libbpf: Re-build libbpf.so when libbpf.map changes

[ Upstream commit 61c7aa5020e98ac2fdcf07d07eec1baf2e9f0a08 ]

Ensure libbpf.so is re-built whenever libbpf.map is modified.  Without this,
changes to libbpf.map are not detected and versioned symbols mismatch error
will be reported until `make clean && make` is used, which is a suboptimal
developer experience.

Fixes: 306b267cb3c4 ("libbpf: Verify versioned symbols")
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20210815070609.987780-8-andrii@kernel.org
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index 310f647..154b75f 100644 (file)
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -4,8 +4,9 @@
 RM ?= rm
 srctree = $(abs_srctree)
 
+VERSION_SCRIPT := libbpf.map
 LIBBPF_VERSION := $(shell \
-       grep -oE '^LIBBPF_([0-9.]+)' libbpf.map | \
+       grep -oE '^LIBBPF_([0-9.]+)' $(VERSION_SCRIPT) | \
        sort -rV | head -n1 | cut -d'_' -f2)
 LIBBPF_MAJOR_VERSION := $(firstword $(subst ., ,$(LIBBPF_VERSION)))
 
@@ -131,7 +132,6 @@ SHARED_OBJDIR       := $(OUTPUT)sharedobjs/
 STATIC_OBJDIR  := $(OUTPUT)staticobjs/
 BPF_IN_SHARED  := $(SHARED_OBJDIR)libbpf-in.o
 BPF_IN_STATIC  := $(STATIC_OBJDIR)libbpf-in.o
-VERSION_SCRIPT := libbpf.map
 BPF_HELPER_DEFS        := $(OUTPUT)bpf_helper_defs.h
 
 LIB_TARGET     := $(addprefix $(OUTPUT),$(LIB_TARGET))
@@ -184,10 +184,10 @@ $(BPF_HELPER_DEFS): $(srctree)/tools/include/uapi/linux/bpf.h
 
 $(OUTPUT)libbpf.so: $(OUTPUT)libbpf.so.$(LIBBPF_VERSION)
 
-$(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN_SHARED)
+$(OUTPUT)libbpf.so.$(LIBBPF_VERSION): $(BPF_IN_SHARED) $(VERSION_SCRIPT)
        $(QUIET_LINK)$(CC) $(LDFLAGS) \
                --shared -Wl,-soname,libbpf.so.$(LIBBPF_MAJOR_VERSION) \
-               -Wl,--version-script=$(VERSION_SCRIPT) $^ -lelf -lz -o $@
+               -Wl,--version-script=$(VERSION_SCRIPT) $< -lelf -lz -o $@
        @ln -sf $(@F) $(OUTPUT)libbpf.so
        @ln -sf $(@F) $(OUTPUT)libbpf.so.$(LIBBPF_MAJOR_VERSION)
 
@@ -202,7 +202,7 @@ $(OUTPUT)libbpf.pc:
 
 check: check_abi
 
-check_abi: $(OUTPUT)libbpf.so
+check_abi: $(OUTPUT)libbpf.so $(VERSION_SCRIPT)
        @if [ "$(GLOBAL_SYM_COUNT)" != "$(VERSIONED_SYM_COUNT)" ]; then  \
                echo "Warning: Num of global symbols in $(BPF_IN_SHARED)"        \
                     "($(GLOBAL_SYM_COUNT)) does NOT match with num of"  \