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Fri, 12 Dec 2025 06:43:59 -0800 (PST) Message-ID: <99e9614d-a956-40dc-a86b-a4c5aea0fe8a@linaro.org> Date: Fri, 12 Dec 2025 16:43:57 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 01/12] perf parse-events: Refactor get_config_terms() to remove macros To: Ian Rogers Cc: Linux perf Profiling , linux-kernel@vger.kernel.org, coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Namhyung Kim , Mark Rutland , Alexander Shishkin , Jiri Olsa , Adrian Hunter , Suzuki K Poulose , Mike Leach , John Garry , Will Deacon , Leo Yan , leo.yan@arm.com References: <20251208-james-perf-config-bits-v2-0-4ac0281993b0@linaro.org> <20251208-james-perf-config-bits-v2-1-4ac0281993b0@linaro.org> <6ba6bde3-f56b-4354-b336-4739cb1edb71@linaro.org> Content-Language: en-US From: James Clark In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 09/12/2025 20:09, Ian Rogers wrote: > On Tue, Dec 9, 2025 at 9:55 AM James Clark wrote: >> >> On 09/12/2025 15:58, Ian Rogers wrote: >>> On Tue, Dec 9, 2025 at 4:48 AM James Clark wrote: >>>> >>>> On 08/12/2025 2:22 pm, James Clark wrote: >>>>> The ADD_CONFIG_TERM() macros build the __type argument out of a partial >>>>> EVSEL__CONFIG_TERM_x enum name. This means that they can't be called >>>>> from a function where __type is a variable and it's also impossible to >>>>> grep the codebase to find usages of these enums as they're never typed >>>>> in full. >>>>> >>>>> Fix this by removing the macros and replacing them with an >>>>> add_config_term() function. It seems the main reason these existed in >>>>> the first place was to avoid type punning and to write to a specific >>>>> field in the union, but the same thing can be achieved with a single >>>>> write to a u64 'val' field. >>>>> >>>>> Signed-off-by: James Clark >>>>> --- >>>>> tools/perf/util/evsel_config.h | 1 + >>>>> tools/perf/util/parse-events.c | 146 ++++++++++++++++++++++++----------------- >>>>> 2 files changed, 86 insertions(+), 61 deletions(-) >>>>> >>>>> diff --git a/tools/perf/util/evsel_config.h b/tools/perf/util/evsel_config.h >>>>> index bcd3a978f0c4..685fd8d5c4a8 100644 >>>>> --- a/tools/perf/util/evsel_config.h >>>>> +++ b/tools/perf/util/evsel_config.h >>>>> @@ -50,6 +50,7 @@ struct evsel_config_term { >>>>> u64 cfg_chg; >>>>> char *str; >>>>> int cpu; >>>>> + u64 val; >>>>> } val; >>>>> bool weak; >>>>> }; >>>>> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c >>>>> index 17c1c36a7bf9..d5b009b4ebab 100644 >>>>> --- a/tools/perf/util/parse-events.c >>>>> +++ b/tools/perf/util/parse-events.c >>>>> @@ -1116,105 +1116,107 @@ static int config_attr(struct perf_event_attr *attr, >>>>> return 0; >>>>> } >>>>> >>>>> -static int get_config_terms(const struct parse_events_terms *head_config, >>>>> - struct list_head *head_terms) >>>>> +static struct evsel_config_term *add_config_term(enum evsel_term_type type, >>>>> + struct list_head *head_terms, >>>>> + bool weak) >>>>> { >>>>> -#define ADD_CONFIG_TERM(__type, __weak) \ >>>>> - struct evsel_config_term *__t; \ >>>>> - \ >>>>> - __t = zalloc(sizeof(*__t)); \ >>>>> - if (!__t) \ >>>>> - return -ENOMEM; \ >>>>> - \ >>>>> - INIT_LIST_HEAD(&__t->list); \ >>>>> - __t->type = EVSEL__CONFIG_TERM_ ## __type; \ >>>>> - __t->weak = __weak; \ >>>>> - list_add_tail(&__t->list, head_terms) >>>>> - >>>>> -#define ADD_CONFIG_TERM_VAL(__type, __name, __val, __weak) \ >>>>> -do { \ >>>>> - ADD_CONFIG_TERM(__type, __weak); \ >>>>> - __t->val.__name = __val; \ >>>>> -} while (0) >>>>> + struct evsel_config_term *t; >>>>> >>>>> -#define ADD_CONFIG_TERM_STR(__type, __val, __weak) \ >>>>> -do { \ >>>>> - ADD_CONFIG_TERM(__type, __weak); \ >>>>> - __t->val.str = strdup(__val); \ >>>>> - if (!