linux-kernel - Re: [PATCH] perf jevents: Handle deleted JSONS in out of source builds

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAP-5=fVxMcMt=red5+D9_m4+wrUdPGkNP0irNqr5PU1UPJSO6A@mail.gmail.com>
Date: Tue, 20 Jan 2026 10:01:52 -0800
From: Ian Rogers <irogers@...gle.com>
To: James Clark <james.clark@...aro.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Arnaldo Carvalho de Melo <acme@...nel.org>, Namhyung Kim <namhyung@...nel.org>, 
	Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, linux-perf-users@...r.kernel.org, 
	linux-kernel@...r.kernel.org, Mark Brown <broonie@...nel.org>
Subject: Re: [PATCH] perf jevents: Handle deleted JSONS in out of source builds

On Tue, Jan 20, 2026 at 7:39 AM James Clark <james.clark@...aro.org> wrote:
>
> The cp command here doesn't remove files that have been removed from the
> sourcetree. That means incremental builds can either succeed with stale
> events or will fail completely if a stale json file has a broken
> reference in it.
>
> Fix it by using rsync instead of cp. legacy-cache.json has to be
> excluded as this is a generated file isn't present in the source tree.
>
> This only happens when deleting a JSON file, which has only happened
> once since the linked commit. The fixes commit is marked as the origin
> of the problem in case any future changes that delete JSONs are back
> ported, rather than the first commit that deleted a JSON file.
>
> Reported-by: Mark Brown <broonie@...nel.org>
> Closes: https://lore.kernel.org/linux-next/aW5XSAo88_LBPSYI@sirena.org.uk/
> Fixes: 4bb55de4ff03 ("perf jevents: Support copying the source json files to OUTPUT")
> Signed-off-by: James Clark <james.clark@...aro.org>
> ---
> This is a bit of a hack and I thought that making jevents.py handle
> multiple input folders would be a much better solution than this. Then
> we could have "gen-pmu-events" for only generated files and "pmu-events"
> for only in-tree input files. It would be very clear what's generated
> and what's not and all copying rules and special clean rules just
> disappear (and this isn't the first time these rules have caused build
> issues).
>
> Unfortunately, after a while of trying to modify the script I thought it
> was too invasive for now. The script does output per-file at the very
> bottom of the logic in process_one_file(), so adding files in another
> folder ends up re-emitting section headers when another chunk is output.
> Although other parts of the script do build things up in memory before
> outputting so it was possible to make those parts work with multiple
> folders transparently.

Thanks James!
Acked-by: Ian Rogers <irogers@...gle.com>
I see other rsync uses in:
tools/testing/selftests/sparc64/Makefile
tools/testing/selftests/bpf/Makefile
but they aren't the most compelling mainstream uses. I wonder whether
we can test for rsync's availability and if not fall back on cp?

Thanks,
Ian

> ---
>  tools/perf/pmu-events/Build | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/tools/perf/pmu-events/Build b/tools/perf/pmu-events/Build
> index a46ab7b612df..079d04c4f7d8 100644
> --- a/tools/perf/pmu-events/Build
> +++ b/tools/perf/pmu-events/Build
> @@ -12,13 +12,16 @@ METRIC_TEST_LOG     =  $(OUTPUT)pmu-events/metric_test.log
>  TEST_EMPTY_PMU_EVENTS_C = $(OUTPUT)pmu-events/test-empty-pmu-events.c
>  EMPTY_PMU_EVENTS_TEST_LOG = $(OUTPUT)pmu-events/empty-pmu-events.log
>  LEGACY_CACHE_PY        =  pmu-events/make_legacy_cache.py
> -LEGACY_CACHE_JSON = $(OUTPUT)pmu-events/arch/common/common/legacy-cache.json
> +LEGACY_CACHE_SYNC_PATH = arch/common/common/legacy-cache.json
> +LEGACY_CACHE_JSON = $(OUTPUT)pmu-events/$(LEGACY_CACHE_SYNC_PATH)
>
>  ifeq ($(JEVENTS_ARCH),)
>  JEVENTS_ARCH=$(SRCARCH)
>  endif
>  JEVENTS_MODEL ?= all
>
> +GEN_JSON = $(patsubst %,$(OUTPUT)%,$(JSON)) $(LEGACY_CACHE_JSON)
> +
>  #
>  # Locate/process JSON files in pmu-events/arch/
>  # directory and create tables in pmu-events.c.
> @@ -31,17 +34,20 @@ $(PMU_EVENTS_C): $(EMPTY_PMU_EVENTS_C)
>  else
>  # Copy checked-in json to OUTPUT for generation if it's an out of source build
>  ifneq ($(OUTPUT),)
> -$(OUTPUT)pmu-events/arch/%: pmu-events/arch/%
> +SYNC_PMU_EVENTS := $(OUTPUT)pmu-events/.synced
> +$(SYNC_PMU_EVENTS): $(JSON)
>         $(call rule_mkdir)
> -       $(Q)$(call echo-cmd,gen)cp $< $@
> +       $(Q)$(call echo-cmd,gen)rsync -a --delete --exclude=$(LEGACY_CACHE_SYNC_PATH) \
> +               --include="*.json" --include="*.csv" pmu-events/arch $(OUTPUT)pmu-events/
> +       $(Q)touch $@
> +
> +$(GEN_JSON): $(SYNC_PMU_EVENTS)
>  endif
>
>  $(LEGACY_CACHE_JSON): $(LEGACY_CACHE_PY)
>         $(call rule_mkdir)
>         $(Q)$(call echo-cmd,gen)$(PYTHON) $(LEGACY_CACHE_PY) > $@
>
> -GEN_JSON = $(patsubst %,$(OUTPUT)%,$(JSON)) $(LEGACY_CACHE_JSON)
> -
>  $(METRIC_TEST_LOG): $(METRIC_TEST_PY) $(METRIC_PY)
>         $(call rule_mkdir)
>         $(Q)$(call echo-cmd,test)$(PYTHON) $< 2> $@ || (cat $@ && false)
>
> ---
> base-commit: 571d29baa07e83e637075239f379f91353c24ec9
> change-id: 20260120-james-perf-json-delete-fix-71553b379e8e
>
> Best regards,
> --
> James Clark <james.clark@...aro.org>
>