sim: Rework the Linux Kernel exit events (#639)

This patch reworks the Linux Kernel panic and oops events. The code has
been re-factored to provide re-usable events that can be applied to all
ISAs from the base `KernelWorkload` `SimObject`. At the moment they are
installed for the Arm workloads.

This update also provides more configuration options that can be
specified using the new `KernelPanicOopsBehaviour` enum. The options are
applied to the Kernel Workload parameters `on_panic` and `on_oops` which
are available to all subclasses of `KernelWorkload`.

The main rationale for this reworking is to add the option to cleanly
exit the simulation after dumping the Dmesg buffer. Without this option,
the simulation would continue running after a Kernel panic. If system
components (e.g. a system timer) keep the event queue alive, this causes
the simulation to run slowly to the maximum allowed tick.

src/arch/arm/linux/fs_workload.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2010-2013, 2016, 2020 ARM Limited
+ * Copyright (c) 2010-2013, 2016, 2020, 2023 Arm Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -228,21 +228,22 @@ FsLinux::startup()
         }
     }
 
-    const std::string dmesg_output = name() + ".dmesg";
-    if (params().panic_on_panic) {
-        kernelPanic = addKernelFuncEventOrPanic<linux::KernelPanic>(
-            "panic", "Kernel panic in simulated kernel", dmesg_output);
-    } else {
-        kernelPanic = addKernelFuncEventOrPanic<linux::DmesgDump>(
-            "panic", "Kernel panic in simulated kernel", dmesg_output);
+    const std::string dmesg_output_fname = name() + ".dmesg";
+
+    kernelPanic = addKernelFuncEvent<linux::PanicOrOopsEvent>(
+        "panic", "Kernel panic in simulated kernel",
+        dmesg_output_fname, params().on_panic);
+    if (kernelPanic == nullptr) {
+        warn("Could not add Kernel Panic event handler. "
+             "`panic` symbol not found.");
     }
 
-    if (params().panic_on_oops) {
-        kernelOops = addKernelFuncEventOrPanic<linux::KernelPanic>(
-            "oops_exit", "Kernel oops in guest", dmesg_output);
-    } else {
-        kernelOops = addKernelFuncEventOrPanic<linux::DmesgDump>(
-            "oops_exit", "Kernel oops in guest", dmesg_output);
+    kernelOops = addKernelFuncEvent<linux::PanicOrOopsEvent>(
+        "oops_exit", "Kernel oops in guest",
+        dmesg_output_fname, params().on_oops);
+    if (kernelOops == nullptr) {
+        warn("Could not add Kernel Oops event handler. "
+             "`oops_exit` symbol not found.");
     }
 
     // With ARM udelay() is #defined to __udelay

src/kern/linux/events.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011, 2016 ARM Limited
+ * Copyright (c) 2011, 2016, 2023 Arm Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -49,6 +49,7 @@
 #include "kern/linux/helpers.hh"
 #include "kern/system_events.hh"
 #include "sim/core.hh"
+#include "sim/sim_exit.hh"
 #include "sim/system.hh"
 
 namespace gem5
@@ -58,25 +59,22 @@ namespace linux
 {
 
 void
-DmesgDump::process(ThreadContext *tc)
+PanicOrOopsEvent::process(ThreadContext *tc)
 {
-    inform("Dumping kernel dmesg buffer to %s...\n", fname);
-    OutputStream *os = simout.create(fname);
-    dumpDmesg(tc, *os->stream());
-    simout.close(os);
-
     warn(descr());
-}
 
-void
-KernelPanic::process(ThreadContext *tc)
-{
-    inform("Dumping kernel dmesg buffer to %s...\n", fname);
-    OutputStream *os = simout.create(fname);
-    dumpDmesg(tc, *os->stream());
-    simout.close(os);
+    if (behaviour != KernelPanicOopsBehaviour::Continue) {
+        inform("Dumping kernel dmesg buffer to %s...\n", fname);
+        OutputStream *os = simout.create(fname);
+        dumpDmesg(tc, *os->stream());
+        simout.close(os);
+    }
 
-    panic(descr());
+    if (behaviour == KernelPanicOopsBehaviour::DumpDmesgAndExit) {
+        exitSimLoop(descr(), static_cast<int>(1), curTick(), false);
+    } else if (behaviour == KernelPanicOopsBehaviour::DumpDmesgAndPanic) {
+        panic(descr());
+    }
 }
 
 void

src/kern/linux/events.hh

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2016 ARM Limited
+ * Copyright (c) 2016, 2023 Arm Limited
  * All rights reserved
  *
  * The license below extends only to copyright in the software and shall
@@ -47,6 +47,7 @@
 #include "base/compiler.hh"
 #include "base/trace.hh"
 #include "debug/DebugPrintf.hh"
+#include "enums/KernelPanicOopsBehaviour.hh"
 #include "kern/linux/printk.hh"
 #include "kern/system_events.hh"
 #include "mem/se_translating_port_proxy.hh"
@@ -83,43 +84,25 @@ class DebugPrintk : public Base
 };
 
