[LTP] [PATCH 1/8] Hugetlb: Migrating libhugetlbfs fork-cow

[Tarun Sahu]

Migrating the libhugetlbfs/testcases/fork-cow.c test

Test Description: This checks copy-on-write semantics, specifically the
semantics of a MAP_PRIVATE mapping across a fork().  Some versions of the
powerpc kernel had a bug in huge_ptep_set_wrprotect() which would fail to
flush the hash table after setting the write protect bit in the parent's
page tables, thus allowing the parent to pollute the child's mapping.

Signed-off-by: Tarun Sahu <tsahu@linux.ibm.com>
---
 runtest/hugetlb                               |   2 +
 testcases/kernel/mem/.gitignore               |   1 +
 .../kernel/mem/hugetlb/hugefork/Makefile      |  10 ++
 .../kernel/mem/hugetlb/hugefork/hugefork01.c  | 108 ++++++++++++++++++
 4 files changed, 121 insertions(+)
 create mode 100644 testcases/kernel/mem/hugetlb/hugefork/Makefile
 create mode 100644 testcases/kernel/mem/hugetlb/hugefork/hugefork01.c

diff --git a/runtest/hugetlb b/runtest/hugetlb
index ec1fc2515..4c16e1e7c 100644
--- a/runtest/hugetlb
+++ b/runtest/hugetlb
@@ -1,6 +1,8 @@
 hugefallocate01 hugefallocate01
 hugefallocate02 hugefallocate02
 
+hugefork01 hugefork01
+
 hugemmap01 hugemmap01
 hugemmap02 hugemmap02
 hugemmap04 hugemmap04
diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
index c0906f3d3..adea760c7 100644
--- a/testcases/kernel/mem/.gitignore
+++ b/testcases/kernel/mem/.gitignore
@@ -1,6 +1,7 @@
 /cpuset/cpuset01
 /hugetlb/hugefallocate/hugefallocate01
 /hugetlb/hugefallocate/hugefallocate02
+/hugetlb/hugefork/hugefork01
 /hugetlb/hugemmap/hugemmap01
 /hugetlb/hugemmap/hugemmap02
 /hugetlb/hugemmap/hugemmap04
diff --git a/testcases/kernel/mem/hugetlb/hugefork/Makefile b/testcases/kernel/mem/hugetlb/hugefork/Makefile
new file mode 100644
index 000000000..77ebb0aef
--- /dev/null
+++ b/testcases/kernel/mem/hugetlb/hugefork/Makefile
@@ -0,0 +1,10 @@
+# SPDX-License-Identifier: GPL-2.0-or-later
+# Copyright (C) 2009, Cisco Systems Inc.
+# Ngie Cooper, July 2009
+
+top_srcdir		?= ../../../../..
+
+include $(top_srcdir)/include/mk/testcases.mk
+include $(abs_srcdir)/../Makefile.inc
+include $(top_srcdir)/include/mk/generic_leaf_target.mk
+
diff --git a/testcases/kernel/mem/hugetlb/hugefork/hugefork01.c b/testcases/kernel/mem/hugetlb/hugefork/hugefork01.c
new file mode 100644
index 000000000..b59c461e3
--- /dev/null
+++ b/testcases/kernel/mem/hugetlb/hugefork/hugefork01.c
@@ -0,0 +1,108 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+/*
+ * Copyright (C) 2008 David Gibson, IBM Corporation.
+ * Author: David Gibson
+ */
+
+/*\
+ * [Description]
+ *
+ * This checks copy-on-write semantics, specifically the semantics of a
+ * MAP_PRIVATE mapping across a fork().  Some versions of the powerpc
+ * kernel had a bug in huge_ptep_set_wrprotect() which would fail to
+ * flush the hash table after setting the write protect bit in the parent's
+ * page tables, thus allowing the parent to pollute the child's mapping.
+ *
+ */
+
+#include <sys/wait.h>
+#include <sys/mman.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+
+#include "hugetlb.h"
+
+#define RANDOM_CONSTANT		0x1234ABCD
+#define OTHER_CONSTANT		0xfeef5678
+#define MNTPOINT "hugetlbfs/"
+static int  fd = -1;
+static long hpage_size;
+
+static void run_test(void)
+{
+	int status;
+	volatile unsigned int *p;
+	volatile unsigned int *child_readback;
+	int parent_readback;
+	pid_t pid;
+
+	child_readback = SAFE_MMAP(NULL, getpagesize(), PROT_READ|PROT_WRITE,
+			MAP_SHARED|MAP_ANONYMOUS, -1, 0);
+	*child_readback = 0;
+
+	p = SAFE_MMAP(NULL, hpage_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
+	*p = RANDOM_CONSTANT;
+
+	pid = SAFE_FORK();
+	if (pid != 0) {
+		*p = ~RANDOM_CONSTANT;
+		TST_CHECKPOINT_WAKE_AND_WAIT(0);
+		parent_readback = *p;
+		TST_CHECKPOINT_WAKE(0);
+	} else {
+		TST_CHECKPOINT_WAIT(0);
+		*child_readback = *p;
+		*p = OTHER_CONSTANT;
+		TST_CHECKPOINT_WAKE_AND_WAIT(0);
+		exit(0);
+	}
+
+	SAFE_WAITPID(pid, &status, 0);
+	if (WEXITSTATUS(status) != 0) {
+		tst_res(TFAIL, "Child failed: %d", WEXITSTATUS(status));
+		goto cleanup;
+	}
+
+	tst_res(TINFO, "child_readback = 0x%x, parent_readback = 0x%x",
+			*child_readback, parent_readback);
+
+	if (*child_readback != RANDOM_CONSTANT) {
+		tst_res(TFAIL, "Child read back 0x%x instead of 0x%x",
+		     *child_readback, RANDOM_CONSTANT);
+		goto cleanup;
+	}
+	if (parent_readback != ~RANDOM_CONSTANT) {
+		tst_res(TFAIL, "Parent read back 0x%x instead of 0x%x",
+		     parent_readback, RANDOM_CONSTANT);
+	} else
+		tst_res(TPASS, "Parent and child both read the expected values.");
+
+cleanup:
+	SAFE_MUNMAP((void *)p, hpage_size);
+	SAFE_MUNMAP((void *)child_readback, getpagesize());
+}
+
+static void setup(void)
+{
+	hpage_size = SAFE_READ_MEMINFO("Hugepagesize:")*1024;
+	fd = tst_creat_unlinked(MNTPOINT, 0);
+}
+
+static void cleanup(void)
+{
+	if (fd > 0)
+		SAFE_CLOSE(fd);
+}
+
+static struct tst_test test = {
+	.needs_root = 1,
+	.needs_checkpoints = 1,
+	.mntpoint = MNTPOINT,
+	.needs_hugetlbfs = 1,
+	.forks_child = 1,
+	.setup = setup,
+	.cleanup = cleanup,
+	.test_all = run_test,
+	.hugepages = {2, TST_NEEDS},
+};
-- 
2.31.1