diff --git a/artiq/compiler/builtins.py b/artiq/compiler/builtins.py
index 6b9feb9e2..86a356ef3 100644
--- a/artiq/compiler/builtins.py
+++ b/artiq/compiler/builtins.py
@@ -86,6 +86,7 @@ class TException(types.TMono):
         ("__file__",    TStr()),
         ("__line__",    TInt(types.TValue(32))),
         ("__col__",     TInt(types.TValue(32))),
+        ("__func__",    TStr()),
         ("__message__", TStr()),
         ("__param0__",  TInt(types.TValue(64))),
         ("__param1__",  TInt(types.TValue(64))),
diff --git a/artiq/compiler/transforms/artiq_ir_generator.py b/artiq/compiler/transforms/artiq_ir_generator.py
index 84bcbc6c5..8e51b8a3e 100644
--- a/artiq/compiler/transforms/artiq_ir_generator.py
+++ b/artiq/compiler/transforms/artiq_ir_generator.py
@@ -157,7 +157,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
 
     def visit_function(self, node, is_lambda, is_internal):
         if is_lambda:
-            name = "lambda.{}.{}".format(node.loc.line(), node.loc.column())
+            name = "lambda@{}:{}".format(node.loc.line(), node.loc.column())
             typ = node.type.find()
         else:
             name = node.name
@@ -471,9 +471,11 @@ class ARTIQIRGenerator(algorithm.Visitor):
             loc_file = ir.Constant(self.current_loc.source_buffer.name, builtins.TStr())
             loc_line = ir.Constant(self.current_loc.line(), builtins.TInt(types.TValue(32)))
             loc_column = ir.Constant(self.current_loc.column(), builtins.TInt(types.TValue(32)))
+            loc_function = ir.Constant(".".join(self.name), builtins.TStr())
             self.append(ir.SetAttr(exn, "__file__", loc_file))
             self.append(ir.SetAttr(exn, "__line__", loc_line))
             self.append(ir.SetAttr(exn, "__col__", loc_column))
+            self.append(ir.SetAttr(exn, "__func__", loc_function))
 
             if self.unwind_target is not None:
                 self.append(ir.Raise(exn, self.unwind_target))
@@ -1237,6 +1239,7 @@ class ARTIQIRGenerator(algorithm.Visitor):
             ir.Constant("<not thrown>", builtins.TStr()),           # file
             ir.Constant(0, builtins.TInt(types.TValue(32))),        # line
             ir.Constant(0, builtins.TInt(types.TValue(32))),        # column
+            ir.Constant("<not thrown>", builtins.TStr()),           # function
         ]
 
         if message is None:
diff --git a/artiq/coredevice/comm_generic.py b/artiq/coredevice/comm_generic.py
index b386a7430..df0cbb4cd 100644
--- a/artiq/coredevice/comm_generic.py
+++ b/artiq/coredevice/comm_generic.py
@@ -1,5 +1,6 @@
 import struct
 import logging
+import traceback
 from enum import Enum
 from fractions import Fraction
 
@@ -18,11 +19,12 @@ class _H2DMsgType(Enum):
     RUN_KERNEL = 5
 
     RPC_REPLY = 6
+    RPC_EXCEPTION = 7
 
-    FLASH_READ_REQUEST = 7
-    FLASH_WRITE_REQUEST = 8
-    FLASH_ERASE_REQUEST = 9
-    FLASH_REMOVE_REQUEST = 10
+    FLASH_READ_REQUEST = 8
+    FLASH_WRITE_REQUEST = 9
+    FLASH_ERASE_REQUEST = 10
+    FLASH_REMOVE_REQUEST = 11
 
 
 class _D2HMsgType(Enum):
@@ -223,16 +225,12 @@ class CommGeneric:
 
         self._read_empty(_D2HMsgType.CLOCK_SWITCH_COMPLETED)
 
-    def load(self, kernel_library):
-        self._write_header(_H2DMsgType.LOAD_LIBRARY)
-        self._write_chunk(kernel_library)
-        self._write_flush()
+    def get_log(self):
+        self._write_empty(_H2DMsgType.LOG_REQUEST)
 
