[PATCH v2 1/6] efi_loader: add RAM disk device path

[Heinrich Schuchardt]

Am 18. Juli 2023 03:31:30 MESZ schrieb Masahisa Kojima <masahisa.kojima at linaro.org>:
>Hi Heinrich,
>
>On Fri, 14 Jul 2023 at 22:44, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:
>>
>> On 14.07.23 07:44, Masahisa Kojima wrote:
>> > This is a preparation to add the EFI_RAM_DISK_PROTOCOL.
>> > This commit adds the RAM disk device path structure
>> > and text conversion to Device Path to Text Protocol.
>> >
>> > Signed-off-by: Masahisa Kojima <masahisa.kojima at linaro.org>
>> > ---
>> > No update since v1
>> >
>> >   include/efi_api.h                        | 19 +++++++++++++++++++
>> >   lib/efi_loader/efi_device_path_to_text.c | 14 ++++++++++++++
>> >   2 files changed, 33 insertions(+)
>> >
>> > diff --git a/include/efi_api.h b/include/efi_api.h
>> > index 55a4c989fc..4ee4a1b5e9 100644
>> > --- a/include/efi_api.h
>> > +++ b/include/efi_api.h
>> > @@ -682,6 +682,7 @@ struct efi_device_path_uri {
>> >   #  define DEVICE_PATH_SUB_TYPE_CDROM_PATH   0x02
>> >   #  define DEVICE_PATH_SUB_TYPE_VENDOR_PATH  0x03
>> >   #  define DEVICE_PATH_SUB_TYPE_FILE_PATH    0x04
>> > +#  define DEVICE_PATH_SUB_TYPE_RAM_DISK_PATH 0x09
>> >
>> >   struct efi_device_path_hard_drive_path {
>> >       struct efi_device_path dp;
>> > @@ -705,6 +706,24 @@ struct efi_device_path_file_path {
>> >       u16 str[];
>> >   } __packed;
>> >
>> > +/* This GUID defines a RAM Disk supporting a raw disk format in volatile memory */
>> > +#define EFI_VIRTUAL_DISK_GUID \
>> > +     EFI_GUID(0x77ab535a, 0x45fc, 0x624b, \
>> > +     0x55, 0x60, 0xf7, 0xb2, 0x81, 0xd1, 0xf9, 0x6e)
>> > +
>> > +/* This GUID defines a RAM Disk supporting an ISO image in volatile memory */
>> > +#define EFI_VIRTUAL_CD_GUID \
>> > +     EFI_GUID(0x3d5abd30, 0x4175, 0x87ce, \
>> > +              0x6d, 0x64, 0xd2, 0xad, 0xe5, 0x23, 0xc4, 0xbb)
>> > +
>> > +struct efi_device_path_ram_disk_path {
>> > +     struct efi_device_path dp;
>> > +     u64 starting_address;
>> > +     u64 ending_address;
>> > +     efi_guid_t disk_type_guid;
>> > +     u16 disk_instance;
>> > +} __packed;
>> > +
>> >   #define EFI_BLOCK_IO_PROTOCOL_GUID \
>> >       EFI_GUID(0x964e5b21, 0x6459, 0x11d2, \
>> >                0x8e, 0x39, 0x00, 0xa0, 0xc9, 0x69, 0x72, 0x3b)
>> > diff --git a/lib/efi_loader/efi_device_path_to_text.c b/lib/efi_loader/efi_device_path_to_text.c
>> > index 8c76d8be60..4395e79f33 100644
>> > --- a/lib/efi_loader/efi_device_path_to_text.c
>> > +++ b/lib/efi_loader/efi_device_path_to_text.c
>> > @@ -324,6 +324,20 @@ static char *dp_media(char *s, struct efi_device_path *dp)
>> >               free(buffer);
>> >               break;
>> >       }
>> > +     case DEVICE_PATH_SUB_TYPE_RAM_DISK_PATH: {
>> > +             struct efi_device_path_ram_disk_path *rddp =
>> > +                     (struct efi_device_path_ram_disk_path *)dp;
>> > +             u64 start;
>> > +             u64 end;
>> > +
>> > +             /* Copy from packed structure to aligned memory */
>> > +             memcpy(&start, &rddp->starting_address, sizeof(start));
>> > +             memcpy(&end, &rddp->ending_address, sizeof(end));
>> > +
>> > +             s += sprintf(s, "RamDisk(0x%llx,%llx,%pUl,0x%x)", start, end,
>> > +                          &rddp->disk_type_guid, rddp->disk_instance);
>>
>> If there is no alignment guarantee for starting_address, then the same
>> is true for disk_instance which may spread over two u64 blocks.
>
>disk_instance is a u16 field, so it is aligned.

A preceding node, e.g. VenHw(), may have an uneven length?

>
>>
>> In case of DEVICE_PATH_SUB_TYPE_MEMORY we don't use memcpy() to align u64.
>>
>> I don't think we call device_path_to_text before allow_unaligned().
>>
>> There is a family of functions like get_unaligned_le64() if we should
>> ever need to a align a value. Or we could copy the whole device path node.
>
>OK, I will use get_unaligned_le64().

Why do you think this is necessary?

Best regards

Heinrich 

>
>Thanks,
>Masahisa Kojima
>
>>
>> Best regards
>>
>> Heinrich
>>
>> > +             break;
>> > +     }
>> >       default:
>> >               s = dp_unknown(s, dp);
>> >               break;
>>