[PATCH] Improve ext2 driver to allow embedding of the boot loader code.

["Dr. Tilmann Bubeck" <tilmann@bubecks.de>]

This patch extends the ext2 driver to allow embedding core.img into the
filesystem. This allows the long needed installation of GRUB into a partition
without the need to use (unsafe) block lists.

It is realized using the ioctl(EXT4_IOC_SWAP_BOOT) introduced into
Linux 3.10. This ioctl basically swaps the data blocks of the associated
file with the EXT2_BOOT_LOADER_INO inode. After using the ioctl the code
of core.img is stored in the BOOT_LOADER incode of the filesystem and it
is not accessible to file system tools anymore. This ensures, that the boot
code is safe and installation into a partition is possible.

The patchs needs 0001-Refactor-grub_read_mountinfo-out-of-grub_find_root_d.patch
to work correctly.

Signed-off-by: Dr. Tilmann Bubeck <tilmann@bubecks.de>
---
 grub-core/fs/ext2.c | 212 ++++++++++++++++++++++++++++++++++++++++++++++++++--
 util/setup.c        |  11 ++-
 2 files changed, 215 insertions(+), 8 deletions(-)

diff --git a/grub-core/fs/ext2.c b/grub-core/fs/ext2.c
index 5f7a2b9..643969e 100644
--- a/grub-core/fs/ext2.c
+++ b/grub-core/fs/ext2.c
@@ -133,6 +133,14 @@ GRUB_MOD_LICENSE ("GPLv3+");
 
 #define EXT4_EXTENTS_FLAG		0x80000
 
+/*
+ * Special inodes numbers
+ */
+#define EXT2_ROOT_INO            2      /* Root inode */
+#define EXT2_BOOT_LOADER_INO     5      /* Boot loader inode */
+
+#define EXT4_IOC_SWAP_BOOT		_IO('f', 17)
+
 /* The ext2 superblock.  */
 struct grub_ext2_sblock
 {
@@ -393,10 +401,10 @@ grub_ext4_find_leaf (struct grub_ext2_data *data,
 }
 
 static grub_disk_addr_t
-grub_ext2_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
+grub_ext2_read_block2 (struct grub_ext2_data *data,
+		       struct grub_ext2_inode *inode,
+		       grub_disk_addr_t fileblock)
 {
-  struct grub_ext2_data *data = node->data;
-  struct grub_ext2_inode *inode = &node->inode;
   unsigned int blksz = EXT2_BLOCK_SIZE (data);
   grub_disk_addr_t blksz_quarter = blksz / 4;
   int log2_blksz = LOG2_EXT2_BLOCK_SIZE (data);
@@ -497,6 +505,12 @@ indirect:
   return grub_le_to_cpu32 (indir);
 }
 
+static grub_disk_addr_t
+grub_ext2_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
+{
+  return grub_ext2_read_block2(node->data, &node->inode, fileblock);
+}
+
 /* Read LEN bytes from the file described by DATA starting with byte
    POS.  Return the amount of read bytes in READ.  */
 static grub_ssize_t
@@ -607,12 +621,12 @@ grub_ext2_mount (grub_disk_t disk)
   data->disk = disk;
 
   data->diropen.data = data;
-  data->diropen.ino = 2;
+  data->diropen.ino = EXT2_ROOT_INO;
   data->diropen.inode_read = 1;
 
   data->inode = &data->diropen.inode;
 
-  grub_ext2_read_inode (data, 2, data->inode);
+  grub_ext2_read_inode (data, EXT2_ROOT_INO, data->inode);
   if (grub_errno)
     goto fail;
 
@@ -977,6 +991,193 @@ grub_ext2_mtime (grub_device_t device, grub_int32_t *tm)
 
