// SPDX-License-Identifier: GPL-2.0-only
/*
* Userfaultfd tests util functions
*
* Copyright (C) 2015-2023 Red Hat, Inc.
*/
#include "uffd-common.h"
#define BASE_PMD_ADDR ((void *)(1UL << 30))
volatile bool test_uffdio_copy_eexist = true;
unsigned long nr_cpus, nr_pages, nr_pages_per_cpu, page_size;
char *area_src, *area_src_alias, *area_dst, *area_dst_alias, *area_remap;
int uffd = -1, uffd_flags, finished, *pipefd, test_type;
bool map_shared;
bool test_uffdio_wp = true;
unsigned long long *count_verify;
uffd_test_ops_t *uffd_test_ops;
uffd_test_case_ops_t *uffd_test_case_ops;
atomic_bool ready_for_fork;
static int uffd_mem_fd_create(off_t mem_size, bool hugetlb)
{
unsigned int memfd_flags = 0;
int mem_fd;
if (hugetlb)
memfd_flags = MFD_HUGETLB;
mem_fd = memfd_create("uffd-test", memfd_flags);
if (mem_fd < 0)
err("memfd_create");
if (ftruncate(mem_fd, mem_size))
err("ftruncate");
if (fallocate(mem_fd,
FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE, 0,
mem_size))
err("fallocate");
return mem_fd;
}
static void anon_release_pages(char *rel_area)
{
if (madvise(rel_area, nr_pages * page_size, MADV_DONTNEED))
err("madvise(MADV_DONTNEED) failed");
}
static int anon_allocate_area(void **alloc_area, bool is_src)
{
*alloc_area = mmap(NULL, nr_pages * page_size, PROT_READ | PROT_WRITE,
MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
if (*alloc_area == MAP_FAILED) {
*alloc_area = NULL;
return -errno;
}
return 0;
}
static void noop_alias_mapping(__u64 *start, size_t len, unsigned long offset)
{
}
static void hugetlb_release_pages(char *rel_area)
{
if (!map_shared) {
if (madvise(rel_area, nr_pages * page_size, MADV_DONTNEED))
err("madvise(MADV_DONTNEED) failed");
} else {
if (madvise(rel_area, nr_pages * page_size, MADV_REMOVE))
err("madvise(MADV_REMOVE) failed");
}
}
static int hugetlb_allocate_area(void **alloc_area, bool is_src)
{
off_t size = nr_pages * page_size;
off_t offset = is_src ? 0 : size;
void *area_alias = NULL;
char **alloc_area_alias;
int mem_fd = uffd_mem_fd_create(size * 2, true);
*alloc_area = mmap(NULL, size, PROT_READ | PROT_WRITE,
(map_shared ? MAP_SHARED : MAP_PRIVATE) |
(is_src ? 0 : MAP_NORESERVE),
mem_fd, offset);
if (*alloc_area == MAP_FAILED) {
*alloc_area = NULL;
return -errno;
}
if (map_shared) {
area_alias = mmap(NULL, size, PROT_READ | PROT_WRITE,
MAP_SHARED, mem_fd, offset);
if (area_alias == MAP_FAILED)
return -errno;
}
if (is_src) {
alloc_area_alias = &area_src_alias;
} else {
alloc_area_alias = &area_dst_alias;
}
if (area_alias)
*alloc_area_alias = area_alias;
close(mem_fd);
return 0;
}
static void hugetlb_alias_mapping(__u64 *start, size_t len, unsigned long offset)
{
if (!map_shared)
return;
*start = (unsigned long) area_dst_alias + offset;
}
static void shmem_release_pages(char *rel_area)
{
if (madvise(rel_area, nr_pages * page_size, MADV_REMOVE))
err("madvise(MADV_REMOVE) failed");
}
static int shmem_allocate_area(void **alloc_area, bool is_src)
{
void *area_alias = NULL;
size_t bytes = nr_pages * page_size, hpage_size = read_pmd_pagesize();
unsigned long offset = is_src ? 0 : bytes;
char *p = NULL, *p_alias = NULL;
int mem_fd = uffd_mem_fd_create(bytes * 2, false);
/* TODO: clean this up. Use a static addr is ugly */
p = BASE_PMD_ADDR;
if (!is_src)
/* src map + alias + interleaved hpages */
p += 2 * (bytes + hpage_size);
p_alias = p;
p_alias += bytes;
p_alias += hpage_size; /* Prevent src/dst VMA merge */
*alloc_area = mmap(p, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
mem_fd, offset);
if (*alloc_area == MAP_FAILED) {
*alloc_area = NULL;
return -errno;
}
if (*alloc_area != p)
err("mmap of memfd failed at %p", p);
area_alias = mmap(p_alias, bytes, PROT_READ | PROT_WRITE, MAP_SHARED,
