tools/bpftool: Generalize BPF skeleton support and generate vmlinux.h

Adapt Makefile to support BPF skeleton generation beyond single profiler.bpf.c case. Also add vmlinux.h generation and switch profiler.bpf.c to use it. clang-bpf-global-var feature is extended and renamed to clang-bpf-co-re to check for support of preserve_access_index attribute, which, together with BTF for global variables, is the minimum requirement for modern BPF programs. Signed-off-by: Andrii Nakryiko <[email protected]> Signed-off-by: Alexei Starovoitov <[email protected]> Reviewed-by: Quentin Monnet <[email protected]> Link: https://lore.kernel.org/bpf/[email protected]
josf · Jun 23, 2020 · 05aca6d · 05aca6d
1 parent 16e9b18
commit 05aca6d
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Showing 7 changed files with 45 additions and 66 deletions.
diff --git a/tools/bpf/bpftool/.gitignore b/tools/bpf/bpftool/.gitignore
@@ -7,4 +7,5 @@ bpf-helpers.*
 FEATURE-DUMP.bpftool
 feature
 libbpf
-profiler.skel.h
+/*.skel.h
+/vmlinux.h
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
@@ -42,6 +42,7 @@ CFLAGS += -O2
 CFLAGS += -W -Wall -Wextra -Wno-unused-parameter -Wno-missing-field-initializers
 CFLAGS += $(filter-out -Wswitch-enum,$(EXTRA_WARNINGS))
 CFLAGS += -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ \
+	-I$(if $(OUTPUT),$(OUTPUT),.) \
 	-I$(srctree)/kernel/bpf/ \
 	-I$(srctree)/tools/include \
 	-I$(srctree)/tools/include/uapi \
@@ -61,9 +62,9 @@ CLANG ?= clang
 
 FEATURE_USER = .bpftool
 FEATURE_TESTS = libbfd disassembler-four-args reallocarray zlib libcap \
-	clang-bpf-global-var
+	clang-bpf-co-re
 FEATURE_DISPLAY = libbfd disassembler-four-args zlib libcap \
-	clang-bpf-global-var
+	clang-bpf-co-re
 
 check_feat := 1
 NON_CHECK_FEAT_TARGETS := clean uninstall doc doc-clean doc-install doc-uninstall
@@ -121,20 +122,38 @@ BPFTOOL_BOOTSTRAP := $(if $(OUTPUT),$(OUTPUT)bpftool-bootstrap,./bpftool-bootstr
 BOOTSTRAP_OBJS = $(addprefix $(OUTPUT),main.o common.o json_writer.o gen.o btf.o)
 OBJS = $(patsubst %.c,$(OUTPUT)%.o,$(SRCS)) $(OUTPUT)disasm.o
 
-ifneq ($(feature-clang-bpf-global-var),1)
-	CFLAGS += -DBPFTOOL_WITHOUT_SKELETONS
-endif
+VMLINUX_BTF_PATHS := $(if $(O),$(O)/vmlinux)				\
+		     $(if $(KBUILD_OUTPUT),$(KBUILD_OUTPUT)/vmlinux)	\
+		     ../../../vmlinux					\
+		     /sys/kernel/btf/vmlinux				\
+		     /boot/vmlinux-$(shell uname -r)
+VMLINUX_BTF := $(abspath $(firstword $(wildcard $(VMLINUX_BTF_PATHS))))
+
+ifneq ($(VMLINUX_BTF),)
+ifeq ($(feature-clang-bpf-co-re),1)
+
+BUILD_BPF_SKELS := 1
+
+$(OUTPUT)vmlinux.h: $(VMLINUX_BTF) $(BPFTOOL_BOOTSTRAP)
+	$(QUIET_GEN)$(BPFTOOL_BOOTSTRAP) btf dump file $< format c > $@
 
-skeleton/profiler.bpf.o: skeleton/profiler.bpf.c $(LIBBPF)
+$(OUTPUT)%.bpf.o: skeleton/%.bpf.c $(OUTPUT)vmlinux.h $(LIBBPF)
 	$(QUIET_CLANG)$(CLANG) \
+		-I$(if $(OUTPUT),$(OUTPUT),.) \
 		-I$(srctree)/tools/include/uapi/ \
-		-I$(LIBBPF_PATH) -I$(srctree)/tools/lib \
+		-I$(LIBBPF_PATH) \
+		-I$(srctree)/tools/lib \
 		-g -O2 -target bpf -c $< -o $@
 
