Contents of /tags/mkinitrd-6_1_8/busybox/sysklogd/logread.c
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Wed Oct 28 00:17:50 2009 UTC (14 years, 11 months ago) by niro
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File size: 4628 byte(s)
Wed Oct 28 00:17:50 2009 UTC (14 years, 11 months ago) by niro
File MIME type: text/plain
File size: 4628 byte(s)
tagged 'mkinitrd-6_1_8'
1 | /* vi: set sw=4 ts=4: */ |
2 | /* |
3 | * circular buffer syslog implementation for busybox |
4 | * |
5 | * Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com> |
6 | * |
7 | * Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001 |
8 | * |
9 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details. |
10 | */ |
11 | |
12 | #include "libbb.h" |
13 | #include <sys/ipc.h> |
14 | #include <sys/sem.h> |
15 | #include <sys/shm.h> |
16 | |
17 | #define DEBUG 0 |
18 | |
19 | /* our shared key (syslogd.c and logread.c must be in sync) */ |
20 | enum { KEY_ID = 0x414e4547 }; /* "GENA" */ |
21 | |
22 | struct shbuf_ds { |
23 | int32_t size; // size of data - 1 |
24 | int32_t tail; // end of message list |
25 | char data[1]; // messages |
26 | }; |
27 | |
28 | static const struct sembuf init_sem[3] = { |
29 | {0, -1, IPC_NOWAIT | SEM_UNDO}, |
30 | {1, 0}, {0, +1, SEM_UNDO} |
31 | }; |
32 | |
33 | struct globals { |
34 | struct sembuf SMrup[1]; // {0, -1, IPC_NOWAIT | SEM_UNDO}, |
35 | struct sembuf SMrdn[2]; // {1, 0}, {0, +1, SEM_UNDO} |
36 | struct shbuf_ds *shbuf; |
37 | }; |
38 | #define G (*(struct globals*)&bb_common_bufsiz1) |
39 | #define SMrup (G.SMrup) |
40 | #define SMrdn (G.SMrdn) |
41 | #define shbuf (G.shbuf) |
42 | #define INIT_G() do { \ |
43 | memcpy(SMrup, init_sem, sizeof(init_sem)); \ |
44 | } while (0) |
45 | |
46 | static void error_exit(const char *str) NORETURN; |
47 | static void error_exit(const char *str) |
48 | { |
49 | //release all acquired resources |
50 | shmdt(shbuf); |
51 | bb_perror_msg_and_die(str); |
52 | } |
53 | |
54 | /* |
55 | * sem_up - up()'s a semaphore. |
56 | */ |
57 | static void sem_up(int semid) |
58 | { |
59 | if (semop(semid, SMrup, 1) == -1) |
60 | error_exit("semop[SMrup]"); |
61 | } |
62 | |
63 | static void interrupted(int sig UNUSED_PARAM) |
64 | { |
65 | signal(SIGINT, SIG_IGN); |
66 | shmdt(shbuf); |
67 | exit(EXIT_SUCCESS); |
68 | } |
69 | |
70 | int logread_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
71 | int logread_main(int argc UNUSED_PARAM, char **argv) |
72 | { |
73 | unsigned cur; |
74 | int log_semid; /* ipc semaphore id */ |
75 | int log_shmid; /* ipc shared memory id */ |
76 | smallint follow = getopt32(argv, "f"); |
77 | |
78 | INIT_G(); |
79 | |
80 | log_shmid = shmget(KEY_ID, 0, 0); |
81 | if (log_shmid == -1) |
82 | bb_perror_msg_and_die("can't find syslogd buffer"); |
83 | |
84 | /* Attach shared memory to our char* */ |
85 | shbuf = shmat(log_shmid, NULL, SHM_RDONLY); |
86 | if (shbuf == NULL) |
87 | bb_perror_msg_and_die("can't access syslogd buffer"); |
88 | |
89 | log_semid = semget(KEY_ID, 0, 0); |
90 | if (log_semid == -1) |