mem_fd, offset);
if (area_alias == MAP_FAILED) {
munmap(*alloc_area, bytes);
*alloc_area = NULL;
return -errno;
}
if (area_alias != p_alias)
err("mmap of anonymous memory failed at %p", p_alias);
if (is_src)
area_src_alias = area_alias;
else
area_dst_alias = area_alias;
close(mem_fd);
return 0;
}
static void shmem_alias_mapping(__u64 *start, size_t len, unsigned long offset)
{
*start = (unsigned long)area_dst_alias + offset;
}
static void shmem_check_pmd_mapping(void *p, int expect_nr_hpages)
{
if (!check_huge_shmem(area_dst_alias, expect_nr_hpages,
read_pmd_pagesize()))
err("Did not find expected %d number of hugepages",
expect_nr_hpages);
}
struct uffd_test_ops anon_uffd_test_ops = {
.allocate_area = anon_allocate_area,
.release_pages = anon_release_pages,
.alias_mapping = noop_alias_mapping,
.check_pmd_mapping = NULL,
};
struct uffd_test_ops shmem_uffd_test_ops = {
.allocate_area = shmem_allocate_area,
.release_pages = shmem_release_pages,
.alias_mapping = shmem_alias_mapping,
.check_pmd_mapping = shmem_check_pmd_mapping,
};
struct uffd_test_ops hugetlb_uffd_test_ops = {
.allocate_area = hugetlb_allocate_area,
.release_pages = hugetlb_release_pages,
.alias_mapping = hugetlb_alias_mapping,
.check_pmd_mapping = NULL,
};
void uffd_stats_report(struct uffd_args *args, int n_cpus)
{
int i;
unsigned long long miss_total = 0, wp_total = 0, minor_total = 0;
for (i = 0; i < n_cpus; i++) {
miss_total += args[i].missing_faults;
wp_total += args[i].wp_faults;
minor_total += args[i].minor_faults;
}
printf("userfaults: ");
if (miss_total) {
printf("%llu missing (", miss_total);
for (i = 0; i < n_cpus; i++)
printf("%lu+", args[i].missing_faults);
printf("\b) ");
}
if (wp_total) {
printf("%llu wp (", wp_total);
for (i = 0; i < n_cpus; i++)
printf("%lu+", args[i].wp_faults);
printf("\b) ");
}
if (minor_total) {
printf("%llu minor (", minor_total);
for (i = 0; i < n_cpus; i++)
printf("%lu+", args[i].minor_faults);
printf("\b)");
}
printf("\n");
}
int userfaultfd_open(uint64_t *features)
{
struct uffdio_api uffdio_api;
uffd = uffd_open(UFFD_FLAGS);
if (uffd < 0)
return -1;
uffd_flags = fcntl(uffd, F_GETFD, NULL);
uffdio_api.api = UFFD_API;
uffdio_api.features = *features;
if (ioctl(uffd, UFFDIO_API, &uffdio_api))
/* Probably lack of CAP_PTRACE? */
return -1;
if (uffdio_api.api != UFFD_API)
err("UFFDIO_API error: %" PRIu64, (uint64_t)uffdio_api.api);
*features = uffdio_api.features;
return 0;
}
static inline void munmap_area(void **area)
{
if (*area)
if (munmap(*area, nr_pages * page_size))
err("munmap");
*area = NULL;
}
void uffd_test_ctx_clear(void)
{
size_t i;
if (pipefd) {
for (i = 0; i < nr_cpus * 2; ++i) {
if (close(pipefd[i]))
err("close pipefd");
}
free(pipefd);
pipefd = NULL;
}
if (count_verify) {
free(count_verify);
count_verify = NULL;
}
if (uffd != -1) {
if (close(uffd))
err("close uffd");
uffd = -1;
}
munmap_area((void **)&area_src);
munmap_area((void **)&area_src_alias);
munmap_area((void **)&area_dst);
munmap_area((void **)&area_dst_alias);
munmap_area((void **)&area_remap);
}
int uffd_test_ctx_init(uint64_t features, const char **errmsg)
{
unsigned long nr, cpu;
int ret;
if (uffd_test_case_ops && uffd_test_case_ops->pre_alloc) {
ret = uffd_test_case_ops->pre_alloc(errmsg);
if (ret)
return ret;
}
ret = uffd_test_ops->allocate_area((void **)&area_src, true);
ret |= uffd_test_ops->allocate_area((void **)&area_dst, false);
if (ret) {
if (errmsg)
*errmsg = "memory allocation failed";
return ret;
}
if (uffd_test_case_ops && uffd_test_case_ops->post_alloc) {
ret = uffd_test_case_ops->post_alloc(errmsg);
if (ret)
return ret;
}
ret = userfaultfd_open(&features);
if (ret) {
if (errmsg)
