xen-store: support XenStore access through /dev/xen/xenbus

coverage_config_x86_64.json

@@ -1,5 +1,5 @@
 {
-  "coverage_score": 18.62,
+  "coverage_score": 28.58,
   "exclude_path": "oxerun",
   "crate_features": ""
 }

xen-store/Cargo.toml

@@ -11,5 +11,4 @@ edition = "2018"
 [dependencies]
 libc = ">=0.2.95"
 vmm-sys-util = ">=0.9.0"
-nix = "0.24.1"
 xen-bindings = { path = "../xen-bindings" }

xen-store/src/types.rs

@@ -10,9 +10,8 @@
 
 use std::io;
 
-use nix::libc::{iovec, E2BIG};
-
 pub const XENSTORED_SOCKET: &str = "/var/run/xenstored/socket";
+pub const XENBUS_DEVICE: &str = "/dev/xen/xenbus";
 pub const XENSTORE_PAYLOAD_MAX: u32 = 4096;
 
 #[repr(C)]
@@ -26,21 +25,18 @@ pub(crate) struct XenSocketMessage {
 }
 
 impl XenSocketMessage {
-    #[allow(clippy::ptr_arg)]
-    pub(crate) fn new(r#type: u32, iovec_buffers: &mut Vec<iovec>) -> Result<Self, std::io::Error> {
+    pub(crate) fn new(r#type: u32, payload_len: usize) -> Result<Self, std::io::Error> {
+        if payload_len > XENSTORE_PAYLOAD_MAX as usize {
+            return Err(io::Error::from_raw_os_error(libc::E2BIG));
+        }
+
         let msg = XenSocketMessage {
             r#type,
             req_id: 0,
             tx_id: 0,
-            len: iovec_buffers
-                .iter()
-                .fold(0, |acc, iovec| acc + iovec.iov_len as u32),
+            len: payload_len as u32,
         };
 
-        if msg.len > XENSTORE_PAYLOAD_MAX {
-            return Err(io::Error::from_raw_os_error(E2BIG));
-        }
-
         Ok(msg)
     }
 }