1 /* vi: set sw=4 ts=4: */
3 * circular buffer syslog implementation for busybox
5 * Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com>
7 * Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
9 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
12 //usage:#define logread_trivial_usage
14 //usage:#define logread_full_usage "\n\n"
15 //usage: "Show messages in syslogd's circular buffer\n"
16 //usage: "\n -f Output data as log grows"
25 /* our shared key (syslogd.c and logread.c must be in sync) */
26 enum { KEY_ID
= 0x414e4547 }; /* "GENA" */
29 int32_t size
; // size of data - 1
30 int32_t tail
; // end of message list
31 char data
[1]; // messages
34 static const struct sembuf init_sem
[3] = {
35 {0, -1, IPC_NOWAIT
| SEM_UNDO
},
36 {1, 0}, {0, +1, SEM_UNDO
}
40 struct sembuf SMrup
[1]; // {0, -1, IPC_NOWAIT | SEM_UNDO},
41 struct sembuf SMrdn
[2]; // {1, 0}, {0, +1, SEM_UNDO}
42 struct shbuf_ds
*shbuf
;
44 #define G (*(struct globals*)&bb_common_bufsiz1)
45 #define SMrup (G.SMrup)
46 #define SMrdn (G.SMrdn)
47 #define shbuf (G.shbuf)
48 #define INIT_G() do { \
49 memcpy(SMrup, init_sem, sizeof(init_sem)); \
53 static void error_exit(const char *str
) NORETURN
;
54 static void error_exit(const char *str
)
56 /* Release all acquired resources */
58 bb_perror_msg_and_die(str
);
61 /* On Linux, shmdt is not mandatory on exit */
62 # define error_exit(str) bb_perror_msg_and_die(str)
66 * sem_up - up()'s a semaphore.
68 static void sem_up(int semid
)
70 if (semop(semid
, SMrup
, 1) == -1)
71 error_exit("semop[SMrup]");
74 static void interrupted(int sig
)
76 /* shmdt(shbuf); - on Linux, shmdt is not mandatory on exit */
77 kill_myself_with_sig(sig
);
80 int logread_main(int argc
, char **argv
) MAIN_EXTERNALLY_VISIBLE
;
81 int logread_main(int argc UNUSED_PARAM
, char **argv
)
84 int log_semid
; /* ipc semaphore id */
85 int log_shmid
; /* ipc shared memory id */
86 smallint follow
= getopt32(argv
, "f");
90 log_shmid
= shmget(KEY_ID
, 0, 0);
92 bb_perror_msg_and_die("can't %s syslogd buffer", "find");
94 /* Attach shared memory to our char* */
95 shbuf
= shmat(log_shmid
, NULL
, SHM_RDONLY
);
97 bb_perror_msg_and_die("can't %s syslogd buffer", "access");
99 log_semid
= semget(KEY_ID
, 0, 0);
101 error_exit("can't get access to semaphores for syslogd buffer");
103 bb_signals(BB_FATAL_SIGS
, interrupted
);
105 /* Suppose atomic memory read */
106 /* Max possible value for tail is shbuf->size - 1 */
109 /* Loop for logread -f, one pass if there was no -f */
113 const char *shbuf_data
;
114 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
117 int len_total
= len_total
; /* for gcc */
118 char *copy
= copy
; /* for gcc */
120 if (semop(log_semid
, SMrdn
, 2) == -1)
121 error_exit("semop[SMrdn]");
123 /* Copy the info, helps gcc to realize that it doesn't change */
124 shbuf_size
= shbuf
->size
;
125 shbuf_tail
= shbuf
->tail
;
126 shbuf_data
= shbuf
->data
; /* pointer! */
129 printf("cur:%u tail:%u size:%u\n",
130 cur
, shbuf_tail
, shbuf_size
);
133 /* advance to oldest complete message */
135 cur
+= strlen(shbuf_data
+ cur
);
136 if (cur
>= shbuf_size
) { /* last byte in buffer? */
137 cur
= strnlen(shbuf_data
, shbuf_tail
);
138 if (cur
== shbuf_tail
)
139 goto unlock
; /* no complete messages */
141 /* advance to first byte of the message */
143 if (cur
>= shbuf_size
) /* last byte in buffer? */
145 } else { /* logread -f */
146 if (cur
== shbuf_tail
) {
149 sleep(1); /* TODO: replace me with a sleep_on */
154 /* Read from cur to tail */
155 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
156 len_first_part
= len_total
= shbuf_tail
- cur
;
159 /* [SECOND PART.........FIRST PART] */
160 /* ^data ^tail ^cur ^size */
161 len_total
+= shbuf_size
;
163 copy
= xmalloc(len_total
+ 1);
164 if (len_first_part
< 0) {
165 /* message wraps (see above) */
166 len_first_part
= shbuf_size
- cur
;
167 memcpy(copy
+ len_first_part
, shbuf_data
, shbuf_tail
);
169 memcpy(copy
, shbuf_data
+ cur
, len_first_part
);
170 copy
[len_total
] = '\0';
173 while (cur
!= shbuf_tail
) {
174 fputs(shbuf_data
+ cur
, stdout
);
175 cur
+= strlen(shbuf_data
+ cur
) + 1;
176 if (cur
>= shbuf_size
)
181 /* release the lock on the log chain */
184 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
185 for (i
= 0; i
< len_total
; i
+= strlen(copy
+ i
) + 1) {
186 fputs(copy
+ i
, stdout
);
193 /* shmdt(shbuf); - on Linux, shmdt is not mandatory on exit */
195 fflush_stdout_and_exit(EXIT_SUCCESS
);