Re: [PATCH 2/2] perf tools: Fix hybrid config terms list corruption

[Adrian Hunter]

On 10/09/21 10:32 pm, Jiri Olsa wrote:
> On Thu, Sep 09, 2021 at 03:55:08PM +0300, Adrian Hunter wrote:
>> A config terms list was spliced twice, resulting in a never-ending loop
>> when the list was traversed. Fix by using list_splice_init() and copying
>> and freeing the lists as necessary.
>>
>> This patch also depends on patch "perf tools: Factor out
>> copy_config_terms() and free_config_terms()"
>>
>> Example on ADL:
>>
>>  Before:
>>
>>  # perf record -e '{intel_pt//,cycles/aux-sample-size=4096/pp}' uname &
>>  # jobs
>>  [1]+  Running                    perf record -e "{intel_pt//,cycles/aux-sample-size=4096/pp}" uname
>>  # perf top -E 10
>>    PerfTop:    4071 irqs/sec  kernel: 6.9%  exact: 100.0% lost: 0/0 drop: 0/0 [4000Hz cycles],  (all, 24 CPUs)
>>  ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
>>
>>     97.60%  perf           [.] __evsel__get_config_term
>>      0.25%  [kernel]       [k] kallsyms_expand_symbol.constprop.13
>>      0.24%  perf           [.] kallsyms__parse
>>      0.15%  [kernel]       [k] _raw_spin_lock
>>      0.14%  [kernel]       [k] number
>>      0.13%  [kernel]       [k] advance_transaction
>>      0.08%  [kernel]       [k] format_decode
>>      0.08%  perf           [.] map__process_kallsym_symbol
>>      0.08%  perf           [.] rb_insert_color
>>      0.08%  [kernel]       [k] vsnprintf
>>  exiting.
>>  # kill %1
>>
>> After:
>>
>>  # perf record -e '{intel_pt//,cycles/aux-sample-size=4096/pp}' uname &
>>  Linux
>>  [ perf record: Woken up 1 times to write data ]
>>  [ perf record: Captured and wrote 0.060 MB perf.data ]
>>  # perf script | head
>>        perf-exec   604 [001]  1827.312293:                            psb:  psb offs: 0                       ffffffffb8415e87 pt_config_start+0x37 ([kernel.kallsyms])
>>        perf-exec   604  1827.312293:          1                       branches:  ffffffffb856a3bd event_sched_in.isra.133+0xfd ([kernel.kallsyms]) => ffffffffb856a9a0 perf_pmu_nop_void+0x0 ([kernel.kallsyms])
>>        perf-exec   604  1827.312293:          1                       branches:  ffffffffb856b10e merge_sched_in+0x26e ([kernel.kallsyms]) => ffffffffb856a2c0 event_sched_in.isra.133+0x0 ([kernel.kallsyms])
>>        perf-exec   604  1827.312293:          1                       branches:  ffffffffb856a45d event_sched_in.isra.133+0x19d ([kernel.kallsyms]) => ffffffffb8568b80 perf_event_set_state.part.61+0x0 ([kernel.kallsyms])
>>        perf-exec   604  1827.312293:          1                       branches:  ffffffffb8568b86 perf_event_set_state.part.61+0x6 ([kernel.kallsyms]) => ffffffffb85662a0 perf_event_update_time+0x0 ([kernel.kallsyms])
>>        perf-exec   604  1827.312293:          1                       branches:  ffffffffb856a35c event_sched_in.isra.133+0x9c ([kernel.kallsyms]) => ffffffffb8567610 perf_log_itrace_start+0x0 ([kernel.kallsyms])
>>        perf-exec   604  1827.312293:          1                       branches:  ffffffffb856a377 event_sched_in.isra.133+0xb7 ([kernel.kallsyms]) => ffffffffb8403b40 x86_pmu_add+0x0 ([kernel.kallsyms])
>>        perf-exec   604  1827.312293:          1                       branches:  ffffffffb8403b86 x86_pmu_add+0x46 ([kernel.kallsyms]) => ffffffffb8403940 collect_events+0x0 ([kernel.kallsyms])
>>        perf-exec   604  1827.312293:          1                       branches:  ffffffffb8403a7b collect_events+0x13b ([kernel.kallsyms]) => ffffffffb8402cd0 collect_event+0x0 ([kernel.kallsyms])
>>
>> Fixes: 94da591b1c7913 ("perf parse-events: Create two hybrid raw events")
>> Fixes: 9cbfa2f64c04d9 ("perf parse-events: Create two hybrid hardware events")
>> Fixes: 30def61f64bac5 ("perf parse-events: Create two hybrid cache events")
>> Signed-off-by: Adrian Hunter <adrian.hunter@xxxxxxxxx>
>> ---
>>  tools/perf/util/parse-events-hybrid.c | 18 +++++++++++++++---
>>  tools/perf/util/parse-events.c        | 18 ++++++++++++------
>>  2 files changed, 27 insertions(+), 9 deletions(-)
>>
>> diff --git a/tools/perf/util/parse-events-hybrid.c b/tools/perf/util/parse-events-hybrid.c
>> index 10160ab126f9..b234d95fb10a 100644
>> --- a/tools/perf/util/parse-events-hybrid.c
>> +++ b/tools/perf/util/parse-events-hybrid.c
>> @@ -76,12 +76,16 @@ static int add_hw_hybrid(struct parse_events_state *parse_state,
>>  	int ret;
>>  
>>  	perf_pmu__for_each_hybrid_pmu(pmu) {
>> +		LIST_HEAD(terms);
>> +
>>  		if (pmu_cmp(parse_state, pmu))
>>  			continue;
>>  
>> +		copy_config_terms(&terms, config_terms);
>>  		ret = create_event_hybrid(PERF_TYPE_HARDWARE,
>>  					  &parse_state->idx, list, attr, name,
>> -					  config_terms, pmu);
>> +					  &terms, pmu);
>> +		free_config_terms(&terms);
> 
> hm, why is this needed.. there's now list_splice_init &terms within
> create_event_hybrid call right? so there should be nothing nothing
> to clean

