[mammoth] Return ErrorOr when creating a process

lib/glacier/container/pair.h

@@ -1,5 +1,7 @@
 #pragma once
 
+namespace glcr {
+
 template <typename T, typename U>
 class Pair {
  public:
@@ -11,3 +13,5 @@ class Pair {
   T first_;
   U second_;
 };
+
+}  // namespace glcr

lib/glacier/status/error_or.h

@@ -10,6 +10,8 @@ class ErrorOr {
   ErrorOr() = delete;
   ErrorOr(const ErrorOr&) = delete;
   ErrorOr(ErrorOr&&) = delete;
+  // FIXME: Do we have to call ~T manually here.
+  ~ErrorOr() {}
 
   ErrorOr(ErrorCode code) : error_(code), ok_(false) {}
   ErrorOr(const T& obj) : obj_(obj), ok_(true) {}

lib/mammoth/include/mammoth/process.h

@@ -1,7 +1,8 @@
 #pragma once
 
+#include <glacier/status/error_or.h>
 #include <stdint.h>
 
 #include "mammoth/channel.h"
 
-uint64_t SpawnProcessFromElfRegion(uint64_t program, Channel& local);
+glcr::ErrorOr<Channel> SpawnProcessFromElfRegion(uint64_t program);

lib/mammoth/src/process.cpp

@@ -95,8 +95,8 @@ uint64_t LoadElfProgram(uint64_t base, uint64_t as_cap) {
 
 }  // namespace
 
-uint64_t SpawnProcessFromElfRegion(uint64_t program, Channel& local) {
-  Channel foreign;
+glcr::ErrorOr<Channel> SpawnProcessFromElfRegion(uint64_t program) {
+  Channel local, foreign;
   check(CreateChannels(local, foreign));
 
   uint64_t proc_cap;
@@ -134,5 +134,5 @@ uint64_t SpawnProcessFromElfRegion(uint64_t program, Channel& local) {
 #endif
   check(ZThreadStart(thread_cap, entry_point, foreign_port_id, 0));
 
-  return glcr::OK;
+  return local;
 }

sys/yellowstone/yellowstone.cpp

@@ -17,8 +17,11 @@ uint64_t main(uint64_t port_cap) {
   uint64_t vaddr;
   check(ZAddressSpaceMap(gSelfVmasCap, 0, gBootDenaliVmmoCap, &vaddr));
 
-  Channel local;
-  check(SpawnProcessFromElfRegion(vaddr, local));
+  auto local_or = SpawnProcessFromElfRegion(vaddr);
+  if (!local_or) {
+    check(local_or.error());
+  }
+  Channel local = local_or.value();
 
   DenaliClient client(local);
   GptReader reader(client);

zion/object/channel.cpp

@@ -3,7 +3,7 @@
 #include "include/ztypes.h"
 #include "scheduler/scheduler.h"
 
-Pair<glcr::RefPtr<Channel>, glcr::RefPtr<Channel>>
+glcr::Pair<glcr::RefPtr<Channel>, glcr::RefPtr<Channel>>
 Channel::CreateChannelPair() {
   auto c1 = glcr::MakeRefCounted<Channel>();
   auto c2 = glcr::MakeRefCounted<Channel>();

zion/object/channel.h

@@ -1,13 +1,13 @@
 #pragma once
 
 #include <glacier/container/intrusive_list.h>
+#include <glacier/container/pair.h>
 #include <glacier/memory/ref_ptr.h>
 
 #include "capability/capability.h"
 #include "include/ztypes.h"
 #include "lib/message_queue.h"
 #include "lib/mutex.h"
-#include "lib/pair.h"
 #include "object/kernel_object.h"
 #include "usr/zcall_internal.h"
 
@@ -21,7 +21,8 @@ struct KernelObjectTag<Channel> {
 class Channel : public KernelObject {
  public:
   uint64_t TypeTag() override { return KernelObject::CHANNEL; }
-  static Pair<glcr::RefPtr<Channel>, glcr::RefPtr<Channel>> CreateChannelPair();
+  static glcr::Pair<glcr::RefPtr<Channel>, glcr::RefPtr<Channel>>
+  CreateChannelPair();
 
   glcr::RefPtr<Channel> peer() { return peer_; }