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[PATCH v4] Support to disable reed-solomon codes
|
From: |
Jon McCune |
|
Subject: |
[PATCH v4] Support to disable reed-solomon codes |
|
Date: |
Mon, 9 Dec 2013 11:54:57 -0800 |
[v0] new grub-*-setup flag to disable insertion of reed solomon codes
[v0] grub-install support for option --no-rs-codes
[v1] bugfix: also change the maxsec value in util/setup.c
[v2] Modified to support new C-language install utilities, added documentation
[v3] Incorporate feedback from ML. Most significant changes:
Clarify Reed Solomon code behavior in documentation
Use positive logic within code
Move core.img version check outside add_rs_codes conditional
[v4] Use enum and start from 0x100 for no-short-form option
Zero extra memory returned by realloc() prior to use
Signed-off-by: Jon McCune <address@hidden>
---
docs/grub.texi | 14 +++++++++++++-
include/grub/util/install.h | 6 ++++--
util/grub-install.c | 19 +++++++++++++++----
util/grub-setup.c | 19 +++++++++++++++++--
util/setup.c | 39 ++++++++++++++++++++++++++-------------
5 files changed, 75 insertions(+), 22 deletions(-)
diff --git a/docs/grub.texi b/docs/grub.texi
index 54b02fd..91fa1de 100644
--- a/docs/grub.texi
+++ b/docs/grub.texi
@@ -5994,8 +5994,20 @@ mounted on
Recheck the device map, even if @file{/boot/grub/device.map} already
exists. You should use this option whenever you add/remove a disk
into/from your computer.
address@hidden table
address@hidden --no-rs-codes
+By default on x86 BIOS systems, @command{grub-install} will use some
+extra space in the bootloader embedding area for Reed-Solomon
+error-correcting codes. This enables GRUB to still boot successfully
+if some blocks are corrupted. The exact amount of protection offered
+is dependent on available space in the embedding area. R sectors of
+redundancy can tolerate up to R/2 corrupted sectors. This
+redundancy may be cumbersome if attempting to cryptographically
+validate the contents of the bootloader embedding area, or in more
+modern systems with GPT-style partition tables (@pxref{BIOS
+installation}) where GRUB does not reside in any unpartitioned space
+outside of the MBR. Disable the Reed-Solomon codes with this option.
address@hidden table
@node Invoking grub-mkconfig
@chapter Invoking grub-mkconfig
diff --git a/include/grub/util/install.h b/include/grub/util/install.h
index beca2d2..20626d4 100644
--- a/include/grub/util/install.h
+++ b/include/grub/util/install.h
@@ -183,12 +183,14 @@ void
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 fs_probe, int allow_floppy,
+ int add_rs_codes);
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 fs_probe, int allow_floppy,
+ int add_rs_codes);
char *
grub_install_get_image_targets_string (void);
diff --git a/util/grub-install.c b/util/grub-install.c
index 0aa7f48..5d22f90 100644
--- a/util/grub-install.c
+++ b/util/grub-install.c
@@ -68,6 +68,7 @@ static int have_load_cfg = 0;
static FILE * load_cfg_f = NULL;
static char *load_cfg;
static int install_bootsector = 1;
+static int add_rs_codes = 1;
enum
{
@@ -93,7 +94,8 @@ enum
OPTION_DEBUG_IMAGE,
OPTION_NO_FLOPPY,
OPTION_DISK_MODULE,
- OPTION_NO_BOOTSECTOR
+ OPTION_NO_BOOTSECTOR,
