prepare-root: add kernel cmdline ostree.prepare-root.readonly

man/ostree-prepare-root.xml

@@ -163,6 +163,11 @@ License along with this library. If not, see <https://www.gnu.org/licenses/>.
                 <listitem><para>This accepts the same values as <literal>composefs.enabled</literal> above, and overrides the config file (if present).
                     For example, specifying <literal>ostree.prepare-root.composefs=0</literal> will disable composefs, even if it is enabled by default in the initrd config.</para></listitem>
             </varlistentry>
+            <varlistentry>
+                <term><varname>ostree.prepare-root.readonly</varname></term>
+                <listitem><para>This accepts the same values as <literal>sysroot.readonly</literal> above, and overrides the config file (if present).
+                    For example, specifying <literal>ostree.prepare-root.readonly=0</literal> will disable mounting /sysroot read-only, even if it is enabled by default in the initrd config.</para></listitem>
+            </varlistentry>
         </variablelist>
 
     </refsect1>

src/libotcore/otcore-prepare-root.c

@@ -26,6 +26,8 @@
 #define BINDING_KEYPATH "/etc/ostree/initramfs-root-binding.key"
 // The kernel argument to configure composefs
 #define CMDLINE_KEY_COMPOSEFS "ostree.prepare-root.composefs"
+// The kernel argument to configure sysroot.readonly
+#define CMDLINE_KEY_READONLY "ostree.prepare-root.readonly"
 
 static bool
 proc_cmdline_has_key_starting_with (const char *cmdline, const char *key)
@@ -239,3 +241,36 @@ otcore_load_composefs_config (const char *cmdline, GKeyFile *config, gboolean lo
 
   return g_steal_pointer (&ret);
 }
+
+gboolean
+otcore_load_sysroot_readonly (const char *cmdline, GKeyFile *config,
+                              const ComposefsConfig *composefs_config,
+                              gboolean *sysroot_readonly, GError **error)
+{
+  g_assert (cmdline);
+  g_assert (config);
+  g_assert (composefs_config);
+  g_assert (sysroot_readonly);
+
+  GLNX_AUTO_PREFIX_ERROR ("Loading sysroot readonly config", error);
+
+  g_autofree char *readonly_cmdline =
+    otcore_find_proc_cmdline_key (cmdline, CMDLINE_KEY_READONLY);
+  if (readonly_cmdline)
+    {
+      if (!_ostree_parse_boolean(readonly_cmdline, sysroot_readonly, error))
+        return glnx_prefix_error (error, "handling karg" CMDLINE_KEY_READONLY);
+
+      return TRUE;
+    }
+
+  // If composefs is enabled, that also implies sysroot.readonly=true because it's
+  // the new default we want to use (not because it's actually required)
+  const gboolean sysroot_readonly_default = composefs_config->enabled == OT_TRISTATE_YES;
+  if (!ot_keyfile_get_boolean_with_default (config, OTCORE_PREPARE_ROOT_SYSROOT_KEY,
+                                            OTCORE_PREPARE_ROOT_READONLY_KEY,
+                                            sysroot_readonly_default, sysroot_readonly, error))
+    return FALSE;
+
+  return TRUE;
+}

src/libotcore/otcore.h

@@ -61,6 +61,9 @@ G_DEFINE_AUTOPTR_CLEANUP_FUNC (ComposefsConfig, otcore_free_composefs_config)
 
 ComposefsConfig *otcore_load_composefs_config (const char *cmdline, GKeyFile *config,
                                                gboolean load_keys, GError **error);
+gboolean otcore_load_sysroot_readonly (const char *cmdline, GKeyFile *config,
+                                       const ComposefsConfig *composefs_config,
+                                       gboolean *sysroot_readonly, GError **error);
 
 // Our directory with transient state (eventually /run/ostree-booted should be a link to
 // /run/ostree/booted)
@@ -86,6 +89,9 @@ ComposefsConfig *otcore_load_composefs_config (const char *cmdline, GKeyFile *co
 // EROFS mount if we somehow leaked it (but it *should* be unmounted always).
 #define OSTREE_COMPOSEFS_LOWERMNT OTCORE_RUN_OSTREE_PRIVATE "/cfsroot-lower"
 
+#define OTCORE_PREPARE_ROOT_SYSROOT_KEY "sysroot"
+#define OTCORE_PREPARE_ROOT_READONLY_KEY "readonly"
+
 #define OTCORE_PREPARE_ROOT_COMPOSEFS_KEY "composefs"
 #define OTCORE_PREPARE_ROOT_ENABLED_KEY "enabled"
 #define OTCORE_PREPARE_ROOT_KEYPATH_KEY "keypath"

src/switchroot/ostree-prepare-root.c

@@ -76,9 +76,6 @@
 #include "ot-keyfile-utils.h"
 #include "otcore.h"
 
-#define SYSROOT_KEY "sysroot"
-#define READONLY_KEY "readonly"
-
 /* This key configures the / mount in the deployment root */
 #define ROOT_KEY "root"
 #define ETC_KEY "etc"
@@ -109,7 +106,8 @@ sysroot_is_configured_ro (const char *sysroot)
       return false;
     }
 
-  return g_key_file_get_boolean (repo_config, SYSROOT_KEY, READONLY_KEY, NULL);
+  return g_key_file_get_boolean (repo_config, OTCORE_PREPARE_ROOT_SYSROOT_KEY,
+                                 OTCORE_PREPARE_ROOT_READONLY_KEY, NULL);
 }
 
 static char *
@@ -280,7 +278,6 @@ main (int argc, char *argv[])
   if (!config)
     errx (EXIT_FAILURE, "Failed to parse config: %s", error->message);
 
-  gboolean sysroot_readonly = FALSE;
   gboolean root_transient = FALSE;
 
   if (!ot_keyfile_get_boolean_with_default (config, ROOT_KEY, TRANSIENT_KEY, FALSE, &root_transient,
@@ -294,12 +291,10 @@ main (int argc, char *argv[])
   if (!composefs_config)
     errx (EXIT_FAILURE, "%s", error->message);
 
-  // If composefs is enabled, that also implies sysroot.readonly=true because it's
-  // the new default we want to use (not because it's actually required)
-  const bool sysroot_readonly_default = composefs_config->enabled == OT_TRISTATE_YES;
-  if (!ot_keyfile_get_boolean_with_default (config, SYSROOT_KEY, READONLY_KEY,
-                                            sysroot_readonly_default, &sysroot_readonly, &error))
-    errx (EXIT_FAILURE, "Failed to parse sysroot.readonly value: %s", error->message);
+  gboolean sysroot_readonly;
+  if (!otcore_load_sysroot_readonly (kernel_cmdline, config, composefs_config, &sysroot_readonly,
+                                     &error))
+    errx (EXIT_FAILURE, "%s", error->message);
 
   /* This is the final target where we should prepare the rootfs.  The usual
    * case with systemd in the initramfs is that root_mountpoint = "/sysroot".