implement evtchn support

xenstore/Cargo.toml

@@ -0,0 +1,19 @@
+[package]
+name = "xenstore"
+version = "0.0.1"
+edition = "2021"
+resolver = "2"
+
+[lib]
+path = "src/lib.rs"
+
+[dependencies]
+libc = "0.2"
+
+[dependencies.bytemuck]
+version = "1.14.0"
+features = ["derive"]
+
+[[example]]
+name = "xenstore-ls"
+path = "examples/list.rs"

xenstore/examples/list.rs

@@ -0,0 +1,35 @@
+use xenstore::bus::XsdBusError;
+use xenstore::client::{XsdClient, XsdInterface};
+use xenstore::sys::XSD_ERROR_EINVAL;
+
+fn list_recursive(client: &mut XsdClient, level: usize, path: &str) -> Result<(), XsdBusError> {
+    let children = match client.list(path) {
+        Ok(children) => children,
+        Err(error) => {
+            return if error.to_string() == XSD_ERROR_EINVAL.error {
+                Ok(())
+            } else {
+                Err(error)
+            }
+        }
+    };
+
+    for child in children {
+        let full = format!("{}/{}", if path == "/" { "" } else { path }, child);
+        let value = client.read(full.as_str())?;
+        println!(
+            "{}{} = {:?}",
+            " ".repeat(level),
+            child,
+            String::from_utf8(value)?
+        );
+        list_recursive(client, level + 1, full.as_str())?;
+    }
+    Ok(())
+}
+
+fn main() -> Result<(), XsdBusError> {
+    let mut client = XsdClient::new()?;
+    list_recursive(&mut client, 0, "/")?;
+    Ok(())
+}

xenstore/src/bus.rs

@@ -0,0 +1,173 @@
+use crate::sys::{XsdMessageHeader, XSD_ERROR};
+use std::error::Error;
+use std::ffi::{CString, FromVecWithNulError, NulError};
+use std::fs::metadata;
+use std::io::{Read, Write};
+use std::mem::size_of;
+use std::net::Shutdown;
+use std::num::ParseIntError;
+use std::os::unix::net::UnixStream;
+use std::str::Utf8Error;
+use std::string::FromUtf8Error;
+
+const XEN_BUS_PATHS: &[&str] = &["/var/run/xenstored/socket"];
+
+fn find_bus_path() -> Option<String> {
+    for path in XEN_BUS_PATHS {
+        match metadata(path) {
+            Ok(_) => return Some(String::from(*path)),
+            Err(_) => continue,
+        }
+    }
+    None
+}
+
+#[derive(Debug)]
+pub struct XsdBusError {
+    message: String,
+}
+
+impl XsdBusError {
+    pub fn new(msg: &str) -> XsdBusError {
+        XsdBusError {
+            message: msg.to_string(),
+        }
+    }
+}
+
+impl std::fmt::Display for XsdBusError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(f, "{}", self.message)
+    }
+}
+
+impl Error for XsdBusError {
+    fn description(&self) -> &str {
+        &self.message
+    }
+}
+
+impl From<std::io::Error> for XsdBusError {
+    fn from(value: std::io::Error) -> Self {
+        XsdBusError::new(value.to_string().as_str())
+    }
+}
+
+impl From<NulError> for XsdBusError {
+    fn from(_: NulError) -> Self {
+        XsdBusError::new("Unable to coerce data into a C string.")
+    }
+}
+
+impl From<FromVecWithNulError> for XsdBusError {
+    fn from(_: FromVecWithNulError) -> Self {
+        XsdBusError::new("Unable to coerce data into a C string.")
+    }
+}
+
+impl From<Utf8Error> for XsdBusError {
+    fn from(_: Utf8Error) -> Self {
