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;