misc: Generalize GDB single stepping.

The new single stepping implementation for x86 doesn't rely on any ISA
specific properties or functionality. This change pulls out the per ISA
implementation of those functions and promotes the X86 implementation to the
base class.

One drawback of that implementation is that the CPU might stop on an
instruction twice if it's affected by both breakpoints and single stepping.
While that might be a little surprising, it's harmless and would only happen
under somewhat unlikely circumstances.

13 files changed, 52 insertions, 234 deletions

diff --git a/src/arch/alpha/remote_gdb.cc b/src/arch/alpha/remote_gdb.cc
index 951a20982..a3fcf6136 100644
--- a/src/arch/alpha/remote_gdb.cc
+++ b/src/arch/alpha/remote_gdb.cc
@@ -255,46 +255,6 @@ RemoteGDB::setregs()
     context->pcState(gdbregs.regs64[KGDB_REG_PC]);
 }
 
-void
-RemoteGDB::clearSingleStep()
-{
-    DPRINTF(GDBMisc, "clearSingleStep bt_addr=%#x nt_addr=%#x\n",
-            takenBkpt, notTakenBkpt);
-
-    if (takenBkpt != 0)
-        clearTempBreakpoint(takenBkpt);
-
-    if (notTakenBkpt != 0)
-        clearTempBreakpoint(notTakenBkpt);
-}
-
-void
-RemoteGDB::setSingleStep()
-{
-    PCState pc = context->pcState();
-    PCState bpc;
-    bool set_bt = false;
-
-    // User was stopped at pc, e.g. the instruction at pc was not
-    // executed.
-    MachInst inst = read<MachInst>(pc.pc());
-    StaticInstPtr si = context->getDecoderPtr()->decode(inst, pc.pc());
-    if (si->hasBranchTarget(pc, context, bpc)) {
-        // Don't bother setting a breakpoint on the taken branch if it
-        // is the same as the next pc
-        if (bpc.pc() != pc.npc())
-            set_bt = true;
-    }
-
-    DPRINTF(GDBMisc, "setSingleStep bt_addr=%#x nt_addr=%#x\n",
-            takenBkpt, notTakenBkpt);
-
-    setTempBreakpoint(notTakenBkpt = pc.npc());
-
-    if (set_bt)
-        setTempBreakpoint(takenBkpt = bpc.pc());
-}
-
 // Write bytes to kernel address space for debugger.
 bool
 RemoteGDB::write(Addr vaddr, size_t size, const char *data)
diff --git a/src/arch/alpha/remote_gdb.hh b/src/arch/alpha/remote_gdb.hh
index d9c124c72..33994653d 100644
--- a/src/arch/alpha/remote_gdb.hh
+++ b/src/arch/alpha/remote_gdb.hh
@@ -48,21 +48,14 @@ namespace AlphaISA {
 class RemoteGDB : public BaseRemoteGDB
 {
   protected:
-    Addr notTakenBkpt;
-    Addr takenBkpt;
-
-  protected:
     void getregs();
     void setregs();
 
-    void clearSingleStep();
-    void setSingleStep();
-
     // Machine memory
     bool acc(Addr addr, size_t len);
     bool write(Addr addr, size_t size, const char *data);
 
-    virtual bool insertHardBreak(Addr addr, size_t len);
+    bool insertHardBreak(Addr addr, size_t len);
 
   public:
     RemoteGDB(System *system, ThreadContext *context);
diff --git a/src/arch/arm/remote_gdb.cc b/src/arch/arm/remote_gdb.cc
index fce060311..1686cab39 100644
--- a/src/arch/arm/remote_gdb.cc
+++ b/src/arch/arm/remote_gdb.cc
@@ -161,8 +161,7 @@ using namespace std;
 using namespace ArmISA;
 
 RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc)
-    : BaseRemoteGDB(_system, tc, GDB_REG_BYTES),
-      notTakenBkpt(0), takenBkpt(0)
+    : BaseRemoteGDB(_system, tc, GDB_REG_BYTES)
 {
 }
 
