[LTP] [PATCH v3] Hugetlb: Migrating libhugetlbfs shm-perms

[Spoorthy]

Test Description: Tests the behavior of shared memory when
multiple threads attach to a segment with different permissions. 

At one point, reservation accounting of free hugepages between the parent
and child processes may become inconsistent during memory operations.
The parent creates 4 hugepages and a shared memory segment
(size segment_size, permission 0640), attaches it, and initializes
four parts with a pattern (0x55), then detaches it. Child processes
are created in a loop, each reattaching the segment in read-only mode
with SHM_RDONLY, detaching, and exiting. If attach/detach fails or
if the reservation accounting of free hugepages doesn't match
between parent and child, the test fails. If all child processes exit
successfully and accounting matches, the test passes.

Tested and verified the success of test case

Signed-off-by: Spoorthy <spoorthy@linux.ibm.com>
---
 runtest/hugetlb                               |  1 +
 testcases/kernel/mem/.gitignore               |  1 +
 .../mem/hugetlb/hugeshmat/hugeshmat06.c       | 97 +++++++++++++++++++
 3 files changed, 99 insertions(+)
 create mode 100644 testcases/kernel/mem/hugetlb/hugeshmat/hugeshmat06.c

diff --git a/runtest/hugetlb b/runtest/hugetlb
index 299c07ac9..240701b2b 100644
--- a/runtest/hugetlb
+++ b/runtest/hugetlb
@@ -44,6 +44,7 @@ hugeshmat02 hugeshmat02 -i 5
 hugeshmat03 hugeshmat03 -i 5
 hugeshmat04 hugeshmat04 -i 5
 hugeshmat05 hugeshmat05 -i 5
+hugeshmat06 hugeshmat06
 
 hugeshmctl01 hugeshmctl01 -i 5
 hugeshmctl02 hugeshmctl02 -i 5
diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
index c96fe8bfc..4ad1dc313 100644
--- a/testcases/kernel/mem/.gitignore
+++ b/testcases/kernel/mem/.gitignore
@@ -39,6 +39,7 @@
 /hugetlb/hugeshmat/hugeshmat03
 /hugetlb/hugeshmat/hugeshmat04
 /hugetlb/hugeshmat/hugeshmat05
+/hugetlb/hugeshmat/hugeshmat06
 /hugetlb/hugeshmctl/hugeshmctl01
 /hugetlb/hugeshmctl/hugeshmctl02
 /hugetlb/hugeshmctl/hugeshmctl03
diff --git a/testcases/kernel/mem/hugetlb/hugeshmat/hugeshmat06.c b/testcases/kernel/mem/hugetlb/hugeshmat/hugeshmat06.c
new file mode 100644
index 000000000..bcb31b1d4
--- /dev/null
+++ b/testcases/kernel/mem/hugetlb/hugeshmat/hugeshmat06.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2005-2006, IBM Corporation.
+ * Author: David Gibson & Adam Litke
+ */
+/*\
+ * [DESCRIPTION]
+ * Test shared memory behavior when multiple threads are attached
+ * to a segment with different permissions.  A segment is created
+ * and children attach read-only to check reservation accounting.
+ */
+
+#include "hugetlb.h"
+#include "tst_safe_sysv_ipc.h"
+
+#define SEGMENT_KEY (0x82ba15ff)
+#define MNTPOINT "hugetlbfs/"
+#define HPAGES_IN_SEGMENT 4
+
+static int global_shmid = -1;
+static void *shmaddr;
+static long segment_size, hpage_size, stride;
+
+static int attach_segment(size_t segsize, int shmflags, int shmperms)
+{
+	int shmid;
+
+	shmid = SAFE_SHMGET(SEGMENT_KEY, segsize, shmflags);
+	shmaddr = SAFE_SHMAT(shmid, shmaddr, shmperms);
+	global_shmid = shmid;
+	return shmid;
+}
+
+static void setup(void)
+{
+	hpage_size = tst_get_hugepage_size();
+	segment_size = 4 * hpage_size;
+	stride = hpage_size;
+}
+
+static void compare_free_hugepage_memory(long free_end, long free_start)
+{
+	if (free_end != free_start)
+		tst_res(TFAIL, "Free hugepages after attaching multiple threads differ from initial allocation");
+}
+
+static void run_test(void)
+{
+	char *p;
+	int i, iterations;
+	long total_hpages, free_start, free_end, val;
+
+	total_hpages = SAFE_READ_MEMINFO(MEMINFO_HPAGE_TOTAL);
+	iterations = (total_hpages * hpage_size) / segment_size+1;
+	attach_segment(segment_size, IPC_CREAT | SHM_HUGETLB | 0640, 0);
+	p = (char *)shmaddr;
+	for (i = 0; i < 4; i++, p += stride)
+		memset(p, 0x55, stride);
+	free_start = SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE);
+	SAFE_SHMDT((const void *)shmaddr);
+	for (i = 0; i < iterations; i++) {
+		pid_t pid;
+
+		pid = SAFE_FORK();
+		if (!pid) {
+			attach_segment(0, 0, SHM_RDONLY);
+			for (i = 0; i < HPAGES_IN_SEGMENT; i++)
+				val = *((char *)shmaddr + (i * hpage_size));
+			SAFE_SHMDT(((const void *)shmaddr));
+			free_end = SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE);
+			compare_free_hugepage_memory(free_end, free_start);
+			exit(EXIT_SUCCESS);
+		}
+	}
+	free_end = SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE);
+	compare_free_hugepage_memory(free_end, free_start);
+	tst_reap_children();
+	tst_res(TPASS, "Successfully tested shared memory behavior when multiple threads are attached");
+}
+
+static void cleanup(void)
+{
+	if (global_shmid >= 0)
+		SAFE_SHMCTL(global_shmid, IPC_RMID, NULL);
+}
+
+static struct tst_test test = {
+	.needs_root = 1,
+	.mntpoint = MNTPOINT,
+	.needs_hugetlbfs = 1,
+	.needs_tmpdir = 1,
+	.forks_child = 1,
+	.setup = setup,
+	.cleanup = cleanup,
+	.test_all = run_test,
+	.hugepages = {32, TST_NEEDS},
+};
-- 
2.43.0