summaryrefslogtreecommitdiffstats
path: root/arch/um/os-Linux/helper.c
blob: cd15b9df5b5c1a195eae1f34439a0d4004636786 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
/*
 * Copyright (C) 2002 Jeff Dike (jdike@karaya.com)
 * Licensed under the GPL
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sched.h>
#include <sys/signal.h>
#include <sys/wait.h>
#include "user.h"
#include "kern_util.h"
#include "user_util.h"
#include "os.h"

struct helper_data {
	void (*pre_exec)(void*);
	void *pre_data;
	char **argv;
	int fd;
};

/* Debugging aid, changed only from gdb */
int helper_pause = 0;

static void helper_hup(int sig)
{
}

static int helper_child(void *arg)
{
	struct helper_data *data = arg;
	char **argv = data->argv;
	int errval;

	if(helper_pause){
		signal(SIGHUP, helper_hup);
		pause();
	}
	if(data->pre_exec != NULL)
		(*data->pre_exec)(data->pre_data);
	execvp(argv[0], argv);
	errval = -errno;
	printk("helper_child - execve of '%s' failed - errno = %d\n", argv[0], errno);
	os_write_file(data->fd, &errval, sizeof(errval));
	kill(os_getpid(), SIGKILL);
	return(0);
}

/* Returns either the pid of the child process we run or -E* on failure.
 * XXX The alloc_stack here breaks if this is called in the tracing thread */
int run_helper(void (*pre_exec)(void *), void *pre_data, char **argv,
	       unsigned long *stack_out)
{
	struct helper_data data;
	unsigned long stack, sp;
	int pid, fds[2], ret, n;

	if((stack_out != NULL) && (*stack_out != 0))
		stack = *stack_out;
	else stack = alloc_stack(0, __cant_sleep());
	if(stack == 0)
		return -ENOMEM;

	ret = os_pipe(fds, 1, 0);
	if(ret < 0){
		printk("run_helper : pipe failed, ret = %d\n", -ret);
		goto out_free;
	}

	ret = os_set_exec_close(fds[1], 1);
	if(ret < 0){
		printk("run_helper : setting FD_CLOEXEC failed, ret = %d\n",
		       -ret);
		goto out_close;
	}

	sp = stack + page_size() - sizeof(void *);
	data.pre_exec = pre_exec;
	data.pre_data = pre_data;
	data.argv = argv;
	data.fd = fds[1];
	pid = clone(helper_child, (void *) sp, CLONE_VM | SIGCHLD, &data);
	if(pid < 0){
		ret = -errno;
		printk("run_helper : clone failed, errno = %d\n", errno);
		goto out_close;
	}

	close(fds[1]);
	fds[1] = -1;

	/* Read the errno value from the child, if the exec failed, or get 0 if
	 * the exec succeeded because the pipe fd was set as close-on-exec. */
	n = os_read_file(fds[0], &ret, sizeof(ret));
	if(n == 0)
		ret = pid;
	else {
		if(n < 0){
			printk("run_helper : read on pipe failed, ret = %d\n",
			       -n);
			ret = n;
			kill(pid, SIGKILL);
		}
		CATCH_EINTR(waitpid(pid, NULL, 0));
	}

out_close:
	if (fds[1] != -1)
		close(fds[1]);
	close(fds[0]);
out_free:
	if(stack_out == NULL)
		free_stack(stack, 0);
	else *stack_out = stack;
	return(ret);
}

int run_helper_thread(int (*proc)(void *), void *arg, unsigned int flags,
		      unsigned long *stack_out, int stack_order)
{
	unsigned long stack, sp;
	int pid, status, err;

	stack = alloc_stack(stack_order, __cant_sleep());
	if(stack == 0) return(-ENOMEM);

	sp = stack + (page_size() << stack_order) - sizeof(void *);
	pid = clone(proc, (void *) sp, flags | SIGCHLD, arg);
	if(pid < 0){
		err = -errno;
		printk("run_helper_thread : clone failed, errno = %d\n",
		       errno);
		return err;
	}
	if(stack_out == NULL){
		CATCH_EINTR(pid = waitpid(pid, &status, 0));
		if(pid < 0){
			err = -errno;
			printk("run_helper_thread - wait failed, errno = %d\n",
			       errno);
			pid = err;
		}
		if(!WIFEXITED(status) || (WEXITSTATUS(status) != 0))
			printk("run_helper_thread - thread returned status "
			       "0x%x\n", status);
		free_stack(stack, stack_order);
	}
	else *stack_out = stack;
	return(pid);
}

int helper_wait(int pid)
{
	int ret;

	CATCH_EINTR(ret = waitpid(pid, NULL, WNOHANG));
	if(ret < 0){
		ret = -errno;
		printk("helper_wait : waitpid failed, errno = %d\n", errno);
	}
	return(ret);
}
OpenPOWER on IntegriCloud