Re: [PATCH v3 3/4] LoongArch: Fix entry point in image header

[WANG Rui]

On Thu, May 23, 2024 at 6:03 AM Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx> wrote:
>
> Currently kernel entry in head.S is in DMW address range,
> firmware is instructed to jump to this address after loading
> the image.
>
> However kernel should not make any assumption on firmware's
> DMW setting, thus the entry point should be a physical address
> falls into direct translation region.
>
> Fix by converting entry address to physical and amend entry
> calculation logic in libstub accordingly.
>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Jiaxun Yang <jiaxun.yang@xxxxxxxxxxx>
> ---
> v2: Fix efistub
> v3: Move calculation to linker script
> ---
>  arch/loongarch/kernel/head.S             | 2 +-
>  arch/loongarch/kernel/vmlinux.lds.S      | 2 ++
>  drivers/firmware/efi/libstub/loongarch.c | 2 +-
>  3 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/arch/loongarch/kernel/head.S b/arch/loongarch/kernel/head.S
> index c4f7de2e2805..2cdc1ea808d9 100644
> --- a/arch/loongarch/kernel/head.S
> +++ b/arch/loongarch/kernel/head.S
> @@ -22,7 +22,7 @@
>  _head:
>         .word   MZ_MAGIC                /* "MZ", MS-DOS header */
>         .org    0x8
> -       .dword  kernel_entry            /* Kernel entry point */
> +       .dword  _kernel_entry_phys      /* Kernel entry point (physical address) */
>         .dword  _kernel_asize           /* Kernel image effective size */
>         .quad   PHYS_LINK_KADDR         /* Kernel image load offset from start of RAM */
>         .org    0x38                    /* 0x20 ~ 0x37 reserved */
> diff --git a/arch/loongarch/kernel/vmlinux.lds.S b/arch/loongarch/kernel/vmlinux.lds.S
> index e8e97dbf9ca4..c6f89e51257a 100644
> --- a/arch/loongarch/kernel/vmlinux.lds.S
> +++ b/arch/loongarch/kernel/vmlinux.lds.S
> @@ -6,6 +6,7 @@
>
>  #define PAGE_SIZE _PAGE_SIZE
>  #define RO_EXCEPTION_TABLE_ALIGN       4
> +#define TO_PHYS_MASK                   0x000fffffffffffff /* 48-bit */
>
>  /*
>   * Put .bss..swapper_pg_dir as the first thing in .bss. This will
> @@ -142,6 +143,7 @@ SECTIONS
>
>  #ifdef CONFIG_EFI_STUB
>         /* header symbols */
> +       _kernel_entry_phys = kernel_entry & TO_PHYS_MASK;

 -       _kernel_entry_phys = kernel_entry & TO_PHYS_MASK;
 +       _kernel_entry_phys = ABSOLUTE(kernel_entry & TO_PHYS_MASK);

>         _kernel_asize = _end - _text;
>         _kernel_fsize = _edata - _text;
>         _kernel_vsize = _end - __initdata_begin;
> diff --git a/drivers/firmware/efi/libstub/loongarch.c b/drivers/firmware/efi/libstub/loongarch.c
> index 684c9354637c..60c145121393 100644
> --- a/drivers/firmware/efi/libstub/loongarch.c
> +++ b/drivers/firmware/efi/libstub/loongarch.c
> @@ -41,7 +41,7 @@ static efi_status_t exit_boot_func(struct efi_boot_memmap *map, void *priv)
>  unsigned long __weak kernel_entry_address(unsigned long kernel_addr,
>                 efi_loaded_image_t *image)
>  {
> -       return *(unsigned long *)(kernel_addr + 8) - VMLINUX_LOAD_ADDRESS + kernel_addr;
> +       return *(unsigned long *)(kernel_addr + 8) - TO_PHYS(VMLINUX_LOAD_ADDRESS) + kernel_addr;
>  }
>
>  efi_status_t efi_boot_kernel(void *handle, efi_loaded_image_t *image,
>
> --
> 2.43.0
>
>

- Rui