[PATCH] ARM: compressed: discard ksym/kcrctab input section

[Ard Biesheuvel]

On 20 October 2017 at 17:11, Russell King - ARM Linux
<linux at armlinux.org.uk> wrote:
> On Fri, Oct 20, 2017 at 04:28:49PM +0100, Ard Biesheuvel wrote:
>> On 20 October 2017 at 16:25, Gregory CLEMENT
>> <gregory.clement at free-electrons.com> wrote:
>> > Hi Ard,
>> >
>> >  On jeu., oct. 12 2017, Ard Biesheuvel <ard.biesheuvel at linaro.org> wrote:
>> >
>> >> On 12 October 2017 at 10:45, Russell King - ARM Linux
>> >> <linux at armlinux.org.uk> wrote:
>> >>> On Thu, Oct 12, 2017 at 11:24:57AM +0200, Gregory CLEMENT wrote:
>> >>>> Hi Ard,
>> >>>>
>> >>>> Can we move forward to fix the booting problem ?
>> >>>>
>> >>>> What about amending your commit log with this new information and then
>> >>>> submit it to Russell patch system?
>> >>>
>> >>> Well, I think there's a choice that needs to be made between this
>> >>> approach and Arnd's approach.
>> >>>
>> >>> I'm not all that thrilled with the need to add explicit alignment to
>> >>> data that is inherently a byte stream, and that invariably results in
>> >>> unaligned data words even if you do align the start of it.  That
>> >>> sounds to me very much like a hack rather than a proper solution.
>> >>> So, right now I'm leaning more towards Arnd's solution than Ard's
>> >>> from what's been said in this thread.
>> >>>
>> >>
>> >> I agree that the struct type unaligned accessors are the best choice
>> >> for ARM in any case, given that it will also prevent hitting the
>> >> alignment fixup handler in the kernel unnecessarily.
>> >>
>> >>> However, I don't recall Arnd's patch, it's probably buried deep in
>> >>> my mailbox.
>> >>>
>> >>
>> >> Well, unless you are considering changing the unaligned accessors from
>> >> access_ok.h to le_struct.h as a bugfix, I think we need both patches.
>> >
>> > We will soon reach v4.14-rc6 and the Armada XP and Armada 370 still not
>> > boot. I also didn't see your patch in rmk patch system.
>> >
>> > Waiting for you find a agreement an other option is to remove CONFIG_EFI
>> > from multi_v7_defconfig as I don't really see any armv7 base board using
>> > EFI.
>> >
>>
>> It is up to Russell to decide how he wants to proceed. Russell?
>
> Well, having failed to attract Arnd's attention, I've spent 20 minutes
> searching my mailbox to find it.
>
> It turns out that there was never a proper patch from Arnd - it was a
> patch in pastebin.  It's not ARM specific either, it's an asm-generic
> change, for which Arnd is the maintainer for.
>
> I've just replied to that old thread and I've included Gregory and some
> PXA folk who are also having alignment problems in the decompressor.  It
> could all be due to this same issue.
>
> There's also one additional factor that hasn't been considered, and I'm
> scared to point it out, but:
>
> 1. Does Arnd's patch fix the PXA problem as well?
>

I don't think it will help configs that don't have
HAVE_EFFICIENT_UNALIGNED_ACCESS set, given that they don't use
access_ok.h in the first place.

> 2. What is the performance impact of Arnd's fix?
>

Well, given that we may be relying on the alignment fixup handler to
fix up kernel accesses, the performance impact could actually be
favorable in some cases. But I don't have any numbers, nor do I have
access to a representative sampling of ARM hardware so I can't be of
any help here, unfortunately.

-- 
Ard.