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Subject[PATCH 3/3] userfaultfd: selftest: add test for FORK, MADVDONTNEED and REMAP events
Date
Add test for userfaultfd events used in non-cooperative scenario when the
process that monitors the userfaultfd and handles user faults is not the
same process that causes the page faults.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
---
tools/testing/selftests/vm/userfaultfd.c | 174 ++++++++++++++++++++++++++++---
1 file changed, 162 insertions(+), 12 deletions(-)

diff --git a/tools/testing/selftests/vm/userfaultfd.c b/tools/testing/selftests/vm/userfaultfd.c
index c79c372..fed2119 100644
--- a/tools/testing/selftests/vm/userfaultfd.c
+++ b/tools/testing/selftests/vm/userfaultfd.c
@@ -63,6 +63,7 @@
#include <sys/mman.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
+#include <sys/wait.h>
#include <pthread.h>
#include <linux/userfaultfd.h>

@@ -347,6 +348,7 @@ static void *uffd_poll_thread(void *arg)
unsigned long cpu = (unsigned long) arg;
struct pollfd pollfd[2];
struct uffd_msg msg;
+ struct uffdio_register uffd_reg;
int ret;
unsigned long offset;
char tmp_chr;
@@ -378,16 +380,35 @@ static void *uffd_poll_thread(void *arg)
continue;
perror("nonblocking read error"), exit(1);
}
- if (msg.event != UFFD_EVENT_PAGEFAULT)
+ switch (msg.event) {
+ default:
fprintf(stderr, "unexpected msg event %u\n",
msg.event), exit(1);
- if (msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
- fprintf(stderr, "unexpected write fault\n"), exit(1);
- offset = (char *)(unsigned long)msg.arg.pagefault.address -
- area_dst;
- offset &= ~(page_size-1);
- if (copy_page(uffd, offset))
- userfaults++;
+ break;
+ case UFFD_EVENT_PAGEFAULT:
+ if (msg.arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
+ fprintf(stderr, "unexpected write fault\n"), exit(1);
+ offset = (char *)(unsigned long)msg.arg.pagefault.address -
+ area_dst;
+ offset &= ~(page_size-1);
+ if (copy_page(uffd, offset))
+ userfaults++;
+ break;
+ case UFFD_EVENT_FORK:
+ uffd = msg.arg.fork.ufd;
+ pollfd[0].fd = uffd;
+ break;
+ case UFFD_EVENT_MADVDONTNEED:
+ uffd_reg.range.start = msg.arg.madv_dn.start;
+ uffd_reg.range.len = msg.arg.madv_dn.end -
+ msg.arg.madv_dn.start;
+ if (ioctl(uffd, UFFDIO_UNREGISTER, &uffd_reg.range))
+ fprintf(stderr, "madv_dn failure\n"), exit(1);
+ break;
+ case UFFD_EVENT_REMAP:
+ area_dst = (char *)(unsigned long)msg.arg.remap.to;
+ break;
+ }
}
return (void *)userfaults;
}
@@ -512,7 +533,7 @@ static int stress(unsigned long *userfaults)
return 0;
}

-static int userfaultfd_open(void)
+static int userfaultfd_open(int features)
{
struct uffdio_api uffdio_api;

@@ -525,7 +546,7 @@ static int userfaultfd_open(void)
uffd_flags = fcntl(uffd, F_GETFD, NULL);

uffdio_api.api = UFFD_API;
- uffdio_api.features = 0;
+ uffdio_api.features = features;
if (ioctl(uffd, UFFDIO_API, &uffdio_api)) {
fprintf(stderr, "UFFDIO_API\n");
return 1;
@@ -538,6 +559,131 @@ static int userfaultfd_open(void)
return 0;
}

