Add ostree=aboot for signed Android Boot Images

Some kernel images are delivered in a signed kernel + cmdline +
initramfs + dtb blob. When this is added to the commit server side, only
after this do you know what the cmdline is, this creates a recursion
issue. To avoid this, in the case where we have ostree=aboot karg
set, do the bls parsing in the initramfs instead, so we can take
advantage of existing bls logic.

src/switchroot/ostree-mount-util.h

@@ -21,17 +21,19 @@
 #ifndef __OSTREE_MOUNT_UTIL_H_
 #define __OSTREE_MOUNT_UTIL_H_
 
+#include <dirent.h>
 #include <err.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdio.h>
 #include <stdlib.h>
+#include <string.h>
 #include <sys/statvfs.h>
-#include <stdio.h>
 #include <unistd.h>
-#include <fcntl.h>
-#include <string.h>
-#include <stdbool.h>
 
 #define INITRAMFS_MOUNT_VAR "/run/ostree/initramfs-mount-var"
 #define _OSTREE_SYSROOT_READONLY_STAMP "/run/ostree-sysroot-ro.stamp"
+#define ABOOT_KARG "aboot"
 
 static inline int
 path_is_on_readonly_fs (const char *path)
@@ -72,6 +74,26 @@ read_proc_cmdline (void)
   return cmdline;
 }
 
+static inline void
+free_char (char **to_free)
+{
+  free (*to_free);
+}
+
+static inline void
+close_dir (DIR **dir)
+{
+  if (*dir)
+    closedir (*dir);
+}
+
+static inline void
+close_file (FILE **f)
+{
+  if (*f)
+    fclose (*f);
+}
+
 static inline char *
 read_proc_cmdline_ostree (void)
 {
@@ -106,6 +128,118 @@ read_proc_cmdline_ostree (void)
   return ret;
 }
 
+/* If the key matches the start of the line, strip the key from the line just
+ * to get the value
+ */
+static inline bool
+rm_key_if_match (char *line, const char *key, const size_t key_len, char *out)
+{
+  if (strstr (line, key) == line)
+    {
+      char *value = line + key_len;
+      strcpy (out, value);
+      return true;
+    }
+
+  return false;
+}
+
+/* On completion version and options will be set to new values if the version
+ * is more recent. Will loop line through line on the passed in open FILE.
+ */
+static inline int
+copy_if_higher_version (FILE *f, char *version, char *options)
+{
+  char __attribute__ ((cleanup (free_char))) *line = NULL;
+  char version_local[PATH_MAX] = "";
+  char options_local[PATH_MAX] = "";
+  /* Note getline() will reuse the previous buffer */
+  for (size_t len = 0; getline (&line, &len, f) != -1;)
+    {
+      /* This is an awful hack to avoid depending on GLib in the
+       * initramfs right now.
+       */
+      if (rm_key_if_match (line, "version ", sizeof ("version"),
+                           version_local))
+        {
+          if (options_local[0])
+            break;
+
+          continue;
+        }
+
+      if (rm_key_if_match (line, "options ", sizeof ("options"),
+                           options_local))
+        {
+          if (version_local[0])
+            break;
+
+          continue;
+        }
+    }
+
+  const int ret = strverscmp (version_local, version);
+  if (ret > 0)
+    {
+      strcpy (version, version_local);
+      strcpy (options, options_local);
+    }
+
+  return ret;
+}
+
+/* This function is for boot arrangements where it is not possible to use a
+ * karg/cmdline, this is the case when the cmdline is part of the signed
+ * boot image, alternatively this function takes the karg from the bls entry
+ * which will have the correct ostree= karg set. This bls entry is not parsed
+ * from the bootloader but from the initramfs instead.
+ */
+static inline char *
+bls_parser_get_ostree_option (const char *sysroot)
+{
+  char out[PATH_MAX] = "";
+  int written = snprintf (out, PATH_MAX, "%s/boot/loader/entries", sysroot);
+  DIR __attribute__ ((cleanup (close_dir))) *dir = opendir (out);
+  if (!dir)
+    {
+      fprintf (stderr, "opendir(\"%s\") failed with %d\n", out, errno);
+      return strdup ("");
+    }
+
+  char version[PATH_MAX] = "";
+  char options[PATH_MAX] = "";
+  for (struct dirent *ent = 0; (ent = readdir (dir));)
+    {
+      if (ent->d_name[0] == '.')
+        continue;
+
+      snprintf (out + written, PATH_MAX - written, "/%s", ent->d_name);
+
+      FILE __attribute__ ((cleanup (close_file))) *f = fopen (out, "r");
+      if (!f)
+        {
+          fprintf (stderr, "fopen(\"%s\", \"r\") failed with %d\n", out,
+                   errno);
+          continue;
+        }
+
+      copy_if_higher_version (f, version, options);
+    }
+
+  if (options[0])
+    {
+      char *start_of_ostree = strstr (options, "ostree=");
+      if (start_of_ostree > options)
+        {
+          start_of_ostree += sizeof ("ostree");
+          strtok (start_of_ostree, " \t\r\n"); // trim everything to the right
+          return strdup (start_of_ostree);
+        }
+    }
+
+  return strdup ("");
+}
+
 /* This is an API for other projects to determine whether or not the
  * currently running system is ostree-controlled.
  */

src/switchroot/ostree-prepare-root.c

@@ -124,9 +124,13 @@ resolve_deploy_path (const char * root_mountpoint)
 {
   char destpath[PATH_MAX];
   struct stat stbuf;
-  char *ostree_target, *deploy_path;
+  char __attribute__ ((cleanup (free_char))) * ostree_target;
+  char *deploy_path;
 
   ostree_target = read_proc_cmdline_ostree ();
+  if (!strcmp (ostree_target, ABOOT_KARG))
+    ostree_target = bls_parser_get_ostree_option (root_mountpoint);
+
   if (!ostree_target)
     errx (EXIT_FAILURE, "No OSTree target; expected ostree=/ostree/boot.N/...");
 

src/switchroot/ostree-system-generator.c

@@ -62,7 +62,11 @@ main(int argc, char *argv[])
    * exit so that we don't error, but at the same time work where switchroot
    * is PID 1 (and so hasn't created /run/ostree-booted).
    */
-  char *ostree_cmdline = read_proc_cmdline_ostree ();
+  char __attribute__ ((cleanup (free_char))) *ostree_cmdline
+      = read_proc_cmdline_ostree ();
+  if (!strcmp (ostree_cmdline, ABOOT_KARG))
+    ostree_cmdline = bls_parser_get_ostree_option ("/sysroot");
+
   if (!ostree_cmdline)
     exit (EXIT_SUCCESS);