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    SubjectRe: [tip: x86/core] objtool: Find unused ENDBR instructions
    On Thu, Mar 17, 2022 at 03:22:54PM -0700, Josh Poimboeuf wrote:
    > On Tue, Mar 15, 2022 at 03:39:52PM +0000, David Laight wrote:
    > > From: Peter Zijlstra
    > > >
    > > > objtool: Find unused ENDBR instructions
    > > >
    > > > Find all ENDBR instructions which are never referenced and stick them
    > > > in a section such that the kernel can poison them, sealing the
    > > > functions from ever being an indirect call target.
    > >
    > > Thought, what happens if the only indirect call is from
    > > code in a module?
    >
    > Then <boom>, I guess. Is it safe to assume in-tree modules don't need
    > to do indirect calls to exported functions? I guess we'll find out :-)

    So exported functions will keep their ENDBR. Specifically, their address
    is taken by the EXPORT_SYMBOL thing.

    Sealing them might work, but let's not do that just now ;-)

    Any unexported function discovered through kallsyms OTOH... those
    deservedly will go *boom*.

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