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