docs: Correct FW_JUMP_FDT_ADDR calculation example

When using `PLATFORM=generic` defaults, the kernel is loaded at
`FW_JUMP_ADDR`, and the FDT is loaded at `FW_JUMP_FDT_ADDR.

Therefore, the maximum kernel size before `FW_JUMP_FDT_ADDR` must
be increased is `$(( FW_JUMP_FDT_ADDR - FW_JUMP_ADDR ))`.

The example calculation assumes `rv64`, and is wrong to boot
(off by 0x200000). Fix it and update it for the general case.

Signed-off-by: Gabriel Somlo <gsomlo@gmail.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Xiang W <wxjstz@126.com>
This commit is contained in:
Gabriel Somlo
2023-03-30 16:25:30 -04:00
committed by Anup Patel
parent edc9914392
commit ee016a7bb0

View File

@@ -43,18 +43,18 @@ follows:
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.
You can use the following method (e.g., using bash or zsh):
```
${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
${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` > (FW_JUMP_FDT_ADDR - FW_JUMP_ADDR) )) &&
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
${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` > (FW_JUMP_FDT_ADDR - FW_JUMP_ADDR) )) &&
echo fdt overlaps kernel, increase FW_JUMP_FDT_ADDR
```
*FW_JUMP* Example