-        self._read_empty(_D2HMsgType.LOAD_COMPLETED)
-
-    def run(self):
-        self._write_empty(_H2DMsgType.RUN_KERNEL)
-        logger.debug("running kernel")
+        self._read_header()
+        self._read_expect(_D2HMsgType.LOG_REPLY)
+        return self._read_chunk(self._read_length).decode('utf-8')
 
     def flash_storage_read(self, key):
         self._write_header(_H2DMsgType.FLASH_READ_REQUEST)
@@ -267,7 +265,18 @@ class CommGeneric:
 
         self._read_empty(_D2HMsgType.FLASH_OK_REPLY)
 
-    def _receive_rpc_value(self, tag):
+    def load(self, kernel_library):
+        self._write_header(_H2DMsgType.LOAD_LIBRARY)
+        self._write_chunk(kernel_library)
+        self._write_flush()
+
+        self._read_empty(_D2HMsgType.LOAD_COMPLETED)
+
+    def run(self):
+        self._write_empty(_H2DMsgType.RUN_KERNEL)
+        logger.debug("running kernel")
+
+    def _receive_rpc_value(self, tag, rpc_map):
         if tag == "n":
             return None
         elif tag == "b":
@@ -286,37 +295,83 @@ class CommGeneric:
             elt_tag = chr(self._read_int8())
             length = self._read_int32()
             return [self._receive_rpc_value(elt_tag) for _ in range(length)]
+        elif tag == "o":
+            return rpc_map[self._read_int32()]
         else:
             raise IOError("Unknown RPC value tag: {}", tag)
 
-    def _receive_rpc_values(self):
+    def _receive_rpc_values(self, rpc_map):
         result = []
         while True:
             tag = chr(self._read_int8())
             if tag == "\x00":
                 return result
             else:
-                result.append(self._receive_rpc_value(tag))
+                result.append(self._receive_rpc_value(tag, rpc_map))
 
     def _serve_rpc(self, rpc_map):
         service = self._read_int32()
-        args = self._receive_rpc_values()
+        args = self._receive_rpc_values(rpc_map)
         logger.debug("rpc service: %d %r", service, args)
 
-        eid, result = rpc_wrapper.run_rpc(rpc_map[rpc_num], args)
-        logger.debug("rpc service: %d %r == %r (eid %d)", service, args,
-                     result, eid)
+        try:
+            result = rpc_map[rpc_num](args)
+            if not isinstance(result, int) or not (-2**31 < result < 2**31-1):
+                raise ValueError("An RPC must return an int(width=32)")
+        except ARTIQException as exn:
+            logger.debug("rpc service: %d %r ! %r", service, args, exn)
 
-        self._write_header(_H2DMsgType.RPC_REPLY)
-        self._write_int32(eid)
-        self._write_int32(result)
-        self._write_flush()
+            self._write_header(_H2DMsgType.RPC_EXCEPTION)
+            self._write_string(exn.name)
+            self._write_string(exn.message)
+            for index in range(3):
+                self._write_int64(exn.param[index])
+
+            self._write_string(exn.filename)
+            self._write_int32(exn.line)
+            self._write_int32(exn.column)
+            self._write_string(exn.function)
+
+            self._write_flush()
+        except Exception as exn:
+            logger.debug("rpc service: %d %r ! %r", service, args, exn)
+
+            self._write_header(_H2DMsgType.RPC_EXCEPTION)
+            self._write_string(type(exn).__name__)
+            self._write_string(str(exn))
+            for index in range(3):
+                self._write_int64(0)
+
+            ((filename, line, function, _), ) = traceback.extract_tb(exn.__traceback__)
+            self._write_string(filename)
+            self._write_int32(line)
+            self._write_int32(-1) # column not known
+            self._write_string(function)
+
+            self._write_flush()
+        else:
+            logger.debug("rpc service: %d %r == %r", service, args, result)
+
+            self._write_header(_H2DMsgType.RPC_REPLY)
+            self._write_int32(result)
+            self._write_flush()
 
