Messages in this thread | | | Date | Thu, 15 Jun 2017 17:20:32 +0800 | From | 'Baoquan He' <> | Subject | Re: [RFC][PATCH 0/2] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions if existed |
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On 06/15/17 at 08:34am, Izumi, Taku wrote: > Dear Baoquan, > > > > Our customer reported that Kernel text may be located on non-mirror > > > region (movable zone) when both address range mirroring feature and > > > KASLR are enabled. > > I know your customer :)
LOL, have to agree.
> > > The method is very simple. If efi is enabled, just iterate all efi > > > memory map and pick up mirror region to process for adding candidate > > > of slot. If efi disabled or no mirror region existed, still process > > > e820 memory map. This won't bring much efficiency loss, at worst we > > > just go through all efi memory maps and found no mirror. > > > > > > One question: > > > From code, though mirror regions are existed, they are meaningful only > > > if kernelcore=mirror kernel option is specified. Not sure if my > > > understanding is correct. > > Your understanding is almost correct. > Only when "kernelcore=mirror" specified, the above procedure works. > But, if mirrored regions are existed, bootmem allocator tries to > allocate from mirrored region independently of "kerenelcore=mirror" option. > > So, IMHO, kernel text is important, so putting it to mirrored (more reliable) > region is reasonable whether or not "kernelcore=mirror" is specified.
Ah, yeah, thanks for telling. So at boot time memblock will put mirror region in highest priority to allocate. Then let me remove the kernelcore=mirror handling code, the process_efi_entry will be simpler.
commit a3f5bafcc04aaf62990e0cf3ced1cc6d8dc6fe95 Author: Tony Luck <tony.luck@intel.com> Date: Wed Jun 24 16:58:12 2015 -0700
mm/memblock: allocate boot time data structures from mirrored memory
> > Anyway thanks for submitting patch. > We have Address Range Mirroring capable machine, so we'll test your patch.
Thanks a lot for help, Yasuaki Ishimatsu said he also will loan me a testing machine when it's available.
Thanks Baoquan
> > > > > > > > NOTE: > > > I haven't got a machine with efi mirror region enabled, so only test > > > the > > > e820 map processing case and the case of no mirror region on efi machine. > > > So set this as a RFC patchset, will post formal one after above > > > question is made clear and mirror issue test passed. > > > > > > Baoquan He (2): > > > x86/boot/KASLR: Adapt process_e820_entry for all kinds of memory map > > > x86/boot/KASLR: Restrict kernel to be randomized in mirror regions if > > > existed > > > > > > arch/x86/boot/compressed/kaslr.c | 129 > > > +++++++++++++++++++++++++++++++-------- > > > 1 file changed, 104 insertions(+), 25 deletions(-) > > > > > > -- > > > 2.5.5 > > > >
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