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Date:   Tue, 8 Mar 2022 15:51:41 +0100
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Subject: Re: hppa vDSO and compiler (non-)support
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To:     Jiri Slaby <jirislaby@kernel.org>,
        "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>,
        linux-parisc@vger.kernel.org,
        Linux kernel mailing list <linux-kernel@vger.kernel.org>
References: <d2713ae1-0ca5-9e5a-b7d2-b7d0f1f5614a@kernel.org>
From:   Helge Deller <deller@gmx.de>
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Hi Jiri,

Thanks for testing on parisc!

On 3/8/22 12:06, Jiri Slaby wrote:
> since the "parisc: Add vDSO support" commit, I can no longer cross-build=
 a hppa kernel. I see two issues:
>
> 1) CROSS32_COMPILE detection doesn't work here, as openSUSE provides hpp=
a-suse-linux-* binaries. It's easy to overcome by "CROSS32_COMPILE=3Dhppa-=
suse-linux-"

How is it handled for other platforms like s390x?
Would it make sense to add the detection for SUSE too?

> 2) openSUSE doesn't provide any libc for hppa. So gcc doesn't provide li=
bgcc.a and the build of vDSO fails.

libgcc.a comes with the compiler, I don't think you need libc for that.
I'm currently installing opensuse to try myself though...

> So could vDSO be optional on hppa via KConfig?
The vDSO is one of the first things which is built during kernel build pro=
cess.
This is why you fail.
Making it optional doesn't make sense, because then the kernel wouldn't be=
 able
to start the user space processes.

> I used to use the cross compiler to at least compile-check the following=
 =C2=A0tty drivers:
> arch/parisc/kernel/pdc_cons.o
> drivers/tty/serial/mux.o
> drivers/tty/serial/8250/8250_gsc.o

I assume you never built a full kernel, but stopped when building those mo=
dules?
Without libgcc.a the kernel itself wouldn't have linked before either.

Helge