kernel: proper type for static shared variables.

* Changed the KERNEL_CHANNEL_* to Mutex<T> with proper type, remove the
  need for unsafe.
* Exposed a const pointer to KernelImage, with UnsafeCell holding
  the library field for unbind with interior mutability.

src/runtime/src/kernel/core1.rs

@@ -1,6 +1,6 @@
 //! Kernel prologue/epilogue that runs on the 2nd CPU core
 
-use core::{mem, ptr};
+use core::{mem, ptr, cell::UnsafeCell};
 use alloc::borrow::ToOwned;
 use log::{debug, info, error};
 use cslice::CSlice;
@@ -9,7 +9,6 @@ use libcortex_a9::{
     enable_fpu,
     cache::{dcci_slice, iciallu, bpiall},
     asm::{dsb, isb},
-    sync_channel
 };
 use dyld::{self, Library};
 use crate::eh_artiq;
@@ -19,13 +18,10 @@ use super::{
     dma::init_dma,
     CHANNEL_0TO1, CHANNEL_1TO0,
     KERNEL_CHANNEL_0TO1, KERNEL_CHANNEL_1TO0,
-    KERNEL_LIBRARY,
+    KERNEL_IMAGE,
     Message,
 };
 
-/// will contain the kernel image address on the heap
-static mut KERNEL_LOAD_ADDR: usize = 0;
-
 unsafe fn attribute_writeback(typeinfo: *const ()) {
     struct Attr {
         offset: usize,
@@ -65,8 +61,8 @@ unsafe fn attribute_writeback(typeinfo: *const ()) {
     }
 }
 
-struct KernelImage {
-    library: Library,
+pub struct KernelImage {
+    library: UnsafeCell<Library>,
     __modinit__: u32,
     typeinfo: Option<u32>,
 }
@@ -89,21 +85,21 @@ impl KernelImage {
         }
 
         Ok(KernelImage {
-            library,
+            library: UnsafeCell::new(library),
             __modinit__,
             typeinfo,
         })
     }
 
-    pub fn get_library_ptr(&mut self) -> *mut Library {
-        &mut self.library as *mut Library
+    pub unsafe fn rebind(&self, name: &[u8], addr: *const ()) -> Result<(), dyld::Error> {
+        let library = self.library.get().as_mut().unwrap();
+        library.rebind(name, addr)
     }
 
-    pub unsafe fn exec(&mut self) {
+    pub unsafe fn exec(&self) {
         // Flush data cache entries for the image in DDR, including
         // Memory/Instruction Synchronization Barriers
-        dcci_slice(self.library.image.data);
-        dsb();
+        dcci_slice(self.library.get().as_ref().unwrap().image.data);
         iciallu();
         bpiall();
         dsb();
@@ -115,6 +111,12 @@ impl KernelImage {
             attribute_writeback(typeinfo as *const ());
         }
     }
+
+    pub fn get_load_addr(&self) -> usize {
+        unsafe {
+            self.library.get().as_ref().unwrap().image.as_ptr() as usize
+        }
+    }
 }
 
 #[no_mangle]
@@ -148,11 +150,7 @@ pub fn main_core1() {
                 let result = dyld::load(&data, &resolve)
                     .and_then(KernelImage::new);
                 match result {
-                    Ok(mut kernel) => {
-                        unsafe {
-                            KERNEL_LOAD_ADDR = kernel.library.image.as_ptr() as usize;
-                            KERNEL_LIBRARY = kernel.get_library_ptr();
-                        }
+                    Ok(kernel) => {
                         loaded_kernel = Some(kernel);
                         debug!("kernel loaded");
                         core1_tx.send(Message::LoadCompleted);
@@ -165,14 +163,16 @@ pub fn main_core1() {
             },
             Message::StartRequest => {
                 info!("kernel starting");
-                if let Some(mut kernel) = loaded_kernel.take() {
+                if let Some(kernel) = loaded_kernel.take() {
+                    core::mem::replace(&mut *KERNEL_CHANNEL_0TO1.lock(), Some(core1_rx));
+                    core::mem::replace(&mut *KERNEL_CHANNEL_1TO0.lock(), Some(core1_tx));
                     unsafe {
-                        KERNEL_CHANNEL_0TO1 = mem::transmute(&mut core1_rx);
-                        KERNEL_CHANNEL_1TO0 = mem::transmute(&mut core1_tx);
+                        KERNEL_IMAGE = &kernel as *const KernelImage;
                         kernel.exec();
-                        KERNEL_CHANNEL_0TO1 = ptr::null_mut();
-                        KERNEL_CHANNEL_1TO0 = ptr::null_mut();
+                        KERNEL_IMAGE = ptr::null();
                     }
+                    core1_rx = core::mem::replace(&mut *KERNEL_CHANNEL_0TO1.lock(), None).unwrap();
+                    core1_tx = core::mem::replace(&mut *KERNEL_CHANNEL_1TO0.lock(), None).unwrap();
                 }
                 info!("kernel finished");
                 core1_tx.send(Message::KernelFinished);
@@ -185,7 +185,7 @@ pub fn main_core1() {
 /// Called by eh_artiq
 pub fn terminate(exception: &'static eh_artiq::Exception<'static>, backtrace: &'static mut [usize]) -> ! {
     let load_addr = unsafe {
-        KERNEL_LOAD_ADDR
+        KERNEL_IMAGE.as_ref().unwrap().get_load_addr()
     };
     let mut cursor = 0;
     // The address in the backtrace is relocated, so we have to convert it back to the address in
@@ -197,8 +197,10 @@ pub fn terminate(exception: &'static eh_artiq::Exception<'static>, backtrace: &'
         }
     }
 
