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    SubjectRe: [PATCH 1/1] Allow i386 crash kernels to handle x86_64 dumps
    On Thu, Mar 15, 2007 at 10:25:36AM +0530, Vivek Goyal wrote:
    > On Thu, Mar 15, 2007 at 10:46:38AM +0900, Horms wrote:
    > > On Wed, Mar 14, 2007 at 05:00:09PM +0000, Ian Campbell wrote:
    > > > The specific case I am encountering is kdump under Xen with a 64 bit
    > > > hypervisor and 32 bit kernel/userspace. The dump created is a 64 bit due
    > > > to the hypervisor but the dump kernel is 32 bit to match the domain 0
    > > > kernel.
    > > >
    > > > It's possibly less likely to be useful in a purely native scenario but I
    > > > see no reason to disallow it.
    > >
    > > For native Linux, would this cover the case where the pre-crash kernel
    > > is 64bit and the crashdump (post-crash) kernel is 32bit?
    > >
    >
    > I think so. Though I have never tried this.
    >
    > > > Signed-off-by: Ian Campbell <ian.campbell@xensource.com>
    > > >
    > > > --- pristine-linux-2.6.18/include/asm-i386/elf.h 2006-09-20 04:42:06.000000000 +0100
    > > > +++ linux-2.6.18-xen/include/asm-i386/elf.h 2007-03-14 16:42:30.000000000 +0000
    > > > @@ -36,7 +36,7 @@
    > > > * This is used to ensure we don't load something for the wrong architecture.
    > > > */
    > > > #define elf_check_arch(x) \
    > > > - (((x)->e_machine == EM_386) || ((x)->e_machine == EM_486))
    > > > + (((x)->e_machine == EM_386) || ((x)->e_machine == EM_486) || ((x)->e_machine == EM_X86_64))
    >
    > But I think changing this macro might run into issues. It is being used at
    > few places in kernel, for example while loading module. This will essentially
    > mean that we allow loading 64bit x86_64 modules on 32bit i386 systems?
    >
    > Similarly, load_elf_interp() is using it, again will we allow loading a
    > interp written for X86_64 on a 32bit i386 machine?
    >
    > Should we create a separate macro something like elf_check_allowed_arch(),
    > to take care of such corner cases?

    That sounds reasonable to me. Though perhaps it could just be
    kexec_elf_check_arch() for now, as I don't think there are any
    other consumers of it.

    --
    Horms
    H: http://www.vergenet.net/~horms/
    W: http://www.valinux.co.jp/en/

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