linux-kernel - Re: [PATCH] x86/boot: clear rsdp address in boot

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Message-ID: <e7ca96fe-5bd5-d051-3bf4-abcca52e73a9@suse.com>
Date:   Tue, 4 Dec 2018 07:03:58 +0100
From:   Juergen Gross <jgross@...e.com>
To:     "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org
Cc:     sstabellini@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de
Subject: Re: [PATCH] x86/boot: clear rsdp address in boot_params for broken
 loaders

On 04/12/2018 06:49, H. Peter Anvin wrote:
> On 12/3/18 9:32 PM, Juergen Gross wrote:
>>
>> I'd like to send a followup patch doing that. And I'd like to not only
>> test sentinel for being non-zero, but all padding fields as well. This
>> should be 4.21 material, though.
>>
> 
> No, you can't do that.  That breaks backwards compatibility.

So you are speaking about paddings which are at places where there used
to be some information? Shouldn't those be named "_res*"?
Recycling such paddings with some useful information seems to be rather
dangerous then.

I'd like to have at least some idea which boot loader is not passing a
clean struct boot_params. So I think we should at least have some debug
or info messages telling us which paddings are not zero initially to be
able to either fix the boot loader or switch from _pad* to _res* naming.

Juergen