libostree: Add initial GRUB2 support

In this approach, we drop a /etc/grub.d/15_ostree file which is a
hybrid of shell/C that picks up bits from the GRUB2 library (e.g. the
block device script generation), and then calls into libostree's
GRUB2 code which knows about the BLS entries.

This is admittedly ugly.  There exists another approach for GRUB2 to
learn the BLS specification.  However, the spec has a few issues:

https://www.redhat.com/archives/anaconda-devel-list/2014-July/msg00002.html

This approach also gives a bit more control to the admin via the
naming of the 15_ostree symlink; they can easily disable it:

Or reorder the ostree entries ahead of 10_linux:

Also, this approach doesn't require patches for grub2, which is an
issue with the pressure to backport (rpm-)OSTree to EL7.

src/libostree/ostree-bootloader-grub2.c

@@ -0,0 +1,261 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 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-grub2.h"
+#include "otutil.h"
+#include <gio/gfiledescriptorbased.h>
+#include <gio/gunixoutputstream.h>
+#include "libgsystem.h"
+
+#include <string.h>
+
+struct _OstreeBootloaderGrub2
+{
+  GObject       parent_instance;
+
+  OstreeSysroot  *sysroot;
+  GFile          *config_path_bios;
+};
+
+typedef GObjectClass OstreeBootloaderGrub2Class;
+
+static void _ostree_bootloader_grub2_bootloader_iface_init (OstreeBootloaderInterface *iface);
+G_DEFINE_TYPE_WITH_CODE (OstreeBootloaderGrub2, _ostree_bootloader_grub2, G_TYPE_OBJECT,
+                         G_IMPLEMENT_INTERFACE (OSTREE_TYPE_BOOTLOADER, _ostree_bootloader_grub2_bootloader_iface_init));
+
+static gboolean
+_ostree_bootloader_grub2_query (OstreeBootloader *bootloader)
+{
+  OstreeBootloaderGrub2 *self = OSTREE_BOOTLOADER_GRUB2 (bootloader);
+
+  return g_file_query_exists (self->config_path_bios, NULL);
+}
+
+static const char *
+_ostree_bootloader_grub2_get_name (OstreeBootloader *bootloader)
+{
+  return "grub2";
+}
+
+gboolean
+_ostree_bootloader_grub2_generate_config (OstreeBootloaderGrub2         *self,
+                                          int                            bootversion,
+                                          int                            target_fd,
+                                          GCancellable                  *cancellable,
+                                          GError                       **error)
+{
+  gboolean ret = FALSE;
+  GString *output = g_string_new ("");
+  gs_unref_object GOutputStream *out_stream = NULL;
+  gs_unref_ptrarray GPtrArray *loader_configs = NULL;
+  guint i;
+  gsize bytes_written;
+  /* So... yeah.  Just going to hardcode these. */
+  static const char hardcoded_video[] = "load_video\n"
+    "set gfxpayload=keep\n";
+  static const char hardcoded_insmods[] = "insmod gzio\n";
+  const char *grub2_boot_device_id =
+    g_getenv ("GRUB2_BOOT_DEVICE_ID");
+  const char *grub2_prepare_root_cache =
+    g_getenv ("GRUB2_PREPARE_ROOT_CACHE");
+
+  /* We must have been called via the wrapper script */
+  g_assert (grub2_boot_device_id != NULL);
+  g_assert (grub2_prepare_root_cache != NULL);
+
+  out_stream = g_unix_output_stream_new (target_fd, FALSE);
+
+  if (!_ostree_sysroot_read_boot_loader_configs (self->sysroot, bootversion,
+                                                 &loader_configs,
+                                                 cancellable, error))
+    goto out;
+
+  for (i = 0; i < loader_configs->len; i++)
+    {
+      OstreeBootconfigParser *config = loader_configs->pdata[i];
+      const char *title;
+      const char *options;
+      const char *kernel;
+      const char *initrd;
+      char *quoted_title = NULL;
+      char *uuid = NULL;
+      char *quoted_uuid = NULL;
+
+      title = ostree_bootconfig_parser_get (config, "title");
+      if (!title)
+        title = "(Untitled)";
+
+      kernel = ostree_bootconfig_parser_get (config, "linux");
+
+      quoted_title = g_shell_quote (title);
+      uuid = g_strdup_printf ("ostree-%u-%s", (guint)i, grub2_boot_device_id);
+      quoted_uuid = g_shell_quote (uuid);
+      g_string_append_printf (output, "menuentry %s --class gnu-linux --class gnu --class os --unrestricted %s {\n", quoted_title, quoted_uuid);
+      g_free (uuid);
+      g_free (quoted_title);
+      g_free (quoted_uuid);
+
+      /* Hardcoded sections */
+      g_string_append (output, hardcoded_video);
+      g_string_append (output, hardcoded_insmods);
+      g_string_append (output, grub2_prepare_root_cache);
+      g_string_append_c (output, '\n');
