added back sigsegv handler

CMakeLists.txt

@@ -140,11 +140,20 @@ set(DREAVM_SOURCES
   src/renderer/gl_shader.cc
   src/sys/files.cc
   src/sys/keys.cc
+  src/sys/sigsegv_handler.cc
   src/sys/system.cc
   src/trace/trace.cc
   src/trace/trace_viewer.cc
   src/main.cc)
 
+if(WIN32)
+  list(APPEND DREAVM_SOURCES src/sys/sigsegv_handler_win.cc)
+elseif(APPLE)
+  list(APPEND DREAVM_SOURCES src/sys/sigsegv_handler_mac.cc)
+else()
+  list(APPEND DREAVM_SOURCES src/sys/sigsegv_handler_linux.cc)
+endif()
+
 
 # assign source groups for visual studio projects
 source_group_by_dir(DREAVM_SOURCES)

src/hw/dreamcast.cc

@@ -103,6 +103,10 @@ Dreamcast::~Dreamcast() {
 }
 
 bool Dreamcast::Init() {
+  if (!(sigsegv_ = SIGSEGVHandler::Install())) {
+    return false;
+  }
+
   MapMemory();
 
   if (!aica_->Init()) {

src/hw/dreamcast.h

@@ -16,6 +16,7 @@
 #include "jit/frontend/frontend.h"
 #include "jit/runtime.h"
 #include "renderer/backend.h"
+#include "sys/sigsegv_handler.h"
 #include "trace/trace.h"
 
 namespace dreavm {
@@ -120,6 +121,8 @@ class Dreamcast {
   hw::holly::TextureCache *texcache() { return texcache_; }
   hw::holly::TileRenderer *tile_renderer() { return tile_renderer_; }
 
+  sys::SIGSEGVHandler *sigsegv() { return sigsegv_; }
+
   renderer::Backend *rb() { return rb_; }
   void set_rb(renderer::Backend *rb) { rb_ = rb; }
 
@@ -179,6 +182,7 @@ class Dreamcast {
   hw::holly::TileRenderer *tile_renderer_;
 
   // not owned by us
+  sys::SIGSEGVHandler *sigsegv_;
   renderer::Backend *rb_;
   trace::TraceWriter *trace_writer_;
 };

src/sys/sigsegv_handler.cc

@@ -0,0 +1,75 @@
+#include "core/core.h"
+#include "core/interval_tree.h"
+#include "emu/profiler.h"
+#include "sys/sigsegv_handler.h"
+
+using namespace dreavm::sys;
+
+SIGSEGVHandler *dreavm::sys::SIGSEGVHandler::global_handler_ = nullptr;
+
+SIGSEGVHandler *SIGSEGVHandler::Install() {
+  if (global_handler_) {
+    return global_handler_;
+  }
+
+  global_handler_ = CreateSIGSEGVHandler();
+
+  if (!global_handler_->Init()) {
+    LOG_WARNING("Failed to install SIGSEGV handler");
+
+    delete global_handler_;
+    global_handler_ = nullptr;
+  }
+
+  return global_handler_;
+}
+
+SIGSEGVHandler::~SIGSEGVHandler() { global_handler_ = nullptr; }
+
+void SIGSEGVHandler::AddWriteWatch(void *ptr, int size,
+                                   WriteWatchHandler handler, void *ctx,
+                                   void *data) {
+  int page_size = GetPageSize();
+  uintptr_t physical_start = dreavm::align(reinterpret_cast<uintptr_t>(ptr),
+                                           static_cast<uintptr_t>(page_size));
+  uintptr_t physical_end =
+      dreavm::align(reinterpret_cast<uintptr_t>(ptr) + size,
+                    static_cast<uintptr_t>(page_size));
+
+  // write protect the pages
+  CHECK(Protect(reinterpret_cast<void *>(physical_start),
+                static_cast<int>(physical_end - physical_start), ACC_READONLY));
+
+  write_watches_.Insert(
+      physical_start, physical_end - 1,
+      WriteWatch(handler, ctx, data, physical_start, physical_end));
+
+  // track number of watches
+  PROFILER_COUNT("WriteWatches", write_watches_.Size());
+}
+
+bool SIGSEGVHandler::HandleAccessFault(uintptr_t rip, uintptr_t fault_addr) {
+  WatchTree::node_type *node = write_watches_.Find(fault_addr, fault_addr);
+
+  bool handled = node != nullptr;
+
+  while (node) {
+    WriteWatch &watch = node->value;
+
+    watch.handler(watch.ctx, watch.data);
+
+    // remove write protection
+    CHECK(Protect(reinterpret_cast<void *>(watch.physical_start),
+                  static_cast<int>(watch.physical_end - watch.physical_start),
+                  ACC_READWRITE));
+
+    write_watches_.Remove(node);
+
+    node = write_watches_.Find(fault_addr, fault_addr);
+  }
+
+  // track number of watches
+  PROFILER_COUNT("WriteWatches", write_watches_.Size());
+
+  return handled;
+}

