resolve_btfids: Fix linker flags detection

The "|| echo -lzstd" default makes zstd an unconditional link dependency of resolve_btfids. On systems where libzstd-dev is not installed and pkg-config fails, the linker fails: ld: cannot find -lzstd: No such file or directory libzstd is a transitive dependency of libelf, so the -lzstd flag is strictly necessary only for static builds [1]. Remove ZSTD_LIBS variable, and instead set LIBELF_LIBS depending on whether the build is static or not. Use $(HOSTPKG_CONFIG) as primary source of the flags list. Also add a default value for HOSTPKG_CONFIG in case it's not built via the toplevel Makefile. Pass it from selftests/bpf too. [1] https://lore.kernel.org/bpf/4ff82800-2daa-4b9f-95a9-6f512859ee70@linux.dev/

Ihor Solodrai committed 8 months ago

Commit b0dcdcb1 parent 325d1ba2 files · +8 −2Browse files

Unified · Split

2 files

tools/bpf/resolve_btfids/Makefile +7 −2
tools/testing/selftests/bpf/Makefile +1 −0

tools/bpf/resolve_btfids/Makefile+7−2

@@ -23,6 +23,7 @@ RM ?= rm · 22 unmodified lines
23	23	HOSTCC ?= gcc
24	24	HOSTLD ?= ld
25	25	HOSTAR ?= ar
	26	+HOSTPKG_CONFIG ?= pkg-config
26	27	CROSS_COMPILE =
27	28
28	29	OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/
@@ -63,10 +64,14 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) \| $(LIBBPF_OU · 34 unmodified lines
63	64	$(abspath $@) install_headers
64	65
65	66	LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null)
	67	+
	68	+ifneq ($(filter -static,$(EXTRA_LDFLAGS)),)
	69	+LIBELF_LIBS := $(shell $(HOSTPKG_CONFIG) libelf --libs --static 2>/dev/null \|\| echo -lelf -lzstd)
	70	+else
66	71	LIBELF_LIBS := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null \|\| echo -lelf)
	72	+endif
67	73
68	74	ZLIB_LIBS := $(shell $(HOSTPKG_CONFIG) zlib --libs 2>/dev/null \|\| echo -lz)
69		−ZSTD_LIBS := $(shell $(HOSTPKG_CONFIG) libzstd --libs 2>/dev/null \|\| echo -lzstd)
70	75
71	76	HOSTCFLAGS_resolve_btfids += -g \
72	77	-I$(srctree)/tools/include \
@@ -76,7 +81,7 @@ HOSTCFLAGS_resolve_btfids += -g \ · 3 unmodified lines
76	81	$(LIBELF_FLAGS) \
77	82	-Wall -Werror
78	83
79		−LIBS = $(LIBELF_LIBS) $(ZLIB_LIBS) $(ZSTD_LIBS)
	84	+LIBS = $(LIBELF_LIBS) $(ZLIB_LIBS)
80	85
81	86	export srctree OUTPUT HOSTCFLAGS_resolve_btfids Q HOSTCC HOSTLD HOSTAR
82	87	include $(srctree)/tools/build/Makefile.include

tools/testing/selftests/bpf/Makefile+1−0

@@ -409,6 +409,7 @@ $(RESOLVE_BTFIDS): $(HOST_BPFOBJ) \| $(HOST_BUILD_DIR)/resolve_btfids \ · 408 unmodified lines
409	409	CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)" \
410	410	LIBBPF_INCLUDE=$(HOST_INCLUDE_DIR) \
411	411	EXTRA_LDFLAGS='$(SAN_LDFLAGS) $(EXTRA_LDFLAGS)' \
	412	+ HOSTPKG_CONFIG=$(PKG_CONFIG) \
412	413	OUTPUT=$(HOST_BUILD_DIR)/resolve_btfids/ BPFOBJ=$(HOST_BPFOBJ)
413	414
414	415	# Get Clang's default includes on this system, as opposed to those seen by