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    SubjectRe: [tip:x86/seves] BUILD SUCCESS WITH WARNING e6eb15c9ba3165698488ae5c34920eea20eaa38e
    On Tue, Sep 15, 2020 at 05:50:54PM -0400, Arvind Sankar wrote:
    > On Tue, Sep 15, 2020 at 10:49:12PM +0200, Borislav Petkov wrote:
    > >
    > > (Btw, clang doesn't need to add that "xor %eax,%eax" - panic() should not be
    > > returning, ever. :-))
    > >
    >
    > I think this is because panic() is varargs, and clang doesn't support
    > gcc's -mskip-rax-setup. The normal ABI requires the caller to set RAX to
    > the number of arguments in vector registers.
    >
    > https://patchwork.ozlabs.org/project/gcc/patch/20141218131150.GA32638@intel.com/

    Ah, good point. Found this in the ABI doc:

    "For calls that may call functions that use varargs or stdargs
    (prototype-less calls or calls to functions containing ellipsis (...) in
    the declaration) %al is used as hidden argument to specify the number of
    vector registers used. The contents of %al do not need to match exactly
    the number of registers, but must be an upper bound on the number of
    vector registers used and is in the range 0–8 inclusive."

    Thx.

    --
    Regards/Gruss,
    Boris.

    https://people.kernel.org/tglx/notes-about-netiquette

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