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    SubjectRe: [PATCH v6 RESEND] x86/boot/KASLR: Restrict kernel to be randomized in mirror regions
    On Fri, 28 Jul, at 07:26:03PM, Baoquan He wrote:
    > Hi Matt,
    >
    > On 07/28/17 at 11:55am, Ingo Molnar wrote:
    > >
    > > * 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).
    >
    > I can make a efi_memdesc_ptr(efi, i) wrapper as Ingo suggested and use
    > it here if you agree. Seems it might be not good to add another
    > for_each_efi_memory_desc_xxxx wrapper since there are different memmap
    > data structures in x86 boot and in general efi libstub. Or any other
    > idea?

    I think adding a wrapper is fine, but I'd suggest including the word
    "early" (or something similar) to explain that it should only be used
    during bootup -- we want everyone else to use the
    for_each_efi_memory_*() API.

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