src/sys/sigsegv_handler.h

@@ -0,0 +1,61 @@
+#ifndef SIGSEGV_HANDLER_H
+#define SIGSEGV_HANDLER_H
+
+#include <functional>
+#include <memory>
+#include "core/interval_tree.h"
+
+namespace dreavm {
+namespace sys {
+
+// implemented in the platform specific souce file
+class SIGSEGVHandler;
+extern SIGSEGVHandler *CreateSIGSEGVHandler();
+
+enum PageAccess { ACC_READONLY, ACC_READWRITE };
+
+typedef std::function<void(void *, void *)> WriteWatchHandler;
+
+struct WriteWatch {
+  WriteWatch(WriteWatchHandler handler, void *ctx, void *data,
+             uintptr_t physical_start, uintptr_t physical_end)
+      : handler(handler),
+        ctx(ctx),
+        data(data),
+        physical_start(physical_start),
+        physical_end(physical_end) {}
+
+  WriteWatchHandler handler;
+  void *ctx;
+  void *data;
+  uintptr_t physical_start;
+  uintptr_t physical_end;
+};
+
+typedef IntervalTree<WriteWatch> WatchTree;
+
+class SIGSEGVHandler {
+ public:
+  static SIGSEGVHandler *global_handler() { return global_handler_; }
+
+  static SIGSEGVHandler *Install();
+
+  virtual ~SIGSEGVHandler();
+
+  void AddWriteWatch(void *ptr, int size, WriteWatchHandler handler, void *ctx,
+                     void *data);
+  bool HandleAccessFault(uintptr_t rip, uintptr_t fault_addr);
+
+ protected:
+  static SIGSEGVHandler *global_handler_;
+
+  virtual bool Init() = 0;
+  virtual int GetPageSize() = 0;
+  virtual bool Protect(void *ptr, int size, PageAccess access) = 0;
+
+  WatchTree write_watches_;
+};
+}
+}
+
+#endif

src/sys/sigsegv_handler_linux.cc

@@ -0,0 +1,61 @@
+#include <sys/mman.h>
+#include <signal.h>
+#include <unistd.h>
+#include "core/core.h"
+#include "sys/sigsegv_handler_linux.h"
+
+using namespace dreavm::sys;
+
+SIGSEGVHandler *dreavm::sys::CreateSIGSEGVHandler() {
+  return new SIGSEGVHandlerLinux();
+}
+
+static struct sigaction old_sa;
+
+static void SignalHandler(int signo, siginfo_t *info, void *ctx) {
+  ucontext_t *uctx = reinterpret_cast<ucontext_t *>(ctx);
+
+  uintptr_t rip = uctx->uc_mcontext.gregs[REG_RIP];
+  uintptr_t fault_addr = reinterpret_cast<uintptr_t>(info->si_addr);
+  bool handled =
+      SIGSEGVHandler::global_handler()->HandleAccessFault(rip, fault_addr);
+
+  if (!handled) {
+    // call into the original handler if the installed handler fails to handle
+    // the signal
+    (*old_sa.sa_sigaction)(signo, info, ctx);
+  }
+}
+
+SIGSEGVHandlerLinux::~SIGSEGVHandlerLinux() {
+  sigaction(SIGSEGV, &old_sa, nullptr);
+}
+
+bool SIGSEGVHandlerLinux::Init() {
+  struct sigaction new_sa;
+  new_sa.sa_flags = SA_SIGINFO;
+  sigemptyset(&new_sa.sa_mask);
+  new_sa.sa_sigaction = &SignalHandler;
+
+  if (sigaction(SIGSEGV, &new_sa, &old_sa) != 0) {
+    return false;
+  }
+
+  return true;
+}
+
+int SIGSEGVHandlerLinux::GetPageSize() { return getpagesize(); }
+
+bool SIGSEGVHandlerLinux::Protect(void *ptr, int size, PageAccess access) {
+  int prot = PROT_NONE;
+  switch (access) {
+    case ACC_READONLY:
+      prot = PROT_READ;
+      break;
+    case ACC_READWRITE:
+      prot = PROT_READ | PROT_WRITE;
+      break;
+  }
+
+  return mprotect(ptr, size, prot) == 0;
+}

src/sys/sigsegv_handler_linux.h

@@ -0,0 +1,24 @@
+#ifndef SIGSEGV_HANDLER_LINUX
+#define SIGSEGV_HANDLER_LINUX
+
+#include <thread>
+#include "sys/sigsegv_handler.h"
+
+namespace dreavm {
+namespace sys {
+
+class SIGSEGVHandlerLinux : public SIGSEGVHandler {
+ public:
+  ~SIGSEGVHandlerLinux();
+
+ protected:
+  bool Init();
+  int GetPageSize();
+  bool Protect(void *ptr, int size, PageAccess access);
+
+ private:
+};
+}
+}
+
+#endif

