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

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Date:   Wed, 1 Mar 2023 20:06:57 +0800
From:   Huacai Chen <chenhuacai@...nel.org>
To:     Youling Tang <tangyouling@...ngson.cn>
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, Youling,

On Wed, Mar 1, 2023 at 6:08 PM Youling Tang <tangyouling@...ngson.cn> wrote:
>
> 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
We can select RELOCATABLE when we modify EFI_KIMG_PREFERRED_ADDRESS.
Before that I prefer to give a chance to build a non-PIE kernel.

Huacai
>
> 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;
> >>>  }
> >>>
> >>
>
>