From: Denis Vlasenko Date: Sun, 12 Aug 2007 21:33:06 +0000 (-0000) Subject: syslogd,logread: get rid of head pointer, fix logread bug in the process X-Git-Tag: 1_7_0~58 X-Git-Url: https://git.librecmc.org/?a=commitdiff_plain;h=5f1b149d541ebba7cab841cb647f113248f9fb8f;p=oweals%2Fbusybox.git 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 --- 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(""); } - // 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 }