bind mounts

src/spawner.rs

@@ -10,6 +10,7 @@ use std::ffi::CString;
 use std::fs::File;
 use std::io::Read;
 use std::os::unix::io::AsRawFd;
+use std::path::PathBuf;
 
 use nix::unistd;
 
@@ -29,10 +30,15 @@ impl<'a> Spawner<'a> {
 
             match &entrypoint.trigger {
                 Trigger::Startup => {
+                    let binary = PathBuf::from(self.binary).canonicalize()?;
+
+                    let mut builder = VoidBuilder::new();
+                    builder.mount(binary, "/entrypoint");
+
                     let closure = || {
                         let args = self.prepare_args(name, &entrypoint.args, None);
 
-                        if let Err(e) = unistd::execv(&CString::new(self.binary).unwrap(), &args)
+                        if let Err(e) = unistd::execv(&CString::new("/entrypoint").unwrap(), &args)
                             .map_err(|e| Error::Nix {
                                 msg: "execv",
                                 src: e,
@@ -45,14 +51,15 @@ impl<'a> Spawner<'a> {
                         }
                     };
 
-                    let mut builder = VoidBuilder::new();
                     builder.spawn(closure)?;
                 }
 
                 Trigger::Pipe(s) => {
                     let pipe = self.pipes.get_mut(s).unwrap().take_read();
+                    let binary = PathBuf::from(self.binary).canonicalize()?;
 
                     let mut builder = VoidBuilder::new();
+                    builder.mount(binary, "/entrypoint");
                     builder.keep_fd(&pipe);
 
                     let closure = || match self.pipe_trigger(pipe, entrypoint, name) {
@@ -87,7 +94,7 @@ impl<'a> Spawner<'a> {
                     let pipe_trigger = std::str::from_utf8(&buf[0..read_bytes]).unwrap();
                     let args = self.prepare_args_ref(name, &spec.args, Some(pipe_trigger));
 
-                    if let Err(e) = unistd::execv(&CString::new(self.binary).unwrap(), &args)
+                    if let Err(e) = unistd::execv(&CString::new("/entrypoint").unwrap(), &args)
                         .map_err(|e| Error::Nix {
                             msg: "execv",
                             src: e,

src/void.rs

@@ -6,7 +6,7 @@ use crate::{Error, Result};
 use std::collections::{HashMap, HashSet};
 use std::fs;
 use std::os::unix::io::{AsRawFd, RawFd};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 
 use nix::mount::{mount, umount2, MntFlags, MsFlags};
 use nix::sched::unshare;
@@ -31,8 +31,8 @@ impl VoidBuilder {
     }
 
     #[allow(dead_code)]
-    pub fn mount(&mut self, src: PathBuf, dst: PathBuf) -> &mut Self {
-        self.mounts.insert(src, dst);
+    pub fn mount<T1: AsRef<Path>, T2: AsRef<Path>>(&mut self, src: T1, dst: T2) -> &mut Self {
+        self.mounts.insert(src.as_ref().into(), dst.as_ref().into());
         self
     }
 
@@ -144,10 +144,37 @@ impl VoidBuilder {
         // chdir after
         std::env::set_current_dir("/")?;
 
-        // TODO: mount requested mounts
+        // mount paths before unmounting old_root
+        for (src, dst) in &self.mounts {
+            let src = PathBuf::from("/old_root/").join(src.strip_prefix("/").unwrap_or(src));
+            let dst = PathBuf::from("/").join(dst);
+
+            debug!("mounting `{:?}` as `{:?}`", src, dst);
+
+            // create the target
+            let src_data = fs::metadata(&src)?;
+            if src_data.is_dir() {
+                fs::create_dir_all(&dst)?;
+            } else {
+                fs::write(&dst, b"")?;
+            }
+
+            // bind mount
+            mount(
+                Some(&src),
+                &dst,
+                Option::<&str>::None,
+                MsFlags::MS_BIND,
+                Option::<&str>::None,
+            )
+            .map_err(|e| Error::Nix {
+                msg: "mount",
+                src: e,
+            })?;
+        }
 
         // unmount the old root
-        umount2("old_root/", MntFlags::MNT_DETACH).map_err(|e| Error::Nix {
+        umount2("/old_root/", MntFlags::MNT_DETACH).map_err(|e| Error::Nix {
             msg: "umount2",
             src: e,
         })?;