[PATCH v3 1/4] perf: Enable libtracefs dynamic linking

[Ian Rogers <irogers@google.com>]

Currently libtracefs isn't used by perf, but there are potential
improvements by using it as identified Steven Rostedt's e-mail:
https://lore.kernel.org/lkml/20210610154759.1ef958f0@oasis.local.home/

This change is modelled on the dynamic libtraceevent patch by Michael
Petlan:
https://lore.kernel.org/linux-perf-users/20210428092023.4009-1-mpetlan@redhat.com/

v3. Adds file missed in v1 and v2 spotted by Jiri Olsa.

Signed-off-by: Ian Rogers <irogers@google.com>
---
 tools/build/Makefile.feature          |  1 +
 tools/build/feature/Makefile          |  4 ++++
 tools/build/feature/test-libtracefs.c | 10 ++++++++++
 tools/perf/Makefile.config            |  9 +++++++++
 tools/perf/Makefile.perf              |  2 ++
 5 files changed, 26 insertions(+)
 create mode 100644 tools/build/feature/test-libtracefs.c

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 3dd2f68366f9..45a9a59828c3 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -52,6 +52,7 @@ FEATURE_TESTS_BASIC :=                  \
         libslang                        \
         libslang-include-subdir         \
         libtraceevent                   \
+        libtracefs                      \
         libcrypto                       \
         libunwind                       \
         pthread-attr-setaffinity-np     \
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index eff55d287db1..d024b5204ba0 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -36,6 +36,7 @@ FILES=                                          \
          test-libslang.bin                      \
          test-libslang-include-subdir.bin       \
          test-libtraceevent.bin                 \
+         test-libtracefs.bin                    \
          test-libcrypto.bin                     \
          test-libunwind.bin                     \
          test-libunwind-debug-frame.bin         \
@@ -199,6 +200,9 @@ $(OUTPUT)test-libslang-include-subdir.bin:
 $(OUTPUT)test-libtraceevent.bin:
 	$(BUILD) -ltraceevent
 
+$(OUTPUT)test-libtracefs.bin:
+	$(BUILD) -ltracefs
+
 $(OUTPUT)test-libcrypto.bin:
 	$(BUILD) -lcrypto
 
diff --git a/tools/build/feature/test-libtracefs.c b/tools/build/feature/test-libtracefs.c
new file mode 100644
index 000000000000..8eff16c0c10b
--- /dev/null
+++ b/tools/build/feature/test-libtracefs.c
@@ -0,0 +1,10 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <tracefs/tracefs.h>
+
+int main(void)
+{
+	struct tracefs_instance *inst = tracefs_instance_create("dummy");
+
+	tracefs_instance_destroy(inst);
+	return 0;
+}
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index 446180401e26..00ec900ddbca 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -1098,6 +1098,15 @@ ifdef LIBTRACEEVENT_DYNAMIC
   endif
 endif
 
+ifdef LIBTRACEFS_DYNAMIC
+  $(call feature_check,libtracefs)
+  ifeq ($(feature-libtracefs), 1)
+    EXTLIBS += -ltracefs
+  else
+    dummy := $(error Error: No libtracefs devel library found, please install libtracefs-dev);
+  endif
+endif
+
 # Among the variables below, these:
 #   perfexecdir
 #   perf_include_dir
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index e04313c4d840..7df13e74450c 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -130,6 +130,8 @@ include ../scripts/utilities.mak
 #
 # Define LIBTRACEEVENT_DYNAMIC to enable libtraceevent dynamic linking
 #
+# Define LIBTRACEFS_DYNAMIC to enable libtracefs dynamic linking
+#
 
 # As per kernel Makefile, avoid funny character set dependencies
 unexport LC_ALL
-- 
2.33.0.464.g1972c5931b-goog