+      
+      if (!kernel)
+        {
+          g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                       "No \"linux\" key in bootloader config");
+          goto out;
+        }
+      g_string_append (output, "linux16 ");
+      g_string_append (output, kernel);
+
+      options = ostree_bootconfig_parser_get (config, "options");
+      if (options)
+        {
+          g_string_append_c (output, ' ');
+          g_string_append (output, options);
+        }
+      g_string_append_c (output, '\n');
+
+      initrd = ostree_bootconfig_parser_get (config, "initrd");
+      if (initrd)
+        {
+          g_string_append (output, "initrd16 ");
+          g_string_append (output, initrd);
+          g_string_append_c (output, '\n');
+        }
+
+      g_string_append (output, "}\n");
+    }
+
+  if (!g_output_stream_write_all (out_stream, output->str, output->len,
+                                  &bytes_written, cancellable, error))
+    goto out;
+
+  ret = TRUE;
+ out:
+  if (output)
+    g_string_free (output, TRUE);
+  return ret;
+}
+
+static gboolean
+_ostree_bootloader_grub2_write_config (OstreeBootloader      *bootloader,
+                                       int                    bootversion,
+                                       GCancellable          *cancellable,
+                                       GError               **error)
+{
+  OstreeBootloaderGrub2 *self = OSTREE_BOOTLOADER_GRUB2 (bootloader);
+  gboolean ret = FALSE;
+  gs_unref_object GFile *new_config_path = NULL;
+  gs_unref_object GSSubprocessContext *procctx = NULL;
+  gs_unref_object GSSubprocess *proc = NULL;
+  gs_strfreev char **child_env = g_get_environ ();
+  gs_free char *bootversion_str = g_strdup_printf ("%u", (guint)bootversion);
+
+  new_config_path = ot_gfile_resolve_path_printf (self->sysroot->path, "boot/loader.%d/grub.cfg",
+                                                  bootversion);
+
+  procctx = gs_subprocess_context_newv ("grub2-mkconfig", "-o",
+                                        gs_file_get_path_cached (new_config_path),
+                                        NULL);
+  child_env = g_environ_setenv (child_env, "_OSTREE_GRUB2_BOOTVERSION", bootversion_str, TRUE);
+  gs_subprocess_context_set_environment (procctx, child_env);
+  gs_subprocess_context_set_stdout_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_NULL);
+  if (g_getenv ("OSTREE_DEBUG_GRUB2"))
+    gs_subprocess_context_set_stderr_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_INHERIT);
+  else
+    gs_subprocess_context_set_stderr_disposition (procctx, GS_SUBPROCESS_STREAM_DISPOSITION_NULL);
+
+  /* In the current Fedora grub2 package, this script doesn't even try
+     to be atomic; it just does:
+
+cat ${grub_cfg}.new > ${grub_cfg}
+rm -f ${grub_cfg}.new
+
+     Upstream is fixed though.
+  */
+  proc = gs_subprocess_new (procctx, cancellable, error);
+  if (!proc)
+    goto out;
+
+  if (!gs_subprocess_wait_sync_check (proc, cancellable, error))
+    goto out;
+
+  /* Now let's fdatasync() for the new file */
+  if (!gs_file_sync_data (new_config_path, cancellable, error))
+    goto out;
+  
+  ret = TRUE;
+ out:
+  return ret;
+}
+
+static gboolean
+_ostree_bootloader_grub2_is_atomic (OstreeBootloader      *bootloader) 
+{
+  return TRUE;
+}
+
+static void
+_ostree_bootloader_grub2_finalize (GObject *object)
+{
+  OstreeBootloaderGrub2 *self = OSTREE_BOOTLOADER_GRUB2 (object);
+
+  g_clear_object (&self->sysroot);
+  g_clear_object (&self->config_path_bios);
+
+  G_OBJECT_CLASS (_ostree_bootloader_grub2_parent_class)->finalize (object);
+}
+
+void
+_ostree_bootloader_grub2_init (OstreeBootloaderGrub2 *self)
+{
+}
+
+static void
+_ostree_bootloader_grub2_bootloader_iface_init (OstreeBootloaderInterface *iface)
+{
+  iface->query = _ostree_bootloader_grub2_query;
+  iface->get_name = _ostree_bootloader_grub2_get_name;
+  iface->write_config = _ostree_bootloader_grub2_write_config;
+  iface->is_atomic = _ostree_bootloader_grub2_is_atomic;
+}
+
+void
+_ostree_bootloader_grub2_class_init (OstreeBootloaderGrub2Class *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->finalize = _ostree_bootloader_grub2_finalize;
+}
+
+OstreeBootloaderGrub2 *
+_ostree_bootloader_grub2_new (OstreeSysroot *sysroot)
+{
+  OstreeBootloaderGrub2 *self = g_object_new (OSTREE_TYPE_BOOTLOADER_GRUB2, NULL);
+  self->sysroot = g_object_ref (sysroot);
+  self->config_path_bios = g_file_resolve_relative_path (self->sysroot->path, "boot/grub2/grub.cfg");
+  return self;
+}

