Commit b0dcdcb9 authored by Ihor Solodrai's avatar Ihor Solodrai Committed by Alexei Starovoitov
Browse files

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/



Reported-by: default avatarBPF CI Bot (Claude Opus 4.6) <bot+bpf-ci@kernel.org>
Reported-by: default avatarVitaly Chikunov <vt@altlinux.org>
Closes: https://lore.kernel.org/bpf/aaWqMcK-2AQw5dx8@altlinux.org/


Fixes: 4021848a ("selftests/bpf: Pass through build flags to bpftool and resolve_btfids")
Signed-off-by: default avatarIhor Solodrai <ihor.solodrai@linux.dev>
Reviewed-by: default avatarPaul Chaignon <paul.chaignon@gmail.com>
Link: https://lore.kernel.org/r/20260305014730.3123382-1-ihor.solodrai@linux.dev


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 325d1ba3

tools/bpf/resolve_btfids/Makefile

+7 −2
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ RM ?= rm 
HOSTCC  ?= gcc

HOSTLD  ?= ld

HOSTAR  ?= ar

HOSTPKG_CONFIG ?= pkg-config

CROSS_COMPILE =



OUTPUT ?= $(srctree)/tools/bpf/resolve_btfids/
@@ -63,10 +64,14 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OU 
		    $(abspath $@) install_headers



LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null)



ifneq ($(filter -static,$(EXTRA_LDFLAGS)),)

LIBELF_LIBS  := $(shell $(HOSTPKG_CONFIG) libelf --libs --static 2>/dev/null || echo -lelf -lzstd)

else

LIBELF_LIBS  := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)

endif



ZLIB_LIBS  := $(shell $(HOSTPKG_CONFIG) zlib --libs 2>/dev/null || echo -lz)

ZSTD_LIBS  := $(shell $(HOSTPKG_CONFIG) libzstd --libs 2>/dev/null || echo -lzstd)



HOSTCFLAGS_resolve_btfids += -g \

          -I$(srctree)/tools/include \
@@ -76,7 +81,7 @@ HOSTCFLAGS_resolve_btfids += -g \ 
          $(LIBELF_FLAGS) \

          -Wall -Werror



LIBS = $(LIBELF_LIBS) $(ZLIB_LIBS) $(ZSTD_LIBS)

LIBS = $(LIBELF_LIBS) $(ZLIB_LIBS)



export srctree OUTPUT HOSTCFLAGS_resolve_btfids Q HOSTCC HOSTLD HOSTAR

include $(srctree)/tools/build/Makefile.include

tools/testing/selftests/bpf/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -409,6 +409,7 @@ $(RESOLVE_BTFIDS): $(HOST_BPFOBJ) | $(HOST_BUILD_DIR)/resolve_btfids \ 
		CC="$(HOSTCC)" LD="$(HOSTLD)" AR="$(HOSTAR)" \

		LIBBPF_INCLUDE=$(HOST_INCLUDE_DIR) \

		EXTRA_LDFLAGS='$(SAN_LDFLAGS) $(EXTRA_LDFLAGS)' \

		HOSTPKG_CONFIG=$(PKG_CONFIG) \

		OUTPUT=$(HOST_BUILD_DIR)/resolve_btfids/ BPFOBJ=$(HOST_BPFOBJ)



# Get Clang's default includes on this system, as opposed to those seen by