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

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    Revision 532 - (hide 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 niro 532 /* 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     }