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selftests/mm: add tests for RO pinning vs fork() 

Add a test suite (with 10 more sub-tests) to cover RO pinning against
fork() over uffd-wp.  It covers both:

  (1) Early CoW test in fork() when page pinned,
  (2) page unshare due to RO longterm pin.

They are:

  Testing wp-fork-pin on anon... done
  Testing wp-fork-pin on shmem... done
  Testing wp-fork-pin on shmem-private... done
  Testing wp-fork-pin on hugetlb... done
  Testing wp-fork-pin on hugetlb-private... done
  Testing wp-fork-pin-with-event on anon... done
  Testing wp-fork-pin-with-event on shmem... done
  Testing wp-fork-pin-with-event on shmem-private... done
  Testing wp-fork-pin-with-event on hugetlb... done
  Testing wp-fork-pin-with-event on hugetlb-private... done

CONFIG_GUP_TEST needed or they'll be skipped.

  Testing wp-fork-pin on anon... skipped [reason: Possibly CONFIG_GUP_TEST missing or unprivileged]

Note that the major test goal is on private memory, but no hurt to also run
all of them over shared because shared memory should work the same.

Link: https://lkml.kernel.org/r/20230417195317.898696-7-peterx@redhat.com
Signed-off-by: Peter Xu <peterx@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Mika Penttilä <mpenttil@redhat.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Peter Xu 2023-04-17 15:53:17 -04:00 committed by Andrew Morton
parent 71fc41eb98
commit 760aee0b71
1 changed files with 141 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