__t->val.str) { \ >>>>> - zfree(&__t); \ >>>>> - return -ENOMEM; \ >>>>> - } \ >>>>> - __t->free_str = true; \ >>>>> -} while (0) >>>>> + t = zalloc(sizeof(*t)); >>>>> + if (!t) >>>>> + return NULL; >>>>> + >>>>> + INIT_LIST_HEAD(&t->list); >>>>> + t->type = type; >>>>> + t->weak = weak; >>>>> + list_add_tail(&t->list, head_terms); >>>>> >>>>> + return t; >>>>> +} >>>>> + >>>>> +static int get_config_terms(const struct parse_events_terms *head_config, >>>>> + struct list_head *head_terms) >>>>> +{ >>>>> struct parse_events_term *term; >>>>> >>>>> list_for_each_entry(term, &head_config->terms, list) { >>>>> + struct evsel_config_term *new_term; >>>>> + enum evsel_term_type new_type; >>>>> + char *str = NULL; >>>>> + u64 val; >>>>> + >>>>> switch (term->type_term) { >>>>> case PARSE_EVENTS__TERM_TYPE_SAMPLE_PERIOD: >>>>> - ADD_CONFIG_TERM_VAL(PERIOD, period, term->val.num, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_PERIOD; >>>>> + val = term->val.num; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_SAMPLE_FREQ: >>>>> - ADD_CONFIG_TERM_VAL(FREQ, freq, term->val.num, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_FREQ; >>>>> + val = term->val.num; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_TIME: >>>>> - ADD_CONFIG_TERM_VAL(TIME, time, term->val.num, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_TIME; >>>>> + val = term->val.num; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_CALLGRAPH: >>>>> - ADD_CONFIG_TERM_STR(CALLGRAPH, term->val.str, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_CALLGRAPH; >>>>> + str = term->val.str; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_BRANCH_SAMPLE_TYPE: >>>>> - ADD_CONFIG_TERM_STR(BRANCH, term->val.str, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_BRANCH; >>>>> + str = term->val.str; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_STACKSIZE: >>>>> - ADD_CONFIG_TERM_VAL(STACK_USER, stack_user, >>>>> - term->val.num, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_STACK_USER; >>>>> + val = term->val.num; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_INHERIT: >>>>> - ADD_CONFIG_TERM_VAL(INHERIT, inherit, >>>>> - term->val.num ? 1 : 0, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_INHERIT; >>>>> + val = term->val.num ? 1 : 0; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_NOINHERIT: >>>>> - ADD_CONFIG_TERM_VAL(INHERIT, inherit, >>>>> - term->val.num ? 0 : 1, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_INHERIT; >>>>> + val = term->val.num ? 0 : 1; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_MAX_STACK: >>>>> - ADD_CONFIG_TERM_VAL(MAX_STACK, max_stack, >>>>> - term->val.num, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_MAX_STACK; >>>>> + val = term->val.num; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_MAX_EVENTS: >>>>> - ADD_CONFIG_TERM_VAL(MAX_EVENTS, max_events, >>>>> - term->val.num, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_MAX_EVENTS; >>>>> + val = term->val.num; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_OVERWRITE: >>>>> - ADD_CONFIG_TERM_VAL(OVERWRITE, overwrite, >>>>> - term->val.num ? 1 : 0, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_OVERWRITE; >>>>> + val = term->val.num ? 1 : 0; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_NOOVERWRITE: >>>>> - ADD_CONFIG_TERM_VAL(OVERWRITE, overwrite, >>>>> - term->val.num ? 0 : 1, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_OVERWRITE; >>>>> + val = term->val.num ? 0 : 1; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_DRV_CFG: >>>>> - ADD_CONFIG_TERM_STR(DRV_CFG, term->val.str, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_DRV_CFG; >>>>> + str = term->val.str; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_PERCORE: >>>>> - ADD_CONFIG_TERM_VAL(PERCORE, percore, >>>>> - term->val.num ? true : false, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_PERCORE; >>>>> + val = term->val.num ? true : false; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_AUX_OUTPUT: >>>>> - ADD_CONFIG_TERM_VAL(AUX_OUTPUT, aux_output, >>>>> - term->val.num ? 