linux-kernel - Re: [PATCH] Documentation/x86/boot.rst: minor improvement

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Message-ID: <2486ec9a-64fe-6026-274d-4afa3548273f@cn.fujitsu.com>
Date:   Tue, 1 Sep 2020 14:23:04 +0800
From:   Cao jin <caoj.fnst@...fujitsu.com>
To:     "H. Peter Anvin" <hpa@...or.com>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC:     <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
        <corbet@....net>
Subject: Re: [PATCH] Documentation/x86/boot.rst: minor improvement

On 9/1/20 1:35 PM, H. Peter Anvin wrote:
> If you are going to fix the language...
> 
> On 2020-08-31 22:25, Cao jin wrote:
>> Sorry, I mis-copied 2 addresses. make sure they are CCed.
>>
>> On 9/1/20 11:41 AM, Cao jin wrote:
>>> Typo fix & file name update
>>>

I did quick search in dict & google, didn't see ident = identity, my omission.

>>> Signed-off-by: Cao jin <caoj.fnst@...fujitsu.com>
...

>>> @@ -1391,7 +1391,7 @@ In 64-bit boot protocol, the kernel is started by jumping to the
>>>  
>>>  At entry, the CPU must be in 64-bit mode with paging enabled.
> 
> (Paging enabled is redundant here.)

Yes, 64-bit defaults with paging enabled. Maybe it is a little bit helpful for
newbies.

> 
>>>  The range with setup_header.init_size from start address of loaded
>>> -kernel and zero page and command line buffer get ident mapping;
>>> +kernel and zero page and command line buffer get identity mapping;
> 
> The range with setup_header.init_size from start address of the loaded kernel,
> the zero page, and the command line buffer get identity-mapped, anda GDT must
> be loaded with the descriptors for selectors __BOOT_CS(0x10) and
> __BOOT_DS(0x18): both descriptors must be 4G flat segment with __BOOT_CS
> having execute/read
> permission and __BOOT_DS...
> 
> Also, it might be useful to take a look to see if other data structures, like
> setup_data and the initrd also need to be in the identity map.
> 

Thanks for your info. I have indistinct memory that KASLR need them identity
mapped. I will take a look.

-- 
Sincerely,
Cao jin