src/libostree/ostree-bootloader-grub2.h

@@ -0,0 +1,40 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 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.
+ */
+
+#pragma once
+
+#include "ostree-bootloader.h"
+
+G_BEGIN_DECLS
+
+#define OSTREE_TYPE_BOOTLOADER_GRUB2 (_ostree_bootloader_grub2_get_type ())
+#define OSTREE_BOOTLOADER_GRUB2(inst) (G_TYPE_CHECK_INSTANCE_CAST ((inst), OSTREE_TYPE_BOOTLOADER_GRUB2, OstreeBootloaderGrub2))
+#define OSTREE_IS_BOOTLOADER_GRUB2(inst) (G_TYPE_CHECK_INSTANCE_TYPE ((inst), OSTREE_TYPE_BOOTLOADER_GRUB2))
+
+typedef struct _OstreeBootloaderGrub2 OstreeBootloaderGrub2;
+
+GType _ostree_bootloader_grub2_get_type (void) G_GNUC_CONST;
+
+OstreeBootloaderGrub2 * _ostree_bootloader_grub2_new (OstreeSysroot *sysroot);
+
+gboolean _ostree_bootloader_grub2_generate_config (OstreeBootloaderGrub2 *self, int bootversion, int target_fd, GCancellable *cancellable, GError **error);
+
+G_END_DECLS
+

src/libostree/ostree-bootloader.c

@@ -61,3 +61,14 @@ _ostree_bootloader_write_config (OstreeBootloader  *self,
   return OSTREE_BOOTLOADER_GET_IFACE (self)->write_config (self, bootversion, 
                                                        cancellable, error);
 }
+
+gboolean
+_ostree_bootloader_is_atomic (OstreeBootloader  *self)
+{
+  g_return_val_if_fail (OSTREE_IS_BOOTLOADER (self), FALSE);
+
+  if (OSTREE_BOOTLOADER_GET_IFACE (self)->is_atomic)
+    return OSTREE_BOOTLOADER_GET_IFACE (self)->is_atomic (self);
+  else
+    return TRUE;
+}

