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Date: Mon, 12 Sep 2011 15:05:25 +0200
From: Daniel Cegiełka <daniel.cegielka@...il.com>
To: owl-dev@...ts.openwall.com
Subject: Re: gcc 4.6.x and kernel-2.6.18-ovz

I remember that from some version of gcc (4.5?) there was a problem
with kernel compilation. The reason was that gcc checking code more
carefully and did not want to accept certain parts of the kernel.
Kernel 2.6.18 is quite old and maybe this is just such a situation.

regards,
daniel


2011/9/12 Vasiliy Kulikov <segoon@...nwall.com>:
> Solar,
>
> There is an issue with compiling RHEL5/OpenVZ kernel with gcc 4.6.1:
>
>  CC      arch/i386/kernel/kvmclock.o
>  SYSCALL arch/i386/kernel/vsyscall-syms.o
> gcc: error: elf_i386: No such file or directory
> make[2]: *** [arch/i386/kernel/vsyscall-syms.o] Error 1
> make[2]: *** Waiting for unfinished jobs....
>  CC      arch/i386/kernel/cpu/mtrr/main.o
>
> While this specific failure is trivial to fix, there are more of them,
> like this one:
>
>  LD      init/built-in.o
>  LD      .tmp_vmlinux1
> kernel/built-in.o: In function `.text.lock.mutex':
> mutex.c:(.sched.text+0x186b): undefined reference to `__mutex_lock_slowpath'
> mutex.c:(.sched.text+0x1875): undefined reference to `__mutex_unlock_slowpath'
> make[1]: *** [.tmp_vmlinux1] Error 1
>
> and I suspect we'll get more of weird build bugs (and runtime bugs
> perhaps) during RHEL6 kernel updates too as RHEL6 has gcc 4.4.5 (DW says
> so), but we'll have 4.6.1.
>
>
> Kir Kolyshkin suggested to use the same gcc version as RHELx has:
>
> http://bugzilla.openvz.org/show_bug.cgi?id=1801
>
> "The rule of thumb here is this: RHELx kernels are best to be compiled by gcc
> from RHELx, otherwise we can get bad results (and it happened before)."
>
>
> Probably we should use gcc 4.4.x for Owl 4.0?  Probably even not patch
> the 2.6.18 kernel and suggest users to upgrade gcc and the kernel at the
> same time.  Or patch the kernel and humble with possible runtime bugs
> until we upgrade it to RHEL6/OpenVZ, but this more time consuming.
>
> What do you think?
>
> Thanks,
>
> --
> Vasiliy
>

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