helper.c

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
  4 */
  5
  6#include <stdlib.h>
  7#include <string.h>
  8#include <unistd.h>
  9#include <errno.h>
 10#include <sched.h>
 11#include <pthread.h>
 12#include <linux/limits.h>
 13#include <sys/socket.h>
 14#include <sys/wait.h>
 15#include <kern_util.h>
 16#include <os.h>
 17#include <um_malloc.h>
 18
 19struct helper_data {
 20	void (*pre_exec)(void*);
 21	void *pre_data;
 22	char **argv;
 23	int fd;
 24	char *buf;
 25};
 26
 27static int helper_child(void *arg)
 28{
 29	struct helper_data *data = arg;
 30	char **argv = data->argv;
 31	int err, ret;
 32
 33	if (data->pre_exec != NULL)
 34		(*data->pre_exec)(data->pre_data);
 35	err = execvp_noalloc(data->buf, argv[0], argv);
 36
 37	/* If the exec succeeds, we don't get here */
 38	CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));
 39
 40	return 0;
 41}
 42
 43/* Returns either the pid of the child process we run or -E* on failure. */
 44int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
 45{
 46	struct helper_data data;
 47	unsigned long stack, sp;
 48	int pid, fds[2], ret, n;
 49
 50	stack = alloc_stack(0, __uml_cant_sleep());
 51	if (stack == 0)
 52		return -ENOMEM;
 53
 54	ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
 55	if (ret < 0) {
 56		ret = -errno;
 57		printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
 58		       errno);
 59		goto out_free;
 60	}
 61
 62	ret = os_set_exec_close(fds[1]);
 63	if (ret < 0) {
 64		printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
 65		       "ret = %d\n", -ret);
 66		goto out_close;
 67	}
 68
 69	sp = stack + UM_KERN_PAGE_SIZE;
 70	data.pre_exec = pre_exec;
 71	data.pre_data = pre_data;
 72	data.argv = argv;
 73	data.fd = fds[1];
 74	data.buf = __uml_cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
 75					uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
 76	pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
 77	if (pid < 0) {
 78		ret = -errno;
 79		printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
 80		       errno);
 81		goto out_free2;
 82	}
 83
 84	close(fds[1]);
 85	fds[1] = -1;
 86
 87	/*
 88	 * Read the errno value from the child, if the exec failed, or get 0 if
 89	 * the exec succeeded because the pipe fd was set as close-on-exec.
 90	 */
 91	n = read(fds[0], &ret, sizeof(ret));
 92	if (n == 0) {
 93		ret = pid;
 94	} else {
 95		if (n < 0) {
 96			n = -errno;
 97			printk(UM_KERN_ERR "run_helper : read on pipe failed, "
 98			       "ret = %d\n", -n);
 99			ret = n;
100		}
101		CATCH_EINTR(waitpid(pid, NULL, __WALL));
102	}
103
104	if (ret < 0)
105		printk(UM_KERN_ERR "run_helper : failed to exec %s on host: %s\n",
106		       argv[0], strerror(-ret));
107
108out_free2:
109	kfree(data.buf);
110out_close:
111	if (fds[1] != -1)
112		close(fds[1]);
113	close(fds[0]);
114out_free:
115	free_stack(stack, 0);
116	return ret;
117}
118
119int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
120		      unsigned long *stack_out)
121{
122	unsigned long stack, sp;
123	int pid, status, err;
124
125	/* To share memory space, use os_run_helper_thread() instead. */
126	if (flags & CLONE_VM)
127		return -EINVAL;
128
129	stack = alloc_stack(0, __uml_cant_sleep());
130	if (stack == 0)
131		return -ENOMEM;
132
133	sp = stack + UM_KERN_PAGE_SIZE;
134	pid = clone(proc, (void *) sp, flags, arg);
135	if (pid < 0) {
136		err = -errno;
137		printk(UM_KERN_ERR "run_helper_thread : clone failed, "
138		       "errno = %d\n", errno);
139		return err;
140	}
141	if (stack_out == NULL) {
142		CATCH_EINTR(pid = waitpid(pid, &status, __WALL));
143		if (pid < 0) {
144			err = -errno;
145			printk(UM_KERN_ERR "run_helper_thread - wait failed, "
146			       "errno = %d\n", errno);
147			pid = err;
148		}
149		if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
150			printk(UM_KERN_ERR "run_helper_thread - thread "
151			       "returned status 0x%x\n", status);
152		free_stack(stack, 0);
153	} else
154		*stack_out = stack;
155	return pid;
156}
157
158int helper_wait(int pid)
159{
160	int ret, status;
161	int wflags = __WALL;
162
163	CATCH_EINTR(ret = waitpid(pid, &status, wflags));
164	if (ret < 0) {
165		printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
166		       "errno = %d\n", pid, errno);
167		return -errno;
168	} else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
169		printk(UM_KERN_ERR "helper_wait : process %d exited with "
170		       "status 0x%x\n", pid, status);
171		return -ECHILD;
172	} else
173		return 0;
174}
175
176struct os_helper_thread {
177	pthread_t handle;
178};
179
180int os_run_helper_thread(struct os_helper_thread **td_out,
181			 void *(*routine)(void *), void *arg)
182{
183	struct os_helper_thread *td;
184	sigset_t sigset, oset;
185	int err, flags;
186
187	flags = __uml_cant_sleep() ? UM_GFP_ATOMIC : UM_GFP_KERNEL;
188	td = uml_kmalloc(sizeof(*td), flags);
189	if (!td)
190		return -ENOMEM;
191
192	sigfillset(&sigset);
193	if (sigprocmask(SIG_SETMASK, &sigset, &oset) < 0) {
194		err = -errno;
195		kfree(td);
196		return err;
197	}
198
199	err = pthread_create(&td->handle, NULL, routine, arg);
200
201	if (sigprocmask(SIG_SETMASK, &oset, NULL) < 0)
202		panic("Failed to restore the signal mask: %d", errno);
203
204	if (err != 0)
205		kfree(td);
206	else
207		*td_out = td;
208
209	return -err;
210}
211
212void os_kill_helper_thread(struct os_helper_thread *td)
213{
214	pthread_cancel(td->handle);
215	pthread_join(td->handle, NULL);
216	kfree(td);
217}
218
219void os_fix_helper_thread_signals(void)
220{
221	sigset_t sigset;
222
223	sigemptyset(&sigset);
224
225	sigaddset(&sigset, SIGWINCH);
226	sigaddset(&sigset, SIGPIPE);
227	sigaddset(&sigset, SIGPROF);
228	sigaddset(&sigset, SIGINT);
229	sigaddset(&sigset, SIGTERM);
230	sigaddset(&sigset, SIGCHLD);
231	sigaddset(&sigset, SIGALRM);
232	sigaddset(&sigset, SIGIO);
233	sigaddset(&sigset, SIGUSR1);
234
235	pthread_sigmask(SIG_SETMASK, &sigset, NULL);
236}