Re: [PATCH v3 2/2] pstore/ramoops: Add ramoops.mem_name= command line option

[Kees Cook]

On June 13, 2024 7:06:47 AM PDT, Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
>On Thu, 13 Jun 2024 at 15:26, Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>>
>> On Thu, 13 Jun 2024 08:11:48 +0200
>> Ard Biesheuvel <ardb@xxxxxxxxxx> wrote:
>> > >
>> > > I've added one more comment to v5, with that fixed I can take this.
>> > >
>> >
>> > 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. The kernel command line has
>> broken in the past. If you update the kernel, you can update the
>> command line. There's no "no user visible regressions" rule. It's
>> "Don't break user space". This has nothing to do with user space.
>>
>> > to begin with. This needs at least a huge disclaimer that this rule
>> > does not apply, and if this works today, there is no guarantee that it
>> > will keep working on newer kernels. Otherwise, you will be making the
>> > job of the people who work on the boot code significantly more
>> > difficult. And even then, I wonder whether Linus and #regzcop are
>> > going to honour such a disclaimer.
>>
>> Again, this has nothing to do with user space. The rule Linus talks
>> about is breaking user space. This is about kernel debugging. Something
>> *completely different*!
>>
>> >
>> > So this belongs downstream, unless some guarantees can be provided
>> > that this functionality is exempt from the usual regression policies.
>>
>> I disagree. kexec/kdump also has the same issues.
>>
>
>Fair enough. 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.

Yeah, I should better document this for pstore as a whole, but I've already made the call that cross-kernel-versison operation is best effort.

-Kees

-- 
Kees Cook