2023-10-16 11:55:55

by Akihiko Odaki

Subject: [PATCH v2] selftests/bpf: Use pkg-config to determine ld flags

When linking statically, libraries may require other dependencies to be
included to ld flags. In particular, libelf may require libzstd. Use
pkg-config to determine such dependencies.

Signed-off-by: Akihiko Odaki <[email protected]>
---
V1 -> V2: Implemented fallback, referring to HOSTPKG_CONFIG.

tools/testing/selftests/bpf/Makefile | 3 ++-
tools/testing/selftests/bpf/README.rst | 2 +-
2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/Makefile b/tools/testing/selftests/bpf/Makefile
index caede9b574cb..4b947040d6d4 100644
--- a/tools/testing/selftests/bpf/Makefile
+++ b/tools/testing/selftests/bpf/Makefile
@@ -4,6 +4,7 @@ include ../../../scripts/Makefile.arch
include ../../../scripts/Makefile.include

CXX ?= $(CROSS_COMPILE)g++
+PKG_CONFIG ?= $(CROSS_COMPILE)pkg-config

CURDIR := $(abspath .)
TOOLSDIR := $(abspath ../../..)
@@ -31,7 +32,7 @@ CFLAGS += -g -O0 -rdynamic -Wall -Werror $(GENFLAGS) $(SAN_CFLAGS) \
-I$(CURDIR) -I$(INCLUDE_DIR) -I$(GENDIR) -I$(LIBDIR) \
-I$(TOOLSINCDIR) -I$(APIDIR) -I$(OUTPUT)
LDFLAGS += $(SAN_LDFLAGS)
-LDLIBS += -lelf -lz -lrt -lpthread
+LDLIBS += $(shell $(PKG_CONFIG) --libs libelf zlib || -lelf -lz) -lrt -lpthread

ifneq ($(LLVM),)
# Silence some warnings when compiled with clang
diff --git a/tools/testing/selftests/bpf/README.rst b/tools/testing/selftests/bpf/README.rst
index cb9b95702ac6..9af79c7a9b58 100644
--- a/tools/testing/selftests/bpf/README.rst
+++ b/tools/testing/selftests/bpf/README.rst
@@ -77,7 +77,7 @@ In case of linker errors when running selftests, try using static linking:

.. code-block:: console

- $ LDLIBS=-static vmtest.sh
+ $ LDLIBS=-static PKG_CONFIG='pkg-config --static' vmtest.sh

.. note:: Some distros may not support static linking.

--
2.42.0

2023-10-16 12:19:43

by Daniel Borkmann

Subject: Re: [PATCH v2] selftests/bpf: Use pkg-config to determine ld flags

On 10/16/23 1:54 PM, Akihiko Odaki wrote:
> When linking statically, libraries may require other dependencies to be
> included to ld flags. In particular, libelf may require libzstd. Use
> pkg-config to determine such dependencies.
>
> Signed-off-by: Akihiko Odaki <[email protected]>
> ---
> V1 -> V2: Implemented fallback, referring to HOSTPKG_CONFIG.

This still does not work with BPF CI, BPF selftest build fails again :

https://github.com/kernel-patches/bpf/actions/runs/6524480596/job/17716169959 :

[...]
make: pkg-config: Command not found
BINARY xdping
HOSTLD /tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/build/resolve_btfids/fixdep-in.o
/usr/bin/x86_64-linux-gnu-ld: /usr/bin/x86_64-linux-gnu-ld: DWARF error: invalid or unhandled FORM value: 0x25
/tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a(libbpf-in.o): in function `bpf_object_open':
libbpf.c:(.text+0x2871): undefined reference to `elf_version'
/usr/bin/x86_64-linux-gnu-ld: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a(libbpf-in.o): in function `bpf_object__elf_finish':
libbpf.c:(.text+0x4ccf): undefined reference to `elf_end'
/usr/bin/x86_64-linux-gnu-ld: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a(libbpf-in.o): in function `elf_find_func_offset_from_archive':
libbpf.c:(.text+0xb419): undefined reference to `elf_memory'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0xb447): undefined reference to `elf_errmsg'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0xb4e2): undefined reference to `elf_end'
/usr/bin/x86_64-linux-gnu-ld: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a(libbpf-in.o): in function `bpf_object__elf_init':
libbpf.c:(.text+0x10b02): undefined reference to `elf_memory'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10bae): undefined reference to `elf_begin'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10bdd): undefined reference to `elf_errmsg'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10c1b): undefined reference to `elf_kind'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10c54): undefined reference to `gelf_getclass'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10c8d): undefined reference to `elf64_getehdr'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10cd1): undefined reference to `elf_errmsg'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10d0f): undefined reference to `elf_getshdrstrndx'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10d38): undefined reference to `elf_errmsg'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10d72): undefined reference to `elf_getscn'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10d7e): undefined reference to `elf_rawdata'
/usr/bin/x86_64-linux-gnu-ld: libbpf.c:(.text+0x10da8): undefined reference to `elf_errmsg'
/usr/bin/x86_64-linux-gnu-ld: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/tools/build/libbpf/libbpf.a(libbpf-in.o): in function `bpf_object__elf_collect':
libbpf.c:(.text+0x10f17): undefined reference to `elf_getshdrnum'

2023-10-16 12:47:10

by Akihiko Odaki

Subject: Re: [PATCH v2] selftests/bpf: Use pkg-config to determine ld flags

On 2023/10/16 21:19, Daniel Borkmann wrote:
> On 10/16/23 1:54 PM, Akihiko Odaki wrote:
>> When linking statically, libraries may require other dependencies to be
>> included to ld flags. In particular, libelf may require libzstd. Use
>> pkg-config to determine such dependencies.
>>
>> Signed-off-by: Akihiko Odaki <[email protected]>
>> ---
>> V1 -> V2: Implemented fallback, referring to HOSTPKG_CONFIG.
>
> This still does not work with BPF CI, BPF selftest build fails again :
>
> https://github.com/kernel-patches/bpf/actions/runs/6524480596/job/17716169959 :

I was so careless forgetting to put "echo". I have just sent v3.