docs/firmware: Update FW_JUMP documentation

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

Signed-off-by: Nylon Chen <nylon.chen@sifive.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Anup Patel <anup@brainfault.org>
This commit is contained in:
Nylon.Chen
2022-09-27 15:34:09 +08:00
committed by Anup Patel
parent 7f09fba86e
commit 7105c189f6

View File

@@ -41,6 +41,22 @@ follows:
provided, then the OpenSBI firmware will pass the FDT address passed by the
previous booting stage to the next booting stage.
When using the default *FW_JUMP_FDT_ADDR* with *PLATFORM=generic*, you must
ensure *FW_JUMP_FDT_ADDR* is set high enough to avoid overwriting the kernel.
You can use the following method.
```
${CROSS_COMPILE}objdump -h $KERNEL_ELF | sort -k 5,5 | awk -n '/^ +[0-9]+ /\
{addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}' \
| (( `tail -1` > 0x2200000 )) && echo fdt overlaps kernel,\
increase FW_JUMP_FDT_ADDR
${LLVM}objdump -h --show-lma $KERNEL_ELF | sort -k 5,5 | \
awk -n '/^ +[0-9]+ / {addr="0x"$3; size="0x"$5; printf "0x""%x\n",addr+size}'\
| (( `tail -1` > 0x2200000 )) && echo fdt overlaps kernel,\
increase FW_JUMP_FDT_ADDR
```
*FW_JUMP* Example
-----------------