 /**
- * Dump the guest kernel's dmesg buffer to a file in gem5's output
- * directory and print a warning.
+ * Specify what to do on a Linux Kernel Panic or Oops.
  *
- * @warn This event uses linux::dumpDmesg() and comes with the same
+ * @warn This event may use linux::dumpDmesg() and comes with the same
  * limitations. Most importantly, the kernel's address mappings must
  * be available to the translating proxy.
  */
-class DmesgDump : public PCEvent
+class PanicOrOopsEvent : public PCEvent
 {
   protected:
     std::string fname;
+    KernelPanicOopsBehaviour behaviour;
 
   public:
-    DmesgDump(PCEventScope *s, const std::string &desc, Addr addr,
-              const std::string &_fname) :
-        PCEvent(s, desc, addr), fname(_fname)
-    {}
-    void process(ThreadContext *tc) override;
-};
-
-/**
- * Dump the guest kernel's dmesg buffer to a file in gem5's output
- * directory and panic.
- *
- * @warn This event uses linux::dumpDmesg() and comes with the same
- * limitations. Most importantly, the kernel's address mappings must
- * be available to the translating proxy.
- */
-class KernelPanic : public PCEvent
-{
-  protected:
-    std::string fname;
-
-  public:
-    KernelPanic(PCEventScope *s, const std::string &desc, Addr addr,
-                const std::string &_fname) :
-        PCEvent(s, desc, addr), fname(_fname)
+    PanicOrOopsEvent(PCEventScope *s, const std::string &desc, Addr addr,
+                     const std::string &_fname,
+                     const KernelPanicOopsBehaviour _behaviour)
+        : PCEvent(s, desc, addr)
+        , fname(_fname)
+        , behaviour(_behaviour)
     {}
     void process(ThreadContext *tc) override;
 };

src/sim/SConscript

@@ -1,5 +1,16 @@
 # -*- mode:python -*-
-
+# Copyright (c) 2023 Arm Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
 # Copyright (c) 2006 The Regents of The University of Michigan
 # All rights reserved.
 #
@@ -31,7 +42,8 @@ Import('*')
 SimObject('ClockedObject.py', sim_objects=['ClockedObject'])
 SimObject('TickedObject.py', sim_objects=['TickedObject'])
 SimObject('Workload.py', sim_objects=[
-    'Workload', 'StubWorkload', 'KernelWorkload', 'SEWorkload'])
+    'Workload', 'StubWorkload', 'KernelWorkload', 'SEWorkload'],
+          enums=['KernelPanicOopsBehaviour'])
 SimObject('Root.py', sim_objects=['Root'])
 SimObject('ClockDomain.py', sim_objects=[
     'ClockDomain', 'SrcClockDomain', 'DerivedClockDomain'])

src/sim/Workload.py

@@ -1,3 +1,15 @@
+# Copyright (c) 2023 Arm Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
 # Copyright 2019 Google Inc.
 #
 # Redistribution and use in source and binary forms, with or without
@@ -62,6 +74,16 @@ class StubWorkload(Workload):
     )
 
 
+class KernelPanicOopsBehaviour(ScopedEnum):
+    "Define what gem5 should do after a Kernel Panic or Oops."
+    vals = [
+        "Continue",
+        "DumpDmesgAndContinue",
+        "DumpDmesgAndExit",
+        "DumpDmesgAndPanic",
+    ]
+
+
 class KernelWorkload(Workload):
     type = "KernelWorkload"
     cxx_header = "sim/kernel_workload.hh"
@@ -86,6 +108,18 @@ class KernelWorkload(Workload):
 
     command_line = Param.String("a", "boot flags to pass to the kernel")
 
+    on_panic = Param.KernelPanicOopsBehaviour(
+        "DumpDmesgAndExit",
+        "Define how gem5 should behave after a Linux Kernel Panic. "
+        "Handler might not be implemented for all architectures.",
+    )
+
+    on_oops = Param.KernelPanicOopsBehaviour(
+        "DumpDmesgAndExit",
+        "Define how gem5 should behave after a Linux Kernel Oops. "
+        "Handler might not be implemented for all architectures.",
+    )
+
 
 class SEWorkloadMeta(type(Workload)):
     all_se_workload_classes = []