linux-kernel - Re: question about head

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Message-ID: <023da151-bb1d-1b11-ec1d-01eb675d528f@cn.fujitsu.com>
Date:   Tue, 22 Jan 2019 15:31:25 +0800
From:   Cao jin <caoj.fnst@...fujitsu.com>
To:     <kirill.shutemov@...ux.intel.com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: question about head_64.S

Hi, Kirll,

On 1/15/19 7:45 PM, Cao jin wrote:
> Hi,
>   I have been digging into this file for a while, and I still have 2
> questions unclear, hope to get your help.
> 

> 
> 2.
> Why gdt64 has following definition?:
> 
> gdt64:
> 	.word	gdt_end - gdt
> 	.long	0
> 	.word	0
> 	.quad   0
> 
> obviously, gdt64 stores the GDTR content under x86_64, which is 10 bytes
> long, so why not just:
> 
> gdt64:
> 	.word	gdt_end - gdt
> 	.quad   0
> 
> With above modification, it can boot.
> 

Seems you introduced gdt64 code in commit beebaccd50, could you help
with this question?

And it also remind me of another question about adjust_got which is also
introduced by you. Because I failed to construct a test environment with
ld version less than 2.24 until now, so I wanna do a quick ask here:
does it make sense to adjust GOT from the 4th entry of it? Because as I
know, the first 3 entries are special one, which (I guess) will be not used.
-- 
Sincerely,
Cao jin