     def _serve_exception(self):
-        eid = self._read_int32()
-        params = [self._read_int64() for _ in range(3)]
-        rpc_wrapper.filter_rpc_exception(eid)
-        raise exception(self.core, *params)
+        name      = self._read_string()
+        message   = self._read_string()
+        params    = [self._read_int64() for _ in range(3)]
+
+        filename  = self._read_string()
+        line      = self._read_int32()
+        column    = self._read_int32()
+        function  = self._read_string()
+
+        backtrace = [self._read_int32() for _ in range(self._read_int32())]
+        # we don't have debug information yet.
+        # print("exception backtrace:", [hex(x) for x in backtrace])
+
+        raise core_language.ARTIQException(name, message, params,
+                                           filename, line, column, function)
 
     def serve(self, rpc_map):
         while True:
@@ -328,10 +383,3 @@ class CommGeneric:
             else:
                 self._read_expect(_D2HMsgType.KERNEL_FINISHED)
                 return
-
-    def get_log(self):
-        self._write_empty(_H2DMsgType.LOG_REQUEST)
-
-        self._read_header()
-        self._read_expect(_D2HMsgType.LOG_REPLY)
-        return self._read_chunk(self._read_length).decode('utf-8')
diff --git a/artiq/coredevice/exceptions.py b/artiq/coredevice/exceptions.py
index 05d475908..d0f54f2fa 100644
--- a/artiq/coredevice/exceptions.py
+++ b/artiq/coredevice/exceptions.py
@@ -1,5 +1,13 @@
 from artiq.language.core import ARTIQException
 
+class ZeroDivisionError(ARTIQException):
+    """Python's :class:`ZeroDivisionError`, mirrored in ARTIQ."""
+
+class ValueError(ARTIQException):
+    """Python's :class:`ValueError`, mirrored in ARTIQ."""
+
+class IndexError(ARTIQException):
+    """Python's :class:`IndexError`, mirrored in ARTIQ."""
 
 class InternalError(ARTIQException):
     """Raised when the runtime encounters an internal error condition."""
diff --git a/artiq/language/core.py b/artiq/language/core.py
index d8e24a552..a7dfecc5d 100644
--- a/artiq/language/core.py
+++ b/artiq/language/core.py
@@ -2,6 +2,7 @@
 Core ARTIQ extensions to the Python language.
 """
 
+import linecache
 from collections import namedtuple
 from functools import wraps
 
@@ -278,7 +279,8 @@ class ARTIQException(Exception):
     """Base class for exceptions raised or passed through the core device."""
 
     # Try and create an instance of the specific class, if one exists.
-    def __new__(cls, name, message, params):
+    def __new__(cls, name, message,
+                params, filename, line, column, function):
         def find_subclass(cls):
             if cls.__name__ == name:
                 return cls
@@ -293,15 +295,30 @@ class ARTIQException(Exception):
             more_specific_cls = cls
 
         exn = Exception.__new__(more_specific_cls)
-        exn.__init__(name, message, params)
+        exn.__init__(name, message, params,
+                     filename, line, column, function)
         return exn
 
-    def __init__(self, name, message, params):
+    def __init__(self, name, message, params,
+                 filename, line, column, function):
         Exception.__init__(self, name, message, *params)
         self.name, self.message, self.params = name, message, params
+        self.filename, self.line, self.column = filename, line, column
+        self.function = function
 
