fix up access violation handling on windows; refactor posix segv handling to match API change needed for windows

src/compile.S

@@ -59,13 +59,6 @@ test:
    popq   %rbp
    ret
 
-.globl vmJump
-vmJump:
-   movq   %rsi,%rbp
-   movq   %rdx,%rsp
-   movq   %rcx,%rbx
-   jmp    *%rdi
-
 #elif defined __i386__
 
 #  if defined __APPLE__ || defined __MINGW32__
@@ -135,19 +128,6 @@ exit:
    movl   %ebp,%esp
    popl   %ebp
    ret
-     
-#  if defined __APPLE__ || defined __MINGW32__
-.globl _vmJump
-_vmJump: 
-#  else
-.globl vmJump
-vmJump:
-#  endif
-   movl   4(%esp),%eax
-   movl   8(%esp),%ebp
-   movl   16(%esp),%ebx
-   movl   12(%esp),%esp
-   jmp    *%eax
    
 #else
 #  error unsupported platform

src/compile.cpp

@@ -3,6 +3,7 @@
 #include "vector.h"
 #include "process.h"
 #include "compiler.h"
+#include "x86.h"
 
 using namespace vm;
 
@@ -13,9 +14,6 @@ vmInvoke(void* thread, void* function, void* stack, unsigned stackSize,
 extern "C" void
 vmCall();
 
-extern "C" void NO_RETURN
-vmJump(void* address, void* base, void* stack, void* thread);
-
 namespace {
 
 const bool Verbose = false;
@@ -996,8 +994,9 @@ class Frame {
   unsigned sp;
 };
 
-void NO_RETURN
-unwind(MyThread* t)
+void
+findUnwindTarget(MyThread* t, void** targetIp, void** targetBase,
+                 void** targetStack)
 {
   void* ip = t->ip;
   void* base = t->base;
@@ -1008,7 +1007,8 @@ unwind(MyThread* t)
     ip = *stack;
   }
 
-  while (true) {
+  *targetIp = 0;
+  while (*targetIp == 0) {
     object node = findTraceNode(t, ip);
     if (node) {
       object method = traceNodeMethod(t, node);
@@ -1028,7 +1028,9 @@ unwind(MyThread* t)
         *(--stack) = t->exception;
         t->exception = 0;
 
-        vmJump(compiled + exceptionHandlerIp(handler), base, stack, t);
+        *targetIp = compiled + exceptionHandlerIp(handler);
+        *targetBase = base;
+        *targetStack = stack;
       } else {
         if (methodFlags(t, method) & ACC_SYNCHRONIZED) {
           object lock;
@@ -1046,11 +1048,23 @@ unwind(MyThread* t)
         base = *static_cast<void**>(base);
       }
     } else {
-      vmJump(ip, base, stack + 1, 0);
+      *targetIp = ip;
+      *targetBase = base;
+      *targetStack = stack + 1;
     }
   }
 }
 
+void NO_RETURN
+unwind(MyThread* t)
+{
+  void* ip;
+  void* base;
+  void* stack;
+  findUnwindTarget(t, &ip, &base, &stack);
+  vmJump(ip, base, stack, t);
+}
+
 void
 insertTraceNode(MyThread* t, object method, object target, bool virtualCall,
                 uintptr_t* map, void* address)
@@ -3997,15 +4011,22 @@ class SegFaultHandler: public System::SignalHandler {
  public:
   SegFaultHandler(): m(0) { }
 
-  virtual void handleSignal(void* ip, void* base, void* stack) {
+  virtual bool handleSignal(void** ip, void** base, void** stack,
+                            void** thread)
+  {
     MyThread* t = static_cast<MyThread*>(m->localThread->get());
-    object node = findTraceNode(t, ip);
+    object node = findTraceNode(t, *ip);
     if (node) {
-      t->ip = ip;
-      t->base = base;
-      t->stack = stack;
+      t->ip = *ip;
+      t->base = *base;
+      t->stack = *stack;
       t->exception = makeNullPointerException(t);
-      unwind(t);
+
+      findUnwindTarget(t, ip, base, stack);
+      *thread = t;
+      return true;
+    } else {
+      return false;
     }
   }
 

src/posix.cpp

@@ -9,6 +9,7 @@
 #include "unistd.h"
 #include "pthread.h"
 #include "signal.h"
+#include "ucontext.h"
 #include "stdint.h"
 
