Re: [PATCH 1/1] add --partuuid to probe

["Vladimir 'phcoder' Serbinenko" <phcoder@gmail.com>]

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On Wed, Feb 15, 2017, 17:27 Andrei Borzenkov <arvidjaar@gmail.com> wrote:

> 15.02.2017 13:56, Vladimir 'phcoder' Serbinenko пишет:
> > On Tue, Feb 14, 2017, 19:01 Steve Kenton <skenton@ou.edu> wrote:
> >
> >> Support both EFI and NT Disk Signature for passing to kernel as
> >> root=PARTUUID=$val
> >>
> >> Signed-off-by: Steve Kenton <skenton@ou.edu>
> >> ---
> >> It's been six months so I thought I'd resend this so it does not get
> lost
> >> in case I get hit by a meteor or something before the next release
> >>
> >>  grub-core/commands/probe.c | 53
> >> ++++++++++++++++++++++++++++++++++++++++++++++
> >>  1 file changed, 53 insertions(+)
> >>
> >> diff --git a/grub-core/commands/probe.c b/grub-core/commands/probe.c
> >> index cf2793e..3afc8b8 100644
> >> --- a/grub-core/commands/probe.c
> >> +++ b/grub-core/commands/probe.c
> >> @@ -45,6 +45,7 @@ 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},
> >> +    {"partuuid",       'g', 0, N_("Determine partition GUID/UUID."), 0,
> >> 0}, /* GUID but Linux kernel calls it "PARTUUID" */
> >>
> > I like how it generalizes.
> >
> >>      {0, 0, 0, 0, 0, 0}
> >>    };
> >>
> >> @@ -154,6 +155,58 @@ 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 *partuuid = NULL; /* NULL to silence a spurious GCC warning
> */
> >> +      grub_uint8_t diskbuf[16];
> >> +      if (dev->disk && dev->disk->partition)
> >> +       {
> >> +         grub_partition_t p = dev->disk->partition;
> >> +         if (!grub_strcmp (p->partmap->name, "msdos"))
> >>
> > Please use == 0 rather than !
> >
> >> +           {
> >> +             const int diskid_offset = 440; /* location in MBR */
> >>
> > Please get this from a common header rather than hard coding. I think we
> > have it in msdos.h
> >
> >> +             dev->disk->partition = p->parent;
> >> +             /* little-endian 4-byte NT disk signature */
> >> +             err = grub_disk_read (dev->disk, 0, diskid_offset, 4,
> >> diskbuf);
> >> +             dev->disk->partition = p;
> >> +             if (err)
> >> +               return grub_errno;
> >> +             partuuid = grub_xasprintf ("%02x%02x%02x%02x-%02x",
> >> +                                        diskbuf[3], diskbuf[2],
> >> diskbuf[1], diskbuf[0],
> >> +                                        p->number + 1); /* one based
> >> partition number */
> >>
> > This is not NT-style. NT uses partition offset. Who uses this format? Are
>
> This is used by util-linux and Linux kernel.
>
>
>  *      6) PARTUUID=00112233-4455-6677-8899-AABBCCDDEEFF representing the
>  *         unique id of a partition if the partition table provides it.
>  *         The UUID may be either an EFI/GPT UUID, or refer to an MSDOS
>  *         partition using the format SSSSSSSS-PP, where SSSSSSSS is a
> zero-
>  *         filled hex representation of the 32-bit "NT disk signature",
> and PP
>  *         is a zero-filled hex representation of the 1-based partition
> number.
>
> > you sure that partition numbers are synced with user? Even in presence of
> > Solaris and bsd partitions.
> >
>
> It is not clear what we should return for nested partition. I'm not sure
> whether linux kernel scans nested partitions at all in which case we
> probably should follow the suite and assign PARTUUID to top-level
> partitions only.
>
Linux scans nested partitions and it uses though numeration in dev/sdaX, in
some cases shifting numbering of normal partitions. In those cases grub and
Linux numeration get out of sync

>
> >> +           }
> >> +         else if (!grub_strcmp (p->partmap->name, "gpt"))
> >>
> > Ditto.
> >
> >> +           {
> >> +             const int guid_offset = 16; /* location in entry */
> >>
> > Ditto.
> >
> >> +             dev->disk->partition = p->parent;
> >> +             /* little-endian 16-byte EFI partition GUID */
> >> +             err = grub_disk_read (dev->disk, p->offset, p->index +
> >> guid_offset, 16, diskbuf);
> >> +             dev->disk->partition = p;
> >> +             if (err)
> >> +               return grub_errno;
> >> +             partuuid = grub_xasprintf
> >> ("%02x%02x%02x%02x-%02x%02x-%02x%02x-%02x%02x-%02x%02x%02x%02x%02x%02x",
> >> +                                        diskbuf[3], diskbuf[2],
> >> diskbuf[1], diskbuf[0],
> >> +                                        diskbuf[5], diskbuf[4],
> >> +                                        diskbuf[7], diskbuf[6],
> >> +                                        diskbuf[8], diskbuf[9],
> >> +                                        diskbuf[10], diskbuf[11],
> >> diskbuf[12], diskbuf[13], diskbuf[14], diskbuf[15]);
> >> +           }
> >> +         else
> >> +           return grub_error (GRUB_ERR_NOT_IMPLEMENTED_YET,
> >> +                              N_("partition map %s does not support
> >> partition UUIDs"),
> >> +                              dev->disk->partition->partmap->name);
> >> +       }
> >> +      else
> >> +       partuuid = grub_strdup (""); /* a freeable empty string */
> >> +
> >> +      if (state[0].set)
> >> +       grub_env_set (state[0].arg, partuuid);
> >> +      else
> >> +       grub_printf ("%s", partuuid);
> >> +      grub_free (partuuid);
> >> +      grub_device_close (dev);
> >> +      return GRUB_ERR_NONE;
> >> +    }
> >>    grub_device_close (dev);
> >>    return grub_error (GRUB_ERR_BAD_ARGUMENT, "unrecognised target");
> >>  }
> >> --
> >> 2.9.0.137.gcf4c2cf
> >>
> >>
> >> _______________________________________________
> >> Grub-devel mailing list
> >> Grub-devel@gnu.org
> >> https://lists.gnu.org/mailman/listinfo/grub-devel
> >>
> >
> >
> >
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> >
>
>
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