Re: [Bpf] IETF 118 BPF WG summary

[Michael Richardson <mcr+ietf@sandelman.ca>]

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David Vernet <void@manifault.com> wrote:
    > We had a productive BPF working group meeting at IETF 118, and we
    > wanted to provide a summary to recap what was discussed.

David, this is a most excellent summary, thank you.
(I wasn't there, I had a conflict)

    > subset. Existing language MMs do not properly handle control
    > dependencies, and suffer from issues such as OOTA (Out-of-Thin-Air)
    > reads. The presentation outlined the control dependencies proposed for
    > various types of BPF instructions, such as atomics, jumps, etc.

I didn't know what an OOTA read was, but I think that hte first answer at:
  https://stackoverflow.com/questions/42588079/what-is-out-of-thin-air-safety

explained it, but I just wnated to be sure that this was the same term.

I think that we don't expect compilers emitting BPF code to do things like
the tearing example:
        void threadA() {
            g = 0xAB00;  // "tearing"
            g += 0x00CD;
        }

but an underlying BPF JIT might do this kind of thing, and of course, the
reads could be anywhere, and the variable could be written by C-code (or
RUST!).


--
Michael Richardson <mcr+IETF@sandelman.ca>, Sandelman Software Works
 -= IPv6 IoT consulting =-                      *I*LIKE*TRAINS*




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