Patch "selftests/resctrl: Fix incorrect parsing of iMC counters" has been added to the 5.10-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    selftests/resctrl: Fix incorrect parsing of iMC counters

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     selftests-resctrl-fix-incorrect-parsing-of-imc-count.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit e781826ad69c6cb5995c82e5a918719c95cc2830
Author: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Date:   Wed Mar 17 02:22:53 2021 +0000

    selftests/resctrl: Fix incorrect parsing of iMC counters
    
    [ Upstream commit d81343b5eedf84be71a4313e8fd073d0c510afcf ]
    
    iMC (Integrated Memory Controller) counters are usually at
    "/sys/bus/event_source/devices/" and are named as "uncore_imc_<n>".
    num_of_imcs() function tries to count number of such iMC counters so that
    it could appropriately initialize required number of perf_attr structures
    that could be used to read these iMC counters.
    
    num_of_imcs() function assumes that all the directories under this path
    that start with "uncore_imc" are iMC counters. But, on some systems there
    could be directories named as "uncore_imc_free_running" which aren't iMC
    counters. Trying to read from such directories will result in "not found
    file" errors and MBM/MBA tests will fail.
    
    Hence, fix the logic in num_of_imcs() such that it looks at the first
    character after "uncore_imc_" to check if it's a numerical digit or not. If
    it's a digit then the directory represents an iMC counter, else, skip the
    directory.
    
    Reported-by: Reinette Chatre <reinette.chatre@xxxxxxxxx>
    Tested-by: Babu Moger <babu.moger@xxxxxxx>
    Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
    Signed-off-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/tools/testing/selftests/resctrl/resctrl_val.c b/tools/testing/selftests/resctrl/resctrl_val.c
index aed71fd0713b..5478c23c62ba 100644
--- a/tools/testing/selftests/resctrl/resctrl_val.c
+++ b/tools/testing/selftests/resctrl/resctrl_val.c
@@ -221,8 +221,8 @@ static int read_from_imc_dir(char *imc_dir, int count)
  */
 static int num_of_imcs(void)
 {
+	char imc_dir[512], *temp;
 	unsigned int count = 0;
-	char imc_dir[512];
 	struct dirent *ep;
 	int ret;
 	DIR *dp;
@@ -230,7 +230,25 @@ static int num_of_imcs(void)
 	dp = opendir(DYN_PMU_PATH);
 	if (dp) {
 		while ((ep = readdir(dp))) {
-			if (strstr(ep->d_name, UNCORE_IMC)) {
+			temp = strstr(ep->d_name, UNCORE_IMC);
+			if (!temp)
+				continue;
+
+			/*
+			 * imc counters are named as "uncore_imc_<n>", hence
+			 * increment the pointer to point to <n>. Note that
+			 * sizeof(UNCORE_IMC) would count for null character as
+			 * well and hence the last underscore character in
+			 * uncore_imc'_' need not be counted.
+			 */
+			temp = temp + sizeof(UNCORE_IMC);
+
+			/*
+			 * Some directories under "DYN_PMU_PATH" could have
+			 * names like "uncore_imc_free_running", hence, check if
+			 * first character is a numerical digit or not.
+			 */
+			if (temp[0] >= '0' && temp[0] <= '9') {
 				sprintf(imc_dir, "%s/%s/", DYN_PMU_PATH,
 					ep->d_name);
 				ret = read_from_imc_dir(imc_dir, count);