diff options
Diffstat (limited to 'sysklogd/logread.c')
| -rw-r--r-- | sysklogd/logread.c | 185 |
1 files changed, 185 insertions, 0 deletions
diff --git a/sysklogd/logread.c b/sysklogd/logread.c new file mode 100644 index 0000000..603a377 --- /dev/null +++ b/sysklogd/logread.c @@ -0,0 +1,185 @@ +/* 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 "libbb.h" +#include <sys/ipc.h> +#include <sys/sem.h> +#include <sys/shm.h> + +#define DEBUG 0 + +/* our shared key (syslogd.c and logread.c must be in sync) */ +enum { KEY_ID = 0x414e4547 }; /* "GENA" */ + +struct shbuf_ds { + int32_t size; // size of data - 1 + int32_t tail; // end of message list + char data[1]; // messages +}; + +static const struct sembuf init_sem[3] = { + {0, -1, IPC_NOWAIT | SEM_UNDO}, + {1, 0}, {0, +1, SEM_UNDO} +}; + +struct globals { + struct sembuf SMrup[1]; // {0, -1, IPC_NOWAIT | SEM_UNDO}, + struct sembuf SMrdn[2]; // {1, 0}, {0, +1, SEM_UNDO} + struct shbuf_ds *shbuf; +}; +#define G (*(struct globals*)&bb_common_bufsiz1) +#define SMrup (G.SMrup) +#define SMrdn (G.SMrdn) +#define shbuf (G.shbuf) +#define INIT_G() do { \ + memcpy(SMrup, init_sem, sizeof(init_sem)); \ +} while (0) + +static void error_exit(const char *str) NORETURN; +static void error_exit(const char *str) +{ + //release all acquired resources + shmdt(shbuf); + bb_perror_msg_and_die(str); +} + +/* + * sem_up - up()'s a semaphore. + */ +static void sem_up(int semid) +{ + if (semop(semid, SMrup, 1) == -1) + error_exit("semop[SMrup]"); +} + +static void interrupted(int sig UNUSED_PARAM) +{ + signal(SIGINT, SIG_IGN); + shmdt(shbuf); + exit(EXIT_SUCCESS); +} + +int logread_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; +int logread_main(int argc UNUSED_PARAM, char **argv) +{ + unsigned cur; + int log_semid; /* ipc semaphore id */ + int log_shmid; /* ipc shared memory id */ + smallint follow = getopt32(argv, "f"); + + INIT_G(); + + log_shmid = shmget(KEY_ID, 0, 0); + if (log_shmid == -1) + bb_perror_msg_and_die("can't find syslogd buffer"); + + /* Attach shared memory to our char* */ + shbuf = shmat(log_shmid, NULL, SHM_RDONLY); + if (shbuf == NULL) + bb_perror_msg_and_die("can't access syslogd buffer"); + + log_semid = semget(KEY_ID, 0, 0); + if (log_semid == -1) + error_exit("can't get access to semaphores for syslogd buffer"); + + signal(SIGINT, interrupted); + + /* Suppose atomic memory read */ + /* Max possible value for tail is shbuf->size - 1 */ + cur = shbuf->tail; + + /* Loop for logread -f, one pass if there was no -f */ + do { + unsigned shbuf_size; + unsigned shbuf_tail; + const char *shbuf_data; +#if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING + int i; + int len_first_part; + int len_total = len_total; /* for gcc */ + char *copy = copy; /* for gcc */ +#endif + if (semop(log_semid, SMrdn, 2) == -1) + error_exit("semop[SMrdn]"); + + /* Copy the info, helps gcc to realize that it doesn't change */ + shbuf_size = shbuf->size; + shbuf_tail = shbuf->tail; + shbuf_data = shbuf->data; /* pointer! */ + + if (DEBUG) + printf("cur:%d tail:%i size:%i\n", + cur, shbuf_tail, shbuf_size); + + if (!follow) { + /* advance to oldest complete message */ + /* find NUL */ + cur += strlen(shbuf_data + cur); + if (cur >= shbuf_size) { /* last byte in buffer? */ + cur = strnlen(shbuf_data, shbuf_tail); + if (cur == shbuf_tail) + goto unlock; /* no complete messages */ + } + /* advance to first byte of the message */ + cur++; + if (cur >= shbuf_size) /* last byte in buffer? */ + cur = 0; + } else { /* logread -f */ + if (cur == shbuf_tail) { + sem_up(log_semid); + fflush(stdout); + sleep(1); /* TODO: replace me with a sleep_on */ + continue; + } + } + + /* Read from cur to tail */ +#if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING + len_first_part = len_total = shbuf_tail - cur; + if (len_total < 0) { + /* message wraps: */ + /* [SECOND PART.........FIRST PART] */ + /* ^data ^tail ^cur ^size */ + len_total += shbuf_size; + } + copy = xmalloc(len_total + 1); + if (len_first_part < 0) { + /* message wraps (see above) */ + len_first_part = shbuf_size - cur; + memcpy(copy + len_first_part, shbuf_data, shbuf_tail); + } + memcpy(copy, shbuf_data + cur, len_first_part); + copy[len_total] = '\0'; + cur = shbuf_tail; +#else + while (cur != shbuf_tail) { + fputs(shbuf_data + cur, stdout); + cur += strlen(shbuf_data + cur) + 1; + if (cur >= shbuf_size) + cur = 0; + } +#endif + unlock: + /* release the lock on the log chain */ + sem_up(log_semid); + +#if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING + for (i = 0; i < len_total; i += strlen(copy + i) + 1) { + fputs(copy + i, stdout); + } + free(copy); +#endif + } while (follow); + + shmdt(shbuf); + + fflush_stdout_and_exit(EXIT_SUCCESS); +} |