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
 17struct helper_data {
 18	void (*pre_exec)(void*);
 19	void *pre_data;
 20	char **argv;
 21	int fd;
 22	char *buf;
 23};
 24
 25static 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. */
 42int 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
102out_free2:
103	kfree(data.buf);
104out_close:
105	if (fds[1] != -1)
106		close(fds[1]);
107	close(fds[0]);
108out_free:
109	free_stack(stack, 0);
110	return ret;
111}
112
113int 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
148int 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}