Kernel: Basic support for IPC translation for HLE services

src/core/hle/kernel/hle_ipc.cpp

@@ -8,6 +8,7 @@
 #include "core/hle/kernel/handle_table.h"
 #include "core/hle/kernel/hle_ipc.h"
 #include "core/hle/kernel/kernel.h"
+#include "core/hle/kernel/process.h"
 #include "core/hle/kernel/server_session.h"
 
 namespace Kernel {
@@ -24,12 +25,97 @@ void SessionRequestHandler::ClientDisconnected(SharedPtr<ServerSession> server_s
 
 HLERequestContext::~HLERequestContext() = default;
 
-SharedPtr<Object> HLERequestContext::GetIncomingHandle(Handle id_from_cmdbuf) const {
-    return Kernel::g_handle_table.GetGeneric(id_from_cmdbuf);
+SharedPtr<Object> HLERequestContext::GetIncomingHandle(u32 id_from_cmdbuf) const {
+    ASSERT(id_from_cmdbuf < request_handles.size());
+    return request_handles[id_from_cmdbuf];
 }
 
-Handle HLERequestContext::AddOutgoingHandle(SharedPtr<Object> object) {
-    return Kernel::g_handle_table.Create(object).Unwrap();
+u32 HLERequestContext::AddOutgoingHandle(SharedPtr<Object> object) {
+    request_handles.push_back(std::move(object));
+    return request_handles.size() - 1;
+}
+
+ResultCode HLERequestContext::PopulateFromIncomingCommandBuffer(const u32_le* src_cmdbuf,
+                                                                Process& src_process,
+                                                                HandleTable& src_table) {
+    IPC::Header header{src_cmdbuf[0]};
+
+    size_t untranslated_size = 1u + header.normal_params_size;
+    size_t command_size = untranslated_size + header.translate_params_size;
+    ASSERT(command_size <= IPC::COMMAND_BUFFER_LENGTH); // TODO(yuriks): Return error
+
+    std::copy_n(src_cmdbuf, untranslated_size, cmd_buf.begin());
+
+    size_t i = untranslated_size;
+    while (i < command_size) {
+        u32 descriptor = cmd_buf[i] = src_cmdbuf[i];
+        i += 1;
+
+        switch (IPC::GetDescriptorType(descriptor)) {
+        case IPC::DescriptorType::CopyHandle:
+        case IPC::DescriptorType::MoveHandle: {
+            u32 num_handles = IPC::HandleNumberFromDesc(descriptor);
+            ASSERT(i + num_handles <= command_size); // TODO(yuriks): Return error
+            for (u32 j = 0; j < num_handles; ++j) {
+                Handle handle = src_cmdbuf[i];
+                SharedPtr<Object> object = src_table.GetGeneric(handle);
+                ASSERT(object != nullptr); // TODO(yuriks): Return error
+                if (descriptor == IPC::DescriptorType::MoveHandle) {
+                    src_table.Close(handle);
+                }
+
+                cmd_buf[i++] = AddOutgoingHandle(std::move(object));
+            }
+            break;
+        }
+        case IPC::DescriptorType::CallingPid: {
+            cmd_buf[i++] = src_process.process_id;
+            break;
+        }
+        default:
+            UNIMPLEMENTED_MSG("Unsupported handle translation: 0x%08X", descriptor);
+        }
+    }
+
+    return RESULT_SUCCESS;
+}
+
+ResultCode HLERequestContext::WriteToOutgoingCommandBuffer(u32_le* dst_cmdbuf, Process& dst_process,
+                                                           HandleTable& dst_table) const {
+    IPC::Header header{cmd_buf[0]};
+
+    size_t untranslated_size = 1u + header.normal_params_size;
+    size_t command_size = untranslated_size + header.translate_params_size;
+    ASSERT(command_size <= IPC::COMMAND_BUFFER_LENGTH);
+
+    std::copy_n(cmd_buf.begin(), untranslated_size, dst_cmdbuf);
+
+    size_t i = untranslated_size;
+    while (i < command_size) {
+        u32 descriptor = dst_cmdbuf[i] = cmd_buf[i];
+        i += 1;
+
+        switch (IPC::GetDescriptorType(descriptor)) {
+        case IPC::DescriptorType::CopyHandle:
+        case IPC::DescriptorType::MoveHandle: {
+            // HLE services don't use handles, so we treat both CopyHandle and MoveHandle equally
+            u32 num_handles = IPC::HandleNumberFromDesc(descriptor);
+            ASSERT(i + num_handles <= command_size);
+            for (u32 j = 0; j < num_handles; ++j) {
+                SharedPtr<Object> object = GetIncomingHandle(cmd_buf[i]);
+
+                // TODO(yuriks): Figure out the proper error handling for if this fails
+                Handle handle = dst_table.Create(object).Unwrap();
+                dst_cmdbuf[i++] = handle;
+            }
+            break;
+        }
+        default:
+            UNIMPLEMENTED_MSG("Unsupported handle translation: 0x%08X", descriptor);
+        }
+    }
+
+    return RESULT_SUCCESS;
 }
 
