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    Contents of /trunk/mkinitrd-magellan/busybox/sysklogd/logread.c

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    Revision 532 - (show annotations) (download)
    Sat Sep 1 22:45:15 2007 UTC (16 years, 8 months ago) by niro
    File MIME type: text/plain
    File size: 3371 byte(s) 
    -import if magellan mkinitrd; it is a fork of redhats mkinitrd-5.0.8 with all magellan patches and features; deprecates magellan-src/mkinitrd
    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 "busybox.h"
    13 #include <sys/ipc.h>
    14 #include <sys/sem.h>
    15 #include <sys/shm.h>
    16
    17 #define DEBUG 0
    18
    19 enum { KEY_ID = 0x414e4547 }; /* "GENA" */
    20
    21 static struct shbuf_ds {
    22 int32_t size; // size of data written
    23 int32_t head; // start of message list
    24 int32_t tail; // end of message list
    25 char data[1]; // data/messages
    26 } *buf; // shared memory pointer
    27
    28 // Semaphore operation structures
    29 static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
    30 static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
    31
    32
    33 static void error_exit(const char *str) ATTRIBUTE_NORETURN;
    34 static void error_exit(const char *str)
    35 {
    36 //release all acquired resources
    37 shmdt(buf);
    38 bb_perror_msg_and_die(str);
    39 }
    40
    41 /*
    42 * sem_up - up()'s a semaphore.
    43 */
    44 static void sem_up(int semid)
    45 {
    46 if (semop(semid, SMrup, 1) == -1)
    47 error_exit("semop[SMrup]");
    48 }
    49
    50 static void interrupted(int sig ATTRIBUTE_UNUSED)
    51 {
    52 signal(SIGINT, SIG_IGN);
    53 shmdt(buf);
    54 exit(0);
    55 }
    56
    57 int logread_main(int argc, char **argv)
    58 {
    59 int cur;
    60 int log_semid; /* ipc semaphore id */
    61 int log_shmid; /* ipc shared memory id */
    62 smallint follow = getopt32(argc, argv, "f");
    63
    64 log_shmid = shmget(KEY_ID, 0, 0);
    65 if (log_shmid == -1)
    66 bb_perror_msg_and_die("can't find syslogd buffer");
    67
    68 // Attach shared memory to our char*
    69 buf = shmat(log_shmid, NULL, SHM_RDONLY);
    70 if (buf == NULL)
    71 bb_perror_msg_and_die("can't access syslogd buffer");
    72
    73 log_semid = semget(KEY_ID, 0, 0);
    74 if (log_semid == -1)
    75 error_exit("can't get access to semaphores for syslogd buffer");
    76
    77 // attempt to redefine ^C signal
    78 signal(SIGINT, interrupted);
    79
    80 // Suppose atomic memory move
    81 cur = follow ? buf->tail : buf->head;
    82
    83 do {
    84 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
    85 char *buf_data;
    86 int log_len, j;
    87 #endif
    88 if (semop(log_semid, SMrdn, 2) == -1)
    89 error_exit("semop[SMrdn]");
    90
    91 if (DEBUG)
    92 printf("head:%i cur:%d tail:%i size:%i\n",
    93 buf->head, cur, buf->tail, buf->size);
    94
    95 if (buf->head == buf->tail || cur == buf->tail) {
    96 if (follow) {
    97 sem_up(log_semid);
    98 fflush(stdout);
    99 sleep(1); /* TODO: replace me with a sleep_on */
    100 continue;
    101 }
    102 puts("<empty syslog>");
    103 }
    104
    105 // Read Memory
    106 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
    107 log_len = buf->tail - cur;
    108 if (log_len < 0)
    109 log_len += buf->size;
    110 buf_data = xmalloc(log_len);
    111
    112 if (buf->tail >= cur)
    113 j = log_len;
    114 else
    115 j = buf->size - cur;
    116 memcpy(buf_data, buf->data + cur, j);
    117
    118 if (buf->tail < cur)
    119 memcpy(buf_data + buf->size - cur, buf->data, buf->tail);
    120 cur = buf->tail;
    121 #else
    122 while (cur != buf->tail) {
    123 fputs(buf->data + cur, stdout);
    124 cur += strlen(buf->data + cur) + 1;
    125 if (cur >= buf->size)
    126 cur = 0;
    127 }
    128 #endif
    129 // release the lock on the log chain
    130 sem_up(log_semid);
    131
    132 #if ENABLE_FEATURE_LOGREAD_REDUCED_LOCKING
    133 for (j = 0; j < log_len; j += strlen(buf_data+j) + 1) {
    134 fputs(buf_data + j, stdout);
    135 }
    136 free(buf_data);
    137 #endif
    138 } while (follow);
    139
    140 shmdt(buf);
    141
    142 fflush_stdout_and_exit(EXIT_SUCCESS);
    143 }