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      1 /*
      2  * Copyright (C) 2008 The Android Open Source Project
      3  *
      4  * Licensed under the Apache License, Version 2.0 (the "License");
      5  * you may not use this file except in compliance with the License.
      6  * You may obtain a copy of the License at
      7  *
      8  *      http://www.apache.org/licenses/LICENSE-2.0
      9  *
     10  * Unless required by applicable law or agreed to in writing, software
     11  * distributed under the License is distributed on an "AS IS" BASIS,
     12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     13  * See the License for the specific language governing permissions and
     14  * limitations under the License.
     15  */
     16 
     17 #include <errno.h>
     18 #include <fcntl.h>
     19 #include <stdarg.h>
     20 #include <stdio.h>
     21 #include <stdlib.h>
     22 #include <string.h>
     23 #include <sys/stat.h>
     24 #include <sys/types.h>
     25 #include <unistd.h>
     26 
     27 #include <cutils/klog.h>
     28 
     29 static int klog_fd = -1;
     30 static int klog_level = KLOG_DEFAULT_LEVEL;
     31 
     32 int klog_get_level(void) {
     33     return klog_level;
     34 }
     35 
     36 void klog_set_level(int level) {
     37     klog_level = level;
     38 }
     39 
     40 void klog_init(void) {
     41     if (klog_fd >= 0) return; /* Already initialized */
     42 
     43     klog_fd = open("/dev/kmsg", O_WRONLY | O_CLOEXEC);
     44     if (klog_fd >= 0) {
     45         return;
     46     }
     47 
     48     static const char* name = "/dev/__kmsg__";
     49     if (mknod(name, S_IFCHR | 0600, (1 << 8) | 11) == 0) {
     50         klog_fd = open(name, O_WRONLY | O_CLOEXEC);
     51         unlink(name);
     52     }
     53 }
     54 
     55 #define LOG_BUF_MAX 512
     56 
     57 void klog_writev(int level, const struct iovec* iov, int iov_count) {
     58     if (level > klog_level) return;
     59     if (klog_fd < 0) klog_init();
     60     if (klog_fd < 0) return;
     61     TEMP_FAILURE_RETRY(writev(klog_fd, iov, iov_count));
     62 }
     63 
     64 void klog_write(int level, const char* fmt, ...) {
     65     if (level > klog_level) return;
     66     char buf[LOG_BUF_MAX];
     67     va_list ap;
     68     va_start(ap, fmt);
     69     vsnprintf(buf, sizeof(buf), fmt, ap);
     70     va_end(ap);
     71 
     72     buf[LOG_BUF_MAX - 1] = 0;
     73 
     74     struct iovec iov[1];
     75     iov[0].iov_base = buf;
     76     iov[0].iov_len = strlen(buf);
     77     klog_writev(level, iov, 1);
     78 }
     79