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1 /*
2  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{addtoit,linux.intel}.com)
3  * Licensed under the GPL
4  */
5 
6 #include <stdlib.h>
7 #include <unistd.h>
8 #include <errno.h>
9 #include <sched.h>
10 #include <linux/limits.h>
11 #include <sys/socket.h>
12 #include <sys/wait.h>
13 #include <kern_util.h>
14 #include <os.h>
15 #include <um_malloc.h>
16 
17 struct helper_data {
18 	void (*pre_exec)(void*);
19 	void *pre_data;
20 	char **argv;
21 	int fd;
22 	char *buf;
23 };
24 
helper_child(void * arg)25 static int helper_child(void *arg)
26 {
27 	struct helper_data *data = arg;
28 	char **argv = data->argv;
29 	int err, ret;
30 
31 	if (data->pre_exec != NULL)
32 		(*data->pre_exec)(data->pre_data);
33 	err = execvp_noalloc(data->buf, argv[0], argv);
34 
35 	/* If the exec succeeds, we don't get here */
36 	CATCH_EINTR(ret = write(data->fd, &err, sizeof(err)));
37 
38 	return 0;
39 }
40 
41 /* Returns either the pid of the child process we run or -E* on failure. */
run_helper(void (* pre_exec)(void *),void * pre_data,char ** argv)42 int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv)
43 {
44 	struct helper_data data;
45 	unsigned long stack, sp;
46 	int pid, fds[2], ret, n;
47 
48 	stack = alloc_stack(0, __cant_sleep());
49 	if (stack == 0)
50 		return -ENOMEM;
51 
52 	ret = socketpair(AF_UNIX, SOCK_STREAM, 0, fds);
53 	if (ret < 0) {
54 		ret = -errno;
55 		printk(UM_KERN_ERR "run_helper : pipe failed, errno = %d\n",
56 		       errno);
57 		goto out_free;
58 	}
59 
60 	ret = os_set_exec_close(fds[1]);
61 	if (ret < 0) {
62 		printk(UM_KERN_ERR "run_helper : setting FD_CLOEXEC failed, "
63 		       "ret = %d\n", -ret);
64 		goto out_close;
65 	}
66 
67 	sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
68 	data.pre_exec = pre_exec;
69 	data.pre_data = pre_data;
70 	data.argv = argv;
71 	data.fd = fds[1];
72 	data.buf = __cant_sleep() ? uml_kmalloc(PATH_MAX, UM_GFP_ATOMIC) :
73 					uml_kmalloc(PATH_MAX, UM_GFP_KERNEL);
74 	pid = clone(helper_child, (void *) sp, CLONE_VM, &data);
75 	if (pid < 0) {
76 		ret = -errno;
77 		printk(UM_KERN_ERR "run_helper : clone failed, errno = %d\n",
78 		       errno);
79 		goto out_free2;
80 	}
81 
82 	close(fds[1]);
83 	fds[1] = -1;
84 
85 	/*
86 	 * Read the errno value from the child, if the exec failed, or get 0 if
87 	 * the exec succeeded because the pipe fd was set as close-on-exec.
88 	 */
89 	n = read(fds[0], &ret, sizeof(ret));
90 	if (n == 0) {
91 		ret = pid;
92 	} else {
93 		if (n < 0) {
94 			n = -errno;
95 			printk(UM_KERN_ERR "run_helper : read on pipe failed, "
96 			       "ret = %d\n", -n);
97 			ret = n;
98 		}
99 		CATCH_EINTR(waitpid(pid, NULL, __WALL));
100 	}
101 
102 out_free2:
103 	kfree(data.buf);
104 out_close:
105 	if (fds[1] != -1)
106 		close(fds[1]);
107 	close(fds[0]);
108 out_free:
109 	free_stack(stack, 0);
110 	return ret;
111 }
112 
run_helper_thread(int (* proc)(void *),void * arg,unsigned int flags,unsigned long * stack_out)113 int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
114 		      unsigned long *stack_out)
115 {
116 	unsigned long stack, sp;
117 	int pid, status, err;
118 
119 	stack = alloc_stack(0, __cant_sleep());
120 	if (stack == 0)
121 		return -ENOMEM;
122 
123 	sp = stack + UM_KERN_PAGE_SIZE - sizeof(void *);
124 	pid = clone(proc, (void *) sp, flags, arg);
125 	if (pid < 0) {
126 		err = -errno;
127 		printk(UM_KERN_ERR "run_helper_thread : clone failed, "
128 		       "errno = %d\n", errno);
129 		return err;
130 	}
131 	if (stack_out == NULL) {
132 		CATCH_EINTR(pid = waitpid(pid, &status, __WALL));
133 		if (pid < 0) {
134 			err = -errno;
135 			printk(UM_KERN_ERR "run_helper_thread - wait failed, "
136 			       "errno = %d\n", errno);
137 			pid = err;
138 		}
139 		if (!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
140 			printk(UM_KERN_ERR "run_helper_thread - thread "
141 			       "returned status 0x%x\n", status);
142 		free_stack(stack, 0);
143 	} else
144 		*stack_out = stack;
145 	return pid;
146 }
147 
helper_wait(int pid)148 int helper_wait(int pid)
149 {
150 	int ret, status;
151 	int wflags = __WALL;
152 
153 	CATCH_EINTR(ret = waitpid(pid, &status, wflags));
154 	if (ret < 0) {
155 		printk(UM_KERN_ERR "helper_wait : waitpid process %d failed, "
156 		       "errno = %d\n", pid, errno);
157 		return -errno;
158 	} else if (!WIFEXITED(status) || WEXITSTATUS(status) != 0) {
159 		printk(UM_KERN_ERR "helper_wait : process %d exited with "
160 		       "status 0x%x\n", pid, status);
161 		return -ECHILD;
162 	} else
163 		return 0;
164 }
165