Userspace support: Refactor init to launch a simple device model

Cargo.toml

@@ -24,6 +24,8 @@ members = [
     "user/lib",
     # Init user-space module
     "user/init",
+    # device model module
+    "user/dm",
     # Release version identifier
     "release",
 ]
@@ -41,6 +43,7 @@ syscall = { path = "syscall" }
 packit = { path = "packit" }
 userlib = { path = "user/lib" }
 userinit = { path = "user/init" }
+userdm = { path = "user/dm" }
 release = { path = "release" }
 
 # crates.io

configs/all-targets.json

@@ -53,6 +53,9 @@
         "modules": {
             "userinit": {
                 "path": "/init"
+            },
+            "userdm": {
+                "path": "/dm"
             }
         }
     }

configs/hyperv-target.json

@@ -35,6 +35,9 @@
         "modules": {
             "userinit": {
                 "path": "/init"
+            },
+            "userdm": {
+                "path": "/dm"
             }
         }
     }

configs/qemu-target.json

@@ -34,6 +34,9 @@
         "modules": {
             "userinit": {
                 "path": "/init"
+            },
+            "userdm": {
+                "path": "/dm"
             }
         }
     }

configs/vanadium-target.json

@@ -35,6 +35,9 @@
         "modules": {
             "userinit": {
                 "path": "/init"
+            },
+            "userdm": {
+                "path": "/dm"
             }
         }
     }

kernel/src/svsm.rs

@@ -323,7 +323,7 @@ pub extern "C" fn svsm_main() {
     virt_log_usage();
 
     if let Err(e) = SVSM_PLATFORM.launch_fw(&config) {
-        panic!("Failed to launch FW: {e:#?}");
+        panic!("Failed to launch FW: {e:?}");
     }
 
     start_kernel_task(request_processing_main, String::from("request-processing"))
@@ -339,7 +339,7 @@ pub extern "C" fn svsm_main() {
 
     match exec_user("/init", opendir("/").expect("Failed to find FS root")) {
         Ok(_) => (),
-        Err(e) => log::info!("Failed to launch /init: {e:#?}"),
+        Err(e) => log::info!("Failed to launch /init: {e:?}"),
     }
 
     request_loop();

kernel/src/syscall/class0.rs

@@ -14,7 +14,10 @@ use core::ffi::c_char;
 use syscall::SysCallError;
 
 pub fn sys_exit(exit_code: u32) -> ! {
-    log::info!("Terminating current task, exit_code {exit_code}");
+    log::info!(
+        "Terminating task {}, exit_code {exit_code}",
+        current_task().get_task_name()
+    );
     unsafe {
         current_task_terminated();
     }

kernel/src/task/exec.rs

@@ -51,7 +51,7 @@ fn task_name(binary: &str) -> String {
 ///
 /// # Returns
 ///
-/// `()` on success, [`SvsmError`] on failure.
+/// Returns [`Ok(tid)`] on success, [`Err(SvsmError)`] on failure.
 pub fn exec_user(binary: &str, root: Arc<dyn Directory>) -> Result<u32, SvsmError> {
     let fh = open_read(binary)?;
     let file_size = fh.size();

user/dm/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "userdm"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+userlib.workspace = true
+
+[lints]
+workspace = true

user/dm/build.rs

@@ -0,0 +1,4 @@
+fn main() {
+    println!("cargo:rustc-link-arg=-Tuser/lib/module.lds");
+    println!("cargo:rustc-link-arg=-no-pie");
+}

user/dm/src/main.rs

@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright (c) 2024 Intel Corporation.
+//
+// Author: Vijay Dhanraj <[email protected]>
+
+#![no_std]
+#![no_main]
+
+use userlib::*;
+
+declare_main!(main);
+
+fn main() -> u32 {
+    0
+}

user/init/src/main.rs

@@ -1,41 +1,49 @@
+// SPDX-License-Identifier: MIT
+//
+// Copyright (c) 2024 SUSE LLC
+//
+// Author: Joerg Roedel <[email protected]>
+
 #![no_std]
 #![no_main]
 
+use core::ffi::CStr;
 use userlib::*;
 
-use core::ptr::{addr_of, addr_of_mut};
-
-static mut SOME_BSS_DATA: [u64; 128] = [0; 128];
-static mut SOME_DATA: [u64; 128] = [0x01; 128];
-static SOME_RO_DATA: [u64; 128] = [0xee; 128];
-
-fn check(arr: &[u64; 128], val: u64) {
-    for v in arr.iter() {
-        if *v != val {
-            panic!("Unexpected array value");
-        }
-    }
-}
-
-fn write(arr: &mut [u64; 128], val: u64) {
-    for v in arr.iter_mut() {
-        *v = val;
-    }
-}
-
 declare_main!(main);
-
 fn main() -> u32 {
     println!("COCONUT-SVSM init process starting");
 
-    // SAFETY: Single-threaded process, so no data races. Safe to access global
-    // mutable data.
-    unsafe {
-        write(&mut *addr_of_mut!(SOME_DATA), 0xcc);
-        write(&mut *addr_of_mut!(SOME_BSS_DATA), 0xaa);
-        check(&*addr_of!(SOME_DATA), 0xccu64);
-        check(&*addr_of!(SOME_RO_DATA), 0xeeu64);
-        check(&*addr_of!(SOME_BSS_DATA), 0xaa);
+    let obj = opendir(c"/").expect("Cannot open root directory");
+
+    // Discover the first file under root directory, excluding `/init`.
+    let mut dirents: [DirEnt; 8] = Default::default();
+    let binfile = loop {
+        let n = readdir(&obj, &mut dirents).unwrap();
+        if let Some(f) = dirents
+            .iter()
+            .take(n)
+            .filter(|d| d.file_type == FileType::File)
+            .map(|d| {
+                CStr::from_bytes_until_nul(&d.file_name).expect("Filename is not nul-terminated!")
+            })
+            .find(|&f| f != c"init")
+        {
+            break f;
+        }
+        if n < dirents.len() {
+            return 0;
+        }
+    };
+
+    let mut path = [b'\0'; F_NAME_SIZE + 1];
+    path[0] = b'/';
+    path[1..=binfile.count_bytes()].copy_from_slice(binfile.to_bytes());
+    let file = CStr::from_bytes_until_nul(&path).unwrap();
+
+    match exec(file, c"/", 0) {
+        Ok(_) => 0,
+        Err(SysCallError::ENOTFOUND) => 1,
+        _ => panic!("{} launch failed", file.to_str().unwrap()),
     }
-    0
 }