Thread sysroot through install flow

More incremental work on #108

src/bootupd.rs

@@ -23,6 +23,7 @@ pub(crate) enum ClientRequest {
 }
 
 pub(crate) fn install(source_root: &str, dest_root: &str) -> Result<()> {
+    let source_root = openat::Dir::open(source_root)?;
     SavedState::ensure_not_present(dest_root)
         .context("failed to install, invalid re-install attempted")?;
 
@@ -35,7 +36,7 @@ pub(crate) fn install(source_root: &str, dest_root: &str) -> Result<()> {
     let mut state = SavedState::default();
     for component in components.values() {
         let meta = component
-            .install(source_root, dest_root)
+            .install(&source_root, dest_root)
             .with_context(|| format!("installing component {}", component.name()))?;
         state.installed.insert(component.name().into(), meta);
     }

src/component.rs

@@ -43,7 +43,7 @@ pub(crate) trait Component {
     /// of a filesystem root, the component should query the mount point to
     /// determine the block device.
     /// This will be run during a disk image build process.
-    fn install(&self, src_root: &str, dest_root: &str) -> Result<InstalledContent>;
+    fn install(&self, src_root: &openat::Dir, dest_root: &str) -> Result<InstalledContent>;
 
     /// Implementation of `bootupd generate-update-metadata` for a given component.
     /// This expects to be run during an "image update build" process.  For CoreOS

src/efi.rs

@@ -6,6 +6,7 @@
 
 use std::collections::{BTreeMap, BTreeSet};
 use std::io::prelude::*;
+use std::os::unix::io::AsRawFd;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
@@ -102,27 +103,27 @@ impl Component for EFI {
         })
     }
 
-    fn install(&self, src_root: &str, dest_root: &str) -> Result<InstalledContent> {
-        let src_rootd = openat::Dir::open(src_root)?;
-        let meta = if let Some(meta) = get_component_update(&src_rootd, self)? {
+    fn install(&self, src_root: &openat::Dir, dest_root: &str) -> Result<InstalledContent> {
+        let meta = if let Some(meta) = get_component_update(&src_root, self)? {
             meta
         } else {
             anyhow::bail!("No update metadata for component {} found", self.name());
         };
-        let srcdir = component_updatedir(src_root, self);
-        let srcd = openat::Dir::open(&srcdir)
-            .with_context(|| format!("opening src dir {}", srcdir.display()))?;
-        let ft = crate::filetree::FileTree::new_from_dir(&srcd)?;
+        let srcdir_name = component_updatedirname(self);
+        let ft = crate::filetree::FileTree::new_from_dir(&src_root.sub_dir(&srcdir_name)?)?;
         let destdir = Path::new(dest_root).join(MOUNT_PATH);
         {
             let destd = openat::Dir::open(&destdir)
                 .with_context(|| format!("opening dest dir {}", destdir.display()))?;
             validate_esp(&destd)?;
         }
+        // TODO - add some sort of API that allows directly setting the working
+        // directory to a file descriptor.
         let r = std::process::Command::new("cp")
             .args(&["-rp", "--reflink=auto"])
-            .arg(&srcdir)
+            .arg(&srcdir_name)
             .arg(&destdir)
+            .current_dir(format!("/proc/self/fd/{}", src_root.as_raw_fd()))
             .status()?;
         if !r.success() {
             anyhow::bail!("Failed to copy");