+/*
+ * For non-cooperative userfaultfd test we fork() a process that will
+ * generate pagefaults, will mremap the area monitored by the
+ * userfaultfd and at last this process will release the monitored
+ * area.
+ * For the anonymous and shared memory the area is divided into two
+ * parts, the first part is accessed before mremap, and the second
+ * part is accessed after mremap. Since hugetlbfs does not support
+ * mremap, the entire monitored area is accessed in a single pass for
+ * HUGETLB_TEST.
+ * The release of the pages currently generates event only for
+ * anonymous memory (UFFD_EVENT_MADVDONTNEED), hence it is not checked
+ * for hugetlb and shmem.
+ */
+static int faulting_process(void)
+{
+ unsigned long nr;
+ unsigned long long count;
+
+#ifndef HUGETLB_TEST
+ unsigned long split_nr_pages = (nr_pages + 1) / 2;
+#else
+ unsigned long split_nr_pages = nr_pages;
+#endif
+
+ for (nr = 0; nr < split_nr_pages; nr++) {
+ count = *area_count(area_dst, nr);
+ if (count != count_verify[nr]) {
+ fprintf(stderr,
+ "nr %lu memory corruption %Lu %Lu\n",
+ nr, count,
+ count_verify[nr]), exit(1);
+ }
+ }
+
+#ifndef HUGETLB_TEST
+ area_dst = mremap(area_dst, nr_pages * page_size, nr_pages * page_size,
+ MREMAP_MAYMOVE | MREMAP_FIXED, area_src);
+ if (area_dst == MAP_FAILED)
+ perror("mremap"), exit(1);
+
+ for (; nr < nr_pages; nr++) {
+ count = *area_count(area_dst, nr);
+ if (count != count_verify[nr]) {
+ fprintf(stderr,
+ "nr %lu memory corruption %Lu %Lu\n",
+ nr, count,
+ count_verify[nr]), exit(1);
+ }
+ }
+
+#ifndef SHMEM_TEST
+ if (release_pages(area_dst))
+ return 1;
+
+ for (nr = 0; nr < nr_pages; nr++) {
+ if (my_bcmp(area_dst + nr * page_size, zeropage, page_size))
+ fprintf(stderr, "nr %lu is not zero\n", nr), exit(1);
+ }
+#endif /* SHMEM_TEST */
+
+#endif /* HUGETLB_TEST */
+
+ return 0;
+}
+
+static int userfaultfd_events_test(void)
+{
+ struct uffdio_register uffdio_register;
+ unsigned long expected_ioctls;
+ unsigned long userfaults;
+ pthread_t uffd_mon;
+ int err, features;
+ pid_t pid;
+ char c;
+
+ printf("testing events (fork, remap, madv_dn): ");
+ fflush(stdout);
+
+ if (release_pages(area_dst))
+ return 1;
+
+ features = UFFD_FEATURE_EVENT_FORK | UFFD_FEATURE_EVENT_REMAP |
+ UFFD_FEATURE_EVENT_MADVDONTNEED;
+ if (userfaultfd_open(features) < 0)
+ return 1;
+ fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
+
+ uffdio_register.range.start = (unsigned long) area_dst;
+ uffdio_register.range.len = nr_pages * page_size;
+ uffdio_register.mode = UFFDIO_REGISTER_MODE_MISSING;
+ if (ioctl(uffd, UFFDIO_REGISTER, &uffdio_register))
+ fprintf(stderr, "register failure\n"), exit(1);
+
+ expected_ioctls = EXPECTED_IOCTLS;
+ if ((uffdio_register.ioctls & expected_ioctls) !=
+ expected_ioctls)
+ fprintf(stderr,
+ "unexpected missing ioctl for anon memory\n"),
+ exit(1);
+
+ if (pthread_create(&uffd_mon, &attr, uffd_poll_thread, NULL))
+ perror("uffd_poll_thread create"), exit(1);
+
+ pid = fork();
+ if (pid < 0)
+ perror("fork"), exit(1);
+
+ if (!pid)
+ return faulting_process();
+
+ waitpid(pid, &err, 0);
+ if (err)
+ fprintf(stderr, "faulting process failed\n"), exit(1);
+
+ if (write(pipefd[1], &c, sizeof(c)) != sizeof(c))
+ perror("pipe write"), exit(1);
+ if (pthread_join(uffd_mon, (void **)&userfaults))
+ return 1;
+
+ printf("userfaults: %ld\n", userfaults);
+
+ return userfaults != nr_pages;
+}
+
static int userfaultfd_stress(void)
{
void *area;
@@ -555,7 +701,7 @@ static int userfaultfd_stress(void)
if (!area_dst)
return 1;

- if (userfaultfd_open() < 0)
+ if (userfaultfd_open(0) < 0)
return 1;

count_verify = malloc(nr_pages * sizeof(unsigned long long));
@@ -702,7 +848,11 @@ static int userfaultfd_stress(void)
printf("\n");
}

- return err;
+ if (err)
+ return err;
+
+ close(uffd);
+ return userfaultfd_events_test();
}

#ifndef HUGETLB_TEST
--
1.9.1
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