Add a VMO pointer to VNode.

This way, if anyone tries to map an already mapped file, we share the VMO.

AK/Function.h

@@ -87,7 +87,7 @@ class Function<Out(In...)> {
  };
 
  template<typename CallableType>
- class CallableWrapper : public CallableWrapperBase {
+ class CallableWrapper final : public CallableWrapperBase {
  public:
  explicit CallableWrapper(CallableType&& callable)
  : m_callable(move(callable))

AK/StdLib.h

@@ -28,9 +28,10 @@ inline T max(const T& a, const T& b)
 }
 
 
-template<typename T>
-static inline T ceilDiv(T a, T b)
+template<typename T, typename U>
+static inline T ceilDiv(T a, U b)
 {
+ static_assert(sizeof(T) == sizeof(U));
  T result = a / b;
  if ((a % b) != 0)
  ++result;

Kernel/MemoryManager.cpp

@@ -220,8 +220,7 @@ Region* MemoryManager::region_from_laddr(Process& process, LinearAddress laddr)
  return region.ptr();
  }
  kprintf("%s(%u) Couldn't find region for L%x\n", process.name().characters(), process.pid(), laddr.get());
- process.dumpRegions();
- ASSERT_NOT_REACHED();
+ return nullptr;
 }
 
 bool MemoryManager::copy_on_write(Process& process, Region& region, unsigned page_index_in_region)
@@ -292,7 +291,10 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
  dbgprintf("MM: handle_page_fault(%w) at L%x\n", fault.code(), fault.laddr().get());
 #endif
  auto* region = region_from_laddr(*current, fault.laddr());
- ASSERT(region);
+ if (!region) {
+ kprintf("NP(error) fault at invalid address L%x\n", fault.laddr().get());
+ return PageFaultResponse::ShouldCrash;
+ }
  auto page_index_in_region = region->page_index_from_address(fault.laddr());
  if (fault.is_not_present()) {
  if (region->vmo().vnode()) {
@@ -640,7 +642,12 @@ void PhysicalPage::return_to_freelist()
 
 RetainPtr<VMObject> VMObject::create_file_backed(RetainPtr<VirtualFileSystem::Node>&& vnode, size_t size)
 {
- return adopt(*new VMObject(move(vnode), size));
+ InterruptDisabler disabler;
+ if (vnode->vmo())
+ return static_cast<VMObject*>(vnode->vmo());
+ auto vmo = adopt(*new VMObject(move(vnode), size));
+ vmo->vnode()->set_vmo(vmo.ptr());
+ return vmo;
 }
 
 RetainPtr<VMObject> VMObject::create_anonymous(size_t size)
@@ -679,6 +686,11 @@ VMObject::VMObject(RetainPtr<VirtualFileSystem::Node>&& vnode, size_t size)
 
 VMObject::~VMObject()
 {
+ InterruptDisabler disabler;
+ if (m_vnode) {
+ ASSERT(m_vnode->vmo() == this);
+ m_vnode->set_vmo(nullptr);
+ }
 }
 
 int Region::commit(Process& process)

Kernel/ProcFileSystem.cpp

@@ -49,7 +49,7 @@ ByteBuffer procfs$pid_vm(Process& process)
 {
  ProcessInspectionScope scope(process);
  char* buffer;
- auto stringImpl = StringImpl::createUninitialized(80 + process.regionCount() * 80 + 4096, buffer);
+ auto stringImpl = StringImpl::createUninitialized(80 + process.regionCount() * 160 + 4096, buffer);
  memset(buffer, 0, stringImpl->length());
  char* ptr = buffer;
  ptr += ksprintf(ptr, "BEGIN END SIZE NAME\n");
@@ -59,12 +59,17 @@ ByteBuffer procfs$pid_vm(Process& process)
  region->linearAddress.offset(region->size - 1).get(),
  region->size,
  region->name.characters());
+ ptr += ksprintf(ptr, "VMO: %s \"%s\" @ %x(%u)\n",
+ region->vmo().is_anonymous() ? "anonymous" : "file-backed",
+ region->vmo().name().characters(),
+ &region->vmo(),
+ region->vmo().retainCount());
  for (size_t i = 0; i < region->vmo().page_count(); ++i) {
  auto& physical_page = region->vmo().physical_pages()[i];
  ptr += ksprintf(ptr, "P%x%s(%u) ",
  physical_page ? physical_page->paddr().get() : 0,
  region->cow_map.get(i) ? "!" : "",
- physical_page->retain_count()
+ physical_page ? physical_page->retain_count() : 0
  );
  }
  ptr += ksprintf(ptr, "\n");