-    let core1_tx: &mut sync_channel::Sender<Message> = unsafe { mem::transmute(KERNEL_CHANNEL_1TO0) };
-    core1_tx.send(Message::KernelException(exception, &backtrace[..cursor]));
+    {
+        let mut core1_tx = KERNEL_CHANNEL_1TO0.lock();
+        core1_tx.as_mut().unwrap().send(Message::KernelException(exception, &backtrace[..cursor]));
+    }
     // TODO: remove after implementing graceful kernel termination.
     error!("Core1 uncaught exception");
     loop {}

src/runtime/src/kernel/dma.rs

@@ -5,7 +5,7 @@ use crate::{
 };
 use alloc::{vec::Vec, string::String, collections::BTreeMap, str};
 use cslice::CSlice;
-use super::KERNEL_LIBRARY;
+use super::KERNEL_IMAGE;
 use core::mem;
 use log::debug;
 
@@ -136,7 +136,7 @@ pub extern fn dma_record_start(name: CSlice<u8>) {
             artiq_raise!("DMAError", "DMA is already recording")
         }
 
-        let library = KERNEL_LIBRARY.as_mut().unwrap();
+        let library = KERNEL_IMAGE.as_ref().unwrap();
         library.rebind(b"rtio_output",
                        dma_record_output as *const ()).unwrap();
         library.rebind(b"rtio_output_wide",
@@ -156,7 +156,7 @@ pub extern fn dma_record_stop(duration: i64) {
             artiq_raise!("DMAError", "DMA is not recording")
         }
 
-        let library = KERNEL_LIBRARY.as_mut().unwrap();
+        let library = KERNEL_IMAGE.as_ref().unwrap();
         library.rebind(b"rtio_output",
                        rtio::output as *const ()).unwrap();
         library.rebind(b"rtio_output_wide",

src/runtime/src/kernel/mod.rs

@@ -1,7 +1,6 @@
 use core::ptr;
 use alloc::{vec::Vec, sync::Arc, string::String};
 
-use dyld::Library;
 use libcortex_a9::{mutex::Mutex, sync_channel};
 use crate::eh_artiq;
 
@@ -39,7 +38,8 @@ pub enum Message {
 static CHANNEL_0TO1: Mutex<Option<sync_channel::Receiver<Message>>> = Mutex::new(None);
 static CHANNEL_1TO0: Mutex<Option<sync_channel::Sender<Message>>> = Mutex::new(None);
 
-static mut KERNEL_CHANNEL_0TO1: *mut () = ptr::null_mut();
-static mut KERNEL_CHANNEL_1TO0: *mut () = ptr::null_mut();
-static mut KERNEL_LIBRARY: *mut Library = ptr::null_mut();
+static KERNEL_CHANNEL_0TO1: Mutex<Option<sync_channel::Receiver<Message>>> = Mutex::new(None);
+static KERNEL_CHANNEL_1TO0: Mutex<Option<sync_channel::Sender<Message>>> = Mutex::new(None);
+
+static mut KERNEL_IMAGE: *const core1::KernelImage = ptr::null();
 

src/runtime/src/kernel/rpc.rs

@@ -1,10 +1,8 @@
 //! Kernel-side RPC API
 
-use core::mem;
 use alloc::{vec::Vec, sync::Arc};
 use cslice::{CSlice, AsCSlice};
 
-use libcortex_a9::sync_channel;
 use crate::eh_artiq;
 use crate::rpc::send_args;
 use super::{
@@ -13,10 +11,10 @@ use super::{
 };
 
 fn rpc_send_common(is_async: bool, service: u32, tag: &CSlice<u8>, data: *const *const ()) {
-    let core1_tx: &mut sync_channel::Sender<Message> = unsafe { mem::transmute(KERNEL_CHANNEL_1TO0) };
+    let mut core1_tx = KERNEL_CHANNEL_1TO0.lock();
     let mut buffer = Vec::<u8>::new();
     send_args(&mut buffer, service, tag.as_ref(), data).expect("RPC encoding failed");
-    core1_tx.send(Message::RpcSend { is_async: is_async, data: Arc::new(buffer) });
+    core1_tx.as_mut().unwrap().send(Message::RpcSend { is_async, data: Arc::new(buffer) });
 }
 
 pub extern fn rpc_send(service: u32, tag: &CSlice<u8>, data: *const *const ()) {
@@ -28,10 +26,12 @@ pub extern fn rpc_send_async(service: u32, tag: &CSlice<u8>, data: *const *const
 }
 
 pub extern fn rpc_recv(slot: *mut ()) -> usize {
-    let core1_rx: &mut sync_channel::Receiver<Message> = unsafe { mem::transmute(KERNEL_CHANNEL_0TO1) };
-    let core1_tx: &mut sync_channel::Sender<Message> = unsafe { mem::transmute(KERNEL_CHANNEL_1TO0) };
-    core1_tx.send(Message::RpcRecvRequest(slot));
-    let reply = core1_rx.recv();
+    let reply = {
+        let mut core1_rx = KERNEL_CHANNEL_0TO1.lock();
+        let mut core1_tx = KERNEL_CHANNEL_1TO0.lock();
+        core1_tx.as_mut().unwrap().send(Message::RpcRecvRequest(slot));
+        core1_rx.as_mut().unwrap().recv()
+    };
     match *reply {
         Message::RpcRecvReply(Ok(alloc_size)) => alloc_size,
         Message::RpcRecvReply(Err(exception)) => unsafe {