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

["Alexis Lothoré via buildroot" <buildroot@buildroot.org>]

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>
---
Changes in v2:
- no change
---
 package/linux-tools/linux-tool-perf.mk.in | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/package/linux-tools/linux-tool-perf.mk.in b/package/linux-tools/linux-tool-perf.mk.in
index d67318571aa4deefde5b38effe1ade0b87f4627b..1e19ee7f1c4e46d210c079d796f9461f2bfaae08 100644
--- a/package/linux-tools/linux-tool-perf.mk.in
+++ b/package/linux-tools/linux-tool-perf.mk.in
@@ -28,7 +28,6 @@ PERF_MAKE_FLAGS = \
 	NO_LIBPERL=1 \
 	NO_LIBPYTHON=1 \
 	NO_LIBBIONIC=1 \
-	NO_LIBTRACEEVENT=1 \
 	NO_SHELLCHECK=1
 
 # We need to pass an argument to ld for setting the emulation when
@@ -128,6 +127,12 @@ PERF_MAKE_FLAGS += CORESIGHT=1
 # bare "ifdef CORESIGHT" constructs.
 endif
 
+ifeq ($(BR2_PACKAGE_LIBTRACEEVENT),y)
+PERF_DEPENDENCIES += libtraceevent
+else
+PERF_MAKE_FLAGS += NO_LIBTRACEEVENT=1
+endif
+
 # We really do not want to build the perf documentation, because it
 # has stringent requirement on the documentation generation tools,
 # like xmlto and asciidoc), which may be lagging behind on some

-- 
2.50.0

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