Re: [Xen-devel] Xen 3.1 - Can't run Fedora Core 1 PV

[Nick Craig-Wood <nick@xxxxxxxxxxxxxx>]

On Fri, Jul 13, 2007 at 07:31:32AM +0100, Keir Fraser wrote:
> On 12/7/07 18:51, "Ian Campbell" <Ian.Campbell@xxxxxxxxxxxxx> wrote:
> 
> >> The above fails for xen 3.1 but succeeds (you get a shell) for xen 3.0.4 
> >> and
> >> 3.0.3
> > 
> > FC1 had some odd stuff going on with the vdso -- it comes up any time
> > upstream tries to touch the compat vdso code.
> > 
> > You could try enabling/disabling COMPAT_VDSO in your kernel
> > configuration, see what happens.
> > 
> > It'd also be interesting to know which libc is getting linked in within
> > the chroot.
> 
> Yes, it's definitely VDSO related as it crashes in linux-gate.so. 3.0.4
> kernels work just fine with 3.1, so that is the correct fix for this
> situation.

I've now tried this.

Firstly the COMPAT_VDSO wasn't appearing in the menu

# from arch/i386/Kconfig 

config COMPAT_VDSO
        bool "Compat VDSO support"
        depends on !X86_XEN
        default y
        help
          Map the VDSO to the predictable old-style address too.
        ---help---
          Say N here if you are running a sufficiently recent glibc
          version (2.3.3 or later), to remove the high-mapped
          VDSO mapping and to exclusively use the randomized VDSO.

          If unsure, say Y.

endmenu

I removed the "depends on !X86_XEN" line, configured COMPAT_VDSO but
the build then failed here

  CC      arch/i386/kernel/asm-offsets.s
arch/i386/kernel/asm-offsets.c: In function 'foo':
arch/i386/kernel/asm-offsets.c:79: warning: asm operand 0 probably doesn't 
match constraints
arch/i386/kernel/asm-offsets.c:79: error: impossible constraint in 'asm'

So I guess it was there for a reason!  Configuring COMPAT_VDSO off
causes it to compile again.

Any ideas?

Thanks

-- 
Nick Craig-Wood <nick@xxxxxxxxxxxxxx> -- http://www.craig-wood.com/nick

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