[LTP] [PATCH v2 8/8] Hugetlb: Migrating libhugetlbfs misaligned_offset

Tarun Sahu
2022-12-20T06:32:48Z

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>
Reviewed-by: Richard Palethorpe <rpalethorpe@suse.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..11060125b
--- /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
+ * 856fc2950555.
+ */
+
+#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},