[PATCH 1/1] Revert "tools build: Remove leftover libcap tests that prevents fast path feature detection from working"

[Arnaldo Carvalho de Melo]

Ian pointed out that the libcap feature test is also used by bpftool, so
we can't remove it just because perf stopped using it, revert the
removal of the feature test.

Since both perf and libcap uses the fast path feature detection
(tools/build/feature/test-all.c), probably the best thing is to keep
libcap-devel when building perf even it not being used there.

This reverts commit 47b3b6435e4bfb61ae8ffc63a11bd3c310f69acf.

Cc: Adrian Hunter <adrian.hunter@xxxxxxxxx>
Cc: Ian Rogers <irogers@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/build/feature/Makefile      |  6 +++++-
 tools/build/feature/test-libcap.c | 20 ++++++++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)
 create mode 100644 tools/build/feature/test-libcap.c

diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
index b873fc58804e2f38..12796808f07a8c0d 100644
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -25,6 +25,7 @@ FILES=                                          \
          test-libbfd-liberty-z.bin              \
          test-cplus-demangle.bin                \
          test-cxa-demangle.bin                  \
+         test-libcap.bin			\
          test-libelf.bin                        \
          test-libelf-getphdrnum.bin             \
          test-libelf-gelf_getnote.bin           \
@@ -111,7 +112,7 @@ all: $(FILES)
 __BUILD = $(CC) $(CFLAGS) -MD -Wall -Werror -o $@ $(patsubst %.bin,%.c,$(@F)) $(LDFLAGS)
   BUILD = $(__BUILD) > $(@:.bin=.make.output) 2>&1
   BUILD_BFD = $(BUILD) -DPACKAGE='"perf"' -lbfd -ldl
-  BUILD_ALL = $(BUILD) -fstack-protector-all -O2 -D_FORTIFY_SOURCE=2 -ldw -lelf -lnuma -lelf -lslang $(FLAGS_PERL_EMBED) $(FLAGS_PYTHON_EMBED) -DPACKAGE='"perf"' -lbfd -ldl -lz -llzma -lzstd
+  BUILD_ALL = $(BUILD) -fstack-protector-all -O2 -D_FORTIFY_SOURCE=2 -ldw -lelf -lnuma -lelf -lslang $(FLAGS_PERL_EMBED) $(FLAGS_PYTHON_EMBED) -DPACKAGE='"perf"' -lbfd -ldl -lz -llzma -lzstd -lcap
 
 __BUILDXX = $(CXX) $(CXXFLAGS) -MD -Wall -Werror -o $@ $(patsubst %.bin,%.cpp,$(@F)) $(LDFLAGS)
   BUILDXX = $(__BUILDXX) > $(@:.bin=.make.output) 2>&1
@@ -139,6 +140,9 @@ $(OUTPUT)test-fortify-source.bin:
 $(OUTPUT)test-bionic.bin:
 	$(BUILD)
 
+$(OUTPUT)test-libcap.bin:
+	$(BUILD) -lcap
+
 $(OUTPUT)test-libelf.bin:
 	$(BUILD) -lelf
 
diff --git a/tools/build/feature/test-libcap.c b/tools/build/feature/test-libcap.c
new file mode 100644
index 0000000000000000..d2a2e152195f976b
--- /dev/null
+++ b/tools/build/feature/test-libcap.c
@@ -0,0 +1,20 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <sys/capability.h>
+#include <linux/capability.h>
+
+int main(void)
+{
+	cap_flag_value_t val;
+	cap_t caps = cap_get_proc();
+
+	if (!caps)
+		return 1;
+
+	if (cap_get_flag(caps, CAP_SYS_ADMIN, CAP_EFFECTIVE, &val) != 0)
+		return 1;
+
+	if (cap_free(caps) != 0)
+		return 1;
+
+	return 0;
+}
-- 
2.46.0