[LTP] [PATCH 8/8] Hugetlb: Migrating libhugetlbfs misaligned_offset

[Tarun Sahu <tsahu@linux.ibm.com>]

Migrating the libhugetlbfs/testcases/misaligned_offset.c test

Test Name: Misaligned offset

Test Description: At one stage, a misconversion of hugetlb_vmtruncate_list
to a prio_tree meant that on 32-bit machines, truncates at or above 4GB
could truncate lower pages, resulting in BUG_ON()s.

WARNING: The offsets and addresses used within are specifically
calculated to trigger the bug as it existed.  Don't mess with them
unless you *really* know what you're doing.

The kernel bug in question was fixed with
'commit 856fc2950555 ("[PATCH] hugetlb: fix prio_tree unit")'.

Signed-off-by: Tarun Sahu <tsahu@linux.ibm.com>
---
 runtest/hugetlb                               |   1 +
 testcases/kernel/mem/.gitignore               |   1 +
 .../kernel/mem/hugetlb/hugemmap/hugemmap19.c  | 147 ++++++++++++++++++
 3 files changed, 149 insertions(+)
 create mode 100644 testcases/kernel/mem/hugetlb/hugemmap/hugemmap19.c

diff --git a/runtest/hugetlb b/runtest/hugetlb
index de76cdaf2..4da1525a7 100644
--- a/runtest/hugetlb
+++ b/runtest/hugetlb
@@ -20,6 +20,7 @@ hugemmap15 hugemmap15
 hugemmap16 hugemmap16
 hugemmap17 hugemmap17
 hugemmap18 hugemmap18
+hugemmap19 hugemmap19
 hugemmap05_1 hugemmap05 -m
 hugemmap05_2 hugemmap05 -s
 hugemmap05_3 hugemmap05 -s -m
diff --git a/testcases/kernel/mem/.gitignore b/testcases/kernel/mem/.gitignore
index daee70586..b6b3e5ddd 100644
--- a/testcases/kernel/mem/.gitignore
+++ b/testcases/kernel/mem/.gitignore
@@ -19,6 +19,7 @@
 /hugetlb/hugemmap/hugemmap16
 /hugetlb/hugemmap/hugemmap17
 /hugetlb/hugemmap/hugemmap18
+/hugetlb/hugemmap/hugemmap19
 /hugetlb/hugeshmat/hugeshmat01
 /hugetlb/hugeshmat/hugeshmat02
 /hugetlb/hugeshmat/hugeshmat03
diff --git a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap19.c b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap19.c
new file mode 100644
index 000000000..c5b29a701
--- /dev/null
+++ b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap19.c
@@ -0,0 +1,147 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+/*
+ * Copyright (C) 2005-2006 David Gibson & Adam Litke, IBM Corporation.
+ * Copyright (C) 2006 Hugh Dickins <hugh@veritas.com>
+ * Author: David Gibson & Adam Litke
+ */
+
+/*\
+ * [Descripiton]
+ *
+ * At one stage, a misconversion of hugetlb_vmtruncate_list to a
+ * prio_tree meant that on 32-bit machines, truncates at or above 4GB
+ * could truncate lower pages, resulting in BUG_ON()s.
+ *
+ * WARNING: The offsets and addresses used within are specifically
+ * calculated to trigger the bug as it existed.  Don't mess with them
+ * unless you *really* know what you're doing.
+ *
+ * The kernel bug in question was fixed with commit
+ * 856fc29505556cf263f3dcda2533cf3766c14ab6.
+ */
+
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <sys/mount.h>
+#include <limits.h>
+#include <sys/param.h>
+#include <sys/types.h>
+
+#include "hugetlb.h"
+
+#define RANDOM_CONSTANT	0x1234ABCD
+#define MNTPOINT "hugetlbfs/"
+static int page_size;
+static long hpage_size;
+static int  fd = -1;
+
+static void run_test(void)
+{
+	off_t buggy_offset;
+	void *p, *q;
+	volatile int *pi;
+	int err;
+
+	/*
+	 * First, we make a 2 page sane hugepage mapping.  Then we