1 : 0, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_AUX_OUTPUT; >>>>> + val = term->val.num ? 1 : 0; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_AUX_ACTION: >>>>> - ADD_CONFIG_TERM_STR(AUX_ACTION, term->val.str, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_AUX_ACTION; >>>>> + str = term->val.str; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_AUX_SAMPLE_SIZE: >>>>> - ADD_CONFIG_TERM_VAL(AUX_SAMPLE_SIZE, aux_sample_size, >>>>> - term->val.num, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_AUX_SAMPLE_SIZE; >>>>> + val = term->val.num; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_RATIO_TO_PREV: >>>>> - ADD_CONFIG_TERM_STR(RATIO_TO_PREV, term->val.str, term->weak); >>>>> + new_type = EVSEL__CONFIG_TERM_RATIO_TO_PREV; >>>>> + str = term->val.str; >>>>> break; >>>>> case PARSE_EVENTS__TERM_TYPE_USER: >>>>> case PARSE_EVENTS__TERM_TYPE_CONFIG: >>>>> @@ -1229,7 +1231,23 @@ do { \ >>>>> case PARSE_EVENTS__TERM_TYPE_RAW: >>>>> case PARSE_EVENTS__TERM_TYPE_CPU: >>>>> default: >>>>> - break; >>>>> + /* Don't add a new term for these ones */ >>>>> + continue; >>>>> + } >>>>> + >>>>> + new_term = add_config_term(new_type, head_terms, term->weak); >>>>> + if (!new_term) >>>>> + return -ENOMEM; >>>>> + >>>>> + if (str) { >>>>> + new_term->val.str = strdup(str); >>>>> + if (!new_term->val.str) { >>>>> + zfree(&new_term); >>>>> + return -ENOMEM; >>>>> + } >>>>> + new_term->free_str = true; >>>>> + } else { >>>> >>>> This will incorrectly hit the else if term->val.str is NULL. Not sure if >>>> that can happen but will fix anyway. >>>> >>>>> + new_term->val.val = val; >>>> >>>> There's an uninitialized variable warning for val here on release >>>> builds. Will fix too >>> >>> I'm not sure how I feel about the change, but did you check that it is >>> ubsan clean? I worry it is introducing writes to "val" and then reads >>> from say "period" in the evsel_config_term val union. I believe ubsan >>> will flag this as: >>> https://en.cppreference.com/w/cpp/language/union.html >>> "It is undefined behavior to read from the member of the union that >>> wasn't most recently written." >>> >>> Thanks, >>> Ian >>> >> >> Maybe for C++, but not for C [1]: >> >> Accessing my_union.i after most recently writing to the other member, >> my_union.d, is an allowed form of type-punning in C, provided that the >> member read is not larger than the one whose value was set >> >> Type punning with unions is widely used in the kernel and there are a >> couple of instances in Perf. There are tons of discussions about it on >> the mailing lists too. I can check it with ubsan though. > > Thanks. I'm mostly worried about ubsan being clean. One of those > mailing list discussions, or sadly outside the usual trolls lack of > discussion, is my trying to remove a prevalent source of type punning: > https://lore.kernel.org/lkml/20251016205126.2882625-1-irogers@google.com/ > > Ian > No ubsan issues on any Perf tests from this, but I did forget a free in the new test that I saw with asan so I'll send a new version. >> [1]: https://en.wikipedia.org/wiki/Type_punning#C_and_C++ >> >>>>> } >>>>> } >>>>> return 0; >>>>> @@ -1290,10 +1308,16 @@ static int get_config_chgs(struct perf_pmu *pmu, struct parse_events_terms *head >>>>> } >>>>> } >>>>> >>>>> - if (bits) >>>>> - ADD_CONFIG_TERM_VAL(CFG_CHG, cfg_chg, bits, false); >>>>> + if (bits) { >>>>> + struct evsel_config_term *new_term; >>>>> + >>>>> + new_term = add_config_term(EVSEL__CONFIG_TERM_CFG_CHG, >>>>> + head_terms, false); >>>>> + if (!new_term) >>>>> + return -ENOMEM; >>>>> + new_term->val.cfg_chg = bits; >>>>> + } >>>>> >>>>> -#undef ADD_CONFIG_TERM >>>>> return 0; >>>>> } >>>>> >>>>> >>>> >>