/*
* Linux UFFD-WP support
*
* Copyright Virtuozzo GmbH, 2020
*
* Authors:
* Andrey Gruzdev <andrey.gruzdev@virtuozzo.com>
*
* This work is licensed under the terms of the GNU GPL, version 2 or
* later. See the COPYING file in the top-level directory.
*/
#include "qemu/osdep.h"
#include "qemu/bitops.h"
#include "qemu/error-report.h"
#include "qemu/userfaultfd.h"
#include "trace.h"
#include <poll.h>
#include <sys/syscall.h>
#include <sys/ioctl.h>
/**
* uffd_query_features: query UFFD features
*
* Returns: 0 on success, negative value in case of an error
*
* @features: parameter to receive 'uffdio_api.features'
*/
int uffd_query_features(uint64_t *features)
{
int uffd_fd;
struct uffdio_api api_struct = { 0 };
int ret = -1;
uffd_fd = syscall(__NR_userfaultfd, O_CLOEXEC);
if (uffd_fd < 0) {
trace_uffd_query_features_nosys(errno);
return -1;
}
api_struct.api = UFFD_API;
api_struct.features = 0;
if (ioctl(uffd_fd, UFFDIO_API, &api_struct)) {
trace_uffd_query_features_api_failed(errno);
goto out;
}
*features = api_struct.features;
ret = 0;
out:
close(uffd_fd);
return ret;
}
/**
* uffd_create_fd: create UFFD file descriptor
*
* Returns non-negative file descriptor or negative value in case of an error
*
* @features: UFFD features to request
* @non_blocking: create UFFD file descriptor for non-blocking operation
*/
int uffd_create_fd(uint64_t features, bool non_blocking)
{
int uffd_fd;
int flags;
struct uffdio_api api_struct = { 0 };
uint64_t ioctl_mask = BIT(_UFFDIO_REGISTER) | BIT(_UFFDIO_UNREGISTER);
flags = O_CLOEXEC | (non_blocking ? O_NONBLOCK : 0);
uffd_fd = syscall(__NR_userfaultfd, flags);
if (uffd_fd < 0) {
trace_uffd_create_fd_nosys(errno);
return -1;
}
api_struct.api = UFFD_API;
api_struct.features = features;
if (ioctl(uffd_fd, UFFDIO_API, &api_struct)) {
trace_uffd_create_fd_api_failed(errno);
goto fail;
}
if ((api_struct.ioctls & ioctl_mask) != ioctl_mask) {
trace_uffd_create_fd_api_noioctl(ioctl_mask, api_struct.ioctls);
goto fail;
}
return uffd_fd;
fail:
close(uffd_fd);
return -1;
}
/**
* uffd_close_fd: close UFFD file descriptor
*
* @uffd_fd: UFFD file descriptor
*/
void uffd_close_fd(int uffd_fd)
{
assert(uffd_fd >= 0);
close(uffd_fd);
}
/**
* uffd_register_memory: register memory range via UFFD-IO
*
* Returns 0 in case of success, negative value in case of an error
*
* @uffd_fd: UFFD file descriptor
* @addr: base address of memory range
* @length: length of memory range
* @mode: UFFD register mode (UFFDIO_REGISTER_MODE_MISSING, ...)
* @ioctls: optional pointer to receive supported IOCTL mask
*/
int uffd_register_memory(int uffd_fd, void *addr, uint64_t length,
uint64_t mode, uint64_t *ioctls)
{
struct uffdio_register uffd_register;
uffd_register.range.start = (uintptr_t) addr;
uffd_register.range.len = length;
uffd_register.mode = mode;
if (ioctl(uffd_fd, UFFDIO_REGISTER, &uffd_register)) {
trace_uffd_register_memory_failed(addr, length, mode, errno);
return -1;
}
if (ioctls) {
*ioctls = uffd_register.ioctls;
}
return 0;
}
/**
* uffd_unregister_memory: un-register memory range with UFFD-IO
*
* Returns 0 in case of success, negative value in case of an error
*
* @uffd_fd: UFFD file descriptor
* @addr: base address of memory range
* @length: length of memory range
*/
int uffd_unregister_memory(int uffd_fd, void *addr, uint64_t length)
{
struct uffdio_range uffd_range;
uffd_range.start = (uintptr_t) addr;
uffd_range.len = length;
if (ioctl(uffd_fd, UFFDIO_UNREGISTER, &uffd_range)) {
trace_uffd_unregister_memory_failed(addr, length, errno);
return -1;
}
return 0;
}
/**
* uffd_change_protection: protect/un-protect memory range for writes via UFFD-IO
*
* Returns 0 on success, negative value in case of error
*
* @uffd_fd: UFFD file descriptor
* @addr: base address of memory range
* @length: length of memory range
* @wp: write-protect/unprotect
* @dont_wake: do not wake threads waiting on wr-protected page
*/
int uffd_change_protection(int uffd_fd, void *addr, uint64_t length,
bool wp, bool dont_wake)
{
struct uffdio_writeprotect uffd_writeprotect;
uffd_writeprotect.range.start = (uintptr_t) addr;
uffd_writeprotect.range.len = length;
if (!wp && dont_wake) {
/* DONTWAKE is meaningful only on protection release */
uffd_writeprotect.mode = UFFDIO_WRITEPROTECT_MODE_DONTWAKE;
} else {
uffd_writeprotect.mode = (wp ? UFFDIO_WRITEPROTECT_MODE_WP : 0);
}
if (ioctl(uffd_fd, UFFDIO_WRITEPROTECT, &uffd_writeprotect)) {
error_report("uffd_change_protection() failed: addr=%p len=%" PRIu64
" mode=%" PRIx64 " errno=%i", addr, length,
(uint64_t) uffd_writeprotect.mode, errno);
return -1;
}
return 0;
}
/**
* uffd_copy_page: copy range of pages to destination via UFFD-IO
*
* Copy range of source pages to the destination to resolve
* missing page fault somewhere in the destination range.
