From: Ihor Solodrai <ihor.solodrai@linux.dev>
To: Vitaly Chikunov <vt@altlinux.org>
Cc: bot+bpf-ci@kernel.org, ast@kernel.org, andrii@kernel.org,
daniel@iogearbox.net, eddyz87@gmail.com, olsajiri@gmail.com,
yatsenko@meta.com, alexis.lothore@bootlin.com,
ameryhung@gmail.com, bpf@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel-team@meta.com,
martin.lau@kernel.org, yonghong.song@linux.dev, clm@meta.com
Subject: Re: [PATCH bpf v3 01/15] selftests/bpf: Pass through build flags to bpftool and resolve_btfids
Date: Mon, 2 Mar 2026 10:01:59 -0800 [thread overview]
Message-ID: <d6fda426-b59f-48d6-bbe7-b2069a7e352e@linux.dev> (raw)
In-Reply-To: <aaWqMcK-2AQw5dx8@altlinux.org>
On 3/2/26 7:22 AM, Vitaly Chikunov wrote:
> Ihor,
>
> On Fri, Feb 20, 2026 at 08:23:51PM -0800, Ihor Solodrai wrote:
>>
>>
>> On 2/20/26 2:57 PM, bot+bpf-ci@kernel.org wrote:
>>>> diff --git a/tools/bpf/resolve_btfids/Makefile b/tools/bpf/resolve_btfids/Makefile
>>>> index 1733a6e93a07..ef083602b73a 100644
>>>> --- a/tools/bpf/resolve_btfids/Makefile
>>>> +++ b/tools/bpf/resolve_btfids/Makefile
>>>> @@ -65,6 +65,9 @@ $(BPFOBJ): $(wildcard $(LIBBPF_SRC)/*.[ch] $(LIBBPF_SRC)/Makefile) | $(LIBBPF_OU
>>>> LIBELF_FLAGS := $(shell $(HOSTPKG_CONFIG) libelf --cflags 2>/dev/null)
>>>> LIBELF_LIBS := $(shell $(HOSTPKG_CONFIG) libelf --libs 2>/dev/null || echo -lelf)
>>>>
>>>> +ZLIB_LIBS := $(shell $(HOSTPKG_CONFIG) zlib --libs 2>/dev/null || echo -lz)
>>>> +ZSTD_LIBS := $(shell $(HOSTPKG_CONFIG) libzstd --libs 2>/dev/null || echo -lzstd)
>>>
>>> The "|| echo -lzstd" fallback makes zstd an unconditional link
>>> dependency. On systems where libzstd-dev is not installed, pkg-config
>>> fails and the fallback provides -lzstd, but the linker cannot find the
>>> library and the build fails.
>>>
>>> bpftool handles the same transitive dependency conditionally via a
>>> feature test:
>>>
>>> tools/bpf/bpftool/Makefile:
>>> ifeq ($(feature-libelf-zstd),1)
>>> LIBS += -lzstd
>>> LIBS_BOOTSTRAP += -lzstd
>>> endif
>>>
>>> Would it be safer to drop the fallback here so ZSTD_LIBS is empty
>>> when zstd is not available?
>>>
>>> ZSTD_LIBS := $(shell $(HOSTPKG_CONFIG) libzstd --libs 2>/dev/null)
>>>
>>> This would still link zstd when present (needed for the static linking
>>> case where libelf.a pulls in ZSTD symbols from elf_compress.o), but
>>> avoid breaking dynamic builds on systems without libzstd-dev.
>>
>> [...]
>>
>>
>> So, while AI may be technically correct that the build will fail if
>> libelf is installed and libzstd is not, it seems a far-fetched
>> situation, given that libelf depends on libzstd.
>
> This is not far-fetched, and we have build failure for v7.0-rc2 due to
> this.
>
> ld: cannot find -lzstd: No such file or directory
>
> Even though libelf is linked with libzstd, this does not imply
> libzstd-devel (with headers and so library) is there when building.
Does AI's suggestion make sense in your case then?
That is, make ZSTD_LIBS empty in case pkg-config didn't find libzstd?
I'm happy to fix this, the build shouldn't fail unless it must.
But I am curious how and why an environment building Linux with BTF
(requiring build and run of resolve_btfids), which needs libelf-dev
and presumably its dependencies, would exclude/avoid installing
libzstd-dev?
Thanks.
>
> Thanks,
>
>>
>> I think we can leave the default -lzstd to have an explicit
>> dependency in the Makefile.
>>
>>
>>>
>>> [ ... ]
next prev parent reply other threads:[~2026-03-02 18:02 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-02-20 22:25 [PATCH bpf v3 00/15] selftests/bpf: Fixes for userspace ASAN Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 01/15] selftests/bpf: Pass through build flags to bpftool and resolve_btfids Ihor Solodrai
2026-02-20 22:57 ` bot+bpf-ci
2026-02-21 4:23 ` Ihor Solodrai
2026-03-02 15:22 ` Vitaly Chikunov
2026-03-02 18:01 ` Ihor Solodrai [this message]
2026-03-02 20:27 ` Vitaly Chikunov
2026-03-02 22:42 ` Ihor Solodrai
2026-03-03 4:01 ` Vitaly Chikunov
2026-02-20 22:25 ` [PATCH bpf v3 02/15] resolve_btfids: Fix memory leaks reported by ASAN Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 03/15] selftests/bpf: Add DENYLIST.asan Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 04/15] selftests/bpf: Refactor bpf_get_ksyms() trace helper Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 05/15] selftests/bpf: Fix memory leaks in tests Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 06/15] selftests/bpf: Fix cleanup in check_fd_array_cnt__fd_array_too_big() Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 07/15] veristat: Fix a memory leak for preset ENUMERATOR Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 08/15] selftests/bpf: Fix use-after-free in xdp_metadata test Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 09/15] selftests/bpf: Fix double thread join in uprobe_multi_test Ihor Solodrai
2026-02-20 22:25 ` [PATCH bpf v3 10/15] selftests/bpf: Fix resource leaks caused by missing cleanups Ihor Solodrai
2026-02-20 22:26 ` [PATCH bpf v3 11/15] selftests/bpf: Free bpf_object in test_sysctl Ihor Solodrai
2026-02-20 22:26 ` [PATCH bpf v3 12/15] selftests/bpf: Fix array bounds warning in jit_disasm_helpers Ihor Solodrai
2026-02-20 22:26 ` [PATCH bpf v3 13/15] selftests/bpf: Fix out-of-bounds array access bugs reported by ASAN Ihor Solodrai
2026-02-20 22:26 ` [PATCH bpf v3 14/15] selftests/bpf: Check BPFTOOL env var in detect_bpftool_path() Ihor Solodrai
2026-02-20 22:26 ` [PATCH bpf v3 15/15] selftests/bpf: Don't override SIGSEGV handler with ASAN Ihor Solodrai
2026-02-21 0:52 ` Eduard Zingerman
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