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authorGravatar Denis Vlasenko <vda.linux@googlemail.com>2007-08-12 21:33:06 +0000
committerGravatar Denis Vlasenko <vda.linux@googlemail.com>2007-08-12 21:33:06 +0000
commit5f1b149d541ebba7cab841cb647f113248f9fb8f (patch)
treee7f962fba89b6e201b4c857e32d85c9671b3db0d
parent1b9064d5355b5c26676e8447a1900116066e42e4 (diff)
downloadbusybox-5f1b149d541ebba7cab841cb647f113248f9fb8f.tar.gz
busybox-5f1b149d541ebba7cab841cb647f113248f9fb8f.tar.bz2
syslogd,logread: get rid of head pointer, fix logread bug in the process
function old new delta logread_main 450 462 +12 syslogd_main 1246 1252 +6 shbuf - 4 +4 buf 34 30 -4 packed_usage 22729 22724 -5 log_locally 957 767 -190 ------------------------------------------------------------------------------ (add/remove: 1/0 grow/shrink: 2/3 up/down: 22/-199) Total: -177 bytes text data bss dec hex filename 773886 1116 11316 786318 bff8e busybox_old 773714 1116 11316 786146 bfee2 busybox_unstripped
-rw-r--r--include/usage.h10
-rw-r--r--sysklogd/logread.c113
-rw-r--r--sysklogd/syslogd.c55
3 files changed, 86 insertions, 92 deletions
diff --git a/include/usage.h b/include/usage.h
index 9c14f4508..3f2916006 100644
--- a/include/usage.h
+++ b/include/usage.h
@@ -3327,17 +3327,17 @@ USE_FEATURE_RUN_PARTS_FANCY("\n -l Prints names of all matching files even when
"Note that this version of syslogd ignores /etc/syslog.conf." \
"\n\nOptions:" \
"\n -n Run as foreground process" \
- "\n -O FILE Use an alternate log file (default=/var/log/messages)" \
- "\n -l n Sets the local log level of messages to n" \
- "\n -S Make logging output smaller" \
+ "\n -O FILE Log to given file (default=/var/log/messages)" \
+ "\n -l n Set local log level" \
+ "\n -S Smaller logging output" \
USE_FEATURE_ROTATE_LOGFILE( \
"\n -s SIZE Max size (KB) before rotate (default=200KB, 0=off)" \
"\n -b NUM Number of rotated logs to keep (default=1, max=99, 0=purge)") \
USE_FEATURE_REMOTE_LOG( \
"\n -R HOST[:PORT] Log to IP or hostname on PORT (default PORT=514/UDP)" \
- "\n -L Log locally and via network logging (default is network only)") \
+ "\n -L Log locally and via network (default is network only if -R)") \
USE_FEATURE_IPC_SYSLOG( \
- "\n -C[size(KiB)] Log to a shared mem buffer (read the buffer using logread)")
+ "\n -C[size(KiB)] Log to shared mem buffer (read it using logread)")
/* NB: -Csize shouldn't have space (because size is optional) */
/* "\n -m MIN Minutes between MARK lines (default=20, 0=off)" */
#define syslogd_example_usage \
diff --git a/sysklogd/logread.c b/sysklogd/logread.c
index ac354b5c3..597e285a5 100644
--- a/sysklogd/logread.c
+++ b/sysklogd/logread.c
@@ -19,11 +19,10 @@
enum { KEY_ID = 0x414e4547 }; /* "GENA" */
static struct shbuf_ds {
- int32_t size; // size of data written
- int32_t head; // start of message list
+ int32_t size; // size of data - 1
int32_t tail; // end of message list
- char data[1]; // data/messages
-} *buf; // shared memory pointer
+ char data[1]; // messages
+} *shbuf;
// Semaphore operation structures
static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
@@ -34,7 +33,7 @@ static void error_exit(const char *str) ATTRIBUTE_NORETURN;
static void error_exit(const char *str)
{
//release all acquired resources
- shmdt(buf);
+ shmdt(shbuf);
bb_perror_msg_and_die(str);
}
@@ -50,7 +49,7 @@ static void sem_up(int semid)
static void interrupted(int sig ATTRIBUTE_UNUSED)
{
signal(SIGINT, SIG_IGN);
- shmdt(buf);
+ shmdt(shbuf);
exit(0);
}
@@ -66,79 +65,105 @@ int logread_main(int argc, char **argv)
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);
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);
}
diff --git a/sysklogd/syslogd.c b/sysklogd/syslogd.c
