Re: [PATCH 05/11] vmlinux.lds.h: Preserve DTB sections from being discarded after init

[Stephen Boyd]

Quoting Andrea della Porta (2024-08-20 07:36:07)
> The special section .dtb.init.rodata contains dtb and dtbo compiled
> as objects inside the kernel and ends up in .init.data sectiion that
> will be discarded early after the init phase. This is a problem for
> builtin drivers that apply dtb overlay at runtime since this happens
> later (e.g. during bus enumeration) and also for modules that should
> be able to do it dynamically during runtime.
> Move the dtb section to .data.
> 
> Signed-off-by: Andrea della Porta <andrea.porta@xxxxxxxx>
> ---
>  include/asm-generic/vmlinux.lds.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index ad6afc5c4918..3ae9097774b0 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -365,6 +365,7 @@
>         TRACE_PRINTKS()                                                 \
>         BPF_RAW_TP()                                                    \
>         TRACEPOINT_STR()                                                \
> +       KERNEL_DTB()                                                    \

The KERNEL_DTB() macro shows the section name is dtb.init.rodata. Can
you remove the ".init." part if this isn't initdata anymore? And
shouldn't it be in the RO_DATA() macro?

It would be nice to keep the initdata properties when this isn't used
after init as well. Perhaps we need another macro and/or filename to
indicate that the DTB{O} can be thrown away after init/module init.