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Date: Thu, 15 Mar 2007 11:17:26 +0530 From: Vivek Goyal <vgoyal@...ibm.com> To: Horms <horms@...ge.net.au> Cc: Ian Campbell <Ian.Campbell@...Source.com>, hbabu@...ibm.com, fastboot@...ts.osdl.org, linux-kernel@...r.kernel.org, Magnus Damm <magnus.damm@...il.com> Subject: Re: [PATCH 1/1] Allow i386 crash kernels to handle x86_64 dumps On Thu, Mar 15, 2007 at 02:07:56PM +0900, Horms wrote: > 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@...source.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. Kexec will also not allow loading an x86_64 kernel on a 32bit machine. So how about something like vmcore_elf_allowed_cross_arch()? Vmcore code can continue to check elf_check_arch() and if that fails it can invoke vmcore_elf_allowed_cross_arch() to find out what cross arch are allowed for vmcore. Thanks Vivek - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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