91 | error_exit("can't get access to semaphores for syslogd buffer"); |
92 | |
93 | signal(SIGINT, interrupted); |
94 | |
95 | /* Suppose atomic memory read */ |
96 | /* Max possible value for tail is shbuf->size - 1 */ |
97 | cur = shbuf->tail; |
98 | |
99 | /* Loop for logread -f, one pass if there was no -f */ |
100 | do { |
101 | unsigned shbuf_size; |
102 | unsigned shbuf_tail; |
103 | const char *shbuf_data; |
104 | #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING |
105 | int i; |
106 | int len_first_part; |
107 | int len_total = len_total; /* for gcc */ |
108 | char *copy = copy; /* for gcc */ |
109 | #endif |
110 | if (semop(log_semid, SMrdn, 2) == -1) |
111 | error_exit("semop[SMrdn]"); |
112 | |
113 | /* Copy the info, helps gcc to realize that it doesn't change */ |
114 | shbuf_size = shbuf->size; |
115 | shbuf_tail = shbuf->tail; |
116 | shbuf_data = shbuf->data; /* pointer! */ |
117 | |
118 | if (DEBUG) |
119 | printf("cur:%d tail:%i size:%i\n", |
120 | cur, shbuf_tail, shbuf_size); |
121 | |
122 | if (!follow) { |
123 | /* advance to oldest complete message */ |
124 | /* find NUL */ |
125 | cur += strlen(shbuf_data + cur); |
126 | if (cur >= shbuf_size) { /* last byte in buffer? */ |
127 | cur = strnlen(shbuf_data, shbuf_tail); |
128 | if (cur == shbuf_tail) |
129 | goto unlock; /* no complete messages */ |
130 | } |
131 | /* advance to first byte of the message */ |
132 | cur++; |
133 | if (cur >= shbuf_size) /* last byte in buffer? */ |
134 | cur = 0; |
135 | } else { /* logread -f */ |
136 | if (cur == shbuf_tail) { |
137 | sem_up(log_semid); |
138 | fflush(stdout); |
139 | sleep(1); /* TODO: replace me with a sleep_on */ |
140 | continue; |
141 | } |
142 | } |
143 | |
144 | /* Read from cur to tail */ |
145 | #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING |
146 | len_first_part = len_total = shbuf_tail - cur; |
147 | if (len_total < 0) { |
148 | /* message wraps: */ |
149 | /* [SECOND PART.........FIRST PART] */ |
150 | /* ^data ^tail ^cur ^size */ |
151 | len_total += shbuf_size; |
152 | } |
153 | copy = xmalloc(len_total + 1); |
154 | if (len_first_part < 0) { |
155 | /* message wraps (see above) */ |
156 | len_first_part = shbuf_size - cur; |
157 | memcpy(copy + len_first_part, shbuf_data, shbuf_tail); |
158 | } |
159 | memcpy(copy, shbuf_data + cur, len_first_part); |
160 | copy[len_total] = '\0'; |
161 | cur = shbuf_tail; |
162 | #else |
163 | while (cur != shbuf_tail) { |
164 | fputs(shbuf_data + cur, stdout); |
165 | cur += strlen(shbuf_data + cur) + 1; |
166 | if (cur >= shbuf_size) |
167 | cur = 0; |
168 | } |
169 | #endif |
170 | unlock: |
171 | /* release the lock on the log chain */ |
172 | sem_up(log_semid); |
173 | |
174 | #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING |
175 | for (i = 0; i < len_total; i += strlen(copy + i) + 1) { |
176 | fputs(copy + i, stdout); |
177 | } |
178 | free(copy); |
179 | #endif |
180 | } while (follow); |
181 | |
182 | shmdt(shbuf); |
183 | |
184 | fflush_stdout_and_exit(EXIT_SUCCESS); |
185 | } |