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136 lines
3.3 KiB
C
136 lines
3.3 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* circular buffer syslog implementation for busybox
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*
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* Copyright (C) 2000 by Gennady Feldman <gfeldman@cachier.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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* 02111-1307 USA
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <sys/ipc.h>
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#include <sys/types.h>
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#include <sys/sem.h>
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#include <sys/shm.h>
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#include <signal.h>
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#include <setjmp.h>
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#include "busybox.h"
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static const long KEY_ID = 0x414e4547; /*"GENA"*/
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static struct shbuf_ds {
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int size; // size of data written
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int head; // start of message list
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int tail; // end of message list
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char data[1]; // data/messages
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} *buf = NULL; // shared memory pointer
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// Semaphore operation structures
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static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
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static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
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static int shmid = -1; // ipc shared memory id
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static int semid = -1; // ipc semaphore id
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static jmp_buf jmp_env;
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static void error_exit(const char *str);
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static void interrupted(int sig);
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/*
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* sem_up - up()'s a semaphore.
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*/
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static inline void sem_up(int semid)
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{
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if ( semop(semid, SMrup, 1) == -1 )
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error_exit("semop[SMrup]");
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}
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/*
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* sem_down - down()'s a semaphore
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*/
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static inline void sem_down(int semid)
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{
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if ( semop(semid, SMrdn, 2) == -1 )
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error_exit("semop[SMrdn]");
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}
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extern int logread_main(int argc, char **argv)
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{
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int i;
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/* no options, no getopt */
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if (argc > 1)
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show_usage();
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// handle intrrupt signal
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if (setjmp(jmp_env)) goto output_end;
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// attempt to redefine ^C signal
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signal(SIGINT, interrupted);
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if ( (shmid = shmget(KEY_ID, 0, 0)) == -1)
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error_exit("Can't find circular buffer");
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// Attach shared memory to our char*
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if ( (buf = shmat(shmid, NULL, SHM_RDONLY)) == NULL)
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error_exit("Can't get access to circular buffer from syslogd");
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if ( (semid = semget(KEY_ID, 0, 0)) == -1)
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error_exit("Can't get access to semaphone(s) for circular buffer from syslogd");
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sem_down(semid);
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// Read Memory
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i=buf->head;
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//printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
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if (buf->head == buf->tail) {
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printf("<empty syslog>\n");
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}
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while ( i != buf->tail) {
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printf("%s", buf->data+i);
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i+= strlen(buf->data+i) + 1;
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if (i >= buf->size )
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i=0;
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}
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sem_up(semid);
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output_end:
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if (shmid != -1)
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shmdt(buf);
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return EXIT_SUCCESS;
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}
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static void interrupted(int sig){
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signal(SIGINT, SIG_IGN);
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longjmp(jmp_env, 1);
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}
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static void error_exit(const char *str){
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perror(str);
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//release all acquired resources
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if (shmid != -1)
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shmdt(buf);
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exit(1);
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}
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