From 8b4e129fc167f2a666ecd73b2bea3374ece2f849 Mon Sep 17 00:00:00 2001
From: Bananymous <oskari.alaranta@bananymous.com>
Date: Sat, 4 Nov 2023 18:13:16 +0200
Subject: [PATCH] Kernel: Add better APIs for fast page

---
 kernel/include/kernel/Memory/PageTable.h | 25 ++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/kernel/include/kernel/Memory/PageTable.h b/kernel/include/kernel/Memory/PageTable.h
index 705853bac1..96c527a927 100644
--- a/kernel/include/kernel/Memory/PageTable.h
+++ b/kernel/include/kernel/Memory/PageTable.h
@@ -1,12 +1,20 @@
 #pragma once
 
 #include <BAN/Errors.h>
+#include <BAN/Traits.h>
+#include <kernel/CriticalScope.h>
 #include <kernel/Memory/Types.h>
 #include <kernel/SpinLock.h>
 
 namespace Kernel
 {
 
+	template<typename F>
+	concept with_fast_page_callback = requires(F func)
+	{
+		requires BAN::is_same_v<decltype(func()), void>;
+	};
+
 	class PageTable
 	{
 	public:
@@ -33,6 +41,15 @@ namespace Kernel
 		static void unmap_fast_page();
 		static constexpr vaddr_t fast_page() { return KERNEL_OFFSET; }
 
+		template<with_fast_page_callback F>
+		static void with_fast_page(paddr_t paddr, F callback)
+		{
+			CriticalScope _;
+			map_fast_page(paddr);
+			callback();
+			unmap_fast_page();
+		}
+
 		// FIXME: implement sized checks, return span, etc
 		static void* fast_page_as_ptr(size_t offset = 0)
 		{
@@ -47,6 +64,14 @@ namespace Kernel
 			return *reinterpret_cast<T*>(fast_page() + offset);
 		}
 
+		// Retrieves index'th element from fast_page
+		template<typename T>
+		static T& fast_page_as_sized(size_t index)
+		{
+			ASSERT((index + 1) * sizeof(T) <= PAGE_SIZE);
+			return *reinterpret_cast<T*>(fast_page() + index * sizeof(T));
+		}
+
 		static bool is_valid_pointer(uintptr_t);
 
 		static BAN::ErrorOr<PageTable*> create_userspace();