// SPDX-License-Identifier: GPL-2.0-only
/*
* Stress userfaultfd syscall.
*
* Copyright (C) 2015 Red Hat, Inc.
*
* This test allocates two virtual areas and bounces the physical
* memory across the two virtual areas (from area_src to area_dst)
* using userfaultfd.
*
* There are three threads running per CPU:
*
* 1) one per-CPU thread takes a per-page pthread_mutex in a random
* page of the area_dst (while the physical page may still be in
* area_src), and increments a per-page counter in the same page,
* and checks its value against a verification region.
*
* 2) another per-CPU thread handles the userfaults generated by
* thread 1 above. userfaultfd blocking reads or poll() modes are
* exercised interleaved.
*
* 3) one last per-CPU thread transfers the memory in the background
* at maximum bandwidth (if not already transferred by thread
* 2). Each cpu thread takes cares of transferring a portion of the
* area.
*
* When all threads of type 3 completed the transfer, one bounce is
* complete. area_src and area_dst are then swapped. All threads are
* respawned and so the bounce is immediately restarted in the
* opposite direction.
*
* per-CPU threads 1 by triggering userfaults inside
* pthread_mutex_lock will also verify the atomicity of the memory
* transfer (UFFDIO_COPY).
*/
#include <asm-generic/unistd.h>
#include "uffd-common.h"
uint64_t features;
#define BOUNCE_RANDOM (1<<0)
#define BOUNCE_RACINGFAULTS (1<<1)
#define BOUNCE_VERIFY (1<<2)
#define BOUNCE_POLL (1<<3)
static int bounces;
/* exercise the test_uffdio_*_eexist every ALARM_INTERVAL_SECS */
#define ALARM_INTERVAL_SECS 10
static char *zeropage;
pthread_attr_t attr;
#define swap(a, b) \
do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
const char *examples =
"# Run anonymous memory test on 100MiB region with 99999 bounces:\n"
"./uffd-stress anon 100 99999\n\n"
"# Run share memory test on 1GiB region with 99 bounces:\n"
"./uffd-stress shmem 1000 99\n\n"
"# Run hugetlb memory test on 256MiB region with 50 bounces:\n"
"./uffd-stress hugetlb 256 50\n\n"
"# Run the same hugetlb test but using private file:\n"
"./uffd-stress hugetlb-private 256 50\n\n"
"# 10MiB-~6GiB 999 bounces anonymous test, "
"continue forever unless an error triggers\n"
"while ./uffd-stress anon $[RANDOM % 6000 + 10] 999; do true; done\n\n";
static void usage(void)
{
fprintf(stderr, "\nUsage: ./uffd-stress <test type> <MiB> <bounces>\n\n");
fprintf(stderr, "Supported <test type>: anon, hugetlb, "
"hugetlb-private, shmem, shmem-private\n\n");
fprintf(stderr, "Examples:\n\n");
fprintf(stderr, "%s", examples);
exit(1);
}
static void uffd_stats_reset(struct uffd_args *args, unsigned long n_cpus)
{
int i;
for (i = 0; i < n_cpus; i++) {
args[i].cpu = i;
args[i].apply_wp = test_uffdio_wp;
args[i].missing_faults = 0;
args[i].wp_faults = 0;
args[i].minor_faults = 0;
}
}
static void *locking_thread(void *arg)
{
unsigned long cpu = (unsigned long) arg;
unsigned long page_nr;
unsigned long long count;
if (!(bounces & BOUNCE_RANDOM)) {
page_nr = -bounces;
if (!(bounces & BOUNCE_RACINGFAULTS))
page_nr += cpu * nr_pages_per_cpu;
}
while (!finished) {
if (bounces & BOUNCE_RANDOM) {
if (getrandom(&page_nr, sizeof(page_nr), 0) != sizeof(page_nr))
err("getrandom failed");
} else
page_nr += 1;
page_nr %= nr_pages;
pthread_mutex_lock(area_mutex(area_dst, page_nr));
count = *area_count(area_dst, page_nr);
if (count != count_verify[page_nr])
err("page_nr %lu memory corruption %llu %llu",
page_nr, count, count_verify[page_nr]);
count++;
*area_count(area_dst, page_nr) = count_verify[page_nr] = count;
pthread_mutex_unlock(area_mutex(area_dst, page_nr));
}
return NULL;
}
static int copy_page_retry(int ufd, unsigned long offset)
{
return __copy_page(ufd, offset, true, test_uffdio_wp);
}
pthread_mutex_t uffd_read_mutex = PTHREAD_MUTEX_INITIALIZER;
static void *uffd_read_thread(void *arg)
{
struct uffd_args *args = (struct uffd_args *)arg;
struct uffd_msg msg;
pthread_mutex_unlock(&uffd_read_mutex);
/* from here cancellation is ok */
for (;;) {
if (uffd_read_msg(uffd, &msg))
continue;
uffd_handle_page_fault(&msg, args);
}
return NULL;
}
static void *background_thread(void *arg)
{
unsigned long cpu = (unsigned long) arg;
unsigned long page_nr, start_nr, mid_nr, end_nr;
start_nr = cpu * nr_pages_per_cpu;
end_nr = (cpu+1) * nr_pages_per_cpu;
