[PATCH] tools/resolve_btfids: Use pkg-config to locate libelf

[PATCH] tools/resolve_btfids: Use pkg-config to locate libelf

[Shen Jiamin]

When libelf was not installed in the standard location, it cannot be
located by the current building config.

Use pkg-config to help locate libelf in such cases.

Signed-off-by: Shen Jiamin <shen_jiamin@comp.nus.edu.sg>
---
 tools/bpf/resolve_btfids/Makefile | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
index 19a3112e271a..5dcc31e01149 100644
--- a/tools/bpf/resolve_btfids/Makefile
+++ b/tools/bpf/resolve_btfids/Makefile
@@ -56,11 +56,17 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OU
 		    DESTDIR=$(LIBBPF_DESTDIR) prefix= EXTRA_CFLAGS="$(CFLAGS)" \
 		    $(abspath $@) install_headers

+LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null)
+LIBELF_LIBS  := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
+
 CFLAGS += -g \
           -I$(srctree)/tools/include \
           -I$(srctree)/tools/include/uapi \
           -I$(LIBBPF_INCLUDE) \
-          -I$(SUBCMD_SRC)
+          -I$(SUBCMD_SRC) \
+          $(LIBELF_FLAGS)
+
+LDFLAGS +=  $(LIBELF_LIBS)

 LIBS = -lelf -lz

--
2.34.1

Re: [PATCH] tools/resolve_btfids: Use pkg-config to locate libelf

[Jiri Olsa]

On Wed, Dec 14, 2022 at 11:20:37PM +0800, Shen Jiamin wrote:
> When libelf was not installed in the standard location, it cannot be
> located by the current building config.
> 
> Use pkg-config to help locate libelf in such cases.
> 
> Signed-off-by: Shen Jiamin <shen_jiamin@comp.nus.edu.sg>
> ---
>  tools/bpf/resolve_btfids/Makefile | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
> index 19a3112e271a..5dcc31e01149 100644
> --- a/tools/bpf/resolve_btfids/Makefile
> +++ b/tools/bpf/resolve_btfids/Makefile
> @@ -56,11 +56,17 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OU
>  		    DESTDIR=$(LIBBPF_DESTDIR) prefix= EXTRA_CFLAGS="$(CFLAGS)" \
>  		    $(abspath $@) install_headers
> 
> +LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null)
> +LIBELF_LIBS  := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
> +
>  CFLAGS += -g \
>            -I$(srctree)/tools/include \
>            -I$(srctree)/tools/include/uapi \
>            -I$(LIBBPF_INCLUDE) \
> -          -I$(SUBCMD_SRC)
> +          -I$(SUBCMD_SRC) \
> +          $(LIBELF_FLAGS)
> +
> +LDFLAGS +=  $(LIBELF_LIBS)
> 
>  LIBS = -lelf -lz

now we can remove -lelf from LIBS.. or we could do:

  LIBS = $(LIBELF_LIBS) -lz

jirka

Re: [PATCH] tools/resolve_btfids: Use pkg-config to locate libelf

[Shen Jiamin]

Thank you, jirka, for your comment.
Actually we can put that `LIBELF_LIBS` into `LIBS` directly.
I've submitted a new patch.

https://lore.kernel.org/bpf/20221215044703.400139-1-shen_jiamin@comp.nus.edu.sg/

Jiamin