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Diffstat (limited to 'website/content/en/status/report-2023-01-2023-03/kinst.adoc')
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diff --git a/website/content/en/status/report-2023-01-2023-03/kinst.adoc b/website/content/en/status/report-2023-01-2023-03/kinst.adoc new file mode 100644 index 0000000000..9320736896 --- /dev/null +++ b/website/content/en/status/report-2023-01-2023-03/kinst.adoc @@ -0,0 +1,66 @@ +=== Improve the kinst DTrace provider + +Links: + +link:https://reviews.freebsd.org/D38825[libdtrace: implement inline function tracing] URL: link:https://reviews.freebsd.org/D38825[] + +link:https://reviews.freebsd.org/D38732[dtrace(1): add -d flag to dump D script post-dt_sugar] URL: link:https://reviews.freebsd.org/D38732[] + +Contact: Christos Margiolis <christos@FreeBSD.org> + +Contact: Mark Johnston <markj@FreeBSD.org> + +kinst is a new DTrace provider created by christos@ and markj@ that allows for arbitrary instruction tracing in a kernel function. +kinst has been added to the base system in FreeBSD 14.0. + +link:../report-2022-07-2022-09/#_dtrace_instruction_level_dynamic_tracing[The 2022Q3 status report gives a brief introduction to kinst.] +We're now working on inline function tracing (see review D38825 above) -- a much-requested DTrace feature -- by using kernel DWARF and ELF info to find the call sites of each inline copy and use that information to transform D syntax by turning kinst probes of the form: + +.... + kinst::<inline_func>:<entry/return> + /<pred>/ + { + <acts> + } +.... + +To: + +.... + kinst::<caller_func1>:<offset>, + kinst::<caller_func2>:<offset>, + kinst::<caller_func3>:<offset> + /<pred>/ + { + <acts> + } +.... + +For example: + +.... + # dtrace -dn 'kinst::cam_iosched_has_more_trim:entry { printf("\t%d\t%s", pid, execname); }' + kinst::cam_iosched_get_trim:13, + kinst::cam_iosched_next_bio:13, + kinst::cam_iosched_schedule:40 + { + printf("\t%d\t%s", pid, execname); + } + + dtrace: description 'kinst::cam_iosched_has_more_trim:entry ' matched 3 probes + CPU ID FUNCTION:NAME + 2 79315 cam_iosched_next_bio:13 0 kernel + 2 79316 cam_iosched_schedule:40 0 kernel + 0 79316 cam_iosched_schedule:40 12 intr + 2 79315 cam_iosched_next_bio:13 0 kernel + 2 79316 cam_iosched_schedule:40 0 kernel + 0 79316 cam_iosched_schedule:40 12 intr + ^C +.... + +A new `-d` flag has also been added to man:dtrace[1] which dumps the D script after libdtrace has applied syntactic transformations. + +Further goals include: + +* Implement a `locals` structure in D which stores the local variables of the traced function. + For example with `kinst::foo:<x>`, we could print the local variable `bar` by doing `print(locals->bar)` inside a D script. +* Port kinst to riscv and/or arm64. + +Sponsor: The FreeBSD Foundation |