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    SubjectRe: [PATCH v3 0/4] Allow customizable random offset to mmap_base address.
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    On 11/24/2015 04:39 PM, Andrew Morton wrote:

    > mips, powerpc and s390 also implement arch_mmap_rnd(). Are there any
    > special considerations here, or it just a matter of maintainers wiring
    > it up and testing it?

    I had not yet looked at those at all, as I had no way to do even a
    rudimentary "does it boot" test and opted to post v3 first. Upon first
    glance, it should just be a matter of wiring it up:

    Mips is divided into 12/16 bits for 32/64 bit (assume baseline 4k page)
    w/COMPAT kconfig, powerpc is 11/18 w/COMPAT, s390 is 11/11 w/COMPAT.
    s390 is a bit strange as COMPAT is for a 31-bit address space, although
    is_32bit_task() is used to determine which mask to use, and the mask
    itself for 64-bit only introduces 11 bits of entropy, but while still
    affecting larger chunks of the address space (mask is 0x3ff80, resulting
    in an effective 0x7ff shift of PAGE_SIZE + 7 bits).

    I could go ahead and add these to patchset v4 and as with the previous
    architectures, rely on feedback from arch-specific maintainers to help
    tune and test the values.

    -Dan


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