*errmsg = "possible lack of priviledge";
return ret;
}
count_verify = malloc(nr_pages * sizeof(unsigned long long));
if (!count_verify)
err("count_verify");
for (nr = 0; nr < nr_pages; nr++) {
*area_mutex(area_src, nr) =
(pthread_mutex_t)PTHREAD_MUTEX_INITIALIZER;
count_verify[nr] = *area_count(area_src, nr) = 1;
/*
* In the transition between 255 to 256, powerpc will
* read out of order in my_bcmp and see both bytes as
* zero, so leave a placeholder below always non-zero
* after the count, to avoid my_bcmp to trigger false
* positives.
*/
*(area_count(area_src, nr) + 1) = 1;
}
/*
* After initialization of area_src, we must explicitly release pages
* for area_dst to make sure it's fully empty. Otherwise we could have
* some area_dst pages be errornously initialized with zero pages,
* hence we could hit memory corruption later in the test.
*
* One example is when THP is globally enabled, above allocate_area()
* calls could have the two areas merged into a single VMA (as they
* will have the same VMA flags so they're mergeable). When we
* initialize the area_src above, it's possible that some part of
* area_dst could have been faulted in via one huge THP that will be
* shared between area_src and area_dst. It could cause some of the
* area_dst won't be trapped by missing userfaults.
*
* This release_pages() will guarantee even if that happened, we'll
* proactively split the thp and drop any accidentally initialized
* pages within area_dst.
*/
uffd_test_ops->release_pages(area_dst);
pipefd = malloc(sizeof(int) * nr_cpus * 2);
if (!pipefd)
err("pipefd");
for (cpu = 0; cpu < nr_cpus; cpu++)
if (pipe2(&pipefd[cpu * 2], O_CLOEXEC | O_NONBLOCK))
err("pipe");
return 0;
}
void wp_range(int ufd, __u64 start, __u64 len, bool wp)
{
struct uffdio_writeprotect prms;
/* Write protection page faults */
prms.range.start = start;
prms.range.len = len;
/* Undo write-protect, do wakeup after that */
prms.mode = wp ? UFFDIO_WRITEPROTECT_MODE_WP : 0;
if (ioctl(ufd, UFFDIO_WRITEPROTECT, &prms))
err("clear WP failed: address=0x%"PRIx64, (uint64_t)start);
}
static void continue_range(int ufd, __u64 start, __u64 len, bool wp)
{
struct uffdio_continue req;
int ret;
req.range.start = start;
req.range.len = len;
req.mode = 0;
if (wp)
req.mode |= UFFDIO_CONTINUE_MODE_WP;
if (ioctl(ufd, UFFDIO_CONTINUE, &req))
err("UFFDIO_CONTINUE failed for address 0x%" PRIx64,
(uint64_t)start);
/*
* Error handling within the kernel for continue is subtly different
* from copy or zeropage, so it may be a source of bugs. Trigger an
* error (-EEXIST) on purpose, to verify doing so doesn't cause a BUG.
*/
req.mapped = 0;
ret = ioctl(ufd, UFFDIO_CONTINUE, &req);
if (ret >= 0 || req.mapped != -EEXIST)
err("failed to exercise UFFDIO_CONTINUE error handling, ret=%d, mapped=%" PRId64,
ret, (int64_t) req.mapped);
}
int uffd_read_msg(int ufd, struct uffd_msg *msg)
{
int ret = read(uffd, msg, sizeof(*msg));
if (ret != sizeof(*msg)) {
if (ret < 0) {
if (errno == EAGAIN || errno == EINTR)
return 1;
err("blocking read error");
} else {
err("short read");
}
}
return 0;
}
void uffd_handle_page_fault(struct uffd_msg *msg, struct uffd_args *args)
{
unsigned long offset;
if (msg->event != UFFD_EVENT_PAGEFAULT)
err("unexpected msg event %u", msg->event);
if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WP) {
/* Write protect page faults */
wp_range(uffd, msg->arg.pagefault.address, page_size, false);
args->wp_faults++;
} else if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_MINOR) {
uint8_t *area;
int b;
/*
* Minor page faults
*
* To prove we can modify the original range for testing
* purposes, we're going to bit flip this range before
* continuing.
