@@ -30,6 +30,10 @@
#endif
#ifdef USE_PCRE2
+static pthread_key_t match_data_key;
+static int match_data_key_uninitialized = 1;
+static __thread char match_data_initialized;
+
char const *regex_arch_string(void)
{
static char arch_string_buffer[32];
@@ -60,14 +64,6 @@ char const *regex_arch_string(void)
struct regex_data {
pcre2_code *regex; /* compiled regular expression */
-#ifndef AGGRESSIVE_FREE_AFTER_REGEX_MATCH
- /*
- * match data block required for the compiled
- * pattern in pcre2
- */
- pcre2_match_data *match_data;
-#endif
- pthread_mutex_t match_mutex;
};
int regex_prepare_data(struct regex_data **regex, char const *pattern_string,
@@ -86,13 +82,6 @@ int regex_prepare_data(struct regex_data **regex, char const *pattern_string,
goto err;
}
-#ifndef AGGRESSIVE_FREE_AFTER_REGEX_MATCH
- (*regex)->match_data =
- pcre2_match_data_create_from_pattern((*regex)->regex, NULL);
- if (!(*regex)->match_data) {
- goto err;
- }
-#endif
return 0;
err:
@@ -142,13 +131,6 @@ int regex_load_mmap(struct mmap_area *mmap_area, struct regex_data **regex,
if (rc != 1)
goto err;
-#ifndef AGGRESSIVE_FREE_AFTER_REGEX_MATCH
- (*regex)->match_data =
- pcre2_match_data_create_from_pattern((*regex)->regex, NULL);
- if (!(*regex)->match_data)
- goto err;
-#endif
-
*regex_compiled = true;
}
@@ -204,18 +186,16 @@ out:
return rc;
}
+static void match_data_thread_free(void *match_data)
+{
+ pcre2_match_data_free(match_data);
+}
+
void regex_data_free(struct regex_data *regex)
{
if (regex) {
if (regex->regex)
pcre2_code_free(regex->regex);
-
-#ifndef AGGRESSIVE_FREE_AFTER_REGEX_MATCH
- if (regex->match_data)
- pcre2_match_data_free(regex->match_data);
-#endif
-
- __pthread_mutex_destroy(®ex->match_mutex);
free(regex);
}
}
@@ -223,32 +203,30 @@ void regex_data_free(struct regex_data *regex)
int regex_match(struct regex_data *regex, char const *subject, int partial)
{
int rc;
+ bool slow;
pcre2_match_data *match_data;
- __pthread_mutex_lock(®ex->match_mutex);
-#ifdef AGGRESSIVE_FREE_AFTER_REGEX_MATCH
- match_data = pcre2_match_data_create_from_pattern(
- regex->regex, NULL);
- if (match_data == NULL) {
- __pthread_mutex_unlock(®ex->match_mutex);
- return REGEX_ERROR;
+ if (match_data_initialized == 0) {
+ match_data = pcre2_match_data_create(1, NULL);
+ match_data_initialized = 1;
+ __selinux_setspecific(match_data_key, match_data);
+ } else
+ match_data = __selinux_getspecific(match_data_key);
+
+ slow = (match_data == NULL);
+ if (slow) {
+ match_data = pcre2_match_data_create_from_pattern(regex->regex,
+ NULL);
}
-#else
- match_data = regex->match_data;
-#endif
rc = pcre2_match(
regex->regex, (PCRE2_SPTR)subject, PCRE2_ZERO_TERMINATED, 0,
partial ? PCRE2_PARTIAL_SOFT : 0, match_data, NULL);
-#ifdef AGGRESSIVE_FREE_AFTER_REGEX_MATCH
- // pcre2_match allocates heap and it won't be freed until
- // pcre2_match_data_free, resulting in heap overhead.
- pcre2_match_data_free(match_data);
-#endif
+ if (slow)
+ pcre2_match_data_free(match_data);
- __pthread_mutex_unlock(®ex->match_mutex);
- if (rc > 0)
+ if (rc >= 0)
return REGEX_MATCH;
switch (rc) {
case PCRE2_ERROR_PARTIAL:
@@ -290,7 +268,12 @@ struct regex_data *regex_data_create(void)
if (!regex_data)
return NULL;
- __pthread_mutex_init(®ex_data->match_mutex, NULL);
+ if (match_data_key_uninitialized) {
+ match_data_key_uninitialized = __selinux_key_create(
+ &match_data_key,
+ match_data_thread_free);
+ }
+
return regex_data;
}
@@ -13,6 +13,7 @@ extern int selinux_page_size ;
#pragma weak pthread_key_create
#pragma weak pthread_key_delete
#pragma weak pthread_setspecific
+#pragma weak pthread_getspecific
/* Call handler iff the first call. */
#define __selinux_once(ONCE_CONTROL, INIT_FUNCTION) \
@@ -41,6 +42,9 @@ extern int selinux_page_size ;
pthread_setspecific(KEY, VALUE); \
} while (0)
+#define __selinux_getspecific(KEY) \
+ (pthread_getspecific != NULL ? pthread_getspecific(KEY) : NULL)
+
/* selabel_lookup() is only thread safe if we're compiled with pthreads */
#pragma weak pthread_mutex_init
Since 30b3e9d2 (libselinux: Workaround for heap overhead of pcre, 2023-01-12), performance of PCRE2 matches has been affected due to excesive recreation of the match_data in an attempt to reduce memory utilization, but instead of a workaround, it would be better to address the problem and maybe even improve performance in the process. The issue is that currently the structure that holds PCRE state has both a pcre2_code (which is per pattern) and a pcre2_match_data (which is per match), forcing us to add a mutex to prevent multiple matches to step on each other. Lets remove the match_data and the mutex and instead allocate one once in a thread independent way that could be used and reused, by extending our pthread inteface to not only store TLS variables but also retrieve them, and use one of those. Since we are not interested on the capture groups (if any) lets only allocate 1 pair which is all that will be needed and change the logic so that a return of 0 (which means the pattern matched but there were not enough fields) is also considered a match. This will ensure that the memory use would be bound to the number of concurrent matches instead of the number of patterns and therefore reduce the impact that recent changes on the way the frames used for matching are allocated might had brough since 10.41 was released. Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com> --- Sent as an RFC since it has been very lightly tested (I can't even build the whole project), and because I couldn't figure out where to destroy the key, so it is adding a once on a lifetime leak of a pointer. It is also more verbose than it needs, because I am combining it with the revert of the workaround, and that could be split away, but that would hopefully help with testing as well. libselinux/src/regex.c | 77 ++++++++++++------------------- libselinux/src/selinux_internal.h | 4 ++ 2 files changed, 34 insertions(+), 47 deletions(-)