sysroot: Preserve custom bootconfig keys across staged deployment finalization

When a deployment is staged via ostree_sysroot_stage_tree_with_options(),
the deployment metadata is serialized to /run/ostree/staged-deployment as
a GVariant. During deserialization in _ostree_sysroot_reload_staged(),
_ostree_deployment_set_bootconfig_from_kargs() creates a fresh empty
OstreeBootconfigParser and only populates the "options" key. Any
non-standard BLS keys that were set on the bootconfig by consumers
(such as rpm-ostree) are silently lost.

This matters for the new rpm-ostree kargs --source feature which stores
source ownership metadata as custom keys in the BLS config (e.g.
"ostree-source-tuned"). Without this fix, these keys are dropped during
finalization at shutdown, breaking the source tracking across reboots.

Fix this by following the same pattern used for overlay-initrds:

1. Add _ostree_bootconfig_parser_get_extra_keys_variant() which returns
   all non-standard bootconfig keys as an a{ss} GVariant. Standard keys
   (title, version, options, linux, initrd, devicetree, fdtdir, aboot,
   abootcfg) that install_deployment_kernel() rebuilds from scratch are
   excluded.

2. In ostree_sysroot_stage_tree_with_options(), serialize any extra
   bootconfig keys as "bootconfig-extra" in the staged GVariant dict.

3. In _ostree_sysroot_reload_staged(), restore extra bootconfig keys
   from the "bootconfig-extra" dict onto the deployment's bootconfig.

Backwards compatibility:
- Old ostree versions ignore the unknown "bootconfig-extra" key in the
  a{sv} dict (custom keys silently lost, same as before this patch).
- New ostree gracefully handles the absence of "bootconfig-extra" in
  staged data written by older versions (g_variant_dict_lookup returns
  FALSE, no restoration attempted).

Resolves: RHEL-135363
See: bootc-dev/bootc#899

Assisted-by: OpenCode (Claude Opus 4.6)
Signed-off-by: Joseph Marrero <jmarrero@redhat.com>

Author: jmarrero

src/libostree/ostree-bootconfig-parser-private.h

@@ -8,4 +8,6 @@ G_BEGIN_DECLS
 
 const char *_ostree_bootconfig_parser_filename (OstreeBootconfigParser *self);
 
+GVariant *_ostree_bootconfig_parser_get_extra_keys_variant (OstreeBootconfigParser *self);
+
 G_END_DECLS

src/libostree/ostree-bootconfig-parser.c

@@ -339,6 +339,58 @@ ostree_bootconfig_parser_write (OstreeBootconfigParser *self, GFile *output,
                                             cancellable, error);
 }
 
+/* Keys that are managed by install_deployment_kernel() and should not be
+ * included in the "extra keys" serialization for staged deployments.
+ * These are rebuilt from scratch during finalization.
+ */
+static const char *const standard_bls_keys[]
+    = { "title", "version", "options", "devicetree", "linux", "initrd", "fdtdir", "aboot", "abootcfg", NULL };
+
+static gboolean
+is_standard_bls_key (const char *key)
+{
+  for (const char *const *k = standard_bls_keys; *k != NULL; k++)
+    {
+      if (g_str_equal (key, *k))
+        return TRUE;
+    }
+  return FALSE;
+}
+
+/**
+ * _ostree_bootconfig_parser_get_extra_keys_variant:
+ * @self: Parser
+ *
+ * Returns a GVariant of type "a{ss}" containing all bootconfig keys
+ * that are NOT standard BLS keys (title, version, options, linux, initrd,
+ * devicetree, fdtdir, aboot, abootcfg). These are custom keys set by
+ * consumers like rpm-ostree (e.g. "ostree-source-tuned").
+ *
+ * Returns: (transfer full) (nullable): A new floating GVariant, or NULL if
+ *          there are no extra keys
+ */
+GVariant *
+_ostree_bootconfig_parser_get_extra_keys_variant (OstreeBootconfigParser *self)
+{
+  g_auto (GVariantBuilder) builder = OT_VARIANT_BUILDER_INITIALIZER;
+  gboolean has_entries = FALSE;
+
+  g_variant_builder_init (&builder, (GVariantType *)"a{ss}");
+
+  GLNX_HASH_TABLE_FOREACH_KV (self->options, const char *, k, const char *, v)
+    {
+      if (is_standard_bls_key (k))
+        continue;
+      g_variant_builder_add (&builder, "{ss}", k, v);
+      has_entries = TRUE;
+    }
+
+  if (!has_entries)
+    return NULL;
+
+  return g_variant_builder_end (&builder);
+}
+
 static void
 ostree_bootconfig_parser_finalize (GObject *object)
 {

src/libostree/ostree-sysroot-deploy.c

@@ -3884,6 +3884,20 @@ ostree_sysroot_stage_tree_with_options (OstreeSysroot *self, const char *osname,
     g_variant_builder_add (builder, "{sv}", "overlay-initrds",
                            g_variant_new_strv ((const char *const *)opts->overlay_initrds, -1));
 
