linux-kernel - Re: Build/qemu test results for v4.18-rc2

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Date:   Tue, 26 Jun 2018 08:40:37 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>, mcroce@...hat.com,
        sbrivio@...hat.com, David Miller <davem@...emloft.net>
Subject: Re: Build/qemu test results for v4.18-rc2

On Mon, Jun 25, 2018 at 9:31 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> Yes, looks like they tried again with c24fb5e68ebf ("bpfilter: fix user
> mode helper cross compilation"), but it still doesn't work.

That was a different issue - an actual cross-build environment.

The problem on x86-64 cross-building to i386 is that the *compiler* is
the same, but the flags are not, and the games the Makefile plays
aren't sufficient. It plays with changing HOSTCC to CC in order to get
he right target compiler, but since the difference between i386 and
x86-64 is not the compiler but the "-m64" in the cflags, it doesn't
actually do what it intended to do.

We'll get it sorted, I think. The problem is that the current Makefile
infrastructure doesn't have any support for building a stand-alone
binary for the target, which is why the code plays games with HOSTCC
(to use the infrastructure that does binaries for the host, but using
the target compiler).

So it's all a bit hacky right now, and the hacks come back and bite us
for the x86-64/i386 case.

               Linus