Re: [edk2-devel] [PATCH V2 2/3] MdeModulePkg/PartitionDxe: Revert changes for the special MBR

["Wu, Hao A" <hao.a.wu@intel.com>]

> -----Original Message-----
> From: devel@edk2.groups.io <devel@edk2.groups.io> On Behalf Of Gao,
> Zhichao
> Sent: Wednesday, August 12, 2020 9:21 AM
> To: devel@edk2.groups.io
> Cc: Wang, Jian J <jian.j.wang@intel.com>; Wu, Hao A
> <hao.a.wu@intel.com>; Ni, Ray <ray.ni@intel.com>; Gary Lin
> <glin@suse.com>; Andrew Fish <afish@apple.com>
> Subject: [edk2-devel] [PATCH V2 2/3] MdeModulePkg/PartitionDxe: Revert
> changes for the special MBR
> 
> REF: https://bugzilla.tianocore.org/show_bug.cgi?id=2823
> 
> Revert "MdeModulePkg/PartitionDxe: Skip the MBR that add for CD-ROM"
> 
> Follow the spec definition, the ISO 9660 (and UDF) would be checked before
> the MBR. So it is not required to skip such MBR talbe that contian the entire
> block device.


> 
> Cc: Jian J Wang <jian.j.wang@intel.com>
> Cc: Hao A Wu <hao.a.wu@intel.com>
> Cc: Ray Ni <ray.ni@intel.com>
> Cc: Gary Lin <glin@suse.com>
> Cc: Andrew Fish <afish@apple.com>
> Signed-off-by: Zhichao Gao <zhichao.gao@intel.com>
> ---
>  .../Universal/Disk/PartitionDxe/Mbr.c         | 37 +++----------------
>  1 file changed, 6 insertions(+), 31 deletions(-)
> 
> diff --git a/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c
> b/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c
> index 3830af1ea7..f0c92aa09a 100644
> --- a/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c
> +++ b/MdeModulePkg/Universal/Disk/PartitionDxe/Mbr.c
> @@ -39,7 +39,6 @@ PartitionValidMbr (
>    UINT32  StartingLBA;
>    UINT32  EndingLBA;
>    UINT32  NewEndingLBA;
> -  UINT32  SizeInLBA;
>    INTN    Index1;
>    INTN    Index2;
>    BOOLEAN MbrValid;
> @@ -52,34 +51,13 @@ PartitionValidMbr (
>    //
>    MbrValid = FALSE;
>    for (Index1 = 0; Index1 < MAX_MBR_PARTITIONS; Index1++) {
> -    StartingLBA = UNPACK_UINT32 (Mbr->Partition[Index1].StartingLBA);
> -    SizeInLBA   = UNPACK_UINT32 (Mbr->Partition[Index1].SizeInLBA);
> -
> -    //
> -    // If the MBR with partition entry covering the ENTIRE disk, i.e. start at
> LBA0
> -    // with whole disk size, we treat it as an invalid MBR partition.
> -    //
> -    if ((StartingLBA == 0) &&
> -        (SizeInLBA == (LastLba + 1))) {
> -      //
> -      // Refer to the
> http://manpages.ubuntu.com/manpages/bionic/man8/mkudffs.8.html
> -      // "WHOLE DISK VS PARTITION"
> -      // Some linux ISOs may put the MBR table in the first 512 bytes for
> compatibility reasons with Windows.
> -      // Linux  kernel  ignores MBR table if contains partition which starts at
> sector 0.
> -      // Skip it because we don't have the partition check for UDF(El Torito
> compatible).
> -      // It would continue to do the whole disk check in the UDF routine.
> -      //
> -      DEBUG ((DEBUG_INFO, "PartitionValidMbr: MBR table has partition
> entry covering the ENTIRE disk. Don't treat it as a valid MBR.\n"));
> -
> -      return FALSE;
> -    }
> -
> -    if (Mbr->Partition[Index1].OSIndicator == 0x00 || SizeInLBA == 0) {
> +    if (Mbr->Partition[Index1].OSIndicator == 0x00 || UNPACK_UINT32
> + (Mbr->Partition[Index1].SizeInLBA) == 0) {
>        continue;
>      }
> 
>      MbrValid    = TRUE;
> -    EndingLBA   = StartingLBA + SizeInLBA - 1;
> +    StartingLBA = UNPACK_UINT32 (Mbr->Partition[Index1].StartingLBA);
> +    EndingLBA   = StartingLBA + UNPACK_UINT32 (Mbr-
> >Partition[Index1].SizeInLBA) - 1;
>      if (EndingLBA > LastLba) {
>        //
>        // Compatibility Errata:
> @@ -99,15 +77,12 @@ PartitionValidMbr (
>      }
> 
>      for (Index2 = Index1 + 1; Index2 < MAX_MBR_PARTITIONS; Index2++) {
> -      StartingLBA = UNPACK_UINT32 (Mbr->Partition[Index2].StartingLBA);
> -      SizeInLBA   = UNPACK_UINT32 (Mbr->Partition[Index2].SizeInLBA);
> -
> -      if (Mbr->Partition[Index2].OSIndicator == 0x00 || SizeInLBA == 0) {
> +      if (Mbr->Partition[Index2].OSIndicator == 0x00 || UNPACK_UINT32
> + (Mbr->Partition[Index2].SizeInLBA) == 0) {
>          continue;
>        }
> 
> -      NewEndingLBA = StartingLBA + SizeInLBA - 1;
> -      if (NewEndingLBA >= StartingLBA && StartingLBA <= EndingLBA) {
> +      NewEndingLBA = UNPACK_UINT32 (Mbr->Partition[Index2].StartingLBA)
> + UNPACK_UINT32 (Mbr->Partition[Index2].SizeInLBA) - 1;
> +      if (NewEndingLBA >= StartingLBA && UNPACK_UINT32
> + (Mbr->Partition[Index2].StartingLBA) <= EndingLBA) {
>          //
>          // This region overlaps with the Index1'th region
>          //
> --
> 2.21.0.windows.1
> 
> 
>