src/libostree/ostree-bootloader.h

@@ -43,6 +43,7 @@ struct _OstreeBootloaderInterface
                                                    int            bootversion,
                                                    GCancellable  *cancellable,
                                                    GError       **error);
+  gboolean             (* is_atomic)              (OstreeBootloader  *self);
 };
 
 GType _ostree_bootloader_get_type (void) G_GNUC_CONST;
@@ -56,5 +57,7 @@ gboolean _ostree_bootloader_write_config (OstreeBootloader  *self,
                                           GCancellable  *cancellable,
                                           GError       **error);
 
+gboolean _ostree_bootloader_is_atomic (OstreeBootloader  *self);
+
 G_END_DECLS
 

src/libostree/ostree-cmdprivate.c

@@ -0,0 +1,52 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>
+ *
+ * This library 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 License, 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-cmdprivate.h"
+#include "ostree-sysroot.h"
+#include "ostree-bootloader-grub2.h"
+
+#include "otutil.h"
+
+static gboolean 
+impl_ostree_generate_grub2_config (OstreeSysroot *sysroot, int bootversion, int target_fd, GCancellable *cancellable, GError **error)
+{
+  gs_unref_object OstreeBootloaderGrub2 *grub2 = _ostree_bootloader_grub2_new (sysroot);
+
+  return _ostree_bootloader_grub2_generate_config (grub2, bootversion, target_fd, cancellable, error);
+}
+
+/**
+ * ostree_cmdprivate: (skip)
+ *
+ * Do not call this function; it is used to share private API between
+ * the OSTree commandline and the library.
+ */
+OstreeCmdPrivateVTable *
+ostree_cmd__private__ (void)
+{
+  static OstreeCmdPrivateVTable table = {
+    impl_ostree_generate_grub2_config
+  };
+
+  return &table;
+}
+

src/libostree/ostree-cmdprivate.h

@@ -0,0 +1,35 @@
+/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*-
+ *
+ * Copyright (C) 2014 Colin Walters <walters@verbum.org>
+ *
+ * This library 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 License, 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.
+ */
+
+#pragma once
+
+#include "ostree-types.h"
+
+G_BEGIN_DECLS
+
+typedef struct {
+  gboolean (* ostree_generate_grub2_config) (OstreeSysroot *sysroot, int bootversion, int target_fd, GCancellable *cancellable, GError **error);
+} OstreeCmdPrivateVTable;
+
+OstreeCmdPrivateVTable *
+ostree_cmd__private__ (void);
+
+G_END_DECLS
+

src/libostree/ostree-sysroot-deploy.c

@@ -1004,6 +1004,8 @@ get_kernel_from_tree (GFile         *deployroot,
                       GError       **error)
 {
   gboolean ret = FALSE;
+  gs_unref_object GFile *ostree_bootdir
+    = g_file_resolve_relative_path (deployroot, "usr/lib/ostree-boot");
   gs_unref_object GFile *bootdir = g_file_get_child (deployroot, "boot");
   gs_unref_object GFileEnumerator *dir_enum = NULL;
   gs_unref_object GFile *ret_kernel = NULL;
@@ -1011,11 +1013,22 @@ get_kernel_from_tree (GFile         *deployroot,
   gs_free char *kernel_checksum = NULL;
   gs_free char *initramfs_checksum = NULL;
 
