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    SubjectRe: [PATCH v5 1/5] arm64: Add utilities to save restore pointer authentication keys
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    Hi Amit,

    On 28/01/2019 06:58, Amit Daniel Kachhap wrote:
    > The keys can be switched either inside an assembly or such
    > functions which do not have pointer authentication checks, so a GCC
    > attribute is added to enable it.
    >
    > A function ptrauth_keys_store is added which is similar to existing
    > function ptrauth_keys_switch but saves the key values in memory.
    > This may be useful for save/restore scenarios when CPU changes
    > privilege levels, suspend/resume etc.


    > diff --git a/arch/arm64/include/asm/pointer_auth.h b/arch/arm64/include/asm/pointer_auth.h
    > index 15d4951..98441ce 100644
    > --- a/arch/arm64/include/asm/pointer_auth.h
    > +++ b/arch/arm64/include/asm/pointer_auth.h
    > @@ -11,6 +11,13 @@
    >
    > #ifdef CONFIG_ARM64_PTR_AUTH
    > /*
    > + * Compile the function without pointer authentication instructions. This
    > + * allows pointer authentication to be enabled/disabled within the function
    > + * (but leaves the function unprotected by pointer authentication).
    > + */
    > +#define __no_ptrauth __attribute__((target("sign-return-address=none")))

    The documentation[0] for this says 'none' is the default. Will this only
    take-effect once the kernel supports pointer-auth for the host? (Is this just
    documentation until then?)

    ('noptrauth' would fit with 'notrace' slightly better)


    Thanks,

    James

    [0]
    https://gcc.gnu.org/onlinedocs/gcc/AArch64-Function-Attributes.html#AArch64-Function-Attributes

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