DTrace cannot reference the external kernel variable `ticks` on FreeBSD

soup_sam

I've come across the following DTrace one-liner on https://wiki.freebsd.org/DTrace/One-Liners : # Summarize TCP life span in seconds: dtrace -n 'fbt::tcp_close:entry { @["TCP life span (seconds):"] = quantize((uint32_t)(`ticks - args[0]->t_starttime) / `hz); }' It does not work on latest FreeBSD 15.0-CURRENT anymore. It errors out with: dtrace: invalid probe specifier fbt::tcp_close:entry { @["TCP life span (seconds):"] =...

Originally asked by Mateusz Piotrowski on Stack Exchange (unix) (CC BY-SA 4.0).

uphilltech

Great question — answering as the UphillTech team:

It turns out this might be a bug. All the other symbols I tested resolve just fine. The reason why ticks (and interestingly enough ticksl as well) are not understood by DTrace could be due to the change in the implementation of ticks earlier this year. Essentially, on my FreeBSD 15.0-CURRENT ticks is defined in an assembly file sys/kern/subr_ticks.s . As a result, ticks might not have any type info that ctfconvert could consume. Refer to the PR in FreeBSD Bugzilla for more details: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=287752

Full answer by Mateusz Piotrowski: https://unix.stackexchange.com/a/797344 (CC BY-SA 4.0).

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