Re: [RFC PATCH 00/13][V3] kexec: A new system call to allow in kernel loading

Vivek Goyal
2014-06-12T12:37:46Z

On Thu, Jun 12, 2014 at 01:42:03PM +0800, Dave Young wrote:
> On 06/03/14 at 09:06am, Vivek Goyal wrote:
> > Hi,
> >
> > This is V3 of the patchset. Previous versions were posted here.
> >
> > V1: https://lkml.org/lkml/2013/11/20/540
> > V2: https://lkml.org/lkml/2014/1/27/331
> >
> > Changes since v2:
> >
> > - Took care of most of the review comments from V2.
> > - Added support for kexec/kdump on EFI systems.
> > - Dropped support for loading ELF vmlinux.
> >
> > This patch series is generated on top of 3.15.0-rc8. It also requires a
> > two patch cleanup series which is sitting in -tip tree here.
> >
> > https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/log/?h=x86/boot
> >
> > This patch series does not do kernel signature verification yet. I plan
> > to post another patch series for that. Now bzImage is already signed
> > with PKCS7 signature I plan to parse and verify those signatures.
> >
> > Primary goal of this patchset is to prepare groundwork so that kernel
> > image can be signed and signatures be verified during kexec load. This
> > should help with two things.
> >
> > - It should allow kexec/kdump on secureboot enabled machines.
> >
> > - In general it can help even without secureboot. By being able to verify
> > kernel image signature in kexec, it should help with avoiding module
> > signing restrictions. Matthew Garret showed how to boot into a custom
> > kernel, modify first kernel's memory and then jump back to old kernel and
> > bypass any policy one wants to.
> >
> > Any feedback is welcome.
>
> Hi, Vivek
>
> For efi ioremapping case, in 3.15 kernel efi runtime maps will not be saved
> if efi=old_map is used. So you need detect this and fail the kexec file load.
>
> Otherwise the patchset works for me.

Thanks Dave. I will make sure that in case of old mapping, kexec loading
fails. I don't want to be supporting that old "noefi" mode in this new
system call. Even SGI is planning to fix their firmware to support
1:1 mapping.

Thanks
Vivek