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Date: Thu, 13 Jun 2024 07:42:01 -0700
From: Kees Cook <kees@kernel.org>
To: Ard Biesheuvel <ardb@kernel.org>, Steven Rostedt <rostedt@goodmis.org>
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On June 13, 2024 7:06:47 AM PDT, Ard Biesheuvel <ardb@kernel=2Eorg> wrote:
>On Thu, 13 Jun 2024 at 15:26, Steven Rostedt <rostedt@goodmis=2Eorg> wrot=
e:
>>
>> On Thu, 13 Jun 2024 08:11:48 +0200
>> Ard Biesheuvel <ardb@kernel=2Eorg> wrote:
>> > >
>> > > I've added one more comment to v5, with that fixed I can take this=
=2E
>> > >
>> >
>> > So how is this supposed to work wrt to the rigid 'no user visible
>> > regressions' rule, given that this whole thing is a best effort thing
>>
>> This has nothing to do with user space=2E The kernel command line has
>> broken in the past=2E If you update the kernel, you can update the
>> command line=2E There's no "no user visible regressions" rule=2E It's
>> "Don't break user space"=2E This has nothing to do with user space=2E
>>
>> > to begin with=2E This needs at least a huge disclaimer that this rule
>> > does not apply, and if this works today, there is no guarantee that i=
t
>> > will keep working on newer kernels=2E Otherwise, you will be making t=
he
>> > job of the people who work on the boot code significantly more
>> > difficult=2E And even then, I wonder whether Linus and #regzcop are
>> > going to honour such a disclaimer=2E
>>
>> Again, this has nothing to do with user space=2E The rule Linus talks
>> about is breaking user space=2E This is about kernel debugging=2E Somet=
hing
>> *completely different*!
>>
>> >
>> > So this belongs downstream, unless some guarantees can be provided
>> > that this functionality is exempt from the usual regression policies=
=2E
>>
>> I disagree=2E kexec/kdump also has the same issues=2E
>>
>
>Fair enough=2E As long as it is documented that there is no guarantee
>that this will keep working over a kernel upgrade, then I have no
>objections=2E

Yeah, I should better document this for pstore as a whole, but I've alread=
y made the call that cross-kernel-versison operation is best effort=2E

-Kees

--=20
Kees Cook