Jiyong Park | d7178e8 | 2021-06-22 16:47:17 +0900 | [diff] [blame] | 1 | //! Logger implementation for low level kernel log (using `/dev/kmsg`) |
| 2 | //! |
| 3 | //! Usually intended for low level implementations, like [systemd generators][1], |
| 4 | //! which have to use `/dev/kmsg`: |
| 5 | //! |
| 6 | //! > Since syslog is not available (see above) write log messages to /dev/kmsg instead. |
| 7 | //! |
| 8 | //! [1]: http://www.freedesktop.org/wiki/Software/systemd/Generators/ |
| 9 | //! |
| 10 | //! # Examples |
| 11 | //! |
| 12 | //! ```toml |
| 13 | //! [dependencies] |
| 14 | //! log = "0.4" |
| 15 | //! kernlog = "0.3" |
| 16 | //! ``` |
| 17 | //! |
| 18 | //! ```rust |
| 19 | //! #[macro_use] |
| 20 | //! extern crate log; |
| 21 | //! extern crate kernlog; |
| 22 | //! |
| 23 | //! fn main() { |
| 24 | //! kernlog::init().unwrap(); |
| 25 | //! warn!("something strange happened"); |
| 26 | //! } |
| 27 | //! ``` |
| 28 | //! Note you have to have permissions to write to `/dev/kmsg`, |
| 29 | //! which normal users (not root) usually don't. |
| 30 | //! |
| 31 | //! If compiled with nightly it can use libc feature to get process id |
| 32 | //! and report it into log. This feature is unavailable for stable release |
| 33 | //! for now. To enable nightly features, compile with `--features nightly`: |
| 34 | //! |
| 35 | //! ```toml |
| 36 | //! [dependencies.kernlog] |
| 37 | //! version = "*" |
| 38 | //! features = ["nightly"] |
| 39 | //! ``` |
| 40 | |
| 41 | #![deny(missing_docs)] |
| 42 | #![cfg_attr(feature="nightly", feature(libc))] |
| 43 | |
| 44 | #[macro_use] |
| 45 | extern crate log; |
| 46 | extern crate libc; |
| 47 | |
| 48 | use std::fs::{OpenOptions, File}; |
Jiyong Park | 39bcfd9 | 2021-06-26 00:31:25 +0900 | [diff] [blame] | 49 | use std::io::{Error, ErrorKind, Write, self}; |
Jiyong Park | d7178e8 | 2021-06-22 16:47:17 +0900 | [diff] [blame] | 50 | use std::sync::Mutex; |
| 51 | use std::env; |
| 52 | |
| 53 | use log::{Log, Metadata, Record, Level, LevelFilter, SetLoggerError}; |
| 54 | |
| 55 | /// Kernel logger implementation |
| 56 | pub struct KernelLog { |
| 57 | kmsg: Mutex<File>, |
| 58 | maxlevel: LevelFilter |
| 59 | } |
| 60 | |
| 61 | impl KernelLog { |
| 62 | /// Create new kernel logger |
| 63 | pub fn new() -> io::Result<KernelLog> { |
| 64 | KernelLog::with_level(LevelFilter::Trace) |
| 65 | } |
| 66 | |
| 67 | /// Create new kernel logger from `KERNLOG_LEVEL` environment variable |
| 68 | pub fn from_env() -> io::Result<KernelLog> { |
| 69 | match env::var("KERNLOG_LEVEL") { |
| 70 | Err(_) => KernelLog::new(), |
| 71 | Ok(s) => match s.parse() { |
| 72 | Ok(filter) => KernelLog::with_level(filter), |
| 73 | Err(_) => KernelLog::new(), |
| 74 | } |
| 75 | } |
| 76 | } |
| 77 | |
Jiyong Park | 39bcfd9 | 2021-06-26 00:31:25 +0900 | [diff] [blame] | 78 | #[cfg(not(target_os = "android"))] |
| 79 | fn open_kmsg() -> io::Result<File> { |
| 80 | OpenOptions::new().write(true).open("/dev/kmsg") |
| 81 | } |
| 82 | |
| 83 | #[cfg(target_os = "android")] |
| 84 | fn open_kmsg() -> io::Result<File> { |
| 85 | // In Android, a process normally doesn't have the permission to open /dev/kmsg. Instead it |
| 86 | // is opened by init (via `file /dev/kmsg w` in the rc file) and the file descriptor is |
| 87 | // shared when executing the process. The file descriptor number is passed via an |
| 88 | // environment variable "ANDROID_FILE_<file_name>" where <file_name> is the path to the |
| 89 | // file where non alpha-numeric characters are replaced with '_'. |
| 90 | match env::var("ANDROID_FILE__dev_kmsg") { |
| 91 | Ok(val) => OpenOptions::new().write(true).open(format!("/proc/self/fd/{}", val)), |
| 92 | Err(e) => Err(Error::new(ErrorKind::Other, "ANDROID_FILE__dev_kmsg doesn't exist")), |
| 93 | } |
| 94 | } |
| 95 | |
Jiyong Park | d7178e8 | 2021-06-22 16:47:17 +0900 | [diff] [blame] | 96 | /// Create new kernel logger with error level filter |
| 97 | pub fn with_level(filter: LevelFilter) -> io::Result<KernelLog> { |
| 98 | Ok(KernelLog { |
Jiyong Park | 39bcfd9 | 2021-06-26 00:31:25 +0900 | [diff] [blame] | 99 | kmsg: Mutex::new(Self::open_kmsg()?), |
Jiyong Park | d7178e8 | 2021-06-22 16:47:17 +0900 | [diff] [blame] | 100 | maxlevel: filter |
| 101 | }) |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | impl Log for KernelLog { |
| 106 | fn enabled(&self, meta: &Metadata) -> bool { |
| 107 | meta.level() <= self.maxlevel |
| 108 | } |
| 109 | |
| 110 | fn log(&self, record: &Record) { |
| 111 | if record.level() > self.maxlevel { |
| 112 | return; |
| 113 | } |
| 114 | |
| 115 | let level: u8 = match record.level() { |
| 116 | Level::Error => 3, |
| 117 | Level::Warn => 4, |
| 118 | Level::Info => 5, |
| 119 | Level::Debug => 6, |
| 120 | Level::Trace => 7, |
| 121 | }; |
| 122 | |
| 123 | let mut buf = Vec::new(); |
| 124 | writeln!(buf, "<{}>{}[{}]: {}", level, record.target(), |
| 125 | unsafe { ::libc::getpid() }, |
| 126 | record.args()).unwrap(); |
| 127 | |
| 128 | if let Ok(mut kmsg) = self.kmsg.lock() { |
| 129 | let _ = kmsg.write(&buf); |
| 130 | let _ = kmsg.flush(); |
| 131 | } |
| 132 | } |
| 133 | |
| 134 | fn flush(&self) {} |
| 135 | } |
| 136 | |
| 137 | /// KernelLog initialization error |
| 138 | #[derive(Debug)] |
| 139 | pub enum KernelLogInitError { |
| 140 | /// IO error |
| 141 | Io(io::Error), |
| 142 | /// Set logger error |
| 143 | Log(SetLoggerError) |
| 144 | } |
| 145 | |
| 146 | impl std::fmt::Display for KernelLogInitError { |
| 147 | fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { |
| 148 | match self { |
| 149 | KernelLogInitError::Io(err) => err.fmt(f), |
| 150 | KernelLogInitError::Log(err) => err.fmt(f), |
| 151 | } |
| 152 | } |
| 153 | } |
| 154 | |
| 155 | impl std::error::Error for KernelLogInitError { |
| 156 | fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { |
| 157 | match self { |
| 158 | KernelLogInitError::Io(err) => Some(err), |
| 159 | KernelLogInitError::Log(err) => Some(err), |
| 160 | } |
| 161 | } |
| 162 | } |
| 163 | |
| 164 | impl From<SetLoggerError> for KernelLogInitError { |
| 165 | fn from(err: SetLoggerError) -> Self { |
| 166 | KernelLogInitError::Log(err) |
| 167 | } |
| 168 | } |
| 169 | impl From<io::Error> for KernelLogInitError { |
| 170 | fn from(err: io::Error) -> Self { |
| 171 | KernelLogInitError::Io(err) |
| 172 | } |
| 173 | } |
| 174 | |
| 175 | /// Setup kernel logger as a default logger |
| 176 | pub fn init() -> Result<(), KernelLogInitError> { |
| 177 | let klog = KernelLog::from_env()?; |
| 178 | let maxlevel = klog.maxlevel; |
| 179 | log::set_boxed_logger(Box::new(klog))?; |
| 180 | log::set_max_level(maxlevel); |
| 181 | Ok(()) |
| 182 | } |
| 183 | |
| 184 | #[cfg(test)] |
| 185 | mod tests { |
| 186 | use super::{KernelLog, init}; |
| 187 | |
| 188 | #[test] |
| 189 | fn log_to_kernel() { |
| 190 | init().unwrap(); |
| 191 | debug!("hello, world!"); |
| 192 | } |
| 193 | } |