linux-kernel - Re: [PATCH 1/1] tools build: Don't set libunwind as available if test-all.c build succeeds

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Message-ID: <Z_K7ruz8hhvCTbL8@gmail.com>
Date: Sun, 6 Apr 2025 19:36:46 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Namhyung Kim <namhyung@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	Dmitry Vyukov <dvyukov@...gle.com>, Ian Rogers <irogers@...gle.com>,
	James Clark <james.clark@...aro.org>, Jiri Olsa <jolsa@...nel.org>,
	Kan Liang <kan.liang@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-perf-users@...r.kernel.org
Subject: Re: [PATCH 1/1] tools build: Don't set libunwind as available if
 test-all.c build succeeds


* Arnaldo Carvalho de Melo <acme@...nel.org> wrote:

> The tools/build/feature/test-all.c file tries to detect the expected,
> most common set of libraries/features we expect to have available to
> build perf with.
> 
> At some point libunwind was deemed not to be part of that set of
> libraries, but the patches making it to be opt-in ended up forgetting
> some details, fix one more.
> 
> Testing it:
> 
>   $ rm -rf /tmp/build/$(basename $PWD)/ ; mkdir -p /tmp/build/$(basename $PWD)/
>   $ rpm -q libunwind-devel
>   libunwind-devel-1.8.0-3.fc40.x86_64
>   $ make -k LIBUNWIND=1 CORESIGHT=1 O=/tmp/build/$(basename $PWD)/ -C tools/perf install-bin |& grep unwind && ldd ~/bin/perf | grep unwind
>   ...                               libunwind: [ on  ]
>     CC      /tmp/build/perf-tools-next/arch/x86/tests/dwarf-unwind.o
>     CC      /tmp/build/perf-tools-next/arch/x86/util/unwind-libunwind.o
>     CC      /tmp/build/perf-tools-next/util/arm64-frame-pointer-unwind-support.o
>     CC      /tmp/build/perf-tools-next/tests/dwarf-unwind.o
>     CC      /tmp/build/perf-tools-next/util/unwind-libunwind-local.o
>     CC      /tmp/build/perf-tools-next/util/unwind-libunwind.o
> 	  libunwind-x86_64.so.8 => /lib64/libunwind-x86_64.so.8 (0x00007f615a549000)
> 	  libunwind.so.8 => /lib64/libunwind.so.8 (0x00007f615a52f000)
>   $ sudo rpm -e libunwind-devel
>   $ rm -rf /tmp/build/$(basename $PWD)/ ; mkdir -p /tmp/build/$(basename $PWD)/
>   $ make -k LIBUNWIND=1 CORESIGHT=1 O=/tmp/build/$(basename $PWD)/ -C tools/perf install-bin |& grep unwind && ldd ~/bin/perf | grep unwind
>   Makefile.config:653: No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR
>   ...                               libunwind: [ OFF ]
>     CC      /tmp/build/perf-tools-next/arch/x86/tests/dwarf-unwind.o
>     CC      /tmp/build/perf-tools-next/arch/x86/util/unwind-libdw.o
>     CC      /tmp/build/perf-tools-next/util/arm64-frame-pointer-unwind-support.o
>     CC      /tmp/build/perf-tools-next/tests/dwarf-unwind.o
>     CC      /tmp/build/perf-tools-next/util/unwind-libdw.o
>   $

So I'm not sure whether this is related to my libunwind-OFF build 
message bugreport, but in case it is, with this patch applied I still 
get this message both before and after applying the patch:

...                               libunwind: [ OFF ]

Note: I did not add any LIBUNWIND parameters to the build, it's a 
standard 'make clean install' perf build:

  $ make clean install
  ...
  BUILD:   Doing 'make -j128' parallel build
  ...
  ...                               libunwind: [ OFF ]
  ...

All other feature messages indicate '[ on ]'.

It's on a fairly standard x86-64 Ubuntu 24.10 installation, with 
various development libraries installed. Let me know if you need
any debug output or other information!

Thanks,

	Ingo