1/* vi: set sw=4 ts=4: */
2/*
3 * circular buffer syslog implementation for busybox
4 *
5 * Copyright (C) 2000 by Gennady Feldman <gfeldman@cachier.com>
6 *
7 * Maintainer: Gennady Feldman <gena01@cachier.com> as of Mar 12, 2001
8 *
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
13 *
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * General Public License for more details.
18 *
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
22 * 02111-1307 USA
23 *
24 */
25
26
27#include <stdio.h>
28#include <stdlib.h>
29#include <string.h>
30#include <sys/ipc.h>
31#include <sys/types.h>
32#include <sys/sem.h>
33#include <sys/shm.h>
34#include <signal.h>
35#include <setjmp.h>
36#include "busybox.h"
37
38#if __GNU_LIBRARY__ < 5
39#error Sorry.  Looks like you are using libc5.
40#error libc5 shm support isnt good enough.
41#error Please disable BB_FEATURE_IPC_SYSLOG
42#endif
43
44
45static const long KEY_ID = 0x414e4547; /*"GENA"*/
46
47static struct shbuf_ds {
48	int size;		// size of data written
49	int head;		// start of message list
50	int tail;		// end of message list
51	char data[1];		// data/messages
52} *buf = NULL;			// shared memory pointer
53
54
55// Semaphore operation structures
56static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
57static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
58
59static int	log_shmid = -1;	// ipc shared memory id
60static int	log_semid = -1;	// ipc semaphore id
61static jmp_buf	jmp_env;
62
63static void error_exit(const char *str);
64static void interrupted(int sig);
65
66/*
67 * sem_up - up()'s a semaphore.
68 */
69static inline void sem_up(int semid)
70{
71	if ( semop(semid, SMrup, 1) == -1 )
72		error_exit("semop[SMrup]");
73}
74
75/*
76 * sem_down - down()'s a semaphore
77 */
78static inline void sem_down(int semid)
79{
80	if ( semop(semid, SMrdn, 2) == -1 )
81		error_exit("semop[SMrdn]");
82}
83
84extern int logread_main(int argc, char **argv)
85{
86	int i;
87
88	/* no options, no getopt */
89	if (argc > 1)
90		show_usage();
91
92	// handle intrrupt signal
93	if (setjmp(jmp_env)) goto output_end;
94
95	// attempt to redefine ^C signal
96	signal(SIGINT, interrupted);
97
98	if ( (log_shmid = shmget(KEY_ID, 0, 0)) == -1)
99		error_exit("Can't find circular buffer");
100
101	// Attach shared memory to our char*
102	if ( (buf = shmat(log_shmid, NULL, SHM_RDONLY)) == NULL)
103		error_exit("Can't get access to circular buffer from syslogd");
104
105	if ( (log_semid = semget(KEY_ID, 0, 0)) == -1)
106	    	error_exit("Can't get access to semaphone(s) for circular buffer from syslogd");
107
108	sem_down(log_semid);
109	// Read Memory
110	i=buf->head;
111
112	//printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
113	if (buf->head == buf->tail) {
114		printf("<empty syslog>\n");
115	}
116
117	while ( i != buf->tail) {
118		printf("%s", buf->data+i);
119		i+= strlen(buf->data+i) + 1;
120		if (i >= buf->size )
121			i=0;
122	}
123	sem_up(log_semid);
124
125output_end:
126	if (log_shmid != -1)
127		shmdt(buf);
128
129	return EXIT_SUCCESS;
130}
131
132static void interrupted(int sig){
133	signal(SIGINT, SIG_IGN);
134	longjmp(jmp_env, 1);
135}
136
137static void error_exit(const char *str){
138	perror(str);
139	//release all acquired resources
140	if (log_shmid != -1)
141		shmdt(buf);
142
143	exit(1);
144}
145