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