[U-Boot] [PATCH v2] efi: Export mbr partition for EFI.

[Ard Biesheuvel]

On 20 June 2017 at 13:55, Alexander Graf <agraf at suse.de> wrote:
>
>
> On 20.06.17 08:35, Emmanuel Vadot wrote:
>>
>> While MBR partition isn't supposed to work in a EFI environment some
>
>
> It actually is supposed to work :). I've used it on edk2 based systems a few
> times already.
>

Correct. Even though UEFI reinvented everything including
partitioning, the spec mandates support for MBR, GPT and El Torito for
platforms that have the ability to boot from SSD/HDD drives and/or
optical drives.

>> board rely partially or fully on MBR (BeagleBone, RPI and probably
>> others).
>> This export the MBR partition as logical partition which is useful to efi
>> application that cannot read raw disks.
>>
>> Signed-off-by: Emmanuel Vadot <manu at bidouilliste.com>
>
>
> I think we should do whatever edk2 does here to stay compatible. Ard, can
> you please enlighten me what that would be? Does edk2 expose logical
> partitions as raw disks?
>

The UEFI partition driver consumes block and disk I/O protocols of raw
devices and produces the same protocols for each individual partition
that it recognizes.

I hope this answers your question, otherwise could you elaborate?


>> ---
>> Changes in v2:
>>   * Pass correct arg to efi_disk_create_mbr
>>
>>   lib/efi_loader/efi_disk.c | 59
>> +++++++++++++++++++++++++++++++++++++++--------
>>   1 file changed, 50 insertions(+), 9 deletions(-)
>>
>> diff --git a/lib/efi_loader/efi_disk.c b/lib/efi_loader/efi_disk.c
>> index 39e602a868..097bb544d7 100644
>> --- a/lib/efi_loader/efi_disk.c
>> +++ b/lib/efi_loader/efi_disk.c
>> @@ -197,11 +197,13 @@ static void efi_disk_add_dev(const char *name,
>>                              const char *if_typename,
>>                              const struct blk_desc *desc,
>>                              int dev_index,
>> -                            lbaint_t offset)
>> +                            disk_partition_t *info,
>> +                            int logical_partition)
>>   {
>>         struct efi_disk_obj *diskobj;
>>         struct efi_device_path_file_path *dp;
>>         int objlen = sizeof(*diskobj) + (sizeof(*dp) * 2);
>> +       static int mediaid;
>>         /* Don't add empty devices */
>>         if (!desc->lba)
>> @@ -218,16 +220,26 @@ static void efi_disk_add_dev(const char *name,
>>         diskobj->ops = block_io_disk_template;
>>         diskobj->ifname = if_typename;
>>         diskobj->dev_index = dev_index;
>> -       diskobj->offset = offset;
>> +       if (info)
>> +               diskobj->offset = info->start;
>> +
>>         diskobj->desc = desc;
>>         /* Fill in EFI IO Media info (for read/write callbacks) */
>>         diskobj->media.removable_media = desc->removable;
>>         diskobj->media.media_present = 1;
>> -       diskobj->media.block_size = desc->blksz;
>> -       diskobj->media.io_align = desc->blksz;
>> -       diskobj->media.last_block = desc->lba - offset;
>> +       diskobj->media.media_id = mediaid++;
>>         diskobj->ops.media = &diskobj->media;
>> +       if (logical_partition) {
>> +               diskobj->media.logical_partition = 1;
>> +               diskobj->media.block_size = info->blksz;
>> +               diskobj->media.io_align = info->blksz;
>> +               diskobj->media.last_block = info->size - 1;
>> +       } else {
>> +               diskobj->media.block_size = desc->blksz;
>> +               diskobj->media.io_align = desc->blksz;
>> +               diskobj->media.last_block = desc->lba;
>> +       }
>>         /* Fill in device path */
>>         dp = (void*)&diskobj[1];
>> @@ -262,8 +274,33 @@ static int efi_disk_create_eltorito(struct blk_desc
>> *desc,
>>         while (!part_get_info(desc, part, &info)) {
>>                 snprintf(devname, sizeof(devname), "%s:%d", pdevname,
>>                          part);
>> -               efi_disk_add_dev(devname, if_typename, desc, diskid,
>> -                                info.start);
>> +               efi_disk_add_dev(devname, if_typename, desc, diskid, 0,
>> 0);
>> +               part++;
>> +               disks++;
>> +       }
>> +#endif
>> +
>> +       return disks;
>> +}
>> +
>> +static int efi_disk_create_mbr(struct blk_desc *desc,
>> +                                   const char *if_typename,
>> +                                   int diskid)
>> +{
>> +       int disks = 0;
>> +#if CONFIG_IS_ENABLED(DOS_PARTITION)
>> +       char devname[32] = { 0 }; /* dp->str is u16[32] long */
>> +       disk_partition_t info;
>> +       int part = 1;
>> +
>> +       if (desc->part_type != PART_TYPE_DOS)
>> +               return 0;
>> +
>> +       while (!part_get_info(desc, part, &info)) {
>> +               snprintf(devname, sizeof(devname), "%s%d:%d", if_typename,
>> +                        diskid, part);
>> +
>> +               efi_disk_add_dev(devname, if_typename, desc, diskid,
>> &info, 1);
>>                 part++;
>>                 disks++;
>>         }
>> @@ -296,9 +333,11 @@ int efi_disk_register(void)
>>                 const char *if_typename = dev->driver->name;
>>                 printf("Scanning disk %s...\n", dev->name);
>> -               efi_disk_add_dev(dev->name, if_typename, desc,
>> desc->devnum, 0);
>> +               efi_disk_add_dev(dev->name, if_typename, desc,
>> desc->devnum,
>> +                                NULL, 0);
>>                 disks++;
>>   +             disks += efi_disk_create_mbr(desc, if_typename,
>> desc->devnum);
>>                 /*
>>                 * El Torito images show up as block devices in an EFI
>> world,
>>                 * so let's create them here
>> @@ -332,15 +371,17 @@ int efi_disk_register(void)
>>                         snprintf(devname, sizeof(devname), "%s%d",
>>                                  if_typename, i);
>> -                       efi_disk_add_dev(devname, if_typename, desc, i,
>> 0);
>> +                       efi_disk_add_dev(devname, if_typename, desc, i, 0,
>> 0);
>>                         disks++;
>>   +                     disks += efi_disk_create_mbr(desc, if_typename,
>> i);
>>                         /*
>>                          * El Torito images show up as block devices
>>                          * in an EFI world, so let's create them here
>>                          */
>>                         disks += efi_disk_create_eltorito(desc,
>> if_typename,
>>                                                           i, devname);
>> +
>>                 }
>>         }
>>   #endif
>>
>