arch,base,sim: Construct the GDB stub with no threads.

By moving the installation of even the first ThreadContext out of the
constructor, it's possible to construct the stub separately. We can then
move the code that creates the stub out of the base class and into
architecture specific sub-classes.

Change-Id: I0dfd53a3135ebc98ec49acf81d83e58830bc365c
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/44618
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>

src/arch/arm/remote_gdb.cc

@@ -184,8 +184,8 @@ tryTranslate(ThreadContext *tc, Addr addr)
            mmu->translateFunctional(req, tc, BaseTLB::Execute) == NoFault;
 }
 
-RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc, int _port)
-    : BaseRemoteGDB(_system, tc, _port), regCache32(this), regCache64(this)
+RemoteGDB::RemoteGDB(System *_system, int _port)
+    : BaseRemoteGDB(_system, _port), regCache32(this), regCache64(this)
 {
 }
 

src/arch/arm/remote_gdb.hh

@@ -115,7 +115,7 @@ class RemoteGDB : public BaseRemoteGDB
     AArch64GdbRegCache regCache64;
 
   public:
-    RemoteGDB(System *_system, ThreadContext *tc, int _port);
+    RemoteGDB(System *_system, int _port);
     BaseGdbRegCache *gdbRegs();
     std::vector<std::string>
     availableFeatures() const

src/arch/mips/remote_gdb.cc

@@ -148,8 +148,8 @@
 
 using namespace MipsISA;
 
-RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc, int _port)
-    : BaseRemoteGDB(_system, tc, _port), regCache(this)
+RemoteGDB::RemoteGDB(System *_system, int _port)
+    : BaseRemoteGDB(_system, _port), regCache(this)
 {
 }
 

src/arch/mips/remote_gdb.hh

@@ -77,7 +77,7 @@ class RemoteGDB : public BaseRemoteGDB
     MipsGdbRegCache regCache;
 
   public:
-    RemoteGDB(System *_system, ThreadContext *tc, int _port);
+    RemoteGDB(System *_system, int _port);
     BaseGdbRegCache *gdbRegs();
     std::vector<std::string>
     availableFeatures() const

src/arch/power/remote_gdb.cc

@@ -145,8 +145,8 @@
 
 using namespace PowerISA;
 
-RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc, int _port)
-    : BaseRemoteGDB(_system, tc, _port), regCache(this)
+RemoteGDB::RemoteGDB(System *_system, int _port)
+    : BaseRemoteGDB(_system, _port), regCache(this)
 {
 }
 

src/arch/power/remote_gdb.hh

@@ -76,7 +76,7 @@ class RemoteGDB : public BaseRemoteGDB
     PowerGdbRegCache regCache;
 
   public:
-    RemoteGDB(System *_system, ThreadContext *tc, int _port);
+    RemoteGDB(System *_system, int _port);
     BaseGdbRegCache *gdbRegs();
     std::vector<std::string>
     availableFeatures() const

src/arch/riscv/remote_gdb.cc

@@ -152,8 +152,8 @@
 
 using namespace RiscvISA;
 
-RemoteGDB::RemoteGDB(System *_system, ThreadContext *tc, int _port)
-    : BaseRemoteGDB(_system, tc, _port), regCache(this)
+RemoteGDB::RemoteGDB(System *_system, int _port)
+    : BaseRemoteGDB(_system, _port), regCache(this)
 {
 }
 

src/arch/riscv/remote_gdb.hh

@@ -142,7 +142,7 @@ class RemoteGDB : public BaseRemoteGDB
     RiscvGdbRegCache regCache;
 
   public:
-    RemoteGDB(System *_system, ThreadContext *tc, int _port);
+    RemoteGDB(System *_system, int _port);
     BaseGdbRegCache *gdbRegs() override;
     /**
      * Informs GDB remote serial protocol that XML features are supported

src/arch/sparc/remote_gdb.cc

@@ -144,8 +144,8 @@
 
 using namespace SparcISA;
 
-RemoteGDB::RemoteGDB(System *_system, ThreadContext *c, int _port)
-    : BaseRemoteGDB(_system, c, _port), regCache32(this), regCache64(this)
+RemoteGDB::RemoteGDB(System *_system, int _port)
+    : BaseRemoteGDB(_system, _port), regCache32(this), regCache64(this)
 {}
 
 ///////////////////////////////////////////////////////////

src/arch/sparc/remote_gdb.hh

@@ -105,7 +105,7 @@ class RemoteGDB : public BaseRemoteGDB
     SPARC64GdbRegCache regCache64;
 
   public:
-    RemoteGDB(System *_system, ThreadContext *tc, int _port);
+    RemoteGDB(System *_system, int _port);
     BaseGdbRegCache *gdbRegs();
 };
 } // namespace SparcISA

src/arch/x86/remote_gdb.cc

@@ -63,8 +63,8 @@
 
 using namespace X86ISA;
 