@@ -314,46 +313,6 @@ RemoteGDB::setregs()
     }
 }
 
-void
-RemoteGDB::clearSingleStep()
-{
-    DPRINTF(GDBMisc, "clearSingleStep bt_addr=%#x nt_addr=%#x\n",
-            takenBkpt, notTakenBkpt);
-
-    if (takenBkpt != 0)
-        clearTempBreakpoint(takenBkpt);
-
-    if (notTakenBkpt != 0)
-        clearTempBreakpoint(notTakenBkpt);
-}
-
-void
-RemoteGDB::setSingleStep()
-{
-    PCState pc = context->pcState();
-    PCState bpc;
-    bool set_bt = false;
-
-    // User was stopped at pc, e.g. the instruction at pc was not
-    // executed.
-    MachInst inst = read<MachInst>(pc.pc());
-    StaticInstPtr si = context->getDecoderPtr()->decode(inst, pc.pc());
-    if (si->hasBranchTarget(pc, context, bpc)) {
-        // Don't bother setting a breakpoint on the taken branch if it
-        // is the same as the next pc
-        if (bpc.pc() != pc.npc())
-            set_bt = true;
-    }
-
-    DPRINTF(GDBMisc, "setSingleStep bt_addr=%#x nt_addr=%#x\n",
-            takenBkpt, notTakenBkpt);
-
-    setTempBreakpoint(notTakenBkpt = pc.npc());
-
-    if (set_bt)
-        setTempBreakpoint(takenBkpt = bpc.pc());
-}
-
 // Write bytes to kernel address space for debugger.
 bool
 RemoteGDB::write(Addr vaddr, size_t size, const char *data)
diff --git a/src/arch/arm/remote_gdb.hh b/src/arch/arm/remote_gdb.hh
index 423ba9d02..80a0bf1b1 100644
--- a/src/arch/arm/remote_gdb.hh
+++ b/src/arch/arm/remote_gdb.hh
@@ -80,23 +80,15 @@ const int GDB_REG_BYTES = std::max(GDB64_NUMREGS * sizeof(uint64_t),
 
 class RemoteGDB : public BaseRemoteGDB
 {
+  protected:
+    bool acc(Addr addr, size_t len);
+    bool write(Addr addr, size_t size, const char *data);
 
-protected:
-  Addr notTakenBkpt;
-  Addr takenBkpt;
+    void getregs();
+    void setregs();
 
-protected:
-  bool acc(Addr addr, size_t len);
-  bool write(Addr addr, size_t size, const char *data);
-
-  void getregs();
-  void setregs();
-
-  void clearSingleStep();
-  void setSingleStep();
-
-public:
-  RemoteGDB(System *_system, ThreadContext *tc);
+  public:
+    RemoteGDB(System *_system, ThreadContext *tc);
 };
 } // namespace ArmISA
 
diff --git a/src/arch/mips/remote_gdb.cc b/src/arch/mips/remote_gdb.cc
index 9c944fc59..a7bde8ba6 100644
--- a/src/arch/mips/remote_gdb.cc
+++ b/src/arch/mips/remote_gdb.cc
@@ -235,47 +235,3 @@ RemoteGDB::setregs()
     context->setFloatRegBits(FLOATREG_FIR,
         gdbregs.regs32[GdbIntRegs + GdbFloatArchRegs + 1]);
 }
-
-void
-RemoteGDB::clearSingleStep()
-{
-    DPRINTF(GDBMisc, "clearSingleStep bt_addr=%#x nt_addr=%#x\n",
-            takenBkpt, notTakenBkpt);
-
-    if (takenBkpt != 0)
-        clearTempBreakpoint(takenBkpt);
-
-    if (notTakenBkpt != 0)
-        clearTempBreakpoint(notTakenBkpt);
-}
-
-void
-RemoteGDB::setSingleStep()
-{
-    PCState pc = context->pcState();
-    PCState bpc;
-    bool set_bt = false;
-
-    // User was stopped at pc, e.g. the instruction at pc was not
-    // executed.
-    MachInst inst = read<MachInst>(pc.pc());
-    StaticInstPtr si = context->getDecoderPtr()->decode(inst, pc.pc());
-    if (si->hasBranchTarget(pc, context, bpc)) {
-        // Don't bother setting a breakpoint on the taken branch if it
-        // is the same as the next npc
-        if (bpc.npc() != pc.nnpc())
-            set_bt = true;
-    }
-
-    DPRINTF(GDBMisc, "setSingleStep bt_addr=%#x nt_addr=%#x\n",
-            takenBkpt, notTakenBkpt);
-
-    notTakenBkpt = pc.nnpc();
-    setTempBreakpoint(notTakenBkpt);
-
-    if (set_bt) {
-        takenBkpt = bpc.npc();
-        setTempBreakpoint(takenBkpt);
-    }
-}
-
diff --git a/src/arch/mips/remote_gdb.hh b/src/arch/mips/remote_gdb.hh
index 157276dcf..8d113eb99 100644
--- a/src/arch/mips/remote_gdb.hh
+++ b/src/arch/mips/remote_gdb.hh
@@ -54,10 +54,6 @@ namespace MipsISA
 
     class RemoteGDB : public BaseRemoteGDB
     {
-      protected:
-        Addr notTakenBkpt;
-        Addr takenBkpt;
-
       public:
         RemoteGDB(System *_system, ThreadContext *tc);
 
