Aarch64 kernel with 32bit userspace question

[Marek Vasut]

On 02/10/2017 01:39 PM, Arnd Bergmann wrote:
> On Thursday, February 9, 2017 9:38:41 PM CET Marek Vasut wrote:
>>>
>>> The default kernel headers_install will want to place the headers into
>>> <includepath>/asm along side <includepath>/asm-generic and
>>> <includepath>/linux which is not what modern ARM distros want.
>>
>> Thanks for all the help, it at least helped me get a better picture how
>> the multilib stuff works on arm/aarch64 .
>>
>> It turns out that OE is not yet able to generate multilib sdk, while it
>> is able to generate multilib system image. Therefore, while I had two
>> different compilers, only one sysroot was installed (aarch64 one) and
>> both were pointing into it. The 32bit compiler used the wrong headers,
>> so I ran into this issue.  I'll have to drill into the OE further to
>> figure out the proper solution.
> 
> It seems the support for biarch headers was removed from the kernel
> a few years before arm64 got merged: https://lkml.org/lkml/2008/6/30/467
> 
> You could still use "make headers_install_all" in place of
> "make headers_install" in 

Whoa, I didn't know about this trick, nice :)

> http://git.yoctoproject.org/cgit.cgi/poky/plain/meta/recipes-kernel/linux-libc-headers/linux-libc-headers.inc
> but you still have to figure out how to find the right headers,
> either by moving the two asm directories to /usr/{arm,aarch64}-linux-gnu/include/asm
> or by doing the same trick that we had before the 2008 patch.

Well, I think I will wait for the multilib support to be fixed in OE
(someone is already working on it). Until then, I will stick with 32bit
userspace, which should be good enough for now.

Thanks for the help!

-- 
Best regards,
Marek Vasut