dwarf stacktrace in bpf

Posted Apr 14, 2021 9:02 UTC (Wed) by seanyoung (subscriber, #28711)
Parent article: Comparing SystemTap and bpftrace

BPF is pretty powerful nowadays. Loops are allowed; instruction set is complete (you can work around the missing signed div) and instruction limits are high. I don't understand why dwarf stacktraces can't be generated in BPF.

dwarf stacktrace in bpf

Posted Apr 14, 2021 13:27 UTC (Wed) by fuhchee (guest, #40059) [Link] (1 responses)

> Loops are allowed

Last I heard, this was compile-time bounded, implemented by unrolling.

dwarf stacktrace in bpf

Posted Apr 14, 2021 14:14 UTC (Wed) by mathstuf (subscriber, #69389) [Link]

This article[1] is the latest I can find. You can have bounded loops now, but they must be verifiable. Validating that there is an end to the stack is data-dependent and likely not allowed. One could get up to a fixed stack size though I presume.

[1]https://lwn.net/Articles/794934/