[PATCH v2 1/9] util/grub-editenv: add basic structures and probe call for external envblk

[Michael Chang via Grub-devel <grub-devel@gnu.org>]

This patch prepares for using an environment block stored in a reserved
area of the filesystem. It adds a constant ENV_BTRFS_OFFSET at 256 KiB
in the Btrfs header. It also introduces the fs_envblk_spec and fs_envblk
structures together with the probe_fs_envblk function to identify the
root filesystem and to avoid configurations that involve diskfilter or
cryptodisk.

The probe is only invoked when grub-editenv is working on the default
environment file path. This restriction ensures that probing and
possible raw device access are not triggered for arbitrary user supplied
paths, but only for the standard grubenv file. In that case the code
checks if the filename equals DEFAULT_ENVBLK_PATH and then calls
probe_fs_envblk with fs_envblk_spec. The result is stored in the global
fs_envblk handle. At this stage the external environment block is only
detected and recorded, and the behavior of grub editenv is unchanged.

Signed-off-by: Michael Chang <mchang@suse.com>
---
 include/grub/fs.h   |   2 +
 util/grub-editenv.c | 153 +++++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 154 insertions(+), 1 deletion(-)

diff --git a/include/grub/fs.h b/include/grub/fs.h
index df4c93b16..1be26dfba 100644
--- a/include/grub/fs.h
+++ b/include/grub/fs.h
@@ -132,4 +132,6 @@ grub_fs_unregister (grub_fs_t fs)
 
 grub_fs_t EXPORT_FUNC(grub_fs_probe) (grub_device_t device);
 
+#define ENV_BTRFS_OFFSET (256 * 1024)
+
 #endif /* ! GRUB_FS_HEADER */
diff --git a/util/grub-editenv.c b/util/grub-editenv.c
index db6f187cc..2302a6acf 100644
--- a/util/grub-editenv.c
+++ b/util/grub-editenv.c
@@ -23,8 +23,11 @@
 #include <grub/util/misc.h>
 #include <grub/lib/envblk.h>
 #include <grub/i18n.h>
-#include <grub/emu/hostfile.h>
+#include <grub/emu/hostdisk.h>
 #include <grub/util/install.h>
+#include <grub/emu/getroot.h>
+#include <grub/fs.h>
+#include <grub/crypto.h>
 
 #include <stdio.h>
 #include <unistd.h>
@@ -120,6 +123,26 @@ block, use `rm %s'."),
   NULL, help_filter, NULL
 };
 
+struct fs_envblk_spec {
+  const char *fs_name;
+  off_t offset;
+  size_t size;
+};
+typedef struct fs_envblk_spec *fs_envblk_spec_t;
+
+struct fs_envblk {
+  struct fs_envblk_spec *spec;
+  const char *dev;
+};
+typedef struct fs_envblk *fs_envblk_t;
+
+static struct fs_envblk_spec fs_envblk_spec[] = {
+  { "btrfs", ENV_BTRFS_OFFSET, GRUB_DISK_SECTOR_SIZE },
+  { NULL, 0, 0 }
+};
+
+static fs_envblk_t fs_envblk = NULL;
+
 static grub_envblk_t
 open_envblk_file (const char *name)
 {
@@ -253,6 +276,131 @@ unset_variables (const char *name, int argc, char *argv[])
   grub_envblk_close (envblk);
 }
 
