[821] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * circular buffer syslog implementation for busybox
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| 4 | *
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| 5 | * Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com>
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| 6 | *
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| 7 | * Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
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| 8 | *
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| 9 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
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| 10 | */
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| 11 |
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| 12 |
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| 13 | #include "busybox.h"
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| 14 | #include <stdio.h>
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| 15 | #include <stdlib.h>
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| 16 | #include <string.h>
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| 17 | #include <sys/ipc.h>
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| 18 | #include <sys/types.h>
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| 19 | #include <sys/sem.h>
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| 20 | #include <sys/shm.h>
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| 21 | #include <signal.h>
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| 22 | #include <setjmp.h>
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| 23 | #include <unistd.h>
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| 24 |
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| 25 | static const long KEY_ID = 0x414e4547; /*"GENA"*/
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| 26 |
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| 27 | static struct shbuf_ds {
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| 28 | int size; // size of data written
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| 29 | int head; // start of message list
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| 30 | int tail; // end of message list
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| 31 | char data[1]; // data/messages
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| 32 | } *buf = NULL; // shared memory pointer
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| 33 |
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| 34 |
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| 35 | // Semaphore operation structures
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| 36 | static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
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| 37 | static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
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| 38 |
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| 39 | static int log_shmid = -1; // ipc shared memory id
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| 40 | static int log_semid = -1; // ipc semaphore id
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| 41 | static jmp_buf jmp_env;
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| 42 |
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| 43 | static void error_exit(const char *str);
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| 44 | static void interrupted(int sig);
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| 45 |
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| 46 | /*
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| 47 | * sem_up - up()'s a semaphore.
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| 48 | */
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| 49 | static inline void sem_up(int semid)
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| 50 | {
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| 51 | if ( semop(semid, SMrup, 1) == -1 )
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| 52 | error_exit("semop[SMrup]");
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| 53 | }
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| 54 |
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| 55 | /*
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| 56 | * sem_down - down()'s a semaphore
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| 57 | */
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| 58 | static inline void sem_down(int semid)
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| 59 | {
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| 60 | if ( semop(semid, SMrdn, 2) == -1 )
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| 61 | error_exit("semop[SMrdn]");
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| 62 | }
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| 63 |
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| 64 | int logread_main(int argc, char **argv)
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| 65 | {
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| 66 | int i;
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| 67 | int follow=0;
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| 68 |
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| 69 | if (argc == 2 && argv[1][0]=='-' && argv[1][1]=='f') {
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| 70 | follow = 1;
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| 71 | } else {
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| 72 | /* no options, no getopt */
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| 73 | if (argc > 1)
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| 74 | bb_show_usage();
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| 75 | }
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| 76 |
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| 77 | // handle interrupt signal
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| 78 | if (setjmp(jmp_env)) goto output_end;
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| 79 |
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| 80 | // attempt to redefine ^C signal
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| 81 | signal(SIGINT, interrupted);
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| 82 |
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| 83 | if ( (log_shmid = shmget(KEY_ID, 0, 0)) == -1)
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| 84 | error_exit("Can't find circular buffer");
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| 85 |
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| 86 | // Attach shared memory to our char*
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| 87 | if ( (buf = shmat(log_shmid, NULL, SHM_RDONLY)) == NULL)
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| 88 | error_exit("Can't get access to circular buffer from syslogd");
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| 89 |
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| 90 | if ( (log_semid = semget(KEY_ID, 0, 0)) == -1)
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| 91 | error_exit("Can't get access to semaphone(s) for circular buffer from syslogd");
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| 92 |
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| 93 | // Suppose atomic memory move
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| 94 | i = follow ? buf->tail : buf->head;
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| 95 |
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| 96 | do {
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| 97 | #ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
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| 98 | char *buf_data;
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| 99 | int log_len,j;
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| 100 | #endif
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| 101 |
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| 102 | sem_down(log_semid);
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| 103 |
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| 104 | //printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
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| 105 | if (buf->head == buf->tail || i==buf->tail) {
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| 106 | if (follow) {
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| 107 | sem_up(log_semid);
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| 108 | sleep(1); /* TODO: replace me with a sleep_on */
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| 109 | continue;
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| 110 | } else {
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| 111 | printf("<empty syslog>\n");
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| 112 | }
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| 113 | }
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| 114 |
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| 115 | // Read Memory
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| 116 | #ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
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| 117 | log_len = buf->tail - i;
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| 118 | if (log_len < 0)
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| 119 | log_len += buf->size;
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| 120 | buf_data = (char *)xmalloc(log_len);
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| 121 |
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| 122 | if (buf->tail < i) {
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| 123 | memcpy(buf_data, buf->data+i, buf->size-i);
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| 124 | memcpy(buf_data+buf->size-i, buf->data, buf->tail);
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| 125 | } else {
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| 126 | memcpy(buf_data, buf->data+i, buf->tail-i);
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| 127 | }
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| 128 | i = buf->tail;
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| 129 |
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| 130 | #else
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| 131 | while ( i != buf->tail) {
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| 132 | printf("%s", buf->data+i);
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| 133 | i+= strlen(buf->data+i) + 1;
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| 134 | if (i >= buf->size )
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| 135 | i=0;
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| 136 | }
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| 137 | #endif
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| 138 | // release the lock on the log chain
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| 139 | sem_up(log_semid);
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| 140 |
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| 141 | #ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
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| 142 | for (j=0; j < log_len; j+=strlen(buf_data+j)+1) {
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| 143 | printf("%s", buf_data+j);
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| 144 | if (follow)
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| 145 | fflush(stdout);
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| 146 | }
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| 147 | free(buf_data);
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| 148 | #endif
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| 149 | fflush(stdout);
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| 150 | } while (follow);
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| 151 |
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| 152 | output_end:
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| 153 | if (log_shmid != -1)
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| 154 | shmdt(buf);
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| 155 |
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| 156 | return EXIT_SUCCESS;
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| 157 | }
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| 158 |
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| 159 | static void interrupted(int sig){
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| 160 | signal(SIGINT, SIG_IGN);
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| 161 | longjmp(jmp_env, 1);
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| 162 | }
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| 163 |
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| 164 | static void error_exit(const char *str){
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| 165 | bb_perror_msg(str);
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| 166 | //release all acquired resources
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| 167 | if (log_shmid != -1)
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| 168 | shmdt(buf);
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| 169 |
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| 170 | exit(1);
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| 171 | }
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