selftests/mm: pagemap_scan ioctl: add PFN ZERO test cases

Add test cases to test the correctness of PFN ZERO flag of pagemap_scan
ioctl.  Test with normal pages backed memory and huge pages backed memory.

Link: https://lkml.kernel.org/r/20250707073321.106431-1-usama.anjum@collabora.com
Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Muhammad Usama Anjum <usama.anjum@collabora.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 69 insertions, 3 deletions

diff --git a/tools/testing/selftests/mm/pagemap_ioctl.c b/tools/testing/selftests/mm/pagemap_ioctl.c
index b07acc86f4f0..c2dcda78ad31 100644
--- a/tools/testing/selftests/mm/pagemap_ioctl.c
+++ b/tools/testing/selftests/mm/pagemap_ioctl.c
@@ -1,4 +1,5 @@
 // SPDX-License-Identifier: GPL-2.0
+
 #define _GNU_SOURCE
 #include <stdio.h>
 #include <fcntl.h>
@@ -34,8 +35,8 @@
 #define PAGEMAP "/proc/self/pagemap"
 int pagemap_fd;
 int uffd;
-unsigned long page_size;
-unsigned int hpage_size;
+size_t page_size;
+size_t hpage_size;
 const char *progname;
 
 #define LEN(region)	((region.end - region.start)/page_size)
@@ -1480,6 +1481,68 @@ static void transact_test(int page_size)
 			      extra_thread_faults);
 }
 
+void zeropfn_tests(void)
+{
+	unsigned long long mem_size;
+	struct page_region vec;
+	int i, ret;
+	char *mmap_mem, *mem;
+
+	/* Test with normal memory */
+	mem_size = 10 * page_size;
+	mem = mmap(NULL, mem_size, PROT_READ, MAP_PRIVATE | MAP_ANON, -1, 0);
+	if (mem == MAP_FAILED)
+		ksft_exit_fail_msg("error nomem\n");
+
+	/* Touch each page to ensure it's mapped */
+	for (i = 0; i < mem_size; i += page_size)
+		(void)((volatile char *)mem)[i];
+
+	ret = pagemap_ioctl(mem, mem_size, &vec, 1, 0,
+			    (mem_size / page_size), PAGE_IS_PFNZERO, 0, 0, PAGE_IS_PFNZERO);
+	if (ret < 0)
+		ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno));
+
+	ksft_test_result(ret == 1 && LEN(vec) == (mem_size / page_size),
+			 "%s all pages must have PFNZERO set\n", __func__);
+
+	munmap(mem, mem_size);
+
+	/* Test with huge page if user_zero_page is set to 1 */
+	if (!detect_huge_zeropage()) {
+		ksft_test_result_skip("%s use_zero_page not supported or set to 1\n", __func__);
+		return;
+	}
+
+	mem_size = 2 * hpage_size;
+	mmap_mem = mmap(NULL, mem_size, PROT_READ | PROT_WRITE,
+			MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (mmap_mem == MAP_FAILED)
+		ksft_exit_fail_msg("error nomem\n");
+
+	/* We need a THP-aligned memory area. */
+	mem = (char *)(((uintptr_t)mmap_mem + hpage_size) & ~(hpage_size - 1));
+
+	ret = madvise(mem, hpage_size, MADV_HUGEPAGE);
+	if (!ret) {
+		char tmp = *mem;
+
+		asm volatile("" : "+r" (tmp));
+
+		ret = pagemap_ioctl(mem, hpage_size, &vec, 1, 0,
+				    0, PAGE_IS_PFNZERO, 0, 0, PAGE_IS_PFNZERO);
+		if (ret < 0)
+			ksft_exit_fail_msg("error %d %d %s\n", ret, errno, strerror(errno));
+
+		ksft_test_result(ret == 1 && LEN(vec) == (hpage_size / page_size),
+				 "%s all huge pages must have PFNZERO set\n", __func__);
+	} else {
+		ksft_test_result_skip("%s huge page not supported\n", __func__);
+	}
+
+	munmap(mmap_mem, mem_size);
+}
+
 int main(int __attribute__((unused)) argc, char *argv[])
 {
 	int shmid, buf_size, fd, i, ret;
@@ -1494,7 +1557,7 @@ int main(int __attribute__((unused)) argc, char *argv[])
 	if (init_uffd())
 		ksft_exit_pass();
 
-	ksft_set_plan(115);
+	ksft_set_plan(117);
 
 	page_size = getpagesize();
 	hpage_size = read_pmd_pagesize();
@@ -1669,6 +1732,9 @@ int main(int __attribute__((unused)) argc, char *argv[])
 	/* 16. Userfaultfd tests */
 	userfaultfd_tests();
 
+	/* 17. ZEROPFN tests */
+	zeropfn_tests();
+
 	close(pagemap_fd);
 	ksft_exit_pass();
 }