Re: [PATCH 1/1 next] tools build: Remove the libunwind feature tests from the ones detected when test-all.o builds

[Quentin Monnet <qmo@kernel.org>]

2025-03-17 10:16 UTC-0700 ~ Ian Rogers <irogers@google.com>
> On Mon, Mar 17, 2025 at 10:06 AM Namhyung Kim <namhyung@kernel.org> wrote:
>>
>> Hello,
>>
>> On Mon, Mar 17, 2025 at 09:10:29AM -0700, Ian Rogers wrote:
>>> On Wed, Dec 11, 2024 at 7:45 AM Arnaldo Carvalho de Melo
>>> <acme@kernel.org> wrote:
>>>>
>>>> We have a tools/build/feature/test-all.c that has the most common set of
>>>> features that perf uses and are expected to have its development files
>>>> available when building perf.
>>>>
>>>> When we made libwunwind opt-in we forgot to remove them from the list of
>>>> features that are assumed to be available when test-all.c builds, remove
>>>> them.
>>>>
>>>> Before this patch:
>>>>
>>>>   $ rm -rf /tmp/b ; mkdir /tmp/b ; make -C tools/perf O=/tmp/b feature-dump ; grep feature-libunwind-aarch64= /tmp/b/FEATURE-DUMP
>>>>   feature-libunwind-aarch64=1
>>>>   $
>>>>
>>>> Even tho this not being test built and those header files being
>>>> available:
>>>>
>>>>   $ head -5 tools/build/feature/test-libunwind-aarch64.c
>>>>   // SPDX-License-Identifier: GPL-2.0
>>>>   #include <libunwind-aarch64.h>
>>>>   #include <stdlib.h>
>>>>
>>>>   extern int UNW_OBJ(dwarf_search_unwind_table) (unw_addr_space_t as,
>>>>   $
>>>>
>>>> After this patch:
>>>>
>>>>   $ grep feature-libunwind- /tmp/b/FEATURE-DUMP
>>>>   $
>>>>
>>>> Now an audit on what is being enabled when test-all.c builds will be
>>>> performed.
>>>>
>>>> Fixes: 176c9d1e6a06f2fa ("tools features: Don't check for libunwind devel files by default")
>>>> Cc: Adrian Hunter <adrian.hunter@intel.com>
>>>> Cc: Ian Rogers <irogers@google.com>
>>>> Cc: James Clark <james.clark@linaro.org>
>>>> Cc: Jiri Olsa <jolsa@kernel.org>
>>>> Cc: Kan Liang <kan.liang@linux.intel.com>
>>>> Cc: Namhyung Kim <namhyung@kernel.org>
>>>> Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
>>>
>>> Sorry for the delay on this.
>>>
>>> Reviewed-by: Ian Rogers <irogers@google.com>
>>
>> Thanks for the review, but I think this part is used by other tools like
>> BPF and tracing.  It'd be nice to get reviews from them.
> 
> Sgtm. The patch hasn't had attention for 3 months. A quick grep for
> "unwind" and "UNW_" shows only use in perf and the feature tests.
> 
> Thanks,
> Ian


Indeed, bpftool does not rely on libunwind, and I don't remember other
BPF components doing so, either.

Quentin