Ideally the option shouldn't be specific to GPT as other partmaps also have
stable IDs. I think it's better not to have short option at all

On Mon, 13 May 2019, 20:33 Jacob Kroon, <jacob.kr...@gmail.com> wrote:

> Linux supports root=PARTUUID=<partuuid> boot argument, so add
> support for probing it. Compared to the fs UUID, the partition
> UUID does not change when reformatting a partition.
>
> Signed-off-by: Jacob Kroon <jacob.kr...@gmail.com>
> ---
>  docs/grub.texi             |  2 +-
>  grub-core/commands/probe.c | 34 ++++++++++++++++++++++++++++++++++
>  2 files changed, 35 insertions(+), 1 deletion(-)
>
> Changes since v4:
>  * Do endianess byte-swapping on the fly when formatting string
>
> diff --git a/docs/grub.texi b/docs/grub.texi
> index 308b25074..d85818744 100644
> --- a/docs/grub.texi
> +++ b/docs/grub.texi
> @@ -4771,7 +4771,7 @@ a rest.
>  @node probe
>  @subsection probe
>
> -@deffn Command probe [@option{--set} var]
> @option{--driver}|@option{--partmap}|@option{--fs}|@option{--fs-uuid}|@option{--label}
> device
> +@deffn Command probe [@option{--set} var]
> @option{--driver}|@option{--partmap}|@option{--fs}|@option{--fs-uuid}|@option{--label}|@option{--part-uuid}
> device
>  Retrieve device information. If option @option{--set} is given, assign
> result
>  to variable @var{var}, otherwise print information on the screen.
>  @end deffn
> diff --git a/grub-core/commands/probe.c b/grub-core/commands/probe.c
> index 95d272287..b26cbe2cc 100644
> --- a/grub-core/commands/probe.c
> +++ b/grub-core/commands/probe.c
> @@ -24,6 +24,7 @@
>  #include <grub/device.h>
>  #include <grub/disk.h>
>  #include <grub/partition.h>
> +#include <grub/gpt_partition.h>
>  #include <grub/net.h>
>  #include <grub/fs.h>
>  #include <grub/file.h>
> @@ -45,6 +46,7 @@ static const struct grub_arg_option options[] =
>      {"fs",             'f', 0, N_("Determine filesystem type."), 0, 0},
>      {"fs-uuid",                'u', 0, N_("Determine filesystem UUID."),
> 0, 0},
>      {"label",          'l', 0, N_("Determine filesystem label."), 0, 0},
> +    {"part-uuid",      'g', 0, N_("Determine GPT partition UUID."), 0, 0},
>      {0, 0, 0, 0, 0, 0}
>    };
>
> @@ -98,6 +100,38 @@ grub_cmd_probe (grub_extcmd_context_t ctxt, int argc,
> char **args)
>        grub_device_close (dev);
>        return GRUB_ERR_NONE;
>      }
> +  if (state[6].set)
> +    {
> +      /* AAAABBBB-CCCC-DDDD-EEEE-FFFFFFFFFFFF + null terminator */
> +      char val[37] = "none";
> +      if (dev->disk && dev->disk->partition &&
> +         grub_strcmp(dev->disk->partition->partmap->name, "gpt") == 0)
> +       {
> +         struct grub_gpt_partentry entry;
> +         struct grub_partition *p = dev->disk->partition;
> +         grub_disk_t disk = grub_disk_open(dev->disk->name);
> +         if (!disk)
> +           return grub_errno;
> +         if (grub_disk_read(disk, p->offset, p->index, sizeof(entry),
> &entry))
> +           return grub_errno;
> +         grub_disk_close(disk);
> +         grub_gpt_part_guid_t *guid = &entry.guid;
> +         grub_snprintf (val, sizeof(val),
> +
> "%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x",
> +                        grub_le_to_cpu32 (guid->data1),
> +                        grub_le_to_cpu16 (guid->data2),
> +                        grub_le_to_cpu16 (guid->data3),
> +                        guid->data4[0], guid->data4[1], guid->data4[2],
> +                        guid->data4[3], guid->data4[4], guid->data4[5],
> +                        guid->data4[6], guid->data4[7]);
> +       }
> +      if (state[0].set)
> +       grub_env_set (state[0].arg, val);
> +      else
> +       grub_printf ("%s", val);
> +      grub_device_close (dev);
> +      return GRUB_ERR_NONE;
> +    }
>    fs = grub_fs_probe (dev);
>    if (! fs)
>      return grub_errno;
> --
> 2.20.1
>
>
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>
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