Subject: Re: [PATCH] efi/loongarch: Reintroduce efi_relocate_kernel() to
 relocate kernel
To:     Huacai Chen <chenhuacai@loongson.cn>,
        Ard Biesheuvel <ardb@kernel.org>,
        Huacai Chen <chenhuacai@kernel.org>
References: <20230301085545.2373646-1-chenhuacai@loongson.cn>
Cc:     linux-efi@vger.kernel.org, loongarch@lists.linux.dev,
        Xuefeng Li <lixuefeng@loongson.cn>,
        Xuerui Wang <kernel@xen0n.name>, linux-kernel@vger.kernel.org,
        loongson-kernel@lists.loongnix.cn
From:   Youling Tang <tangyouling@loongson.cn>
Message-ID: <aba37b65-6fc4-721e-ebc5-df52533e4791@loongson.cn>
Date:   Wed, 1 Mar 2023 17:20:02 +0800
User-Agent: Mozilla/5.0 (X11; Linux mips64; rv:45.0) Gecko/20100101
 Thunderbird/45.4.0
MIME-Version: 1.0
In-Reply-To: <20230301085545.2373646-1-chenhuacai@loongson.cn>
Content-Type: text/plain; charset=windows-1252; format=flowed
Content-Transfer-Encoding: 7bit
Precedence: bulk

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@loongson.cn>
> ---
>  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;
>  }
>