[PATCH v5 1/2] Warn if MBR gap is small and user uses advanced modules

[Vladimir 'phcoder' Serbinenko]

>From 515ee70c0a289624f71f43cbd09be2a1b929f574 Mon Sep 17 00:00:00 2001
From: Vladimir Serbinenko <phcoder@gmail.com>
Date: Mon, 27 Apr 2020 17:50:04 +0200
Subject: [PATCH 1/2] Warn if MBR gap is small and user uses advanced modules

We don't want to support small MBR gap in pair with anything but
the simplest config of biosdisk+part_msdos+simple filesystem. In this
path "simple filesystems" are all current filesystems except zfs and
btrfs.
---
 grub-core/partmap/gpt.c     |  9 ++++++++-
 grub-core/partmap/msdos.c   |  7 ++++++-
 include/grub/partition.h    |  4 +++-
 include/grub/util/install.h |  7 +++++--
 util/grub-install-common.c  | 24 ++++++++++++++++++++++++
 util/grub-install.c         | 10 +++++++---
 util/grub-setup.c           |  2 +-
 util/setup.c                |  5 +++--
 8 files changed, 57 insertions(+), 11 deletions(-)

diff --git a/grub-core/partmap/gpt.c b/grub-core/partmap/gpt.c
index 72a2e37cd..20cbcc7ff 100644
--- a/grub-core/partmap/gpt.c
+++ b/grub-core/partmap/gpt.c
@@ -25,6 +25,9 @@
 #include <grub/msdos_partition.h>
 #include <grub/gpt_partition.h>
 #include <grub/i18n.h>
+#ifdef GRUB_UTIL
+#include <grub/emu/misc.h>
+#endif

 GRUB_MOD_LICENSE ("GPLv3+");

@@ -169,7 +172,8 @@ static grub_err_t
 gpt_partition_map_embed (struct grub_disk *disk, unsigned int *nsectors,
  unsigned int max_nsectors,
  grub_embed_type_t embed_type,
- grub_disk_addr_t **sectors)
+ grub_disk_addr_t **sectors,
+ int warn_short)
 {
   struct gpt_partition_map_embed_ctx ctx = {
     .start = 0,
@@ -191,6 +195,9 @@ gpt_partition_map_embed (struct grub_disk *disk,
unsigned int *nsectors,
         N_("this GPT partition label contains no BIOS Boot Partition;"
    " embedding won't be possible"));

+  if (ctx.len < GRUB_MIN_RECOMMENDED_MBRGAP) {
+    grub_util_warn("Your BIOS Boot Partition is under 1 MiB, please
increase its size.");
+  }
   if (ctx.len < *nsectors)
     return grub_error (GRUB_ERR_OUT_OF_RANGE,
         N_("your BIOS Boot Partition is too small;"
diff --git a/grub-core/partmap/msdos.c b/grub-core/partmap/msdos.c
index ee3f24982..1483413b2 100644
--- a/grub-core/partmap/msdos.c
+++ b/grub-core/partmap/msdos.c
@@ -236,7 +236,8 @@ static grub_err_t
 pc_partition_map_embed (struct grub_disk *disk, unsigned int *nsectors,
  unsigned int max_nsectors,
  grub_embed_type_t embed_type,
- grub_disk_addr_t **sectors)
+ grub_disk_addr_t **sectors,
+ int warn_short)
 {
   grub_disk_addr_t end = ~0ULL;
   struct grub_msdos_partition_mbr mbr;
@@ -390,6 +391,10 @@ pc_partition_map_embed (struct grub_disk *disk,
unsigned int *nsectors,
       return GRUB_ERR_NONE;
     }

+  if (end < GRUB_MIN_RECOMMENDED_MBRGAP && warn_short) {
+    grub_util_warn("You have a short MBR gap and use advanced config.
Please increase post-MBR gap");
+  }
+
   if (end <= 1)
     return grub_error (GRUB_ERR_FILE_NOT_FOUND,
         N_("this msdos-style partition label has no "
diff --git a/include/grub/partition.h b/include/grub/partition.h
index 7adb7ec6e..adc50d680 100644
--- a/include/grub/partition.h
+++ b/include/grub/partition.h
@@ -52,10 +52,12 @@ struct grub_partition_map
  grub_partition_iterate_hook_t hook, void *hook_data);
 #ifdef GRUB_UTIL
   /* Determine sectors available for embedding.  */
+#define GRUB_MIN_RECOMMENDED_MBRGAP 1900
   grub_err_t (*embed) (struct grub_disk *disk, unsigned int *nsectors,
         unsigned int max_nsectors,
         grub_embed_type_t embed_type,
-        grub_disk_addr_t **sectors);
+        grub_disk_addr_t **sectors,
+        int warn_short);
 #endif
 };
 typedef struct grub_partition_map *grub_partition_map_t;
diff --git a/include/grub/util/install.h b/include/grub/util/install.h
index 2631b1074..640c71d28 100644
--- a/include/grub/util/install.h
+++ b/include/grub/util/install.h
@@ -193,13 +193,13 @@ grub_util_bios_setup (const char *dir,
        const char *boot_file, const char *core_file,
        const char *dest, int force,
        int fs_probe, int allow_floppy,
-       int add_rs_codes);
+       int add_rs_codes, int warn_short_mbr_gap);
 void
 grub_util_sparc_setup (const char *dir,
         const char *boot_file, const char *core_file,
         const char *dest, int force,
         int fs_probe, int allow_floppy,
-        int add_rs_codes);
+        int add_rs_codes, int warn_short_mbr_gap);

 char *
 grub_install_get_image_targets_string (void);
@@ -265,4 +265,7 @@ grub_util_get_target_name (const struct
grub_install_image_target_desc *t);
 extern char *grub_install_copy_buffer;
 #define GRUB_INSTALL_COPY_BUFFER_SIZE 1048576