+        XsdBusError::new("Unable to coerce data into a UTF8 string.")
+    }
+}
+
+impl From<FromUtf8Error> for XsdBusError {
+    fn from(_: FromUtf8Error) -> Self {
+        XsdBusError::new("Unable to coerce data into a UTF8 string.")
+    }
+}
+
+impl From<ParseIntError> for XsdBusError {
+    fn from(_: ParseIntError) -> Self {
+        XsdBusError::new("Unable to coerce data into an integer.")
+    }
+}
+
+pub struct XsdSocket {
+    handle: UnixStream,
+}
+
+#[derive(Debug)]
+pub struct XsdResponse {
+    pub header: XsdMessageHeader,
+    pub payload: Vec<u8>,
+}
+
+impl XsdResponse {
+    pub fn parse_string(&self) -> Result<String, XsdBusError> {
+        Ok(String::from_utf8(self.payload.clone())?)
+    }
+
+    pub fn parse_string_vec(&self) -> Result<Vec<String>, XsdBusError> {
+        let mut strings: Vec<String> = Vec::new();
+        let mut buffer: Vec<u8> = Vec::new();
+        for b in &self.payload {
+            if *b == 0 {
+                let string = String::from_utf8(buffer.clone())?;
+                strings.push(string);
+                buffer.clear();
+                continue;
+            }
+            buffer.push(*b);
+        }
+        Ok(strings)
+    }
+
+    pub fn parse_bool(&self) -> Result<bool, XsdBusError> {
+        if self.payload.len() != 1 {
+            Err(XsdBusError::new("Expected payload to be a single byte."))
+        } else {
+            Ok(self.payload[0] == 0)
+        }
+    }
+}
+
+impl XsdSocket {
+    pub fn dial() -> Result<XsdSocket, XsdBusError> {
+        let path = match find_bus_path() {
+            Some(path) => path,
+            None => return Err(XsdBusError::new("Failed to find valid bus path.")),
+        };
+        let stream = UnixStream::connect(path)?;
+        Ok(XsdSocket { handle: stream })
+    }
+
+    pub fn send(&mut self, tx: u32, typ: u32, buf: &[u8]) -> Result<XsdResponse, XsdBusError> {
+        let header = XsdMessageHeader {
+            typ,
+            req: 0,
+            tx,
+            len: buf.len() as u32,
+        };
+        self.handle.write_all(bytemuck::bytes_of(&header))?;
+        self.handle.write_all(buf)?;
+        let mut result_buf = vec![0u8; size_of::<XsdMessageHeader>()];
+        self.handle.read_exact(result_buf.as_mut_slice())?;
+        let result_header = bytemuck::from_bytes::<XsdMessageHeader>(&result_buf);
+        let mut payload = vec![0u8; result_header.len as usize];
+        self.handle.read_exact(payload.as_mut_slice())?;
+        if result_header.typ == XSD_ERROR {
+            let error = CString::from_vec_with_nul(payload)?;
+            return Err(XsdBusError::new(error.to_str()?));
+        }
+        let response = XsdResponse { header, payload };
+        Ok(response)
+    }
+
+    pub fn send_single(
+        &mut self,
+        tx: u32,
+        typ: u32,
+        string: &str,
+    ) -> Result<XsdResponse, XsdBusError> {
+        let path = CString::new(string)?;
+        let buf = path.as_bytes_with_nul();
+        self.send(tx, typ, buf)
+    }
+}
+
+impl Drop for XsdSocket {
+    fn drop(&mut self) {
+        self.handle.shutdown(Shutdown::Both).unwrap()
+    }
+}

