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selftests/mm: add PAGEMAP_SCAN guard region test

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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: Andrei Vagin <avagin@gmail.com>
Reviewed-by: Lorenzo 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Andrei Vagin
2025-03-24 06:53:28 +00:00
committed by Andrew Morton
parent 267bee0cd8
commit a9562fd03a
1 changed files with 57 additions and 0 deletions
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tools/testing/selftests/mm/guard-regions.c
+57
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@@ -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