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Subject[RFC v2 1/2] perf: support build BPF skeletons with perf
Date
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.

Signed-off-by: Song Liu <songliubraving@fb.com>
---
tools/bpf/bpftool/Makefile | 2 ++
tools/build/Makefile.feature | 3 +-
tools/perf/Makefile.config | 9 +++++
tools/perf/Makefile.perf | 52 ++++++++++++++++++++++++++--
tools/perf/util/bpf_skel/.gitignore | 3 ++
tools/perf/util/bpf_skel/dummy.bpf.c | 19 ++++++++++
tools/scripts/Makefile.include | 1 +
7 files changed, 86 insertions(+), 3 deletions(-)
create mode 100644 tools/perf/util/bpf_skel/.gitignore
create mode 100644 tools/perf/util/bpf_skel/dummy.bpf.c

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index f60e6ad3a1dff..a01407ec78dc5 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -120,6 +120,8 @@ endif

BPFTOOL_BOOTSTRAP := $(if $(OUTPUT),$(OUTPUT)bpftool-bootstrap,./bpftool-bootstrap)

+bootstrap: $(BPFTOOL_BOOTSTRAP)
+
BOOTSTRAP_OBJS = $(addprefix $(OUTPUT),main.o common.o json_writer.o gen.o btf.o)
OBJS = $(patsubst %.c,$(OUTPUT)%.o,$(SRCS)) $(OUTPUT)disasm.o

diff --git a/tools/build/Makefile.feature b/tools/build/Makefile.feature
index 97cbfb31b7625..95a58b5564218 100644
--- a/tools/build/Makefile.feature
+++ b/tools/build/Makefile.feature
@@ -70,7 +70,8 @@ FEATURE_TESTS_BASIC := \
libaio \
libzstd \
disassembler-four-args \
- file-handle
+ file-handle \
+ clang-bpf-co-re

# FEATURE_TESTS_BASIC + FEATURE_TESTS_EXTRA is the complete list
# of all feature tests
diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
index ce8516e4de34f..cb0cf06e0bb43 100644
--- a/tools/perf/Makefile.config
+++ b/tools/perf/Makefile.config
@@ -621,6 +621,15 @@ ifndef NO_LIBBPF
endif
endif

+ifeq ($(feature-clang-bpf-co-re), 0)
+ BUILD_BPF_SKEL := 0
+endif
+
+ifeq ($(BUILD_BPF_SKEL), 1)
+ $(call detected,CONFIG_PERF_BPF_SKEL)
+ CFLAGS += -DBUILD_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..37b7ffe1db27c 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
@@ -735,7 +737,8 @@ 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 +1011,52 @@ 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 util/bpf_skel)
+SKEL_TMP_OUT := $(abspath util/bpf_skel/.tmp)
+SKELETONS := $(SKEL_OUT)/dummy.skel.h
+
+ifdef BUILD_BPF_SKEL
+CLANG ?= clang
+LLVM_STRIP ?= llvm-strip
+BPFTOOL_CFLAGS := $(filter-out -D_GNU_SOURCE,$(CFLAGS))
+BPFTOOL := $(SKEL_TMP_OUT)/bpftool-bootstrap
+LIBBPF_SRC := $(abspath ../lib/bpf)
+BPFOBJ := $(SKEL_TMP_OUT)/libbpf.a
+BPF_INCLUDE := $(SKEL_TMP_OUT)
+submake_extras := feature_display=0
+
+$(SKEL_TMP_OUT):
+ $(Q)$(MKDIR) -p $@
+
+$(BPFTOOL): | $(SKEL_TMP_OUT)
+ CFLAGS= $(MAKE) $(submake_extras) -C ../bpf/bpftool \
+ OUTPUT=$(SKEL_TMP_OUT)/ bootstrap
+
+$(SKEL_TMP_OUT)/%.bpf.o: util/bpf_skel/%.bpf.c $(BPFOBJ) | $(SKEL_TMP_OUT)
+ $(call QUIET_CLANG, $@)
+ $(Q)$(CLANG) -g -O2 -target bpf -c $(filter util/bpf_skel/%.bpf.c,$^) -o $@ && \
+ $(LLVM_STRIP) -g $@
+
+$(SKEL_OUT)/%.skel.h: $(SKEL_TMP_OUT)/%.bpf.o | $(BPFTOOL)
+ $(call QUIET_GENSKEL, $@)
+ $(Q)$(BPFTOOL) gen skeleton $< > $@
+
+bpf-skel: $(SKELETONS)
+
+$(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(SKEL_TMP_OUT)
+ $(Q)$(MAKE) $(submake_extras) -C $(LIBBPF_SRC) \
+ OUTPUT=$(abspath $(dir $@))/ $(abspath $@)
+
+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) $(OUTPUT).config-detected
diff --git a/tools/perf/util/bpf_skel/.gitignore b/tools/perf/util/bpf_skel/.gitignore
new file mode 100644
index 0000000000000..5263e9e6c5d83
--- /dev/null
+++ b/tools/perf/util/bpf_skel/.gitignore
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0-only
+.tmp
+*.skel.h
\ No newline at end of file
diff --git a/tools/perf/util/bpf_skel/dummy.bpf.c b/tools/perf/util/bpf_skel/dummy.bpf.c
new file mode 100644
index 0000000000000..492a43a851deb
--- /dev/null
+++ b/tools/perf/util/bpf_skel/dummy.bpf.c
@@ -0,0 +1,19 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+// Copyright (c) 2020 Facebook
+#include <linux/bpf.h>
+#include <bpf/bpf_helpers.h>
+#include <bpf/bpf_tracing.h>
+
+struct {
+ __uint(type, BPF_MAP_TYPE_PERCPU_ARRAY);
+ __uint(key_size, sizeof(__u32));
+ __uint(value_size, sizeof(__u64));
+} counts SEC(".maps");
+
+SEC("fentry/dummy")
+int BPF_PROG(fentry_dummy)
+{
+ return 0;
+}
+
+char LICENSE[] SEC("license") = "Dual BSD/GPL";
diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
index a7974638561ca..ed1720dc12194 100644
--- a/tools/scripts/Makefile.include
+++ b/tools/scripts/Makefile.include
@@ -126,6 +126,7 @@ ifneq ($(silent),1)
QUIET_CLEAN = @printf ' CLEAN %s\n' $1;
QUIET_INSTALL = @printf ' INSTALL %s\n' $1;
QUIET_UNINST = @printf ' UNINST %s\n' $1;
+ QUIET_GENSKEL = @printf ' GEN-SKEL %s\n' $1;
endif
endif

--
2.24.1
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