[PATCH] board_f: Relocate fdt if SKIP_RELOC and fdt is in bss

[Simon Glass]

Hi Kunihiko,

On Thu, 8 Jun 2023 at 07:53, Kunihiko Hayashi
<hayashi.kunihiko at socionext.com> wrote:
>
> There are cases that the devicetree blob is placed after _end, such as
> fdt_find_separate() returns _end. This is in bss area cleared before
> relocation.
>
> When GD_FLG_SKIP_RELOC is set, the blob is still in bss, but will be
> cleared. As a result, the devicetree become invalid.
>
> To avoid this issue, should relocate it to the new fdt area using the
> latter condition in reloc_fdt().
>
> Signed-off-by: Kunihiko Hayashi <hayashi.kunihiko at socionext.com>
> ---
>  common/board_f.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/common/board_f.c b/common/board_f.c
> index 51d2f3c365e9..9a245872d190 100644
> --- a/common/board_f.c
> +++ b/common/board_f.c
> @@ -622,7 +622,8 @@ static int init_post(void)
>  static int reloc_fdt(void)
>  {
>         if (!IS_ENABLED(CONFIG_OF_EMBED)) {
> -               if (gd->flags & GD_FLG_SKIP_RELOC)
> +               if (gd->flags & GD_FLG_SKIP_RELOC &&
> +                   gd->fdt_blob != &_end)

!IS_ENABLED(CONFIG_OF_EMBED)  == IS_ENABLED(CONFIG_OF_SEPARATE)

reloc_fdt() is only called by U-Boot (not SP)

So the FDT was found by fdt_find_separate() and gd->fdt_blob == &_end

So, is there any case where:

gd->flags & GD_FLG_SKIP_RELO is true
gd->fdt_blob != &_end is true

?

I can't think of one.

If that is the case, then you could add a comment to this effect and
unconditionally relocate if !CONFIG_OF_EMBED.

Of course the down size is that you would probably rather relocate it
to just after BSS (rather than to the top of memory) but it doesn't
much matter, I suspect.

>                         return 0;
>                 if (gd->new_fdt) {
>                         memcpy(gd->new_fdt, gd->fdt_blob,
> --
> 2.25.1
>

Regards,
Simon