*
* Note that this requires all minor page fault tests operate on
* area_dst (non-UFFD-registered) and area_dst_alias
* (UFFD-registered).
*/
area = (uint8_t *)(area_dst +
((char *)msg->arg.pagefault.address -
area_dst_alias));
for (b = 0; b < page_size; ++b)
area[b] = ~area[b];
continue_range(uffd, msg->arg.pagefault.address, page_size,
args->apply_wp);
args->minor_faults++;
} else {
/*
* Missing page faults.
*
* Here we force a write check for each of the missing mode
* faults. It's guaranteed because the only threads that
* will trigger uffd faults are the locking threads, and
* their first instruction to touch the missing page will
* always be pthread_mutex_lock().
*
* Note that here we relied on an NPTL glibc impl detail to
* always read the lock type at the entry of the lock op
* (pthread_mutex_t.__data.__type, offset 0x10) before
* doing any locking operations to guarantee that. It's
* actually not good to rely on this impl detail because
* logically a pthread-compatible lib can implement the
* locks without types and we can fail when linking with
* them. However since we used to find bugs with this
* strict check we still keep it around. Hopefully this
* could be a good hint when it fails again. If one day
* it'll break on some other impl of glibc we'll revisit.
*/
if (msg->arg.pagefault.flags & UFFD_PAGEFAULT_FLAG_WRITE)
err("unexpected write fault");
offset = (char *)(unsigned long)msg->arg.pagefault.address - area_dst;
offset &= ~(page_size-1);
if (copy_page(uffd, offset, args->apply_wp))
args->missing_faults++;
}
}
void *uffd_poll_thread(void *arg)
{
struct uffd_args *args = (struct uffd_args *)arg;
unsigned long cpu = args->cpu;
struct pollfd pollfd[2];
struct uffd_msg msg;
struct uffdio_register uffd_reg;
int ret;
char tmp_chr;
if (!args->handle_fault)
args->handle_fault = uffd_handle_page_fault;
pollfd[0].fd = uffd;
pollfd[0].events = POLLIN;
pollfd[1].fd = pipefd[cpu*2];
pollfd[1].events = POLLIN;
ready_for_fork = true;
for (;;) {
ret = poll(pollfd, 2, -1);
if (ret <= 0) {
if (errno == EINTR || errno == EAGAIN)
continue;
err("poll error: %d", ret);
}
if (pollfd[1].revents) {
if (!(pollfd[1].revents & POLLIN))
err("pollfd[1].revents %d", pollfd[1].revents);
if (read(pollfd[1].fd, &tmp_chr, 1) != 1)
err("read pipefd error");
break;
}
if (!(pollfd[0].revents & POLLIN))
err("pollfd[0].revents %d", pollfd[0].revents);
if (uffd_read_msg(uffd, &msg))
continue;
switch (msg.event) {
default:
err("unexpected msg event %u\n", msg.event);
break;
case UFFD_EVENT_PAGEFAULT:
args->handle_fault(&msg, args);
break;
case UFFD_EVENT_FORK:
close(uffd);
uffd = msg.arg.fork.ufd;
pollfd[0].fd = uffd;
break;
case UFFD_EVENT_REMOVE:
uffd_reg.range.start = msg.arg.remove.start;
uffd_reg.range.len = msg.arg.remove.end -
msg.arg.remove.start;
if (ioctl(uffd, UFFDIO_UNREGISTER, &uffd_reg.range))
err("remove failure");
break;
case UFFD_EVENT_REMAP:
area_remap = area_dst; /* save for later unmap */
area_dst = (char *)(unsigned long)msg.arg.remap.to;
break;
}
}
return NULL;
}
static void retry_copy_page(int ufd, struct uffdio_copy *uffdio_copy,
unsigned long offset)
{
uffd_test_ops->alias_mapping(&uffdio_copy->dst,
uffdio_copy->len,
offset);
if (ioctl(ufd, UFFDIO_COPY, uffdio_copy)) {
