Re: [Buildroot] [PATCH v2 1/2] package/linux-tools: perf: build with libtraceevent support when it is selected

[Luca Ceresoli via buildroot <buildroot@buildroot.org>]

On mercoledì 9 luglio 2025 17:04:14 Ora legale dell’Europa centrale 
Alexis Lothoré wrote:
>When trying to perform a custom uprobe recording on a target with perf
>built by buildroot, the recording step fails as perf can not record
>uprobes without libtraceevent support:
>
>  $ perf probe -x linked_list insert_name index
>  Target program is compiled without optimization. Skipping prologue.
>  Probe on address 0x808 to force probing at the function entry.
>
>  Added new event:
>    probe_linked_list:insert_name (on insert_name in
>/root/gdb/linked_list with index)
>
>  perf is not linked with libtraceevent, to use the new probe you can
>use tracefs:
>
>          cd /sys/kernel/tracing/
>          echo 1 > events/probe_linked_list/insert_name/enable
>          echo 1 > tracing_on
>          cat trace_pipe
>          Before removing the probe, echo 0 >
>events/probe_linked_list/insert_name/enable $ perf record -e
>probe_linked_list:insert_name ./linked_list event syntax error:
>'probe_linked_list:insert_name'
>                       \___ unsupported tracepoint
>
>  libtraceevent is necessary for tracepoint support
>  Run 'perf list' for a list of valid events
>
>   Usage: perf record [<options>] [<command>]
>      or: perf record [<options>] -- <command> [<options>]
>
>      -e, --event <event>   event selector. use 'perf list' to list
>available events
>
>libtraceevent support for perf has been disabled with commit
>b4ab45a5c1db ("package/linux-tools: disable libtracevent detection")
>because there was no libtraceevent package in buildroot to replace the
>former libtraceevent removed from the kernel sources. Since then,
>commit 1474f1b34b17 ("package/libtraceevent: new package") has
>introduced a libtraceevent package. We can then expose again the
>possibility to build perf with libtraceevent support.
>
>Make buildroot perf makefile detect if libtraceevent package has been
>enabled, and if so, allow to build perf with libtraceevent support.
>
>Signed-off-by: Alexis Lothoré <alexis.lothore@bootlin.com>

Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
Tested-by: Luca Ceresoli <luca.ceresoli@bootlin.com>

Luca

-- 
Luca Ceresoli, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com



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