Re: Adding partition guid/uuid to the probe command for use with Linux kernel command line root=PARTUUID=$guid

[Andrei Borzenkov]

14.08.2016 21:31, Steve Kenton пишет:
> I have not look at NTFS yet, but is this more what you were wanting? I'm

Yes. Did you test it?

> not sure about the printing, should grub_gpt_partentry.guid[16] change
> to a UUID struct?
> 

It may make sense if we started to actually use it. Actually we may
probably just as well get rid of special case grub_gpt_part_type_t.

> Steve Kenton
> 
> diff --git a/grub-core/commands/probe.c b/grub-core/commands/probe.c
> index cf2793e..8ff4ff9 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},
> +    {"partguid",    'g', 0, N_("Determine partition guid."), 0, 0},

Linux is using PARTUUID and patches from Nicholas use --target=partuuid,
so let's stick to it.

>      {0, 0, 0, 0, 0, 0}
>    };
> 
> @@ -154,6 +156,43 @@ grub_cmd_probe (grub_extcmd_context_t ctxt, int
> argc, char **args)
>        grub_device_close (dev);
>        return GRUB_ERR_NONE;
>      }
> +  if (state[6].set)
> +    {
> +      char *val;
> +      struct grub_gpt_partentry entry;
> +      if (dev->disk && dev->disk->partition)
> +    {
> +      if (grub_strcmp (dev->disk->partition->partmap->name, "gpt"))
> +        return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
> +               N_("partition map %s does not support partition GUIDs"),
> dev->disk->partition->partmap->name);
> +      if (grub_disk_read (dev->disk, dev->disk->partition->offset,
> dev->disk->partition->index, sizeof(entry), &entry))

You need to read from partition parent, not from partition itself. Usual
hack is to reset disk->partition = disk->partition->parent. See e.g. in
gpt.c itself or in mentioned grub-probe patches.

May be we need to provide something like grub_read_partition_container()
to encapsulate it.

> +        return grub_errno;
> +#if 0
> +      val = grub_xasprintf
> ("%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x", /* should
> grub_gpt_partentry.guid[16] change to a UUID struct? */
> +      grub_be_to_cpu32 (*(grub_uint32_t *) &entry.guid[0]),
> +      grub_be_to_cpu16 (*(grub_uint16_t *) &entry.guid[4]),
> +      grub_be_to_cpu16 (*(grub_uint16_t *) &entry.guid[6]),
> +      entry.guid[8], entry.guid[9],
> +      entry.guid[10], entry.guid[11], entry.guid[12], entry.guid[13],
> entry.guid[14], entry.guid[15]);
> +#else
> +      val = grub_xasprintf
> ("%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
> /* guid is big-endian */

No, EFI GUIDs are little-endian as was discussed in another subthread.
See also grub-probe patches.

> +      entry.guid[0], entry.guid[1], entry.guid[2], entry.guid[3],
> +      entry.guid[4], entry.guid[5],
> +      entry.guid[6], entry.guid[7],
> +      entry.guid[8], entry.guid[9],
> +      entry.guid[10], entry.guid[11], entry.guid[12], entry.guid[13],
> entry.guid[14], entry.guid[15]);
> +#endif
> +    }
> +    else
> +      val = grub_strdup(""); /* set guid to the empty string */
> +      if (state[0].set)
> +    grub_env_set (state[0].arg, val);
> +      else
> +    grub_printf ("%s", val);
> +      grub_free (val);
> +      grub_device_close (dev);
> +      return GRUB_ERR_NONE;
> +    }
>    grub_device_close (dev);
>    return grub_error (GRUB_ERR_BAD_ARGUMENT, "unrecognised target");
>  }