src/sys/sigsegv_handler_mac.cc

@@ -0,0 +1,141 @@
+#include <mach/mach.h>
+#include <sys/mman.h>
+#include <unistd.h>
+#include "core/core.h"
+#include "sys/sigsegv_handler_mac.h"
+
+using namespace dreavm::sys;
+
+SIGSEGVHandler *dreavm::sys::CreateSIGSEGVHandler() {
+  return new SIGSEGVHandlerMac();
+}
+
+// http://web.mit.edu/darwin/src/modules/xnu/osfmk/man/exc_server.html
+extern "C" boolean_t exc_server(mach_msg_header_t *request_msg,
+                                mach_msg_header_t *reply_msg);
+
+// http://web.mit.edu/darwin/src/modules/xnu/osfmk/man/catch_exception_raise.html
+extern "C" kern_return_t catch_exception_raise(
+    mach_port_t exception_port, mach_port_t thread, mach_port_t task,
+    exception_type_t exception, exception_data_t code,
+    mach_msg_type_number_t code_count) {
+  // get exception state
+  mach_msg_type_number_t state_count = x86_EXCEPTION_STATE64_COUNT;
+  x86_exception_state64_t exc_state;
+  if (thread_get_state(thread, x86_EXCEPTION_STATE64,
+                       reinterpret_cast<thread_state_t>(&exc_state),
+                       &state_count) != KERN_SUCCESS) {
+    return KERN_FAILURE;
+  }
+
+  // get thread state
+  state_count = x86_THREAD_STATE64_COUNT;
+  x86_thread_state64_t thread_state;
+  if (thread_get_state(thread, x86_THREAD_STATE64,
+                       reinterpret_cast<thread_state_t>(&thread_state),
+                       &state_count) != KERN_SUCCESS) {
+    return KERN_FAILURE;
+  }
+
+  uintptr_t rip = thread_state.__rip;
+  uintptr_t fault_addr = exc_state.__faultvaddr;
+  bool handled =
+      SIGSEGVHandler::global_handler()->HandleAccessFault(rip, fault_addr);
+  if (!handled) {
+    return KERN_FAILURE;
+  }
+
+  // reset thread state
+  if (thread_set_state(thread, x86_THREAD_STATE64,
+                       reinterpret_cast<thread_state_t>(&thread_state),
+                       state_count) != KERN_SUCCESS) {
+    return KERN_FAILURE;
+  }
+
+  return KERN_SUCCESS;
+}
+
+SIGSEGVHandlerMac::~SIGSEGVHandlerMac() {
+  task_set_exception_ports(mach_task_self(), EXC_MASK_BAD_ACCESS, 0,
+                           EXCEPTION_DEFAULT, 0);
+  mach_port_deallocate(mach_task_self(), listen_port_);
+}
+
+bool SIGSEGVHandlerMac::Init() {
+  // allocate port to listen for exceptions
+  if (mach_port_allocate(mach_task_self(), MACH_PORT_RIGHT_RECEIVE,
+                         &listen_port_) != KERN_SUCCESS) {
+    return false;
+  }
+
+  // http://web.mit.edu/darwin/src/modules/xnu/osfmk/man/mach_port_insert_right.html
+  if (mach_port_insert_right(mach_task_self(), listen_port_, listen_port_,
+                             MACH_MSG_TYPE_MAKE_SEND) != KERN_SUCCESS) {
+    return false;
+  }
+
+  // filter out any exception other than EXC_BAD_ACCESS
+  // http://web.mit.edu/darwin/src/modules/xnu/osfmk/man/task_set_exception_ports.html
+  if (task_set_exception_ports(mach_task_self(), EXC_MASK_BAD_ACCESS,
+                               listen_port_, EXCEPTION_DEFAULT,
+                               MACHINE_THREAD_STATE) != KERN_SUCCESS) {
+    return false;
+  }
+
+  // launch thread to listen for exceptions
+  thread_ = std::thread([this] { ThreadEntry(); });
+  thread_.detach();
+
+  return true;
+}
+
+int SIGSEGVHandlerMac::GetPageSize() { return getpagesize(); }
+
+bool SIGSEGVHandlerMac::Protect(void *ptr, int size, PageAccess access) {
+  int prot = PROT_NONE;
+  switch (access) {
+    case ACC_READONLY:
+      prot = PROT_READ;
+      break;
+    case ACC_READWRITE:
+      prot = PROT_READ | PROT_WRITE;
+      break;
+  }
+
+  return mprotect(ptr, size, prot) == 0;
+}
+
+void SIGSEGVHandlerMac::ThreadEntry() {
+  while (true) {
+    struct {
+      mach_msg_header_t head;
+      mach_msg_body_t msgh_body;
+      char data[1024];
+    } msg;
+    struct {
+      mach_msg_header_t head;
+      char data[1024];
+    } reply;
+
+    // wait for a message on the exception port
+    mach_msg_return_t ret =
+        mach_msg(&msg.head, MACH_RCV_MSG | MACH_RCV_LARGE, 0, sizeof(msg),
+                 listen_port_, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
+    if (ret != MACH_MSG_SUCCESS) {
+      LOG_INFO("mach_msg receive failed with %d %s", ret,
+               mach_error_string(ret));
+      break;
+    }
+
+    // call exc_server, which will call back into catch_exception_raise
+    exc_server(&msg.head, &reply.head);
+
+    // send the reply
+    ret = mach_msg(&reply.head, MACH_SEND_MSG, reply.head.msgh_size, 0,
+                   MACH_PORT_NULL, MACH_MSG_TIMEOUT_NONE, MACH_PORT_NULL);
+    if (ret != MACH_MSG_SUCCESS) {
+      LOG_INFO("mach_msg send failed with %d %s", ret, mach_error_string(ret));
+      break;
+    }
+  }
+}

