[3320] | 1 | /* vi: set sw=4 ts=4: */
|
---|
| 2 | /*
|
---|
| 3 | * circular buffer syslog implementation for busybox
|
---|
| 4 | *
|
---|
| 5 | * Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com>
|
---|
| 6 | *
|
---|
| 7 | * Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
|
---|
| 8 | *
|
---|
| 9 | * Licensed under GPLv2 or later, see file LICENSE in this source tree.
|
---|
| 10 | */
|
---|
| 11 |
|
---|
| 12 | #include "libbb.h"
|
---|
| 13 | #include <sys/ipc.h>
|
---|
| 14 | #include <sys/sem.h>
|
---|
| 15 | #include <sys/shm.h>
|
---|
| 16 |
|
---|
| 17 | #define DEBUG 0
|
---|
| 18 |
|
---|
| 19 | /* our shared key (syslogd.c and logread.c must be in sync) */
|
---|
| 20 | enum { KEY_ID = 0x414e4547 }; /* "GENA" */
|
---|
| 21 |
|
---|
| 22 | struct shbuf_ds {
|
---|
| 23 | int32_t size; // size of data - 1
|
---|
| 24 | int32_t tail; // end of message list
|
---|
| 25 | char data[1]; // messages
|
---|
| 26 | };
|
---|
| 27 |
|
---|
| 28 | static const struct sembuf init_sem[3] = {
|
---|
| 29 | {0, -1, IPC_NOWAIT | SEM_UNDO},
|
---|
| 30 | {1, 0}, {0, +1, SEM_UNDO}
|
---|
| 31 | };
|
---|
| 32 |
|
---|
| 33 | struct globals {
|
---|
| 34 | struct sembuf SMrup[1]; // {0, -1, IPC_NOWAIT | SEM_UNDO},
|
---|
| 35 | struct sembuf SMrdn[2]; // {1, 0}, {0, +1, SEM_UNDO}
|
---|
| 36 | struct shbuf_ds *shbuf;
|
---|
| 37 | } FIX_ALIASING;
|
---|
| 38 | #define G (*(struct globals*)&bb_common_bufsiz1)
|
---|
| 39 | #define SMrup (G.SMrup)
|
---|
| 40 | #define SMrdn (G.SMrdn)
|
---|
| 41 | #define shbuf (G.shbuf)
|
---|
| 42 | #define INIT_G() do { \
|
---|
| 43 | memcpy(SMrup, init_sem, sizeof(init_sem)); \
|
---|
| 44 | } while (0)
|
---|
| 45 |
|
---|
| 46 | static void error_exit(const char *str) NORETURN;
|
---|
| 47 | static void error_exit(const char *str)
|
---|
| 48 | {
|
---|
| 49 | //release all acquired resources
|
---|
| 50 | shmdt(shbuf);
|
---|
| 51 | bb_perror_msg_and_die(str);
|
---|
| 52 | }
|
---|
| 53 |
|
---|
| 54 | /*
|
---|
| 55 | * sem_up - up()'s a semaphore.
|
---|
| 56 | */
|
---|
| 57 | static void sem_up(int semid)
|
---|
| 58 | {
|
---|
| 59 | if (semop(semid, SMrup, 1) == -1)
|
---|
| 60 | error_exit("semop[SMrup]");
|
---|
| 61 | }
|
---|
| 62 |
|
---|
| 63 | static void interrupted(int sig UNUSED_PARAM)
|
---|
| 64 | {
|
---|
| 65 | signal(SIGINT, SIG_IGN);
|
---|
| 66 | shmdt(shbuf);
|
---|
| 67 | exit(EXIT_SUCCESS);
|
---|
| 68 | }
|
---|
| 69 |
|
---|
| 70 | int logread_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
|
---|
| 71 | int logread_main(int argc UNUSED_PARAM, char **argv)
|
---|
| 72 | {
|
---|
| 73 | unsigned cur;
|
---|
| 74 | int log_semid; /* ipc semaphore id */
|
---|
| 75 | int log_shmid; /* ipc shared memory id */
|
---|
| 76 | smallint follow = getopt32(argv, "f");
|
---|
| 77 |
|
---|
| 78 | INIT_G();
|
---|
| 79 |
|
---|
| 80 | log_shmid = shmget(KEY_ID, 0, 0);
|
---|
| 81 | if (log_shmid == -1)
|
---|
| 82 | bb_perror_msg_and_die("can't find syslogd buffer");
|
---|
| 83 |
|
---|
| 84 | /* Attach shared memory to our char* */
|
---|
| 85 | shbuf = shmat(log_shmid, NULL, SHM_RDONLY);
|
---|
| 86 | if (shbuf == NULL)
|
---|
| 87 | bb_perror_msg_and_die("can't access syslogd buffer");
|
---|
| 88 |
|
---|
| 89 | log_semid = semget(KEY_ID, 0, 0);
|
---|
| 90 | if (log_semid == -1)
|
---|
| 91 | error_exit("can't get access to semaphores for syslogd buffer");
|
---|
| 92 |
|
---|
| 93 | signal(SIGINT, interrupted);
|
---|
| 94 |
|
---|
| 95 | /* Suppose atomic memory read */
