sim: revamp unserialization procedure

Replace direct call to unserialize() on each SimObject with a pair of
calls for better control over initialization in both ckpt and non-ckpt
cases.

If restoring from a checkpoint, loadState(ckpt) is called on each
SimObject.  The default implementation simply calls unserialize() if
there is a corresponding checkpoint section, so we get backward
compatibility for existing objects.  However, objects can override
loadState() to get other behaviors, e.g., doing other programmed
initializations after unserialize(), or complaining if no checkpoint
section is found.  (Note that the default warning for a missing
checkpoint section is now gone.)

If not restoring from a checkpoint, we call the new initState() method
on each SimObject instead.  This provides a hook for state
initializations that are only required when *not* restoring from a
checkpoint.

Given this new framework, do some cleanup of LiveProcess subclasses
and X86System, which were (in some cases) emulating initState()
behavior in startup via a local flag or (in other cases) erroneously
doing initializations in startup() that clobbered state loaded earlier
by unserialize().

2 files changed, 26 insertions, 6 deletions

diff --git a/src/arch/alpha/process.cc b/src/arch/alpha/process.cc
index 1c83f64b2..431ef86c0 100644
--- a/src/arch/alpha/process.cc
+++ b/src/arch/alpha/process.cc
@@ -173,19 +173,35 @@ AlphaLiveProcess::argsInit(int intSize, int pageSize)
 }
 
 void
-AlphaLiveProcess::startup()
+AlphaLiveProcess::setupASNReg()
 {
     ThreadContext *tc = system->getThreadContext(contextIds[0]);
     tc->setMiscRegNoEffect(IPR_DTB_ASN, M5_pid << 57);
+}
 
-    if (checkpointRestored) {
-        return;
-    }
 
-    Process::startup();
+void
+AlphaLiveProcess::loadState(Checkpoint *cp)
+{
+    LiveProcess::loadState(cp);
+    // need to set up ASN after unserialization since M5_pid value may
+    // come from checkpoint
+    setupASNReg();
+}
+
+
+void
+AlphaLiveProcess::initState()
+{
+    // need to set up ASN before further initialization since init
+    // will involve writing to virtual memory addresses
+    setupASNReg();
+
+    LiveProcess::initState();
 
     argsInit(MachineBytes, VMPageSize);
 
+    ThreadContext *tc = system->getThreadContext(contextIds[0]);
     tc->setIntReg(GlobalPointerReg, objFile->globalPointer());
     //Operate in user mode
     tc->setMiscRegNoEffect(IPR_ICM, 0x18);
diff --git a/src/arch/alpha/process.hh b/src/arch/alpha/process.hh
index 36b25a48e..40d6bf48a 100644
--- a/src/arch/alpha/process.hh
+++ b/src/arch/alpha/process.hh
@@ -36,10 +36,14 @@
 
 class AlphaLiveProcess : public LiveProcess
 {
+  private:
+    void setupASNReg();
+
   protected:
     AlphaLiveProcess(LiveProcessParams *params, ObjectFile *objFile);
 
-    void startup();
+    void loadState(Checkpoint *cp);
+    void initState();
 
     void argsInit(int intSize, int pageSize);