create_event_hybrid() can fail and not consume 'terms'.  By using
list_splice_init(), free_config_terms() will only free unconsumed terms.

> 
> same below

That also has the same reasoning.

> 
>>  		if (ret)
>>  			return ret;
>>  	}
>> @@ -115,11 +119,15 @@ static int add_raw_hybrid(struct parse_events_state *parse_state,
>>  	int ret;
>>  
>>  	perf_pmu__for_each_hybrid_pmu(pmu) {
>> +		LIST_HEAD(terms);
>> +
>>  		if (pmu_cmp(parse_state, pmu))
>>  			continue;
>>  
>> +		copy_config_terms(&terms, config_terms);
>>  		ret = create_raw_event_hybrid(&parse_state->idx, list, attr,
>> -					      name, config_terms, pmu);
>> +					      name, &terms, pmu);
>> +		free_config_terms(&terms);
>>  		if (ret)
>>  			return ret;
>>  	}
>> @@ -165,11 +173,15 @@ int parse_events__add_cache_hybrid(struct list_head *list, int *idx,
>>  
>>  	*hybrid = true;
>>  	perf_pmu__for_each_hybrid_pmu(pmu) {
>> +		LIST_HEAD(terms);
>> +
>>  		if (pmu_cmp(parse_state, pmu))
>>  			continue;
>>  
>> +		copy_config_terms(&terms, config_terms);
>>  		ret = create_event_hybrid(PERF_TYPE_HW_CACHE, idx, list,
>> -					  attr, name, config_terms, pmu);
>> +					  attr, name, &terms, pmu);
>> +		free_config_terms(&terms);
>>  		if (ret)
>>  			return ret;
>>  	}
>> diff --git a/tools/perf/util/parse-events.c b/tools/perf/util/parse-events.c
>> index ded5808798f9..51a2219df601 100644
>> --- a/tools/perf/util/parse-events.c
>> +++ b/tools/perf/util/parse-events.c
>> @@ -387,7 +387,7 @@ __add_event(struct list_head *list, int *idx,
>>  		evsel->name = strdup(name);
>>  
>>  	if (config_terms)
>> -		list_splice(config_terms, &evsel->config_terms);
>> +		list_splice_init(config_terms, &evsel->config_terms);
>>  
>>  	if (list)
>>  		list_add_tail(&evsel->core.node, list);
>> @@ -535,9 +535,12 @@ int parse_events_add_cache(struct list_head *list, int *idx,
>>  					     config_name ? : name, &config_terms,
>>  					     &hybrid, parse_state);
>>  	if (hybrid)
>> -		return ret;
>> +		goto out_free_terms;
>>  
>> -	return add_event(list, idx, &attr, config_name ? : name, &config_terms);
>> +	ret = add_event(list, idx, &attr, config_name ? : name, &config_terms);
>> +out_free_terms:
>> +	free_config_terms(&config_terms);
> 
> .. apart from this one and below, when coming from 'goto out_free_terms'
> we should call free_config_terms
> 
> jirka
> 
>> +	return ret;
>>  }
>>  
>>  static void tracepoint_error(struct parse_events_error *e, int err,
>> @@ -1457,10 +1460,13 @@ int parse_events_add_numeric(struct parse_events_state *parse_state,
>>  					       get_config_name(head_config),
>>  					       &config_terms, &hybrid);
>>  	if (hybrid)
>> -		return ret;
>> +		goto out_free_terms;
>>  
>> -	return add_event(list, &parse_state->idx, &attr,
>> -			 get_config_name(head_config), &config_terms);
>> +	ret = add_event(list, &parse_state->idx, &attr,
>> +			get_config_name(head_config), &config_terms);
>> +out_free_terms:
>> +	free_config_terms(&config_terms);
>> +	return ret;
>>  }
>>  
>>  int parse_events_add_tool(struct parse_events_state *parse_state,
>> -- 
>> 2.17.1
>>
>