On 10/24/20 10:41 AM, Stefan Sperling wrote:
> On Sat, Oct 24, 2020 at 04:11:00PM +0200, Filippo Valsorda wrote:
>> Fair enough, but "there's no auto-assembly and it's inefficient and
>> nothing stops you from messing with the intermediate discipline" is a
>> different kind of not supported than "you should expect kernel panics".
>>
>> If the latter is the case, maybe it should be documented in the
>> softraid(4) CAVEATS, as it breaks the sd(4) abstraction.
> 
> Neither Joel's mail nor the word "unsupported" imply a promise
> that it will work without auto-assembly and with inefficient i/o.
> 
> Unsupported means unsupported. We don't need to list any reasons
> for this in user-facing documentation.

One could also argue that the kernel must never panic because userspace
did something wrong.  The only exceptions I am aware of are:

- init dying
- corrupt kernel image
- corrupt root filesystem
- not being able to mount the root filesystem
- overwriting kernel memory with /dev/mem or DMA
- hardware fault

In particular, I would expect that at securelevel 1 or higher,
userspace should not be able to cause a fatal kernel page fault.

Demi

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