Re: [PATCH 1/1] riscv: efi: Set NX compat flag in PE/COFF header

[Alexandre Ghiti]

Hi Heinrich,

On 29/09/2024 16:02, Heinrich Schuchardt wrote:
> The IMAGE_DLLCHARACTERISTICS_NX_COMPAT informs the firmware that the
> EFI binary does not rely on pages that are both executable and
> writable.
>
> The flag is used by some distro versions of GRUB to decide if the EFI
> binary may be executed.
>
> As the Linux kernel neither has RWX sections nor needs RWX pages for
> relocation we should set the flag.
>
> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@xxxxxxxxxxxxx>
> ---
>   arch/riscv/kernel/efi-header.S | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/riscv/kernel/efi-header.S b/arch/riscv/kernel/efi-header.S
> index 515b2dfbca75..c5f17c2710b5 100644
> --- a/arch/riscv/kernel/efi-header.S
> +++ b/arch/riscv/kernel/efi-header.S
> @@ -64,7 +64,7 @@ extra_header_fields:
>   	.long	efi_header_end - _start			// SizeOfHeaders
>   	.long	0					// CheckSum
>   	.short	IMAGE_SUBSYSTEM_EFI_APPLICATION		// Subsystem
> -	.short	0					// DllCharacteristics
> +	.short	IMAGE_DLL_CHARACTERISTICS_NX_COMPAT	// DllCharacteristics
>   	.quad	0					// SizeOfStackReserve
>   	.quad	0					// SizeOfStackCommit
>   	.quad	0					// SizeOfHeapReserve


I don't understand if this fixes something or not: what could go wrong 
if we don't do this?

Thanks,

Alex