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
18 struct helper_data {
19 void (*pre_exec)(void*);
20 void *pre_data;
21 char **argv;
22 int fd;
23 char *buf;
24 };
25
26 static 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. */
43 int 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
107 out_free2:
108 kfree(data.buf);
109 out_close:
110 if (fds[1] != -1)
111 close(fds[1]);
112 close(fds[0]);
113 out_free:
114 free_stack(stack, 0);
115 return ret;
116 }
117
118 int 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
153 int 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
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