[yocto] x86_64 kernel with i586 userland plus SDK?

[Bruce Ashfield]

On 12/17/18 8:50 AM, Richard Weinberger wrote:
> Bruce,
> 
> On Mon, Dec 17, 2018 at 2:47 PM Bruce Ashfield
> <bruce.ashfield at windriver.com> wrote:
>>> Yocto seems to try a different approach.
>>> When I use qemux86-64.conf with DEFAULTTUNE being "i586" it generates a 32bit
>>> toolchain by default.
>>>
>>> Build Configuration:
>>> BB_VERSION           = "1.38.0"
>>> BUILD_SYS            = "x86_64-linux"
>>> NATIVELSBSTRING      = "universal"
>>> TARGET_SYS           = "i686-poky-linux"
>>> MACHINE              = "myqemux86-64"
>>> DISTRO               = "poky"
>>> DISTRO_VERSION       = "2.5.1"
>>> TUNE_FEATURES        = "m32 i586"
>>>
>>> What I need is a x86_64-poky-linux toolchain with -m32 set for everything except
>>> kernel (and modules).
>>
>> For the most part the kernel builds do not take any flags from the
>> outside, i.e. they are all generated based on the kernel build
>> structure, not what is calling the build. (unless you bury flags
>> into the definition of $(CC), etc, but I wouldn't recommend that.
>>
>> So if you have a 64 bit capable toolchain, have a 64 bit configured
>> kernel (i.e. CONFIG_64BIT=y), are passing -m32 to usespace .. the
>> kernel really should build 64bit.
> 
> This was my plan, but yocto always create a 32bit toolchain when
> it set DEFAULTTUNE to i586 for a 64bit machine.
> 
>> Have you tried that and are seeing the kernel still be built with the
>> 32bit toolchain ?
> 
> Yes, it builds with i686-poky-linux. :-(

It's Monday, and I've only had half a coffee .. so bear with me. When
I see i686, I'd expect that without -m32 it is generating 64bit by
default .. so there's definitely a -m32 sneaking into the definition of
CC for the kernel build ?

Do you have a dump of the kernel build line that I could see ?

Bruce

>