LE and BE build for the same machine in Yocto

LE and BE build for the same machine in Yocto

[Zhenhua Luo]

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Hi all,

If the multilib feature is enabled in Yocto, two cross-compile gcc binaries will be generated to do both 32b and 64b build for the same machine.  Currently we have requirement to build LE u-boot and BE kernel/rootfs for the same machine, may I know if there is similar multilib mechanism in Yocto to support BE and LE build for the same machine?


Best Regards,

Zhenhua

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Re: LE and BE build for the same machine in Yocto

[Richard Purdie]

On Fri, 2016-03-25 at 06:07 +0000, Zhenhua Luo wrote:
> If the multilib feature is enabled in Yocto, two cross-compile gcc
> binaries will be generated to do both 32b and 64b build for the same
> machine.  Currently we have requirement to build LE u-boot and BE
> kernel/rootfs for the same machine, may I know if there is similar
> multilib mechanism in Yocto to support BE and LE build for the same
> machine?

If u-boot doesn't need any support libs, the existing compiler can
likely cope with that. If you need libgcc, then you will need multilib.

I'd like to get to a point where we can support this using multilib
however it might not all work correctly today. It would be interesting
to try it! The intent is to get to the point where it would work but
its not currently a priority as not many people have been asking for
it.

Cheers,

Richard

Re: LE and BE build for the same machine in Yocto

[Khem Raj]

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> On Mar 25, 2016, at 1:26 AM, Richard Purdie <richard.purdie@linuxfoundation.org> wrote:
> 
> On Fri, 2016-03-25 at 06:07 +0000, Zhenhua Luo wrote:
>> If the multilib feature is enabled in Yocto, two cross-compile gcc
>> binaries will be generated to do both 32b and 64b build for the same
>> machine.  Currently we have requirement to build LE u-boot and BE
>> kernel/rootfs for the same machine, may I know if there is similar
>> multilib mechanism in Yocto to support BE and LE build for the same
>> machine?
> 
> If u-boot doesn't need any support libs, the existing compiler can
> likely cope with that. If you need libgcc, then you will need multilib.
> 
> I'd like to get to a point where we can support this using multilib
> however it might not all work correctly today. It would be interesting
> to try it! The intent is to get to the point where it would work but
> its not currently a priority as not many people have been asking for
> it.
> 

Do you mean having BE/LE as a multilib option ? that might be a possibility
and would probably make sense for this kind of limited scenario.

u-boot, kernel, are standalone apps, but some of them do need gcc runtime at
various stages, some need startup files some need libgcc as well. Good thing
is they won’t require libgcc_s but static libgcc, which can come from gcc-cross area and
we don’t have to worry about packaging it for target. I wonder
if we could tool the multilib configuration of cross-gcc separately from the rootfs

however, that might work for startup files since they are only needed during build
and are not packaged into target package like libgcc is.

If we can limit ourselves to startup files and static libgcc then a solution could
become possible.

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Re: LE and BE build for the same machine in Yocto

[Zhenhua Luo]

Hi Richard and Khem, 

Thanks for your comments. 

I have tried to build the LE u-boot for BE target in Yocto, the u-boot can be built successfully, I only need to pass "-mlittle-endian" for cross gcc and pass " -EL" for cross ld. 


Best Regards,

Zhenhua

> -----Original Message-----
> From: Khem Raj [mailto:raj.khem@gmail.com]
> Sent: Friday, March 25, 2016 11:44 PM
> To: Richard Purdie <richard.purdie@linuxfoundation.org>
> Cc: Zhenhua Luo <zhenhua.luo@nxp.com>; openembedded-
> core@lists.openembedded.org
> Subject: Re: [OE-core] LE and BE build for the same machine in Yocto
> 
> 
> > On Mar 25, 2016, at 1:26 AM, Richard Purdie
> <richard.purdie@linuxfoundation.org> wrote:
> >
> > On Fri, 2016-03-25 at 06:07 +0000, Zhenhua Luo wrote:
> >> If the multilib feature is enabled in Yocto, two cross-compile gcc
> >> binaries will be generated to do both 32b and 64b build for the same
> >> machine.  Currently we have requirement to build LE u-boot and BE
> >> kernel/rootfs for the same machine, may I know if there is similar
> >> multilib mechanism in Yocto to support BE and LE build for the same
> >> machine?
> >
> > If u-boot doesn't need any support libs, the existing compiler can
> > likely cope with that. If you need libgcc, then you will need multilib.
> >
> > I'd like to get to a point where we can support this using multilib
> > however it might not all work correctly today. It would be interesting
> > to try it! The intent is to get to the point where it would work but
> > its not currently a priority as not many people have been asking for
> > it.
> >
> 
> Do you mean having BE/LE as a multilib option ? that might be a possibility and
> would probably make sense for this kind of limited scenario.
> 
> u-boot, kernel, are standalone apps, but some of them do need gcc runtime at
> various stages, some need startup files some need libgcc as well. Good thing is
> they won’t require libgcc_s but static libgcc, which can come from gcc-cross
> area and we don’t have to worry about packaging it for target. I wonder if we
> could tool the multilib configuration of cross-gcc separately from the rootfs
> 
> however, that might work for startup files since they are only needed during
> build and are not packaged into target package like libgcc is.
> 
> If we can limit ourselves to startup files and static libgcc then a solution could
> become possible.