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
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
|
/* vi: set sw=4 ts=4: */
/*
* circular buffer syslog implementation for busybox
*
* Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com>
*
* Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
* 02111-1307 USA
*
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ipc.h>
#include <sys/types.h>
#include <sys/sem.h>
#include <sys/shm.h>
#include <signal.h>
#include <setjmp.h>
#include <unistd.h>
#include "busybox.h"
static const long KEY_ID = 0x414e4547; /*"GENA"*/
static struct shbuf_ds {
int size; // size of data written
int head; // start of message list
int tail; // end of message list
char data[1]; // data/messages
} *buf = NULL; // shared memory pointer
// Semaphore operation structures
static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
static int log_shmid = -1; // ipc shared memory id
static int log_semid = -1; // ipc semaphore id
static jmp_buf jmp_env;
static void error_exit(const char *str);
static void interrupted(int sig);
/*
* sem_up - up()'s a semaphore.
*/
static inline void sem_up(int semid)
{
if ( semop(semid, SMrup, 1) == -1 )
error_exit("semop[SMrup]");
}
/*
* sem_down - down()'s a semaphore
*/
static inline void sem_down(int semid)
{
if ( semop(semid, SMrdn, 2) == -1 )
error_exit("semop[SMrdn]");
}
extern int logread_main(int argc, char **argv)
{
int i;
int follow=0;
if (argc == 2 && strcmp(argv[1],"-f")==0) {
follow = 1;
} else {
/* no options, no getopt */
if (argc > 1)
bb_show_usage();
}
// handle intrrupt signal
if (setjmp(jmp_env)) goto output_end;
// attempt to redefine ^C signal
signal(SIGINT, interrupted);
if ( (log_shmid = shmget(KEY_ID, 0, 0)) == -1)
error_exit("Can't find circular buffer");
// Attach shared memory to our char*
if ( (buf = shmat(log_shmid, NULL, SHM_RDONLY)) == NULL)
error_exit("Can't get access to circular buffer from syslogd");
if ( (log_semid = semget(KEY_ID, 0, 0)) == -1)
error_exit("Can't get access to semaphone(s) for circular buffer from syslogd");
// Suppose atomic memory move
i = follow ? buf->tail : buf->head;
do {
#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
char *buf_data;
int log_len,j;
#endif
sem_down(log_semid);
//printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
if (buf->head == buf->tail || i==buf->tail) {
if (follow) {
sem_up(log_semid);
sleep(1); /* TODO: replace me with a sleep_on */
continue;
} else {
printf("<empty syslog>\n");
}
}
// Read Memory
#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
log_len = buf->tail - i;
if (log_len < 0)
log_len += buf->size;
buf_data = (char *)malloc(log_len);
if (!buf_data)
error_exit("malloc failed");
if (buf->tail < i) {
memcpy(buf_data, buf->data+i, buf->size-i);
memcpy(buf_data+buf->size-i, buf->data, buf->tail);
} else {
memcpy(buf_data, buf->data+i, buf->tail-i);
}
i = buf->tail;
#else
while ( i != buf->tail) {
printf("%s", buf->data+i);
i+= strlen(buf->data+i) + 1;
if (i >= buf->size )
i=0;
}
#endif
// release the lock on the log chain
sem_up(log_semid);
#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
for (j=0; j < log_len; j+=strlen(buf_data+j)+1) {
printf("%s", buf_data+j);
if (follow)
fflush(stdout);
}
free(buf_data);
#endif
fflush(stdout);
} while (follow);
output_end:
if (log_shmid != -1)
shmdt(buf);
return EXIT_SUCCESS;
}
static void interrupted(int sig){
signal(SIGINT, SIG_IGN);
longjmp(jmp_env, 1);
}
static void error_exit(const char *str){
perror(str);
//release all acquired resources
if (log_shmid != -1)
shmdt(buf);
exit(1);
}
|
