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io/command: use glib GSpawn, instead of open-coding fork/exec
Simplify qio_channel_command_new_spawn() with GSpawn API. This will allow to build for WIN32 in the following patches. As pointed out by Daniel Berrangé: there is a change in semantics here too. The current code only touches stdin/stdout/stderr. Any other FDs which do NOT have O_CLOEXEC set will be inherited. With the new code, all FDs except stdin/out/err will be explicitly closed, because we don't set the flag G_SPAWN_LEAVE_DESCRIPTORS_OPEN. The only place we use QIOChannelCommand today is the migration exec: protocol, and that is only declared to use stdin/stdout. Reviewed-by: Daniel P. Berrangé <berrange@redhat.com> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Message-Id: <20221006113657.2656108-5-marcandre.lureau@redhat.com>
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@ -41,7 +41,7 @@ struct QIOChannelCommand {
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QIOChannel parent;
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int writefd;
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int readfd;
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pid_t pid;
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GPid pid;
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};
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@ -31,7 +31,7 @@
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* qio_channel_command_new_pid:
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* @writefd: the FD connected to the command's stdin
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* @readfd: the FD connected to the command's stdout
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* @pid: the PID of the running child command
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* @pid: the PID/HANDLE of the running child command
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* @errp: pointer to a NULL-initialized error object
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*
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* Create a channel for performing I/O with the
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@ -50,7 +50,7 @@
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static QIOChannelCommand *
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qio_channel_command_new_pid(int writefd,
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int readfd,
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pid_t pid)
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GPid pid)
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{
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QIOChannelCommand *ioc;
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@ -69,94 +69,24 @@ qio_channel_command_new_spawn(const char *const argv[],
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int flags,
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Error **errp)
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{
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pid_t pid = -1;
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int stdinfd[2] = { -1, -1 };
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int stdoutfd[2] = { -1, -1 };
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int devnull = -1;
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bool stdinnull = false, stdoutnull = false;
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QIOChannelCommand *ioc;
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g_autoptr(GError) err = NULL;
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GPid pid = 0;
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GSpawnFlags gflags = G_SPAWN_CLOEXEC_PIPES | G_SPAWN_DO_NOT_REAP_CHILD;
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int stdinfd = -1, stdoutfd = -1;
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flags = flags & O_ACCMODE;
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gflags |= flags == O_WRONLY ? G_SPAWN_STDOUT_TO_DEV_NULL : 0;
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if (flags == O_RDONLY) {
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stdinnull = true;
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}
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if (flags == O_WRONLY) {
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stdoutnull = true;
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if (!g_spawn_async_with_pipes(NULL, (char **)argv, NULL, gflags, NULL, NULL,
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&pid,
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flags == O_RDONLY ? NULL : &stdinfd,
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flags == O_WRONLY ? NULL : &stdoutfd,
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NULL, &err)) {
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error_setg(errp, "%s", err->message);
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return NULL;
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}
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if (stdinnull || stdoutnull) {
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devnull = open("/dev/null", O_RDWR);
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if (devnull < 0) {
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error_setg_errno(errp, errno,
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"Unable to open /dev/null");
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goto error;
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}
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}
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if ((!stdinnull && !g_unix_open_pipe(stdinfd, FD_CLOEXEC, NULL)) ||
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(!stdoutnull && !g_unix_open_pipe(stdoutfd, FD_CLOEXEC, NULL))) {
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error_setg_errno(errp, errno,
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"Unable to open pipe");
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goto error;
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}
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pid = qemu_fork(errp);
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if (pid < 0) {
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goto error;
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}
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if (pid == 0) { /* child */
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dup2(stdinnull ? devnull : stdinfd[0], STDIN_FILENO);
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dup2(stdoutnull ? devnull : stdoutfd[1], STDOUT_FILENO);
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/* Leave stderr connected to qemu's stderr */
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if (!stdinnull) {
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close(stdinfd[0]);
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close(stdinfd[1]);
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}
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if (!stdoutnull) {
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close(stdoutfd[0]);
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close(stdoutfd[1]);
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}
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if (devnull != -1) {
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close(devnull);
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}
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execv(argv[0], (char * const *)argv);
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_exit(1);
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}
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if (!stdinnull) {
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close(stdinfd[0]);
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}
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if (!stdoutnull) {
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close(stdoutfd[1]);
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}
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ioc = qio_channel_command_new_pid(stdinnull ? devnull : stdinfd[1],
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stdoutnull ? devnull : stdoutfd[0],
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pid);
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trace_qio_channel_command_new_spawn(ioc, argv[0], flags);
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return ioc;
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error:
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if (devnull != -1) {
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close(devnull);
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}
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if (stdinfd[0] != -1) {
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close(stdinfd[0]);
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}
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if (stdinfd[1] != -1) {
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close(stdinfd[1]);
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}
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if (stdoutfd[0] != -1) {
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close(stdoutfd[0]);
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}
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if (stdoutfd[1] != -1) {
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close(stdoutfd[1]);
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}
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return NULL;
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return qio_channel_command_new_pid(stdinfd, stdoutfd, pid);
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}
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#else /* WIN32 */
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@ -221,7 +151,7 @@ static void qio_channel_command_init(Object *obj)
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QIOChannelCommand *ioc = QIO_CHANNEL_COMMAND(obj);
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ioc->readfd = -1;
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ioc->writefd = -1;
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ioc->pid = -1;
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ioc->pid = 0;
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}
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static void qio_channel_command_finalize(Object *obj)
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@ -239,6 +169,7 @@ static void qio_channel_command_finalize(Object *obj)
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#ifndef WIN32
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qio_channel_command_abort(ioc, NULL);
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#endif
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g_spawn_close_pid(ioc->pid);
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}
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}
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