install: Use zipl to install bootloader on s390x

Running zipl via ostree does not work correctly on a loop deivce.
This patch changes bootc to execute zipl directly with appropriate
command line options for installation on a loop device.

Signed-off-by: Yohei Ueda <yohei@jp.ibm.com>

lib/src/bootloader.rs

@@ -1,4 +1,4 @@
-use anyhow::Result;
+use anyhow::{anyhow, Context, Result};
 use camino::Utf8Path;
 use fn_error_context::context;
 
@@ -26,3 +26,77 @@ pub(crate) fn install_via_bootupd(
         .verbose()
         .run()
 }
+
+#[context("Installing bootloader using zipl")]
+pub(crate) fn install_via_zipl(device: &Utf8Path, boot_uuid: &str) -> Result<()> {
+    // Identify the target boot partition from UUID
+    let fs = crate::mount::inspect_filesystem_by_uuid(boot_uuid)?;
+    let boot_dir = Utf8Path::new(&fs.target);
+    let maj_min = fs.maj_min;
+
+    // Ensure that the found partition is a part of the target device
+    crate::blockdev::list_dev(device)?
+        .children
+        .context("not found")?
+        .iter()
+        .find(|dev| dev.maj_min == Some(maj_min.clone()))
+        .ok_or(anyhow!("not found"))?;
+
+    // Get an offset of the target partition by reading /sys/dev/block/<major:minor>/start
+    let sysfs_start_path = Utf8Path::new("/sys/dev/block").join(&maj_min).join("start");
+    let boot_offset = match std::fs::read_to_string(sysfs_start_path.clone()) {
+        Ok(v) => v.trim().parse::<i64>().map_err(|e| anyhow!(e)),
+        Err(e) if e.kind() == std::io::ErrorKind::NotFound => Ok(0), // partition-less disk
+        Err(e) => Err(anyhow!(e)),
+    }
+    .with_context(|| format!("reading {sysfs_start_path:?}"))?;
+
+    // Find the default BLS conf under /boot/loader/entries
+    // TODO: utilize the BLS parser in ostree
+    let bls_dir = boot_dir.join("boot/loader/entries");
+    let ls_desc = format!("running ls to find the default BLS configuration under {bls_dir}");
+    let ls_task = Task::new(ls_desc, "ls").args(["--sort=version", "--reverse", bls_dir.as_str()]);
+    let ls_out = ls_task.quiet().read()?;
+
+    let bls_name = ls_out
+        .lines()
+        .find(|f| f.ends_with(".conf"))
+        .with_context(|| format!("no BLS conf under {bls_dir:?}"))?;
+    let bls_path = bls_dir.join(bls_name);
+    let bls_conf =
+        std::fs::read_to_string(&bls_path).with_context(|| format!("reading {bls_path:?}"))?;
+
+    let mut kernel = None;
+    let mut initrd = None;
+    let mut options = None;
+
+    for line in bls_conf.lines() {
+        match line.split_once(char::is_whitespace) {
+            Some(("linux", val)) => kernel = Some(val.trim().trim_start_matches('/')),
+            Some(("initrd", val)) => initrd = Some(val.trim().trim_start_matches('/')),
+            Some(("options", val)) => options = Some(val.trim()),
+            _ => (),
+        }
+    }
+
+    let kernel = kernel.ok_or_else(|| anyhow!("missing 'linux' key in default BLS config"))?;
+    let initrd = initrd.ok_or_else(|| anyhow!("missing 'initrd' key in default BLS config"))?;
+    let options = options.ok_or_else(|| anyhow!("missing 'options' key in default BLS config"))?;
+
+    let image = boot_dir.join(kernel).canonicalize_utf8()?;
+    let ramdisk = boot_dir.join(initrd).canonicalize_utf8()?;
+
+    // Execute the zipl command to install bootloader
+    let zipl_desc = format!("running zipl to install bootloader on {device}");
+    let zipl_task = Task::new(&zipl_desc, "zipl")
+        .args(["--target", boot_dir.as_str()])
+        .args(["--image", image.as_str()])
+        .args(["--ramdisk", ramdisk.as_str()])
+        .args(["--parameters", options])
+        .args(["--targetbase", device.as_str()])
+        .args(["--targettype", "SCSI"])
+        .args(["--targetblocksize", "512"])
+        .args(["--targetoffset", &boot_offset.to_string()])
+        .args(["--add-files", "--verbose"]);
+    zipl_task.verbose().run().context(zipl_desc)
+}

lib/src/install.rs

@@ -573,15 +573,9 @@ async fn initialize_ostree_root_from_self(
         crate::lsm::ensure_dir_labeled(rootfs_dir, "boot", None, 0o755.into(), sepolicy)?;
     }
 
-    // Default to avoiding grub2-mkconfig etc., but we need to use zipl on s390x.
-    // TODO: Lower this logic into ostree proper.
-    let bootloader = if cfg!(target_arch = "s390x") {
-        "zipl"
-    } else {
-        "none"
-    };
     for (k, v) in [
-        ("sysroot.bootloader", bootloader),
+        // Default to avoiding grub2-mkconfig etc.
+        ("sysroot.bootloader", "none"),
         // Always flip this one on because we need to support alongside installs
         // to systems without a separate boot partition.
         ("sysroot.bootprefix", "true"),
@@ -1240,7 +1234,12 @@ async fn install_to_filesystem_impl(state: &State, rootfs: &mut RootSetup) -> Re
             .context("Writing aleph version")?;
     }
 
-    crate::bootloader::install_via_bootupd(&rootfs.device, &rootfs.rootfs, &state.config_opts)?;
+    if cfg!(target_arch = "s390x") {
+        // TODO: Integrate s390x support into install_via_bootupd
+        crate::bootloader::install_via_zipl(&rootfs.device, boot_uuid)?;
+    } else {
+        crate::bootloader::install_via_bootupd(&rootfs.device, &rootfs.rootfs, &state.config_opts)?;
+    }
     tracing::debug!("Installed bootloader");
 
     // Finalize mounted filesystems