[PATCH v3] selftests:proc Add /proc/$(pid)/statm output validation

[Swarup Laxman Kotiaklapudi]

Add /proc/${pid}/statm validation

/proc/$(pid)/statm output is expected to be:
 "0 0 0 * 0 0 0\n"
Here * can be any value

Read output of /proc/$(pid)/statm
and check except for 4th position,
all other positions have value zero.

Fixes: 5bc73bb3451b (proc: test how it holds up with mapping'less process)
Signed-off-by: Swarup Laxman Kotiaklapudi <swarupkotikalapudi@xxxxxxxxx>
---

 Changes in V3:
- Remove wrong comment "/proc/${pid}/statm is under
  CONFIG_PROC_PAGE_MONITOR"
- read() function usage is change

 Changes in V2:
- 4th field if zero it will assert
- field other than 4th field is checked for zero value
- clean up of function test_proc_pid_statm()

 tools/testing/selftests/proc/proc-empty-vm.c | 60 ++++++++++++++++++--
 1 file changed, 55 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/proc/proc-empty-vm.c b/tools/testing/selftests/proc/proc-empty-vm.c
index b16c13688b88..bc76e8bba7e4 100644
--- a/tools/testing/selftests/proc/proc-empty-vm.c
+++ b/tools/testing/selftests/proc/proc-empty-vm.c
@@ -38,6 +38,8 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
+#include "../kselftest.h"
+
 #ifdef __amd64__
 #define TEST_VSYSCALL
 #endif
@@ -302,6 +304,57 @@ static int test_proc_pid_smaps_rollup(pid_t pid)
 	}
 }
 
+static int test_proc_pid_statm(pid_t pid)
+{
+	char buf[4096];
+	char *tok;
+	char *string, *p;
+	int non_zero_value_indx = 4;
+	int i = 1, len;
+        size_t left;
+
+	snprintf(buf, sizeof(buf), "/proc/%u/statm", pid);
+
+	/*
+	 *  Output can be "0 0 0 2 0 0 0\n" where "2" can be anything.
+	 */
+	int fd = open(buf, O_RDONLY);
+
+	if (fd == -1) {
+		if (errno == ENOENT) {
+			return EXIT_SUCCESS;
+		}
+		perror("open /proc/${pid}/statm");
+		return EXIT_FAILURE;
+	} else {
+		memset(buf, 0, sizeof(buf));
+		left = ARRAY_SIZE(buf);
+		p = buf;
+		while ((len = read(fd, p, left)) > 0) {
+			p += len;
+			left -= len;
+		}
+		close(fd);
+		string = buf;
+
+		while ((tok = strsep(&string, " ")) != NULL) {
+			if (i == non_zero_value_indx) {
+				if (!strncmp(tok, "0", 1))
+					goto err_statm;
+			} else {
+				if (strncmp(tok, "0", 1))
+					goto err_statm;
+			}
+			i++;
+		}
+	}
+
+	return EXIT_SUCCESS;
+
+err_statm:
+	assert(0);
+}
+
 int main(void)
 {
 	int rv = EXIT_SUCCESS;
@@ -388,11 +441,8 @@ int main(void)
 		if (rv == EXIT_SUCCESS) {
 			rv = test_proc_pid_smaps_rollup(pid);
 		}
-		/*
-		 * TODO test /proc/${pid}/statm, task_statm()
-		 * ->start_code, ->end_code aren't updated by munmap().
-		 * Output can be "0 0 0 2 0 0 0\n" where "2" can be anything.
-		 */
+		if (rv == EXIT_SUCCESS)
+			rv = test_proc_pid_statm(pid);
 
 		/* Cut the rope. */
 		int wstatus;
-- 
2.34.1