[PATCH] hugemmap36: Migrate the libhugetlbfs/testcases/truncate_above_4GB.c test

Test for a bug where truncating hugepage files at offsets >= 4GB on
32-bit systems could incorrectly truncate lower pages due to a
misconversion of hugetlb_vmtruncate_list to a prio_tree.
This test verifies that:
- Pages below 4GB remain accessible after truncation at 4GB
- Pages at or above the truncation point correctly trigger SIGBUS

Signed-off-by: Pavithra <[email protected]>
---
 runtest/hugetlb                               |   1 +
 testcases/kernel/mem/.gitignore               |   1 +
 .../kernel/mem/hugetlb/hugemmap/hugemmap36.c  | 160 ++++++++++++++++++
 3 files changed, 162 insertions(+)
 create mode 100644 testcases/kernel/mem/hugetlb/hugemmap/hugemmap36.c

diff --git a/runtest/hugetlb b/runtest/hugetlb
index 8ee0e6f82..5ea76df35 100644
--- a/runtest/hugetlb
+++ b/runtest/hugetlb
@@ -37,6 +37,7 @@ hugemmap31 hugemmap31
 hugemmap32 hugemmap32
 hugemmap34 hugemmap34
 hugemmap35 hugemmap35
+hugemmap36 hugemmap36
 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 0e59035df..1585b35bd 100644
--- a/testcases/kernel/mem/.gitignore
+++ b/testcases/kernel/mem/.gitignore
@@ -37,6 +37,7 @@
 /hugetlb/hugemmap/hugemmap32
 /hugetlb/hugemmap/hugemmap34
 /hugetlb/hugemmap/hugemmap35
+/hugetlb/hugemmap/hugemmap36
 /hugetlb/hugeshmat/hugeshmat01
 /hugetlb/hugeshmat/hugeshmat02
 /hugetlb/hugeshmat/hugeshmat03
diff --git a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap36.c b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap36.c
new file mode 100644
index 000000000..b48a34f59
--- /dev/null
+++ b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap36.c
@@ -0,0 +1,160 @@
+// SPDX-License-Identifier: LGPL-2.1-or-later
+/*
+ * Copyright (C) 2005-2006 David Gibson & Adam Litke, IBM Corporation.
+ * Copyright (c) 2026 Pavithra <[email protected]>
+ */
+
+/*\
+ * Test for a bug where truncating hugepage files at offsets >= 4GB on
+ * 32-bit systems could incorrectly truncate lower pages due to a
+ * misconversion of hugetlb_vmtruncate_list to a prio_tree.
+ *
+ * This test verifies that:
+ * - Pages below 4GB remain accessible after truncation at 4GB
+ * - Pages at or above the truncation point correctly trigger SIGBUS
+ *
+ * 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.
+ *
+ * Requires root to mount hugetlbfs.
+ */
+
+#define _GNU_SOURCE
+#define FOURGIG ((off64_t)0x100000000ULL)
+#define MNTPOINT "hugetlbfs/"
+
+#include <signal.h>
+#include <setjmp.h>
+#include "hugetlb.h"
+
+static int page_size;
+static long hpage_size;
+static int fd = -1;
+static long long buggy_offset;
+static volatile int test_pass;
+static sigjmp_buf sig_escape;
+
+static void sigbus_handler_fail(int signum LTP_ATTRIBUTE_UNUSED,
+				siginfo_t *si LTP_ATTRIBUTE_UNUSED,
+				void *uc LTP_ATTRIBUTE_UNUSED)
+{
+	test_pass = -1;
+	siglongjmp(sig_escape, 17);
+}
+
+static void sigbus_handler_pass(int signum LTP_ATTRIBUTE_UNUSED,
