[Mammoth] Add an owned memory capability that cleans itself up.

lib/mammoth/include/mammoth/memory_region.h

@@ -32,3 +32,40 @@ class MappedMemoryRegion {
   uint64_t vaddr_ = 0;
   uint64_t size_ = 0;
 };
+
+/*
+ * Memory Region class that unmaps its memory and releases its
+ * capability when it goes out of scope.
+ */
+class OwnedMemoryRegion {
+ public:
+  OwnedMemoryRegion() = default;
+
+  OwnedMemoryRegion(const OwnedMemoryRegion&) = delete;
+  OwnedMemoryRegion& operator=(const OwnedMemoryRegion&) = delete;
+
+  OwnedMemoryRegion(OwnedMemoryRegion&&);
+  OwnedMemoryRegion& operator=(OwnedMemoryRegion&&);
+
+  ~OwnedMemoryRegion();
+
+  static OwnedMemoryRegion FromCapability(z_cap_t vmmo_cap);
+
+  uint64_t paddr() { return paddr_; }
+  uint64_t vaddr() { return vaddr_; }
+  uint64_t size() { return size_; }
+
+  uint64_t cap() { return vmmo_cap_; }
+
+  bool empty() { return vmmo_cap_ != 0; }
+  explicit operator bool() { return vmmo_cap_ != 0; }
+
+ private:
+  OwnedMemoryRegion(uint64_t vmmo_cap, uint64_t paddr, uint64_t vaddr,
+                    uint64_t size)
+      : vmmo_cap_(vmmo_cap), paddr_(paddr), vaddr_(vaddr), size_(size) {}
+  uint64_t vmmo_cap_ = 0;
+  uint64_t paddr_ = 0;
+  uint64_t vaddr_ = 0;
+  uint64_t size_ = 0;
+};

lib/mammoth/src/memory_region.cpp

@@ -43,3 +43,41 @@ MappedMemoryRegion MappedMemoryRegion::FromCapability(z_cap_t vmmo_cap) {
   // FIXME: get the size here.
   return MappedMemoryRegion(vmmo_cap, 0, vaddr, 0);
 }
+
+OwnedMemoryRegion::OwnedMemoryRegion(OwnedMemoryRegion&& other)
+    : OwnedMemoryRegion(other.vmmo_cap_, other.paddr_, other.vaddr_,
+                        other.size_) {
+  other.vmmo_cap_ = 0;
+  other.paddr_ = 0;
+  other.vaddr_ = 0;
+  other.size_ = 0;
+}
+
+OwnedMemoryRegion& OwnedMemoryRegion::operator=(OwnedMemoryRegion&& other) {
+  if (vmmo_cap_) {
+    check(ZCapRelease(vmmo_cap_));
+  }
+  vmmo_cap_ = other.vmmo_cap_;
+  paddr_ = other.paddr_;
+  vaddr_ = other.vaddr_;
+  size_ = other.size_;
+  other.vmmo_cap_ = 0;
+  other.paddr_ = 0;
+  other.vaddr_ = 0;
+  other.size_ = 0;
+  return *this;
+}
+
+OwnedMemoryRegion::~OwnedMemoryRegion() {
+  if (vmmo_cap_ != 0) {
+    check(ZCapRelease(vmmo_cap_));
+  }
+}
+
+OwnedMemoryRegion OwnedMemoryRegion::FromCapability(z_cap_t vmmo_cap) {
+  uint64_t vaddr;
+  check(ZAddressSpaceMap(gSelfVmasCap, 0, vmmo_cap, &vaddr));
+
+  // FIXME: get the size here.
+  return OwnedMemoryRegion(vmmo_cap, 0, vaddr, 0);
+}