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    SubjectRe: [PATCH v17 03/15] arm64: Introduce prctl() options to control the tagged user addresses ABI
    On Wed, Jun 12, 2019 at 01:43:20PM +0200, Andrey Konovalov wrote:
    > From: Catalin Marinas <catalin.marinas@arm.com>
    >
    > It is not desirable to relax the ABI to allow tagged user addresses into
    > the kernel indiscriminately. This patch introduces a prctl() interface
    > for enabling or disabling the tagged ABI with a global sysctl control
    > for preventing applications from enabling the relaxed ABI (meant for
    > testing user-space prctl() return error checking without reconfiguring
    > the kernel). The ABI properties are inherited by threads of the same
    > application and fork()'ed children but cleared on execve().
    >
    > The PR_SET_TAGGED_ADDR_CTRL will be expanded in the future to handle
    > MTE-specific settings like imprecise vs precise exceptions.
    >
    > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

    A question for the user-space folk: if an application opts in to this
    ABI, would you want the sigcontext.fault_address and/or siginfo.si_addr
    to contain the tag? We currently clear it early in the arm64 entry.S but
    we could find a way to pass it down if needed.

    --
    Catalin

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