xdp-tools: Feature detection for bpftool

Add bpftool feature detection to generate necessarily BPF skeletons from
the BPF objects we build.

Signed-off-by: Kumar Kartikeya Dwivedi <[email protected]>
[ Support skeletons in common.mk, make bpftool and clang-11 hard dependencies ]
Signed-off-by: Toke Høiland-Jørgensen <[email protected]>

Author: kkdwivedi

.gitignore

@@ -63,3 +63,6 @@ xdp-dispatcher.c
 .clangd
 .cache
 compile_commands.json
+
+# BPF skeleton files
+*.skel.h

configure

@@ -39,7 +39,7 @@ find_tool()
 
     # we're looking for a binary with the same name as tool_name; try version
     # suffixes in order until we find one
-    for v in 16 15 14 13 12 11 10; do
+    for v in 16 15 14 13 12 11; do
         tool_path="${tool_name}-$v"
         if command -v "$tool_path" >/dev/null 2>&1; then
             echo $tool_path
@@ -55,6 +55,7 @@ check_toolchain()
 {
     local emacs_version
     local clang_version
+    local bpftool_version
 
     : ${PKG_CONFIG:=pkg-config}
     : ${CC=gcc}
@@ -64,12 +65,13 @@ check_toolchain()
     : ${LLC=llc}
     : ${M4=m4}
     : ${EMACS=emacs}
+    : ${BPFTOOL=bpftool}
     : ${ARCH_INCLUDES=}
 
     CLANG=$(find_tool clang "$CLANG")
     LLC=$(find_tool llc "$LLC")
 
-    for TOOL in $PKG_CONFIG $CC $LD $OBJCOPY $CLANG $LLC $M4; do
+    for TOOL in $PKG_CONFIG $CC $LD $OBJCOPY $CLANG $LLC $M4 $BPFTOOL; do
         if [ ! $(command -v ${TOOL} 2>/dev/null) ]; then
             echo "*** ERROR: Cannot find tool ${TOOL}" ;
             exit 1;
@@ -83,8 +85,8 @@ check_toolchain()
     fi
 
     echo "Found clang binary '$CLANG' with version $clang_version (from '$($CLANG --version | head -n 1)')"
-    if [ "$clang_version" -lt "10" ]; then
-        echo "*** ERROR: Need LLVM version 10+, '$CLANG' is version $clang_version"
+    if [ "$clang_version" -lt "11" ]; then
+        echo "*** ERROR: Need LLVM version 11+, '$CLANG' is version $clang_version"
         [ -n "$RELAXED_LLVM_VERSION" ] || exit 1
     fi
 
@@ -106,6 +108,14 @@ check_toolchain()
         exit 1
     fi
 
+    if $BPFTOOL gen help 2>&1 | grep 'gen help' > /dev/null; then
+        bpftool_version=$($BPFTOOL version | head -n 1)
+	echo "using $bpftool_version"
+    else
+	echo "bpftool doesn't support skeleton generation"
+        exit 1
+    fi
+
     if [ -z "$ARCH_INCLUDES" ]; then
         for dir in $(echo | $CC -Wp,-v -E - 2>&1 | grep '^ '); do
             local idir
@@ -123,6 +133,7 @@ check_toolchain()
     echo "M4:=${M4}" >>$CONFIG
     echo "EMACS:=${EMACS}" >>$CONFIG
     echo "ARCH_INCLUDES:=$ARCH_INCLUDES" >> $CONFIG
+    echo "BPFTOOL:=${BPFTOOL}" >> $CONFIG
 }
 
 check_zlib()

lib/common.mk

@@ -12,6 +12,8 @@
 #
 XDP_C = ${XDP_TARGETS:=.c}
 XDP_OBJ = ${XDP_C:.c=.o}
+BPF_SKEL_OBJ = ${BPF_SKEL_TARGETS:=.o}
+BPF_SKEL_H = ${BPF_SKEL_OBJ:.bpf.o=.skel.h}
 USER_C := ${USER_TARGETS:=.c}
 USER_OBJ := ${USER_C:.c=.o}
 TEST_C := ${TEST_TARGETS:=.c}
@@ -63,7 +65,7 @@ all: $(USER_TARGETS) $(XDP_OBJ) $(EXTRA_TARGETS) $(TEST_TARGETS) man
 
 .PHONY: clean
 clean::
-	$(Q)rm -f $(USER_TARGETS) $(XDP_OBJ) $(USER_OBJ) $(TEST_OBJ) $(USER_GEN) *.ll
+	$(Q)rm -f $(USER_TARGETS) $(XDP_OBJ) $(USER_OBJ) $(TEST_OBJ) $(USER_GEN) $(BPF_SKEL_H) *.ll
 
 .PHONY: install
 install: all install_local
@@ -100,7 +102,7 @@ $(LIB_OBJS): %.o: %.c %.h $(LIB_H)
 	$(Q)$(MAKE) -C $(dir $@) $(notdir $@)
 
 ALL_EXEC_TARGETS=$(USER_TARGETS) $(TEST_TARGETS)
-$(ALL_EXEC_TARGETS): %: %.c  $(OBJECT_LIBBPF) $(OBJECT_LIBXDP) $(LIBMK) $(LIB_OBJS) $(KERN_USER_H) $(EXTRA_DEPS) $(EXTRA_USER_DEPS)
+$(ALL_EXEC_TARGETS): %: %.c  $(OBJECT_LIBBPF) $(OBJECT_LIBXDP) $(LIBMK) $(LIB_OBJS) $(KERN_USER_H) $(EXTRA_DEPS) $(EXTRA_USER_DEPS) $(BPF_SKEL_H)
 	$(QUIET_CC)$(CC) -Wall $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) -o $@ $(LIB_OBJS) \
 	 $< $(LDLIBS)
 
@@ -117,6 +119,9 @@ $(XDP_OBJ): %.o: %.c $(KERN_USER_H) $(EXTRA_DEPS) $(BPF_HEADERS) $(LIBMK)
 	    -O2 -emit-llvm -c -g -o ${@:.o=.ll} $<
 	$(QUIET_LLC)$(LLC) -march=$(BPF_TARGET) -filetype=obj -o $@ ${@:.o=.ll}
 
+$(BPF_SKEL_H): %.skel.h: %.bpf.o
+	$(QUIET_GEN)$(BPFTOOL) gen skeleton $< name ${@:.skel.h=} > $@
+
 .PHONY: man
 ifeq ($(EMACS),)
 man: ;