xenstore/src/client.rs

@@ -0,0 +1,126 @@
+use crate::bus::{XsdBusError, XsdSocket};
+use crate::sys::{
+    XSD_DIRECTORY, XSD_MKDIR, XSD_READ, XSD_RM, XSD_TRANSACTION_END, XSD_TRANSACTION_START,
+    XSD_WRITE,
+};
+use std::ffi::CString;
+
+pub struct XsdClient {
+    pub socket: XsdSocket,
+}
+
+pub trait XsdInterface {
+    fn list(&mut self, path: &str) -> Result<Vec<String>, XsdBusError>;
+    fn read(&mut self, path: &str) -> Result<Vec<u8>, XsdBusError>;
+    fn write(&mut self, path: &str, data: Vec<u8>) -> Result<bool, XsdBusError>;
+    fn mkdir(&mut self, path: &str) -> Result<bool, XsdBusError>;
+    fn rm(&mut self, path: &str) -> Result<bool, XsdBusError>;
+}
+
+impl XsdClient {
+    pub fn new() -> Result<XsdClient, XsdBusError> {
+        let socket = XsdSocket::dial()?;
+        Ok(XsdClient { socket })
+    }
+
+    fn list(&mut self, tx: u32, path: &str) -> Result<Vec<String>, XsdBusError> {
+        let response = self.socket.send_single(tx, XSD_DIRECTORY, path)?;
+        response.parse_string_vec()
+    }
+
+    fn read(&mut self, tx: u32, path: &str) -> Result<Vec<u8>, XsdBusError> {
+        let response = self.socket.send_single(tx, XSD_READ, path)?;
+        Ok(response.payload)
+    }
+
+    fn write(&mut self, tx: u32, path: &str, data: Vec<u8>) -> Result<bool, XsdBusError> {
+        let mut buffer = Vec::new();
+        let path = CString::new(path)?;
+        buffer.extend_from_slice(path.as_bytes_with_nul());
+        buffer.extend_from_slice(data.as_slice());
+        let response = self.socket.send(tx, XSD_WRITE, buffer.as_slice())?;
+        response.parse_bool()
+    }
+
+    fn mkdir(&mut self, tx: u32, path: &str) -> Result<bool, XsdBusError> {
+        self.socket.send_single(tx, XSD_MKDIR, path)?.parse_bool()
+    }
+
+    fn rm(&mut self, tx: u32, path: &str) -> Result<bool, XsdBusError> {
+        self.socket.send_single(tx, XSD_RM, path)?.parse_bool()
+    }
+
+    pub fn transaction(&mut self) -> Result<XsdTransaction, XsdBusError> {
+        let response = self.socket.send(0, XSD_TRANSACTION_START, &[])?;
+        let tx = response.parse_string()?.parse::<u32>()?;
+        Ok(XsdTransaction { client: self, tx })
+    }
+}
+
+pub struct XsdTransaction<'a> {
+    client: &'a mut XsdClient,
+    tx: u32,
+}
+
+impl XsdInterface for XsdClient {
+    fn list(&mut self, path: &str) -> Result<Vec<String>, XsdBusError> {
+        self.list(0, path)
+    }
+
+    fn read(&mut self, path: &str) -> Result<Vec<u8>, XsdBusError> {
+        self.read(0, path)
+    }
+
+    fn write(&mut self, path: &str, data: Vec<u8>) -> Result<bool, XsdBusError> {
+        self.write(0, path, data)
+    }
+
+    fn mkdir(&mut self, path: &str) -> Result<bool, XsdBusError> {
+        self.mkdir(0, path)
+    }
+
+    fn rm(&mut self, path: &str) -> Result<bool, XsdBusError> {
+        self.rm(0, path)
+    }
+}
+
+impl XsdInterface for XsdTransaction<'_> {
+    fn list(&mut self, path: &str) -> Result<Vec<String>, XsdBusError> {
+        self.client.list(self.tx, path)
+    }
+
+    fn read(&mut self, path: &str) -> Result<Vec<u8>, XsdBusError> {
+        self.client.read(self.tx, path)
+    }
+
+    fn write(&mut self, path: &str, data: Vec<u8>) -> Result<bool, XsdBusError> {
+        self.client.write(self.tx, path, data)
+    }
+
+    fn mkdir(&mut self, path: &str) -> Result<bool, XsdBusError> {
+        self.client.mkdir(self.tx, path)
+    }
+
+    fn rm(&mut self, path: &str) -> Result<bool, XsdBusError> {
+        self.client.rm(self.tx, path)
+    }
+}
+
+impl XsdTransaction<'_> {
+    pub fn end(&mut self, abort: bool) -> Result<bool, XsdBusError> {
+        let abort_str = if abort { "F" } else { "T" };
+
+        self.client
+            .socket
+            .send_single(self.tx, XSD_TRANSACTION_END, abort_str)?
+            .parse_bool()
+    }
+
+    pub fn commit(&mut self) -> Result<bool, XsdBusError> {
+        self.end(false)
+    }
+
+    pub fn abort(&mut self) -> Result<bool, XsdBusError> {
+        self.end(true)
+    }
+}

xenstore/src/lib.rs

@@ -0,0 +1,3 @@
+pub mod bus;
+pub mod client;
+pub mod sys;