+int
+grub_install_is_short_mbrgap_supported(void);
+
 #endif
diff --git a/util/grub-install-common.c b/util/grub-install-common.c
index 277eaf4e2..06cb74646 100644
--- a/util/grub-install-common.c
+++ b/util/grub-install-common.c
@@ -234,6 +234,30 @@ char *grub_install_source_directory = NULL;
 char *grub_install_locale_directory = NULL;
 char *grub_install_themes_directory = NULL;

+int
+grub_install_is_short_mbrgap_supported()
+{
+  int i, j;
+  static const char *whitelist[] =
+    {
+     "part_msdos", "biosdisk", "affs", "afs", "bfs", "archelp",
+     "cpio", "cpio_be", "newc", "odc", "ext2", "fat", "exfat",
+     "f2fs", "fshelp", "hfs", "hfsplus",
+     "iso9660", "jfs", "minix", "minix2", "minix3", "minix_be",
+     "minix2_be", "minix2_be", "nilfs2", "ntfs", "ntfscomp",
+     "reiserfs", "romfs", "sfs", "tar", "udf",
+     "ufs1", "ufs1_be", "ufs2", "xfs"
+    };
+  for (i = 0; i < modules.n_entries; i++) {
+    for (j = 0; j < ARRAY_SIZE (whitelist); j++)
+      if (strcmp(modules.entries[i], whitelist[j]) == 0)
+ break;
+    if (j == ARRAY_SIZE (whitelist))
+      return 0;
+  }
+  return 1;
+}
+
 void
 grub_install_push_module (const char *val)
 {
diff --git a/util/grub-install.c b/util/grub-install.c
index a35a2e2e8..c123319c3 100644
--- a/util/grub-install.c
+++ b/util/grub-install.c
@@ -1718,10 +1718,14 @@ main (int argc, char *argv[])
  install_device);

  /*  Now perform the installation.  */
- if (install_bootsector)
+ if (install_bootsector) {
+   int warn_short_mbr_gap = !grub_install_is_short_mbrgap_supported();
+
    grub_util_bios_setup (platdir, "boot.img", "core.img",
  install_drive, force,
- fs_probe, allow_floppy, add_rs_codes);
+ fs_probe, allow_floppy, add_rs_codes,
+ warn_short_mbr_gap);
+ }
  break;
       }
     case GRUB_INSTALL_PLATFORM_SPARC64_IEEE1275:
@@ -1748,7 +1752,7 @@ main (int argc, char *argv[])
    grub_util_sparc_setup (platdir, "boot.img", "core.img",
  install_drive, force,
  fs_probe, allow_floppy,
- 0 /* unused */ );
+ 0 /* unused */, 0 /* unused */ );
  break;
       }

diff --git a/util/grub-setup.c b/util/grub-setup.c
index 42b98ad3c..1783224dd 100644
--- a/util/grub-setup.c
+++ b/util/grub-setup.c
@@ -315,7 +315,7 @@ main (int argc, char *argv[])
     arguments.core_file ? : DEFAULT_CORE_FILE,
     dest_dev, arguments.force,
     arguments.fs_probe, arguments.allow_floppy,
-    arguments.add_rs_codes);
+    arguments.add_rs_codes, 0);

   /* Free resources.  */
   grub_fini_all ();
diff --git a/util/setup.c b/util/setup.c
index 3be88aae1..da5f2c07f 100644
--- a/util/setup.c
+++ b/util/setup.c
@@ -254,7 +254,8 @@ SETUP (const char *dir,
        const char *boot_file, const char *core_file,
        const char *dest, int force,
        int fs_probe, int allow_floppy,
-       int add_rs_codes __attribute__ ((unused))) /* unused on sparc64 */
+       int add_rs_codes __attribute__ ((unused)), /* unused on sparc64 */
+       int warn_small)
 {
   char *core_path;
   char *boot_img, *core_img, *boot_path;
@@ -530,7 +531,7 @@ SETUP (const char *dir,
  GRUB_EMBED_PCBIOS, &sectors);
     else if (ctx.dest_partmap)
       err = ctx.dest_partmap->embed (dest_dev->disk, &nsec, maxsec,
-      GRUB_EMBED_PCBIOS, &sectors);
+      GRUB_EMBED_PCBIOS, &sectors, warn_small);
     else
       err = fs->fs_embed (dest_dev, &nsec, maxsec,
    GRUB_EMBED_PCBIOS, &sectors);
-- 
2.20.1


-- 
Regards
Vladimir 'phcoder' Serbinenko