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    SubjectRe: [PATCH v19 02/15] arm64: Introduce prctl() options to control the tagged user addresses ABI
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    On 8/1/19 5:38 AM, Kevin Brodsky wrote:
    > This patch series only changes what is allowed or not at the syscall
    > interface. It does not change the address space size. On arm64, TBI (Top
    > Byte Ignore) has always been enabled for userspace, so it has never been
    > possible to use the upper 8 bits of user pointers for addressing.

    Oh, so does the address space that's available already chop that out?

    > If other architectures were to support a similar functionality, then I
    > agree that a common and more generic interface (if needed) would be
    > helpful, but as it stands this is an arm64-specific prctl, and on arm64
    > the address tag is defined by the architecture as bits [63:56].

    It should then be an arch_prctl(), no?

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