Messages in this thread | | | Subject | Re: [PATCH v3 net-next] bpf/verifier: track liveness for pruning | From | Alexei Starovoitov <> | Date | Mon, 21 Aug 2017 14:18:45 -0700 |
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On 8/21/17 1:24 PM, Edward Cree wrote: > On 18/08/17 15:16, Edward Cree wrote: >> On 18/08/17 04:21, Alexei Starovoitov wrote: >>> It seems you're trying to sort-of do per-fake-basic block liveness >>> analysis, but our state_list_marks are not correct if we go with >>> canonical basic block definition, since we mark the jump insn and >>> not insn after the branch and not every basic block boundary is >>> properly detected. >> I think the reason this works is that jump insns can't do writes. >> [snip] >> the sl->state will never have any write marks and it'll all just work. >> But I should really test that! > I tested this, and found that, no, sl->state can have write marks, and the > algorithm will get the wrong answer in that case. So I've got a patch to > make the first iteration ignore write marks, as part of a series which I > will post shortly. When I do so, please re-do your tests with adding > state_list_marks in strange and exciting places; it should work wherever > you put them. Like you say, it "magically doesn't depend on proper basic > block boundaries", and that's because really pruning is just a kind of > checkpointing that just happens to be most effective when done just after > a jump (pop_stack). > > Can I have a SOB for your "grr" test program, so I can include it in the > series?
yes. of course. just give the test some reasonable name :)
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