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Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions

From Ingo Molnar <mingo@kernel.org>
Newsgroups linux.kernel
Subject Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions
Date 2017-07-28 12:00 +0200
Message-ID <u8adS-247-39@gated-at.bofh.it> (permalink)
References <u5fMK-5hG-23@gated-at.bofh.it> <u5DvI-3Ew-3@gated-at.bofh.it> <u5Gaf-5lR-35@gated-at.bofh.it> <u6LKy-5uV-23@gated-at.bofh.it>
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* Matt Fleming <matt@codeblueprint.co.uk> wrote:

> On Fri, 21 Jul, at 09:19:56PM, Baoquan He wrote:
> >
> > There are places where the efi map is getting and used like this. E.g
> > in efi_high_alloc() of drivers/firmware/efi/libstub/efi-stub-helper.c.
> > EFI developers worry the size of efi_memory_desc_t could not be the same
> > as e->efi_memdesc_size?
> > 
> > Hi Matt,
> > 
> > Could you help have a look at this?
> 
> You're exactly right. The code guards against the size of the
> efi_memory_desc_t struct changing. The UEFI spec says to traverse the
> memory map this way.

This is not obvious and looks pretty ugly as well, and open coded in several 
places.

At minimum we should have an efi_memdesc_ptr(efi, i) wrapper inline (or so) that 
gives us the entry pointer, plus a comment that points out that ->memdesc_size 
might not be equal to sizeof(efi_memory_memdesc_t).

Thanks,

	Ingo

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Thread

[PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-20 11:20 +0200
  Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Ingo Molnar <mingo@kernel.org> - 2017-07-21 12:40 +0200
    Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-21 15:30 +0200
      Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Ingo Molnar <mingo@kernel.org> - 2017-07-21 19:40 +0200
        Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-22 01:50 +0200
      Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Matt Fleming <matt@codeblueprint.co.uk> - 2017-07-24 15:40 +0200
        Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-25 02:30 +0200
        Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-28 10:10 +0200
        Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Ingo Molnar <mingo@kernel.org> - 2017-07-28 12:00 +0200
          Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-28 12:20 +0200
            Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-28 12:40 +0200
          Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-28 13:30 +0200
  Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Ingo Molnar <mingo@kernel.org> - 2017-07-21 12:40 +0200
    Re: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be  randomized in mirror regions Baoquan He <bhe@redhat.com> - 2017-07-21 14:40 +0200

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