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docs/firmware: Update FW_JUMP documentation

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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
1 changed files with 16 additions and 0 deletions
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16
docs/firmware/fw_jump.md
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@@ -41,6 +41,22 @@ follows:
provided, then the OpenSBI firmware will pass the FDT address passed by the provided, then the OpenSBI firmware will pass the FDT address passed by the
previous booting stage to the next booting stage. 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 *FW_JUMP* Example
----------------- -----------------