+				siginfo_t *si LTP_ATTRIBUTE_UNUSED,
+				void *uc LTP_ATTRIBUTE_UNUSED)
+{
+	test_pass = 1;
+	siglongjmp(sig_escape, 17);
+}
+
+static void run_test(void)
+{
+	void *p, *q;
+	volatile unsigned int *pi, *qi;
+
+	struct sigaction sa_pass = {
+		.sa_sigaction = sigbus_handler_pass,
+		.sa_flags = SA_SIGINFO,
+	};
+
+	struct sigaction sa_fail = {
+		.sa_sigaction = sigbus_handler_fail,
+		.sa_flags = SA_SIGINFO,
+	};
+
+	test_pass = 0;
+
+	buggy_offset = FOURGIG / (hpage_size / page_size);
+	buggy_offset = (long long)PALIGN(buggy_offset, hpage_size);
+
+	/* First get arena of three hpages size, at file offset 4GB */
+	q = SAFE_MMAP(NULL, 3*hpage_size, PROT_READ|PROT_WRITE,
+		      MAP_PRIVATE, fd, FOURGIG);
+	qi = q;
+	/* Touch the high page */
+	*qi = 0;
+
+	/* This part of the test makes the problem more obvious, but
+	 * is not essential.  It can't be done on segmented powerpc, where
+	 * segment restrictions prohibit us from performing such a
+	 * mapping, so skip it there. Similarly, ia64's address space
+	 * restrictions prevent this.
+	 */
+#if (defined(__powerpc__) && defined(PPC_NO_SEGMENTS)) || \
+	!defined(__powerpc__) && !defined(__powerpc64__) && \
+	!defined(__ia64__)
+	/* Replace middle hpage by tinypage mapping to trigger
+	 * nr_ptes BUG
+	 */
+	p = SAFE_MMAP(q + hpage_size, hpage_size, PROT_READ|PROT_WRITE,
+		      MAP_FIXED|MAP_PRIVATE|MAP_ANON, -1, 0);
+	pi = p;
+	/* Touch one page to allocate its page table */
+	*pi = 0;
+#endif
+
+	/* Replace top hpage by hpage mapping at confusing file offset */
+	p = SAFE_MMAP(q + 2*hpage_size, hpage_size, PROT_READ|PROT_WRITE,
+		      MAP_FIXED|MAP_PRIVATE, fd, buggy_offset);
+	pi = p;
+	/* Touch the low page with something non-zero */
+	*pi = 1;
+
+	SAFE_FTRUNCATE(fd, FOURGIG);
+
+	SAFE_SIGACTION(SIGBUS, &sa_fail, NULL);
+	if (sigsetjmp(sig_escape, 1) == 0) {
+		if (*pi != 1) {
+			tst_res(TFAIL, "Data 1 has changed!");
+			goto cleanup;
+		}
+	} else if (test_pass == -1) {
+		tst_res(TFAIL, "Unexpected SIGBUS on low-offset page (kernel bug present)");
+		goto cleanup;
+	}
+
+	SAFE_SIGACTION(SIGBUS, &sa_pass, NULL);
+	if (sigsetjmp(sig_escape, 1) == 0) {
+		*qi;
+		tst_res(TFAIL, "Didn't SIGBUS on truncated page.");
+	}
+
+	if (test_pass)
+		tst_res(TPASS, "Expected SIGBUS");
+
+cleanup:
+	SAFE_MUNMAP(q, 3*hpage_size);
+}
+
+static void setup(void)
+{
+	page_size = getpagesize();
+	hpage_size = tst_get_hugepage_size();
+	fd = tst_creat_unlinked(MNTPOINT, 0, 0600);
+	if (hpage_size > FOURGIG)
+		tst_brk(TCONF, "Huge page size is too large!");
+}
+
+static void cleanup(void)
+{
+	if (fd != -1)
+		SAFE_CLOSE(fd);
+}
+
+static struct tst_test test = {
+	.tags = (struct tst_tag[]) {
+		{"linux-git", "856fc2950555"},
+		{}
+	},
+	.needs_root = 1,
+	.mntpoint = MNTPOINT,
+	.needs_hugetlbfs = 1,
+	.hugepages = {4, TST_NEEDS},
+	.setup = setup,
+	.cleanup = cleanup,
+	.test_all = run_test,
+};
-- 
2.55.0


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