commit 3a6c9a855195e6f6f44ad6dffe2cd4046426ab53

Author: Masahiko, Yamada <yamada.masahiko@fujitsu.com>

Date:   Wed Nov 25 21:46:26 2020 +0900

    fix for performance improvement of _mx_init_component() function

diff --git a/src/components/mx/linux-mx.c b/src/components/mx/linux-mx.c

index 2da406d14..34e6f02c2 100644

--- a/src/components/mx/linux-mx.c

+++ b/src/components/mx/linux-mx.c

@@ -224,26 +224,35 @@ _mx_init_component( int cidx )

 {

 	FILE *fff;

-	char test_string[BUFSIZ];

+	char *path;

+	int len, pathlen;

 	/* detect if MX available */

-	strncpy(mx_counters_exe,"mx_counters 2> /dev/null",BUFSIZ);

-	fff=popen(mx_counters_exe,"r");

-	/* popen only returns NULL if "sh" fails, not the actual command */

-	if (fgets(test_string,BUFSIZ,fff)==NULL) {

-	   pclose(fff);

-	   strncpy(mx_counters_exe,"./components/mx/utils/fake_mx_counters 2> /dev/null",BUFSIZ);

-	   fff=popen(mx_counters_exe,"r");

-	   if (fgets(test_string,BUFSIZ,fff)==NULL) {

-	      pclose(fff);

-	      /* neither real nor fake found */

-	      strncpy(_mx_vector.cmp_info.disabled_reason,

-		      "No MX utilities found",PAPI_MAX_STR_LEN);

-	      return PAPI_ECMP;

+	path = getenv("PATH");

+	pathlen = strlen(path);

+	while(pathlen > 0) {

+	   len = strcspn(path, ":");

+	   strncpy(mx_counters_exe, path, len);

+	   mx_counters_exe[len] = '\0';

+	   strcat(mx_counters_exe, "/mx_counters");

+	   fff = fopen(mx_counters_exe, "r");

+	   if (fff != NULL) {

+	      strcat(mx_counters_exe, " 2> /dev/null");

+	      break;

 	   }

+	   pathlen = pathlen - len - 1;

+	   if (pathlen > 0) {

+	      path = path + len + 1;

+	   }

+	}

+	if (fff == NULL) {

+	   /* neither real nor fake found */

+	   strncpy(_mx_vector.cmp_info.disabled_reason,

+		   "No MX utilities found",PAPI_MAX_STR_LEN);

+	   return PAPI_ECMP;

 	}

-	pclose(fff);

+	fclose(fff);

 	num_events=MX_MAX_COUNTERS;

 	_mx_vector.cmp_info.num_native_events=num_events;

commit 3a2560a86be44f4b15d96a45eda8e7f387b9166c

Author: Masahiko, Yamada <yamada.masahiko@fujitsu.com>

Date:   Tue Jan 26 16:30:40 2021 +0900

    Add string length check before strncpy() and strcat() calls in _mx_init_component()

    Myrinet Express-related component MX modules are initialized with the _mx_init_component() function,

    which is called from the PAPI_library_init() function.

    The popen(3) call runs a loadable module called "mx_counters",

    and if the loadable module does not exist,

    it attempts to run a loadable module called "./components/mx/utils/fake_mx_counters".

    In an environment where there are no "mx_counters" and "./components/mx/utils/fake_mx_counters" loadable modules,

    popen(3) will be called twice uselessly.

    popen(3) internally calls pipe(2) once, fork(2) twice and exec(2) once.

    The size of the user space of the application calling the PAPI_library_init() function affects the performance of fork(2),

    which is called as an extension of popen(3).

    As a result, the performance of the PAPI_library_init() function is affected by the amount of user space in the application

    that called the PAPI_library_init() function.

    In the _mx_init_component() function,

    the MX module only needs to be able to verify that a load module named "mx_counters" exists.

    We improved the _mx_init_component() function to call fopen(3) instead of popen(3).

    We add string length check before strncpy() and strcat() calls in _mx_init_component() function.

diff --git a/src/components/mx/linux-mx.c b/src/components/mx/linux-mx.c

index 34e6f02c2..c2920d65b 100644

--- a/src/components/mx/linux-mx.c

+++ b/src/components/mx/linux-mx.c

@@ -225,7 +225,7 @@ _mx_init_component( int cidx )

 	FILE *fff;

 	char *path;

-	int len, pathlen;

+	int checklen, len, pathlen;

 	/* detect if MX available */

@@ -233,13 +233,31 @@ _mx_init_component( int cidx )

 	pathlen = strlen(path);

 	while(pathlen > 0) {

 	   len = strcspn(path, ":");

-	   strncpy(mx_counters_exe, path, len);

+	   if (len < BUFSIZ) {

+	      strncpy(mx_counters_exe, path, len);

+	   } else {

+	      fff = NULL;

+	      break;

+	   }

 	   mx_counters_exe[len] = '\0';

-	   strcat(mx_counters_exe, "/mx_counters");

+	   checklen = len + strlen("/mx_counters");

+	   if (checklen < BUFSIZ) {

+	      strcat(mx_counters_exe, "/mx_counters");

+	   } else {

+	      fff = NULL;

+	      break;

+	   }

 	   fff = fopen(mx_counters_exe, "r");

 	   if (fff != NULL) {

-	      strcat(mx_counters_exe, " 2> /dev/null");

-	      break;

+	      checklen = checklen + strlen(" 2> /dev/null");

+	      if (checklen < BUFSIZ) {

+	         strcat(mx_counters_exe, " 2> /dev/null");

+	         break;

+	      } else {

+	         fclose(fff);

+	         fff = NULL;

+	         break;

+	      }

 	   }

 	   pathlen = pathlen - len - 1;

 	   if (pathlen > 0) {

@@ -247,7 +265,7 @@ _mx_init_component( int cidx )

 	   }

 	}

 	if (fff == NULL) {

-	   /* neither real nor fake found */

+	   /* mx_counters not found */

 	   strncpy(_mx_vector.cmp_info.disabled_reason,

 		   "No MX utilities found",PAPI_MAX_STR_LEN);

 	   return PAPI_ECMP;