Re: [PATCH] efi/loongarch: Reintroduce efi_relocate_kernel() to relocate kernel

[Youling Tang <tangyouling@xxxxxxxxxxx>]

Hi, Huacai

On 03/01/2023 04:55 PM, Huacai Chen wrote:
> Since Linux-6.3, LoongArch supports PIE kernel now, so let's reintroduce
> efi_relocate_kernel() to relocate the core kernel.

If we strongly rely on the PIE feature after the modification, we need
to modify it as follows,

--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -137,6 +137,7 @@ config LOONGARCH
        select PCI_MSI_ARCH_FALLBACKS
        select PCI_QUIRKS
        select PERF_USE_VMALLOC
+       select RELOCATABLE
        select RTC_LIB
        select SMP
        select SPARSE_IRQ

or:

--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig
@@ -360,6 +360,7 @@ config EFI_STUB
        default y
        depends on EFI
        select EFI_GENERIC_STUB
+       select RELOCATABLE
        help

Youling.

> Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx>
> ---
>  drivers/firmware/efi/libstub/loongarch-stub.c | 24 ++++++-------------
>  1 file changed, 7 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/firmware/efi/libstub/loongarch-stub.c b/drivers/firmware/efi/libstub/loongarch-stub.c
> index eee7ed43cdfb..72c71ae201f0 100644
> --- a/drivers/firmware/efi/libstub/loongarch-stub.c
> +++ b/drivers/firmware/efi/libstub/loongarch-stub.c
> @@ -21,26 +21,16 @@ efi_status_t handle_kernel_image(unsigned long *image_addr,
>  				 efi_loaded_image_t *image,
>  				 efi_handle_t image_handle)
>  {
> -	int nr_pages = round_up(kernel_asize, EFI_ALLOC_ALIGN) / EFI_PAGE_SIZE;
> -	efi_physical_addr_t kernel_addr = EFI_KIMG_PREFERRED_ADDRESS;
>  	efi_status_t status;
> +	unsigned long kernel_addr = 0;
>
> -	/*
> -	 * Allocate space for the kernel image at the preferred offset. This is
> -	 * the only location in memory from where we can execute the image, so
> -	 * no point in falling back to another allocation.
> -	 */
> -	status = efi_bs_call(allocate_pages, EFI_ALLOCATE_ADDRESS,
> -			     EFI_LOADER_DATA, nr_pages, &kernel_addr);
> -	if (status != EFI_SUCCESS)
> -		return status;
> -
> -	*image_addr = EFI_KIMG_PREFERRED_ADDRESS;
> -	*image_size = kernel_asize;
> +	kernel_addr = (unsigned long)&kernel_offset - kernel_offset;
> +
> +	status = efi_relocate_kernel(&kernel_addr, kernel_fsize, kernel_asize,
> +		     EFI_KIMG_PREFERRED_ADDRESS, efi_get_kimg_min_align(), 0x0);
>
> -	memcpy((void *)EFI_KIMG_PREFERRED_ADDRESS,
> -	       (void *)&kernel_offset - kernel_offset,
> -	       kernel_fsize);
> +	*image_addr = kernel_addr;
> +	*image_size = kernel_asize;
>
>  	return status;
>  }