xenstore/src/sys.rs

@@ -0,0 +1,141 @@
+use bytemuck::{Pod, Zeroable};
+/// Handwritten protocol definitions for XenStore.
+/// Used xen/include/public/io/xs_wire.h as a reference.
+use libc;
+
+#[derive(Copy, Clone, Pod, Zeroable, Debug)]
+#[repr(C)]
+pub struct XsdMessageHeader {
+    pub typ: u32,
+    pub req: u32,
+    pub tx: u32,
+    pub len: u32,
+}
+
+pub const XSD_CONTROL: u32 = 0;
+pub const XSD_DIRECTORY: u32 = 1;
+pub const XSD_READ: u32 = 2;
+pub const XSD_GET_PERMS: u32 = 3;
+pub const XSD_WATCH: u32 = 4;
+pub const XSD_UNWATCH: u32 = 5;
+pub const XSD_TRANSACTION_START: u32 = 6;
+pub const XSD_TRANSACTION_END: u32 = 7;
+pub const XSD_INTRODUCE: u32 = 8;
+pub const XSD_RELEASE: u32 = 9;
+pub const XSD_GET_DOMAIN_PATH: u32 = 10;
+pub const XSD_WRITE: u32 = 11;
+pub const XSD_MKDIR: u32 = 12;
+pub const XSD_RM: u32 = 13;
+pub const XSD_SET_PERMS: u32 = 14;
+pub const XSD_WATCH_EVENT: u32 = 15;
+pub const XSD_ERROR: u32 = 16;
+pub const XSD_IS_DOMAIN_INTRODUCED: u32 = 17;
+pub const XSD_RESUME: u32 = 18;
+pub const XSD_SET_TARGET: u32 = 19;
+pub const XSD_RESET_WATCHES: u32 = XSD_SET_TARGET + 2;
+pub const XSD_DIRECTORY_PART: u32 = 20;
+pub const XSD_TYPE_COUNT: u32 = 21;
+pub const XSD_INVALID: u32 = 0xffff;
+
+pub const XSD_WRITE_NONE: &str = "NONE";
+pub const XSD_WRITE_CREATE: &str = "CREATE";
+pub const XSD_WRITE_CREATE_EXCL: &str = "CREATE|EXCL";
+
+#[repr(C)]
+pub struct XsdError<'a> {
+    pub num: i32,
+    pub error: &'a str,
+}
+
+pub const XSD_ERROR_EINVAL: XsdError = XsdError {
+    num: libc::EINVAL,
+    error: "EINVAL",
+};
+pub const XSD_ERROR_EACCES: XsdError = XsdError {
+    num: libc::EACCES,
+    error: "EACCES",
+};
+pub const XSD_ERROR_EEXIST: XsdError = XsdError {
+    num: libc::EEXIST,
+    error: "EEXIST",
+};
+pub const XSD_ERROR_EISDIR: XsdError = XsdError {
+    num: libc::EISDIR,
+    error: "EISDIR",
+};
+pub const XSD_ERROR_ENOENT: XsdError = XsdError {
+    num: libc::ENOENT,
+    error: "ENOENT",
+};
+pub const XSD_ERROR_ENOMEM: XsdError = XsdError {
+    num: libc::ENOMEM,
+    error: "ENOMEM",
+};
+pub const XSD_ERROR_ENOSPC: XsdError = XsdError {
+    num: libc::ENOSPC,
+    error: "ENOSPC",
+};
+pub const XSD_ERROR_EIO: XsdError = XsdError {
+    num: libc::EIO,
+    error: "EIO",
+};
+pub const XSD_ERROR_ENOTEMPTY: XsdError = XsdError {
+    num: libc::ENOTEMPTY,
+    error: "ENOTEMPTY",
+};
+pub const XSD_ERROR_ENOSYS: XsdError = XsdError {
+    num: libc::ENOSYS,
+    error: "ENOSYS",
+};
+pub const XSD_ERROR_EROFS: XsdError = XsdError {
+    num: libc::EROFS,
+    error: "EROFS",
+};
+pub const XSD_ERROR_EBUSY: XsdError = XsdError {
+    num: libc::EBUSY,
+    error: "EBUSY",
+};
+pub const XSD_ERROR_EAGAIN: XsdError = XsdError {
+    num: libc::EAGAIN,
+    error: "EAGAIN",
+};
+pub const XSD_ERROR_EISCONN: XsdError = XsdError {
+    num: libc::EISCONN,
+    error: "EISCONN",
+};
+pub const XSD_ERROR_E2BIG: XsdError = XsdError {
+    num: libc::E2BIG,
+    error: "E2BIG",
+};
+pub const XSD_ERROR_EPERM: XsdError = XsdError {
+    num: libc::EPERM,
+    error: "EPERM",
+};
+
+pub const XSD_WATCH_PATH: u32 = 0;
+pub const XSD_WATCH_TOKEN: u32 = 1;
+
+#[repr(C)]
+pub struct XenDomainInterface {
+    req: [i8; 1024],
+    rsp: [i8; 1024],
+    req_cons: u32,
+    req_prod: u32,
+    rsp_cons: u32,
+    rsp_prod: u32,
+    server_features: u32,
+    connection: u32,
+    error: u32,
+}
+
+pub const XS_PAYLOAD_MAX: u32 = 4096;
+pub const XS_ABS_PATH_MAX: u32 = 3072;
+pub const XS_REL_PATH_MAX: u32 = 2048;
+pub const XS_SERVER_FEATURE_RECONNECTION: u32 = 1;
+pub const XS_SERVER_FEATURE_ERROR: u32 = 2;
+pub const XS_CONNECTED: u32 = 0;
+pub const XS_RECONNECT: u32 = 1;
+pub const XS_ERROR_NONE: u32 = 0;
+pub const XS_ERROR_COMM: u32 = 1;
+pub const XS_ERROR_RINGIDX: u32 = 2;
+pub const XS_ERROR_PROTO: u32 = 3;