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 <[email protected]>
Signed-off-by: Song Liu <[email protected]>
---
 tools/build/Makefile.feature        |  4 ++-
 tools/perf/Makefile.config          |  9 ++++++
 tools/perf/Makefile.perf            | 43 +++++++++++++++++++++++++++--
 tools/perf/util/bpf_skel/.gitignore |  3 ++
 tools/scripts/Makefile.include      |  1 +
 5 files changed, 57 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 7ce3f2e8b9c74..24dfacbff39d4 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
@@ -178,6 +180,8 @@ 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
@@ -735,7 +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) $@
@@ -1008,7 +1013,41 @@ 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)/bpftool-bootstrap
+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)
+
+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) $(OUTPUT).config-detected
diff --git a/tools/perf/util/bpf_skel/.gitignore 
b/tools/perf/util/bpf_skel/.gitignore
new file mode 100644
index 0000000000000..5263e9e6c5d83
--- /dev/null
+++ b/tools/perf/util/bpf_skel/.gitignore
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+.tmp
+*.skel.h
\ No newline at end of file
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index a7974638561ca..2da3b37f1c6bf 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -117,6 +117,7 @@ ifneq ($(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

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