/* vi: set sw=4 ts=4: *//* * circular buffer syslog implementation for busybox * * Copyright (C) 2000 by Gennady Feldman <gfeldman@cachier.com> * * Maintainer: Gennady Feldman <gena01@cachier.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 "busybox.h"#if __GNU_LIBRARY__ < 5#error Sorry.  Looks like you are using libc5.  #error libc5 shm support isnt good enough.#error Please disable BB_FEATURE_IPC_SYSLOG #endif	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 structuresstatic struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrupstatic struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdnstatic int	log_shmid = -1;	// ipc shared memory idstatic int	log_semid = -1;	// ipc semaphore idstatic 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;		/* no options, no getopt */	if (argc > 1)		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");	sem_down(log_semid);		// Read Memory 	i=buf->head;	//printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);	if (buf->head == buf->tail) {		printf("<empty syslog>\n");	}		while ( i != buf->tail) {		printf("%s", buf->data+i);		i+= strlen(buf->data+i) + 1;		if (i >= buf->size )			i=0;	}	sem_up(log_semid);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);}