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From: Gary Lin <glin@suse.com>
To: Laszlo Ersek <lersek@redhat.com>
Cc: edk2-devel@lists.01.org, Ruiyu Ni <ruiyu.ni@intel.com>,
	Hao Wu <hao.a.wu@intel.com>, Star Zeng <star.zeng@intel.com>
Subject: Re: [PATCH] MdeModulePkg/UefiBootManagerLib: Match the nested partitions
Date: Wed, 16 Jan 2019 10:16:01 +0800	[thread overview]
Message-ID: <20190116021601.GI3972@GaryWorkstation> (raw)
In-Reply-To: <9497b88c-7025-e3bc-8f69-0a20a550930a@redhat.com>

On Tue, Jan 15, 2019 at 12:58:10PM +0100, Laszlo Ersek wrote:
> On 01/15/19 10:45, Gary Lin wrote:
> > In some cases, such as MD RAID1 in Linux, the bootloader may be in a
> > nested EFI system partition partition. For example, sda1 and sdb1 are
> > combined as md0 and the first partition of md0, md0p1, is an EFI system
> > partition. Then, the bootloader can be located by the following device
> > paths:
> > 
> > PCI()/SATA(sda)/Partition(sda1)/Partition(md0p1)/File(bootloader.efi)
> > PCI()/SATA(sdb)/Partition(sdb1)/Partition(md0p1)/File(bootloader.efi)
> 
> How does edk2 recognize the nested partition md0p1 in the first place?
> 
> I would assume that the "outer" partitions (sda1, sdb1) start with some
> kind of MD RAID1 header that allows Linux to combine sda1 and sdb1 into
> md0p1. How does edk2 get past that header?
> 
> Hmmm... based on
> <https://raid.wiki.kernel.org/index.php/RAID_superblock_formats>, does
> Linux use "footers" instead of "headers"?
> 
See the "Sub-versions of the version-1 superblock" section:
<https://raid.wiki.kernel.org/index.php/RAID_superblock_formats#Sub-versions_of_the_version-1_superblock>

For MD 0.9 and 1.0, the metadata is stored in the end of the disk, and
those partitions, nested or not, are just like the normal partitions, so
the firmare can see them without the knowledge of MD metadata. MD 1.1
and 1.2 would be a different story because those two use "headers".

Anyway, I have tested RAID1 with MD 1.0 and OVMF actually appended md0p1
in the device path. I only need to iterate the nested partitions in the
match function to make my boot option work.

Thanks,

Gary Lin

> Thanks,
> Laszlo
> 
> > 
> > To make the boot option more resilient, we may create a boot option with
> > the short-form device path like "Partition(md0p1)/File(bootloader.efi)".
> > 
> > However, BmMatchPartitionDevicePathNode() only matched the first
> > partition node and ignored the nested partitions, so the firmware would
> > refuse to load bootloader.efi since "Partition(md0p1)" doesn't match
> > either "Partition(sda1)" or "Partition(sda2)".
> > 
> > This commit modifies BmMatchPartitionDevicePathNode() to iterate all
> > nested partitions so that the above boot option could work.
> > 
> > Cc: Ruiyu Ni <ruiyu.ni@intel.com>
> > Cc: Star Zeng <star.zeng@intel.com>
> > Cc: Jian J Wang <jian.j.wang@intel.com>
> > Cc: Hao Wu <hao.a.wu@intel.com>
> > Contributed-under: TianoCore Contribution Agreement 1.1
> > Signed-off-by: Gary Lin <glin@suse.com>
> > ---
> >  .../Library/UefiBootManagerLib/BmBoot.c       | 37 ++++++++++++-------
> >  1 file changed, 23 insertions(+), 14 deletions(-)
> > 
> > diff --git a/MdeModulePkg/Library/UefiBootManagerLib/BmBoot.c b/MdeModulePkg/Library/UefiBootManagerLib/BmBoot.c
> > index 6a23477eb873..8354c2af674b 100644
> > --- a/MdeModulePkg/Library/UefiBootManagerLib/BmBoot.c
> > +++ b/MdeModulePkg/Library/UefiBootManagerLib/BmBoot.c
> > @@ -1995,21 +1995,30 @@ BmMatchPartitionDevicePathNode (
> >      return FALSE;
> >    }
> >  
> > -  //
> > -  // See if the harddrive device path in blockio matches the orig Hard Drive Node
> > -  //
> > -  Node = (HARDDRIVE_DEVICE_PATH *) BlockIoDevicePath;
> > +  do {
> > +    //
> > +    // See if the harddrive device path in blockio matches the orig Hard Drive Node
> > +    //
> > +    Node = (HARDDRIVE_DEVICE_PATH *) BlockIoDevicePath;
> >  
> > -  //
> > -  // Match Signature and PartitionNumber.
> > -  // Unused bytes in Signature are initiaized with zeros.
> > -  //
> > -  return (BOOLEAN) (
> > -    (Node->PartitionNumber == HardDriveDevicePath->PartitionNumber) &&
> > -    (Node->MBRType == HardDriveDevicePath->MBRType) &&
> > -    (Node->SignatureType == HardDriveDevicePath->SignatureType) &&
> > -    (CompareMem (Node->Signature, HardDriveDevicePath->Signature, sizeof (Node->Signature)) == 0)
> > -    );
> > +    //
> > +    // Match Signature and PartitionNumber.
> > +    // Unused bytes in Signature are initiaized with zeros.
> > +    //
> > +    if ((Node->PartitionNumber == HardDriveDevicePath->PartitionNumber) &&
> > +        (Node->MBRType == HardDriveDevicePath->MBRType) &&
> > +        (Node->SignatureType == HardDriveDevicePath->SignatureType) &&
> > +        (CompareMem (Node->Signature, HardDriveDevicePath->Signature, sizeof (Node->Signature)) == 0)) {
> > +      return TRUE;
> > +    }
> > +
> > +    // See if a nested partition exists
> > +    BlockIoDevicePath = NextDevicePathNode (BlockIoDevicePath);
> > +  } while (!IsDevicePathEnd (BlockIoDevicePath) &&
> > +           (DevicePathType (BlockIoDevicePath) == MEDIA_DEVICE_PATH) &&
> > +           (DevicePathSubType (BlockIoDevicePath) == MEDIA_HARDDRIVE_DP));
> > +
> > +  return FALSE;
> >  }
> >  
> >  /**
> > 
> 
> _______________________________________________
> edk2-devel mailing list
> edk2-devel@lists.01.org
> https://lists.01.org/mailman/listinfo/edk2-devel
> 


  reply	other threads:[~2019-01-16  2:16 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-15  9:45 [PATCH] MdeModulePkg/UefiBootManagerLib: Match the nested partitions Gary Lin
2019-01-15 11:58 ` Laszlo Ersek
2019-01-16  2:16   ` Gary Lin [this message]
2019-01-16  9:02     ` Laszlo Ersek
2019-01-22 16:01 ` Ni, Ray
2019-01-23  2:12   ` Gary Lin
2019-01-23  3:48     ` Ni, Ray
2019-01-23  3:49       ` Ni, Ray
2019-01-23  4:02         ` Gary Lin

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