[PATCH v1] efi_loader: Handle GD_FLG_SKIP_RELOC

[Ilias Apalodimas]

Hi Varadarajan

On Wed, 26 Mar 2025 at 07:47, Varadarajan Narayanan
<quic_varada at quicinc.com> wrote:
>
> If the EFI runtime services pointers are relocated even though
> relocation is skipped, it corrupts some other data resulting in some
> unexpected behaviour.
>
> In this specific case, it overwrote some page table entries resulting in
> the device memory address range's mappings getting removed. Eventually,
> after the completion of efi_runtime_relocate(), when a driver tries to
> access its device's registers it crashes since the mappings are absent.

How were those page table entries added? The runtime service
relocation might have overwritten those now, but since they are not in
protected memory this can happen arbitrarily.

>
> Signed-off-by: Varadarajan Narayanan <quic_varada at quicinc.com>
> ---
>  common/board_r.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/common/board_r.c b/common/board_r.c
> index 179259b00de..1dd3b96c2de 100644
> --- a/common/board_r.c
> +++ b/common/board_r.c
> @@ -169,7 +169,8 @@ static int initr_reloc_global_data(void)
>          */
>         efi_save_gd();
>
> -       efi_runtime_relocate(gd->relocaddr, NULL);
> +       if (!(gd->flags & GD_FLG_SKIP_RELOC))
> +               efi_runtime_relocate(gd->relocaddr, NULL);

Have you tested booting with EFI with this change?

Thanks
/Ilias
>  #endif
>
>         return 0;
>
> base-commit: 244e61fbb7f5045e4e187024f7ae80434c952145
> --
> 2.34.1
>