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/* 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
*
* Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
*/
#include "busybox.h"
#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>
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 void sem_up(int semid)
{
if ( semop(semid, SMrup, 1) == -1 )
error_exit("semop[SMrup]");
}
/*
* sem_down - down()'s a semaphore
*/
static void sem_down(int semid)
{
if ( semop(semid, SMrdn, 2) == -1 )
error_exit("semop[SMrdn]");
}
int logread_main(int argc, char **argv)
{
int i;
int follow=0;
if (argc == 2 && argv[1][0]=='-' && argv[1][1]=='f') {
follow = 1;
} else {
/* no options, no getopt */
if (argc > 1)
bb_show_usage();
}
// handle interrupt 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 semaphore(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 = xmalloc(log_len);
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){
bb_perror_msg(str);
//release all acquired resources
if (log_shmid != -1)
shmdt(buf);
exit(1);
}
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