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 <linux/limits.h>
12#include <sys/socket.h>
13#include <sys/wait.h>
14#include <kern_util.h>
15#include <os.h>
16#include <um_malloc.h>
17
18struct helper_data {
19	void (*pre_exec)(void*);
20	void *pre_data;
21	char **argv;
22	int fd;
23	char *buf;
24};
25
26static int helper_child(void *arg)
27{
28	struct helper_data *data = arg;
29	char **argv = data->argv;
30	int err, ret;
31
32	if (data->pre_exec != NULL)
33		(*data->pre_exec)(data->pre_data);
34	err = execvp_noalloc(data->buf, argv[0], argv);
35
36	/* If the exec succeeds, we don't get here */
37	CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));
38
39	return 0;
40}
41
42/* Returns either the pid of the child process we run or -E* on failure. */
43int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
44{
45	struct helper_data data;
46	unsigned long stack, sp;
47	int pid, fds[2], ret, n;
48
49	stack = alloc_stack(0, __uml_cant_sleep());
50	if (stack == 0)
51		return -ENOMEM;
52
53	ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
54	if (ret < 0) {
55		ret = -errno;
56		printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
57		       errno);
58		goto out_free;
59	}
60
61	ret = os_set_exec_close(fds[1]);
62	if (ret < 0) {
63		printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
64		       "ret = %d\n", -ret);
65		goto out_close;
66	}
67
68	sp = stack + UM_KERN_PAGE_SIZE;
69	data.pre_exec = pre_exec;
70	data.pre_data = pre_data;
71	data.argv = argv;
72	data.fd = fds[1];
73	data.buf = __uml_cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
74					uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
75	pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
76	if (pid < 0) {
77		ret = -errno;
78		printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
79		       errno);
80		goto out_free2;
81	}
82
83	close(fds[1]);
84	fds[1] = -1;
85
86	/*
87	 * Read the errno value from the child, if the exec failed, or get 0 if
88	 * the exec succeeded because the pipe fd was set as close-on-exec.
89	 */
90	n = read(fds[0], &ret, sizeof(ret));
91	if (n == 0) {
92		ret = pid;
93	} else {
94		if (n < 0) {
95			n = -errno;
96			printk(UM_KERN_ERR "run_helper : read on pipe failed, "
97			       "ret = %d\n", -n);
98			ret = n;
99		}
100		CATCH_EINTR(waitpid(pid, NULL, __WALL));
101	}
102
103	if (ret < 0)
104		printk(UM_KERN_ERR "run_helper : failed to exec %s on host: %s\n",
105		       argv[0], strerror(-ret));
106
107out_free2:
108	kfree(data.buf);
109out_close:
110	if (fds[1] != -1)
111		close(fds[1]);
112	close(fds[0]);
113out_free:
114	free_stack(stack, 0);
115	return ret;
116}
117
118int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
119		      unsigned long *stack_out)
120{
121	unsigned long stack, sp;
122	int pid, status, err;
123
124	stack = alloc_stack(0, __uml_cant_sleep());
125	if (stack == 0)
126		return -ENOMEM;
127
128	sp = stack + UM_KERN_PAGE_SIZE;
129	pid = clone(proc, (void *) sp, flags, arg);
130	if (pid < 0) {
131		err = -errno;
132		printk(UM_KERN_ERR "run_helper_thread : clone failed, "
133		       "errno = %d\n", errno);
134		return err;
135	}
136	if (stack_out == NULL) {
137		CATCH_EINTR(pid = waitpid(pid, &status, __WALL));
138		if (pid < 0) {
139			err = -errno;
140			printk(UM_KERN_ERR "run_helper_thread - wait failed, "
141			       "errno = %d\n", errno);
142			pid = err;
143		}
144		if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
145			printk(UM_KERN_ERR "run_helper_thread - thread "
146			       "returned status 0x%x\n", status);
147		free_stack(stack, 0);
148	} else
149		*stack_out = stack;
150	return pid;
151}
152
153int helper_wait(int pid)
154{
155	int ret, status;
156	int wflags = __WALL;
157
158	CATCH_EINTR(ret = waitpid(pid, &status, wflags));
159	if (ret < 0) {
160		printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
161		       "errno = %d\n", pid, errno);
162		return -errno;
163	} else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
164		printk(UM_KERN_ERR "helper_wait : process %d exited with "
165		       "status 0x%x\n", pid, status);
166		return -ECHILD;
167	} else
168		return 0;
169}
170