-  dir_enum = g_file_enumerate_children (bootdir, OSTREE_GIO_FAST_QUERYINFO,
-                                        G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
-                                        NULL, error);
-  if (!dir_enum)
-    goto out;
+  if (g_file_query_exists (ostree_bootdir, NULL))
+    {
+      dir_enum = g_file_enumerate_children (ostree_bootdir, OSTREE_GIO_FAST_QUERYINFO,
+                                            G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
+                                            NULL, error);
+      if (!dir_enum)
+        goto out;
+    }
+  else
+    {
+      dir_enum = g_file_enumerate_children (bootdir, OSTREE_GIO_FAST_QUERYINFO,
+                                            G_FILE_QUERY_INFO_NOFOLLOW_SYMLINKS,
+                                            NULL, error);
+      if (!dir_enum)
+        goto out;
+    }
 
   while (TRUE)
     {
@@ -1510,6 +1523,7 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
   guint i;
   gboolean requires_new_bootversion = FALSE;
   gboolean found_booted_deployment = FALSE;
+  gboolean bootloader_is_atomic = FALSE;
 
   g_assert (self->loaded);
 
@@ -1578,6 +1592,8 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
           g_prefix_error (error, "Swapping current bootlinks: ");
           goto out;
         }
+      
+      bootloader_is_atomic = TRUE;
     }
   else
     {
@@ -1615,11 +1631,17 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
       g_debug ("Using bootloader: %s", bootloader ?
                g_type_name (G_TYPE_FROM_INSTANCE (bootloader)) : "(none)");
 
-      if (bootloader && !_ostree_bootloader_write_config (bootloader, new_bootversion,
-                                                          cancellable, error))
+      if (bootloader)
+        bootloader_is_atomic = _ostree_bootloader_is_atomic (bootloader);
+
+      if (bootloader)
         {
-          g_prefix_error (error, "Bootloader write config: ");
-          goto out;
+          if (!_ostree_bootloader_write_config (bootloader, new_bootversion,
+                                                cancellable, error))
+            {
+              g_prefix_error (error, "Bootloader write config: ");
+              goto out;
+            }
         }
 
       if (!full_system_sync (cancellable, error))
@@ -1627,7 +1649,7 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
           g_prefix_error (error, "Full sync: ");
           goto out;
         }
-
+      
       if (!swap_bootloader (self, self->bootversion, new_bootversion,
                             cancellable, error))
         {
@@ -1637,7 +1659,8 @@ ostree_sysroot_write_deployments (OstreeSysroot     *self,
     }
 
   gs_log_structured_print_id_v (OSTREE_DEPLOYMENT_COMPLETE_ID,
-                                "Transaction complete; bootconfig swap: %s deployment count change: %i)",
+                                "%s; bootconfig swap: %s deployment count change: %i",
+                                (bootloader_is_atomic ? "Transaction complete" : "Bootloader updated"),
                                 requires_new_bootversion ? "yes" : "no",
                                 new_deployments->len - self->deployments->len);
 

src/libostree/ostree-sysroot.c

@@ -26,6 +26,7 @@
 #include "ostree-sysroot-private.h"
 #include "ostree-bootloader-uboot.h"
 #include "ostree-bootloader-syslinux.h"
+#include "ostree-bootloader-grub2.h"
 
 static gboolean
 find_booted_deployment (OstreeSysroot       *self,
@@ -853,11 +854,16 @@ _ostree_sysroot_query_bootloader (OstreeSysroot *self)
 {
   OstreeBootloaderSyslinux *syslinux;
   OstreeBootloaderUboot    *uboot;
+  OstreeBootloaderGrub2    *grub2;
 
   syslinux = _ostree_bootloader_syslinux_new (self);
   if (_ostree_bootloader_query ((OstreeBootloader*)syslinux))
     return (OstreeBootloader*) (syslinux);
 
+  grub2 = _ostree_bootloader_grub2_new (self);
+  if (_ostree_bootloader_query ((OstreeBootloader*)grub2))
+    return (OstreeBootloader*) (grub2);
+
   uboot = _ostree_bootloader_uboot_new (self);
   if (_ostree_bootloader_query ((OstreeBootloader*)uboot))
     return (OstreeBootloader*) (uboot);