144
tools/testing/selftests/mm/uffd-unit-tests.c
View File

@ -7,6 +7,8 @@
#include "uffd-common.h"
#include "../../../../mm/gup_test.h"
#ifdef __NR_userfaultfd
/* The unit test doesn't need a large or random size, make it 32MB for now */
@ -247,7 +249,53 @@ static void *fork_event_consumer(void *data)
return NULL;
}
static int pagemap_test_fork(int uffd, bool with_event)
typedef struct {
int gup_fd;
bool pinned;
} pin_args;
/*
* Returns 0 if succeed, <0 for errors. pin_pages() needs to be paired
* with unpin_pages(). Currently it needs to be RO longterm pin to satisfy
* all needs of the test cases (e.g., trigger unshare, trigger fork() early
* CoW, etc.).
*/
static int pin_pages(pin_args *args, void *buffer, size_t size)
{
struct pin_longterm_test test = {
.addr = (uintptr_t)buffer,
.size = size,
/* Read-only pins */
.flags = 0,
};
if (args->pinned)
err("already pinned");
args->gup_fd = open("/sys/kernel/debug/gup_test", O_RDWR);
if (args->gup_fd < 0)
return -errno;
if (ioctl(args->gup_fd, PIN_LONGTERM_TEST_START, &test)) {
/* Even if gup_test existed, can be an old gup_test / kernel */
close(args->gup_fd);
return -errno;
}
args->pinned = true;
return 0;
}
static void unpin_pages(pin_args *args)
{
if (!args->pinned)
err("unpin without pin first");
if (ioctl(args->gup_fd, PIN_LONGTERM_TEST_STOP))
err("PIN_LONGTERM_TEST_STOP");
close(args->gup_fd);
args->pinned = false;
}
static int pagemap_test_fork(int uffd, bool with_event, bool test_pin)
{
fork_event_args args = { .parent_uffd = uffd, .child_uffd = -1 };
pthread_t thread;
@ -264,7 +312,17 @@ static int pagemap_test_fork(int uffd, bool with_event)
child = fork();
if (!child) {
/* Open the pagemap fd of the child itself */
pin_args args = {};
fd = pagemap_open();
if (test_pin && pin_pages(&args, area_dst, page_size))
/*
* Normally when reach here we have pinned in
* previous tests, so shouldn't fail anymore
*/
err("pin page failed in child");
value = pagemap_get_entry(fd, area_dst);
/*
* After fork(), we should handle uffd-wp bit differently:
@ -273,6 +331,8 @@ static int pagemap_test_fork(int uffd, bool with_event)
* (2) when without EVENT_FORK, it should be dropped
*/
pagemap_check_wp(value, with_event);
if (test_pin)
unpin_pages(&args);
/* Succeed */
exit(0);
}
@ -352,7 +412,7 @@ static void uffd_wp_fork_test_common(uffd_test_args_t *args,
wp_range(uffd, (uint64_t)area_dst, page_size, true);
value = pagemap_get_entry(pagemap_fd, area_dst);
pagemap_check_wp(value, true);
if (pagemap_test_fork(uffd, with_event)) {
if (pagemap_test_fork(uffd, with_event, false)) {
uffd_test_fail("Detected %s uffd-wp bit in child in present pte",
with_event ? "missing" : "stall");
goto out;
@ -383,7 +443,7 @@ static void uffd_wp_fork_test_common(uffd_test_args_t *args,
/* Uffd-wp should persist even swapped out */
value = pagemap_get_entry(pagemap_fd, area_dst);
pagemap_check_wp(value, true);
if (pagemap_test_fork(uffd, with_event)) {
if (pagemap_test_fork(uffd, with_event, false)) {
uffd_test_fail("Detected %s uffd-wp bit in child in zapped pte",
with_event ? "missing" : "stall");
goto out;
@ -415,6 +475,68 @@ static void uffd_wp_fork_with_event_test(uffd_test_args_t *args)
uffd_wp_fork_test_common(args, true);
}
static void uffd_wp_fork_pin_test_common(uffd_test_args_t *args,
bool with_event)
{
int pagemap_fd;
pin_args pin_args = {};
if (uffd_register(uffd, area_dst, page_size, false, true, false))
err("register failed");
pagemap_fd = pagemap_open();
/* Touch the page */
*area_dst = 1;
wp_range(uffd, (uint64_t)area_dst, page_size, true);
/*
* 1. First pin, then fork(). This tests fork() special path when
* doing early CoW if the page is private.
*/
if (pin_pages(&pin_args, area_dst, page_size)) {
uffd_test_skip("Possibly CONFIG_GUP_TEST missing "
"or unprivileged");
close(pagemap_fd);
uffd_unregister(uffd, area_dst, page_size);
return;
}
if (pagemap_test_fork(uffd, with_event, false)) {
uffd_test_fail("Detected %s uffd-wp bit in early CoW of fork()",
with_event ? "missing" : "stall");
unpin_pages(&pin_args);
goto out;
}
unpin_pages(&pin_args);
/*
* 2. First fork(), then pin (in the child, where test_pin==true).
* This tests COR, aka, page unsharing on private memories.
*/
if (pagemap_test_fork(uffd, with_event, true)) {
uffd_test_fail("Detected %s uffd-wp bit when RO pin",
with_event ? "missing" : "stall");
goto out;
}
uffd_test_pass();
out:
if (uffd_unregister(uffd, area_dst, page_size))
err("register failed");
close(pagemap_fd);
}
static void uffd_wp_fork_pin_test(uffd_test_args_t *args)
{
uffd_wp_fork_pin_test_common(args, false);
}
static void uffd_wp_fork_pin_with_event_test(uffd_test_args_t *args)
{
uffd_wp_fork_pin_test_common(args, true);
}
static void check_memory_contents(char *p)
{
unsigned long i, j;
@ -923,6 +1045,22 @@ uffd_test_case_t uffd_tests[] = {
/* when set, child process should inherit uffd-wp bits */
UFFD_FEATURE_EVENT_FORK,
},
{
.name = "wp-fork-pin",
.uffd_fn = uffd_wp_fork_pin_test,
.mem_targets = MEM_ALL,
.uffd_feature_required = UFFD_FEATURE_PAGEFAULT_FLAG_WP |
UFFD_FEATURE_WP_HUGETLBFS_SHMEM,
},
{
.name = "wp-fork-pin-with-event",
.uffd_fn = uffd_wp_fork_pin_with_event_test,
.mem_targets = MEM_ALL,
.uffd_feature_required = UFFD_FEATURE_PAGEFAULT_FLAG_WP |
UFFD_FEATURE_WP_HUGETLBFS_SHMEM |
/* when set, child process should inherit uffd-wp bits */
UFFD_FEATURE_EVENT_FORK,
},
{
.name = "wp-unpopulated",
.uffd_fn = uffd_wp_unpopulated_test,