+ OPTION_NO_RS_CODES,
};
static int fs_probe = 1;
@@ -180,6 +182,10 @@ argp_parser (int key, char *arg, struct argp_state *state)
install_bootsector = 0;
return 0;
+ case OPTION_NO_RS_CODES:
+ add_rs_codes = 0;
+ return 0;
+
case OPTION_DEBUG:
verbosity++;
return 0;
@@ -238,6 +244,9 @@ static struct argp_option options[] = {
N_("do not probe for filesystems in DEVICE"), 0},
{"no-bootsector", OPTION_NO_BOOTSECTOR, 0, 0,
N_("do not install bootsector"), 0},
+ {"no-rs-codes", OPTION_NO_RS_CODES, 0, 0,
+ N_("Do not apply any reed-solomon codes when embedding core.img. "
+ "This option is only available on x86 BIOS targets."), 0},
{"debug", OPTION_DEBUG, 0, OPTION_HIDDEN, 0, 2},
{"no-floppy", OPTION_NO_FLOPPY, 0, OPTION_HIDDEN, 0, 2},
@@ -1435,12 +1444,13 @@ main (int argc, char *argv[])
"boot.img");
grub_install_copy_file (boot_img_src, boot_img, 1);
- grub_util_info ("%sgrub-bios-setup %s %s %s %s --directory='%s'
--device-map='%s' '%s'",
+ grub_util_info ("%sgrub-bios-setup %s %s %s %s %s --directory='%s'
--device-map='%s' '%s'",
install_bootsector ? "" : "NOT RUNNING: ",
allow_floppy ? "--allow-floppy " : "",
verbosity ? "--verbose " : "",
force ? "--force " : "",
!fs_probe ? "--skip-fs-probe" : "",
+ !add_rs_codes ? "--no-rs-codes" : "",
platdir,
device_map,
install_device);
@@ -1449,7 +1459,7 @@ main (int argc, char *argv[])
if (install_bootsector)
grub_util_bios_setup (platdir, "boot.img", "core.img",
install_drive, force,
- fs_probe, allow_floppy);
+ fs_probe, allow_floppy, add_rs_codes);
break;
}
case GRUB_INSTALL_PLATFORM_SPARC64_IEEE1275:
@@ -1475,7 +1485,8 @@ main (int argc, char *argv[])
if (install_bootsector)
grub_util_sparc_setup (platdir, "boot.img", "core.img",
install_device, force,
- fs_probe, allow_floppy);
+ fs_probe, allow_floppy,
+ 0 /* unused */ );
break;
}
diff --git a/util/grub-setup.c b/util/grub-setup.c
index 90b9de0..7a6ca78 100644
--- a/util/grub-setup.c
+++ b/util/grub-setup.c
@@ -64,6 +64,12 @@
#define DEFAULT_BOOT_FILE "boot.img"
#define DEFAULT_CORE_FILE "core.img"
+/* Non-printable "keys" for arguments with no short form.
+ * See grub-core/gnulib/argp.h for details. */
+enum {
+ NO_RS_CODES_KEY = 0x100,
+};
+
static struct argp_option options[] = {
{"boot-image", 'b', N_("FILE"), 0,
N_("use FILE as the boot image [default=%s]"), 0},
@@ -82,7 +88,9 @@ static struct argp_option options[] = {
/* TRANSLATORS: The potential breakage isn't limited to floppies but it's
likely to make the install unbootable from HDD. */
N_("make the drive also bootable as floppy (default for fdX devices). May
break on some BIOSes."), 0},
-
+ {"no-rs-codes", NO_RS_CODES_KEY, 0, 0,
+ N_("Do not apply any reed-solomon codes when embedding core.img. "
+ "This option is only available on x86 BIOS targets."), 0},
{ 0, 0, 0, 0, 0, 0 }
};
@@ -118,6 +126,7 @@ struct arguments
int fs_probe;
int allow_floppy;
char *device;
+ int add_rs_codes;
};
static error_t
@@ -173,6 +182,10 @@ argp_parser (int key, char *arg, struct argp_state *state)
verbosity++;
break;
+ case NO_RS_CODES_KEY:
+ arguments->add_rs_codes = 0;
+ break;
+
case ARGP_KEY_ARG:
if (state->arg_num == 0)
arguments->device = xstrdup(arg);
@@ -233,6 +246,7 @@ main (int argc, char *argv[])
