On Mon, Mar 24, 2025 at 06:53:28AM +0000, Andrei Vagin wrote:
> From: Andrei Vagin <avagin@xxxxxxxxx>
>
> Add a selftest to verify the PAGEMAP_SCAN ioctl correctly reports guard
> regions using the newly introduced PAGE_IS_GUARD flag.
>
> Signed-off-by: Andrei Vagin <avagin@xxxxxxxxx>
Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>
> ---
> tools/testing/selftests/mm/guard-regions.c | 57 ++++++++++++++++++++++
> 1 file changed, 57 insertions(+)
>
> diff --git a/tools/testing/selftests/mm/guard-regions.c b/tools/testing/selftests/mm/guard-regions.c
> index 0c7183e8b661..c99f3da8bfb7 100644
> --- a/tools/testing/selftests/mm/guard-regions.c
> +++ b/tools/testing/selftests/mm/guard-regions.c
> @@ -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>
> @@ -2079,4 +2080,60 @@ 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
> --
> 2.49.0.395.g12beb8f557-goog
>
