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    SubjectRe: [PATCH 31/32] x86, pkeys: execute-only support
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    On 12/14/2015 12:05 PM, Kees Cook wrote:
    > On Mon, Dec 14, 2015 at 11:06 AM, Dave Hansen <dave@sr71.net> wrote:
    >> > From: Dave Hansen <dave.hansen@linux.intel.com>
    >> > Protection keys provide new page-based protection in hardware.
    >> > But, they have an interesting attribute: they only affect data
    >> > accesses and never affect instruction fetches. That means that
    >> > if we set up some memory which is set as "access-disabled" via
    >> > protection keys, we can still execute from it.
    ...
    >> > I haven't found any userspace that does this today.
    > To realistically take advantage of this, it sounds like the linker
    > would need to know to keep bss and data page-aligned away from text,
    > and then set text to PROT_EXEC only?
    >
    > Do you have any example linker scripts for this?

    Nope. My linker-fu is weak.

    Can we even depend on the linker by itself? Even if the sections were
    marked --x, we can't actually use them with those permissions unless we
    have protection keys.

    Do we need some special tag on the section to tell the linker to map it
    as --x under some conditions and r-x for others?



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