qemu/io/channel-command.c
Marc-André Lureau ec5b6c9c5d io/command: implement support for win32
The initial implementation was changing the pipe state created by GLib
to PIPE_NOWAIT, but it turns out it doesn't work (read/write returns an
error). Since reading may return less than the requested amount, it
seems to be non-blocking already. However, the IO operation may block
until the FD is ready, I can't find good sources of information, to be
safe we can just poll for readiness before.

Alternatively, we could setup the FDs ourself, and use UNIX sockets on
Windows, which can be used in blocking/non-blocking mode. I haven't
tried it, as I am not sure it is necessary.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20221006113657.2656108-6-marcandre.lureau@redhat.com>
2022-10-12 19:22:01 +04:00

385 lines
11 KiB
C

/*
* QEMU I/O channels external command driver
*
* Copyright (c) 2015 Red Hat, Inc.
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* This library is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with this library; if not, see <http://www.gnu.org/licenses/>.
*
*/
#include "qemu/osdep.h"
#include "io/channel-command.h"
#include "io/channel-watch.h"
#include "qapi/error.h"
#include "qemu/module.h"
#include "qemu/sockets.h"
#include "trace.h"
/**
* qio_channel_command_new_pid:
* @writefd: the FD connected to the command's stdin
* @readfd: the FD connected to the command's stdout
* @pid: the PID/HANDLE of the running child command
* @errp: pointer to a NULL-initialized error object
*
* Create a channel for performing I/O with the
* previously spawned command identified by @pid.
* The two file descriptors provide the connection
* to command's stdio streams, either one or which
* may be -1 to indicate that stream is not open.
*
* The channel will take ownership of the process
* @pid and will kill it when closing the channel.
* Similarly it will take responsibility for
* closing the file descriptors @writefd and @readfd.
*
* Returns: the command channel object, or NULL on error
*/
static QIOChannelCommand *
qio_channel_command_new_pid(int writefd,
int readfd,
GPid pid)
{
QIOChannelCommand *ioc;
ioc = QIO_CHANNEL_COMMAND(object_new(TYPE_QIO_CHANNEL_COMMAND));
ioc->readfd = readfd;
ioc->writefd = writefd;
ioc->pid = pid;
trace_qio_channel_command_new_pid(ioc, writefd, readfd,
#ifdef WIN32
GetProcessId(pid)
#else
pid
#endif
);
return ioc;
}
QIOChannelCommand *
qio_channel_command_new_spawn(const char *const argv[],
int flags,
Error **errp)
{
g_autoptr(GError) err = NULL;
GPid pid = 0;
GSpawnFlags gflags = G_SPAWN_CLOEXEC_PIPES | G_SPAWN_DO_NOT_REAP_CHILD;
int stdinfd = -1, stdoutfd = -1;
flags = flags & O_ACCMODE;
gflags |= flags == O_WRONLY ? G_SPAWN_STDOUT_TO_DEV_NULL : 0;
if (!g_spawn_async_with_pipes(NULL, (char **)argv, NULL, gflags, NULL, NULL,
&pid,
flags == O_RDONLY ? NULL : &stdinfd,
flags == O_WRONLY ? NULL : &stdoutfd,
NULL, &err)) {
error_setg(errp, "%s", err->message);
return NULL;
}
return qio_channel_command_new_pid(stdinfd, stdoutfd, pid);
}
#ifndef WIN32
static int qio_channel_command_abort(QIOChannelCommand *ioc,
Error **errp)
{
pid_t ret;
int status;
int step = 0;
/* See if intermediate process has exited; if not, try a nice
* SIGTERM followed by a more severe SIGKILL.
*/
rewait:
trace_qio_channel_command_abort(ioc, ioc->pid);
ret = waitpid(ioc->pid, &status, WNOHANG);
trace_qio_channel_command_wait(ioc, ioc->pid, ret, status);
if (ret == (pid_t)-1) {
if (errno == EINTR) {
goto rewait;
} else {
error_setg_errno(errp, errno,
"Cannot wait on pid %llu",
(unsigned long long)ioc->pid);
return -1;
}
} else if (ret == 0) {
if (step == 0) {
kill(ioc->pid, SIGTERM);
} else if (step == 1) {
kill(ioc->pid, SIGKILL);
} else {
error_setg(errp,
"Process %llu refused to die",
(unsigned long long)ioc->pid);
return -1;
}
step++;
usleep(10 * 1000);
goto rewait;
}
return 0;
}
#else
static int qio_channel_command_abort(QIOChannelCommand *ioc,
Error **errp)
{
DWORD ret;
TerminateProcess(ioc->pid, 0);
ret = WaitForSingleObject(ioc->pid, 1000);
if (ret != WAIT_OBJECT_0) {
error_setg(errp,
"Process %llu refused to die",
(unsigned long long)GetProcessId(ioc->pid));
return -1;
}
return 0;
}
#endif /* ! WIN32 */
static void qio_channel_command_init(Object *obj)
{
QIOChannelCommand *ioc = QIO_CHANNEL_COMMAND(obj);
ioc->readfd = -1;
ioc->writefd = -1;
ioc->pid = 0;
}
static void qio_channel_command_finalize(Object *obj)
{
QIOChannelCommand *ioc = QIO_CHANNEL_COMMAND(obj);
if (ioc->readfd != -1) {
