subkernels: raise exceptions to kernel

src/libksupport/src/eh_artiq.rs

@@ -14,8 +14,10 @@
 
 use core::mem;
 
+use core_io::Error as ReadError;
 use cslice::CSlice;
 use dwarf::eh::{self, EHAction, EHContext};
+use io::{Cursor, ProtoRead};
 use libc::{c_int, c_void, uintptr_t};
 use log::{error, trace};
 use unwind as uw;
@@ -295,6 +297,60 @@ pub unsafe extern "C" fn raise(exception: *const Exception) -> ! {
     unreachable!();
 }
 
+fn read_exception_string<'a>(reader: &mut Cursor<&[u8]>) -> Result<CSlice<'a, u8>, ReadError> {
+    let len = reader.read_u32()? as usize;
+    if len == usize::MAX {
+        let data = reader.read_u32()?;
+        Ok(unsafe { CSlice::new(data as *const u8, len) })
+    } else {
+        let pos = reader.position();
+        let slice = unsafe {
+            let ptr = reader.get_ref().as_ptr().offset(pos as isize);
+            CSlice::new(ptr, len)
+        };
+        reader.set_position(pos + len);
+        Ok(slice)
+    }
+}
+
+fn read_exception(raw_exception: &[u8]) -> Result<Exception, ReadError> {
+    let mut reader = Cursor::new(raw_exception);
+
+    let mut byte = reader.read_u8()?;
+    // to sync
+    while byte != 0x5a {
+        byte = reader.read_u8()?;
+    }
+    // skip sync bytes, 0x09 indicates exception
+    while byte != 0x09 {
+        byte = reader.read_u8()?;
+    }
+    let _len = reader.read_u32()?;
+    // ignore the remaining exceptions, stack traces etc. - unwinding from another device would be unwise anyway
+    Ok(Exception {
+        id: reader.read_u32()?,
+        message: read_exception_string(&mut reader)?,
+        param: [
+            reader.read_u64()? as i64,
+            reader.read_u64()? as i64,
+            reader.read_u64()? as i64,
+        ],
+        file: read_exception_string(&mut reader)?,
+        line: reader.read_u32()?,
+        column: reader.read_u32()?,
+        function: read_exception_string(&mut reader)?,
+    })
+}
+
+pub fn raise_raw(raw_exception: &[u8]) -> ! {
+    use crate::artiq_raise;
+    if let Ok(exception) = read_exception(raw_exception) {
+        unsafe { raise(&exception) };
+    } else {
+        artiq_raise!("SubkernelError", "Error passing exception");
+    }
+}
+
 pub unsafe extern "C" fn resume() -> ! {
     trace!("resume");
     assert!(EXCEPTION_BUFFER.exception_count != 0);

src/libksupport/src/kernel/mod.rs

@@ -24,6 +24,7 @@ pub enum SubkernelStatus {
     IncorrectState,
     CommLost,
     OtherError,
+    Exception(Vec<u8>),
 }
 
 #[derive(Debug, Clone)]

src/libksupport/src/kernel/subkernel.rs

@@ -3,7 +3,7 @@ use alloc::vec::Vec;
 use cslice::CSlice;
 
 use super::{Message, SubkernelStatus, KERNEL_CHANNEL_0TO1, KERNEL_CHANNEL_1TO0};
-use crate::{artiq_raise, rpc::send_args};
+use crate::{artiq_raise, eh_artiq, rpc::send_args};
 
 pub extern "C" fn load_run(id: u32, destination: u8, run: bool) {
     unsafe {
@@ -51,6 +51,12 @@ pub extern "C" fn await_finish(id: u32, timeout: i64) {
         Message::SubkernelAwaitFinishReply {
             status: SubkernelStatus::OtherError,
         } => artiq_raise!("SubkernelError", "An error occurred during subkernel operation"),
+        Message::SubkernelAwaitFinishReply {
+            status: SubkernelStatus::Exception(raw_exception),
+        } => {
+            // reconstruct the exception here and raise it
+            eh_artiq::raise_raw(&raw_exception)
+        }
         _ => panic!("expected SubkernelAwaitFinishReply after SubkernelAwaitFinishRequest"),
     }
 }
@@ -116,6 +122,13 @@ pub extern "C" fn await_message(id: i32, timeout: i64, tags: &CSlice<u8>, min: u
             status: SubkernelStatus::OtherError,
             ..
         } => artiq_raise!("SubkernelError", "An error occurred during subkernel operation"),
+        Message::SubkernelMsgRecvReply {
+            status: SubkernelStatus::Exception(raw_exception),
+            ..
+        } => {
+            // reconstruct the raw exception here
+            eh_artiq::raise_raw(&raw_exception);
+        }
         _ => panic!("expected SubkernelMsgRecvReply after SubkernelMsgRecvRequest"),
     }
     // RpcRecvRequest should be called after this to receive message data

src/runtime/src/comms.rs

@@ -423,19 +423,11 @@ async fn handle_run_kernel(
             kernel::Message::SubkernelAwaitFinishRequest { id, timeout } => {
                 let res = subkernel::await_finish(aux_mutex, routing_table, timer, id, timeout).await;
                 let status = match res {
-                    Ok(ref res) => {
+                    Ok(res) => {
                         if res.status == subkernel::FinishStatus::CommLost {
                             kernel::SubkernelStatus::CommLost
-                        } else if let Some(exception) = &res.exception {
-                            error!("Exception in subkernel");
-                            match stream {
-                                None => (),
-                                Some(stream) => {
-                                    write_chunk(stream, exception).await?;
-                                }
-                            }
-                            // will not be called after exception is served
-                            kernel::SubkernelStatus::OtherError
+                        } else if let Some(exception) = res.exception {
+                            kernel::SubkernelStatus::Exception(exception)
                         } else {
                             kernel::SubkernelStatus::NoError
                         }
@@ -475,18 +467,11 @@ async fn handle_run_kernel(
                     Err(SubkernelError::IncorrectState) => (kernel::SubkernelStatus::IncorrectState, 0),
                     Err(SubkernelError::CommLost) => (kernel::SubkernelStatus::CommLost, 0),
                     Err(SubkernelError::SubkernelException) => {
-                        error!("Exception in subkernel");
                         // just retrieve the exception
                         let status = subkernel::await_finish(aux_mutex, routing_table, timer, id as u32, timeout)
                             .await
                             .unwrap();
-                        match stream {
-                            None => (),
-                            Some(stream) => {
-                                write_chunk(stream, &status.exception.unwrap()).await?;
-                            }
-                        }
-                        (kernel::SubkernelStatus::OtherError, 0)
+                        (kernel::SubkernelStatus::Exception(status.exception.unwrap()), 0)
                     }
                     Err(_) => (kernel::SubkernelStatus::OtherError, 0),
                 };