From 6e9b4491a6846703a113be1660fa98acfd09ee80 Mon Sep 17 00:00:00 2001
From: apio <blobs.trading@gmail.com>
Date: Sat, 7 Jan 2023 00:17:16 +0100
Subject: [PATCH] MemoryManager: Add copy_to_user() and copy_to_user_typed()

---
 kernel/src/memory/MemoryManager.cpp | 29 +++++++++++++++++++++++++++++
 kernel/src/memory/MemoryManager.h   |  7 +++++++
 2 files changed, 36 insertions(+)

diff --git a/kernel/src/memory/MemoryManager.cpp b/kernel/src/memory/MemoryManager.cpp
index 9a834af2..5c73c96a 100644
--- a/kernel/src/memory/MemoryManager.cpp
+++ b/kernel/src/memory/MemoryManager.cpp
@@ -364,6 +364,35 @@ namespace MemoryManager
         return true;
     }
 
+    bool copy_to_user(void* user, const void* kernel, usize size)
+    {
+        uintptr_t user_ptr = (uintptr_t)user;
+        uintptr_t user_page = align_down<ARCH_PAGE_SIZE>(user_ptr);
+
+        const char* kernel_ptr = (const char*)kernel;
+
+        // Userspace pointer not aligned on page boundary
+        if (user_ptr != user_page)
+        {
+            // FIXME: Validate that this page is writable by the user, not just the kernel.
+            if (!validate_writable_page(user_page)) return false;
+        }
+
+        while (size--)
+        {
+            // Crossed a page boundary, gotta check the page tables again before touching any memory!!
+            if (user_ptr % ARCH_PAGE_SIZE)
+            {
+                if (!validate_writable_page(user_ptr)) return false;
+            }
+
+            *(char*)user_ptr = *kernel_ptr++;
+            user_ptr++;
+        }
+
+        return true;
+    }
+
     usize free()
     {
         return free_mem;
diff --git a/kernel/src/memory/MemoryManager.h b/kernel/src/memory/MemoryManager.h
index b2f72a84..6ce8d001 100644
--- a/kernel/src/memory/MemoryManager.h
+++ b/kernel/src/memory/MemoryManager.h
@@ -22,6 +22,13 @@ namespace MemoryManager
 
     bool validate_userspace_string(u64 address);
 
+    bool copy_to_user(void* user, const void* kernel, usize size);
+
+    template <typename T> bool copy_to_user_typed(T* user, const T* kernel)
+    {
+        return copy_to_user(user, kernel, sizeof(T));
+    }
+
     Result<void> map_frames_at(u64 virt, u64 phys, usize count, int flags);
 
     Result<u64> alloc_at(u64 virt, usize count, int flags);