bootloader: Add a zipl bootloader backend

zipl is a bit special in that it parses the BLS config files
directly *but* we need to run the command to update the "boot block".

Hence, we're not generating a separate config file like the other
backends.  Instead, extend the bootloader interface with a `post_bls_sync`
method that is run in the same place we swap the `boot/loader` symlink.

We write a "stamp file" in `/boot` that says we need to run this command.
The reason we use stamp file is to prevent the case where the system is
interrupted after BLS file is updated, but before zipl is triggered,
then zipl boot records are not updated.
This opens the door to making things eventually-consistent/reconcilable
by later adding a systemd unit to run `zipl` if we're interrupted via
a systemd unit - I think we should eventually take this approach
everywhere rather than requiring `/boot/loader` to be a symlink.

Author: Colin Walters <walters@verbum.org>
Tested-by: Tuan Hoang <tmhoang@linux.ibm.com>
Co-Authored-By: Tuan Hoang <tmhoang@linux.ibm.com>

1 files changed, 152 insertions, 0 deletions

diff --git a/src/libostree/ostree-bootloader-zipl.c b/src/libostree/ostree-bootloader-zipl.c
new file mode 100644
index 00000000..4ac785d9
--- /dev/null
+++ b/src/libostree/ostree-bootloader-zipl.c
@@ -0,0 +1,152 @@
+/*
+ * Copyright (C) 2019 Colin Walters <walters@verbum.org>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; either version 2 of the licence or (at
+ * your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General
+ * Public License along with this library; if not, write to the
+ * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
+ * Boston, MA 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "ostree-sysroot-private.h"
+#include "ostree-bootloader-zipl.h"
+#include "otutil.h"
+
+#include <string.h>
+
+/* This is specific to zipl today, but in the future we could also
+ * use it for the grub2-mkconfig case.
+ */
+static const char zipl_requires_execute_path[] = "boot/ostree-bootloader-update.stamp";
+
+struct _OstreeBootloaderZipl
+{
+  GObject       parent_instance;
+
+  OstreeSysroot  *sysroot;
+};
+
+typedef GObjectClass OstreeBootloaderZiplClass;
+
+static void _ostree_bootloader_zipl_bootloader_iface_init (OstreeBootloaderInterface *iface);
+G_DEFINE_TYPE_WITH_CODE (OstreeBootloaderZipl, _ostree_bootloader_zipl, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (OSTREE_TYPE_BOOTLOADER, _ostree_bootloader_zipl_bootloader_iface_init));
+
+static gboolean
+_ostree_bootloader_zipl_query (OstreeBootloader *bootloader,
+                                   gboolean         *out_is_active,
+                                   GCancellable     *cancellable,
+                                   GError          **error)
+{
+  /* We don't auto-detect this one; should be explicitly chosen right now.
+   * see also https://github.com/coreos/coreos-assembler/pull/849
+   */
+  *out_is_active = FALSE;
+  return TRUE;
+}
+
+static const char *
+_ostree_bootloader_zipl_get_name (OstreeBootloader *bootloader)
+{
+  return "zipl";
+}
+
+static gboolean
+_ostree_bootloader_zipl_write_config (OstreeBootloader  *bootloader,
+                                          int                bootversion,
+                                          GPtrArray         *new_deployments,
+                                          GCancellable      *cancellable,
+                                          GError           **error)
+{
+  OstreeBootloaderZipl *self = OSTREE_BOOTLOADER_ZIPL (bootloader);
+
+  /* Write our stamp file */
+  if (!glnx_file_replace_contents_at (self->sysroot->sysroot_fd, zipl_requires_execute_path,
+                                      (guint8*)"", 0, GLNX_FILE_REPLACE_NODATASYNC,
+                                      cancellable, error))
+    return FALSE;
+
+  return TRUE;
+}
+
+static gboolean
+_ostree_bootloader_zipl_post_bls_sync (OstreeBootloader  *bootloader,
+                                       GCancellable  *cancellable,
+                                       GError       **error)
+{
+  OstreeBootloaderZipl *self = OSTREE_BOOTLOADER_ZIPL (bootloader);
+
+  /* Note that unlike the grub2-mkconfig backend, we make no attempt to
+   * chroot().
+   */
+  g_assert (self->sysroot->booted_deployment);
+
+  if (!glnx_fstatat_allow_noent (self->sysroot->sysroot_fd, zipl_requires_execute_path, NULL, 0, error))
+    return FALSE;
+
+  /* If there's no stamp file, nothing to do */
+  if (errno == ENOENT)
+    return TRUE;
+
+  const char *const zipl_argv[] = {"zipl", NULL};
+  int estatus;
+  if (!g_spawn_sync (NULL, (char**)zipl_argv, NULL, G_SPAWN_SEARCH_PATH,
+                     NULL, NULL, NULL, NULL, &estatus, error))
+    return FALSE;
+  if (!g_spawn_check_exit_status (estatus, error))
+    return FALSE;
+  if (!glnx_unlinkat (self->sysroot->sysroot_fd, zipl_requires_execute_path, 0, error))
+    return FALSE;
+  return TRUE;
+}
+
+static void
+_ostree_bootloader_zipl_finalize (GObject *object)
+{
+  OstreeBootloaderZipl *self = OSTREE_BOOTLOADER_ZIPL (object);
+
+  g_clear_object (&self->sysroot);
+
+  G_OBJECT_CLASS (_ostree_bootloader_zipl_parent_class)->finalize (object);
+}
+
+void
+_ostree_bootloader_zipl_init (OstreeBootloaderZipl *self)
+{
+}
+
+static void
+_ostree_bootloader_zipl_bootloader_iface_init (OstreeBootloaderInterface *iface)
+{
+  iface->query = _ostree_bootloader_zipl_query;
+  iface->get_name = _ostree_bootloader_zipl_get_name;
+  iface->write_config = _ostree_bootloader_zipl_write_config;
+  iface->post_bls_sync = _ostree_bootloader_zipl_post_bls_sync;
+}
+
+void
+_ostree_bootloader_zipl_class_init (OstreeBootloaderZiplClass *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->finalize = _ostree_bootloader_zipl_finalize;
+}
+
+OstreeBootloaderZipl *
+_ostree_bootloader_zipl_new (OstreeSysroot *sysroot)
+{
+  OstreeBootloaderZipl *self = g_object_new (OSTREE_TYPE_BOOTLOADER_ZIPL, NULL);
+  self->sysroot = g_object_ref (sysroot);
+  return self;
+}