Re: [edk2-devel] [PATCH v1 2/3] OvmfPkg/GenericQemuLoadImageLib: Read cmdline from QemuKernelLoaderFs

["Ard Biesheuvel" <ardb@kernel.org>]

Hello Dov,

On Wed, 9 Jun 2021 at 14:18, Dov Murik <dovmurik@linux.ibm.com> wrote:
>
> Remove the QemuFwCfgLib interface used to read the QEMU cmdline
> (-append argument) and the initrd size.  Instead, use the synthetic
> filesystem QemuKernelLoaderFs which has three files: "kernel", "initrd",
> and "cmdline".
>
> Cc: Laszlo Ersek <lersek@redhat.com>
> Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
> Cc: Jordan Justen <jordan.l.justen@intel.com>
> Cc: James Bottomley <jejb@linux.ibm.com>
> Cc: Tobin Feldman-Fitzthum <tobin@linux.ibm.com>
> Signed-off-by: Dov Murik <dovmurik@linux.ibm.com>
> ---
>  OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf |   2 +-
>  OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.c   | 132 ++++++++++++++++++--
>  2 files changed, 126 insertions(+), 8 deletions(-)
>
> diff --git a/OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf b/OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
> index b262cb926a4d..f462fd6922cf 100644
> --- a/OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
> +++ b/OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.inf
> @@ -27,12 +27,12 @@ [LibraryClasses]
>    DebugLib
>    MemoryAllocationLib
>    PrintLib
> -  QemuFwCfgLib
>    UefiBootServicesTableLib
>
>  [Protocols]
>    gEfiDevicePathProtocolGuid
>    gEfiLoadedImageProtocolGuid
> +  gEfiSimpleFileSystemProtocolGuid
>
>  [Guids]
>    gQemuKernelLoaderFsMediaGuid
> diff --git a/OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.c b/OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.c
> index 114db7e8441f..7d26c912e14f 100644
> --- a/OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.c
> +++ b/OvmfPkg/Library/GenericQemuLoadImageLib/GenericQemuLoadImageLib.c
> @@ -11,9 +11,9 @@
>  #include <Base.h>
>  #include <Guid/QemuKernelLoaderFsMedia.h>
>  #include <Library/DebugLib.h>
> +#include <Library/FileHandleLib.h>
>  #include <Library/MemoryAllocationLib.h>
>  #include <Library/PrintLib.h>
> -#include <Library/QemuFwCfgLib.h>
>  #include <Library/QemuLoadImageLib.h>
>  #include <Library/UefiBootServicesTableLib.h>
>  #include <Protocol/DevicePath.h>
> @@ -30,6 +30,11 @@ typedef struct {
>    KERNEL_FILE_DEVPATH       FileNode;
>    EFI_DEVICE_PATH_PROTOCOL  EndNode;
>  } KERNEL_VENMEDIA_FILE_DEVPATH;
> +
> +typedef struct {
> +  VENDOR_DEVICE_PATH       VenMediaNode;
> +  EFI_DEVICE_PATH_PROTOCOL EndNode;
> +} SINGLE_VENMEDIA_NODE_DEVPATH;
>  #pragma pack ()
>
>  STATIC CONST KERNEL_VENMEDIA_FILE_DEVPATH mKernelDevicePath = {
> @@ -51,6 +56,78 @@ STATIC CONST KERNEL_VENMEDIA_FILE_DEVPATH mKernelDevicePath = {
>    }
>  };
>
> +STATIC CONST SINGLE_VENMEDIA_NODE_DEVPATH mQemuKernelLoaderFileSystemDevicePath = {
> +  {
> +    {
> +      MEDIA_DEVICE_PATH, MEDIA_VENDOR_DP,
> +      { sizeof (VENDOR_DEVICE_PATH) }
> +    },
> +    QEMU_KERNEL_LOADER_FS_MEDIA_GUID
> +  }, {
> +    END_DEVICE_PATH_TYPE, END_ENTIRE_DEVICE_PATH_SUBTYPE,
> +    { sizeof (EFI_DEVICE_PATH_PROTOCOL) }
> +  }
> +};
> +
> +STATIC
> +EFI_STATUS
> +GetQemuKernelBlobSize (

Could we please use a better name here? 'QemuKernel' is confusing as
it is used for initrd and cmdline only, in this case, right?

'QemuKernelLoader' is better in this regard, or other suggestions
welcome as well.