|
---|
| 96 | /* Max possible value for tail is shbuf->size - 1 */
|
---|
| 97 | cur = shbuf->tail;
|
---|
| 98 |
|
---|
| 99 | /* Loop for logread -f, one pass if there was no -f */
|
---|
| 100 | do {
|
---|
| 101 | unsigned shbuf_size;
|
---|
| 102 | unsigned shbuf_tail;
|
---|
| 103 | const char *shbuf_data;
|
---|
| 104 | #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
|
---|
| 105 | int i;
|
---|
| 106 | int len_first_part;
|
---|
| 107 | int len_total = len_total; /* for gcc */
|
---|
| 108 | char *copy = copy; /* for gcc */
|
---|
| 109 | #endif
|
---|
| 110 | if (semop(log_semid, SMrdn, 2) == -1)
|
---|
| 111 | error_exit("semop[SMrdn]");
|
---|
| 112 |
|
---|
| 113 | /* Copy the info, helps gcc to realize that it doesn't change */
|
---|
| 114 | shbuf_size = shbuf->size;
|
---|
| 115 | shbuf_tail = shbuf->tail;
|
---|
| 116 | shbuf_data = shbuf->data; /* pointer! */
|
---|
| 117 |
|
---|
| 118 | if (DEBUG)
|
---|
| 119 | printf("cur:%d tail:%i size:%i\n",
|
---|
| 120 | cur, shbuf_tail, shbuf_size);
|
---|
| 121 |
|
---|
| 122 | if (!follow) {
|
---|
| 123 | /* advance to oldest complete message */
|
---|
| 124 | /* find NUL */
|
---|
| 125 | cur += strlen(shbuf_data + cur);
|
---|
| 126 | if (cur >= shbuf_size) { /* last byte in buffer? */
|
---|
| 127 | cur = strnlen(shbuf_data, shbuf_tail);
|
---|
| 128 | if (cur == shbuf_tail)
|
---|
| 129 | goto unlock; /* no complete messages */
|
---|
| 130 | }
|
---|
| 131 | /* advance to first byte of the message */
|
---|
| 132 | cur++;
|
---|
| 133 | if (cur >= shbuf_size) /* last byte in buffer? */
|
---|
| 134 | cur = 0;
|
---|
| 135 | } else { /* logread -f */
|
---|
| 136 | if (cur == shbuf_tail) {
|
---|
| 137 | sem_up(log_semid);
|
---|
| 138 | fflush_all();
|
---|
| 139 | sleep(1); /* TODO: replace me with a sleep_on */
|
---|
| 140 | continue;
|
---|
| 141 | }
|
---|
| 142 | }
|
---|
| 143 |
|
---|
| 144 | /* Read from cur to tail */
|
---|
| 145 | #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
|
---|
| 146 | len_first_part = len_total = shbuf_tail - cur;
|
---|
| 147 | if (len_total < 0) {
|
---|
| 148 | /* message wraps: */
|
---|
| 149 | /* [SECOND PART.........FIRST PART] */
|
---|
| 150 | /* ^data ^tail ^cur ^size */
|
---|
| 151 | len_total += shbuf_size;
|
---|
| 152 | }
|
---|
| 153 | copy = xmalloc(len_total + 1);
|
---|
| 154 | if (len_first_part < 0) {
|
---|
| 155 | /* message wraps (see above) */
|
---|
| 156 | len_first_part = shbuf_size - cur;
|
---|
| 157 | memcpy(copy + len_first_part, shbuf_data, shbuf_tail);
|
---|
| 158 | }
|
---|
| 159 | memcpy(copy, shbuf_data + cur, len_first_part);
|
---|
| 160 | copy[len_total] = '\0';
|
---|
| 161 | cur = shbuf_tail;
|
---|
| 162 | #else
|
---|
| 163 | while (cur != shbuf_tail) {
|
---|
| 164 | fputs(shbuf_data + cur, stdout);
|
---|
| 165 | cur += strlen(shbuf_data + cur) + 1;
|
---|
| 166 | if (cur >= shbuf_size)
|
---|
| 167 | cur = 0;
|
---|
| 168 | }
|
---|
| 169 | #endif
|
---|
| 170 | unlock:
|
---|
| 171 | /* release the lock on the log chain */
|
---|
| 172 | sem_up(log_semid);
|
---|
| 173 |
|
---|
| 174 | #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
|
---|
| 175 | for (i = 0; i < len_total; i += strlen(copy + i) + 1) {
|
---|
| 176 | fputs(copy + i, stdout);
|
---|
| 177 | }
|
---|
| 178 | free(copy);
|
---|
| 179 | #endif
|
---|
| 180 | } while (follow);
|
---|
| 181 |
|
---|
| 182 | shmdt(shbuf);
|
---|
| 183 |
|
---|
| 184 | fflush_stdout_and_exit(EXIT_SUCCESS);
|
---|
| 185 | }
|
---|