Re: [PATCH v2 3/6] perf: build: Only link libebl.a for old libdw
From: Namhyung Kim
Date: Fri Jun 21 2024 - 19:40:51 EST
On Mon, Jun 10, 2024 at 10:54:30AM +0100, Leo Yan wrote:
> Since libdw version 0.177, elfutils has merged libebl.a into libdw (see
> the commit "libebl: Don't install libebl.a, libebl.h and remove backends
> from spec." in the elfutils repository).
>
> As a result, libebl.a does not exist on Debian Bullseye and newer
> releases, causing static perf builds to fail on these distributions.
What about libebl.so? I'm curious why it's ok with dynamic build and
causing a problem with static builds.
>
> This commit checks the libdw version and only links libebl.a if it
> detects that the libdw version is older than 0.177.
Have you tested on the older versions too?
>
> Signed-off-by: Leo Yan <leo.yan@xxxxxxx>
> ---
> tools/build/feature/Makefile | 12 +++++++++++-
> tools/perf/Makefile.config | 12 +++++++++++-
> 2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
> index 084f803093c3..b23b3e8ad5e4 100644
> --- a/tools/build/feature/Makefile
> +++ b/tools/build/feature/Makefile
> @@ -171,7 +171,17 @@ $(OUTPUT)test-libopencsd.bin:
>
> DWARFLIBS := -ldw
> ifeq ($(findstring -static,${LDFLAGS}),-static)
> -DWARFLIBS += -lelf -lebl -lz -llzma -lbz2
> + DWARFLIBS += -lelf -lz -llzma -lbz2
> +
> + LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw)
> + LIBDW_VERSION_1 := $(word 1, $(subst ., ,$(LIBDW_VERSION)))
> + LIBDW_VERSION_2 := $(word 2, $(subst ., ,$(LIBDW_VERSION)))
> +
> + # Elfutils merged libebl.a into libdw.a starting from version 0.177,
> + # Link libebl.a only if libdw is older than this version.
> + ifeq ($(shell test $(LIBDW_VERSION_2) -lt 177; echo $$?),0)
> + DWARFLIBS += -lebl
I'm not sure if it's ok to change the order as libebl might depend on
later libraries like libz.
Thanks,
Namhyung
> + endif
> endif
>
> $(OUTPUT)test-dwarf.bin:
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index 755fb78be76a..db3bc460d4c2 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -152,7 +152,17 @@ ifdef LIBDW_DIR
> endif
> DWARFLIBS := -ldw
> ifeq ($(findstring -static,${LDFLAGS}),-static)
> - DWARFLIBS += -lelf -lebl -ldl -lz -llzma -lbz2
> + DWARFLIBS += -lelf -ldl -lz -llzma -lbz2
> +
> + LIBDW_VERSION := $(shell $(PKG_CONFIG) --modversion libdw)
> + LIBDW_VERSION_1 := $(word 1, $(subst ., ,$(LIBDW_VERSION)))
> + LIBDW_VERSION_2 := $(word 2, $(subst ., ,$(LIBDW_VERSION)))
> +
> + # Elfutils merged libebl.a into libdw.a starting from version 0.177,
> + # Link libebl.a only if libdw is older than this version.
> + ifeq ($(shell test $(LIBDW_VERSION_2) -lt 177; echo $$?),0)
> + DWARFLIBS += -lebl
> + endif
> endif
> FEATURE_CHECK_CFLAGS-libdw-dwarf-unwind := $(LIBDW_CFLAGS)
> FEATURE_CHECK_LDFLAGS-libdw-dwarf-unwind := $(LIBDW_LDFLAGS) $(DWARFLIBS)
> --
> 2.34.1
>