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 <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