linux-kernel - Re: [RFC PATCH] x86/doc/boot_protocol: Correct the description of "reloc"

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Message-ID: <faabfe47-ba3e-5a92-af65-dc26e8e2ecb9@cn.fujitsu.com>
Date:   Thu, 26 Sep 2019 15:55:51 +0800
From:   Cao jin <caoj.fnst@...fujitsu.com>
To:     Ingo Molnar <mingo@...nel.org>
CC:     <x86@...nel.org>, <linux-kernel@...r.kernel.org>,
        <linux-doc@...r.kernel.org>, <tglx@...utronix.de>,
        <mingo@...hat.com>, <bp@...en8.de>, <hpa@...or.com>,
        <corbet@....net>
Subject: Re: [RFC PATCH] x86/doc/boot_protocol: Correct the description of
 "reloc"

On 9/26/19 2:01 PM, Ingo Molnar wrote:
> * Cao jin <caoj.fnst@...fujitsu.com> wrote:
> 
>> The fields marked with (reloc) actually are not dedicated for writing,
>> but communicating info for relocatable kernel with boot loaders. For
>> example:
>>
>>     ============    ============
>>     Field name:     pref_address
>>     Type:           read (reloc)
>>     Offset/size:    0x258/8
>>     Protocol:       2.10+
>>     ============    ============
>>
>>     ============    ========================
>>     Field name:     code32_start
>>     Type:           modify (optional, reloc)
>>     Offset/size:    0x214/4
>>     Protocol:       2.00+
>>     ============    ========================
>>
>> Signed-off-by: Cao jin <caoj.fnst@...fujitsu.com>
>> ---
>> Unless I have incorrect non-native understanding for "fill in", I think
>> this is inaccurate.
>>
>>  Documentation/x86/boot.rst | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/Documentation/x86/boot.rst b/Documentation/x86/boot.rst
>> index 08a2f100c0e6..a611bf04492d 100644
>> --- a/Documentation/x86/boot.rst
>> +++ b/Documentation/x86/boot.rst
>> @@ -243,7 +243,7 @@ bootloader ("modify").
>>  
>>  All general purpose boot loaders should write the fields marked
>>  (obligatory).  Boot loaders who want to load the kernel at a
>> -nonstandard address should fill in the fields marked (reloc); other
>> +nonstandard address should consult with the fields marked (reloc); other
>>  boot loaders can ignore those fields.
>>  
>>  The byte order of all fields is littleendian (this is x86, after all.)
> 
> Well, this documentation is written from the point of view of a 
> *bootloader*, not the kernel. So the 'fill in' says that the bootloader 
> should write those fields - which is correct, right?
> 

Take pref_address or relocatable_kernel for example, they have type:
read (reloc), does boot loader need to write them? I don't see grub does
this at least.

-- 
Sincerely,
Cao jin