selftests: prctl: Add prctl test for PR_GET_NAME

This patch covers the testing of PR_GET_NAME by
reading it's value from proc/self/task/pid/comm
and matching it with the value returned by PR_GET_NAME.
If the values are matched then it's successful, otherwise
it fails.

changes since v1:
	- Handled fscanf,fopen error checking.
	- Defined MAX_PATH_LEN.

Signed-off-by: Osama Muhammad <osmtendev@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

Author: osmten

tools/testing/selftests/prctl/set-process-name.c

@@ -12,6 +12,7 @@
 #define CHANGE_NAME "changename"
 #define EMPTY_NAME ""
 #define TASK_COMM_LEN 16
+#define MAX_PATH_LEN 50
 
 int set_name(char *name)
 {
@@ -47,6 +48,35 @@ int check_null_pointer(char *check_name)
 	return res;
 }
 
+int check_name(void)
+{
+
+	int pid;
+
+	pid = getpid();
+	FILE *fptr = NULL;
+	char path[MAX_PATH_LEN] = {};
+	char name[TASK_COMM_LEN] = {};
+	char output[TASK_COMM_LEN] = {};
+	int j;
+
+	j = snprintf(path, MAX_PATH_LEN, "/proc/self/task/%d/comm", pid);
+	fptr = fopen(path, "r");
+	if (!fptr)
+		return -EIO;
+
+	fscanf(fptr, "%s", output);
+	if (ferror(fptr))
+		return -EIO;
+
+	int res = prctl(PR_GET_NAME, name, NULL, NULL, NULL);
+
+	if (res < 0)
+		return -errno;
+
+	return !strcmp(output, name);
+}
+
 TEST(rename_process) {
 
 	EXPECT_GE(set_name(CHANGE_NAME), 0);
@@ -57,6 +87,8 @@ TEST(rename_process) {
 
 	EXPECT_GE(set_name(CHANGE_NAME), 0);
 	EXPECT_LT(check_null_pointer(CHANGE_NAME), 0);
+
+	EXPECT_TRUE(check_name());
 }
 
 TEST_HARNESS_MAIN