close(ioc->readfd);
}
if (ioc->writefd != -1 &&
ioc->writefd != ioc->readfd) {
close(ioc->writefd);
}
ioc->writefd = ioc->readfd = -1;
if (ioc->pid > 0) {
qio_channel_command_abort(ioc, NULL);
g_spawn_close_pid(ioc->pid);
}
}
#ifdef WIN32
static bool win32_fd_poll(int fd, gushort events)
{
GPollFD pfd = { .fd = _get_osfhandle(fd), .events = events };
int res;
do {
res = g_poll(&pfd, 1, 0);
} while (res < 0 && errno == EINTR);
if (res == 0) {
return false;
}
return true;
}
#endif
static ssize_t qio_channel_command_readv(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
int **fds,
size_t *nfds,
Error **errp)
{
QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
ssize_t ret;
#ifdef WIN32
if (!cioc->blocking && !win32_fd_poll(cioc->readfd, G_IO_IN)) {
return QIO_CHANNEL_ERR_BLOCK;
}
#endif
retry:
ret = readv(cioc->readfd, iov, niov);
if (ret < 0) {
if (errno == EAGAIN) {
return QIO_CHANNEL_ERR_BLOCK;
}
if (errno == EINTR) {
goto retry;
}
error_setg_errno(errp, errno,
"Unable to read from command");
return -1;
}
return ret;
}
static ssize_t qio_channel_command_writev(QIOChannel *ioc,
const struct iovec *iov,
size_t niov,
int *fds,
size_t nfds,
int flags,
Error **errp)
{
QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
ssize_t ret;
#ifdef WIN32
if (!cioc->blocking && !win32_fd_poll(cioc->writefd, G_IO_OUT)) {
return QIO_CHANNEL_ERR_BLOCK;
}
#endif
retry:
ret = writev(cioc->writefd, iov, niov);
if (ret <= 0) {
if (errno == EAGAIN) {
return QIO_CHANNEL_ERR_BLOCK;
}
if (errno == EINTR) {
goto retry;
}
error_setg_errno(errp, errno, "%s",
"Unable to write to command");
return -1;
}
return ret;
}
static int qio_channel_command_set_blocking(QIOChannel *ioc,
bool enabled,
Error **errp)
{
QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
#ifdef WIN32
cioc->blocking = enabled;
#else
if ((cioc->writefd >= 0 && !g_unix_set_fd_nonblocking(cioc->writefd, !enabled, NULL)) ||
(cioc->readfd >= 0 && !g_unix_set_fd_nonblocking(cioc->readfd, !enabled, NULL))) {
error_setg_errno(errp, errno, "Failed to set FD nonblocking");
return -1;
}
#endif
return 0;
}
static int qio_channel_command_close(QIOChannel *ioc,
Error **errp)
{
QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
int rv = 0;
#ifndef WIN32
pid_t wp;
#endif
/* We close FDs before killing, because that
* gives a better chance of clean shutdown
*/
if (cioc->readfd != -1 &&
close(cioc->readfd) < 0) {
rv = -1;
}
if (cioc->writefd != -1 &&
cioc->writefd != cioc->readfd &&
close(cioc->writefd) < 0) {
rv = -1;
}
cioc->writefd = cioc->readfd = -1;
#ifndef WIN32
do {
wp = waitpid(cioc->pid, NULL, 0);
} while (wp == (pid_t)-1 && errno == EINTR);
if (wp == (pid_t)-1) {
error_setg_errno(errp, errno, "Failed to wait for pid %llu",
(unsigned long long)cioc->pid);
return -1;
}
#else
WaitForSingleObject(cioc->pid, INFINITE);
#endif
if (rv < 0) {
error_setg_errno(errp, errno, "%s",
"Unable to close command");
}
return rv;
}
static void qio_channel_command_set_aio_fd_handler(QIOChannel *ioc,
AioContext *ctx,
IOHandler *io_read,
IOHandler *io_write,
void *opaque)
{
QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
aio_set_fd_handler(ctx, cioc->readfd, false,
io_read, NULL, NULL, NULL, opaque);
aio_set_fd_handler(ctx, cioc->writefd, false,
NULL, io_write, NULL, NULL, opaque);
}
static GSource *qio_channel_command_create_watch(QIOChannel *ioc,
GIOCondition condition)
{
QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
return qio_channel_create_fd_pair_watch(ioc,
cioc->readfd,
cioc->writefd,
condition);
}
static void qio_channel_command_class_init(ObjectClass *klass,
void *class_data G_GNUC_UNUSED)
{
QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);
ioc_klass->io_writev = qio_channel_command_writev;
ioc_klass->io_readv = qio_channel_command_readv;
ioc_klass->io_set_blocking = qio_channel_command_set_blocking;
ioc_klass->io_close = qio_channel_command_close;
ioc_klass->io_create_watch = qio_channel_command_create_watch;
ioc_klass->io_set_aio_fd_handler = qio_channel_command_set_aio_fd_handler;
}
static const TypeInfo qio_channel_command_info = {
.parent = TYPE_QIO_CHANNEL,
.name = TYPE_QIO_CHANNEL_COMMAND,
.instance_size = sizeof(QIOChannelCommand),
.instance_init = qio_channel_command_init,
.instance_finalize = qio_channel_command_finalize,
.class_init = qio_channel_command_class_init,
};
static void qio_channel_command_register_types(void)
{
type_register_static(&qio_channel_command_info);
}
type_init(qio_channel_command_register_types);