1 /* vi: set sw=4 ts=4: */
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3 * circular buffer syslog implementation for busybox
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5 * Copyright (C) 2000 by Gennady Feldman <gfeldman@cachier.com>
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7 * Maintainer: Gennady Feldman <gena01@cachier.com> as of Mar 12, 2001
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9 * This program is free software; you can redistribute it and/or modify
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10 * it under the terms of the GNU General Public License as published by
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11 * the Free Software Foundation; either version 2 of the License, or
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12 * (at your option) any later version.
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14 * This program is distributed in the hope that it will be useful,
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15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
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16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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17 * General Public License for more details.
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19 * You should have received a copy of the GNU General Public License
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20 * along with this program; if not, write to the Free Software
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21 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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27 /* Stupid libc doesn't have a reliable way for use to know
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28 * that libc5 is being used. Assume this is good enough */
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29 #if ! defined __GLIBC__ || ! defined __UCLIBC__
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30 #error Sorry. Looks like you are using libc5.
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31 #error libc5 shm support isnt good enough.
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32 #error Please disable BB_FEATURE_IPC_SYSLOG
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38 #include <sys/ipc.h>
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39 #include <sys/types.h>
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40 #include <sys/sem.h>
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41 #include <sys/shm.h>
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44 #include "busybox.h"
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46 static const long KEY_ID = 0x414e4547; /*"GENA"*/
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48 static struct shbuf_ds {
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49 int size; // size of data written
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50 int head; // start of message list
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51 int tail; // end of message list
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52 char data[1]; // data/messages
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53 } *buf = NULL; // shared memory pointer
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56 // Semaphore operation structures
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57 static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
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58 static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
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60 static int shmid = -1; // ipc shared memory id
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61 static int semid = -1; // ipc semaphore id
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62 static jmp_buf jmp_env;
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64 static void error_exit(const char *str);
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65 static void interrupted(int sig);
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68 * sem_up - up()'s a semaphore.
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70 static inline void sem_up(int semid)
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72 if ( semop(semid, SMrup, 1) == -1 )
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73 error_exit("semop[SMrup]");
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77 * sem_down - down()'s a semaphore
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79 static inline void sem_down(int semid)
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81 if ( semop(semid, SMrdn, 2) == -1 )
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82 error_exit("semop[SMrdn]");
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85 extern int logread_main(int argc, char **argv)
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89 /* no options, no getopt */
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93 // handle intrrupt signal
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94 if (setjmp(jmp_env)) goto output_end;
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96 // attempt to redefine ^C signal
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97 signal(SIGINT, interrupted);
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99 if ( (shmid = shmget(KEY_ID, 0, 0)) == -1)
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100 error_exit("Can't find circular buffer");
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102 // Attach shared memory to our char*
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103 if ( (buf = shmat(shmid, NULL, SHM_RDONLY)) == NULL)
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104 error_exit("Can't get access to circular buffer from syslogd");
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106 if ( (semid = semget(KEY_ID, 0, 0)) == -1)
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107 error_exit("Can't get access to semaphone(s) for circular buffer from syslogd");
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113 //printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
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114 if (buf->head == buf->tail) {
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115 printf("<empty syslog>\n");
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118 while ( i != buf->tail) {
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119 printf("%s", buf->data+i);
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120 i+= strlen(buf->data+i) + 1;
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121 if (i >= buf->size )
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130 return EXIT_SUCCESS;
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133 static void interrupted(int sig){
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134 signal(SIGINT, SIG_IGN);
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135 longjmp(jmp_env, 1);
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138 static void error_exit(const char *str){
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140 //release all acquired resources
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