Kernel bypass networking using pseudo-syscalls?

Chris Pick rr at
Tue Aug 1 21:37:06 UTC 2017

I was evangelizing rr to a friend last night who's been debugging a program
that uses kernel bypass for networking.

I assumed that 1) userspace uses DMA to interact with the networking
hardware and like shared memory, DMA isn't supported by rr.  If those are
true and, further assuming 3) all the DMA/magic is hidden behind a pair of
send_pkt() and recv_pkt() functions, would it be possible to have rr treat
that pair as a set of custom pseudo-syscalls, recording their inputs and
outputs for later replay?

I imagine something similar must be done if rr supports recording/replaying
vDSO functions?

Thanks for such a useful tool, -Chris
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