     def __str__(self):
+        lines = []
+
         if type(self).__name__ == self.name:
-            return self.message.format(*self.params)
+            lines.append(self.message.format(*self.params))
         else:
-            return "({}) {}".format(self.name, self.message.format(*self.params))
+            lines.append("({}) {}".format(self.name, self.message.format(*self.params)))
+
+        lines.append("Core Device Traceback (most recent call last):")
+        lines.append("  File \"{file}\", line {line}, column {column}, in {function}".
+                     format(file=self.filename, line=self.line, column=self.column + 1,
+                            function=self.function))
+        line = linecache.getline(self.filename, self.line)
+        lines.append("    {}".format(line.strip() if line else "<unknown>"))
+
+        return "\n".join(lines)
diff --git a/soc/runtime/artiq_personality.h b/soc/runtime/artiq_personality.h
index 1952e7269..11a10b2b9 100644
--- a/soc/runtime/artiq_personality.h
+++ b/soc/runtime/artiq_personality.h
@@ -12,6 +12,7 @@ struct artiq_exception {
   const char *file;
   int32_t line;
   int32_t column;
+  const char *function;
   const char *message;
   int64_t param[3];
 };
diff --git a/soc/runtime/kloader.c b/soc/runtime/kloader.c
index 5d1cb0a32..14b4abb7b 100644
--- a/soc/runtime/kloader.c
+++ b/soc/runtime/kloader.c
@@ -30,7 +30,7 @@ void kloader_start_bridge()
     start_kernel_cpu(NULL);
 }
 
-static int load_or_start_kernel(void *library, int run_kernel)
+static int load_or_start_kernel(const void *library, int run_kernel)
 {
     static struct dyld_info library_info;
     struct msg_load_request request = {
@@ -56,7 +56,7 @@ static int load_or_start_kernel(void *library, int run_kernel)
     return 1;
 }
 
-int kloader_load_library(void *library)
+int kloader_load_library(const void *library)
 {
     if(!kernel_cpu_reset_read()) {
         log("BUG: attempted to load kernel library while kernel CPU is running");
@@ -66,6 +66,22 @@ int kloader_load_library(void *library)
     return load_or_start_kernel(library, 0);
 }
 
+void kloader_filter_backtrace(struct artiq_backtrace_item *backtrace,
+                              size_t *backtrace_size) {
+    struct artiq_backtrace_item *cursor = backtrace;
+
+    // Remove all backtrace items belonging to ksupport and subtract
+    // shared object base from the addresses.
+    for(int i = 0; i < *backtrace_size; i++) {
+        if(backtrace[i].function > KERNELCPU_PAYLOAD_ADDRESS) {
+            backtrace[i].function -= KERNELCPU_PAYLOAD_ADDRESS;
+            *cursor++ = backtrace[i];
+        }
+    }
+
+    *backtrace_size = cursor - backtrace;
+}
+
 void kloader_start_kernel()
 {
     load_or_start_kernel(NULL, 1);
diff --git a/soc/runtime/kloader.h b/soc/runtime/kloader.h
index 834fd8d3d..807617e25 100644
--- a/soc/runtime/kloader.h
+++ b/soc/runtime/kloader.h
@@ -1,6 +1,8 @@
 #ifndef __KLOADER_H
 #define __KLOADER_H
 
+#include "artiq_personality.h"
+
 #define KERNELCPU_EXEC_ADDRESS    0x40400000
 #define KERNELCPU_PAYLOAD_ADDRESS 0x40420000
 #define KERNELCPU_LAST_ADDRESS    (0x4fffffff - 1024*1024)
@@ -8,7 +10,9 @@
 
 extern long long int now;
 
-int kloader_load_library(void *code);
+int kloader_load_library(const void *code);
+void kloader_filter_backtrace(struct artiq_backtrace_item *backtrace,
+                              size_t *backtrace_size);
 
 void kloader_start_bridge(void);
 int kloader_start_idle_kernel(void);
diff --git a/soc/runtime/ksupport.c b/soc/runtime/ksupport.c
index da02bc4a0..b2082beef 100644
--- a/soc/runtime/ksupport.c
+++ b/soc/runtime/ksupport.c
@@ -246,7 +246,8 @@ long long int now_init(void)
 
     reply = mailbox_wait_and_receive();
     if(reply->type != MESSAGE_TYPE_NOW_INIT_REPLY) {
-        log("Malformed MESSAGE_TYPE_NOW_INIT_REQUEST reply type");
+        log("Malformed MESSAGE_TYPE_NOW_INIT_REQUEST reply type %d",
+            reply->type);
         while(1);
     }
     now = reply->now;
@@ -281,7 +282,8 @@ int watchdog_set(int ms)
 
