Re: [PATCH v2 11/16] perf parse-events: Improve error message for bad numbers

From: "Liang, Kan" <kan.liang@linux.intel.com>
To: Ian Rogers <irogers@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>,
	Arnaldo Carvalho de Melo <acme@kernel.org>,
	Namhyung Kim <namhyung@kernel.org>,
	Mark Rutland <mark.rutland@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Jiri Olsa <jolsa@kernel.org>,
	Adrian Hunter <adrian.hunter@intel.com>,
	James Clark <james.clark@arm.com>,
	linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org,
	bpf@vger.kernel.org, Atish Patra <atishp@rivosinc.com>,
	linux-riscv@lists.infradead.org,
	Beeman Strong <beeman@rivosinc.com>
Subject: Re: [PATCH v2 11/16] perf parse-events: Improve error message for bad numbers
Date: Fri, 19 Apr 2024 09:29:29 -0400	[thread overview]
Message-ID: <7a576651-6780-41a5-ac69-46ce299367b5@linux.intel.com> (raw)
In-Reply-To: <CAP-5=fXkn-nFTqGEqBYt6NUvoXU7OyLJeSCnWdD3taLHyK-xtQ@mail.gmail.com>

On 2024-04-18 5:07 p.m., Ian Rogers wrote:
> On Thu, Apr 18, 2024 at 1:27 PM Liang, Kan <kan.liang@linux.intel.com> wrote:
>>
>>
>>
>> On 2024-04-16 2:15 a.m., Ian Rogers wrote:
>>> Use the error handler from the parse_state to give a more informative
>>> error message.
>>>
>>> Before:
>>> ```
>>> $ perf stat -e 'cycles/period=99999999999999999999/' true
>>> event syntax error: 'cycles/period=99999999999999999999/'
>>>                                   \___ parser error
>>> Run 'perf list' for a list of valid events
>>>
>>>  Usage: perf stat [<options>] [<command>]
>>>
>>>     -e, --event <event>   event selector. use 'perf list' to list available events
>>> ```
>>>
>>> After:
>>> ```
>>> $ perf stat -e 'cycles/period=99999999999999999999/' true
>>> event syntax error: 'cycles/period=99999999999999999999/'
>>>                                   \___ parser error
>>>
>>> event syntax error: '..les/period=99999999999999999999/'
>>>                                   \___ Bad base 10 number "99999999999999999999"
>>
>>
>> It seems the patch only works for decimal?
>>
>> ./perf stat -e 'cycles/period=0xaaaaaaaaaaaaaaaaaaaaaa/' true
>> event syntax error: '..les/period=0xaaaaaaaaaaaaaaaaaaaaaa/'
>>                                    \___ parser error
>>  Run 'perf list' for a list of valid events
>>
>>   Usage: perf stat [<options>] [<command>]
>>
>>      -e, --event <event>   event selector. use 'perf list' to list
>> available events
>>
>> Thanks,
>> Kan
> 
> Right, for hexadecimal we say the number of digits is at most 16, so
> when you exceed this the token is no longer recognized. It just
> becomes input that can't be parsed, hence parser error. Doing this
> means we can simplify other strtoull checks, but I agree having a
> better error message for hexadecimal would be good. Let's do it as
> follow up.

OK. There is already a warning. It's fine to provide a follow-up for a
better error message later.

Thanks,
Kan

> 
> Thanks,
> Ian
> 
>>> Run 'perf list' for a list of valid events
>>>
>>>  Usage: perf stat [<options>] [<command>]
>>>
>>>     -e, --event <event>   event selector. use 'perf list' to list available events
>>> ```
>>>
>>> Signed-off-by: Ian Rogers <irogers@google.com>
>>> ---
>>>  tools/perf/util/parse-events.l | 40 ++++++++++++++++++++--------------
>>>  1 file changed, 24 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/tools/perf/util/parse-events.l b/tools/perf/util/parse-events.l
>>> index 6fe37003ab7b..0cd68c9f0d4f 100644
>>> --- a/tools/perf/util/parse-events.l
>>> +++ b/tools/perf/util/parse-events.l
>>> @@ -18,26 +18,34 @@
>>>
>>>  char *parse_events_get_text(yyscan_t yyscanner);
>>>  YYSTYPE *parse_events_get_lval(yyscan_t yyscanner);
>>> +int parse_events_get_column(yyscan_t yyscanner);
>>> +int parse_events_get_leng(yyscan_t yyscanner);
>>>
>>> -static int __value(YYSTYPE *yylval, char *str, int base, int token)
>>> +static int get_column(yyscan_t scanner)
>>>  {
>>> -     u64 num;
>>> -
>>> -     errno = 0;
>>> -     num = strtoull(str, NULL, base);
>>> -     if (errno)
>>> -             return PE_ERROR;
>>> -
>>> -     yylval->num = num;
>>> -     return token;
>>> +     return parse_events_get_column(scanner) - parse_events_get_leng(scanner);
>>>  }
>>>
>>> -static int value(yyscan_t scanner, int base)
>>> +static int value(struct parse_events_state *parse_state, yyscan_t scanner, int base)
>>>  {
>>>       YYSTYPE *yylval = parse_events_get_lval(scanner);
>>>       char *text = parse_events_get_text(scanner);
>>> +     u64 num;
>>>
>>> -     return __value(yylval, text, base, PE_VALUE);
>>> +     errno = 0;
>>> +     num = strtoull(text, NULL, base);
>>> +     if (errno) {
>>> +             struct parse_events_error *error = parse_state->error;
>>> +             char *help = NULL;
>>> +
>>> +             if (asprintf(&help, "Bad base %d number \"%s\"", base, text) > 0)
>>> +                     parse_events_error__handle(error, get_column(scanner), help , NULL);
>>> +
>>> +             return PE_ERROR;
>>> +     }
>>> +
>>> +     yylval->num = num;
>>> +     return PE_VALUE;
>>>  }
>>>
>>>  static int str(yyscan_t scanner, int token)
>>> @@ -283,8 +291,8 @@ r0x{num_raw_hex}  { return str(yyscanner, PE_RAW); }
>>>        */
>>>  "/"/{digit}          { return PE_BP_SLASH; }
>>>  "/"/{non_digit}              { BEGIN(config); return '/'; }
>>> -{num_dec}            { return value(yyscanner, 10); }
>>> -{num_hex}            { return value(yyscanner, 16); }
>>> +{num_dec}            { return value(_parse_state, yyscanner, 10); }
>>> +{num_hex}            { return value(_parse_state, yyscanner, 16); }
>>>       /*
>>>        * We need to separate 'mem:' scanner part, in order to get specific
>>>        * modifier bits parsed out. Otherwise we would need to handle PE_NAME
>>> @@ -330,8 +338,8 @@ cgroup-switches                                   { return sym(yyscanner, PERF_COUNT_SW_CGROUP_SWITCHES); }
>>>  {lc_type}-{lc_op_result}-{lc_op_result}      { return str(yyscanner, PE_LEGACY_CACHE); }
>>>  mem:                 { BEGIN(mem); return PE_PREFIX_MEM; }
>>>  r{num_raw_hex}               { return str(yyscanner, PE_RAW); }
>>> -{num_dec}            { return value(yyscanner, 10); }
>>> -{num_hex}            { return value(yyscanner, 16); }
>>> +{num_dec}            { return value(_parse_state, yyscanner, 10); }
>>> +{num_hex}            { return value(_parse_state, yyscanner, 16); }
>>>
>>>  {modifier_event}     { return str(yyscanner, PE_MODIFIER_EVENT); }
>>>  {name}                       { return str(yyscanner, PE_NAME); }
> 