/* real retval in ufdio_copy.copy */
if (uffdio_copy->copy != -EEXIST)
err("UFFDIO_COPY retry error: %"PRId64,
(int64_t)uffdio_copy->copy);
} else {
err("UFFDIO_COPY retry unexpected: %"PRId64,
(int64_t)uffdio_copy->copy);
}
}
static void wake_range(int ufd, unsigned long addr, unsigned long len)
{
struct uffdio_range uffdio_wake;
uffdio_wake.start = addr;
uffdio_wake.len = len;
if (ioctl(ufd, UFFDIO_WAKE, &uffdio_wake))
fprintf(stderr, "error waking %lu\n",
addr), exit(1);
}
int __copy_page(int ufd, unsigned long offset, bool retry, bool wp)
{
struct uffdio_copy uffdio_copy;
if (offset >= nr_pages * page_size)
err("unexpected offset %lu\n", offset);
uffdio_copy.dst = (unsigned long) area_dst + offset;
uffdio_copy.src = (unsigned long) area_src + offset;
uffdio_copy.len = page_size;
if (wp)
uffdio_copy.mode = UFFDIO_COPY_MODE_WP;
else
uffdio_copy.mode = 0;
uffdio_copy.copy = 0;
if (ioctl(ufd, UFFDIO_COPY, &uffdio_copy)) {
/* real retval in ufdio_copy.copy */
if (uffdio_copy.copy != -EEXIST)
err("UFFDIO_COPY error: %"PRId64,
(int64_t)uffdio_copy.copy);
wake_range(ufd, uffdio_copy.dst, page_size);
} else if (uffdio_copy.copy != page_size) {
err("UFFDIO_COPY error: %"PRId64, (int64_t)uffdio_copy.copy);
} else {
if (test_uffdio_copy_eexist && retry) {
test_uffdio_copy_eexist = false;
retry_copy_page(ufd, &uffdio_copy, offset);
}
return 1;
}
return 0;
}
int copy_page(int ufd, unsigned long offset, bool wp)
{
return __copy_page(ufd, offset, false, wp);
}
int move_page(int ufd, unsigned long offset, unsigned long len)
{
struct uffdio_move uffdio_move;
if (offset + len > nr_pages * page_size)
err("unexpected offset %lu and length %lu\n", offset, len);
uffdio_move.dst = (unsigned long) area_dst + offset;
uffdio_move.src = (unsigned long) area_src + offset;
uffdio_move.len = len;
uffdio_move.mode = UFFDIO_MOVE_MODE_ALLOW_SRC_HOLES;
uffdio_move.move = 0;
if (ioctl(ufd, UFFDIO_MOVE, &uffdio_move)) {
/* real retval in uffdio_move.move */
if (uffdio_move.move != -EEXIST)
err("UFFDIO_MOVE error: %"PRId64,
(int64_t)uffdio_move.move);
wake_range(ufd, uffdio_move.dst, len);
} else if (uffdio_move.move != len) {
err("UFFDIO_MOVE error: %"PRId64, (int64_t)uffdio_move.move);
} else
return 1;
return 0;
}
int uffd_open_dev(unsigned int flags)
{
int fd, uffd;
fd = open("/dev/userfaultfd", O_RDWR | O_CLOEXEC);
if (fd < 0)
return fd;
uffd = ioctl(fd, USERFAULTFD_IOC_NEW, flags);
close(fd);
return uffd;
}
int uffd_open_sys(unsigned int flags)
{
return syscall(__NR_userfaultfd, flags);
}
int uffd_open(unsigned int flags)
{
int uffd = uffd_open_sys(flags);
if (uffd < 0)
uffd = uffd_open_dev(flags);
return uffd;
}
int uffd_get_features(uint64_t *features)
{
struct uffdio_api uffdio_api = { .api = UFFD_API, .features = 0 };
/*
* This should by default work in most kernels; the feature list
* will be the same no matter what we pass in here.
*/
int fd = uffd_open(UFFD_USER_MODE_ONLY);
if (fd < 0)
/* Maybe the kernel is older than user-only mode? */
fd = uffd_open(0);
if (fd < 0)
return fd;
if (ioctl(fd, UFFDIO_API, &uffdio_api)) {
close(fd);
return -errno;
}
*features = uffdio_api.features;
close(fd);
return 0;
}
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