Re: [PATCH v4 2/2] mkimage: Align efi sections on 4k boundary

[Daniel Kiper]

On Wed, Jan 23, 2019 at 04:34:58PM +0100, Alexander Graf wrote:
> There is UEFI firmware popping up in the wild now that implements stricter
> permission checks using NX and write protect page table entry bits.
>
> This means that firmware now may fail to load binaries if its individual
> sections are not page aligned, as otherwise it can not ensure permission
> boundaries.
>
> So let's bump all efi section alignments up to 4k (EFI page size). That way
> we will stay compatible going forward.
>
> Unfortunately our internals can't deal very well with a mismatch of alignment
> between the virtual and file offsets, so we have to also pad our target
> binary a bit.
>
> Signed-off-by: Alexander Graf <address@hidden>
> ---
>  include/grub/efi/pe32.h | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/include/grub/efi/pe32.h b/include/grub/efi/pe32.h
> index 7d44732d2..52ff208c0 100644
> --- a/include/grub/efi/pe32.h
> +++ b/include/grub/efi/pe32.h
> @@ -50,8 +50,13 @@
>  /* According to the spec, the minimal alignment is 512 bytes...
>     But some examples (such as EFI drivers in the Intel
>     Sample Implementation) use 32 bytes (0x20) instead, and it seems
> -   to be working. For now, GRUB uses 512 bytes for safety.  */
> -#define GRUB_PE32_SECTION_ALIGNMENT  0x200
> +   to be working.
> +
> +   However, there is firmware showing up in the field now with
> +   page alignment constraints to guarantee that page protection
> +   bits take effect. Because we can not easily distinguish between
> +   in-memory and in-file layout, let's bump all alignment to 4k. */

s/4k/GRUB_EFI_PAGE_SIZE/

> +#define GRUB_PE32_SECTION_ALIGNMENT  0x1000

I think that this should be:

#define GRUB_PE32_SECTION_ALIGNMENT GRUB_EFI_PAGE_SIZE

And I still miss two patches. One replacing GRUB_PE32_SECTION_ALIGNMENT
with GRUB_PE32_FILE_ALIGNMENT in EFI32_HEADER_SIZE and EFI64_HEADER_SIZE
macros.

And another for some code in the util/mkimage.c...

        reloc_addr = ALIGN_UP (header_size + core_size,
                               GRUB_PE32_FILE_ALIGNMENT);

        pe_size = ALIGN_UP (reloc_addr + layout.reloc_size,
                            GRUB_PE32_FILE_ALIGNMENT);

...plus...

        o->file_alignment = grub_host_to_target32 (GRUB_PE32_FILE_ALIGNMENT);

Daniel