Messages in this thread | | | Date | Fri, 24 Mar 2017 22:07:58 +0100 | From | Peter Zijlstra <> | Subject | Re: locking/atomic: Introduce atomic_try_cmpxchg() |
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On Fri, Mar 24, 2017 at 01:27:49PM -0700, Andy Lutomirski wrote: > On Fri, Mar 24, 2017 at 1:22 PM, Peter Zijlstra <peterz@infradead.org> wrote: > > On Fri, Mar 24, 2017 at 11:45:46AM -0700, Andy Lutomirski wrote: > >> After playing with it a bit, I found some of the problem: you're > >> passing val into EXCEPTION_VALUE, which keeps it live. If I get rid > >> of that, the generated code is great. > > > > Right, so I needed that because I land on ud2 through 2 different paths: > > > > - newly saturated > > - use-after-free > > > > And the exception handler can figure out which of the two by looking at > > the variable, but then of course, it needs to be life. > > > > For the full horror of how to do this, look here: > > > > http://paste.debian.net/924190/ > > > > But I didn't just show you that, so you can't blame me for any damage > > that might've done you. > > Wow, that's horrible. Could this not be done by looking at flags > instead of regs?
Well, the EXCEPTION_HANDLER() thing is something ARM/ARM64 could also implement.
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