Re: [Adeos-main] [Vortx86DX] What's wrong with kernels upper than 2.6.30.10 ?

[Philippe Gerum <rpm@xenomai.org>]

On Fri, 2010-04-16 at 00:00 +0200, Gilles DOFFE wrote:
> Hello,
> 
> I try to install a real-time Linux kernel on a Roboard based on a
> Vortex86DX (a x486 with TSC).
> 
> All works fine with :
> Linux Kernel 2.6.30.10
> Xenomai 2.5.1
> Adeos patch adeos-ipipe-2.6.30.8-x86-2.4-09.patch
> 
> But, for all kernels upper or equal to 2.6.31, I always get a double
> fault when testing WP bit. I have this double fault just after that :
> 
> Checking if this processor honours the WP bit even in supervisor
> mode...
> 
> I traced with some simple printk that the problem occurs in this
> function, at the end or after the call of fix_to_virt  :
> 
> static noinline int do_test_wp_bit(void)
> {
>         char tmp_reg;
>         int flag;
> 
>         __asm__ __volatile__(
>                 "       movb %0, %1     \n"
>                 "1:     movb %1, %0     \n"
>                 "       xorl %2, %2     \n"
>                 "2:                     \n"
>                 _ASM_EXTABLE(1b,2b)
>                 :"=m" (*(char *)fix_to_virt(FIX_WP_TEST)),
>                  "=q" (tmp_reg),
>                  "=r" (flag)
>                 :"2" (1)
>                 :"memory");
> 
>         return flag;
> }
> 
> I'm (quasi) sure that the problem is not that function, due to it
> works when the kernel is not patched.
> But where should I search ?

Try backporting these two 2.6.32 patches to your kernel; this should be
straightforward:
http://git.denx.de/?p=ipipe-2.6.git;a=commit;h=576f57f82dfd6c3ac285b0af76e5e0ce617679ba
http://git.denx.de/?p=ipipe-2.6.git;a=commit;h=a250e984a76fd327a0d8cfada5290b27e99f1e4d


> 
> Can you give me some indications ?
> 
> Thanks,
> Gilles 
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-- 
Philippe.