ARM: Adding a bogus fault that does nothing.

This fault can used to flush the pipe, not including the faulting instruction.

The particular case I needed this was for a self-modifying code. It needed to
drain the store queue and force the following instruction to refetch from
icache. DCCMVAC cp15 mcr instruction is modified to raise this fault.

2 files changed, 31 insertions, 1 deletions

diff --git a/src/arch/arm/isa/formats/misc.isa b/src/arch/arm/isa/formats/misc.isa
index 884d93066..2d47c286f 100644
--- a/src/arch/arm/isa/formats/misc.isa
+++ b/src/arch/arm/isa/formats/misc.isa
@@ -111,7 +111,7 @@ let {{
             return new WarnUnimplemented(
                     isRead ? "mrc dcimvac" : "mcr dcimvac", machInst);
           case MISCREG_DCCMVAC:
-            return new WarnUnimplemented(
+            return new FlushPipeInst(
                     isRead ? "mrc dccmvac" : "mcr dccmvac", machInst);
           case MISCREG_DCCMVAU:
             return new WarnUnimplemented(
diff --git a/src/arch/arm/isa/formats/unimp.isa b/src/arch/arm/isa/formats/unimp.isa
index a746f8a7b..a0e0afd32 100644
--- a/src/arch/arm/isa/formats/unimp.isa
+++ b/src/arch/arm/isa/formats/unimp.isa
@@ -101,6 +101,22 @@ output header {{
         std::string
         generateDisassembly(Addr pc, const SymbolTable *symtab) const;
     };
+
+    class FlushPipeInst : public ArmStaticInst
+    {
+      public:
+        FlushPipeInst(const char *_mnemonic, ExtMachInst _machInst)
+            : ArmStaticInst(_mnemonic, _machInst, No_OpClass)
+        {
+            flags[IsNonSpeculative] = true;
+        }
+
+        %(BasicExecDeclare)s
+
+        std::string
+        generateDisassembly(Addr pc, const SymbolTable *symtab) const;
+
+    };
 }};
 
 output decoder {{
@@ -117,6 +133,13 @@ output decoder {{
     {
         return csprintf("%-10s (unimplemented)", mnemonic);
     }
+
+    std::string
+    FlushPipeInst::generateDisassembly(Addr pc,
+                                   const SymbolTable *symtab) const
+    {
+        return csprintf("%-10s (pipe flush)", mnemonic);
+    }
 }};
 
 output exec {{
@@ -142,6 +165,13 @@ output exec {{
 
         return NoFault;
     }
+
+    Fault
+    FlushPipeInst::execute(%(CPU_exec_context)s *xc,
+                           Trace::InstRecord *traceData) const
+    {
+        return new FlushPipe();
+    }
 }};