+static bool
+is_abstraction (grub_device_t dev)
+{
+  if (dev == NULL || dev->disk == NULL)
+    return false;
+
+  if (dev->disk->dev->id == GRUB_DISK_DEVICE_DISKFILTER_ID ||
+      dev->disk->dev->id == GRUB_DISK_DEVICE_CRYPTODISK_ID)
+    return true;
+  return false;
+}
+
+static fs_envblk_t
+probe_fs_envblk (fs_envblk_spec_t spec)
+{
+  char **grub_devices = NULL;
+  char **curdev, **curdrive;
+  size_t ndev = 0;
+  char **grub_drives = NULL;
+  grub_device_t grub_dev = NULL;
+  grub_fs_t grub_fs = NULL;
+  char *devname = NULL;
+  fs_envblk_spec_t p;
+  bool have_abstraction = false;
+
+  grub_util_biosdisk_init (DEFAULT_DEVICE_MAP);
+  grub_init_all ();
+  grub_gcry_init_all ();
+
+  grub_lvm_fini ();
+  grub_mdraid09_fini ();
+  grub_mdraid1x_fini ();
+  grub_diskfilter_fini ();
+  grub_diskfilter_init ();
+  grub_mdraid09_init ();
+  grub_mdraid1x_init ();
+  grub_lvm_init ();
+
+  grub_devices = grub_guess_root_devices (DEFAULT_DIRECTORY);
+
+  if (grub_devices == NULL || grub_devices[0] == NULL)
+    {
+      grub_util_warn (_("cannot find a device for %s (is /dev mounted?)"), DEFAULT_DIRECTORY);
+      goto cleanup;
+    }
+
+  devname = xstrdup (grub_devices[0]);
+
+  for (curdev = grub_devices; *curdev; curdev++, ndev++)
+    grub_util_pull_device (*curdev);
+
+  grub_drives = xcalloc ((ndev + 1), sizeof (grub_drives[0]));
+
+  for (curdev = grub_devices, curdrive = grub_drives; *curdev; curdev++,
+       curdrive++)
+    {
+      *curdrive = grub_util_get_grub_dev (*curdev);
+      if (*curdrive == NULL)
+	{
+	  grub_util_warn (_("cannot find a GRUB drive for %s.  Check your device.map"),
+			  *curdev);
+	  goto cleanup;
+	}
+    }
+  *curdrive = 0;
+
+  grub_dev = grub_device_open (grub_drives[0]);
+  if (grub_dev == NULL)
+    {
+      grub_util_warn (_("cannot open device %s: %s"), grub_drives[0], grub_errmsg);
+      grub_errno = GRUB_ERR_NONE;
+      goto cleanup;
+    }
+
+  grub_fs = grub_fs_probe (grub_dev);
+  if (grub_fs == NULL)
+    {
+      grub_util_warn (_("cannot probe fs for %s: %s"), grub_drives[0], grub_errmsg);
+      grub_errno = GRUB_ERR_NONE;
+      goto cleanup;
+    }
+
+  have_abstraction = is_abstraction (grub_dev);
+  for (curdrive = grub_drives + 1; *curdrive && have_abstraction == false; curdrive++)
+    {
+      grub_device_t dev = grub_device_open (*curdrive);
+      if (dev == NULL)
+	continue;
+      have_abstraction = is_abstraction (dev);
+      grub_device_close (dev);
+    }
+
+ cleanup:
+  if (grub_devices != NULL)
+    for (curdev = grub_devices; *curdev; curdev++)
+      free (*curdev);
+  free (grub_devices);
+  free (grub_drives);
+  grub_device_close (grub_dev);
+  grub_gcry_fini_all ();
+  grub_fini_all ();
+  grub_util_biosdisk_fini ();
+
+  if (grub_fs == NULL)
+    {
+      free (devname);
+      return NULL;
+    }
+
+  for (p = spec; p->fs_name; p++)
+    {
+      if (strcmp (grub_fs->name, p->fs_name) == 0 && !have_abstraction)
+	{
+	  fs_envblk = xmalloc (sizeof (fs_envblk_t));
+	  fs_envblk->spec = p;
+	  fs_envblk->dev = devname;
+	  return fs_envblk;
+	}
+    }
+
+  free (devname);
+  return NULL;
+}
+
+
 int
 main (int argc, char *argv[])
 {
@@ -284,6 +432,9 @@ main (int argc, char *argv[])
       command  = argv[curindex++];
     }
 
+  if (strcmp (filename, DEFAULT_ENVBLK_PATH) == 0)
+    fs_envblk = probe_fs_envblk (fs_envblk_spec);
+
   if (strcmp (command, "create") == 0)
     grub_util_create_envblk_file (filename);
   else if (strcmp (command, "list") == 0)
-- 
2.51.0


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