 }
 
+#ifdef GRUB_UTIL
+
+#include <stdlib.h>
+#include <sys/ioctl.h>
+#include <include/grub/emu/misc.h>
+#include <include/grub/emu/getroot.h>
+#include <include/grub/emu/hostfile.h>
+
+/* Read the addresses of all sectors occupied by the file with the
+   given inode from the filesystem.  Return the number of sectors in
+   "nsector" and the addresses in "sectors".  "sectors" is allocated
+   in this function and must be freed by the caller after usage.
+   A sector in sectors has size GRUB_DISK_SECTOR_SIZE. */
+static grub_err_t
+grub_ext2_read_sectorlist(grub_device_t device,
+			 int ino,
+			 unsigned int *nsectors,
+			 grub_disk_addr_t **sectors)
+{
+  struct grub_ext2_data *data;
+  struct grub_ext2_inode inode;
+  grub_off_t size;
+  grub_err_t err;
+  grub_disk_addr_t fileblock;
+  int i;
+  grub_disk_addr_t fileblock_count;
+  int sectors_per_block;
+
+  data = grub_ext2_mount (device->disk);
+  if (! data) {
+    return grub_error (grub_errno, N_("Unable to mount device"));
+  }
+
+  err = grub_ext2_read_inode (data, ino, &inode);
+  if (err)
+    return grub_error (err, N_("Unable to read inode #%d"), ino);
+
+  size = grub_le_to_cpu32 (inode.size);
+  size |= ((grub_off_t) grub_le_to_cpu32 (inode.size_high)) << 32;
+
+  fileblock_count = size / EXT2_BLOCK_SIZE(data);
+  if ( size % EXT2_BLOCK_SIZE(data) != 0 ) fileblock_count++;
+
+  sectors_per_block = EXT2_BLOCK_SIZE(data) / GRUB_DISK_SECTOR_SIZE;
+  *sectors = grub_malloc (fileblock_count * sectors_per_block
+			  * sizeof (**sectors));
+  *nsectors = 0;
+  for ( fileblock = 0; fileblock < fileblock_count; fileblock++ ) {
+    (*sectors)[*nsectors] = grub_ext2_read_block2 (data, &inode, fileblock)
+	                    * sectors_per_block;
+    for ( i = 1; i < sectors_per_block; i++) {
+      (*sectors)[(*nsectors) + i] = (*sectors)[*nsectors] + i;
+    }
+    (*nsectors) += sectors_per_block;
+  }
+
+  return GRUB_ERR_NONE;
+}
+
+static grub_err_t
+grub_ext2_embed (grub_device_t device,
+		  unsigned int *nsectors,
+		  unsigned int max_nsectors,
+		  grub_embed_type_t embed_type,
+		  grub_disk_addr_t **sectors)
+{
+  unsigned i;
+  grub_err_t err;
+  char *mountpoint;
+  struct mountinfo_entry *entries;
+  grub_util_fd_t out;
+  char *core_name;
+  char diskbuffer[GRUB_DISK_SECTOR_SIZE];
+  unsigned int nsectors_wanted;
+  char *device_name;
+  int ioctl_err;
+
+  if (embed_type != GRUB_EMBED_PCBIOS)
+    return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
+		       N_("ext2 currently supports only PC-BIOS embedding"));
+
+  if ( device->disk->partition)
+      device_name = grub_xasprintf ("%s,%s", device->disk->name,
+			   grub_partition_get_name(device->disk->partition));
+  else
+      device_name = grub_xasprintf ("%s", device->disk->name);
+
+  nsectors_wanted = *nsectors;
+
+  grub_util_info (N_("Embedding %d/%d sectors into ext2 filesystem of %s"),
+		 nsectors_wanted, max_nsectors, device_name);
+
+  /* [1] Check, if the existing boot loader inode exists and has the
+         wanted size: */
+  err = grub_ext2_read_sectorlist (device, EXT2_BOOT_LOADER_INO,
+				   nsectors, sectors);
+  if (!err && *nsectors >= nsectors_wanted && *nsectors <= max_nsectors) {
+      grub_util_info(N_("Reusing existing boot loader inode"
+			" offering %d sectors"),
+		   *nsectors);
+    grub_free (device_name);
+    return GRUB_ERR_NONE;       /* YES! Everything is fine. */
+  }
+
+  /* [2] We have to create a new boot loader inode. */
+
+  /* [2.1] Check if device is mounted and get mountpoint: */
+  mountpoint = NULL;
+  entries = grub_read_mountinfo ();
+  if ( entries ) {
+    for ( i = 0; entries[i].enc_root[0] != 0; i++) {
+      char *grub_dev_of_mount;
+      grub_errno = GRUB_ERR_NONE;    /* Clear errno set previously */
+      grub_dev_of_mount = grub_util_get_grub_dev (entries[i].device);
+      if ( grub_dev_of_mount ) {
+	if ( grub_strcmp (grub_dev_of_mount, device_name) == 0 ) {
+	  mountpoint = grub_strdup (entries[i].enc_path);
+	  break;
+	}
+      }
+    }
+    free (entries);
+  }
+
+  grub_errno = GRUB_ERR_NONE;    /* Clear errno set previously */
+
+  if (!mountpoint) {
+    /* We were unable to find the mountpoint for the device of the
+       filesystem. Maybe it is not mounted? */
+    return grub_error (GRUB_ERR_UNKNOWN_DEVICE,
+		       N_("We are unable to find the mountpoint of %s"),
+		       device_name);
+
+    /** ToDo: Try to mount the filesystem to a temporary location. */
+  }
+
+  grub_free (device_name);
+
+  /* [2.2] Create a new (temporary) file, which then gets the boot loader: */
+  core_name = grub_util_path_concat (2, mountpoint, ".core.img");
+  free (mountpoint);
+  out = grub_util_fd_open (core_name, GRUB_UTIL_FD_O_WRONLY
+			   | GRUB_UTIL_FD_O_CREATTRUNC);
+  if (!GRUB_UTIL_FD_IS_VALID (out)) {
+    return grub_error (GRUB_ERR_BAD_FS,
+		       N_("cannot create `%s': %s"), core_name,
+		       grub_util_fd_strerror ());
+  }
+  for ( i = 0; i < max_nsectors; i++ ) {
+      grub_util_fd_write (out, diskbuffer, GRUB_DISK_SECTOR_SIZE);
+  }
+  grub_util_fd_sync (out);
+
+  /* [2.3] Make that file to the new boot loader inode by swapping the
+           file of "out" with the boot loader inode: */
+  ioctl_err = ioctl (out, EXT4_IOC_SWAP_BOOT);
+  if ( ioctl_err ) {
+    err = grub_error (GRUB_ERR_BAD_FS,
+		      N_("Error in ioctl(EXT4_IOC_SWAP_BOOT);"
+			 "you need Linux >= 3.10: %s"),
+		      grub_util_fd_strerror ());
+    grub_util_fd_close (out);
+    grub_util_unlink (core_name);
+    return err;
+  }
+  grub_util_fd_close (out);
+
+  /* [2.4] Unlink the core file, now containing the previous boot loader. */
+  grub_util_unlink (core_name);
+
+  /* [2.5] Invalidate disk cache and read block list again: */
+  grub_disk_cache_invalidate_all ();
+
+  err = grub_ext2_read_sectorlist (device, EXT2_BOOT_LOADER_INO,
+				   nsectors, sectors);
+  if ( err ) {
+    return grub_error (GRUB_ERR_BAD_FS,
+		       N_("unable to read boot loader inode"));
+  }
+
+  grub_util_info (N_("Created new boot loader inode offering %d sectors"),
+		     *nsectors);
+
+  return GRUB_ERR_NONE;
+}
+#endif
+
 