 } // namespace Kernel

src/core/hle/kernel/hle_ipc.h

@@ -8,6 +8,7 @@
 #include <memory>
 #include <vector>
 #include "common/common_types.h"
+#include "common/swap.h"
 #include "core/hle/ipc.h"
 #include "core/hle/kernel/kernel.h"
 #include "core/hle/kernel/server_session.h"
@@ -18,6 +19,9 @@ class ServiceFrameworkBase;
 
 namespace Kernel {
 
+class HandleTable;
+class Process;
+
 /**
  * Interface implemented by HLE Session handlers.
  * This can be provided to a ServerSession in order to hook into several relevant events
@@ -62,6 +66,20 @@ protected:
  * Class containing information about an in-flight IPC request being handled by an HLE service
  * implementation. Services should avoid using old global APIs (e.g. Kernel::GetCommandBuffer()) and
  * when possible use the APIs in this class to service the request.
+ *
+ * HLE handle protocol
+ * ===================
+ *
+ * To avoid needing HLE services to keep a separate handle table, or having to directly modify the
+ * requester's table, a tweaked protocol is used to receive and send handles in requests. The kernel
+ * will decode the incoming handles into object pointers and insert a id in the buffer where the
+ * handle would normally be. The service then calls GetIncomingHandle() with that id to get the
+ * pointer to the object. Similarly, instead of inserting a handle into the command buffer, the
+ * service calls AddOutgoingHandle() and stores the returned id where the handle would normally go.
+ *
+ * The end result is similar to just giving services their own real handle tables, but since these
+ * ids are local to a specific context, it avoids requiring services to manage handles for objects
+ * across multiple calls and ensuring that unneeded handles are cleaned up.
  */
 class HLERequestContext {
 public:
@@ -80,14 +98,29 @@ public:
         return session;
     }
 
-    SharedPtr<Object> GetIncomingHandle(Handle id_from_cmdbuf) const;
-    Handle AddOutgoingHandle(SharedPtr<Object> object);
+    /**
+     * Resolves a object id from the request command buffer into a pointer to an object. See the
+     * "HLE handle protocol" section in the class documentation for more details.
+     */
+    SharedPtr<Object> GetIncomingHandle(u32 id_from_cmdbuf) const;
+
+    /**
+     * Adds an outgoing object to the response, returning the id which should be used to reference
+     * it. See the "HLE handle protocol" section in the class documentation for more details.
+     */
+    u32 AddOutgoingHandle(SharedPtr<Object> object);
 
 private:
     friend class Service::ServiceFrameworkBase;
 
+    ResultCode PopulateFromIncomingCommandBuffer(const u32_le* src_cmdbuf, Process& src_process,
+                                                 HandleTable& src_table);
+    ResultCode WriteToOutgoingCommandBuffer(u32_le* dst_cmdbuf, Process& dst_process,
+                                            HandleTable& dst_table) const;
+
     std::array<u32, IPC::COMMAND_BUFFER_LENGTH> cmd_buf;
     SharedPtr<ServerSession> session;
+    std::vector<SharedPtr<Object>> request_handles;
 };
 
 } // namespace Kernel