lib/deploy: Add support for overlay initrds

In FCOS and RHCOS, the need to configure software in the initramfs has
come up multiple times. Sometimes, using kernel arguments suffices.
Other times, it really must be a configuration file. Rebuilding the
initramfs on the client-side however is a costly operation. Not only
does it add complexity to the update workflow, it also erodes a lot of
the value obtained from using the baked "blessed" initramfs from the
tree itself.

One elegant way to address this is to allow specifying multiple
initramfses. This is supported by most bootloaders (notably GRUB) and
results in each initrd being overlayed on top of each other.

This patch allows libostree clients to leverage this so that they can
avoid regenerating the initramfs entirely. libostree itself is agnostic
as to what kind and how much data overlay initrds contain. It's up to
the clients to enforce such boundaries.

To implement this, we add a new ostree_sysroot_stage_overlay_initrd
which takes a file descriptor and returns a checksum. Then users can
pass these checksums when calling the deploy APIs via the new array
option `overlay_initrds`. We copy these files into `/boot` and add them
to the BLS as another `initrd` entry.

1 files changed, 61 insertions, 7 deletions

diff --git a/src/ostree/ot-admin-builtin-deploy.c b/src/ostree/ot-admin-builtin-deploy.c
index bcece3f6..8156cc15 100644
--- a/src/ostree/ot-admin-builtin-deploy.c
+++ b/src/ostree/ot-admin-builtin-deploy.c
@@ -44,6 +44,7 @@ static gboolean opt_kernel_proc_cmdline;
 static char *opt_osname;
 static char *opt_origin_path;
 static gboolean opt_kernel_arg_none;
+static char **opt_overlay_initrds;
 
 static GOptionEntry options[] = {
   { "os", 0, 0, G_OPTION_ARG_STRING, &opt_osname, "Use a different operating system root than the current one", "OSNAME" },
@@ -59,6 +60,7 @@ static GOptionEntry options[] = {
   { "karg", 0, 0, G_OPTION_ARG_STRING_ARRAY, &opt_kernel_argv, "Set kernel argument, like root=/dev/sda1; this overrides any earlier argument with the same name", "NAME=VALUE" },
   { "karg-append", 0, 0, G_OPTION_ARG_STRING_ARRAY, &opt_kernel_argv_append, "Append kernel argument; useful with e.g. console= that can be used multiple times", "NAME=VALUE" },
   { "karg-none", 0, 0, G_OPTION_ARG_NONE, &opt_kernel_arg_none, "Do not import kernel arguments", NULL },
+  { "overlay-initrd", 0, 0, G_OPTION_ARG_STRING_ARRAY, &opt_overlay_initrds, "Overlay iniramfs file", "FILE" },
   { NULL }
 };
 
@@ -167,24 +169,76 @@ ot_admin_builtin_deploy (int argc, char **argv, OstreeCommandInvocation *invocat
       ostree_kernel_args_append_argv (kargs, opt_kernel_argv_append);
     }
 
-  g_autoptr(OstreeDeployment) new_deployment = NULL;
+  g_autoptr(GPtrArray) overlay_initrd_chksums = NULL;
+  for (char **it = opt_overlay_initrds; it && *it; it++)
+    {
+      const char *path = *it;
+
+      glnx_autofd int fd = -1;
+      if (!glnx_openat_rdonly (AT_FDCWD, path, TRUE, &fd, error))
+        return FALSE;
+
+      g_autofree char *chksum = NULL;
+      if (!ostree_sysroot_stage_overlay_initrd (sysroot, fd, &chksum, cancellable, error))
+        return FALSE;
+
+      if (!overlay_initrd_chksums)
+        overlay_initrd_chksums = g_ptr_array_new_full (g_strv_length (opt_overlay_initrds), g_free);
+      g_ptr_array_add (overlay_initrd_chksums, g_steal_pointer (&chksum));
+    }
+
+  if (overlay_initrd_chksums)
+    g_ptr_array_add (overlay_initrd_chksums, NULL);
+
   g_auto(GStrv) kargs_strv = kargs ? ostree_kernel_args_to_strv (kargs) : NULL;
+
+  OstreeSysrootDeployTreeOpts opts = {
+    .override_kernel_argv = kargs_strv,
+    .overlay_initrds = overlay_initrd_chksums ? (char**)overlay_initrd_chksums->pdata : NULL,
+  };
+
+  g_autoptr(OstreeDeployment) new_deployment = NULL;
   if (opt_stage)
     {
       if (opt_retain_pending || opt_retain_rollback)
         return glnx_throw (error, "--stage cannot currently be combined with --retain arguments");
       if (opt_not_as_default)
         return glnx_throw (error, "--stage cannot currently be combined with --not-as-default");
-      if (!ostree_sysroot_stage_tree (sysroot, opt_osname, revision, origin, merge_deployment,
-                                      kargs_strv, &new_deployment, cancellable, error))
-        return FALSE;
+      /* use old API if we can to exercise it in CI */
+      if (!overlay_initrd_chksums)
+        {
+          if (!ostree_sysroot_stage_tree (sysroot, opt_osname, revision, origin,
+                                          merge_deployment, kargs_strv, &new_deployment,
+                                          cancellable, error))
+            return FALSE;
+        }
+      else
+        {
+          if (!ostree_sysroot_stage_tree_with_options (sysroot, opt_osname, revision,
+                                                       origin, merge_deployment, &opts,
+                                                       &new_deployment, cancellable, error))
+            return FALSE;
+        }
       g_assert (new_deployment);
     }
   else
     {
-      if (!ostree_sysroot_deploy_tree (sysroot, opt_osname, revision, origin, merge_deployment,
-                                       kargs_strv, &new_deployment, cancellable, error))
-        return FALSE;
+      /* use old API if we can to exercise it in CI */
+      if (!overlay_initrd_chksums)
+        {
+          if (!ostree_sysroot_deploy_tree (sysroot, opt_osname, revision, origin,
+                                           merge_deployment, kargs_strv, &new_deployment,
+                                           cancellable, error))
+            return FALSE;
+        }
+      else
+        {
+          if (!ostree_sysroot_deploy_tree_with_options (sysroot, opt_osname, revision,
+                                                        origin, merge_deployment, &opts,
+                                                        &new_deployment, cancellable,
+                                                        error))
+            return FALSE;
+        }
       g_assert (new_deployment);
 
       OstreeSysrootSimpleWriteDeploymentFlags flags = OSTREE_SYSROOT_SIMPLE_WRITE_DEPLOYMENT_FLAGS_NO_CLEAN;