microsoft/openvmm
Publicmirrored fromhttps://github.com/microsoft/openvmmAvailable
petri/src/linux_direct_serial_agent.rs
81lines · modecode
| 1 | // Copyright (C) Microsoft Corporation. All rights reserved. |
| 2 | |
| 3 | use futures::AsyncReadExt; |
| 4 | use futures::AsyncWriteExt; |
| 5 | use pal_async::socket::ReadHalf; |
| 6 | use pal_async::socket::WriteHalf; |
| 7 | use unix_socket::UnixStream; |
| 8 | |
| 9 | const BUSYBOX_INIT: &str = |
| 10 | "/bin/busybox --install /bin && mount none /dev -t devtmpfs && mount none /proc -t proc && mount none /sys -t sysfs"; |
| 11 | |
| 12 | pub(crate) struct LinuxDirectSerialAgent { |
| 13 | /// Writer to serial 0, the console we define in our kernel commandline |
| 14 | write: WriteHalf<UnixStream>, |
| 15 | /// Reader on serial 1, not serial 0, to avoid reading the commands we just sent |
| 16 | read: ReadHalf<UnixStream>, |
| 17 | /// Delayed initialization so new can be synchronous |
| 18 | init: bool, |
| 19 | } |
| 20 | |
| 21 | impl LinuxDirectSerialAgent { |
| 22 | pub(crate) fn new( |
| 23 | serial1_read: ReadHalf<UnixStream>, |
| 24 | serial0_write: WriteHalf<UnixStream>, |
| 25 | ) -> Self { |
| 26 | Self { |
| 27 | read: serial1_read, |
| 28 | write: serial0_write, |
| 29 | init: false, |
| 30 | } |
| 31 | } |
| 32 | } |
| 33 | |
| 34 | impl LinuxDirectSerialAgent { |
| 35 | // Inform the agent that it should reinitialize itself on the next command. |
| 36 | pub(crate) fn reset(&mut self) { |
| 37 | self.init = false; |
| 38 | } |
| 39 | |
| 40 | pub(crate) async fn run_command(&mut self, command: &str) -> anyhow::Result<String> { |
| 41 | self.init_busybox_if_necessary().await?; |
| 42 | let bytes = self.run_command_core(command).await?; |
| 43 | Ok(String::from_utf8_lossy(&bytes).into_owned()) |
| 44 | } |
| 45 | |
| 46 | async fn run_command_core(&mut self, command: &str) -> anyhow::Result<Vec<u8>> { |
| 47 | // We need a signal that the current command has finished executing so that we can stop reading |
| 48 | // and return to the caller. The pipe will remain open, so we can't just read until we get 0 bytes. |
| 49 | // Instead we send this special text sequence to signal the end of the command, since it's unlikely |
| 50 | // that a normal command will ever output it. |
| 51 | const COMMAND_END_SIGNAL: &str = "== Petri Command Complete =="; |
| 52 | let command = format!("({command}) > /dev/ttyS1\necho {COMMAND_END_SIGNAL} > /dev/ttyS1\n"); |
| 53 | |
| 54 | // When reading the output there will be a trailing newline. |
| 55 | const COMMAND_END_SIGNAL_READ: &str = "== Petri Command Complete ==\r\n"; |
| 56 | |
| 57 | self.write.write_all(command.as_bytes()).await?; |
| 58 | |
| 59 | let mut output = Vec::new(); |
| 60 | let mut buf = [0u8; 1024]; |
| 61 | loop { |
| 62 | let n = self.read.read(&mut buf).await?; |
| 63 | tracing::debug!(buf = ?&buf[..n], "read serial bytes from guest"); |
| 64 | output.extend_from_slice(&buf[..n]); |
| 65 | if output.ends_with(COMMAND_END_SIGNAL_READ.as_bytes()) { |
| 66 | output.truncate(output.len() - COMMAND_END_SIGNAL_READ.len()); |
| 67 | break; |
| 68 | } |
| 69 | } |
| 70 | |
| 71 | Ok(output) |
| 72 | } |
| 73 | |
| 74 | async fn init_busybox_if_necessary(&mut self) -> anyhow::Result<()> { |
| 75 | if !self.init { |
| 76 | self.run_command_core(BUSYBOX_INIT).await?; |
| 77 | self.init = true; |
| 78 | }; |
| 79 | Ok(()) |
| 80 | } |
| 81 | } |
| 82 | |