Commit 72a8b9c0 authored by Thomas Richter's avatar Thomas Richter Committed by Arnaldo Carvalho de Melo
Browse files

perf parse-events: Fix big-endian 'overwrite' by writing correct union member 



The "Read backward ring buffer" test crashes on big-endian (e.g. s390x)
due to a NULL dereference when the backward mmap path isn't enabled.

Reproducer:
  # ./perf test -F 'Read backward ring buffer'
  Segmentation fault (core dumped)
  # uname -m
  s390x
  #

Root cause:
get_config_terms() stores into evsel_config_term::val.val (u64) while later
code reads boolean fields such as evsel_config_term::val.overwrite.
On big-endian the 1-byte boolean is left-aligned, so writing
evsel_config_term::val.val = 1 is read back as
evsel_config_term::val.overwrite = 0,
leaving backward mmap disabled and a NULL map being used.

Store values in the union member that matches the term type, e.g.:
  /* for OVERWRITE */
  new_term->val.overwrite = 1;  /* not new_term->val.val = 1 */
to fix this. Improve add_config_term() and add two more parameters for
string and value. Function add_config_term() now creates a complete node
element of type evsel_config_term and handles all evsel_config_term::val
union members.

Impact:
Enables backward mmap on big-endian and prevents the crash.
No change on little-endian.

Output after:
 # ./perf test -Fv 44
 --- start ---
 Using CPUID IBM,9175,705,ME1,3.8,002f
 mmap size 1052672B
 mmap size 8192B
 ---- end ----
 44: Read backward ring buffer                         : Ok
 #

Fixes: 159ca97c ("perf parse-events: Refactor get_config_terms() to remove macros")
Reviewed-by: default avatarJames Clark <james.clark@linaro.org>
Reviewed-by: default avatarJan Polensky <japo@linux.ibm.com>
Signed-off-by: default avatarThomas Richter <tmricht@linux.ibm.com>
Acked-by: default avatarIan Rogers <irogers@google.com>
Cc: James Clark <james.clark@linaro.org>
Signed-off-by: default avatarNamhyung Kim <namhyung@kernel.org>
Signed-off-by: default avatarArnaldo Carvalho de Melo <acme@redhat.com>
parent 8dd1d9a3

tools/perf/util/parse-events.c

+65 −17
Original line number Diff line number Diff line
@@ -1117,7 +1117,7 @@ static int config_attr(struct perf_event_attr *attr, 


static struct evsel_config_term *add_config_term(enum evsel_term_type type,

						 struct list_head *head_terms,

						 bool weak)

						 bool weak, char *str, u64 val)

{

	struct evsel_config_term *t;
@@ -1128,8 +1128,62 @@ static struct evsel_config_term *add_config_term(enum evsel_term_type type, 
	INIT_LIST_HEAD(&t->list);

	t->type = type;

	t->weak	= weak;

	list_add_tail(&t->list, head_terms);



	switch (type) {

	case EVSEL__CONFIG_TERM_PERIOD:

	case EVSEL__CONFIG_TERM_FREQ:

	case EVSEL__CONFIG_TERM_STACK_USER:

	case EVSEL__CONFIG_TERM_USR_CHG_CONFIG:

	case EVSEL__CONFIG_TERM_USR_CHG_CONFIG1:

	case EVSEL__CONFIG_TERM_USR_CHG_CONFIG2:

	case EVSEL__CONFIG_TERM_USR_CHG_CONFIG3:

	case EVSEL__CONFIG_TERM_USR_CHG_CONFIG4:

		t->val.val = val;

		break;

	case EVSEL__CONFIG_TERM_TIME:

		t->val.time = val;

		break;

	case EVSEL__CONFIG_TERM_INHERIT:

		t->val.inherit = val;

		break;

	case EVSEL__CONFIG_TERM_OVERWRITE:

		t->val.overwrite = val;

		break;

	case EVSEL__CONFIG_TERM_MAX_STACK:

		t->val.max_stack = val;

		break;

	case EVSEL__CONFIG_TERM_MAX_EVENTS:

		t->val.max_events = val;

		break;

	case EVSEL__CONFIG_TERM_PERCORE:

		t->val.percore = val;

		break;

	case EVSEL__CONFIG_TERM_AUX_OUTPUT:

		t->val.aux_output = val;

		break;

	case EVSEL__CONFIG_TERM_AUX_SAMPLE_SIZE:

		t->val.aux_sample_size = val;

		break;

	case EVSEL__CONFIG_TERM_CALLGRAPH:

	case EVSEL__CONFIG_TERM_BRANCH:

	case EVSEL__CONFIG_TERM_DRV_CFG:

	case EVSEL__CONFIG_TERM_RATIO_TO_PREV:

	case EVSEL__CONFIG_TERM_AUX_ACTION:

		if (str) {

			t->val.str = strdup(str);

			if (!t->val.str) {

				zfree(&t);

				return NULL;

			}

			t->free_str = true;

		}

		break;

	default:

		t->val.val = val;

		break;

	}



	list_add_tail(&t->list, head_terms);

	return t;

}
@@ -1142,7 +1196,7 @@ static int get_config_terms(const struct parse_events_terms *head_config, 
		struct evsel_config_term *new_term;

		enum evsel_term_type new_type;

		bool str_type = false;

		u64 val;

		u64 val = 0;



		switch (term->type_term) {

		case PARSE_EVENTS__TERM_TYPE_SAMPLE_PERIOD:
@@ -1234,20 +1288,15 @@ static int get_config_terms(const struct parse_events_terms *head_config, 
			continue;

		}



		new_term = add_config_term(new_type, head_terms, term->weak);

		/*

		 * Note: Members evsel_config_term::val and

		 * parse_events_term::val are unions and endianness needs

		 * to be taken into account when changing such union members.

		 */

		new_term = add_config_term(new_type, head_terms, term->weak,

					   str_type ? term->val.str : NULL, val);

		if (!new_term)

			return -ENOMEM;



		if (str_type) {

			new_term->val.str = strdup(term->val.str);

			if (!new_term->val.str) {

				zfree(&new_term);

				return -ENOMEM;

			}

			new_term->free_str = true;

		} else {

			new_term->val.val = val;

		}

	}

	return 0;

}
@@ -1277,10 +1326,9 @@ static int add_cfg_chg(const struct perf_pmu *pmu, 
	if (bits) {

		struct evsel_config_term *new_term;



		new_term = add_config_term(new_term_type, head_terms, false);

		new_term = add_config_term(new_term_type, head_terms, false, NULL, bits);

		if (!new_term)

			return -ENOMEM;

		new_term->val.cfg_chg = bits;

	}



	return 0;