mid_nr = (start_nr + end_nr) / 2;
/* Copy the first half of the pages */
for (page_nr = start_nr; page_nr < mid_nr; page_nr++)
copy_page_retry(uffd, page_nr * page_size);
/*
* If we need to test uffd-wp, set it up now. Then we'll have
* at least the first half of the pages mapped already which
* can be write-protected for testing
*/
if (test_uffdio_wp)
wp_range(uffd, (unsigned long)area_dst + start_nr * page_size,
nr_pages_per_cpu * page_size, true);
/*
* Continue the 2nd half of the page copying, handling write
* protection faults if any
*/
for (page_nr = mid_nr; page_nr < end_nr; page_nr++)
copy_page_retry(uffd, page_nr * page_size);
return NULL;
}
static int stress(struct uffd_args *args)
{
unsigned long cpu;
pthread_t locking_threads[nr_cpus];
pthread_t uffd_threads[nr_cpus];
pthread_t background_threads[nr_cpus];
finished = 0;
for (cpu = 0; cpu < nr_cpus; cpu++) {
if (pthread_create(&locking_threads[cpu], &attr,
locking_thread, (void *)cpu))
return 1;
if (bounces & BOUNCE_POLL) {
if (pthread_create(&uffd_threads[cpu], &attr, uffd_poll_thread, &args[cpu]))
err("uffd_poll_thread create");
} else {
if (pthread_create(&uffd_threads[cpu], &attr,
uffd_read_thread,
(void *)&args[cpu]))
return 1;
pthread_mutex_lock(&uffd_read_mutex);
}
if (pthread_create(&background_threads[cpu], &attr,
background_thread, (void *)cpu))
return 1;
}
for (cpu = 0; cpu < nr_cpus; cpu++)
if (pthread_join(background_threads[cpu], NULL))
return 1;
/*
* Be strict and immediately zap area_src, the whole area has
* been transferred already by the background treads. The
* area_src could then be faulted in a racy way by still
* running uffdio_threads reading zeropages after we zapped
* area_src (but they're guaranteed to get -EEXIST from
* UFFDIO_COPY without writing zero pages into area_dst
* because the background threads already completed).
*/
uffd_test_ops->release_pages(area_src);
finished = 1;
for (cpu = 0; cpu < nr_cpus; cpu++)
if (pthread_join(locking_threads[cpu], NULL))
return 1;
for (cpu = 0; cpu < nr_cpus; cpu++) {
char c;
if (bounces & BOUNCE_POLL) {
if (write(pipefd[cpu*2+1], &c, 1) != 1)
err("pipefd write error");
if (pthread_join(uffd_threads[cpu],
(void *)&args[cpu]))
return 1;
} else {
if (pthread_cancel(uffd_threads[cpu]))
return 1;
if (pthread_join(uffd_threads[cpu], NULL))
return 1;
}
}
return 0;
}
static int userfaultfd_stress(void)
{
void *area;
unsigned long nr;
struct uffd_args args[nr_cpus];
uint64_t mem_size = nr_pages * page_size;
int flags = 0;
memset(args, 0, sizeof(struct uffd_args) * nr_cpus);
if (features & UFFD_FEATURE_WP_UNPOPULATED && test_type == TEST_ANON)
flags = UFFD_FEATURE_WP_UNPOPULATED;
if (uffd_test_ctx_init(flags, NULL))
err("context init failed");
if (posix_memalign(&area, page_size, page_size))
err("out of memory");
zeropage = area;
bzero(zeropage, page_size);
pthread_mutex_lock(&uffd_read_mutex);
pthread_attr_init(&attr);
pthread_attr_setstacksize(&attr, 16*1024*1024);
while (bounces--) {
printf("bounces: %d, mode:", bounces);
if (bounces & BOUNCE_RANDOM)
printf(" rnd");
if (bounces & BOUNCE_RACINGFAULTS)
printf(" racing");
if (bounces & BOUNCE_VERIFY)
printf(" ver");
if (bounces & BOUNCE_POLL)
printf(" poll");
else
printf(" read");
printf(", ");
fflush(stdout);
if (bounces & BOUNCE_POLL)
fcntl(uffd, F_SETFL, uffd_flags | O_NONBLOCK);
else
fcntl(uffd, F_SETFL, uffd_flags & ~O_NONBLOCK);
/* register */
if (uffd_register(uffd, area_dst, mem_size,
true, test_uffdio_wp, false))
err("register failure");
if (area_dst_alias) {
if (uffd_register(uffd, area_dst_alias, mem_size,
true, test_uffdio_wp, false))
err("register failure alias");
}
/*
* The madvise done previously isn't enough: some
* uffd_thread could have read userfaults (one of
* those already resolved by the background thread)
* and it may be in the process of calling
* UFFDIO_COPY. UFFDIO_COPY will read the zapped
* area_src and it would map a zero page in it (of
* course such a UFFDIO_COPY is perfectly safe as it'd
* return -EEXIST). The problem comes at the next
* bounce though: that racing UFFDIO_COPY would
* generate zeropages in the area_src, so invalidating
* the previous MADV_DONTNEED. Without this additional
* MADV_DONTNEED those zeropages leftovers in the
* area_src would lead to -EEXIST failure during the
* next bounce, effectively leaving a zeropage in the
* area_dst.
