systemc: Fortify how exceptions are caught and passed around.

This change tightens up exception catching and makes gem5's systemc
code react to exceptions more in line with the Accellera
implementation. This prevents exceptions from being caught by the
pybind11 integration which makes it very difficult to see where an
exception came from, and makes the output differ by including a
(mostly useless) backtrace.

Change-Id: I7130d53a98fadd137073d1718f780f32f57c658c
Reviewed-on: https://gem5-review.googlesource.com/c/12601
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/systemc/core/process.cc

@@ -343,6 +343,8 @@ Process::run()
         } catch(const ::sc_core::sc_unwind_exception &exc) {
             reset = exc.is_reset();
             _isUnwinding = false;
+        } catch (...) {
+            throw;
         }
     } while (reset);
     needsStart(true);

src/systemc/core/process_types.hh

@@ -92,7 +92,13 @@ class Thread : public Process
         main() override
         {
             thread->_needsStart = false;
-            thread->run();
+            try {
+                thread->run();
+            } catch (...) {
+                thread->terminate();
+                scheduler.throwToScMain();
+                return;
+            }
             thread->terminate();
             scheduler.yield();
         }

src/systemc/core/sc_main.cc

@@ -79,6 +79,10 @@ class ScMainFiber : public Fiber
             } catch (const sc_report &r) {
                 // There was an exception nobody caught.
                 resultStr = r.what();
+            } catch (...) {
+                // There was some other type of exception we need to wrap.
+                const sc_report *r = ::sc_gem5::reportifyException();
+                resultStr = r->what();
             }
             ::sc_gem5::Kernel::scMainFinished(true);
             ::sc_gem5::scheduler.clear();

src/systemc/core/scheduler.cc

@@ -34,6 +34,8 @@
 #include "sim/eventq.hh"
 #include "systemc/core/kernel.hh"
 #include "systemc/ext/core/sc_main.hh"
+#include "systemc/ext/utils/sc_report.hh"
+#include "systemc/ext/utils/sc_report_handler.hh"
 
 namespace sc_gem5
 {
@@ -42,7 +44,7 @@ Scheduler::Scheduler() :
     eq(nullptr), readyEvent(this, false, ReadyPriority),
     pauseEvent(this, false, PausePriority),
     stopEvent(this, false, StopPriority),
-    scMain(nullptr),
+    scMain(nullptr), _throwToScMain(nullptr),
     starvationEvent(this, false, StarvationPriority),
     _started(false), _paused(false), _stopped(false), _stopNow(false),
     maxTickEvent(this, false, MaxTickPriority),
@@ -184,7 +186,11 @@ Scheduler::yield()
         // If the current process needs to be manually started, start it.
         if (_current && _current->needsStart()) {
             _current->needsStart(false);
-            _current->run();
+            try {
+                _current->run();
+            } catch (...) {
+                throwToScMain();
+            }
         }
     }
     if (_current && _current->excWrapper) {
@@ -336,7 +342,8 @@ Scheduler::pause()
     _paused = true;
     kernel->status(::sc_core::SC_PAUSED);
     runOnce = false;
-    scMain->run();
+    if (scMain && !scMain->finished())
+        scMain->run();
 }
 
 void
@@ -348,7 +355,8 @@ Scheduler::stop()
     clear();
 
     runOnce = false;
-    scMain->run();
+    if (scMain && !scMain->finished())
+        scMain->run();
 }
 
 void
@@ -385,6 +393,12 @@ Scheduler::start(Tick max_tick, bool run_to_time)
         deschedule(&maxTickEvent);
     if (starvationEvent.scheduled())
         deschedule(&starvationEvent);
+
+    if (_throwToScMain) {
+        const ::sc_core::sc_report *to_throw = _throwToScMain;
+        _throwToScMain = nullptr;
+        throw *to_throw;
+    }
 }
 
 void
@@ -404,6 +418,15 @@ Scheduler::schedulePause()
     schedule(&pauseEvent);
 }
 
+void
+Scheduler::throwToScMain(const ::sc_core::sc_report *r)
+{
+    if (!r)
+        r = reportifyException();
+    _throwToScMain = r;
+    scMain->run();
+}
+
 void
 Scheduler::scheduleStop(bool finish_delta)
 {
@@ -421,4 +444,46 @@ Scheduler::scheduleStop(bool finish_delta)
 
