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SubjectRe: [PATCH] riscv: save space on the magic number field of image header
On Fri, Sep 6, 2019 at 12:50 PM Chester Lin <clin@suse.com> wrote:
>
> Change the symbol from "RISCV" to "RSCV" so the magic number can be 32-bit
> long, which is consistent with other architectures.
>
> Signed-off-by: Chester Lin <clin@suse.com>
> ---
> arch/riscv/include/asm/image.h | 9 +++++----
> arch/riscv/kernel/head.S | 5 ++---
> 2 files changed, 7 insertions(+), 7 deletions(-)
>
> diff --git a/arch/riscv/include/asm/image.h b/arch/riscv/include/asm/image.h
> index ef28e106f247..ec8bbfe86dde 100644
> --- a/arch/riscv/include/asm/image.h
> +++ b/arch/riscv/include/asm/image.h
> @@ -3,7 +3,8 @@
> #ifndef __ASM_IMAGE_H
> #define __ASM_IMAGE_H
>
> -#define RISCV_IMAGE_MAGIC "RISCV"
> +#define RISCV_IMAGE_MAGIC "RSCV"
> +
>
> #define RISCV_IMAGE_FLAG_BE_SHIFT 0
> #define RISCV_IMAGE_FLAG_BE_MASK 0x1
> @@ -39,9 +40,9 @@
> * @version: version
> * @res1: reserved
> * @res2: reserved
> - * @magic: Magic number
> * @res3: reserved (will be used for additional RISC-V specific
> * header)
> + * @magic: Magic number
> * @res4: reserved (will be used for PE COFF offset)
> *
> * The intention is for this header format to be shared between multiple
> @@ -57,8 +58,8 @@ struct riscv_image_header {
> u32 version;
> u32 res1;
> u64 res2;
> - u64 magic;
> - u32 res3;
> + u64 res3;
> + u32 magic;
> u32 res4;
> };
> #endif /* __ASSEMBLY__ */
> diff --git a/arch/riscv/kernel/head.S b/arch/riscv/kernel/head.S
> index 0f1ba17e476f..1f8fffbecf68 100644
> --- a/arch/riscv/kernel/head.S
> +++ b/arch/riscv/kernel/head.S
> @@ -39,9 +39,8 @@ ENTRY(_start)
> .word RISCV_HEADER_VERSION
> .word 0
> .dword 0
> - .asciz RISCV_IMAGE_MAGIC
> - .word 0
> - .balign 4
> + .dword 0
> + .ascii RISCV_IMAGE_MAGIC
> .word 0
>
> .global _start_kernel
> --
> 2.22.0
>

This change is not at all backward compatible with
existing booti implementation in U-Boot.

It changes:
1. Magic offset
2. Magic value itself

We don't see this header changing much apart from
res1/res2 becoming flags in-future. The PE COFF header
will be append to this header in-future and it will have lot
more information.

Regards,
Anup

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