Re: [PATCH v8 0/3] x86/boot/KASLR: Parse ACPI table and limit kaslr in immovable memory
From: Chao Fan
Date: Thu Oct 11 2018 - 01:52:43 EST
On Thu, Oct 11, 2018 at 08:29:55AM +0800, Baoquan He wrote:
>On 10/10/18 at 03:44pm, Masayoshi Mizuma wrote:
>> On Wed, Oct 10, 2018 at 05:30:57PM +0800, Baoquan He wrote:
>> > On 10/10/18 at 11:19am, Borislav Petkov wrote:
>> > > On Wed, Oct 10, 2018 at 11:14:26AM +0200, Thomas Gleixner wrote:
>> > > > Yes, it's different, but if the SRAT information is available early, then
>> > > > the command line parameter can go away because then the required
>> > > > information for Masa's problem is available as well.
>> > >
>> > > Exactly. And I'd prefer we delayed the command line parameter until we
>> > > figure out we really need it and not expose it to upstream and then
>> > > remove it shortly after.
>> > >
>> > > So I'd suggest we move Masa's patches to a separate branch and not send
>> > > it up this round.
>> > Yes, sounds more reasonable if we can reuse functions in Chao's patch 1/3
>> > to solve the padding issue.
>> Thanks for your comments! Yes, immovable_mem[num_immovable_mem] in Chao's
>> patch may be useful for calculating the padding size. If so, we don't
>> need the new kernel parameter. It's nice!
>> Do you happen to have ideas how we access immovable_mem[num_immovable_mem]
>> from arch/x86/mm/kaslr.c ? It is located to arch/x86/boot/compressed/*, so
>> I suppose it is not easy to access it...
>> I would appreciate if you could give some advice.
>Hmm, they are living in different life cycle and space. So we can only
>reuse the code from Chao's patch, but not the variable. Means we need
>go through the SRAT accessing again in arch/x86/mm/kaslr.c and fill
>immovable_mem[num_immovable_mem] for mm/kaslr.c usage, if we decide to
>do like that.
Reading three times is redundant, but reading two times is needed.
Becasue the ACPI code run very stable, but we need more information
As for Masa's issue, I am wondering whether we can tranfer the
information or only the address of SRAT table from compressed period
to the period after start_kernel().