[PATCH 4.19 09/43] tools build feature: Check if eventfd() is available

Greg Kroah-Hartman
2021-03-22T13:01:39Z

From: Arnaldo Carvalho de Melo <acme@redhat.com>

commit 11c6cbe706f218a8dc7e1f962f12b3a52ddd33a9 upstream.

A new 'perf bench epoll' will use this, and to disable it for older
systems, add a feature test for this API.

This is just a simple program that if successfully compiled, means that
the feature is present, at least at the library level, in a build that
sets the output directory to /tmp/build/perf (using O=/tmp/build/perf),
we end up with:

$ ls -la /tmp/build/perf/feature/test-eventfd*
-rwxrwxr-x. 1 acme acme 8176 Nov 21 15:58 /tmp/build/perf/feature/test-eventfd.bin
-rw-rw-r--. 1 acme acme 588 Nov 21 15:58 /tmp/build/perf/feature/test-eventfd.d
-rw-rw-r--. 1 acme acme 0 Nov 21 15:58 /tmp/build/perf/feature/test-eventfd.make.output
$ ldd /tmp/build/perf/feature/test-eventfd.bin
linux-vdso.so.1 (0x00007fff3bf3f000)
libc.so.6 => /lib64/libc.so.6 (0x00007fa984061000)
/lib64/ld-linux-x86-64.so.2 (0x00007fa984417000)
$ grep eventfd -A 2 -B 2 /tmp/build/perf/FEATURE-DUMP
feature-dwarf=1
feature-dwarf_getlocations=1
feature-eventfd=1
feature-fortify-source=1
feature-sync-compare-and-swap=1
$

The main thing here is that in the end we'll have -DHAVE_EVENTFD in
CFLAGS, and then the 'perf bench' entry needing that API can be
selectively pruned.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Davidlohr Bueso <dbueso@suse.de>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-wkeldwob7dpx6jvtuzl8164k@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
tools/build/Makefile.feature | 1 +
tools/build/feature/Makefile | 4 ++++
tools/build/feature/test-all.c | 5 +++++
tools/build/feature/test-eventfd.c | 9 +++++++++
tools/perf/Makefile.config | 5 ++++-
5 files changed, 23 insertions(+), 1 deletion(-)
create mode 100644 tools/build/feature/test-eventfd.c

--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -31,6 +31,7 @@ FEATURE_TESTS_BASIC :=
backtrace \
dwarf \
dwarf_getlocations \
+ eventfd \
fortify-source \
sync-compare-and-swap \
get_current_dir_name \
--- a/tools/build/feature/Makefile
+++ b/tools/build/feature/Makefile
@@ -5,6 +5,7 @@ FILES=
test-bionic.bin \
test-dwarf.bin \
test-dwarf_getlocations.bin \
+ test-eventfd.bin \
test-fortify-source.bin \
test-sync-compare-and-swap.bin \
test-get_current_dir_name.bin \
@@ -100,6 +101,9 @@ $(OUTPUT)test-bionic.bin:
$(OUTPUT)test-libelf.bin:
$(BUILD) -lelf

+$(OUTPUT)test-eventfd.bin:
+ $(BUILD)
+
$(OUTPUT)test-get_current_dir_name.bin:
$(BUILD)

--- a/tools/build/feature/test-all.c
+++ b/tools/build/feature/test-all.c
@@ -50,6 +50,10 @@
# include "test-dwarf_getlocations.c"
#undef main

+#define main main_test_eventfd
+# include "test-eventfd.c"
+#undef main
+
#define main main_test_libelf_getphdrnum
# include "test-libelf-getphdrnum.c"
#undef main
@@ -182,6 +186,7 @@ int main(int argc, char *argv[])
main_test_glibc();
main_test_dwarf();
main_test_dwarf_getlocations();
+ main_test_eventfd();
main_test_libelf_getphdrnum();
main_test_libelf_gelf_getnote();
main_test_libelf_getshdrstrndx();
--- /dev/null
+++ b/tools/build/feature/test-eventfd.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2018, Red Hat Inc, Arnaldo Carvalho de Melo <acme@redhat.com>
+
+#include <sys/eventfd.h>
+
+int main(void)
+{
+ return eventfd(0, EFD_NONBLOCK);
+}
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -310,11 +310,14 @@ ifndef NO_BIONIC
endif
endif

+ifeq ($(feature-eventfd), 1)
+ CFLAGS += -DHAVE_EVENTFD
+endif
+
ifeq ($(feature-get_current_dir_name), 1)
CFLAGS += -DHAVE_GET_CURRENT_DIR_NAME
endif

-
ifdef NO_LIBELF
NO_DWARF := 1
NO_DEMANGLE := 1