 Scheduler scheduler;
 
+namespace {
+
+void
+throwingReportHandler(const ::sc_core::sc_report &r,
+                      const ::sc_core::sc_actions &)
+{
+    throw r;
+}
+
+} // anonymous namespace
+
+const ::sc_core::sc_report *
+reportifyException()
+{
+    ::sc_core::sc_report_handler_proc old_handler =
+        ::sc_core::sc_report_handler::get_handler();
+    ::sc_core::sc_report_handler::set_handler(&throwingReportHandler);
+
+    try {
+        try {
+            // Rethrow the current exception so we can catch it and throw an
+            // sc_report instead if it's not a type we recognize/can handle.
+            throw;
+        } catch (const ::sc_core::sc_report &) {
+            // It's already a sc_report, so nothing to do.
+            throw;
+        } catch (const ::sc_core::sc_unwind_exception &) {
+            panic("Kill/reset exception escaped a Process::run()");
+        } catch (const std::exception &e) {
+            SC_REPORT_ERROR("uncaught exception", e.what());
+        } catch (const char *msg) {
+            SC_REPORT_ERROR("uncaught exception", msg);
+        } catch (...) {
+            SC_REPORT_ERROR("uncaught exception", "UNKNOWN EXCEPTION");
+        }
+    } catch (const ::sc_core::sc_report &r) {
+        ::sc_core::sc_report_handler::set_handler(old_handler);
+        return &r;
+    }
+    panic("No exception thrown in reportifyException.");
+}
+
 } // namespace sc_gem5

src/systemc/core/scheduler.hh

@@ -333,6 +333,8 @@ class Scheduler
 
     uint64_t changeStamp() { return _changeStamp; }
 
+    void throwToScMain(const ::sc_core::sc_report *r=nullptr);
+
   private:
     typedef const EventBase::Priority Priority;
     static Priority DefaultPriority = EventBase::Default_Pri;
@@ -377,7 +379,9 @@ class Scheduler
     void stop();
     EventWrapper<Scheduler, &Scheduler::pause> pauseEvent;
     EventWrapper<Scheduler, &Scheduler::stop> stopEvent;
+
     Fiber *scMain;
+    const ::sc_core::sc_report *_throwToScMain;
 
     bool
     starved()
@@ -437,6 +441,8 @@ Scheduler::TimeSlot::process()
     scheduler.completeTimeSlot(this);
 }
 
+const ::sc_core::sc_report *reportifyException();
+
 } // namespace sc_gem5
 
 #endif // __SYSTEMC_CORE_SCHEDULER_H__

src/systemc/ext/utils/sc_report_handler.hh

@@ -105,6 +105,10 @@ class sc_report_handler
     static void set_handler(sc_report_handler_proc);
     static void default_handler(const sc_report &, const sc_actions &);
     static sc_actions get_new_action_id();
+    // Nonstandard
+    // Returns the current handler so it can be restored if it needs to be
+    // changed temporarily.
+    static sc_report_handler_proc get_handler();
 
     static sc_report *get_cached_report();
     static void clear_cached_report();

src/systemc/tests/config.py

@@ -31,6 +31,7 @@ import argparse
 import m5
 import os
 import re
+import sys
 
 from m5.objects import SystemC_Kernel, Root
 
@@ -58,7 +59,5 @@ if result.code != 0:
     # generate errors, and as long as their output matches that's still
     # considered correct. A "real" systemc config should expect sc_main
     # (if present) not to fail.
-    scrubbed = re.sub(r'In file: .*$',
-            'In file: <removed by verify.pl>',
-            result.message)
-    print('\n' + scrubbed)
+    print('\n' + result.message)
+    sys.exit(int(result.code))

src/systemc/utils/sc_report_handler.cc

@@ -341,6 +341,12 @@ sc_report_handler::get_new_action_id()
     return maxAction;
 }
 
+sc_report_handler_proc
+sc_report_handler::get_handler()
+{
+    return reportHandlerProc;
+}
+
 sc_report *
 sc_report_handler::get_cached_report()
 {