From: bot+bpf-ci@kernel.org
To: irogers@google.com,peterz@infradead.org,mingo@redhat.com,acme@kernel.org,namhyung@kernel.org,jolsa@kernel.org,irogers@google.com,adrian.hunter@intel.com,qmo@kernel.org,jpoimboe@kernel.org
Cc: daniel@iogearbox.net,andrii@kernel.org,eddyz87@gmail.com,memxor@gmail.com,martin.lau@linux.dev,song@kernel.org,yonghong.song@linux.dev,james.clark@linaro.org,leo.yan@arm.com,linux-perf-users@vger.kernel.org,bpf@vger.kernel.org,linux-kernel@vger.kernel.org,ast@kernel.org,andrii@kernel.org,daniel@iogearbox.net,martin.lau@kernel.org,eddyz87@gmail.com,yonghong.song@linux.dev,mason@kernel.org,ihor.solodrai@linux.dev
Subject: Re: [PATCH v3 1/4] tools build: Add explicitly sequenced -lzstd to libbfd feature fallback
Date: Wed, 4 Nov 2026 05:03:56 +0000 (UTC) [thread overview]
Message-ID: <d94520950f855a1d5ac4b51975988b70185ba7da61836aa84b044b69e8104bbc@mail.kernel.org> (raw)
In-Reply-To: <20261104043006.1199857-2-irogers@google.com>
[-- Attachment #1: Type: text/plain, Size: 2680 bytes --]
> tools build: Add explicitly sequenced -lzstd to libbfd feature fallback
TL;DR: Possible build break at this commit: the libbfd -lzstd fallback is
removed but no consumer uses the new feature test yet, so perf may fail to
link and bpftool may lose JIT disassembly.
> diff --git a/tools/build/feature/Makefile b/tools/build/feature/Makefile
> --- a/tools/build/feature/Makefile
> +++ b/tools/build/feature/Makefile
[ ... ]
> @@ -249,18 +250,21 @@ $(OUTPUT)test-python-module.bin:
> $(BUILD) $(FLAGS_PYTHON_EMBED)
>
> $(OUTPUT)test-libbfd.bin:
> - $(BUILD_BFD) || $(BUILD_BFD) -lzstd
> + $(BUILD_BFD)
>
> $(OUTPUT)test-libbfd-threadsafe.bin:
> - $(BUILD_BFD) || $(BUILD_BFD) -lzstd || $(BUILD_BFD) -liberty || $(BUILD_BFD) -liberty -lz
> + $(BUILD_BFD) || $(BUILD_BFD) -liberty || $(BUILD_BFD) -liberty -lz || \
> + $(BUILD_BFD) -liberty -lz -lzstd
Can this leave perf and bpftool unable to link libbfd at this commit?
Nothing here reads the new libbfd-liberty-z-zstd result. Neither
tools/perf/Makefile.config nor tools/bpf/bpftool/Makefile calls
feature_check for it or has a branch that uses it.
On a system where "-lbfd -ldl" fails but "-lbfd -ldl -lzstd" links, the
parent commit gave feature-libbfd=1 through the removed fallback. Here
feature-libbfd, feature-libbfd-liberty and feature-libbfd-liberty-z are
all 0, while feature-libbfd-threadsafe is 1 through the new
"-liberty -lz -lzstd" fallback.
With BUILD_NONDISTRO=1, perf's Makefile.config then passes the threadsafe
check but takes none of the EXTLIBS branches:
ifeq ($(feature-libbfd), 1)
EXTLIBS += -lbfd -lopcodes
else ifeq ($(feature-libbfd-liberty), 1)
EXTLIBS += -lbfd -lopcodes -liberty
else ifeq ($(feature-libbfd-liberty-z), 1)
EXTLIBS += -lbfd -lopcodes -liberty -lz
endif
CFLAGS += -DHAVE_LIBBFD_SUPPORT
util/libbfd.o is still built, so the perf link can fail with undefined
references to bfd_openr(), bfd_check_format() and disassembler(). bpftool
goes down the same chain, silently drops -lbfd and -DHAVE_LIBBFD_SUPPORT,
and loses JIT disassembly.
The consumers are added later in the series:
6eb66acc776f ("perf build: Add explicitly sequenced -lzstd to libbfd
feature fallback")
155513d3a59d ("bpftool: Add explicitly sequenced -lzstd to libbfd
feature fallback")
Would it be better to keep the old -lzstd fallback until those consumers
land, or to reorder or squash so that each commit remains buildable?
---
AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
CI run summary: https://github.com/kernel-patches/bpf/actions/runs/41774922004
next prev parent reply other threads:[~2026-11-04 5:03 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-04 4:30 [PATCH v3 0/4] tools build: Fixes for libbfd -lzstd dependency Ian Rogers
2026-11-04 4:30 ` [PATCH v3 1/4] tools build: Add explicitly sequenced -lzstd to libbfd feature fallback Ian Rogers
2026-11-04 5:03 ` bot+bpf-ci [this message]
2026-11-04 4:30 ` [PATCH v3 2/4] perf " Ian Rogers
2026-11-04 4:30 ` [PATCH v3 3/4] bpftool: " Ian Rogers
2026-11-04 4:30 ` [PATCH v3 4/4] objtool: Add explicitly sequenced -lzstd to libopcodes fallback Ian Rogers
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