*
* Returns 0 on success, negative value in case of an error
*
* @uffd_fd: UFFD file descriptor
* @dst_addr: destination base address
* @src_addr: source base address
* @length: length of the range to copy
* @dont_wake: do not wake threads waiting on missing page
*/
int uffd_copy_page(int uffd_fd, void *dst_addr, void *src_addr,
uint64_t length, bool dont_wake)
{
struct uffdio_copy uffd_copy;
uffd_copy.dst = (uintptr_t) dst_addr;
uffd_copy.src = (uintptr_t) src_addr;
uffd_copy.len = length;
uffd_copy.mode = dont_wake ? UFFDIO_COPY_MODE_DONTWAKE : 0;
if (ioctl(uffd_fd, UFFDIO_COPY, &uffd_copy)) {
error_report("uffd_copy_page() failed: dst_addr=%p src_addr=%p length=%" PRIu64
" mode=%" PRIx64 " errno=%i", dst_addr, src_addr,
length, (uint64_t) uffd_copy.mode, errno);
return -1;
}
return 0;
}
/**
* uffd_zero_page: fill range of pages with zeroes via UFFD-IO
*
* Fill range pages with zeroes to resolve missing page fault within the range.
*
* Returns 0 on success, negative value in case of an error
*
* @uffd_fd: UFFD file descriptor
* @addr: base address
* @length: length of the range to fill with zeroes
* @dont_wake: do not wake threads waiting on missing page
*/
int uffd_zero_page(int uffd_fd, void *addr, uint64_t length, bool dont_wake)
{
struct uffdio_zeropage uffd_zeropage;
uffd_zeropage.range.start = (uintptr_t) addr;
uffd_zeropage.range.len = length;
uffd_zeropage.mode = dont_wake ? UFFDIO_ZEROPAGE_MODE_DONTWAKE : 0;
if (ioctl(uffd_fd, UFFDIO_ZEROPAGE, &uffd_zeropage)) {
error_report("uffd_zero_page() failed: addr=%p length=%" PRIu64
" mode=%" PRIx64 " errno=%i", addr, length,
(uint64_t) uffd_zeropage.mode, errno);
return -1;
}
return 0;
}
/**
* uffd_wakeup: wake up threads waiting on page UFFD-managed page fault resolution
*
* Wake up threads waiting on any page/pages from the designated range.
* The main use case is when during some period, page faults are resolved
* via UFFD-IO IOCTLs with MODE_DONTWAKE flag set, then after that all waits
* for the whole memory range are satisfied in a single call to uffd_wakeup().
*
* Returns 0 on success, negative value in case of an error
*
* @uffd_fd: UFFD file descriptor
* @addr: base address
* @length: length of the range
*/
int uffd_wakeup(int uffd_fd, void *addr, uint64_t length)
{
struct uffdio_range uffd_range;
uffd_range.start = (uintptr_t) addr;
uffd_range.len = length;
if (ioctl(uffd_fd, UFFDIO_WAKE, &uffd_range)) {
error_report("uffd_wakeup() failed: addr=%p length=%" PRIu64 " errno=%i",
addr, length, errno);
return -1;
}
return 0;
}
/**
* uffd_read_events: read pending UFFD events
*
* Returns number of fetched messages, 0 if non is available or
* negative value in case of an error
*
* @uffd_fd: UFFD file descriptor
* @msgs: pointer to message buffer
* @count: number of messages that can fit in the buffer
*/
int uffd_read_events(int uffd_fd, struct uffd_msg *msgs, int count)
{
ssize_t res;
do {
res = read(uffd_fd, msgs, count * sizeof(struct uffd_msg));
} while (res < 0 && errno == EINTR);
if ((res < 0 && errno == EAGAIN)) {
return 0;
}
if (res < 0) {
error_report("uffd_read_events() failed: errno=%i", errno);
return -1;
}
return (int) (res / sizeof(struct uffd_msg));
}
/**
* uffd_poll_events: poll UFFD file descriptor for read
*
* Returns true if events are available for read, false otherwise
*
* @uffd_fd: UFFD file descriptor
* @tmo: timeout value
*/
bool uffd_poll_events(int uffd_fd, int tmo)
{
int res;
struct pollfd poll_fd = { .fd = uffd_fd, .events = POLLIN, .revents = 0 };
do {
res = poll(&poll_fd, 1, tmo);
} while (res < 0 && errno == EINTR);
if (res == 0) {
return false;
}
if (res < 0) {
error_report("uffd_poll_events() failed: errno=%i", errno);
return false;
}
return (poll_fd.revents & POLLIN) != 0;
}