+	 * memset() it to ensure that the ptes are instantiated for
+	 * it.  Then we attempt to replace the second half of the map
+	 * with one at a bogus offset.  We leave the first page of
+	 * sane mapping in place to ensure that the corresponding
+	 * pud/pmd/whatever entries aren't cleaned away.  It's those
+	 * bad entries which can trigger bad_pud() checks if the
+	 * backout path for the bogus mapping is buggy, which it was
+	 * in some kernels.
+	 */
+	tst_res(TINFO, "Initial free hugepages: %lu",
+		SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE));
+
+	/* First get arena of three hpages size, at file offset 4GB */
+	p = SAFE_MMAP(NULL, 2*hpage_size, PROT_READ|PROT_WRITE, MAP_PRIVATE, fd, 0);
+
+	tst_res(TINFO, "After Mapping reference map, Free hugepages: %lu",
+		SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE));
+	tst_res(TINFO, "Mapped Address Range: %p-%p", p, p+2*hpage_size-1);
+
+	memset(p, 0, 2*hpage_size);
+	pi = p;
+	*pi = RANDOM_CONSTANT;
+
+	tst_res(TINFO, "After instantiate the pages, Free hugepages: %lu",
+		   SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE));
+
+	/*
+	 * Toggle the permissions on the first page.  This forces TLB
+	 * entries (including hash page table on powerpc) to be
+	 * flushed, so that the page tables must be accessed for the
+	 * test further down.  In the buggy case, those page tables
+	 * can get thrown away by a pud_clear()
+	 */
+	err = mprotect(p, hpage_size, PROT_READ);
+	if (err)
+		tst_brk(TBROK|TERRNO, "mprotect(%p, 0x%lx, PROT_READ)", p, hpage_size);
+
+	/* Replace top hpage by hpage mapping at confusing file offset */
+	buggy_offset = page_size;
+	tst_res(TINFO, "Replacing map at %p with map from offset 0x%lx...",
+	       p + hpage_size, (unsigned long)buggy_offset);
+	q = mmap(p + hpage_size, hpage_size, PROT_READ|PROT_WRITE,
+		 MAP_FIXED|MAP_PRIVATE, fd, buggy_offset);
+	if (q != MAP_FAILED) {
+		tst_res(TFAIL|TERRNO, "bogus offset mmap() succeeded at %p", q);
+		goto cleanup;
+	}
+	if (errno != EINVAL) {
+		tst_res(TFAIL|TERRNO, "bogus mmap() failed should be \"%s\" but it is",
+		     tst_strerrno(EINVAL));
+		goto cleanup;
+	}
+
+	tst_res(TINFO, "After Mapping with buggy offset, Free hugepages: %lu",
+		SAFE_READ_MEMINFO(MEMINFO_HPAGE_FREE));
+
+	if (*pi != RANDOM_CONSTANT) {
+		tst_res(TFAIL, "Pre-existing mapping clobbered: %x instead of %x",
+		     *pi, RANDOM_CONSTANT);
+		goto cleanup;
+	}
+
+	/*
+	 * The real test is whether we got a bad_pud() or similar
+	 * during the run.  The check above, combined with the earlier
+	 * mprotect()s to flush the TLB are supposed to catch it, but
+	 * it's hard to be certain.  Once bad_pud() is called
+	 * behaviour can be very strange.
+	 */
+
+	tst_res(TPASS, "Successful but inconclusive");
+cleanup:
+	SAFE_MUNMAP(p, 2*hpage_size);
+}
+
+static void setup(void)
+{
+	page_size = getpagesize();
+	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 = {
+	.tags = (struct tst_tag[]) {
+		{"linux-git", "856fc2950555"},
+		{}
+	},
+	.needs_root = 1,
+	.mntpoint = MNTPOINT,
+	.needs_hugetlbfs = 1,
+	.setup = setup,
+	.cleanup = cleanup,
+	.test_all = run_test,
+	.hugepages = {4, TST_NEEDS},
+};
-- 
2.31.1


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