Commit a9562fd0 authored by Andrei Vagin's avatar Andrei Vagin Committed by Andrew Morton
Browse files

selftests/mm: add PAGEMAP_SCAN guard region test 

Add a selftest to verify the PAGEMAP_SCAN ioctl correctly reports guard
regions using the newly introduced PAGE_IS_GUARD flag.

Link: https://lkml.kernel.org/r/20250324065328.107678-4-avagin@google.com


Signed-off-by: default avatarAndrei Vagin <avagin@gmail.com>
Reviewed-by: default avatarLorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 267bee0c

tools/testing/selftests/mm/guard-regions.c

+57 −0
Original line number Diff line number Diff line
@@ -8,6 +8,7 @@ 
#include <fcntl.h>

#include <linux/limits.h>

#include <linux/userfaultfd.h>

#include <linux/fs.h>

#include <setjmp.h>

#include <signal.h>

#include <stdbool.h>
@@ -2075,4 +2076,60 @@ TEST_F(guard_regions, pagemap) 
	ASSERT_EQ(munmap(ptr, 10 * page_size), 0);

}



/*

 * Assert that PAGEMAP_SCAN correctly reports guard region ranges.

 */

TEST_F(guard_regions, pagemap_scan)

{

	const unsigned long page_size = self->page_size;

	struct page_region pm_regs[10];

	struct pm_scan_arg pm_scan_args = {

		.size = sizeof(struct pm_scan_arg),

		.category_anyof_mask = PAGE_IS_GUARD,

		.return_mask = PAGE_IS_GUARD,

		.vec = (long)&pm_regs,

		.vec_len = ARRAY_SIZE(pm_regs),

	};

	int proc_fd, i;

	char *ptr;



	proc_fd = open("/proc/self/pagemap", O_RDONLY);

	ASSERT_NE(proc_fd, -1);



	ptr = mmap_(self, variant, NULL, 10 * page_size,

		    PROT_READ | PROT_WRITE, 0, 0);

	ASSERT_NE(ptr, MAP_FAILED);



	pm_scan_args.start = (long)ptr;

	pm_scan_args.end = (long)ptr + 10 * page_size;

	ASSERT_EQ(ioctl(proc_fd, PAGEMAP_SCAN, &pm_scan_args), 0);

	ASSERT_EQ(pm_scan_args.walk_end, (long)ptr + 10 * page_size);



	/* Install a guard region in every other page. */

	for (i = 0; i < 10; i += 2) {

		char *ptr_p = &ptr[i * page_size];



		ASSERT_EQ(syscall(__NR_madvise, ptr_p, page_size, MADV_GUARD_INSTALL), 0);

	}



	/*

	 * Assert ioctl() returns the count of located regions, where each

	 * region spans every other page within the range of 10 pages.

	 */

	ASSERT_EQ(ioctl(proc_fd, PAGEMAP_SCAN, &pm_scan_args), 5);

	ASSERT_EQ(pm_scan_args.walk_end, (long)ptr + 10 * page_size);



	/* Re-read from pagemap, and assert guard regions are detected. */

	for (i = 0; i < 5; i++) {

		long ptr_p = (long)&ptr[2 * i * page_size];



		ASSERT_EQ(pm_regs[i].start, ptr_p);

		ASSERT_EQ(pm_regs[i].end, ptr_p + page_size);

		ASSERT_EQ(pm_regs[i].categories, PAGE_IS_GUARD);

	}



	ASSERT_EQ(close(proc_fd), 0);

	ASSERT_EQ(munmap(ptr, 10 * page_size), 0);

}



TEST_HARNESS_MAIN