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// Copyright 2017 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
//! Runs hardware devices in child processes.
use std::fmt::{self, Display};
use std::io;
use std::os::unix::io::{AsRawFd, RawFd};
use std::time::Duration;
use io_jail::Minijail;
use libc::pid_t;
use msg_socket::{MsgReceiver, MsgSender, MsgSocket};
use sys_util::{error, net::UnixSeqpacket};
use crate::proxy::*;
use crate::BusDevice;
/// Errors for proxy devices.
#[derive(Debug)]
pub enum Error {
ForkingJail(io_jail::Error),
Io(io::Error),
}
pub type Result<T> = std::result::Result<T, Error>;
impl Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
use self::Error::*;
match self {
ForkingJail(e) => write!(f, "Failed to fork jail process: {}", e),
Io(e) => write!(f, "IO error configuring proxy device {}.", e),
}
}
}
const SOCKET_TIMEOUT_MS: u64 = 2000;
fn child_proc<D: BusDevice>(sock: UnixSeqpacket, device: &mut D) {
let mut running = true;
let sock = MsgSocket::<CommandResult, Command>::new(sock);
while running {
let cmd = match sock.recv() {
Ok(cmd) => cmd,
Err(err) => {
error!("child device process failed recv: {}", err);
break;
}
};
let res = match cmd {
Command::Read { len, offset } => {
let mut buffer = [0u8; 8];
device.read(offset, &mut buffer[0..len as usize]);
sock.send(&CommandResult::ReadResult(buffer))
}
Command::Write { len, offset, data } => {
let len = len as usize;
device.write(offset, &data[0..len]);
// Command::Write does not have a result.
Ok(())
}
Command::ReadConfig(idx) => {
let val = device.config_register_read(idx as usize);
sock.send(&CommandResult::ReadConfigResult(val))
}
Command::WriteConfig {
reg_idx,
offset,
len,
data,
} => {
let len = len as usize;
device.config_register_write(reg_idx as usize, offset as u64, &data[0..len]);
// Command::WriteConfig does not have a result.
Ok(())
}
Command::Shutdown => {
running = false;
sock.send(&CommandResult::Ok)
}
};
if let Err(e) = res {
error!("child device process failed send: {}", e);
}
}
}
pub struct JailInfo {
pid: pid_t,
sock: MsgSocket<Command, CommandResult>,
debug_label: String,
}
impl JailInfo {
pub fn pid(&self) -> pid_t {
self.pid
}
pub fn sock(&self) -> &MsgSocket<Command, CommandResult> {
&self.sock
}
pub fn debug_label(&self) -> &str {
self.debug_label.as_ref()
}
}
/// Takes the given device and isolates it into another process via fork before returning.
///
/// # Arguments
/// * `device` - The device to isolate to another process.
/// * `jail` - The jail to use for isolating the given device.
/// * `keep_fds` - File descriptors that will be kept open in the child.
pub fn jail_device<D: BusDevice>(
mut device: D,
jail: &Minijail,
mut keep_fds: Vec<RawFd>,
) -> Result<JailInfo> {
let debug_label = device.debug_label();
let (child_sock, parent_sock) = UnixSeqpacket::pair().map_err(Error::Io)?;
keep_fds.push(child_sock.as_raw_fd());
// Forking here is safe as long as the program is still single threaded.
let pid = unsafe {
match jail.fork(Some(&keep_fds)).map_err(Error::ForkingJail)? {
0 => {
device.on_sandboxed();
child_proc(child_sock, &mut device);
// We're explicitly not using std::process::exit here to avoid the cleanup of
// stdout/stderr globals. This can cause cascading panics and SIGILL if a worker
// thread attempts to log to stderr after at_exit handlers have been run.
// TODO(crbug.com/992494): Remove this once device shutdown ordering is clearly
// defined.
//
// exit() is trivially safe.
// ! Never returns
libc::exit(0);
}
p => p,
}
};
parent_sock
.set_write_timeout(Some(Duration::from_millis(SOCKET_TIMEOUT_MS)))
.map_err(Error::Io)?;
parent_sock
.set_read_timeout(Some(Duration::from_millis(SOCKET_TIMEOUT_MS)))
.map_err(Error::Io)?;
Ok(JailInfo {
sock: MsgSocket::<Command, CommandResult>::new(parent_sock),
pid,
debug_label,
})
}
pub struct JailedDevice {
proxy: ProxyDevice,
pid: pid_t,
}
impl JailedDevice {
pub fn jail<D: BusDevice>(device: D, jail: &Minijail, keep_fds: Vec<RawFd>) -> Result<Self> {
jail_device(device, jail, keep_fds).map(Self::new)
}
/// The forked process will automatically be terminated when this is dropped, so be sure to keep
/// a reference.
pub fn new(j: JailInfo) -> JailedDevice {
Self {
proxy: ProxyDevice::new(j.sock, j.debug_label),
pid: j.pid,
}
}
pub fn pid(&self) -> pid_t {
self.pid
}
}
impl BusDevice for JailedDevice {
fn debug_label(&self) -> String {
self.proxy.debug_label()
}
fn config_register_write(&mut self, reg_idx: usize, offset: u64, data: &[u8]) {
self.proxy.config_register_write(reg_idx, offset, data)
}
fn config_register_read(&self, reg_idx: usize) -> u32 {
self.proxy.config_register_read(reg_idx)
}
fn read(&mut self, offset: u64, data: &mut [u8]) {
self.proxy.read(offset, data)
}
fn write(&mut self, offset: u64, data: &[u8]) {
self.proxy.write(offset, data)
}
}
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