+  /* Serialize any non-standard bootconfig keys (e.g. ostree-source-tuned).
+   * These are custom keys set by consumers and need to survive the staging
+   * roundtrip so they are preserved during finalization at shutdown.
+   */
+  {
+    OstreeBootconfigParser *bootconfig = ostree_deployment_get_bootconfig (deployment);
+    if (bootconfig)
+      {
+        GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (bootconfig);
+        if (extra)
+          g_variant_builder_add (builder, "{sv}", "bootconfig-extra", extra);
+      }
+  }
+
   const char *parent = dirname (strdupa (_OSTREE_SYSROOT_RUNSTATE_STAGED));
   if (!glnx_shutil_mkdir_p_at (AT_FDCWD, parent, 0755, cancellable, error))
     return FALSE;

src/libostree/ostree-sysroot.c

@@ -1225,6 +1225,25 @@ _ostree_sysroot_reload_staged (OstreeSysroot *self, GError **error)
 
           _ostree_deployment_set_overlay_initrds (staged, overlay_initrds);
 
+          /* Restore any non-standard bootconfig keys (e.g. ostree-source-tuned)
+           * that were serialized during staging. This preserves custom BLS keys
+           * set by consumers like rpm-ostree through the staging roundtrip.
+           */
+          {
+            g_autoptr (GVariant) bootconfig_extra = NULL;
+            if (g_variant_dict_lookup (staged_deployment_dict, "bootconfig-extra", "@a{ss}",
+                                       &bootconfig_extra))
+              {
+                OstreeBootconfigParser *bootconfig
+                    = ostree_deployment_get_bootconfig (staged);
+                GVariantIter iter;
+                const char *key, *value;
+                g_variant_iter_init (&iter, bootconfig_extra);
+                while (g_variant_iter_next (&iter, "{&s&s}", &key, &value))
+                  ostree_bootconfig_parser_set (bootconfig, key, value);
+              }
+          }
+
           self->staged_deployment = g_steal_pointer (&staged);
           self->staged_deployment_data = g_steal_pointer (&staged_deployment_data);
           /* We set this flag for ostree_deployment_is_staged() because that API

tests/test-bootconfig-parser-internals.c

@@ -49,12 +49,142 @@ test_parse_tries_invalid (void)
   g_assert_cmpuint (done, ==, 0);
 }
 
