[PATCH] grub-core: modify sector by sysfs as disk sector

[PATCH] grub-core: modify sector by sysfs as disk sector

[Mukesh Kumar Chaurasiya]

The disk sector size provided by sysfs file system considers the
sector size of 512 irrespective of disk sector size, Thus
causing the read by grub to an incorrect offset from what was
originally intended.

Considering the 512 sector size of sysfs data the actual sector
needs to be modified corresponding to disk sector size.

Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.vnet.ibm.com>
---
 grub-core/osdep/linux/hostdisk.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/grub-core/osdep/linux/hostdisk.c b/grub-core/osdep/linux/hostdisk.c
index 07058f63a..13e4e2feb 100644
--- a/grub-core/osdep/linux/hostdisk.c
+++ b/grub-core/osdep/linux/hostdisk.c
@@ -197,8 +197,15 @@ have_devfs (void)
 
 #pragma GCC diagnostic ignored "-Wformat-nonliteral"
 
+static inline grub_disk_addr_t
+transform_sector (grub_disk_t disk, grub_disk_addr_t sector)
+{
+  return sector >> (disk->log_sector_size - GRUB_DISK_SECTOR_BITS);
+}
+
 static int
-grub_hostdisk_linux_find_partition (char *dev, grub_disk_addr_t sector)
+grub_hostdisk_linux_find_partition (const grub_disk_t disk, char *dev,
+                                    grub_disk_addr_t sector)
 {
   size_t len = strlen (dev);
   const char *format;
@@ -263,7 +270,8 @@ grub_hostdisk_linux_find_partition (char *dev, grub_disk_addr_t sector)
       if (fstat (fd, &st) < 0
 	  || !grub_util_device_is_mapped_stat (&st)
 	  || !grub_util_get_dm_node_linear_info (st.st_rdev, 0, 0, &start))
-	start = grub_util_find_partition_start_os (real_dev);
+	start = transform_sector (disk,
+                                 grub_util_find_partition_start_os (real_dev));
       /* We don't care about errors here.  */
       grub_errno = GRUB_ERR_NONE;
 
@@ -344,7 +352,8 @@ grub_util_fd_open_device (const grub_disk_t disk, grub_disk_addr_t sector, int f
 	&& strncmp (dev, "/dev/", 5) == 0)
       {
 	if (sector >= part_start)
-	  is_partition = grub_hostdisk_linux_find_partition (dev, part_start);
+	  is_partition = grub_hostdisk_linux_find_partition (disk, dev,
+                                                            part_start);
 	else
 	  *max = part_start - sector;
       }
-- 
2.31.1

Re: [PATCH] grub-core: modify sector by sysfs as disk sector

[Daniel Kiper]

On Fri, Feb 03, 2023 at 10:10:43AM +0530, Mukesh Kumar Chaurasiya wrote:
> The disk sector size provided by sysfs file system considers the
> sector size of 512 irrespective of disk sector size, Thus
> causing the read by grub to an incorrect offset from what was
> originally intended.
>
> Considering the 512 sector size of sysfs data the actual sector
> needs to be modified corresponding to disk sector size.
>
> Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.vnet.ibm.com>
> ---
>  grub-core/osdep/linux/hostdisk.c | 15 ++++++++++++---
>  1 file changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/grub-core/osdep/linux/hostdisk.c b/grub-core/osdep/linux/hostdisk.c
> index 07058f63a..13e4e2feb 100644
> --- a/grub-core/osdep/linux/hostdisk.c
> +++ b/grub-core/osdep/linux/hostdisk.c
> @@ -197,8 +197,15 @@ have_devfs (void)
>
>  #pragma GCC diagnostic ignored "-Wformat-nonliteral"
>
> +static inline grub_disk_addr_t
> +transform_sector (grub_disk_t disk, grub_disk_addr_t sector)
> +{
> +  return sector >> (disk->log_sector_size - GRUB_DISK_SECTOR_BITS);
> +}

Please take a look at include/grub/disk.h:grub_disk_from_native_sector()
and define grub_disk_to_native_sector() next to it.

> +
>  static int
> -grub_hostdisk_linux_find_partition (char *dev, grub_disk_addr_t sector)
> +grub_hostdisk_linux_find_partition (const grub_disk_t disk, char *dev,
> +                                    grub_disk_addr_t sector)
>  {
>    size_t len = strlen (dev);
>    const char *format;
> @@ -263,7 +270,8 @@ grub_hostdisk_linux_find_partition (char *dev, grub_disk_addr_t sector)
>        if (fstat (fd, &st) < 0
>  	  || !grub_util_device_is_mapped_stat (&st)
>  	  || !grub_util_get_dm_node_linear_info (st.st_rdev, 0, 0, &start))
> -	start = grub_util_find_partition_start_os (real_dev);
> +	start = transform_sector (disk,
> +                                 grub_util_find_partition_start_os (real_dev));

You do not need to wrap lines which are a bit longer than 80 characters.

>        /* We don't care about errors here.  */
>        grub_errno = GRUB_ERR_NONE;
>
> @@ -344,7 +352,8 @@ grub_util_fd_open_device (const grub_disk_t disk, grub_disk_addr_t sector, int f
>  	&& strncmp (dev, "/dev/", 5) == 0)
>        {
>  	if (sector >= part_start)
> -	  is_partition = grub_hostdisk_linux_find_partition (dev, part_start);
> +	  is_partition = grub_hostdisk_linux_find_partition (disk, dev,
> +                                                            part_start);

Ditto.

Daniel