linux-kernel - Re: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on kexec-ed kernel

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Message-ID: <e88fda9c-bd5a-d263-cd8a-380828dd6a93@ce.jp.nec.com>
Date:   Thu, 11 Apr 2019 09:32:59 +0000
From:   Junichi Nomura <j-nomura@...jp.nec.com>
To:     Boris Petkov <bp@...en8.de>
CC:     Dave Young <dyoung@...hat.com>,
        Chao Fan <fanc.fnst@...fujitsu.com>,
        Baoquan He <bhe@...hat.com>, Kairui Song <kasong@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] x86/boot: Use efi_setup_data for searching RSDP on
 kexec-ed kernel

On 4/11/19 6:21 PM, Boris Petkov wrote:
> On April 11, 2019 11:13:03 AM GMT+02:00, Junichi Nomura <j-nomura@...jp.nec.com> wrote:
>> On 4/11/19 5:37 PM, Borislav Petkov wrote:
>>> On Thu, Apr 11, 2019 at 08:16:45AM +0000, Junichi Nomura wrote:
>>>> kexec_get_rsdp_addr() might fail on kexec-booted kernel, e.g. if the
>>>> setup_data was invalid. In such a case, falling back to
>> efi_get_rsdp_addr()
>>>> will hit the problem of accessing invalid table pointer again.
>>>
>>> Then you need to do this:
>>>
>>> 	if (kexeced kernel) {
>>> 		addr = kexec_get_rsdp_addr();
>>> 		if (!addr) {
>>> 			/* cannot get address */
>>> 			return -1;
>>> 		}
>>>
>>> 		return addr;
>>> 	}
>>>
>>> and the calling function get_rsdp_addr() must check the return value
>> and
>>> if it is not 0, return immediately.
>>
>> Do you mean making get_rsdp_addr() like this?
> 
> Does that look like what I've typed above?

No. But that's why I asked the question. Do you mean putting
the above code in efi_get_rsdp_addr()?

-- 
Jun'ichi Nomura, NEC Corporation / NEC Solution Innovators, Ltd.