Kernel/init.cpp

@@ -296,7 +296,6 @@ void init()
  procfs->initialize();
 
  Process::initialize();
-
  Process::create_kernel_process(init_stage2, "init_stage2");
 
  Scheduler::pick_next();

Userland/sh.cpp

@@ -139,6 +139,27 @@ static int sh_mf(int, const char**)
  return 0;
 }
 
+static int sh_mp(int, const char**)
+{
+ int rc;
+ int fd = open("/kernel.map", O_RDONLY);
+ if (fd < 0) {
+ perror("open(/kernel.map)");
+ return 1;
+ }
+ printf("opened /kernel.map, calling mmap...\n");
+ byte* data = (byte*)mmap(nullptr, getpagesize() * 10, PROT_READ, MAP_PRIVATE, fd, 0);
+ if (data == MAP_FAILED) {
+ perror("mmap()");
+ return 1;
+ }
+ printf("mapped file @ %p\n", data);
+ printf("contents: %c%c%c%c%c%c%c...\n", data[0], data[1], data[2], data[3], data[4], data[5], data[6], data[7]);
+
+ printf("leaving it open :)\n");
+ return 0;
+}
+
 static int sh_exit(int, const char**)
 {
  printf("Good-bye!\n");
@@ -221,6 +242,10 @@ static bool handle_builtin(int argc, const char** argv, int& retval)
  retval = sh_mf(argc, argv);
  return true;
  }
+ if (!strcmp(argv[0], "mp")) {
+ retval = sh_mp(argc, argv);
+ return true;
+ }
  if (!strcmp(argv[0], "fork")) {
  retval = sh_fork(argc, argv);
  return true;

VirtualFileSystem/VirtualFileSystem.cpp

@@ -180,6 +180,7 @@ auto VirtualFileSystem::allocateNode() -> RetainPtr<Node>
  ASSERT(node->retainCount == 0);
  node->retainCount = 1;
  node->m_vfs = this;
+ node->m_vmo = nullptr;
  return adopt(*node);
 }
 
@@ -197,6 +198,8 @@ void VirtualFileSystem::freeNode(Node* node)
  m_device2vnode.remove(encodedDevice(node->m_characterDevice->major(), node->m_characterDevice->minor()));
  node->m_characterDevice = nullptr;
  }
+ node->m_vfs = nullptr;
+ node->m_vmo = nullptr;
  m_nodeFreeList.append(move(node));
 }
 

VirtualFileSystem/VirtualFileSystem.h

@@ -65,12 +65,16 @@ class VirtualFileSystem {
  VirtualFileSystem* vfs() { return m_vfs; }
  const VirtualFileSystem* vfs() const { return m_vfs; }
 
+ void* vmo() { return m_vmo; }
+ void set_vmo(void* vmo) { m_vmo = vmo; }
+
  private:
  friend class VirtualFileSystem;
  VirtualFileSystem* m_vfs { nullptr };
  unsigned retainCount { 0 };
  CharacterDevice* m_characterDevice { nullptr };
  mutable InodeMetadata m_cachedMetadata;
+ void* m_vmo { nullptr };
  };
 
  static VirtualFileSystem& the() PURE;