[PATCH 1/1] docs/firmware: Update FW_JUMP documentation

[Anup Patel]

On Tue, Sep 13, 2022 at 11:16 AM Nylon Chen <nylon.chen at sifive.com> wrote:
>
> From: "Nylon.Chen" <nylon.chen at sifive.com>
>
> Add a tip for OpenSBI's Jump mode.
>
> help user avoids the kernel overwritten.

Minor grammer error.

This can be:

"Add a tip for OpenSBI's FW_JUMP which helps users avoid
overwriting the kernel."

>
> Signed-off-by: Nylon Chen <nylon.chen at sifive.com>
> Signed-off-by: Nylon.Chen <nylon.chen at sifive.com>

Otherwise, it looks good to me.

Reviewed-by: Anup Patel <anup at brainfault.org>

Regards,
Anup

> ---
>  docs/firmware/fw_jump.md | 18 ++++++++++++++++++
>  1 file changed, 18 insertions(+)
>
> diff --git a/docs/firmware/fw_jump.md b/docs/firmware/fw_jump.md
> index 35a4301..c20d722 100644
> --- a/docs/firmware/fw_jump.md
> +++ b/docs/firmware/fw_jump.md
> @@ -40,6 +40,24 @@ follows:
>    the booting stage following the OpenSBI firmware. If this option is not
>    provided, then the OpenSBI firmware will pass the FDT address passed by the
>    previous booting stage to the next booting stage.
> +
> +  If your *PLATFORM=generic* and your *FW_JUMP_FDT_ADDR* is default, you must check
> +  your Linux size because Linux will be overwritten in OpneSBI's FDT copy loop.
> +  You can use the following method.
> +
> +  ```
> +  LAST_SECTION=`${CROSS_COMPILE}objdump -h vmlinux | grep "00*" | awk '{print $5,$3}'\
> +  | sort -rfu | head -n 1 | awk '{split($0,addr," ");print addr[1]}'` \
> +  && LAST_SECTION_SIZE=`${CROSS_COMPILE}objdump -h vmlinux | grep "00*" |awk '{print $5,$3}'\
> +  | sort -rfu | head -n 1 | awk '{split($0,addr,"")}'` \
> +  && OFFSET_ADDR=$(( 16#$LAST_SECTION_SIZE + 16#$LAST_SECTION)) \
> +  && printf "The LMA of the last section of the Kernel is 0x%X\n" ${OFFSET_ADDR}
> +  ```
> +
> +  If the result is bigger than the default of FW_JUMP_FDT_ADDR(0x2200000),
> +  you must change it to avoid the problem of being overwritten.
> +
> +
>
>  *FW_JUMP* Example
>  -----------------
> --
> 2.36.1
>
>
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