-profiler.skel.h: $(BPFTOOL_BOOTSTRAP) skeleton/profiler.bpf.o
-	$(QUIET_GEN)$(BPFTOOL_BOOTSTRAP) gen skeleton skeleton/profiler.bpf.o > $@
+$(OUTPUT)%.skel.h: $(OUTPUT)%.bpf.o $(BPFTOOL_BOOTSTRAP)
+	$(QUIET_GEN)$(BPFTOOL_BOOTSTRAP) gen skeleton $< > $@
+
+$(OUTPUT)prog.o: $(OUTPUT)profiler.skel.h
+
+endif
+endif
 
-$(OUTPUT)prog.o: prog.c profiler.skel.h
+CFLAGS += $(if BUILD_BPF_SKELS,,-DBPFTOOL_WITHOUT_SKELETONS)
 
 $(OUTPUT)disasm.o: $(srctree)/kernel/bpf/disasm.c
 	$(QUIET_CC)$(CC) $(CFLAGS) -c -MMD -o $@ $<
@@ -153,7 +172,7 @@ $(OUTPUT)%.o: %.c
 clean: $(LIBBPF)-clean
 	$(call QUIET_CLEAN, bpftool)
 	$(Q)$(RM) -- $(OUTPUT)bpftool $(OUTPUT)*.o $(OUTPUT)*.d
-	$(Q)$(RM) -- $(BPFTOOL_BOOTSTRAP) profiler.skel.h skeleton/profiler.bpf.o
+	$(Q)$(RM) -- $(BPFTOOL_BOOTSTRAP) $(OUTPUT)*.skel.h $(OUTPUT)vmlinux.h
 	$(Q)$(RM) -r -- $(OUTPUT)libbpf/
 	$(call QUIET_CLEAN, core-gen)
 	$(Q)$(RM) -- $(OUTPUT)FEATURE-DUMP.bpftool
@@ -188,6 +207,7 @@ FORCE:
 zdep:
 	@if [ "$(feature-zlib)" != "1" ]; then echo "No zlib found"; exit 1 ; fi
 
+.SECONDARY:
 .PHONY: all FORCE clean install uninstall zdep
 .PHONY: doc doc-clean doc-install doc-uninstall
 .DEFAULT_GOAL := all
diff --git a/tools/bpf/bpftool/skeleton/profiler.bpf.c b/tools/bpf/bpftool/skeleton/profiler.bpf.c
@@ -1,7 +1,6 @@
 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 // Copyright (c) 2020 Facebook
-#include "profiler.h"
-#include <linux/bpf.h>
+#include <vmlinux.h>
 #include <bpf/bpf_helpers.h>
 #include <bpf/bpf_tracing.h>
 

diff --git a/tools/bpf/bpftool/skeleton/profiler.h b/tools/bpf/bpftool/skeleton/profiler.h
diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
@@ -68,7 +68,7 @@ FILES=                                          \
          test-llvm-version.bin			\
          test-libaio.bin			\
          test-libzstd.bin			\
-         test-clang-bpf-global-var.bin		\
+         test-clang-bpf-co-re.bin		\
          test-file-handle.bin			\
          test-libpfm4.bin
 
@@ -325,7 +325,7 @@ $(OUTPUT)test-libaio.bin:
 $(OUTPUT)test-libzstd.bin:
 	$(BUILD) -lzstd
 
-$(OUTPUT)test-clang-bpf-global-var.bin:
+$(OUTPUT)test-clang-bpf-co-re.bin:
 	$(CLANG) -S -g -target bpf -o - $(patsubst %.bin,%.c,$(@F)) |	\
 		grep BTF_KIND_VAR
 

diff --git a/tools/build/feature/test-clang-bpf-co-re.c b/tools/build/feature/test-clang-bpf-co-re.c
@@ -0,0 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (c) 2020 Facebook
+
+struct test {
+	int a;
+	int b;
+} __attribute__((preserve_access_index));
+
+volatile struct test global_value_for_test = {};
diff --git a/tools/build/feature/test-clang-bpf-global-var.c b/tools/build/feature/test-clang-bpf-global-var.c