On Wed, 26 Feb 2020 at 20:43, Ard Biesheuvel <ard.biesheu...@linaro.org> wrote:
>
> EDK2's implementation of the LoadImage() boot service permits non-native
> binaries to be loaded (i.e., X64 images on IA32 firmware), but any
> attempts to start such an image using StartImage() will return
> EFI_UNSUPPORTED.
>
> The integration of the PE/COFF emulator protocol into the DXE core
> deviates slightly from this paradigm, given that its IsImageSupported
> hook as well as its RegisterImage hook are invoked from LoadImage,
> and by the time StartImage is called, no opportunity is given to the
> provider of the PE/COFF emulator protocol to prevent an image from
> being started if it only supports loading it.
>
> To address this disparity, let's move the invocation of RegisterImage()
> to the implementation of the StartImage() boot service, allowing the
> emulator to permit LoadImage() but reject StartImage() on images that
> turn out not to meet the requirements of the emulator as it is being
> started.
>
> Signed-off-by: Ard Biesheuvel <ard.biesheu...@linaro.org>
@MdeModulePkg maintainers: do you have any comments on this patch?
> ---
> MdeModulePkg/Core/Dxe/Image/Image.c | 24 +++++++++++---------
> 1 file changed, 13 insertions(+), 11 deletions(-)
>
> diff --git a/MdeModulePkg/Core/Dxe/Image/Image.c
> b/MdeModulePkg/Core/Dxe/Image/Image.c
> index 22a87ecf6d7c..d86da89ee704 100644
> --- a/MdeModulePkg/Core/Dxe/Image/Image.c
> +++ b/MdeModulePkg/Core/Dxe/Image/Image.c
> @@ -756,17 +756,6 @@ CoreLoadPeImage (
> // Get the image entry point.
> //
> Image->EntryPoint =
> (EFI_IMAGE_ENTRY_POINT)(UINTN)Image->ImageContext.EntryPoint;
> - if (Image->PeCoffEmu != NULL) {
> - Status = Image->PeCoffEmu->RegisterImage (Image->PeCoffEmu,
> - Image->ImageBasePage,
> - EFI_PAGES_TO_SIZE (Image->NumberOfPages),
> - &Image->EntryPoint);
> - if (EFI_ERROR (Status)) {
> - DEBUG ((DEBUG_LOAD | DEBUG_ERROR,
> - "CoreLoadPeImage: Failed to register foreign image with
> emulator.\n"));
> - goto Done;
> - }
> - }
>
> //
> // Fill in the image information for the Loaded Image Protocol
> @@ -1603,6 +1592,19 @@ CoreStartImage (
> return EFI_UNSUPPORTED;
> }
>
> + if (Image->PeCoffEmu != NULL) {
> + Status = Image->PeCoffEmu->RegisterImage (Image->PeCoffEmu,
> + Image->ImageBasePage,
> + EFI_PAGES_TO_SIZE (Image->NumberOfPages),
> + &Image->EntryPoint);
> + if (EFI_ERROR (Status)) {
> + DEBUG ((DEBUG_LOAD | DEBUG_ERROR,
> + "CoreLoadPeImage: Failed to register foreign image with emulator -
> %r\n",
> + Status));
> + return Status;
> + }
> + }
> +
> PERF_START_IMAGE_BEGIN (Handle);
>
>
> --
> 2.17.1
>
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