*
* Try to comment this out madvise to see the memory
* corruption being caught pretty quick.
*
* khugepaged is also inhibited to collapse THP after
* MADV_DONTNEED only after the UFFDIO_REGISTER, so it's
* required to MADV_DONTNEED here.
*/
uffd_test_ops->release_pages(area_dst);
uffd_stats_reset(args, nr_cpus);
/* bounce pass */
if (stress(args)) {
uffd_test_ctx_clear();
return 1;
}
/* Clear all the write protections if there is any */
if (test_uffdio_wp)
wp_range(uffd, (unsigned long)area_dst,
nr_pages * page_size, false);
/* unregister */
if (uffd_unregister(uffd, area_dst, mem_size))
err("unregister failure");
if (area_dst_alias) {
if (uffd_unregister(uffd, area_dst_alias, mem_size))
err("unregister failure alias");
}
/* verification */
if (bounces & BOUNCE_VERIFY)
for (nr = 0; nr < nr_pages; nr++)
if (*area_count(area_dst, nr) != count_verify[nr])
err("error area_count %llu %llu %lu\n",
*area_count(area_src, nr),
count_verify[nr], nr);
/* prepare next bounce */
swap(area_src, area_dst);
swap(area_src_alias, area_dst_alias);
uffd_stats_report(args, nr_cpus);
}
uffd_test_ctx_clear();
return 0;
}
static void set_test_type(const char *type)
{
if (!strcmp(type, "anon")) {
test_type = TEST_ANON;
uffd_test_ops = &anon_uffd_test_ops;
} else if (!strcmp(type, "hugetlb")) {
test_type = TEST_HUGETLB;
uffd_test_ops = &hugetlb_uffd_test_ops;
map_shared = true;
} else if (!strcmp(type, "hugetlb-private")) {
test_type = TEST_HUGETLB;
uffd_test_ops = &hugetlb_uffd_test_ops;
} else if (!strcmp(type, "shmem")) {
map_shared = true;
test_type = TEST_SHMEM;
uffd_test_ops = &shmem_uffd_test_ops;
} else if (!strcmp(type, "shmem-private")) {
test_type = TEST_SHMEM;
uffd_test_ops = &shmem_uffd_test_ops;
}
}
static void parse_test_type_arg(const char *raw_type)
{
set_test_type(raw_type);
if (!test_type)
err("failed to parse test type argument: '%s'", raw_type);
if (test_type == TEST_HUGETLB)
page_size = default_huge_page_size();
else
page_size = sysconf(_SC_PAGE_SIZE);
if (!page_size)
err("Unable to determine page size");
if ((unsigned long) area_count(NULL, 0) + sizeof(unsigned long long) * 2
> page_size)
err("Impossible to run this test");
/*
* Whether we can test certain features depends not just on test type,
* but also on whether or not this particular kernel supports the
* feature.
*/
if (uffd_get_features(&features))
err("failed to get available features");
test_uffdio_wp = test_uffdio_wp &&
(features & UFFD_FEATURE_PAGEFAULT_FLAG_WP);
if (test_type != TEST_ANON && !(features & UFFD_FEATURE_WP_HUGETLBFS_SHMEM))
test_uffdio_wp = false;
close(uffd);
uffd = -1;
}
static void sigalrm(int sig)
{
if (sig != SIGALRM)
abort();
test_uffdio_copy_eexist = true;
alarm(ALARM_INTERVAL_SECS);
}
int main(int argc, char **argv)
{
size_t bytes;
if (argc < 4)
usage();
if (signal(SIGALRM, sigalrm) == SIG_ERR)
err("failed to arm SIGALRM");
alarm(ALARM_INTERVAL_SECS);
parse_test_type_arg(argv[1]);
bytes = atol(argv[2]) * 1024 * 1024;
if (test_type == TEST_HUGETLB &&
get_free_hugepages() < bytes / page_size) {
printf("skip: Skipping userfaultfd... not enough hugepages\n");
return KSFT_SKIP;
}
nr_cpus = sysconf(_SC_NPROCESSORS_ONLN);
nr_pages_per_cpu = bytes / page_size / nr_cpus;
if (!nr_pages_per_cpu) {
_err("invalid MiB");
usage();
}
bounces = atoi(argv[3]);
if (bounces <= 0) {
_err("invalid bounces");
usage();
}
nr_pages = nr_pages_per_cpu * nr_cpus;
printf("nr_pages: %lu, nr_pages_per_cpu: %lu\n",
nr_pages, nr_pages_per_cpu);
return userfaultfd_stress();
}
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