| Date | Mon, 21 Mar 2022 17:04:28 +0100 | From | Peter Zijlstra <> | Subject | Re: linux-next: build warnings after merge of the tip tree |
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On Mon, Mar 21, 2022 at 11:28:05AM -0400, Steven Rostedt wrote: > On Mon, 21 Mar 2022 14:04:05 +0100 > Peter Zijlstra <peterz@infradead.org> wrote:
> > Also, folks, I'm thinking we should start to move to __fexit__, if CET > > SHSTK ever wants to come to kernel land return trampolines will > > insta-stop working. > > > > Hjl, do you think we could get -mfexit to go along with -mfentry ?
> int funcA () { > [..] > return funcB(); > }
> This currently works with function graph and kretprobe tracing because of > the shadow stack. Let's say we traced both funcA and funcB > > funcA: > call __fentry__ push funcA on trace-stack > > [..] > jmp funcB > > funcB: > call __fentry__ push funcB on trace-stack > > [..] call __fexit__ pop trace-stack until empty 'exit funcB' 'exit funcA'
> ret
> > That is, the current algorithm traces the end of both funcA and funcB > without issue, because of how the shadow stack works.
And it all works, no? Or what am I missing?
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