@@ -66,9 +62,6 @@ namespace MipsISA
 
         void getregs();
         void setregs();
-
-        void clearSingleStep();
-        void setSingleStep();
     };
 }
 
diff --git a/src/arch/power/remote_gdb.hh b/src/arch/power/remote_gdb.hh
index b37c31713..fa82af95b 100644
--- a/src/arch/power/remote_gdb.hh
+++ b/src/arch/power/remote_gdb.hh
@@ -65,18 +65,6 @@ class RemoteGDB : public BaseRemoteGDB
     {
         panic("setregs not implemented for POWER!");
     }
-
-    void
-    clearSingleStep()
-    {
-        panic("clearSingleStep not implemented for POWER!");
-    }
-
-    void
-    setSingleStep()
-    {
-        panic("setSingleStep not implemented for POWER!");
-    }
 };
 
 } // namespace PowerISA
diff --git a/src/arch/sparc/remote_gdb.cc b/src/arch/sparc/remote_gdb.cc
index 778c20731..e654741b6 100644
--- a/src/arch/sparc/remote_gdb.cc
+++ b/src/arch/sparc/remote_gdb.cc
@@ -144,7 +144,7 @@ using namespace std;
 using namespace SparcISA;
 
 RemoteGDB::RemoteGDB(System *_system, ThreadContext *c)
-    : BaseRemoteGDB(_system, c, NumGDBRegs * sizeof(uint64_t)), nextBkpt(0)
+    : BaseRemoteGDB(_system, c, NumGDBRegs * sizeof(uint64_t))
 {}
 
 ///////////////////////////////////////////////////////////
@@ -241,17 +241,3 @@ RemoteGDB::setregs()
         context->setIntReg(x - RegG0, gdbregs.regs64[x]);
     // Only the integer registers, pc and npc are set in netbsd
 }
-
-void
-RemoteGDB::clearSingleStep()
-{
-   if (nextBkpt)
-       clearTempBreakpoint(nextBkpt);
-}
-
-void
-RemoteGDB::setSingleStep()
-{
-    nextBkpt = context->pcState().npc();
-    setTempBreakpoint(nextBkpt);
-}
diff --git a/src/arch/sparc/remote_gdb.hh b/src/arch/sparc/remote_gdb.hh
index 0176fd323..46aa03a93 100644
--- a/src/arch/sparc/remote_gdb.hh
+++ b/src/arch/sparc/remote_gdb.hh
@@ -66,11 +66,6 @@ class RemoteGDB : public BaseRemoteGDB
   protected:
     void getregs();
     void setregs();
-
-    void clearSingleStep();
-    void setSingleStep();
-
-    Addr nextBkpt;
 };
 
 }
diff --git a/src/arch/x86/remote_gdb.cc b/src/arch/x86/remote_gdb.cc
index b30bf5739..dd96037e0 100644
--- a/src/arch/x86/remote_gdb.cc
+++ b/src/arch/x86/remote_gdb.cc
@@ -61,7 +61,7 @@ using namespace std;
 using namespace X86ISA;
 
 RemoteGDB::RemoteGDB(System *_system, ThreadContext *c) :
-    BaseRemoteGDB(_system, c, GDB_REG_BYTES), singleStepEvent(this)
+    BaseRemoteGDB(_system, c, GDB_REG_BYTES)
 {}
 
