Root/libbb/libbbd.c

1/*
2 * libbb/libbbd.c - Bitbang library daemon
3 *
4 * Written 2010-2011 by Werner Almesberger
5 * Copyright 2010-2011 Werner Almesberger
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 */
12
13
14#include <stdlib.h>
15#include <stdio.h>
16#include <unistd.h>
17#include <string.h>
18#include <fcntl.h>
19#include <dirent.h>
20#include <poll.h>
21#include <errno.h>
22#include <syslog.h>
23#include <sys/types.h>
24#include <sys/socket.h>
25
26#include "libbb.h"
27
28
29#define FD_DIR "/proc/self/fd"
30
31#define DRIVER_NAME "jz4740-mmc.0"
32#define UNBIND_PATH "/sys/bus/platform/drivers/jz4740-mmc/unbind"
33#define BIND_PATH "/sys/bus/platform/drivers/jz4740-mmc/bind"
34
35
36static void closefds(void)
37{
38    DIR *dir;
39    const struct dirent *de;
40    int fd;
41
42    dir = opendir(FD_DIR);
43    if (!dir) {
44        perror(FD_DIR);
45        exit(1);
46    }
47    while ((de = readdir(dir))) {
48        if (*de->d_name == '.')
49            continue;
50        fd = atoi(de->d_name);
51        if (fd == 1 || fd == 2)
52            continue;
53        if (fd == dirfd(dir))
54            continue;
55        (void) close(fd);
56    }
57    closedir(dir);
58}
59
60
61static int echo(const char *msg, const char *path)
62{
63    int fd;
64    ssize_t wrote;
65    int len = strlen(msg);
66
67    fd = open(path, O_WRONLY);
68    if (fd < 0) {
69        perror(path);
70        return -errno;
71    }
72    wrote = write(fd, msg, len);
73    if (wrote < 0) {
74        perror(path);
75        return -errno;
76    }
77    if (wrote != len) {
78        fprintf(stderr, "short write: %d < %d\n", (int) wrote, len);
79        return -ENOSPC;
80    }
81    if (close(fd) < 0) {
82        perror(path);
83        return -errno;
84    }
85    return 0;
86}
87
88
89static void lock_area(int fd, off_t from, off_t len)
90{
91    if (lseek(fd, from, SEEK_SET) == (off_t) -1) {
92        perror("lseek");
93        exit(1);
94    }
95    if (lockf(fd, F_LOCK, len) < 0) {
96        perror("lockf");
97        exit(1);
98    }
99}
100
101
102static int send_fd(int s, int fd)
103{
104    struct msghdr msg;
105    struct cmsg {
106        struct cmsghdr hdr;
107        int fd;
108    } cmsg;
109
110    memset(&msg, 0, sizeof(msg));
111    msg.msg_control = &cmsg;
112    msg.msg_controllen = sizeof(cmsg);
113    cmsg.hdr.cmsg_level = SOL_SOCKET;
114    cmsg.hdr.cmsg_type = SCM_RIGHTS;
115    cmsg.hdr.cmsg_len = sizeof(cmsg);
116    cmsg.fd = fd;
117    if (sendmsg(s, &msg, 0) >= 0)
118        return 0;
119    perror("sendmsg");
120    return -1;
121}
122
123
124static int wait_for_close(int s)
125{
126    struct pollfd fds[1];
127    int res;
128
129    fds->fd = s;
130    fds->events = 0;
131    fds->revents = POLLHUP;
132    res = poll(fds, 1, -1);
133    if (res < 0) {
134        perror("poll");
135        return -1;
136    }
137    if (!res) {
138        fprintf(stderr, "poll inexplicably returned 0\n");
139        return -1;
140    }
141    return 0;
142}
143
144
145int main(int argc, char **argv)
146{
147    int fd, res;
148    int exit_code = 1;
149
150fprintf(stderr, "setsid\n");
151    if (setsid() == (pid_t) -1) {
152        perror("setsid");
153        exit(1);
154    }
155fprintf(stderr, "closefds\n");
156    closefds();
157
158fprintf(stderr, "open devmem\n");
159    fd = open("/dev/mem", O_RDWR | O_SYNC);
160    if (fd < 0) {
161        perror("/dev/mem");
162        exit(1);
163    }
164fprintf(stderr, "lock_area\n");
165    lock_area(fd, LIBBB_GPIO_BASE+LIBBB_PORT_D_OFFSET,
166        LIBBB_PORT_D_WINDOW);
167
168fprintf(stderr, "echo (unbind)\n");
169    if (echo(DRIVER_NAME "\n", UNBIND_PATH) < 0)
170        exit(1);
171
172fprintf(stderr, "send_fd\n");
173    if (send_fd(1, fd) < 0)
174        goto cleanup;
175
176fprintf(stderr, "wait_for_close\n");
177    if (wait_for_close(1) < 0)
178        goto cleanup;
179
180    exit_code = 0;
181
182cleanup:
183fprintf(stderr, "echo (bind)n");
184    res = echo(DRIVER_NAME "\n", BIND_PATH);
185    if (res < 0) {
186        /* stderr may no longer exist. report to syslog. */
187        openlog("libbbd", LOG_CONS, LOG_USER);
188        syslog(LOG_CRIT, "libbd failed to re-bind driver (%d)", res);
189    }
190
191fprintf(stderr, "exit\n");
192    return exit_code;
193}
194

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