syslog.cpp revision b1b60c30bf321c0fc02264b953b5c16c49d34457 
1/*
2 * Copyright (C) 2014 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 <stdlib.h>
19#include <syslog.h>
20
21#include "private/libc_logging.h"
22
23static const char* syslog_log_tag = NULL;
24static int syslog_priority_mask = 0xff;
25
26void closelog() {
27  syslog_log_tag = NULL;
28}
29
30void openlog(const char* log_tag, int /*options*/, int /*facility*/) {
31  syslog_log_tag = log_tag;
32}
33
34int setlogmask(int new_mask) {
35  int old_mask = syslog_priority_mask;
36  // 0 is used to query the current mask.
37  if (new_mask != 0) {
38    syslog_priority_mask = new_mask;
39  }
40  return old_mask;
41}
42
43void syslog(int priority, const char* fmt, ...) {
44  va_list args;
45  va_start(args, fmt);
46  vsyslog(priority, fmt, args);
47  va_end(args);
48}
49
50void vsyslog(int priority, const char* fmt, va_list args) {
51  int caller_errno = errno;
52
53  // Check whether we're supposed to be logging messages of this priority.
54  if ((syslog_priority_mask & LOG_MASK(LOG_PRI(priority))) == 0) {
55    return;
56  }
57
58  // What's our log tag?
59  const char* log_tag = syslog_log_tag;
60  if (log_tag == NULL) {
61    log_tag = getprogname();
62  }
63
64  // What's our Android log priority?
65  priority &= LOG_PRIMASK;
66  int android_log_priority;
67  if (priority <= LOG_ERR) {
68    android_log_priority = ANDROID_LOG_ERROR;
69  } else if (priority == LOG_WARNING) {
70    android_log_priority = ANDROID_LOG_WARN;
71  } else if (priority <= LOG_INFO) {
72    android_log_priority = ANDROID_LOG_INFO;
73  } else {
74    android_log_priority = ANDROID_LOG_DEBUG;
75  }
76
77  // glibc's printf family support %m directly, but our BSD-based one doesn't.
78  // If the format string seems to contain "%m", rewrite it.
79  const char* log_fmt = fmt;
80  if (strstr(fmt, "%m") != NULL) {
81    size_t dst_len = 1024;
82    char* dst = reinterpret_cast<char*>(malloc(dst_len));
83    log_fmt = dst;
84
85    const char* src = fmt;
86    for (; dst_len > 0 && *src != '\0'; ++src) {
87      if (*src == '%' && *(src + 1) == 'm') {
88        // Expand %m.
89        size_t n = strlcpy(dst, strerror(caller_errno), dst_len);
90        if (n >= dst_len) {
91          n = dst_len;
92        }
93        dst += n;
94        dst_len -= n;
95        ++src;
96      } else if (*src == '%' && *(src + 1) == '%') {
97        // We need to copy pairs of '%'s so the %m test works.
98        if (dst_len <= 2) {
99          break;
100        }
101        *dst++ = '%'; --dst_len;
102        *dst++ = '%'; --dst_len;
103        ++src;
104      } else {
105        *dst++ = *src; --dst_len;
106      }
107    }
108    *dst = '\0';
109  }
110
111  // We can't let __libc_format_log do the formatting because it doesn't support
112  // all the printf functionality.
113  char log_line[1024];
114  vsnprintf(log_line, sizeof(log_line), log_fmt, args);
115
116  if (log_fmt != fmt) {
117    free(const_cast<char*>(log_fmt));
118  }
119
120  __libc_format_log(android_log_priority, log_tag, "%s", log_line);
121}
122