*
* Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
*
- * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
+//usage:#define logread_trivial_usage
+//usage: "[-f]"
+//usage:#define logread_full_usage "\n\n"
+//usage: "Show messages in syslogd's circular buffer\n"
+//usage: "\n -f Output data as log grows"
+
#include "libbb.h"
#include <sys/ipc.h>
#include <sys/sem.h>
#define DEBUG 0
+/* our shared key (syslogd.c and logread.c must be in sync) */
enum { KEY_ID = 0x414e4547 }; /* "GENA" */
-static struct shbuf_ds {
- int32_t size; // size of data written
- int32_t head; // start of message list
+struct shbuf_ds {
+ int32_t size; // size of data - 1
int32_t tail; // end of message list
- char data[1]; // data/messages
-} *buf; // 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 void error_exit(const char *str) ATTRIBUTE_NORETURN;
+ 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;
+} FIX_ALIASING;
+#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(buf);
+ shmdt(shbuf);
bb_perror_msg_and_die(str);
}
error_exit("semop[SMrup]");
}
-static void interrupted(int sig ATTRIBUTE_UNUSED)
+static void interrupted(int sig UNUSED_PARAM)
{
signal(SIGINT, SIG_IGN);
- shmdt(buf);
- exit(0);
+ shmdt(shbuf);
+ exit(EXIT_SUCCESS);
}
-int logread_main(int argc, char **argv);
-int logread_main(int argc, char **argv)
+int logread_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int logread_main(int argc UNUSED_PARAM, char **argv)
{
- int cur;
+ unsigned cur;
int log_semid; /* ipc semaphore id */
int log_shmid; /* ipc shared memory id */
- smallint follow = getopt32(argc, argv, "f");
+ 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*
- buf = shmat(log_shmid, NULL, SHM_RDONLY);
- if (buf == NULL)
+ /* 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");
- // attempt to redefine ^C signal
signal(SIGINT, interrupted);
- // Suppose atomic memory move
- cur = follow ? buf->tail : buf->head;
+ /* 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
- char *buf_data;
- int log_len, j;
+ 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]");
- if (DEBUG)
- printf("head:%i cur:%d tail:%i size:%i\n",
- buf->head, cur, buf->tail, buf->size);
+ /* 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 (buf->head == buf->tail || cur == buf->tail) {
- if (follow) {
+ 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);
+ fflush_all();
sleep(1); /* TODO: replace me with a sleep_on */
continue;
}
- puts("<empty syslog>");
}
- // Read Memory
+ /* Read from cur to tail */
#if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
- log_len = buf->tail - cur;
- if (log_len < 0)
- log_len += buf->size;
- buf_data = xmalloc(log_len);
-
- if (buf->tail >= cur)
- j = log_len;
- else
- j = buf->size - cur;
- memcpy(buf_data, buf->data + cur, j);
-
- if (buf->tail < cur)
- memcpy(buf_data + buf->size - cur, buf->data, buf->tail);
- cur = buf->tail;
+ 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 != buf->tail) {
- fputs(buf->data + cur, stdout);
- cur += strlen(buf->data + cur) + 1;
- if (cur >= buf->size)
+ while (cur != shbuf_tail) {
+ fputs(shbuf_data + cur, stdout);
+ cur += strlen(shbuf_data + cur) + 1;
+ if (cur >= shbuf_size)
cur = 0;
}
#endif
- // release the lock on the log chain
+ unlock:
+ /* release the lock on the log chain */
sem_up(log_semid);
#if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
- for (j = 0; j < log_len; j += strlen(buf_data+j) + 1) {
- fputs(buf_data + j, stdout);
+ for (i = 0; i < len_total; i += strlen(copy + i) + 1) {
+ fputs(copy + i, stdout);
}
- free(buf_data);
+ free(copy);
#endif
} while (follow);
- shmdt(buf);
+ shmdt(shbuf);
fflush_stdout_and_exit(EXIT_SUCCESS);
}
projects / oweals / busybox.git / blobdiff