     reply = mailbox_wait_and_receive();
     if(reply->type != MESSAGE_TYPE_WATCHDOG_SET_REPLY) {
-        log("Malformed MESSAGE_TYPE_WATCHDOG_SET_REQUEST reply type");
+        log("Malformed MESSAGE_TYPE_WATCHDOG_SET_REQUEST reply type %d",
+            reply->type);
         while(1);
     }
     id = reply->id;
@@ -302,7 +304,7 @@ void watchdog_clear(int id)
 int rpc(int rpc_num, ...)
 {
     struct msg_rpc_request request;
-    struct msg_rpc_reply *reply;
+    struct msg_base *reply;
 
     request.type = MESSAGE_TYPE_RPC_REQUEST;
     request.rpc_num = rpc_num;
@@ -311,20 +313,20 @@ int rpc(int rpc_num, ...)
     va_end(request.args);
 
     reply = mailbox_wait_and_receive();
-    if(reply->type != MESSAGE_TYPE_RPC_REPLY) {
-        log("Malformed MESSAGE_TYPE_RPC_REPLY reply type");
-        while(1);
-    }
-
-    if(reply->exception != NULL) {
+    if(reply->type == MESSAGE_TYPE_RPC_REPLY) {
+        int result = ((struct msg_rpc_reply *)reply)->result;
+        mailbox_acknowledge();
+        return result;
+    } else if(reply->type == MESSAGE_TYPE_RPC_EXCEPTION) {
         struct artiq_exception exception;
-        memcpy(&exception, reply->exception, sizeof(exception));
+        memcpy(&exception, ((struct msg_rpc_exception *)reply)->exception,
+               sizeof(struct artiq_exception));
         mailbox_acknowledge();
         __artiq_raise(&exception);
     } else {
-        int retval = reply->retval;
-        mailbox_acknowledge();
-        return retval;
+        log("Malformed MESSAGE_TYPE_RPC_REQUEST reply type %d",
+            reply->type);
+        while(1);
     }
 }
 
diff --git a/soc/runtime/messages.h b/soc/runtime/messages.h
index cb0c9c20b..651c7a5ef 100644
--- a/soc/runtime/messages.h
+++ b/soc/runtime/messages.h
@@ -16,6 +16,7 @@ enum {
     MESSAGE_TYPE_WATCHDOG_CLEAR,
     MESSAGE_TYPE_RPC_REQUEST,
     MESSAGE_TYPE_RPC_REPLY,
+    MESSAGE_TYPE_RPC_EXCEPTION,
     MESSAGE_TYPE_LOG,
 
     MESSAGE_TYPE_BRG_READY,
@@ -37,7 +38,7 @@ struct msg_base {
 /* kernel messages */
 
 struct msg_load_request {
-    void *library;
+    const void *library;
     struct dyld_info *library_info;
     int run_kernel;
 };
@@ -86,9 +87,13 @@ struct msg_rpc_request {
 };
 
 struct msg_rpc_reply {
+    int type;
+    int result;
+};
+
+struct msg_rpc_exception {
     int type;
     struct artiq_exception *exception;
-    int retval;
 };
 
 struct msg_log {
diff --git a/soc/runtime/session.c b/soc/runtime/session.c
index 1ad70c272..b571c5873 100644
--- a/soc/runtime/session.c
+++ b/soc/runtime/session.c
@@ -128,6 +128,13 @@ static int32_t in_packet_int32()
     return result;
 }
 
+static int64_t in_packet_int64()
+{
+    int64_t result;
+    in_packet_chunk(&result, sizeof(result));
+    return result;
+}
+
 static const void *in_packet_bytes(int *length)
 {
     *length = in_packet_int32();
@@ -310,6 +317,7 @@ enum {
     REMOTEMSG_TYPE_RUN_KERNEL,
 
     REMOTEMSG_TYPE_RPC_REPLY,
+    REMOTEMSG_TYPE_RPC_EXCEPTION,
 
     REMOTEMSG_TYPE_FLASH_READ_REQUEST,
     REMOTEMSG_TYPE_FLASH_WRITE_REQUEST,
@@ -452,15 +460,44 @@ static int process_input(void)
         case REMOTEMSG_TYPE_RPC_REPLY: {
             struct msg_rpc_reply reply;
 
