[PATCH v6 2/4] perf: support build BPF skeletons with perf

[Song Liu]

BPF programs are useful in perf to profile BPF programs. BPF skeleton is
by far the easiest way to write BPF tools. Enable building BPF skeletons
in util/bpf_skel. A dummy bpf skeleton is added. More bpf skeletons will
be added for different use cases.

Acked-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Signed-off-by: Song Liu <songliubraving@xxxxxx>
---
 tools/build/Makefile.feature        |  4 ++-
 tools/perf/Makefile.config          |  9 ++++++
 tools/perf/Makefile.perf            | 49 +++++++++++++++++++++++++++--
 tools/perf/util/bpf_skel/.gitignore |  3 ++
 tools/scripts/Makefile.include      |  1 +
 5 files changed, 63 insertions(+), 3 deletions(-)
 create mode 100644 tools/perf/util/bpf_skel/.gitignore

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 97cbfb31b7625..74e255d58d8d0 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -99,7 +99,9 @@ FEATURE_TESTS_EXTRA :=                  \
          clang                          \
          libbpf                         \
          libpfm4                        \
-         libdebuginfod
+         libdebuginfod			\
+         clang-bpf-co-re
+
 
 FEATURE_TESTS ?= $(FEATURE_TESTS_BASIC)
 
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index ce8516e4de34f..d8e59d31399a5 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -621,6 +621,15 @@ ifndef NO_LIBBPF
   endif
 endif
 
+ifdef BUILD_BPF_SKEL
+  $(call feature_check,clang-bpf-co-re)
+  ifeq ($(feature-clang-bpf-co-re), 0)
+    dummy := $(error Error: clang too old. Please install recent clang)
+  endif
+  $(call detected,CONFIG_PERF_BPF_SKEL)
+  CFLAGS += -DHAVE_BPF_SKEL
+endif
+
 dwarf-post-unwind := 1
 dwarf-post-unwind-text := BUG
 
diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
index 62f3deb1d3a8b..d182a2dbb9bbd 100644
--- a/tools/perf/Makefile.perf
+++ b/tools/perf/Makefile.perf
@@ -126,6 +126,8 @@ include ../scripts/utilities.mak
 #
 # Define NO_LIBDEBUGINFOD if you do not want support debuginfod
 #
+# Define BUILD_BPF_SKEL to enable BPF skeletons
+#
 
 # As per kernel Makefile, avoid funny character set dependencies
 unexport LC_ALL
@@ -175,6 +177,12 @@ endef
 
 LD += $(EXTRA_LDFLAGS)
 
+HOSTCC  ?= gcc
+HOSTLD  ?= ld
+HOSTAR  ?= ar
+CLANG   ?= clang
+LLVM_STRIP ?= llvm-strip
+
 PKG_CONFIG = $(CROSS_COMPILE)pkg-config
 LLVM_CONFIG ?= llvm-config
 
@@ -731,7 +739,8 @@ prepare: $(OUTPUT)PERF-VERSION-FILE $(OUTPUT)common-cmds.h archheaders $(drm_ioc
 	$(x86_arch_prctl_code_array) \
 	$(rename_flags_array) \
 	$(arch_errno_name_array) \
-	$(sync_file_range_arrays)
+	$(sync_file_range_arrays) \
+	bpf-skel
 
 $(OUTPUT)%.o: %.c prepare FORCE
 	$(Q)$(MAKE) -f $(srctree)/tools/build/Makefile.build dir=$(build-dir) $@
@@ -1004,7 +1013,43 @@ config-clean:
 python-clean:
 	$(python-clean)
 
-clean:: $(LIBTRACEEVENT)-clean $(LIBAPI)-clean $(LIBBPF)-clean $(LIBSUBCMD)-clean $(LIBPERF)-clean config-clean fixdep-clean python-clean
+SKEL_OUT := $(abspath $(OUTPUT)util/bpf_skel)
+SKEL_TMP_OUT := $(abspath $(SKEL_OUT)/.tmp)
+SKELETONS :=
+
+ifdef BUILD_BPF_SKEL
+BPFTOOL := $(SKEL_TMP_OUT)/bootstrap/bpftool
+LIBBPF_SRC := $(abspath ../lib/bpf)
+BPF_INCLUDE := -I$(SKEL_TMP_OUT)/.. -I$(BPF_PATH) -I$(LIBBPF_SRC)/..
+
+$(SKEL_TMP_OUT):
+	$(Q)$(MKDIR) -p $@
+
+$(BPFTOOL): | $(SKEL_TMP_OUT)
+	CFLAGS= $(MAKE) -C ../bpf/bpftool \
+		OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
+
+$(SKEL_TMP_OUT)/%.bpf.o: util/bpf_skel/%.bpf.c $(LIBBPF) | $(SKEL_TMP_OUT)
+	$(QUIET_CLANG)$(CLANG) -g -O2 -target bpf $(BPF_INCLUDE) \
+	  -c $(filter util/bpf_skel/%.bpf.c,$^) -o $@ && $(LLVM_STRIP) -g $@
+
+$(SKEL_OUT)/%.skel.h: $(SKEL_TMP_OUT)/%.bpf.o | $(BPFTOOL)
+	$(QUIET_GENSKEL)$(BPFTOOL) gen skeleton $< > $@
+
+bpf-skel: $(SKELETONS)
+
+.PRECIOUS: $(SKEL_TMP_OUT)/%.bpf.o
+
+else # BUILD_BPF_SKEL
+
+bpf-skel:
+
+endif # BUILD_BPF_SKEL
+
+bpf-skel-clean:
+	$(call QUIET_CLEAN, bpf-skel) $(RM) -r $(SKEL_TMP_OUT) $(SKELETONS)
+
+clean:: $(LIBTRACEEVENT)-clean $(LIBAPI)-clean $(LIBBPF)-clean $(LIBSUBCMD)-clean $(LIBPERF)-clean config-clean fixdep-clean python-clean bpf-skel-clean
 	$(call QUIET_CLEAN, core-objs)  $(RM) $(LIBPERF_A) $(OUTPUT)perf-archive $(OUTPUT)perf-with-kcore $(LANG_BINDINGS)
 	$(Q)find $(if $(OUTPUT),$(OUTPUT),.) -name '*.o' -delete -o -name '\.*.cmd' -delete -o -name '\.*.d' -delete
 	$(Q)$(RM) $(OUTPUT).config-detected
diff --git a/tools/perf/util/bpf_skel/.gitignore b/tools/perf/util/bpf_skel/.gitignore
new file mode 100644
index 0000000000000..5263e9e6c5d83
--- /dev/null
+++ b/tools/perf/util/bpf_skel/.gitignore
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+.tmp
+*.skel.h
\ No newline at end of file
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index 1358e89cdf7d6..62119ce69ad9a 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -127,6 +127,7 @@ ifneq ($(silent),1)
 			 $(MAKE) $(PRINT_DIR) -C $$subdir
 	QUIET_FLEX     = @echo '  FLEX     '$@;
 	QUIET_BISON    = @echo '  BISON    '$@;
+	QUIET_GENSKEL  = @echo '  GEN-SKEL '$@;
 
 	descend = \
 		+@echo	       '  DESCEND  '$(1); \
-- 
2.24.1