[PATCH] efi: Make FDT extra space configurable

[Ilias Apalodimas]

On Mon, 10 Feb 2025 at 18:07, Pawel Kochanowski <pkochanowski at sii.pl> wrote:
>
> From: Gabriel Nesteruk <gnesteruk at sii.pl>
>
> U-Boot currently reserves only 0x3000 bytes when copying the FDT
> in `copy_fdt()`, which may not be sufficient if additional nodes
> (such as FMAN firmware) are added later.
>
> This patch introduces a new `CONFIG_FDT_EXTRA_SPACE` Kconfig option
> to allow users to define the amount of extra space reserved for FDT
> expansion. The default remains 0x3000.
>
> This change prevents potential corruption when resizing FDT after
> EFI boot, especially when firmware like FMAN requires additional
> space.
>
> Signed-off-by: Gabriel Nesteruk <gnesteruk at sii.pl>
> Signed-off-by: Pawel Kochanowski <pkochanowski at sii.pl>
> ---
>  lib/efi_loader/Kconfig      | 9 +++++++++
>  lib/efi_loader/efi_helper.c | 2 +-
>  2 files changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/lib/efi_loader/Kconfig b/lib/efi_loader/Kconfig
> index d4f6b56afaa..bd2cbe995c9 100644
> --- a/lib/efi_loader/Kconfig
> +++ b/lib/efi_loader/Kconfig
> @@ -586,6 +586,15 @@ config BOOTEFI_TESTAPP_COMPILE
>           No additional space will be required in the resulting U-Boot binary
>           when this option is enabled.
>
> +config EFI_FDT_EXTRA_SPACE
> +    hex "Extra space to allocate for FDT expansion"
> +    default 0x3000
> +    help
> +      Defines additional space (in bytes) reserved for expanding the
> +      Flattened Device Tree (FDT) when passed to the EFI system.
> +      Increase this value if your firmware (e.g., FMAN) needs to add
> +      more data to the device tree after U-Boot relocation.
> +
>  endif
>
>  source "lib/efi/Kconfig"
> diff --git a/lib/efi_loader/efi_helper.c b/lib/efi_loader/efi_helper.c
> index 04b2efc4a3b..91b2a5b8653 100644
> --- a/lib/efi_loader/efi_helper.c
> +++ b/lib/efi_loader/efi_helper.c
> @@ -477,7 +477,7 @@ static efi_status_t copy_fdt(void **fdtp)
>          * needs to be expanded later.
>          */
>         fdt = *fdtp;
> -       fdt_pages = efi_size_in_pages(fdt_totalsize(fdt) + 0x3000);
> +       fdt_pages = efi_size_in_pages(fdt_totalsize(fdt) + CONFIG_EFI_FDT_EXTRA_SPACE);
>         fdt_size = fdt_pages << EFI_PAGE_SHIFT;
>
>         ret = efi_allocate_pages(EFI_ALLOCATE_ANY_PAGES,
> --
> 2.43.0
>

Reviewed-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>