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SubjectRe: questions about header.S
Date
Dear Maintainers,

  Could you help to give a hint?
  Thanks in advance.

--
Sincerely,
Cao jin

On 03/17/2018 06:01 PM, Cao jin wrote:
> Hi,
>
>   I find two small questions which confuse me a little.
>
> 1.
> # Check signature at end of setup
> cmpl $0x5a5aaa55, setup_sig
> jne setup_bad
>
> setup_sig is defined in setup.ld, which points to the constant also
> defined in setup.ld, so I don't figure out in which case they don't
> equal and jump to setup_bad?
>
> In my test, drop these 2 lines seems fine, system can boot without any
> obvious error.
>
> 2.
> # Zero the bss
> movw $__bss_start, %di
> movw $_end+3, %cx
> xorl %eax, %eax
> subw %di, %cx
> shrw $2, %cx
> rep; stosl
>
> It is not a big deal, but I think replace "_end" with "__bss_end" make
> more sense, and "_end" is already aligned to word length. And, there is
> no other code use symbol "__bss_end". So I don't know is there any
> reason to use "_end" here?
>
> In my test, replace the 2nd line with:
>
> movw $_end, %cx
>
> or:
>
> movw $__bss_end+3, %cx
>
> are both fine.
>


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