On 8/6/26 20:17, Audra Mitchell wrote:
> On architectures with separate user address space, such as s390 or
> those without an MMU, the soft-dirty kselftest may fail when checking
> to see if the feature is supported.
>
> # --------------------
> # running ./soft-dirty
> # --------------------
> # TAP version 13
> # 1..15
> # Bail out! PAGEMAP_SCAN succeeded unexpectedly
> # # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0
> # [FAIL]
> not ok 1 soft-dirty # exit=1
> # SUMMARY: PASS=0 SKIP=0 FAIL=1
>
> The soft-dirty test will initate an ioctl with the PAGEMAP_SCAN flag with
> an invalid address for the page_region. This is done intentionally to
> have the ioctl return with an expected EFAULT and with the correct
> categories returned.
>
> However, on architectures with separate user address space, such as s390 or
> those without an MMU, the call to __access_ok (used to validate the
> variables provided with the ioctl) will always return true and we will not
> fail as expected.
>
> if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) ||
> !IS_ENABLED(CONFIG_MMU))
> return true;
>
> Let's simplify the check for PAGEMAP_SCAN and provide a valid page_region
> address so that we get a non-errno return if it is supported.
>
> Fixes: 600bca580579 ("selftests/mm: check that PAGEMAP_SCAN returns correct
> categories")
>
> Signed-off-by: Audra Mitchell <[email protected]>
> ---
> tools/testing/selftests/mm/vm_util.c | 23 ++++++++++++++---------
> 1 file changed, 14 insertions(+), 9 deletions(-)
>
> diff --git a/tools/testing/selftests/mm/vm_util.c
> b/tools/testing/selftests/mm/vm_util.c
> index 6b65bd0a1e0b..4a8e339a7403 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -66,20 +66,25 @@ static uint64_t pagemap_scan_get_categories(int fd, char
> *start)
> }
>
> /* `start` is any valid address. */
Acked to dropping that.
> -static bool pagemap_scan_supported(int fd, char *start)
> +static bool pagemap_scan_supported(int fd)
> {
> + const size_t pagesize = getpagesize();
> static int supported = -1;
> - int ret;
> + struct page_region r;
> + void *test_area;
>
> if (supported != -1)
> return supported;
>
> - /* Provide an invalid address in order to trigger EFAULT. */
> - ret = __pagemap_scan_get_categories(fd, start, (struct page_region *)
> ~0UL);
> - if (ret == 0)
> - ksft_exit_fail_msg("PAGEMAP_SCAN succeeded unexpectedly\n");
> -
> - supported = errno == EFAULT;
> + test_area = mmap(0, pagesize, PROT_READ | PROT_WRITE,
> + MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
> + if (test_area == MAP_FAILED) {
> + ksft_print_msg("WARN: mmap() failed: %s\n", strerror(errno));
> + supported = 0;
You can really just
ksft_exit_fail_msg("mmap() failed\n");
here, because this is one of the things that really should never fail.
Which leaves us with:
test_area = mmap(0, pagesize, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
if (test_area == MAP_FAILED)
ksft_print_msg("WARN: mmap() failed: %s\n", strerror(errno));
supported = __pagemap_scan_get_categories(fd, test_area, &r) >= 0;
munmap(test_area, pagesize);
--
Cheers,
David
