Re: [PATCH v2 26/26] userfaultfd: selftests: add write-protect test

Mike Rapoport
2019-02-26T06:58:51Z

On Tue, Feb 12, 2019 at 10:56:32AM +0800, Peter Xu wrote:
> This patch adds uffd tests for write protection.
>
> Instead of introducing new tests for it, let's simply squashing uffd-wp
> tests into existing uffd-missing test cases. Changes are:
>
> (1) Bouncing tests
>
> We do the write-protection in two ways during the bouncing test:
>
> - By using UFFDIO_COPY_MODE_WP when resolving MISSING pages: then
> we'll make sure for each bounce process every single page will be
> at least fault twice: once for MISSING, once for WP.
>
> - By direct call UFFDIO_WRITEPROTECT on existing faulted memories:
> To further torture the explicit page protection procedures of
> uffd-wp, we split each bounce procedure into two halves (in the
> background thread): the first half will be MISSING+WP for each
> page as explained above. After the first half, we write protect
> the faulted region in the background thread to make sure at least
> half of the pages will be write protected again which is the first
> half to test the new UFFDIO_WRITEPROTECT call. Then we continue
> with the 2nd half, which will contain both MISSING and WP faulting
> tests for the 2nd half and WP-only faults from the 1st half.
>
> (2) Event/Signal test
>
> Mostly previous tests but will do MISSING+WP for each page. For
> sigbus-mode test we'll need to provide standalone path to handle the
> write protection faults.
>
> For all tests, do statistics as well for uffd-wp pages.
>
> Signed-off-by: Peter Xu <peterx@redhat.com>
> ---
> tools/testing/selftests/vm/userfaultfd.c | 154 ++++++++++++++++++-----
> 1 file changed, 126 insertions(+), 28 deletions(-)
>
> diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
> index e5d12c209e09..57b5ac02080a 100644
> --- a/tools/testing/selftests/vm/userfaultfd.c
> +++ b/tools/testing/selftests/vm/userfaultfd.c
> @@ -56,6 +56,7 @@
> #include <linux/userfaultfd.h>
> #include <setjmp.h>
> #include <stdbool.h>
> +#include <assert.h>
>
> #include "../kselftest.h"
>
> @@ -78,6 +79,8 @@ static int test_type;
> #define ALARM_INTERVAL_SECS 10
> static volatile bool test_uffdio_copy_eexist = true;
> static volatile bool test_uffdio_zeropage_eexist = true;
> +/* Whether to test uffd write-protection */
> +static bool test_uffdio_wp = false;
>
> static bool map_shared;
> static int huge_fd;
> @@ -92,6 +95,7 @@ pthread_attr_t attr;
> struct uffd_stats {
> int cpu;
> unsigned long missing_faults;
> + unsigned long wp_faults;
> };
>
> /* pthread_mutex_t starts at page offset 0 */
> @@ -141,9 +145,29 @@ static void uffd_stats_reset(struct uffd_stats *uffd_stats,
> for (i = 0; i < n_cpus; i++) {
> uffd_stats[i].cpu = i;
> uffd_stats[i].missing_faults = 0;
> + uffd_stats[i].wp_faults = 0;
> }
> }
>
> +static void uffd_stats_report(struct uffd_stats *stats, int n_cpus)
> +{
> + int i;
> + unsigned long long miss_total = 0, wp_total = 0;
> +
> + for (i = 0; i < n_cpus; i++) {
> + miss_total += stats[i].missing_faults;
> + wp_total += stats[i].wp_faults;
> + }
> +
> + printf("userfaults: %llu missing (", miss_total);
> + for (i = 0; i < n_cpus; i++)
> + printf("%lu+", stats[i].missing_faults);
> + printf("\b), %llu wp (", wp_total);
> + for (i = 0; i < n_cpus; i++)
> + printf("%lu+", stats[i].wp_faults);
> + printf("\b)\n");
> +}
> +
> static int anon_release_pages(char *rel_area)
> {
> int ret = 0;
> @@ -264,19 +288,15 @@ struct uffd_test_ops {
> void (*alias_mapping)(__u64 *start, size_t len, unsigned long offset);
> };
>
> -#define ANON_EXPECTED_IOCTLS ((1 << _UFFDIO_WAKE) | \
> - (1 << _UFFDIO_COPY) | \
> - (1 << _UFFDIO_ZEROPAGE))
> -
> static struct uffd_test_ops anon_uffd_test_ops = {
> - .expected_ioctls = ANON_EXPECTED_IOCTLS,
> + .expected_ioctls = UFFD_API_RANGE_IOCTLS,
> .allocate_area = anon_allocate_area,
> .release_pages = anon_release_pages,
> .alias_mapping = noop_alias_mapping,
> };
>
> static struct uffd_test_ops shmem_uffd_test_ops = {
> - .expected_ioctls = ANON_EXPECTED_IOCTLS,
> + .expected_ioctls = UFFD_API_RANGE_IOCTLS,

Isn't UFFD_API_RANGE_IOCTLS includes UFFDIO_WP which is not supported for
shmem?

> .allocate_area = shmem_allocate_area,
> .release_pages = shmem_release_pages,
> .alias_mapping = noop_alias_mapping,

...

--
Sincerely yours,
Mike.