sysroot: Support boot counting for boot entries

Add support for boot counting for bootloader entries [1].
The boot counting data is stored in the name of the boot loader entry.
A boot loader entry file name may contain a plus (+) followed by a number.
This may optionally be followed by a minus (-) followed by a second number.
The dot (.) and file name suffix (conf or efi) must immediately follow.

The feature is enabled via sysroot configuration:
[sysroot]
boot-counting-tries=3

Testing:
$ ostree admin deploy 91fc19319be9e79d07159303dff125f40f10e5c25614630dcbed23d95e36f907
Copying /etc changes: 2 modified, 3 removed, 4 added
bootfs is sufficient for calculated new size: 0 bytes
Transaction complete; bootconfig swap: yes; bootversion: boot.0.1, deployment count change: 1

$ ls /boot/loader/entries
ostree-1.conf  ostree-2+3.conf

[1] https://uapi-group.org/specifications/specs/boot_loader_specification/#boot-counting
Signed-off-by: Igor Opaniuk <igor.opaniuk@foundries.io>

Author: igoropaniuk

man/ostree.repo-config.xml

@@ -416,6 +416,18 @@ License along with this library. If not, see <https://www.gnu.org/licenses/>.
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term><varname>boot-counting-tries</varname></term>
+        <listitem><para>Integer value controlling the number of maximum boot attempts. The boot
+        counting data is stored in the name of the boot loader entry. A boot loader entry file name
+        may contain a plus (+) followed by a number. This may optionally be followed by
+        a minus (-) followed by a second number. The dot (.) and file name suffix (conf or efi) must
+        immediately follow. More details in the
+        <ulink url="https://uapi-group.org/specifications/specs/boot_loader_specification/#boot-counting">
+        The Boot Loader Specification</ulink>
+        </para></listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><varname>bls-append-except-default</varname></term>
         <listitem><para>A semicolon separated string list of key-value pairs. For example:

src/libostree/ostree-bootconfig-parser.c

@@ -27,6 +27,9 @@ struct _OstreeBootconfigParser
   gboolean parsed;
   const char *separators;
 
+  guint64 tries_left;
+  guint64 tries_done;
+
   GHashTable *options;
 
   /* Additional initrds; the primary initrd is in options. */
@@ -56,6 +59,94 @@ ostree_bootconfig_parser_clone (OstreeBootconfigParser *self)
   return parser;
 }
 
+/**
+ * ostree_bootconfig_parser_parse_tries:
+ * @self: Parser
+ * @path: File path
+ *
+ * Parses a suffix of two counters in the form "+LEFT-DONE" from the end of the
+ * filename (excluding file extension).
+ */
+static void
+ostree_bootconfig_parser_parse_tries (OstreeBootconfigParser *self,  const char *filename)
+{
+  gchar *counter = NULL;
+  gchar *old_counter = NULL;
+  self->tries_left = 0;
+  self->tries_done = 0;
+
+  for (;;)
+    {
+      char *plus = strchr (counter ?: filename, '+');
+      if (plus)
+        {
+          /* Look for the last "+" symbol in the filename */
+          counter = plus + 1;
+          continue;
+        }
+      if (counter)
+        break;
+
+      /* No boot counter found */
+      return;
+    }
+
+  guint64 tries_left, tries_done = 0;
+
+  old_counter = counter;
+  tries_left = g_ascii_strtoull (old_counter, &counter, 10);
+  if ((old_counter == counter) || (tries_left > INT_MAX))
+    return;
+
+  /* Parse done counter only if present */
+  if (*counter == '-')
+    {
+      old_counter = counter;
+      tries_done = g_ascii_strtoull (counter + 1, &counter, 10);
+      if ((old_counter == counter) || (tries_left > INT_MAX))
+        return;
+    }
+
+  self->tries_left = tries_left;
+  self->tries_done = tries_done;
+}
+
+/**
+ * ostree_bootconfig_parser_get_tries_left:
+ * @self: Parser
+ *
+ * Returns: Amount of boot tries left
+ */
+guint64
+ostree_bootconfig_parser_get_tries_left (OstreeBootconfigParser *self)
+{
+  return self->tries_left;
+}
+
+/**
+ * ostree_bootconfig_parser_get_tries_done:
+ * @self: Parser
+ *
+ * Returns: Amount of boot tries
+ */
+guint64
+ostree_bootconfig_parser_get_tries_done (OstreeBootconfigParser *self)
+{
+  return self->tries_done;
+}
+
+/**
+ * ostree_bootconfig_parser_get_tries_done:
+ * @self: Parser
+ *
+ * Returns: TRUE if the boot config was parsed from existing boot config file
+ */
+gboolean
+ostree_bootconfig_parser_is_parsed (OstreeBootconfigParser *self)
+{
+  return self->parsed;
+}
+
 /**
  * ostree_bootconfig_parser_parse_at:
  * @self: Parser
@@ -116,6 +207,8 @@ ostree_bootconfig_parser_parse_at (OstreeBootconfigParser *self, int dfd, const
       self->overlay_initrds = (char **)g_ptr_array_free (g_steal_pointer (&overlay_initrds), FALSE);
     }
 
