[LTP] [PATCH v3] syscalls/mlock05: add mlock test for locking and pre-faulting of memory

[Filippo Storniolo]

check Rss and Locked variables from /proc/$pid/smaps of the
the new memory mapping.
Rss and Locked size should be equal to the size
of the memory allocation.

Co-developed-by: Dennis Brendel <dbrendel@redhat.com>
Signed-off-by: Filippo Storniolo <fstornio@redhat.com>
---
 runtest/syscalls                           |   1 +
 testcases/kernel/syscalls/mlock/.gitignore |   1 +
 testcases/kernel/syscalls/mlock/mlock05.c  | 107 +++++++++++++++++++++
 3 files changed, 109 insertions(+)
 create mode 100644 testcases/kernel/syscalls/mlock/mlock05.c

diff --git a/runtest/syscalls b/runtest/syscalls
index 252123d8b..05a52fc8f 100644
--- a/runtest/syscalls
+++ b/runtest/syscalls
@@ -781,6 +781,7 @@ mlock01 mlock01
 mlock02 mlock02
 mlock03 mlock03 -i 20
 mlock04 mlock04
+mlock05 mlock05
 
 mlock201 mlock201
 mlock202 mlock202
diff --git a/testcases/kernel/syscalls/mlock/.gitignore b/testcases/kernel/syscalls/mlock/.gitignore
index 306574bbc..1872229b8 100644
--- a/testcases/kernel/syscalls/mlock/.gitignore
+++ b/testcases/kernel/syscalls/mlock/.gitignore
@@ -2,3 +2,4 @@
 /mlock02
 /mlock03
 /mlock04
+/mlock05
diff --git a/testcases/kernel/syscalls/mlock/mlock05.c b/testcases/kernel/syscalls/mlock/mlock05.c
new file mode 100644
index 000000000..e7714453f
--- /dev/null
+++ b/testcases/kernel/syscalls/mlock/mlock05.c
@@ -0,0 +1,107 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright Red Hat
+ * Author: Filippo Storniolo <fstornio@redhat.com>
+ */
+
+/*\
+ * [Description]
+ *
+ * Verify mlock() causes pre-faulting of PTEs and prevent memory to be swapped out.
+ *
+ * Find the new mapping in /proc/$pid/smaps and check Rss and Locked fields after
+ * mlock syscall:
+ * - Rss and Locked size should be equal to the size of the memory allocation
+ */
+
+#include "tst_test.h"
+
+#define MMAPLEN			(1UL<<20)
+#define LINELEN			256
+
+static unsigned long get_proc_smaps_field(unsigned long desired_mapping_address, char *desired_field)
+{
+	bool mapping_found = false;
+	char buffer[LINELEN] = "";
+	FILE *file = NULL;
+	int ret = 0;
+
+	file = fopen("/proc/self/smaps", "r");
+	if (file == NULL) {
+		tst_brk(TBROK | TERRNO, "cannot open file proc/self/smaps");
+		return 0;
+	}
+
+	// find desired field
+	while (fgets(buffer, LINELEN, file) != NULL) {
+		unsigned long mapping_address;
+
+		// check the starting address
+		ret = sscanf(buffer, "%lx[^-]", &mapping_address);
+
+		// most lines will not match the pattern for the mapping address
+		// so it is not treated as an error
+		if (ret == -1)
+			continue;
+
+		if (mapping_address == desired_mapping_address) {
+			mapping_found = true;
+			break;
+		}
+	}
+
+	if (!mapping_found) {
+		tst_brk(TBROK, "cannot find mapping %lx in proc/self/smaps", desired_mapping_address);
+		return 0;
+	}
+
+	// find desired field
+	while (fgets(buffer, LINELEN, file) != NULL) {
+		if (strstr(buffer, desired_field) != NULL) {
+			unsigned long desired_value;
+
+			// extract the value for the requested field
+			ret = sscanf(buffer, "%*[^0-9]%lu%*[^0-9]", &desired_value);
+			fclose(file);
+			if (ret != 1) {
+				tst_brk(TBROK, "failure occured while reading field %s", desired_field);
+				return 0;
+			}
+			return desired_value;
+		}
+	}
+
+	fclose(file);
+	tst_brk(TBROK, "cannot find %s field", desired_field);
+
+	return 0;
+}
+
+static void verify_mlock(void)
+{
+	unsigned long Rss;
+	unsigned long Locked;
+	char *buf;
+
+	buf = SAFE_MMAP(NULL, MMAPLEN, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	SAFE_MLOCK(buf, MMAPLEN);
+
+	printf("buf is %p\n", buf);
+
+	Rss = get_proc_smaps_field((unsigned long)buf, "Rss");
+	Locked = get_proc_smaps_field((unsigned long)buf, "Locked");
+
+	// Convertion from KiB to B
+	Rss *= 1024;
+	Locked *= 1024;
+
+	TST_EXP_EQ_LU(Rss, MMAPLEN);
+	TST_EXP_EQ_LU(Locked, MMAPLEN);
+
+	SAFE_MUNLOCK(buf, MMAPLEN);
+	SAFE_MUNMAP(buf, MMAPLEN);
+}
+
+static struct tst_test test = {
+	.test_all = verify_mlock,
+};
-- 
2.44.0