/* Default option values. */
memset (&arguments, 0, sizeof (struct arguments));
arguments.fs_probe = 1;
+ arguments.add_rs_codes = 1;
/* Parse our arguments */
if (argp_parse (&argp, argc, argv, 0, 0, &arguments) != 0)
@@ -292,7 +306,8 @@ main (int argc, char *argv[])
arguments.boot_file ? : DEFAULT_BOOT_FILE,
arguments.core_file ? : DEFAULT_CORE_FILE,
dest_dev, arguments.force,
- arguments.fs_probe, arguments.allow_floppy);
+ arguments.fs_probe, arguments.allow_floppy,
+ arguments.add_rs_codes);
/* Free resources. */
grub_fini_all ();
diff --git a/util/setup.c b/util/setup.c
index 337c304..682b320 100644
--- a/util/setup.c
+++ b/util/setup.c
@@ -248,7 +248,8 @@ void
SETUP (const char *dir,
const char *boot_file, const char *core_file,
const char *dest, int force,
- int fs_probe, int allow_floppy)
+ int fs_probe, int allow_floppy,
+ int add_rs_codes __attribute__ ((unused))) /* unused on sparc64 */
{
char *core_path;
char *boot_img, *core_img, *boot_path;
@@ -486,7 +487,11 @@ SETUP (const char *dir,
nsec = core_sectors;
- maxsec = 2 * core_sectors;
+ if (add_rs_codes)
+ maxsec = 2 * core_sectors;
+ else
+ maxsec = core_sectors;
+
if (maxsec > ((0x78000 - GRUB_KERNEL_I386_PC_LINK_ADDR)
>> GRUB_DISK_SECTOR_BITS))
maxsec = ((0x78000 - GRUB_KERNEL_I386_PC_LINK_ADDR)
@@ -543,15 +548,16 @@ SETUP (const char *dir,
write_rootdev (root_dev, boot_img, bl.first_sector);
+ /* Round up to the nearest sector boundary, and zero the extra memory */
core_img = realloc (core_img, nsec * GRUB_DISK_SECTOR_SIZE);
+ assert (core_img && (nsec * GRUB_DISK_SECTOR_SIZE >= core_size));
+ memset (core_img + core_size, 0, nsec * GRUB_DISK_SECTOR_SIZE - core_size);
+
bl.first_block = (struct grub_boot_blocklist *) (core_img
+ GRUB_DISK_SECTOR_SIZE
- sizeof (*bl.block));
grub_size_t no_rs_length;
- grub_set_unaligned32 ((core_img + GRUB_DISK_SECTOR_SIZE
- + GRUB_KERNEL_I386_PC_REED_SOLOMON_REDUNDANCY),
- grub_host_to_target32 (nsec * GRUB_DISK_SECTOR_SIZE -
core_size));
no_rs_length = grub_target_to_host16
(grub_get_unaligned16 (core_img
+ GRUB_DISK_SECTOR_SIZE
@@ -560,14 +566,21 @@ SETUP (const char *dir,
if (no_rs_length == 0xffff)
grub_util_error ("%s", _("core.img version mismatch"));
- void *tmp = xmalloc (core_size);
- grub_memcpy (tmp, core_img, core_size);
- grub_reed_solomon_add_redundancy (core_img + no_rs_length +
GRUB_DISK_SECTOR_SIZE,
- core_size - no_rs_length -
GRUB_DISK_SECTOR_SIZE,
- nsec * GRUB_DISK_SECTOR_SIZE
- - core_size);
- assert (grub_memcmp (tmp, core_img, core_size) == 0);
- free (tmp);
+ if (add_rs_codes)
+ {
+ grub_set_unaligned32 ((core_img + GRUB_DISK_SECTOR_SIZE
+ + GRUB_KERNEL_I386_PC_REED_SOLOMON_REDUNDANCY),
+ grub_host_to_target32 (nsec *
GRUB_DISK_SECTOR_SIZE - core_size));
+
+ void *tmp = xmalloc (core_size);
+ grub_memcpy (tmp, core_img, core_size);
+ grub_reed_solomon_add_redundancy (core_img + no_rs_length +
GRUB_DISK_SECTOR_SIZE,
+ core_size - no_rs_length -
GRUB_DISK_SECTOR_SIZE,
+ nsec * GRUB_DISK_SECTOR_SIZE
+ - core_size);
+ assert (grub_memcmp (tmp, core_img, core_size) == 0);
+ free (tmp);
+ }
/* Write the core image onto the disk. */
for (i = 0; i < nsec; i++)
--
1.8.5.1
- [PATCH v4] Support to disable reed-solomon codes,
Jon McCune <=