[zion] Add a direct port write for the kernel

zion/loader/init_loader.cpp

@@ -130,25 +130,11 @@ void LoadInitProgram() {
   prog2_vmmo->CopyBytesToObject(reinterpret_cast<uint64_t>(prog2.address),
                                 prog2.size);
 
-  // TODO: Probably add a way for the kernel to write caps directly rather than
-  // by installing them first.
-  uint64_t vmmo_cap =
-      gScheduler->CurrentProcess().AddNewCapability(prog2_vmmo, ZC_WRITE);
-
   auto port = MakeRefCounted<Port>();
   uint64_t port_cap = proc->AddNewCapability(port, ZC_READ | ZC_WRITE);
 
-  uint64_t vmmo_id = Z_BOOT_DENALI_VMMO;
-  ZMessage vmmo_msg{
-      .type = 0,
-      .num_bytes = 8,
-      .bytes = reinterpret_cast<uint8_t*>(&vmmo_id),
-      .num_caps = 1,
-      .caps = &vmmo_cap,
-  };
-  if (port->Write(vmmo_msg) != Z_OK) {
-    panic("Failed to write cap");
-  }
+  port->WriteKernel(Z_BOOT_DENALI_VMMO,
+                    MakeRefCounted<Capability>(prog2_vmmo, ZC_READ | ZC_WRITE));
 
   proc->CreateThread()->Start(entry, port_cap, 0);
 }

zion/object/port.cpp

@@ -74,6 +74,23 @@ z_err_t Port::Read(ZMessage& msg) {
   return Z_OK;
 }
 
+void Port::WriteKernel(uint64_t init, RefPtr<Capability> cap) {
+  MutexHolder h(mutex_);
+
+  auto msg = MakeShared<Message>();
+  msg->type = 0;
+  msg->bytes = new uint8_t[8];
+  msg->num_bytes = sizeof(init);
+
+  uint8_t* data = reinterpret_cast<uint8_t*>(&init);
+  for (uint8_t i = 0; i < sizeof(init); i++) {
+    msg->bytes[i] = data[i];
+  }
+  msg->caps.PushBack(cap);
+
+  pending_messages_.PushBack(msg);
+}
+
 bool Port::HasMessages() {
   MutexHolder h(mutex_);
   return pending_messages_.size() != 0;

zion/object/port.h

@@ -24,6 +24,8 @@ class Port : public KernelObject {
   z_err_t Write(const ZMessage& msg);
   z_err_t Read(ZMessage& msg);
 
+  void WriteKernel(uint64_t init, RefPtr<Capability> cap);
+
   bool HasMessages();
 
  private: