| //! Logger implementation for low level kernel log (using `/dev/kmsg`) |
| //! |
| //! Usually intended for low level implementations, like [systemd generators][1], |
| //! which have to use `/dev/kmsg`: |
| //! |
| //! > Since syslog is not available (see above) write log messages to /dev/kmsg instead. |
| //! |
| //! [1]: http://www.freedesktop.org/wiki/Software/systemd/Generators/ |
| //! |
| //! # Examples |
| //! |
| //! ```toml |
| //! [dependencies] |
| //! log = "0.4" |
| //! kernlog = "0.3" |
| //! ``` |
| //! |
| //! ```rust |
| //! #[macro_use] |
| //! extern crate log; |
| //! extern crate kernlog; |
| //! |
| //! fn main() { |
| //! kernlog::init().unwrap(); |
| //! warn!("something strange happened"); |
| //! } |
| //! ``` |
| //! Note you have to have permissions to write to `/dev/kmsg`, |
| //! which normal users (not root) usually don't. |
| //! |
| //! If compiled with nightly it can use libc feature to get process id |
| //! and report it into log. This feature is unavailable for stable release |
| //! for now. To enable nightly features, compile with `--features nightly`: |
| //! |
| //! ```toml |
| //! [dependencies.kernlog] |
| //! version = "*" |
| //! features = ["nightly"] |
| //! ``` |
| |
| #![deny(missing_docs)] |
| #![cfg_attr(feature="nightly", feature(libc))] |
| |
| #[macro_use] |
| extern crate log; |
| extern crate libc; |
| |
| use std::fs::{OpenOptions, File}; |
| use std::io::{Error, ErrorKind, Write, self}; |
| use std::sync::Mutex; |
| use std::env; |
| |
| use log::{Log, Metadata, Record, Level, LevelFilter, SetLoggerError}; |
| |
| /// Kernel logger implementation |
| pub struct KernelLog { |
| kmsg: Mutex<File>, |
| maxlevel: LevelFilter |
| } |
| |
| impl KernelLog { |
| /// Create new kernel logger |
| pub fn new() -> io::Result<KernelLog> { |
| KernelLog::with_level(LevelFilter::Trace) |
| } |
| |
| /// Create new kernel logger from `KERNLOG_LEVEL` environment variable |
| pub fn from_env() -> io::Result<KernelLog> { |
| match env::var("KERNLOG_LEVEL") { |
| Err(_) => KernelLog::new(), |
| Ok(s) => match s.parse() { |
| Ok(filter) => KernelLog::with_level(filter), |
| Err(_) => KernelLog::new(), |
| } |
| } |
| } |
| |
| #[cfg(not(target_os = "android"))] |
| fn open_kmsg() -> io::Result<File> { |
| OpenOptions::new().write(true).open("/dev/kmsg") |
| } |
| |
| #[cfg(target_os = "android")] |
| fn open_kmsg() -> io::Result<File> { |
| // In Android, a process normally doesn't have the permission to open /dev/kmsg. Instead it |
| // is opened by init (via `file /dev/kmsg w` in the rc file) and the file descriptor is |
| // shared when executing the process. The file descriptor number is passed via an |
| // environment variable "ANDROID_FILE_<file_name>" where <file_name> is the path to the |
| // file where non alpha-numeric characters are replaced with '_'. |
| match env::var("ANDROID_FILE__dev_kmsg") { |
| Ok(val) => OpenOptions::new().write(true).open(format!("/proc/self/fd/{}", val)), |
| Err(e) => Err(Error::new(ErrorKind::Other, "ANDROID_FILE__dev_kmsg doesn't exist")), |
| } |
| } |
| |
| /// Create new kernel logger with error level filter |
| pub fn with_level(filter: LevelFilter) -> io::Result<KernelLog> { |
| Ok(KernelLog { |
| kmsg: Mutex::new(Self::open_kmsg()?), |
| maxlevel: filter |
| }) |
| } |
| } |
| |
| impl Log for KernelLog { |
| fn enabled(&self, meta: &Metadata) -> bool { |
| meta.level() <= self.maxlevel |
| } |
| |
| fn log(&self, record: &Record) { |
| if record.level() > self.maxlevel { |
| return; |
| } |
| |
| let level: u8 = match record.level() { |
| Level::Error => 3, |
| Level::Warn => 4, |
| Level::Info => 5, |
| Level::Debug => 6, |
| Level::Trace => 7, |
| }; |
| |
| let mut buf = Vec::new(); |
| writeln!(buf, "<{}>{}[{}]: {}", level, record.target(), |
| unsafe { ::libc::getpid() }, |
| record.args()).unwrap(); |
| |
| if let Ok(mut kmsg) = self.kmsg.lock() { |
| let _ = kmsg.write(&buf); |
| let _ = kmsg.flush(); |
| } |
| } |
| |
| fn flush(&self) {} |
| } |
| |
| /// KernelLog initialization error |
| #[derive(Debug)] |
| pub enum KernelLogInitError { |
| /// IO error |
| Io(io::Error), |
| /// Set logger error |
| Log(SetLoggerError) |
| } |
| |
| impl std::fmt::Display for KernelLogInitError { |
| fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result { |
| match self { |
| KernelLogInitError::Io(err) => err.fmt(f), |
| KernelLogInitError::Log(err) => err.fmt(f), |
| } |
| } |
| } |
| |
| impl std::error::Error for KernelLogInitError { |
| fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { |
| match self { |
| KernelLogInitError::Io(err) => Some(err), |
| KernelLogInitError::Log(err) => Some(err), |
| } |
| } |
| } |
| |
| impl From<SetLoggerError> for KernelLogInitError { |
| fn from(err: SetLoggerError) -> Self { |
| KernelLogInitError::Log(err) |
| } |
| } |
| impl From<io::Error> for KernelLogInitError { |
| fn from(err: io::Error) -> Self { |
| KernelLogInitError::Io(err) |
| } |
| } |
| |
| /// Setup kernel logger as a default logger |
| pub fn init() -> Result<(), KernelLogInitError> { |
| let klog = KernelLog::from_env()?; |
| let maxlevel = klog.maxlevel; |
| log::set_boxed_logger(Box::new(klog))?; |
| log::set_max_level(maxlevel); |
| Ok(()) |
| } |
| |
| #[cfg(test)] |
| mod tests { |
| use super::{KernelLog, init}; |
| |
| #[test] |
| fn log_to_kernel() { |
| init().unwrap(); |
| debug!("hello, world!"); |
| } |
| } |