src/sys/sigsegv_handler_mac.h

@@ -0,0 +1,28 @@
+#ifndef SIGSEGV_HANDLER_MAC
+#define SIGSEGV_HANDLER_MAC
+
+#include <thread>
+#include "sys/sigsegv_handler.h"
+
+namespace dreavm {
+namespace sys {
+
+class SIGSEGVHandlerMac : public SIGSEGVHandler {
+ public:
+  ~SIGSEGVHandlerMac();
+
+ protected:
+  bool Init();
+  int GetPageSize();
+  bool Protect(void *ptr, int size, PageAccess access);
+
+ private:
+  void ThreadEntry();
+
+  mach_port_t listen_port_;
+  std::thread thread_;
+};
+}
+}
+
+#endif

src/sys/sigsegv_handler_win.cc

@@ -0,0 +1,56 @@
+#include <windows.h>
+#include "core/core.h"
+#include "sys/sigsegv_handler_win.h"
+
+using namespace dreavm::sys;
+
+SIGSEGVHandler *dreavm::sys::CreateSIGSEGVHandler() {
+  return new SIGSEGVHandlerWin();
+}
+
+static LONG CALLBACK ExceptionHandler(PEXCEPTION_POINTERS ex_info) {
+  auto code = ex_info->ExceptionRecord->ExceptionCode;
+  if (code != STATUS_ACCESS_VIOLATION) {
+    return EXCEPTION_CONTINUE_SEARCH;
+  }
+
+  uintptr_t rip = ex_info->ContextRecord->Rip;
+  uintptr_t fault_addr = ex_info->ExceptionRecord->ExceptionInformation[1];
+  bool handled =
+      SIGSEGVHandler::global_handler()->HandleAccessFault(rip, fault_addr);
+
+  if (!handled) {
+    return EXCEPTION_CONTINUE_SEARCH;
+  }
+
+  return EXCEPTION_CONTINUE_EXECUTION;
+}
+
+SIGSEGVHandlerWin::~SIGSEGVHandlerWin() {
+  RemoveVectoredExceptionHandler(ExceptionHandler);
+}
+
+bool SIGSEGVHandlerWin::Init() {
+  return AddVectoredExceptionHandler(1, ExceptionHandler) != nullptr;
+}
+
+int SIGSEGVHandlerWin::GetPageSize() {
+  SYSTEM_INFO system_info;
+  GetSystemInfo(&system_info);
+  return system_info.dwPageSize;
+}
+
+bool SIGSEGVHandlerWin::Protect(void *ptr, int size, PageAccess access) {
+  DWORD new_protect = PAGE_NOACCESS;
+  DWORD old_protect;
+  switch (access) {
+    case ACC_READONLY:
+      new_protect = PAGE_READONLY;
+      break;
+    case ACC_READWRITE:
+      new_protect = PAGE_READWRITE;
+      break;
+  }
+
+  return VirtualProtect(ptr, size, new_protect, &old_protect);
+}

src/sys/sigsegv_handler_win.h

@@ -0,0 +1,24 @@
+#ifndef SIGSEGV_HANDLER_WIN
+#define SIGSEGV_HANDLER_WIN
+
+#include <thread>
+#include "sys/sigsegv_handler.h"
+
+namespace dreavm {
+namespace sys {
+
+class SIGSEGVHandlerWin : public SIGSEGVHandler {
+ public:
+  ~SIGSEGVHandlerWin();
+
+ protected:
+  bool Init();
+  int GetPageSize();
+  bool Protect(void *ptr, int size, PageAccess access);
+
+ private:
+};
+}
+}
+
+#endif