aarch64: support runtime loading/linking of crates (theseus-os#940)

* Implemented all relocation types that appear in current aarch64 builds
  as well as the overflow checks for those relocation types.

* Note that `loadable` mode fully works, but will hang due to a bug
  in the `multicore_bringup` logic on aarch64. If you modify the arm_board's
  QEMU configuration to use just a single CPU, that will bypass the bug
  and result in the system fully booting. 
  * A PR to fix that is coming soon.

* The following crates were modified to work on aarch64 loadable mode:
  * `panic_entry`, `panic_wrapper`:  don't start unwinding,
    which isn't yet supported on aarch64.
  * `console`: undo arch-specific changes)
  * `first_application`: run a sample hello world app,
    as the full `shell` isn't yet supported on aarch64.

* Split x86_64 and aarch64 relocations into separate functions.

* Ensure `hull` is always built when the `console` is built,
  as the console directly spawns a new instance of it.

Author: kevinaboos

Cargo.lock

@@ -10,8 +10,8 @@ authors = ["Kevin Boos <kevinaboos@gmail.com>"]
 version = "0.4.8"
 
 
-[dependencies.app_io]
-path = "../../kernel/app_io"
+# [dependencies.app_io]
+# path = "../../kernel/app_io"
 
 # [dependencies.application_main_fn]
 # path = "../../compiler_plugins"

applications/hello/Cargo.toml

@@ -4,16 +4,11 @@
 
 
 extern crate alloc;
-// #[macro_use] extern crate log;
-#[macro_use] extern crate app_io;
-
-use alloc::vec::Vec;
-use alloc::string::String;
+// #[macro_use] extern crate app_io;
 
+use alloc::{string::String, vec::Vec};
 
 pub fn main(_args: Vec<String>) -> isize {
-    // info!("Hello, world! (from hello application)");
-    println!("Hello, world! Args: {:?}", _args);
-
+    log::info!("Hello, world! Args: {:?}", _args);
     0
 }

applications/hello/src/lib.rs

@@ -1,9 +1,12 @@
 {
   "abi": "softfloat",
   "arch": "aarch64",
+  "code-model": "large",
   "data-layout": "e-m:e-i8:8:32-i16:16:32-i64:64-i128:128-n32:64-S128",
   "disable-redzone": true,
+  "executables": true,
   "features": "+strict-align,-neon,-fp-armv8",
+  "has-thread-local": true,
   "linker": "rust-lld",
   "linker-flavor": "ld.lld",
   "llvm-target": "aarch64-unknown-none-elf",

cfg/aarch64-unknown-theseus.json

@@ -28,10 +28,10 @@ stack = { path = "../stack" }
 task = { path = "../task" }
 cpu = { path = "../cpu" }
 per_cpu = { path = "../per_cpu" }
+first_application = { path = "../first_application" }
 
 [target.'cfg(target_arch = "x86_64")'.dependencies]
 window_manager = { path = "../window_manager" }
-first_application = { path = "../first_application" }
 exceptions_full = { path = "../exceptions_full" }
 multiple_heaps = { path = "../multiple_heaps" }
 tsc = { path = "../tsc" }

kernel/captain/Cargo.toml

@@ -206,10 +206,6 @@ pub fn init(
     console::start_connection_detection()?;
 
     // 3. Start the first application(s).
-    // arch-gate: many subsystems required by applications are missing
-    // on aarch64: windowing, user input, app loading (relocation code
-    // is x86_64-specific at the moment)
-    #[cfg(target_arch = "x86_64")]
     first_application::start()?;
 
     info!("captain::init(): initialization done! Spawning an idle task on BSP core {} and enabling interrupts...", bsp_id);

kernel/captain/src/lib.rs

@@ -10,20 +10,21 @@ log = "0.4.8"
 irq_safety = { git = "https://github.com/theseus-os/irq_safety" }
 core2 = { version = "0.4.0", default-features = false, features = ["alloc", "nightly"] }
 
+app_io = { path = "../app_io" }
 async_channel = { path = "../async_channel" }
+io = { path = "../io" }
+mod_mgmt = { path = "../mod_mgmt" }
+path = { path = "../path" }
 serial_port = { path = "../serial_port" }
-app_io = { path = "../app_io" }
 spawn = { path = "../spawn" }
 task = { path = "../task" }
 tty = { path = "../tty" }
-io = { path = "../io" }
 
-[target.'cfg(target_arch = "x86_64")'.dependencies]
-path = { path = "../path" }
-mod_mgmt = { path = "../mod_mgmt" }
-
-[target.'cfg(target_arch = "aarch64")'.dependencies]
+## In general, Theseus kernel crates *cannot* depend on application crates.
+## However, this crate loads and runs the `hull` shell application,
+## so it's best to ensure that the `hull` crate is always included in the build
+## by specifying it as a direct dependency here.
+##
+## Note that this does NOT result in a direct runtime dependency
+## from this crate to the `hull` crate; it merely guarantees it gets built.
 hull = { path = "../../applications/hull" }
-
-[lib]
-crate-type = ["rlib"]

kernel/console/Cargo.toml

@@ -110,26 +110,17 @@ fn shell_loop(
         .spawn()?;
 
 
-    let task;
-    #[cfg(target_arch = "x86_64")] {
-        let new_app_ns = mod_mgmt::create_application_namespace(None)?;
-
-        let (app_file, _ns) =
-            mod_mgmt::CrateNamespace::get_crate_object_file_starting_with(&new_app_ns, "hull-")
-                .expect("Couldn't find shell in default app namespace");
-
-        let path = path::Path::new(app_file.lock().get_absolute_path());
-        task = spawn::new_application_task_builder(path, Some(new_app_ns))?
-            .name(format!("{address:?}_shell"))
-            .block()
-            .spawn()?;
-    }
-    #[cfg(target_arch = "aarch64")] {
-        task = spawn::new_task_builder(hull::main, alloc::vec::Vec::new())
-            .name(alloc::format!("{address:?}_shell"))
-            .block()
-            .spawn()?;
-    }
+    let new_app_ns = mod_mgmt::create_application_namespace(None)?;
+
+    let (app_file, _ns) =
+        mod_mgmt::CrateNamespace::get_crate_object_file_starting_with(&new_app_ns, "hull-")
+            .expect("Couldn't find hull in default app namespace");
+
+    let path = path::Path::new(app_file.lock().get_absolute_path());
+    let task = spawn::new_application_task_builder(path, Some(new_app_ns))?
+        .name(format!("{address:?}_hull"))
+        .block()
+        .spawn()?;
 
     let id = task.id;
     let stream = Arc::new(tty.slave());
@@ -143,7 +134,7 @@ fn shell_loop(
         },
     );
 
-    task.unblock().map_err(|_| "couldn't unblock shell task")?;
+    task.unblock().map_err(|_| "couldn't unblock hull task")?;
     task.join()?;
 
     reader_task.kill(KillReason::Requested).unwrap();