Re: [kvm-unit-tests PATCH 1/3] riscv: Add Image header to flat binaries

[Andrew Jones <andrew.jones@linux.dev>]

On Mon, Dec 09, 2024 at 10:44:40PM -0600, Samuel Holland wrote:
> This allows flat binaries to be understood by U-Boot's booti command and
> its PXE boot flow.
> 
> Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
> ---
>  riscv/cstart.S | 16 +++++++++++++++-
>  1 file changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/riscv/cstart.S b/riscv/cstart.S
> index b7ee9b9c..106737a1 100644
> --- a/riscv/cstart.S
> +++ b/riscv/cstart.S
> @@ -39,15 +39,29 @@
>   * The hartid of the current core is in a0
>   * The address of the devicetree is in a1
>   *
> - * See Linux kernel doc Documentation/riscv/boot.rst
> + * See Linux kernel doc Documentation/arch/riscv/boot.rst and
> + * Documentation/arch/riscv/boot-image-header.rst
>   */
>  .global start
>  start:
> +	j	1f
> +	.balign	8
> +	.dword	0				// text offset

When I added a header like this for the bpi I needed the text offset to be
0x200000, like Linux has it.  Did you do something to avoid that?

> +	.dword	stacktop - ImageBase		// image size
> +	.dword	0				// flags
> +	.word	(0 << 16 | 2 << 0)		// version
> +	.word	0				// res1
> +	.dword	0				// res2
> +	.ascii	"RISCV\0\0\0"			// magic
> +	.ascii	"RSC\x05"			// magic2
> +	.word	0				// res3
> +
>  	/*
>  	 * Stash the hartid in scratch and shift the dtb address into a0.
>  	 * thread_info_init() will later promote scratch to point at thread
>  	 * local storage.
>  	 */
> +1:
>  	csrw	CSR_SSCRATCH, a0
>  	mv	a0, a1
>  
> -- 
> 2.39.3 (Apple Git-146)
>

Thanks,
drew