Re: [edk2-devel] [PATCH 1/2] Ext4Pkg: Improve Binding support behavior

["Marvin Häuser" <mhaeuser@posteo.de>]

Good day,

On 09/09/2021 22:41, Jeff Brasen via groups.io wrote:
> A couple improvements to improve performance.
> Add check to return ACCESS_DENIED if already connected

This "performance improvement" actually aligns the load behaviour with 
the UEFI spec, maybe it should be mentioned?

> Add check to verify superblock magic during supported to deduce start calls
>
> Signed-off-by: Jeff Brasen <jbrasen@nvidia.com>
> ---
>   Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h    | 14 +++++++
>   Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.c    | 57 +++++++++++++++++++++------
>   Features/Ext4Pkg/Ext4Dxe/Superblock.c | 34 ++++++++++++++++
>   3 files changed, 92 insertions(+), 13 deletions(-)
>
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> index 64eab455db..9a3938e671 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> @@ -1117,4 +1117,18 @@ Ext4GetVolumeName (
>     OUT UINTN          *VolNameLen
>     );
>   
> +/**
> +   Checks only superblock magic value.
> +
> +   @param[in] DiskIo     Pointer to the DiskIo.
> +   @param[in] BlockIo     Pointer to the BlockIo.
> +
> +   @return TRUE if a valid ext4 superblock, else FALSE.
> +**/
> +BOOLEAN
> +Ext4SuperblockCheckMagic (
> +  IN EFI_DISK_IO_PROTOCOL  *DiskIo,
> +  IN EFI_BLOCK_IO_PROTOCOL *BlockIo
> +  );
> +
>   #endif
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.c b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.c
> index ea2e048d77..cb1e6d532a 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.c
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.c
> @@ -631,7 +631,6 @@ Ext4Unload (
>     @retval EFI_ACCESS_DENIED        The device specified by ControllerHandle and
>                                      RemainingDevicePath is already being managed by a different
>                                      driver or an application that requires exclusive access.
> -                                   Currently not implemented.
>     @retval EFI_UNSUPPORTED          The device specified by ControllerHandle and
>                                      RemainingDevicePath is not supported by the driver specified by This.
>   **/
> @@ -643,32 +642,64 @@ Ext4IsBindingSupported (
>     IN EFI_DEVICE_PATH *RemainingDevicePath  OPTIONAL
>     )
>   {
> -  // Note to self: EFI_OPEN_PROTOCOL_TEST_PROTOCOL lets us not close the
> -  // protocol and ignore the output argument entirely
> -
> -  EFI_STATUS  Status;
> +  EFI_STATUS            Status;
> +  EFI_DISK_IO_PROTOCOL  *DiskIo = NULL;
> +  EFI_BLOCK_IO_PROTOCOL *BlockIo = NULL;
>   
> +  //
> +  // Open the IO Abstraction(s) needed to perform the supported test
> +  //
>     Status = gBS->OpenProtocol (
>                     ControllerHandle,
>                     &gEfiDiskIoProtocolGuid,
> -                  NULL,
> -                  BindingProtocol->ImageHandle,
> +                  (VOID **) &DiskIo,
> +                  BindingProtocol->DriverBindingHandle,
>                     ControllerHandle,
> -                  EFI_OPEN_PROTOCOL_TEST_PROTOCOL
> +                  EFI_OPEN_PROTOCOL_BY_DRIVER
>                     );
>   
>     if (EFI_ERROR (Status)) {
> -    return Status;
> +    goto Exit;

This change is not required as nothing was opened on failure; see below.

>     }
> -
> +  //
> +  // Open the IO Abstraction(s) needed to perform the supported test
> +  //
>     Status = gBS->OpenProtocol (
>                     ControllerHandle,
>                     &gEfiBlockIoProtocolGuid,
> -                  NULL,
> -                  BindingProtocol->ImageHandle,
> +                  (VOID **) &BlockIo,
> +                  BindingProtocol->DriverBindingHandle,
>                     ControllerHandle,
> -                  EFI_OPEN_PROTOCOL_TEST_PROTOCOL
> +                  EFI_OPEN_PROTOCOL_GET_PROTOCOL

Why do the open modes mismatch if both protocols are equally stored in 
the private partition data? Is the owner of Block I/O a different one 
than the one of Disk I/O?

>                     );
> +  if (EFI_ERROR (Status)) {
> +    goto Exit;
> +  }
> +
> +  if (!Ext4SuperblockCheckMagic (DiskIo, BlockIo)) {
> +    Status = EFI_UNSUPPORTED;
> +  }

This can easily be rewritten to not require "goto":

   if (!EFI_ERROR (Status) && !Ext4SuperblockCheckMagic (DiskIo, BlockIo)) {
     Status = EFI_UNSUPPORTED;
   }

With the change above this allows to drop the label and any "goto" code.

> +
> +Exit:
> +  //
> +  // Close the I/O Abstraction(s) used to perform the supported test
> +  //
> +  if (DiskIo != NULL) {
> +    gBS->CloseProtocol (
> +          ControllerHandle,
> +          &gEfiDiskIoProtocolGuid,
> +          BindingProtocol->DriverBindingHandle,
> +          ControllerHandle
> +          );
> +  }
> +  if (BlockIo != NULL) {
> +    gBS->CloseProtocol (
> +          ControllerHandle,
> +          &gEfiBlockIoProtocolGuid,
> +          BindingProtocol->DriverBindingHandle,
> +          ControllerHandle
> +          );
> +  }

Protocols retrieved by GET_PROTOCOL are not closed.

>     return Status;
>   }
>   
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Superblock.c b/Features/Ext4Pkg/Ext4Dxe/Superblock.c
> index c321d8c3d8..1f8cdd3705 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Superblock.c
> +++ b/Features/Ext4Pkg/Ext4Dxe/Superblock.c
> @@ -34,6 +34,40 @@ STATIC CONST UINT32  gSupportedIncompatFeat =
>   // this is desired, it's fairly trivial to look for EFI_VOLUME_CORRUPTED
>   // references and add some Ext4SignalCorruption function + function call.
>   
> +/**
> +   Checks only superblock magic value.

Whether it "only" checks the magic is more of a functional detail than 
an actual description.

> +
> +   @param[in] DiskIo     Pointer to the DiskIo.
> +   @param[in] BlockIo     Pointer to the BlockIo.
> +
> +   @return TRUE if a valid ext4 superblock, else FALSE.

Maybe use "@returns  Whether the partition has a valid EXT4 superblock 
magic" for readability?

Best regards,
Marvin

> +**/
> +BOOLEAN
> +Ext4SuperblockCheckMagic (
> +  IN EFI_DISK_IO_PROTOCOL  *DiskIo,
> +  IN EFI_BLOCK_IO_PROTOCOL *BlockIo
> +  )
> +{
> +  UINT16      Magic;
> +  EFI_STATUS Status;
> +
> +  Status = DiskIo->ReadDisk (DiskIo,
> +                             BlockIo->Media->MediaId,
> +                             EXT4_SUPERBLOCK_OFFSET + OFFSET_OF (EXT4_SUPERBLOCK, s_magic),
> +                             sizeof (Magic),
> +                             &Magic
> +                             );
> +  if (EFI_ERROR (Status)) {
> +    return FALSE;
> +  }
> +
> +  if (Magic != EXT4_SIGNATURE) {
> +    return FALSE;
> +  }
> +
> +  return TRUE;
> +}
> +
>   /**
>      Does brief validation of the ext4 superblock.
>