linux-kernel - Re: [PATCH] efi/loongarch: Reintroduce efi_relocate

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Date:   Wed, 1 Mar 2023 18:07:53 +0800
From:   Youling Tang <tangyouling@...ngson.cn>
To:     Huacai Chen <chenhuacai@...nel.org>
Cc:     Huacai Chen <chenhuacai@...ngson.cn>,
        Ard Biesheuvel <ardb@...nel.org>, linux-efi@...r.kernel.org,
        loongarch@...ts.linux.dev, Xuefeng Li <lixuefeng@...ngson.cn>,
        Xuerui Wang <kernel@...0n.name>, linux-kernel@...r.kernel.org,
        loongson-kernel@...ts.loongnix.cn
Subject: Re: [PATCH] efi/loongarch: Reintroduce efi_relocate_kernel() to
 relocate kernel

Hi, Huacai

On 03/01/2023 05:30 PM, Huacai Chen wrote:
> Hi, Youling,
>
> On Wed, Mar 1, 2023 at 5:21 PM Youling Tang <tangyouling@...ngson.cn> wrote:
>>
>> 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,
> There is no strong rely, efi_relocate_kernel() can also handle the
> non-PIE kernel.

IMHO, if EFI_KIMG_PREFERRED_ADDRESS is no longer defined as
`PHYSADDR(VMLINUX_LOAD_ADDRESS)` (physical link address), we need to
relocate through the RELOCATABLE function, so it is recommended to
select RELOCATABLE if EFI_STUB is enabled

Youling.
>
> Huacai
>>
>> --- 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@...ngson.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;
>>>  }
>>>
>>