[PATCH v8 4/8] arm: armv7: save boot arguments

[Ilias Apalodimas]

On Sat, 3 Feb 2024 at 18:37, Raymond Mao <raymond.mao at linaro.org> wrote:
>
> Save boot arguments r[0-3] into an array for handover of bloblist from
> previous boot stage.
>
> Signed-off-by: Raymond Mao <raymond.mao at linaro.org>
> Suggested-by: Ard Biesheuvel <ardb at kernel.org>
> ---
> Changes in v2
> - New patch file created for v2.
> Changes in v3
> - Swap value of r0 with r2.
> Changes in v4
> - Fix a bug when saving the boot args.
> Changes in V5
> - Drop the dependence on OF_BOARD.
> Changes in V7
> - Exclude the saved_args when BLOBLIST is disabled.
> Changes in V8
> - Use PC-relative reference for saved_args.
> - Add 4-byte alignment for saved_args.
>
>  arch/arm/cpu/armv7/start.S | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
>
> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> index 69e281b086..7730a16e51 100644
> --- a/arch/arm/cpu/armv7/start.S
> +++ b/arch/arm/cpu/armv7/start.S
> @@ -152,9 +152,38 @@ ENDPROC(c_runtime_cpu_setup)
>   *
>   *************************************************************************/
>  WEAK(save_boot_params)
> +#if (IS_ENABLED(CONFIG_BLOBLIST))
> +       /* Calculate the PC-relative address of saved_args */
> +       adr     r12, saved_args_offset
> +       ldr     r13, saved_args_offset
> +       add     r12, r12, r13
> +
> +       /*
> +        * Intentionally swapping r0 with r2 in order to simplify the C
> +        * function we use later.
> +        */
> +       str     r2, [r12]
> +       str     r1, [r12, #4]
> +       str     r0, [r12, #8]
> +       str     r3, [r12, #12]
> +#endif
>         b       save_boot_params_ret            @ back to my caller
>  ENDPROC(save_boot_params)
>
> +#if (IS_ENABLED(CONFIG_BLOBLIST))
> +saved_args_offset:
> +       .long   saved_args - .  /* offset from current code to save_args */
> +
> +       .section .data
> +       .align 2
> +       .global saved_args
> +saved_args:
> +       .rept 4
> +       .word 0
> +       .endr
> +END(saved_args)
> +#endif
> +
>  #ifdef CONFIG_ARMV7_LPAE
>  WEAK(switch_to_hypervisor)
>         b       switch_to_hypervisor_ret
> --
> 2.25.1
>

Reviewed-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>