efi: update the ESP by creating a tmpdir and RENAME_EXCHANGE

Cargo.toml

@@ -22,9 +22,11 @@ path = "src/main.rs"
 anyhow = "1.0"
 bincode = "1.3.2"
 cap-std-ext = "4.0.0"
+camino = "1.1.7"
 chrono = { version = "0.4.38", features = ["serde"] }
 clap = { version = "4.5", default-features = false, features = ["cargo", "derive", "std", "help", "usage", "suggestions"] }
 env_logger = "0.11"
+fail = { version = "0.5", features = ["failpoints"] }
 fn-error-context = "0.2.1"
 fs2 = "0.4.3"
 hex = "0.4.3"

src/bootupd.rs

@@ -396,6 +396,7 @@ pub(crate) fn print_status(status: &Status) -> Result<()> {
 }
 
 pub(crate) fn client_run_update() -> Result<()> {
+    crate::try_fail_point!("update");
     let status: Status = status()?;
     if status.components.is_empty() && status.adoptable.is_empty() {
         println!("No components installed.");
@@ -489,3 +490,17 @@ pub(crate) fn client_run_validate() -> Result<()> {
     }
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_failpoint_update() {
+        let guard = fail::FailScenario::setup();
+        fail::cfg("update", "return").unwrap();
+        let r = client_run_update();
+        assert_eq!(r.is_err(), true);
+        guard.teardown();
+    }
+}

src/efi.rs

@@ -141,7 +141,7 @@ impl Efi {
             log::debug!("Not booted via EFI, skipping firmware update");
             return Ok(());
         }
-        let sysroot = Dir::open_ambient_dir(&Path::new("/"), cap_std::ambient_authority())?;
+        let sysroot = Dir::open_ambient_dir("/", cap_std::ambient_authority())?;
         let product_name = get_product_name(&sysroot)?;
         log::debug!("Get product name: {product_name}");
         assert!(product_name.len() > 0);

src/failpoints.rs

@@ -0,0 +1,21 @@
+//! Wrappers and utilities on top of the `fail` crate.
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+/// TODO: Use https://github.com/tikv/fail-rs/pull/68 once it merges
+/// copy from https://github.com/coreos/rpm-ostree/commit/aa8d7fb0ceaabfaf10252180e2ddee049d07aae3#diff-adcc419e139605fae34d17b31418dbaf515af2fe9fb766fcbdb2eaad862b3daa
+#[macro_export]
+macro_rules! try_fail_point {
+    ($name:expr) => {{
+        if let Some(e) = fail::eval($name, |msg| {
+            let msg = msg.unwrap_or_else(|| "synthetic failpoint".to_string());
+            anyhow::Error::msg(msg)
+        }) {
+            return Err(From::from(e));
+        }
+    }};
+    ($name:expr, $cond:expr) => {{
+        if $cond {
+            $crate::try_fail_point!($name);
+        }
+    }};
+}