[OE-core] kernel miscompilation with gcc 4.8 for ARMv5

[Bruce Ashfield]

On Wed, Jul 10, 2013 at 11:30 AM, Enrico Scholz
<enrico.scholz at sigma-chemnitz.de> wrote:
> Bruce Ashfield <bruce.ashfield-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org>
> writes:
>
>>> Applying two upstream kernel commits
>>> 455bd4c430b0c0a361f38e8658a0d6cb469942b5 (ARM: 7668/1: fix
>>> memset-related crashes caused by recent GCC (4.7.2) optimizations) and
>>> 418df63adac56841ef6b0f1fcf435bc64d4ed177 (ARM: 7670/1: fix the memset
>>> fix) seem to fix the problem for me.
>>
>> Correct. Those are the same commits you'll see on linux-yocto-3.8,
>> we've been soaking them for a while. I was waiting for LTSI and -stable
>> to pick up the changes before updating linux-yocto-3.4, but that hasn't
>> happened yet.
>>
>> If you are using linux-yocto-3.4 and can confirm that it boots for you
>> with those patches,
>
> Sorry, I am using a more or less vanilla 3.4 kernel.  Patches fix
> the problem there (device boots) and (after knowing about them) the
> problematic code is easy to spot:

No worries. I can spot the fix, since we already did this for the 3.8 kernel. I
was just no where near my targets at the moment .. and if I had an independent
report that things boot, I'd go ahead and push my 3.8 fixes (ported to
3.4) .. which
I may do anyway, since I can drop them when they cycle through -stable and
LTSI.

Cheers,

Bruce

>
> $ arm-linux-gnueabi-objdump  -d mm/slub.o
>
> 000014c4 <init_object>:
>     ...
>     14fc:       e1a00001        mov     r0, r1
>     1500:       e3a0106b        mov     r1, #107        ; 0x6b
>     1504:       ebfffffe        bl      0 <memset>
>     1508:       e1a03000        mov     r3, r0          <<<<<<<
>     150c:       e5942010        ldr     r2, [r4, #16]
>     1510:       e3e0105a        mvn     r1, #90 ; 0x5a
>     1514:       e0832002        add     r2, r3, r2
>     1518:       e5421001        strb    r1, [r2, #-1]
>
> With unpatched memset, 'r0' points to end of buffer.
>
>
> Enrico
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--
"Thou shalt not follow the NULL pointer, for chaos and madness await
thee at its end"