 #include "x86.h"
@@ -43,10 +44,12 @@ const int InterruptSignal = SIGUSR2;
 const int IpRegister = REG_RIP;
 const int BaseRegister = REG_RBP;
 const int StackRegister = REG_RSP;
+const int ThreadRegister = REG_RBX;
 #elif defined __i386__
 const int IpRegister = REG_EIP;
 const int BaseRegister = REG_EBP;
 const int StackRegister = REG_ESP;
+const int ThreadRegister = REG_EBX;
 #else
 #  error unsupported architecture
 #endif
@@ -61,15 +64,26 @@ handleSignal(int signal, siginfo_t* info, void* context)
     sigaddset(&set, SIGSEGV);
     sigprocmask(SIG_UNBLOCK, &set, 0);
 
-    greg_t* registers
-      = static_cast<ucontext_t*>(context)->uc_mcontext.gregs;
+    ucontext_t* c = static_cast<ucontext_t*>(context);
 
-    segFaultHandler->handleSignal
-      (reinterpret_cast<void*>(registers[IpRegister]),
-       reinterpret_cast<void*>(registers[BaseRegister]),
-       reinterpret_cast<void*>(registers[StackRegister]));
+    greg_t* registers = c->uc_mcontext.gregs;
+    bool jump = segFaultHandler->handleSignal
+      (reinterpret_cast<void**>(registers + IpRegister),
+       reinterpret_cast<void**>(registers + BaseRegister),
+       reinterpret_cast<void**>(registers + StackRegister),
+       reinterpret_cast<void**>(registers + ThreadRegister));
 
-    if (oldSegFaultHandler.sa_flags & SA_SIGINFO) {
+    if (jump) {
+      // I'd like to use setcontext here (and get rid of the
+      // sigprocmask call above), but it doesn't work on my system,
+      // and I can't tell from the documentation if it's even supposed
+      // to work.
+
+      vmJump(reinterpret_cast<void*>(registers[IpRegister]),
+             reinterpret_cast<void*>(registers[BaseRegister]),
+             reinterpret_cast<void*>(registers[StackRegister]),
+             reinterpret_cast<void*>(registers[ThreadRegister]));
+    } else if (oldSegFaultHandler.sa_flags & SA_SIGINFO) {
       oldSegFaultHandler.sa_sigaction(signal, info, context);
     } else if (oldSegFaultHandler.sa_handler) {
       oldSegFaultHandler.sa_handler(signal);

src/system.h

@@ -84,7 +84,8 @@ class System: public Allocator {
    public:
     virtual ~SignalHandler() { }
 
-    virtual void handleSignal(void* ip, void* base, void* stack) = 0;
+    virtual bool handleSignal(void** ip, void** base, void** stack,
+                              void** thread) = 0;
   };
 
   virtual ~System() { }

src/windows.cpp

@@ -20,10 +20,15 @@ LONG CALLBACK
 handleException(LPEXCEPTION_POINTERS e)
 {
   if (e->ExceptionRecord->ExceptionCode == EXCEPTION_ACCESS_VIOLATION) {
-    segFaultHandler->handleSignal
-      (reinterpret_cast<void*>(e->ContextRecord->Eip),
-       reinterpret_cast<void*>(e->ContextRecord->Ebp),
-       reinterpret_cast<void*>(e->ContextRecord->Esp));
+    bool jump = segFaultHandler->handleSignal
+      (reinterpret_cast<void**>(&(e->ContextRecord->Eip)),
+       reinterpret_cast<void**>(&(e->ContextRecord->Ebp)),
+       reinterpret_cast<void**>(&(e->ContextRecord->Esp)),
+       reinterpret_cast<void**>(&(e->ContextRecord->Ebx)));
+
+    if (jump) {
+      return EXCEPTION_CONTINUE_EXECUTION;
+    }
   }
   return EXCEPTION_CONTINUE_SEARCH;
 }

src/x86.S

@@ -106,6 +106,13 @@ exit:
    popq   %rbp
    ret
 
+.globl vmJump
+vmJump:
+   movq   %rsi,%rbp
+   movq   %rdx,%rsp
+   movq   %rcx,%rbx
+   jmp    *%rdi
+
 #elif defined __i386__
 
 #  if defined __APPLE__ || defined __MINGW32__
@@ -184,6 +191,19 @@ exit:
    movl   %ebp,%esp
    popl   %ebp
    ret
+     
+#  if defined __APPLE__ || defined __MINGW32__
+.globl _vmJump
+_vmJump:
+#  else
+.globl vmJump
+vmJump:
+#  endif
+   movl   4(%esp),%eax
+   movl   8(%esp),%ebp
+   movl   16(%esp),%ebx
+   movl   12(%esp),%esp
+   jmp    *%eax
 
 #else
 #  error unsupported platform

src/x86.h

@@ -3,6 +3,10 @@
 
 #include "types.h"
 #include "stdint.h"
+#include "common.h"
+
+extern "C" void NO_RETURN
+vmJump(void* address, void* base, void* stack, void* thread);
 
 #ifdef __i386__