From 11eef8d892a3e4db81c87bbf6ef58291ce919ef4 Mon Sep 17 00:00:00 2001
From: "Justin C. Miller" <justin@devjustinian.com>
Date: Sat, 15 Jan 2022 09:37:55 -0800
Subject: [PATCH] [kernel] Add process_give_handle syscall

This syscall allows a process to give another process access to an
object it has a handle to. The value of the handle as seen in the
receiver process is returned to the caller, so that the caller may
notify the recipient which handle was given.
---
 definitions/objects/process.def |  7 +++++++
 src/kernel/syscalls/process.cpp | 14 ++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/definitions/objects/process.def b/definitions/objects/process.def
index 8da379b..6113c45 100644
--- a/definitions/objects/process.def
+++ b/definitions/objects/process.def
@@ -24,4 +24,11 @@ object process : kobject {
         param entrypoint address            # The address of the main thread entrypoint
         param handles object kobject [list] # A list of parent handles to send to the child process
     }
+
+    # Give the given process a handle that points to the same
+    # object as the specified handle.
+    method give_handle {
+        param sender object kobject          # A handle in the caller process to send
+        param receiver object kobject [out]  # The handle as the recipient will see it
+    }
 }
diff --git a/src/kernel/syscalls/process.cpp b/src/kernel/syscalls/process.cpp
index bdc2437..d046e50 100644
--- a/src/kernel/syscalls/process.cpp
+++ b/src/kernel/syscalls/process.cpp
@@ -56,4 +56,18 @@ process_exit(int32_t status)
     return j6_err_unexpected;
 }
 
+j6_status_t
+process_give_handle(j6_handle_t handle, j6_handle_t sender, j6_handle_t *receiver)
+{
+    process *dest = get_handle<process>(handle);
+    if (!dest) return j6_err_invalid_arg;
+
+    kobject *o = get_handle<kobject>(sender);
+    j6_handle_t out = dest->add_handle(o);
+
+    if (receiver)
+        *receiver = out;
+    return j6_status_ok;
+}
+
 } // namespace syscalls