+  ostree_bootconfig_parser_parse_tries(self, glnx_basename(path));
+
   self->parsed = TRUE;
 
   return TRUE;

src/libostree/ostree-bootconfig-parser.h

@@ -67,4 +67,13 @@ void ostree_bootconfig_parser_set_overlay_initrds (OstreeBootconfigParser *self,
 _OSTREE_PUBLIC
 char **ostree_bootconfig_parser_get_overlay_initrds (OstreeBootconfigParser *self);
 
+_OSTREE_PUBLIC
+guint64 ostree_bootconfig_parser_get_tries_left (OstreeBootconfigParser *self);
+
+_OSTREE_PUBLIC
+guint64 ostree_bootconfig_parser_get_tries_done (OstreeBootconfigParser *self);
+
+_OSTREE_PUBLIC
+gboolean ostree_bootconfig_parser_is_parsed (OstreeBootconfigParser *self);
+
 G_END_DECLS

src/libostree/ostree-repo-private.h

@@ -247,6 +247,7 @@ struct OstreeRepo
   GHashTable
       *bls_append_values;     /* Parsed key-values from bls-append-except-default key in config. */
   gboolean enable_bootprefix; /* If true, prepend bootloader entries with /boot */
+  guint boot_counting;
 
   OstreeRepo *parent_repo;
 };

src/libostree/ostree-repo.c

@@ -3297,6 +3297,20 @@ reload_remote_config (OstreeRepo *self, GCancellable *cancellable, GError **erro
 static gboolean
 reload_sysroot_config (OstreeRepo *self, GCancellable *cancellable, GError **error)
 {
+  {
+    g_autofree char *boot_counting_str = NULL;
+
+    (void)ot_keyfile_get_value_with_default_group_optional (self->config, "sysroot", "boot-counting-tries", "0",
+                                                            &boot_counting_str, NULL);
+
+    if (boot_counting_str)
+      /* Ensure boot count value is in [0,5] */
+      self->boot_counting
+          = MAX (0, MIN (INT_MAX, g_ascii_strtoull (boot_counting_str, NULL, 10)));
+    else
+      self->boot_counting = 0;
+  }
+
   g_autofree char *bootloader = NULL;
 
   if (!ot_keyfile_get_value_with_default_group_optional (self->config, "sysroot", "bootloader",

src/libostree/ostree-sysroot-deploy.c

@@ -1801,13 +1801,13 @@ parse_os_release (const char *contents, const char *split)
   return ret;
 }
 
-/* Generate the filename we will use in /boot/loader/entries for this deployment.
+/* Generate the entry name we will use in /boot/loader/entries for this deployment.
  * The provided n_deployments should be the total number of target deployments (which
  * might be different from the cached value in the sysroot).
  */
 static char *
-bootloader_entry_filename (OstreeSysroot *sysroot, guint n_deployments,
-                           OstreeDeployment *deployment)
+bootloader_entry_name (OstreeSysroot *sysroot, guint n_deployments,
+                       OstreeDeployment *deployment)
 {
   guint index = n_deployments - ostree_deployment_get_index (deployment);
   // Allow opt-out to dropping the stateroot in case of compatibility issues.
@@ -1817,14 +1817,34 @@ bootloader_entry_filename (OstreeSysroot *sysroot, guint n_deployments,
   if (use_old_naming)
     {
       const char *stateroot = ostree_deployment_get_osname (deployment);
-      return g_strdup_printf ("ostree-%d-%s.conf", index, stateroot);
+      return g_strdup_printf ("ostree-%d-%s", index, stateroot);
     }
   else
     {
-      return g_strdup_printf ("ostree-%d.conf", index);
+      return g_strdup_printf ("ostree-%d", index);
     }
 }
 