 \f
 static struct grub_fs grub_ext2_fs =
@@ -990,6 +1191,7 @@ static struct grub_fs grub_ext2_fs =
     .uuid = grub_ext2_uuid,
     .mtime = grub_ext2_mtime,
 #ifdef GRUB_UTIL
+    .embed = grub_ext2_embed,
     .reserved_first_sector = 1,
     .blocklist_install = 1,
 #endif
diff --git a/util/setup.c b/util/setup.c
index 9fb91a8..3f4a007 100644
--- a/util/setup.c
+++ b/util/setup.c
@@ -509,8 +509,10 @@ SETUP (const char *dir,
     if (!err && nsec < core_sectors)
       {
 	err = grub_error (GRUB_ERR_OUT_OF_RANGE,
-			  N_("Your embedding area is unusually small.  "
-			     "core.img won't fit in it."));
+			  N_("Your embedding area is unusually small "
+			     "(only %d sectors). "
+			     "core.img won't fit in it (needs %d sectors)."),
+			  nsec, core_sectors);
       }
     
     if (err)
@@ -583,10 +585,13 @@ SETUP (const char *dir,
       }
 
     /* Write the core image onto the disk.  */
-    for (i = 0; i < nsec; i++)
+    for (i = 0; i < nsec; i++) {
+	grub_util_info ("writing core.img/%d to sector %" PRIuGRUB_UINT64_T, i,
+			sectors[i]);
       grub_disk_write (dest_dev->disk, sectors[i], 0,
 		       GRUB_DISK_SECTOR_SIZE,
 		       core_img + i * GRUB_DISK_SECTOR_SIZE);
+    }
 
     grub_free (sectors);
 
-- 
1.8.1.4