1 files changed, 171 insertions, 0 deletions

diff --git a/sysklogd/logread.c b/sysklogd/logread.c
new file mode 100644
index 000000000..9cc6561a4
--- /dev/null
+++ b/sysklogd/logread.c
@@ -0,0 +1,171 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * circular buffer syslog implementation for busybox
+ *
+ * Copyright (C) 2000 by Gennady Feldman <gfeldman@gena01.com>
+ *
+ * Maintainer: Gennady Feldman <gfeldman@gena01.com> as of Mar 12, 2001
+ *
+ * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ */
+
+
+#include "busybox.h"
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ipc.h>
+#include <sys/types.h>
+#include <sys/sem.h>
+#include <sys/shm.h>
+#include <signal.h>
+#include <setjmp.h>
+#include <unistd.h>
+
+static const long KEY_ID = 0x414e4547; /*"GENA"*/
+
+static struct shbuf_ds {
+        int size;               // size of data written
+        int head;               // start of message list
+        int tail;               // end of message list
+        char data[1];           // data/messages
+} *buf = NULL;                  // shared memory pointer
+
+
+// Semaphore operation structures
+static struct sembuf SMrup[1] = {{0, -1, IPC_NOWAIT | SEM_UNDO}}; // set SMrup
+static struct sembuf SMrdn[2] = {{1, 0}, {0, +1, SEM_UNDO}}; // set SMrdn
+
+static int      log_shmid = -1; // ipc shared memory id
+static int      log_semid = -1; // ipc semaphore id
+static jmp_buf  jmp_env;
+
+static void error_exit(const char *str);
+static void interrupted(int sig);
+
+/*
+ * sem_up - up()'s a semaphore.
+ */
+static void sem_up(int semid)
+{
+        if ( semop(semid, SMrup, 1) == -1 )
+                error_exit("semop[SMrup]");
+}
+
+/*
+ * sem_down - down()'s a semaphore
+ */
+static void sem_down(int semid)
+{
+        if ( semop(semid, SMrdn, 2) == -1 )
+                error_exit("semop[SMrdn]");
+}
+
+int logread_main(int argc, char **argv)
+{
+        int i;
+        int follow=0;
+
+        if (argc == 2 && argv[1][0]=='-' && argv[1][1]=='f') {
+                follow = 1;
+        } else {
+                /* no options, no getopt */
+                if (argc > 1)
+                        bb_show_usage();
+        }
+
+        // handle interrupt signal
+        if (setjmp(jmp_env)) goto output_end;
+
+        // attempt to redefine ^C signal
+        signal(SIGINT, interrupted);
+
+        if ( (log_shmid = shmget(KEY_ID, 0, 0)) == -1)
+                error_exit("Can't find circular buffer");
+
+        // Attach shared memory to our char*
+        if ( (buf = shmat(log_shmid, NULL, SHM_RDONLY)) == NULL)
+                error_exit("Can't get access to circular buffer from syslogd");
+
+        if ( (log_semid = semget(KEY_ID, 0, 0)) == -1)
+                error_exit("Can't get access to semaphore(s) for circular buffer from syslogd");
+
+        // Suppose atomic memory move
+        i = follow ? buf->tail : buf->head;
+
+        do {
+#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
+                char *buf_data;
+                int log_len,j;
+#endif
+
+                sem_down(log_semid);
+
+                //printf("head: %i tail: %i size: %i\n",buf->head,buf->tail,buf->size);
+                if (buf->head == buf->tail || i==buf->tail) {
+                        if (follow) {
+                                sem_up(log_semid);
+                                sleep(1);       /* TODO: replace me with a sleep_on */
+                                continue;
+                        } else {
+                                printf("<empty syslog>\n");
+                        }
+                }
+
+                // Read Memory
+#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
+                log_len = buf->tail - i;
+                if (log_len < 0)
+                        log_len += buf->size;
+                buf_data = (char *)xmalloc(log_len);
+
+                if (buf->tail < i) {
+                        memcpy(buf_data, buf->data+i, buf->size-i);
+                        memcpy(buf_data+buf->size-i, buf->data, buf->tail);
+                } else {
+                        memcpy(buf_data, buf->data+i, buf->tail-i);
+                }
+                i = buf->tail;
+
+#else
+                while ( i != buf->tail) {
+                        printf("%s", buf->data+i);
+                        i+= strlen(buf->data+i) + 1;
+                        if (i >= buf->size )
+                                i=0;
+                }
+#endif
+                // release the lock on the log chain
+                sem_up(log_semid);
+
+#ifdef CONFIG_FEATURE_LOGREAD_REDUCED_LOCKING
+                for (j=0; j < log_len; j+=strlen(buf_data+j)+1) {
+                        printf("%s", buf_data+j);
+                        if (follow)
+                                fflush(stdout);
+                }
+                free(buf_data);
+#endif
+                fflush(stdout);
+        } while (follow);
+
+output_end:
+        if (log_shmid != -1)
+                shmdt(buf);
+
+        return EXIT_SUCCESS;
+}
+
+static void interrupted(int sig){
+        signal(SIGINT, SIG_IGN);
+        longjmp(jmp_env, 1);
+}
+
+static void error_exit(const char *str){
+        bb_perror_msg(str);
+        //release all acquired resources
+        if (log_shmid != -1)
+                shmdt(buf);
+
+        exit(1);
+}