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Re: [PATCH v3 2/2] x86/efi: clean up dead code around efi_reserve_boot_services()

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On 07/26/17 at 12:12am, Naoya Horiguchi wrote:
> On Mon, Jul 24, 2017 at 02:20:44PM +0100, Matt Fleming wrote:
> > On Mon, 10 Jul, at 02:51:36PM, Naoya Horiguchi wrote:
> > > EFI_BOOT_SERVICES_{CODE|DATA} regions never overlap the kernel now,
> > > so we can clean up the check in efi_reserve_boot_services().
> > > 
> > > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> > > ---
> > >  arch/x86/platform/efi/quirks.c | 23 +----------------------
> > >  1 file changed, 1 insertion(+), 22 deletions(-)
> > 
> > Is this true for kernels not using KASLR? 
> 
> Thank you for pointing out this. It's not true depending on memmap layout.
> If a firmware does not define the memory around the kernel address
> (0x1000000 or CONFIG_PHYSICAL_START) as EFI_BOOT_SERVICES_*, no overlap
> happens.  That's true in my testing server, but I don't think that we can
> expect it generally.
> 
> So I think of adding some assertion in the patch 1/2 to detect this overlap
> in extract_kernel() even for no KASLR case.

EFI_BOOT_SERVICES_* memory are collected as e820 region of
E820_TYPE_RAM, how can we guarantee kernel won't use them after jumping
into the running kernel whether KASLR enabled or not? We can only wish
that EFI firmware engineer don't put EFI_BOOT_SERVICES_* far from
0x1000000 where normal kernel is loaded.

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Re: [PATCH v3 2/2] x86/efi: clean up dead code around  efi_reserve_boot_services() Matt Fleming <matt@codeblueprint.co.uk> - 2017-07-24 15:30 +0200
  Re: [PATCH v3 2/2] x86/efi: clean up dead code around  efi_reserve_boot_services() Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> - 2017-07-26 02:20 +0200
    Re: [PATCH v3 2/2] x86/efi: clean up dead code around  efi_reserve_boot_services() Baoquan He <bhe@redhat.com> - 2017-07-26 03:20 +0200
      Re: [PATCH v3 2/2] x86/efi: clean up dead code around  efi_reserve_boot_services() Baoquan He <bhe@redhat.com> - 2017-07-26 03:40 +0200
        [PATCH] x86/boot: check overlap between kernel and  EFI_BOOT_SERVICES_* Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> - 2017-07-28 09:00 +0200
          Re: [PATCH] x86/boot: check overlap between kernel and  EFI_BOOT_SERVICES_* kbuild test robot <lkp@intel.com> - 2017-07-29 12:10 +0200
          Re: [PATCH] x86/boot: check overlap between kernel and  EFI_BOOT_SERVICES_* kbuild test robot <lkp@intel.com> - 2017-07-29 15:10 +0200
          [RFC PATCH] x86/boot: efi_kernel_boot_services_overlap can be static kbuild test robot <lkp@intel.com> - 2017-07-29 15:10 +0200

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