index 0ed16bc9e..6ecbd16f0 100644
--- a/sysklogd/syslogd.c
+++ b/sysklogd/syslogd.c
@@ -46,8 +46,7 @@ enum { MAX_READ = 256 };
/* Semaphore operation structures */
struct shbuf_ds {
- int32_t size; /* size of data written */
- int32_t head; /* start of message list */
+ int32_t size; /* size of data - 1 */
int32_t tail; /* end of message list */
char data[1]; /* data/messages */
};
@@ -212,8 +211,9 @@ static void ipcsyslog_init(void)
bb_perror_msg_and_die("shmat");
}
- G.shbuf->size = G.shm_size - offsetof(struct shbuf_ds, data);
- G.shbuf->head = G.shbuf->tail = 0;
+ memset(G.shbuf, 0, G.shm_size);
+ G.shbuf->size = G.shm_size - offsetof(struct shbuf_ds, data) - 1;
+ /*G.shbuf->tail = 0;*/
// we'll trust the OS to set initial semval to 0 (let's hope)
G.s_semid = semget(KEY_ID, 2, IPC_CREAT | IPC_EXCL | 1023);
@@ -231,7 +231,6 @@ static void ipcsyslog_init(void)
static void log_to_shmem(const char *msg, int len)
{
int old_tail, new_tail;
- char *c;
if (semop(G.s_semid, G.SMwdn, 3) == -1) {
bb_perror_msg_and_die("SMwdn");
@@ -240,49 +239,20 @@ static void log_to_shmem(const char *msg, int len)
/* Circular Buffer Algorithm:
* --------------------------
* tail == position where to store next syslog message.
- * head == position of next message to retrieve ("print").
- * if head == tail, there is no "unprinted" messages left.
- * head is typically advanced by separate "reader" program,
- * but if there isn't one, we have to do it ourself.
- * messages are NUL-separated.
+ * tail's max value is (shbuf->size - 1)
+ * Last byte of buffer is never used and remains NUL.
*/
len++; /* length with NUL included */
again:
old_tail = G.shbuf->tail;
new_tail = old_tail + len;
if (new_tail < G.shbuf->size) {
- /* No need to move head if shbuf->head <= old_tail,
- * else... */
- if (old_tail < G.shbuf->head && G.shbuf->head <= new_tail) {
- /* ...need to move head forward */
- c = memchr(G.shbuf->data + new_tail, '\0',
- G.shbuf->size - new_tail);
- if (!c) /* no NUL ahead of us, wrap around */
- c = memchr(G.shbuf->data, '\0', old_tail);
- if (!c) { /* still nothing? point to this msg... */
- G.shbuf->head = old_tail;
- } else {
- /* convert pointer to offset + skip NUL */
- G.shbuf->head = c - G.shbuf->data + 1;
- }
- }
/* store message, set new tail */
memcpy(G.shbuf->data + old_tail, msg, len);
G.shbuf->tail = new_tail;
} else {
- /* we need to break up the message and wrap it around */
/* k == available buffer space ahead of old tail */
- int k = G.shbuf->size - old_tail - 1;
- if (G.shbuf->head > old_tail) {
- /* we are going to overwrite head, need to
- * move it out of the way */
- c = memchr(G.shbuf->data, '\0', old_tail);
- if (!c) { /* nothing? point to this msg... */
- G.shbuf->head = old_tail;
- } else { /* convert pointer to offset + skip NUL */
- G.shbuf->head = c - G.shbuf->data + 1;
- }
- }
+ int k = G.shbuf->size - old_tail;
/* copy what fits to the end of buffer, and repeat */
memcpy(G.shbuf->data + old_tail, msg, k);
msg += k;
@@ -294,7 +264,7 @@ static void log_to_shmem(const char *msg, int len)
bb_perror_msg_and_die("SMwup");
}
if (DEBUG)
- printf("head:%d tail:%d\n", G.shbuf->head, G.shbuf->tail);
+ printf("tail:%d\n", G.shbuf->tail);
}
#else
void ipcsyslog_cleanup(void);
@@ -339,11 +309,10 @@ static void log_locally(char *msg)
}
#if ENABLE_FEATURE_ROTATE_LOGFILE
{
- struct stat statf;
-
- G.isRegular = (fstat(G.logFD, &statf) == 0 && (statf.st_mode & S_IFREG));
- /* bug (mostly harmless): can wrap around if file > 4gb */
- G.curFileSize = statf.st_size;
+ struct stat statf;
+ G.isRegular = (fstat(G.logFD, &statf) == 0 && S_ISREG(statf.st_mode));
+ /* bug (mostly harmless): can wrap around if file > 4gb */
+ G.curFileSize = statf.st_size;
}
#endif
}