+            int result = in_packet_int32();
+
             if(user_kernel_state != USER_KERNEL_WAIT_RPC) {
                 log("Unsolicited RPC reply");
                 return 0; // restart session
             }
 
             reply.type = MESSAGE_TYPE_RPC_REPLY;
-            // FIXME memcpy(&reply.eid, &buffer_in[9], 4);
-            // memcpy(&reply.retval, &buffer_in[13], 4);
+            reply.result = result;
             mailbox_send_and_wait(&reply);
+
+            user_kernel_state = USER_KERNEL_RUNNING;
+            break;
+        }
+
+        case REMOTEMSG_TYPE_RPC_EXCEPTION: {
+            struct msg_rpc_exception reply;
+
+            struct artiq_exception exception;
+            exception.name     = in_packet_string();
+            exception.message  = in_packet_string();
+            exception.param[0] = in_packet_int64();
+            exception.param[1] = in_packet_int64();
+            exception.param[2] = in_packet_int64();
+            exception.file     = in_packet_string();
+            exception.line     = in_packet_int32();
+            exception.column   = in_packet_int32();
+            exception.function = in_packet_string();
+
+            if(user_kernel_state != USER_KERNEL_WAIT_RPC) {
+                log("Unsolicited RPC exception reply");
+                return 0; // restart session
+            }
+
+            reply.type = MESSAGE_TYPE_RPC_EXCEPTION;
+            reply.exception = &exception;
+            mailbox_send_and_wait(&reply);
+
             user_kernel_state = USER_KERNEL_RUNNING;
             break;
         }
@@ -509,8 +546,6 @@ static int send_rpc_value(const char **tag, void *value)
             break;
 
         case 'l': { // list(elt='a)
-            size = sizeof(void*);
-
             struct { uint32_t length; void *elements; } *list = value;
             void *element = list->elements;
 
@@ -522,6 +557,18 @@ static int send_rpc_value(const char **tag, void *value)
                 element = (void*)((intptr_t)element + element_size);
             }
             *tag = tag_copy;
+
+            size = sizeof(list);
+            break;
+        }
+
+        case 'o': { // host object
+            struct { uint32_t id; } *object = value;
+
+            if(!out_packet_int32(object->id))
+                return -1;
+
+            size = sizeof(object);
             break;
         }
 
@@ -575,10 +622,29 @@ static int process_kmsg(struct msg_base *umsg)
         case MESSAGE_TYPE_EXCEPTION: {
             struct msg_exception *msg = (struct msg_exception *)umsg;
 
-            out_packet_empty(REMOTEMSG_TYPE_KERNEL_EXCEPTION);
-            // memcpy(&buffer_out[9], &msg->eid, 4);
-            // memcpy(&buffer_out[13], msg->eparams, 3*8);
-            // submit_output(9+4+3*8);
+            out_packet_start(REMOTEMSG_TYPE_KERNEL_EXCEPTION);
+
+            out_packet_string(msg->exception->name);
+            out_packet_string(msg->exception->message);
+            out_packet_int64(msg->exception->param[0]);
+            out_packet_int64(msg->exception->param[1]);
+            out_packet_int64(msg->exception->param[2]);
+
+            out_packet_string(msg->exception->file);
+            out_packet_int32(msg->exception->line);
+            out_packet_int32(msg->exception->column);
+            out_packet_string(msg->exception->function);
+
+            kloader_filter_backtrace(msg->backtrace,
+                                     &msg->backtrace_size);
+
+            out_packet_int32(msg->backtrace_size);
+            for(int i = 0; i < msg->backtrace_size; i++) {
+                struct artiq_backtrace_item *item = &msg->backtrace[i];
+                out_packet_int32(item->function + item->offset);
+            }
+
+            out_packet_finish();
 
             kloader_stop();
             user_kernel_state = USER_KERNEL_LOADED;