 bool
@@ -89,14 +89,6 @@ RemoteGDB::acc(Addr va, size_t len)
 }
 
 void
-RemoteGDB::SingleStepEvent::process()
-{
-    if (!gdb->singleStepEvent.scheduled())
-        gdb->scheduleInstCommitEvent(&gdb->singleStepEvent, 1);
-    gdb->trap(SIGTRAP);
-}
-
-void
 RemoteGDB::getregs()
 {
     HandyM5Reg m5reg = context->readMiscRegNoEffect(MISCREG_M5_REG);
@@ -231,16 +223,3 @@ RemoteGDB::setregs()
         }
     }
 }
-
-void
-RemoteGDB::clearSingleStep()
-{
-    descheduleInstCommitEvent(&singleStepEvent);
-}
-
-void
-RemoteGDB::setSingleStep()
-{
-    if (!singleStepEvent.scheduled())
-        scheduleInstCommitEvent(&singleStepEvent, 1);
-}
diff --git a/src/arch/x86/remote_gdb.hh b/src/arch/x86/remote_gdb.hh
index b654fc2f8..f09d1e012 100644
--- a/src/arch/x86/remote_gdb.hh
+++ b/src/arch/x86/remote_gdb.hh
@@ -116,26 +116,9 @@ class RemoteGDB : public BaseRemoteGDB
     bool acc(Addr addr, size_t len);
 
   protected:
-    class SingleStepEvent : public Event
-    {
-      protected:
-        RemoteGDB *gdb;
-
-      public:
-        SingleStepEvent(RemoteGDB *g) : gdb(g)
-        {}
-
-        void process();
-    };
-
-    SingleStepEvent singleStepEvent;
-
     void getregs();
     void setregs();
 
-    void clearSingleStep();
-    void setSingleStep();
-
     bool checkBpLen(size_t len) { return len == 1; }
 };
 
diff --git a/src/base/remote_gdb.cc b/src/base/remote_gdb.cc
index 97d763803..e603fb90f 100644
--- a/src/base/remote_gdb.cc
+++ b/src/base/remote_gdb.cc
@@ -262,11 +262,18 @@ BaseRemoteGDB::TrapEvent::process()
     gdb->trap(_type);
 }
 
-BaseRemoteGDB::BaseRemoteGDB(System *_system, ThreadContext *c, size_t cacheSize)
-    : inputEvent(NULL), trapEvent(this), listener(NULL), number(-1), fd(-1),
-      active(false), attached(false),
-      system(_system), context(c),
-      gdbregs(cacheSize)
+void
+BaseRemoteGDB::SingleStepEvent::process()
+{
+    if (!gdb->singleStepEvent.scheduled())
+        gdb->scheduleInstCommitEvent(&gdb->singleStepEvent, 1);
+    gdb->trap(SIGTRAP);
+}
+
+BaseRemoteGDB::BaseRemoteGDB(System *_system, ThreadContext *c,
+        size_t cacheSize) : inputEvent(NULL), trapEvent(this), listener(NULL),
+        number(-1), fd(-1), active(false), attached(false), system(_system),
+        context(c), gdbregs(cacheSize), singleStepEvent(this)
 {
     memset(gdbregs.regs, 0, gdbregs.bytes());
 }
@@ -525,6 +532,19 @@ BaseRemoteGDB::write(Addr vaddr, size_t size, const char *data)
     return true;
 }
 
+void
+BaseRemoteGDB::clearSingleStep()
+{
+    descheduleInstCommitEvent(&singleStepEvent);
+}
+
+void
+BaseRemoteGDB::setSingleStep()
+{
+    if (!singleStepEvent.scheduled())
+        scheduleInstCommitEvent(&singleStepEvent, 1);
+}
+
 PCEventQueue *BaseRemoteGDB::getPcEventQueue()
 {
     return &system->pcEventQueue;
diff --git a/src/base/remote_gdb.hh b/src/base/remote_gdb.hh
index 62f98f29a..6cca485e3 100644
--- a/src/base/remote_gdb.hh
+++ b/src/base/remote_gdb.hh
@@ -209,11 +209,25 @@ class BaseRemoteGDB
     }
 
   protected:
+    class SingleStepEvent : public Event
+    {
+      protected:
+        BaseRemoteGDB *gdb;
+
+      public:
+        SingleStepEvent(BaseRemoteGDB *g) : gdb(g)
+        {}
+
+        void process();
+    };
+
+    SingleStepEvent singleStepEvent;
+
     virtual void getregs() = 0;
     virtual void setregs() = 0;
 
-    virtual void clearSingleStep() = 0;
-    virtual void setSingleStep() = 0;
+    void clearSingleStep();
+    void setSingleStep();
 
     PCEventQueue *getPcEventQueue();
     EventQueue *getComInstEventQueue();