+static void
+test_extra_keys_variant_empty (void)
+{
+  /* A bootconfig with only standard BLS keys should return NULL */
+  OstreeBootconfigParser *parser = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (parser, "title", "Fedora Linux 40");
+  ostree_bootconfig_parser_set (parser, "version", "1");
+  ostree_bootconfig_parser_set (parser, "options", "root=UUID=abc rw quiet");
+  ostree_bootconfig_parser_set (parser, "linux", "/vmlinuz-6.8.0");
+  ostree_bootconfig_parser_set (parser, "initrd", "/initramfs-6.8.0.img");
+
+  GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (parser);
+  g_assert_null (extra);
+
+  g_object_unref (parser);
+}
+
+static void
+test_extra_keys_variant_with_custom (void)
+{
+  /* A bootconfig with standard + custom keys should return only the custom ones */
+  OstreeBootconfigParser *parser = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (parser, "title", "Fedora Linux 40");
+  ostree_bootconfig_parser_set (parser, "options", "root=UUID=abc rw");
+  ostree_bootconfig_parser_set (parser, "linux", "/vmlinuz-6.8.0");
+  ostree_bootconfig_parser_set (parser, "ostree-source-tuned", "nohz=full isolcpus=1-3");
+  ostree_bootconfig_parser_set (parser, "ostree-source-dracut", "rd.driver.pre=vfio-pci");
+
+  GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (parser);
+  g_assert_nonnull (extra);
+
+  /* Wrap it so it gets freed */
+  GVariant *extra_owned = g_variant_ref_sink (extra);
+
+  /* Should be a{ss} with exactly 2 entries */
+  g_assert_true (g_variant_is_of_type (extra_owned, G_VARIANT_TYPE ("a{ss}")));
+  g_assert_cmpuint (g_variant_n_children (extra_owned), ==, 2);
+
+  /* Verify the contents - iterate and check both keys exist */
+  GVariantIter iter;
+  const char *key, *val;
+  gboolean found_tuned = FALSE, found_dracut = FALSE;
+  g_variant_iter_init (&iter, extra_owned);
+  while (g_variant_iter_next (&iter, "{&s&s}", &key, &val))
+    {
+      if (g_str_equal (key, "ostree-source-tuned"))
+        {
+          g_assert_cmpstr (val, ==, "nohz=full isolcpus=1-3");
+          found_tuned = TRUE;
+        }
+      else if (g_str_equal (key, "ostree-source-dracut"))
+        {
+          g_assert_cmpstr (val, ==, "rd.driver.pre=vfio-pci");
+          found_dracut = TRUE;
+        }
+      else
+        {
+          g_assert_not_reached ();
+        }
+    }
+  g_assert_true (found_tuned);
+  g_assert_true (found_dracut);
+
+  g_variant_unref (extra_owned);
+  g_object_unref (parser);
+}
+
+static void
+test_extra_keys_variant_all_standard (void)
+{
+  /* Test all known standard keys are excluded */
+  OstreeBootconfigParser *parser = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (parser, "title", "Test");
+  ostree_bootconfig_parser_set (parser, "version", "1");
+  ostree_bootconfig_parser_set (parser, "options", "root=UUID=abc");
+  ostree_bootconfig_parser_set (parser, "devicetree", "/dtbs/foo.dtb");
+  ostree_bootconfig_parser_set (parser, "linux", "/vmlinuz");
+  ostree_bootconfig_parser_set (parser, "initrd", "/initramfs.img");
+  ostree_bootconfig_parser_set (parser, "fdtdir", "/dtbs/");
+  ostree_bootconfig_parser_set (parser, "aboot", "/aboot.img");
+  ostree_bootconfig_parser_set (parser, "abootcfg", "/aboot.cfg");
+
+  GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (parser);
+  g_assert_null (extra);
+
+  g_object_unref (parser);
+}
+
+static void
+test_extra_keys_roundtrip (void)
+{
+  /* Test that extra keys can be serialized to a variant and restored */
+  OstreeBootconfigParser *original = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (original, "options", "root=UUID=abc rw");
+  ostree_bootconfig_parser_set (original, "linux", "/vmlinuz");
+  ostree_bootconfig_parser_set (original, "ostree-source-tuned", "nohz=full isolcpus=1-3");
+
+  /* Serialize */
+  GVariant *extra = _ostree_bootconfig_parser_get_extra_keys_variant (original);
+  g_assert_nonnull (extra);
+  GVariant *extra_owned = g_variant_ref_sink (extra);
+
+  /* Create a new parser (simulating deserialization) with only standard keys */
+  OstreeBootconfigParser *restored = ostree_bootconfig_parser_new ();
+  ostree_bootconfig_parser_set (restored, "options", "root=UUID=abc rw nohz=full isolcpus=1-3");
+
+  /* Restore extra keys from variant */
+  GVariantIter iter;
+  const char *key, *value;
+  g_variant_iter_init (&iter, extra_owned);
+  while (g_variant_iter_next (&iter, "{&s&s}", &key, &value))
+    ostree_bootconfig_parser_set (restored, key, value);
+
+  /* Verify the custom key survived the roundtrip */
+  g_assert_cmpstr (ostree_bootconfig_parser_get (restored, "ostree-source-tuned"), ==,
+                   "nohz=full isolcpus=1-3");
+  /* Standard keys should also be present */
+  g_assert_cmpstr (ostree_bootconfig_parser_get (restored, "options"), ==,
+                   "root=UUID=abc rw nohz=full isolcpus=1-3");
+
+  g_variant_unref (extra_owned);
+  g_object_unref (original);
+  g_object_unref (restored);
+}
+
 int
 main (int argc, char *argv[])
 {
   g_test_init (&argc, &argv, NULL);
 
   g_test_add_func ("/bootconfig-parser/tries/valid", test_parse_tries_valid);
   g_test_add_func ("/bootconfig-parser/tries/invalid", test_parse_tries_invalid);
+  g_test_add_func ("/bootconfig-parser/extra-keys/empty", test_extra_keys_variant_empty);
+  g_test_add_func ("/bootconfig-parser/extra-keys/with-custom", test_extra_keys_variant_with_custom);
+  g_test_add_func ("/bootconfig-parser/extra-keys/all-standard",
+                   test_extra_keys_variant_all_standard);
+  g_test_add_func ("/bootconfig-parser/extra-keys/roundtrip", test_extra_keys_roundtrip);
   return g_test_run ();
 }