linux-kernel - Re: [PATCH V7 6/8] perf/tools: Extend branch type classification

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Date:   Mon, 5 Sep 2022 13:30:25 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>
Cc:     linux-kernel@...r.kernel.org, linux-perf-users@...r.kernel.org,
        peterz@...radead.org, alexander.shishkin@...ux.intel.com,
        jolsa@...hat.com, mark.rutland@....com,
        Robin Murphy <robin.murphy@....com>,
        Suzuki Poulose <suzuki.poulose@....com>,
        James Clark <james.clark@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH V7 6/8] perf/tools: Extend branch type classification



On 9/2/22 23:16, Arnaldo Carvalho de Melo wrote:
> Em Fri, Sep 02, 2022 at 02:31:34PM -0300, Arnaldo Carvalho de Melo escreveu:
>> Em Thu, Sep 01, 2022 at 10:37:24AM +0530, Anshuman Khandual escreveu:
>>> On 8/31/22 02:41, Arnaldo Carvalho de Melo wrote:
>>>> Strange:
>>>>
>>>>   75     8.89 ubuntu:20.04-x-powerpc64el    : FAIL gcc version 10.3.0 (Ubuntu 10.3.0-1ubuntu1~20.04)
>>>>         inlined from 'branch_type_stat_display' at util/branch.c:152:4:
>>>>     /usr/powerpc64le-linux-gnu/include/bits/stdio2.h:100:10: error: '%8s' directive argument is null [-Werror=format-overflow=]
>>>>       100 |   return __fprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1, __fmt,
>>>>           |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>       101 |    __va_arg_pack ());
>>>>           |    ~~~~~~~~~~~~~~~~~
>>>>
>>>
>>> Indeed. But this new code block here looks exact same like the previous and existing one
>>> i.e with branch_new_name() and PERF_BR_NEW_MAX. The complain is that - '%8s' directive
>>> argument is NULL. This warning might just be a false positive [1], because of a compiler
>>> problem on powerpc64el ? But please do let me know if something needs to be changed here
>>> to avoid this warning.
>>>
>>> [1] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90036
>>>
>>
>> So, I tried not returning NULL in the functions that are ultimately
>> called, but that didn't help, so I'll try just disabling that specific
>> warning for this specific file.
> 
> Got it building:

Thanks Arnaldo, I guess all the tool changes in this series, along with this
build will land in linux-next later for more test coverage.

> 
>     23.68 ubuntu:20.04-x-powerpc64el    : Ok   powerpc64le-linux-gnu-gcc (Ubuntu 10.3.0-1ubuntu1~20.04) 10.3.0
> BUILD_TARBALL_HEAD=b0f700972d9d0c9b8e73f69ccf0e56d74c580d71
> 
> With:
> 
>>>From b0f700972d9d0c9b8e73f69ccf0e56d74c580d71 Mon Sep 17 00:00:00 2001
> From: Arnaldo Carvalho de Melo <acme@...hat.com>
> Date: Fri, 2 Sep 2022 14:35:26 -0300
> Subject: [PATCH 1/1] perf build: Avoid false positive with
>  -Werror=format-overflow= with gcc 10.3.0 on powerpc
> 
> When building with gcc 10.3.0 on powerpc this is happening:
> 
>    75     8.89 ubuntu:20.04-x-powerpc64el    : FAIL gcc version 10.3.0 (Ubuntu 10.3.0-1ubuntu1~20.04)
>          inlined from 'branch_type_stat_display' at util/branch.c:152:4:
>      /usr/powerpc64le-linux-gnu/include/bits/stdio2.h:100:10: error: '%8s' directive argument is null [-Werror=format-overflow=]
>        100 |   return __fprintf_chk (__stream, __USE_FORTIFY_LEVEL - 1, __fmt,
>            |          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>        101 |    __va_arg_pack ());
>            |    ~~~~~~~~~~~~~~~~~
> 
> Looks related to:
> 
>   [10/11/12/13 Regression] false positive: directive argument is null [-Werror=format-overflow=]
>   https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90036
> 
> So lets disable this just for the util/branch.o file.
> 
> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
> Cc: Anshuman Khandual <anshuman.khandual@....com>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: James Clark <james.clark@....com>
> Cc: Jiri Olsa <jolsa@...nel.org>
> Cc: Mark Rutland <mark.rutland@....com>
> Cc: Namhyung Kim <namhyung@...nel.org>
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Robin Murphy <robin.murphy@....com>
> Cc: Suzuki Poulouse <suzuki.poulose@....com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Will Deacon <will@...nel.org>
> Link: http://lore.kernel.org/lkml/YxI99uLvpgAZjm2r@kernel.org
> Signed-off-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> ---
>  tools/perf/util/Build | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/tools/perf/util/Build b/tools/perf/util/Build
> index 8fd6dc8de5210336..20a5524e88a04d44 100644
> --- a/tools/perf/util/Build
> +++ b/tools/perf/util/Build
> @@ -223,6 +223,10 @@ CFLAGS_llvm-utils.o += -DPERF_INCLUDE_DIR="BUILD_STR($(perf_include_dir_SQ))"
>  # avoid compiler warnings in 32-bit mode
>  CFLAGS_genelf_debug.o  += -Wno-packed
>  
> +# avoid false positive when building with gcc 10.3.0 on powerpc
> +# See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90036
> +CFLAGS_branch.o += -Wno-format-overflow
> +
>  $(OUTPUT)util/parse-events-flex.c $(OUTPUT)util/parse-events-flex.h: util/parse-events.l $(OUTPUT)util/parse-events-bison.c
>  	$(call rule_mkdir)
>  	$(Q)$(call echo-cmd,flex)$(FLEX) -o $(OUTPUT)util/parse-events-flex.c \