Messages in this thread | | | From | Andy Lutomirski <> | Date | Thu, 21 May 2015 09:20:46 -0700 | Subject | Re: [PATCH net-next 1/4] bpf: allow bpf programs to tail-call other bpf programs |
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On Tue, May 19, 2015 at 5:18 PM, Alexei Starovoitov <ast@plumgrid.com> wrote: > On 5/19/15 5:13 PM, Andy Lutomirski wrote: >> >> >> IMO this is starting to get a bit ugly. Would it be possible to have >> the program dereference the subprogram reference itself from the jump >> table? There would have to be a verifier type that represents a >> reference to a program tail-call entry point, but that seems better >> than having this weird indirection. > > > Which part? I don't think you've looked at examples yet. > network parser has to call itself. Otherwise we cannot parse 10 mpls > labels or TLVs. > Indirection via jump_table also has to be there. > We need to dynamically add and remove programs form this jump table. > It cannot be all static. >
What I mean is: why do we need the interface to be "look up this index in an array and just to what it references" as a single atomic instruction? Can't we break it down into first "look up this index in an array" and then "do this tail call"?
I don't see why everything needs to be a map.
--Andy
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