-RemoteGDB::RemoteGDB(System *_system, ThreadContext *c, int _port) :
-    BaseRemoteGDB(_system, c, _port), regCache32(this), regCache64(this)
+RemoteGDB::RemoteGDB(System *_system, int _port) :
+    BaseRemoteGDB(_system, _port), regCache32(this), regCache64(this)
 {}
 
 bool

src/arch/x86/remote_gdb.hh

@@ -143,7 +143,7 @@ class RemoteGDB : public BaseRemoteGDB
     AMD64GdbRegCache regCache64;
 
   public:
-    RemoteGDB(System *system, ThreadContext *context, int _port);
+    RemoteGDB(System *system, int _port);
     BaseGdbRegCache *gdbRegs();
 };
 } // namespace X86ISA

src/base/remote_gdb.cc

@@ -349,12 +349,10 @@ std::map<Addr, HardBreakpoint *> hardBreakMap;
 
 }
 
-BaseRemoteGDB::BaseRemoteGDB(System *_system, ThreadContext *c, int _port) :
+BaseRemoteGDB::BaseRemoteGDB(System *_system, int _port) :
         connectEvent(nullptr), dataEvent(nullptr), _port(_port), fd(-1),
         sys(_system), trapEvent(this), singleStepEvent(*this)
-{
-    addThreadContext(c);
-}
+{}
 
 BaseRemoteGDB::~BaseRemoteGDB()
 {
@@ -392,7 +390,7 @@ void
 BaseRemoteGDB::connect()
 {
     panic_if(!listener.islistening(),
-             "Cannot accept GDB connections if we're not listening!");
+             "Can't accept GDB connections without any threads!");
 
     int sfd = listener.accept(true);
 
@@ -445,6 +443,10 @@ BaseRemoteGDB::addThreadContext(ThreadContext *_tc)
     // If no ThreadContext is current selected, select this one.
     if (!tc)
         assert(selectThreadContext(_tc->contextId()));
+
+    // Now that we have a thread, we can start listening.
+    if (!listener.islistening())
+        listen();
 }
 
 void

src/base/remote_gdb.hh

@@ -149,7 +149,7 @@ class BaseRemoteGDB
     /**
      * Interface to other parts of the simulator.
      */
-    BaseRemoteGDB(System *system, ThreadContext *context, int _port);
+    BaseRemoteGDB(System *system, int _port);
     virtual ~BaseRemoteGDB();
 
     std::string name();

src/sim/system.cc

@@ -212,7 +212,7 @@ System::System(const Params &p)
       redirectPaths(p.redirect_paths)
 {
     if (workload)
-        workload->system = this;
+        workload->setSystem(this);
 
     // add self to global system list
     systemList.push_back(this);

src/sim/workload.cc

@@ -32,6 +32,18 @@
 #include "cpu/thread_context.hh"
 #include "sim/debug.hh"
 
+void
+Workload::setSystem(System *sys)
+{
+    system = sys;
+
+#   if THE_ISA != NULL_ISA
+    int port = getRemoteGDBPort();
+    if (port)
+        gdb = new TheISA::RemoteGDB(system, port);
+#   endif
+}
+
 void
 Workload::registerThreadContext(ThreadContext *tc)
 {
@@ -42,13 +54,8 @@ Workload::registerThreadContext(ThreadContext *tc)
             tc->contextId());
 
 #   if THE_ISA != NULL_ISA
-    int port = getRemoteGDBPort();
-    if (port && !gdb) {
-        gdb = new TheISA::RemoteGDB(system, tc, port);
-        gdb->listen();
-    } else if (gdb) {
+    if (gdb)
         gdb->addThreadContext(tc);
-    }
 #   endif
 }
 

src/sim/workload.hh

@@ -71,11 +71,15 @@ class Workload : public SimObject
     bool waitForRemoteGDB = false;
     std::set<ThreadContext *> threads;
 
+    System *system = nullptr;
+
   public:
     Workload(const WorkloadParams &params) : SimObject(params), stats(this),
             waitForRemoteGDB(params.wait_for_remote_gdb)
     {}
 
+    void setSystem(System *sys);
+
     void recordQuiesce() { stats.instStats.quiesce++; }
     void recordArm() { stats.instStats.arm++; }
 
@@ -83,8 +87,6 @@ class Workload : public SimObject
     // system object, this helper can be removed.
     bool trapToGdb(int signal, ContextID ctx_id);
 
-    System *system = nullptr;
-
     virtual void registerThreadContext(ThreadContext *tc);
     virtual void replaceThreadContext(ThreadContext *tc);