回复: 回复: [PATCH] bootm: Pass SMP core ID and DTB address for ELF-formatted kernels

[牛 志宏]

Yes, this is a new OS currently being developed with plans to support Linux compatibility.
Registers a0 and a1 pass the boot core ID and DTB address respectively, following a de facto standard shared by both the SBI (RISC-V Supervisor Binary Interface) specification and the Linux implementation.
My rationale is: if U-Boot supports the combination of kernel + ELF loading, why shouldn't we implement this capability as well?


________________________________
发件人: Tom Rini
已发送: 2025 年 5 月 29 日 星期四 23:49
收件人: 牛 志宏
抄送: Heinrich Schuchardt; Simon Glass; u-boot at lists.denx.de; Leo Yu-Chi Liang; Rick Chen
主题: Re: 回复: [PATCH] bootm: Pass SMP core ID and DTB address for ELF-formatted kernels

On Thu, May 29, 2025 at 09:33:56AM +0000, 牛 志宏 wrote:
> hi team,
>
> The ITS file looks something like the following, and the kernel is not a standard Linux kernel:
> ```
> /dts-v1/;
>
> / {
>     ...
>     images {
>         kernel {
>             type = "kernel";
>             arch = "riscv";
>             os = "elf";
>             ...
>         };
>
>         fdt {
>             type = "flat_dt";
>             arch = "riscv";
>             ...
>         };
>     };
>     ...
> };
> ```
>
> To handle this scenario, we need to:
>
>   1.
> Access the values of the `type`, os, and arch fields stored in bootm_headers->image_info to determine the current context.
>   2.
> Access the boot_hart and ft_addr stored in the gd variable to update argc and argv.
>
> Not sure whether accessing the bootm_headers and gd variables in lib/elf.c is allowed or safe.
So this is why I was asking if there's some more generalized
specification we can reference. Is the OS you're using something
pre-existing and so we need to do what it already expect from some other
loader? Or is it something you're also creating and if so, why not
follow the linux kernel convention for compatibility?

--
Tom