vmm" }
 rand = "0.9.2"
+base64 = "0.22.1"
 
 [target.'cfg(target_os = "macos")'.dependencies]
 hvf = { path = "../hvf" }

src/libkrun/Cargo.toml

@@ -1,6 +1,7 @@
 #[macro_use]
 extern crate log;
 
+use base64::prelude::*;
 use crossbeam_channel::unbounded;
 #[cfg(feature = "blk")]
 use devices::virtio::block::ImageType;
@@ -1190,6 +1191,24 @@ unsafe fn collapse_str_array(array: &[*const c_char]) -> Result<String, std::str
     Ok(strvec.join(" "))
 }
 
+// unlike collapse_str_array, this doesn't do the UTF-8 conversion
+// and just keeps the null-terminated strings as raw bytes
+unsafe fn flatten_cstr_array(array: &[*const c_char]) -> Vec<u8> {
+    let mut bytevec = Vec::new();
+
+    for item in array.iter().take(MAX_ARGS) {
+        if item.is_null() {
+            break;
+        } else {
+            let cs = CStr::from_ptr(*item);
+            bytevec.extend_from_slice(cs.to_bytes());
+            bytevec.push(0);
+        }
+    }
+
+    bytevec
+}
+
 #[allow(clippy::format_collect)]
 #[allow(clippy::missing_safety_doc)]
 #[no_mangle]
@@ -1220,7 +1239,14 @@ pub unsafe extern "C" fn krun_set_exec(
         "".to_string()
     };
 
-    let env = if !c_envp.is_null() {
+    let args_raw = if !c_argv.is_null() {
+        let argv_array: &[*const c_char] = slice::from_raw_parts(c_argv, MAX_ARGS);
+        flatten_cstr_array(argv_array)
+    } else {
+        vec![]
+    };
+
+    let mut env = if !c_envp.is_null() {
         let envp_array: &[*const c_char] = slice::from_raw_parts(c_envp, MAX_ARGS);
         match collapse_str_array(envp_array) {
             Ok(s) => s,
@@ -1235,6 +1261,11 @@ pub unsafe extern "C" fn krun_set_exec(
             .collect()
     };
 
+    // KRUN_INIT_ARGVXX="<base64>" must have at most 128 bytes (KENV_MVALLEN on FreeBSD)
+    for (i, args_part) in args_raw.chunks(78).enumerate() {
+        env += &format!(" KRUN_INIT_ARGV{}={}", i, BASE64_STANDARD.encode(args_part));
+    }
+
     match CTX_MAP.lock().unwrap().entry(ctx_id) {
         Entry::Occupied(mut ctx_cfg) => {
             let cfg = ctx_cfg.get_mut();

src/libkrun/src/lib.rs

@@ -572,11 +572,15 @@ pub fn build_microvm(
     )?;
 
     let vcpu_config = vm_resources.vcpu_config();
+    let mut kernel_is_freebsd = false;
 
     // Clone the command-line so that a failed boot doesn't pollute the original.
     #[allow(unused_mut)]
     let mut kernel_cmdline = Cmdline::new(arch::CMDLINE_MAX_SIZE);
     if let Some(cmdline) = payload_config.kernel_cmdline {
+        if cmdline.starts_with("FreeBSD:") {
+            kernel_is_freebsd = true;
+        }
         kernel_cmdline.insert_str(cmdline.as_str()).unwrap();
     } else if let Some(cmdline) = &vm_resources.kernel_cmdline.prolog {
         kernel_cmdline.insert_str(cmdline).unwrap();
@@ -1042,7 +1046,9 @@ pub fn build_microvm(
     }
 
     if let Some(s) = &vm_resources.kernel_cmdline.epilog {
-        vmm.kernel_cmdline.insert_str(s).unwrap();
+        if !kernel_is_freebsd {
+            vmm.kernel_cmdline.insert_str(s).unwrap();
+        }
     };
 
     // Write the kernel command line to guest memory. This is x86_64 specific, since on