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

[Youling Tang <tangyouling@xxxxxxxxxxx>]

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@xxxxxxxxxxx> 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@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;
> > >  }