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    SubjectRe: [PATCH 18/18] arm64: implement Shadow Call Stack
    On Fri, Oct 18, 2019 at 10:13 AM Jann Horn <jannh@google.com> wrote:
    > These things should probably be __always_inline or something like
    > that? If the compiler decides not to inline them (e.g. when called
    > from scs_thread_switch()), stuff will blow up, right?

    Correct. I'll change these to __always_inline in v2. I think there
    might be other places in the kernel where not inlining a static inline
    function would break things, but there's no need to add more.

    > This is different from the intended protection level according to
    > <https://clang.llvm.org/docs/ShadowCallStack.html#security>, which
    > talks about "a runtime that avoids exposing the address of the shadow
    > call stack to attackers that can read arbitrary memory". Of course,
    > that's extremely hard to implement in the context of the kernel, where
    > you can see all the memory management data structures and all physical
    > memory.

    Yes, the security guarantees in the kernel are different as hiding
    shadow stack pointers is more challenging.

    > You might want to write something in the cover letter about what the
    > benefits of this mechanism compared to STACKPROTECTOR are in the
    > context of the kernel, including a specific description of which types
    > of attacker capabilities this is supposed to defend against.

    Sure, I'll add something about that in v2. Thanks.

    Sami

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