+static guint
+bootloader_get_max_boot_tries (OstreeSysroot *self, GCancellable *cancellable, GError **error)
+{
+  g_autoptr (OstreeRepo) repo = NULL;
+  if (!ostree_sysroot_get_repo (self, &repo, cancellable, error))
+    return 0;
+
+  return repo->boot_counting;
+}
+
+static gboolean
+bootloader_is_boot_count_enabled (OstreeSysroot *self, GCancellable *cancellable, GError **error)
+{
+  g_autoptr (OstreeRepo) repo = NULL;
+  if (!ostree_sysroot_get_repo (self, &repo, cancellable, error))
+    return FALSE;
+
+  return (repo->boot_counting != 0 ? TRUE : FALSE);
+}
+
 /* Given @deployment, prepare it to be booted; basically copying its
  * kernel/initramfs into /boot/ostree (if needed) and writing out an entry in
  * /boot/loader/entries.
@@ -1859,7 +1879,7 @@ install_deployment_kernel (OstreeSysroot *sysroot, int new_bootversion,
   const char *bootcsum = ostree_deployment_get_bootcsum (deployment);
   g_autofree char *bootcsumdir = g_strdup_printf ("ostree/%s-%s", osname, bootcsum);
   g_autofree char *bootconfdir = g_strdup_printf ("loader.%d/entries", new_bootversion);
-  g_autofree char *bootconf_name = bootloader_entry_filename (sysroot, n_deployments, deployment);
+  g_autofree char *bootconf_name = bootloader_entry_name (sysroot, n_deployments, deployment);
 
   if (!glnx_shutil_mkdir_p_at (sysroot->boot_fd, bootcsumdir, 0775, cancellable, error))
     return FALSE;
@@ -2173,8 +2193,28 @@ install_deployment_kernel (OstreeSysroot *sysroot, int new_bootversion,
   if (!glnx_opendirat (sysroot->boot_fd, bootconfdir, TRUE, &bootconf_dfd, error))
     return FALSE;
 
+  g_autofree char *bootconf_filename;
+  if (bootloader_is_boot_count_enabled(sysroot, cancellable, error))
+    {
+      guint max_tries = bootloader_get_max_boot_tries (sysroot, cancellable, error);
+
+      if (!ostree_bootconfig_parser_is_parsed(bootconfig))
+        bootconf_filename = g_strdup_printf ("%s+%u.conf", bootconf_name, max_tries);
+      else if (!ostree_bootconfig_parser_get_tries_left(bootconfig) &&
+          !ostree_bootconfig_parser_get_tries_done(bootconfig) )
+        bootconf_filename = g_strdup_printf ("%s.conf", bootconf_name);
+      else
+        bootconf_filename = g_strdup_printf ("%s+%" PRIu64 "-%" PRIu64 ".conf", bootconf_name,
+                                             ostree_bootconfig_parser_get_tries_left(bootconfig),
+                                             ostree_bootconfig_parser_get_tries_done(bootconfig));
+    }
+  else
+    {
+      bootconf_filename = g_strdup_printf ("%s.conf", bootconf_name);
+    }
+
   if (!ostree_bootconfig_parser_write_at (ostree_deployment_get_bootconfig (deployment),
-                                          bootconf_dfd, bootconf_name, cancellable, error))
+                                          bootconf_dfd, bootconf_filename, cancellable, error))
     return FALSE;
 
   return TRUE;
@@ -4213,14 +4253,35 @@ ostree_sysroot_deployment_set_kargs_in_place (OstreeSysroot *self, OstreeDeploym
       ostree_bootconfig_parser_set (new_bootconfig, "options", kargs_str);
 
       g_autofree char *bootconf_name
-          = bootloader_entry_filename (self, self->deployments->len, deployment);
+          = bootloader_entry_name (self, self->deployments->len, deployment);
 
       g_autofree char *bootconfdir = g_strdup_printf ("loader.%d/entries", self->bootversion);
       glnx_autofd int bootconf_dfd = -1;
       if (!glnx_opendirat (self->boot_fd, bootconfdir, TRUE, &bootconf_dfd, error))
         return FALSE;
 
-      if (!ostree_bootconfig_parser_write_at (new_bootconfig, bootconf_dfd, bootconf_name,
+      g_autofree char *bootconf_filename;
+      if (bootloader_is_boot_count_enabled(self, cancellable, error))
+        {
+          guint max_tries = bootloader_get_max_boot_tries (self, cancellable, error);
+
+          if (!ostree_bootconfig_parser_is_parsed (new_bootconfig))
+            bootconf_filename = g_strdup_printf ("%s+%u.conf", bootconf_name, max_tries);
+          else if (!ostree_bootconfig_parser_get_tries_left (new_bootconfig)
+                   && !ostree_bootconfig_parser_get_tries_done (new_bootconfig))
+            bootconf_filename = g_strdup_printf ("%s.conf", bootconf_name);
+          else
+            bootconf_filename
+                = g_strdup_printf ("%s+%lu-%lu.conf", bootconf_name,
+                                   ostree_bootconfig_parser_get_tries_left (new_bootconfig),
+                                   ostree_bootconfig_parser_get_tries_done (new_bootconfig));
+        }
+      else
+        {
+          bootconf_filename = g_strdup_printf ("%s.conf", bootconf_name);
+        }
+
+      if (!ostree_bootconfig_parser_write_at (new_bootconfig, bootconf_dfd, bootconf_filename,
                                               cancellable, error))
         return FALSE;
     }