> +  IN  EFI_FILE_HANDLE     Root,
> +  IN  CHAR16              *FileName,
> +  OUT UINTN               *Size
> +  )
> +{
> +  EFI_STATUS      Status;
> +  EFI_FILE_HANDLE FileHandle;
> +  UINT64          FileSize;
> +
> +  Status = Root->Open (Root, &FileHandle, FileName, EFI_FILE_MODE_READ, 0);
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
> +  Status = FileHandleGetSize (FileHandle, &FileSize);
> +  if (EFI_ERROR (Status)) {
> +    goto CloseFile;
> +  }
> +  *Size = FileSize;
> +  Status = EFI_SUCCESS;
> +CloseFile:
> +  FileHandle->Close (FileHandle);
> +  return Status;
> +}
> +
> +STATIC
> +EFI_STATUS
> +ReadWholeQemuKernelBlob (
> +  IN  EFI_FILE_HANDLE     Root,
> +  IN  CHAR16              *FileName,
> +  IN  UINTN               Size,
> +  OUT VOID                *Buffer
> +  )
> +{
> +  EFI_STATUS      Status;
> +  EFI_FILE_HANDLE FileHandle;
> +  UINTN           ReadSize;
> +
> +  Status = Root->Open (Root, &FileHandle, FileName, EFI_FILE_MODE_READ, 0);
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
> +  ReadSize = Size;
> +  Status = FileHandle->Read (FileHandle, &ReadSize, Buffer);
> +  if (EFI_ERROR (Status)) {
> +    goto CloseFile;
> +  }
> +  if (ReadSize != Size) {
> +    Status = EFI_PROTOCOL_ERROR;
> +    goto CloseFile;
> +  }
> +  Status = EFI_SUCCESS;
> +CloseFile:
> +  FileHandle->Close (FileHandle);
> +  return Status;
> +}
> +
>  /**
>    Download the kernel, the initial ramdisk, and the kernel command line from
>    QEMU's fw_cfg. The kernel will be instructed via its command line to load
> @@ -79,6 +156,10 @@ QemuLoadKernelImage (
>    EFI_STATUS                Status;
>    EFI_HANDLE                KernelImageHandle;
>    EFI_LOADED_IMAGE_PROTOCOL *KernelLoadedImage;
> +  EFI_DEVICE_PATH_PROTOCOL  *DevicePathNode;
> +  EFI_HANDLE                FsVolumeHandle;
> +  EFI_SIMPLE_FILE_SYSTEM_PROTOCOL *FsProtocol;

Slightly tedious, but better to reindent the whole block.

> +  EFI_FILE_HANDLE           Root;
>    UINTN                     CommandLineSize;
>    CHAR8                     *CommandLine;
>    UINTN                     InitrdSize;
> @@ -124,8 +205,38 @@ QemuLoadKernelImage (
>                    );
>    ASSERT_EFI_ERROR (Status);
>
> -  QemuFwCfgSelectItem (QemuFwCfgItemCommandLineSize);
> -  CommandLineSize = (UINTN)QemuFwCfgRead32 ();
> +  //
> +  // Open the Qemu Kernel Loader abstract filesystem (volume) which will be
> +  // used to read the "initrd" and "cmdline" synthetic files.
> +  //
> +  DevicePathNode = (EFI_DEVICE_PATH_PROTOCOL *) &mQemuKernelLoaderFileSystemDevicePath;

No space between cast type and castee please.

> +  Status = gBS->LocateDevicePath (
> +                  &gEfiSimpleFileSystemProtocolGuid,
> +                  &DevicePathNode,
> +                  &FsVolumeHandle
> +                  );
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
> +
> +  Status = gBS->HandleProtocol (
> +                  FsVolumeHandle,
> +                  &gEfiSimpleFileSystemProtocolGuid,
> +                  (VOID **)&FsProtocol
> +                  );
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
> +
> +  Status = FsProtocol->OpenVolume (FsVolumeHandle, &Root);
> +  if (EFI_ERROR (Status)) {
> +    return Status;
> +  }
> +
> +  Status = GetQemuKernelBlobSize (Root, L"cmdline", &CommandLineSize);
> +  if (EFI_ERROR (Status)) {
> +    goto CloseRoot;
> +  }
>
>    if (CommandLineSize == 0) {
>      KernelLoadedImage->LoadOptionsSize = 0;
> @@ -136,8 +247,10 @@ QemuLoadKernelImage (
>        goto UnloadImage;
>      }
>
> -    QemuFwCfgSelectItem (QemuFwCfgItemCommandLineData);
> -    QemuFwCfgReadBytes (CommandLineSize, CommandLine);
> +    Status = ReadWholeQemuKernelBlob (Root, L"cmdline", CommandLineSize, CommandLine);
> +    if (EFI_ERROR (Status)) {
> +      goto FreeCommandLine;
> +    }
>
>      //
>      // Verify NUL-termination of the command line.
> @@ -155,8 +268,10 @@ QemuLoadKernelImage (
>      KernelLoadedImage->LoadOptionsSize = (UINT32)((CommandLineSize - 1) * 2);
>    }
>
> -  QemuFwCfgSelectItem (QemuFwCfgItemInitrdSize);
> -  InitrdSize = (UINTN)QemuFwCfgRead32 ();
> +  Status = GetQemuKernelBlobSize (Root, L"initrd", &InitrdSize);
> +  if (EFI_ERROR (Status)) {
> +    goto FreeCommandLine;
> +  }
>
>    if (InitrdSize > 0) {
>      //
> @@ -193,6 +308,7 @@ QemuLoadKernelImage (
>    }
>
>    *ImageHandle = KernelImageHandle;
> +  Root->Close (Root);
>    return EFI_SUCCESS;
>
>  FreeCommandLine:
> @@ -201,6 +317,8 @@ FreeCommandLine:
>    }
>  UnloadImage:
>    gBS->UnloadImage (KernelImageHandle);
> +CloseRoot:
> +  Root->Close (Root);
>
>    return Status;
>  }
> --
> 2.25.1
>
>
>
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