From 6ef0e69a585e08375e792bad544c35651344b385 Mon Sep 17 00:00:00 2001
From: Amelia Coutard <eliottulio.coutard@gmail.com>
Date: Sun, 12 Jun 2022 01:17:49 +0200
Subject: [PATCH] Moved the page allocator to be a global in paging.cpp and
 paging.hpp

---
 src/kernel.cpp | 12 ++++--------
 src/paging.cpp | 43 +++++++++++++++++++++++--------------------
 src/paging.hpp | 14 ++++++++++----
 3 files changed, 37 insertions(+), 32 deletions(-)

diff --git a/src/kernel.cpp b/src/kernel.cpp
index 7e1ab93..1cfa10e 100644
--- a/src/kernel.cpp
+++ b/src/kernel.cpp
@@ -28,10 +28,6 @@ void remove_some_mem(os::phys_ptr<os::paging::page> mem_start,
 	}
 }
 
-os::paging::page one_past_end_page_for_page_allocator;
-os::paging::page_allocator page_allocator(os::phys_ptr<os::paging::page>(reinterpret_cast<uintptr_t>(&one_past_end_page_for_page_allocator) - 0xFFFFFFFF80000000));
-
-
 os::idt<32> idt;
 extern "C" void handler_impl_code(std::uint32_t err_code) {
 	os::println("Interrupt !");
@@ -84,7 +80,7 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
 							remove_some_mem(
 							s, e, info_start, info_end,
 							[] (auto s, auto e) {
-								page_allocator.deallocate({.ptr = s, .size = std::uint64_t(e - s)});
+								os::paging::page_allocator.deallocate({.ptr = s, .size = std::uint64_t(e - s)});
 							}
 							);
 						}
@@ -107,14 +103,14 @@ extern "C" void kmain(unsigned long magic, os::phys_ptr<const multiboot2::info_s
 
 	// Deallocate multiboot info structure: not usable anymore.
 	if (info_pages_wholly_usable) {
-		page_allocator.deallocate({.ptr = info_start, .size = std::uint64_t(info_end - info_start)});
+		os::paging::page_allocator.deallocate({.ptr = info_start, .size = std::uint64_t(info_end - info_start)});
 	} else if (info_start + 1 < info_end - 1) {
 		// Ignore the first and last blocks: ensures all the RAM is truly usable.
-		page_allocator.deallocate({.ptr = info_start + 1, .size = std::uint64_t(info_end - info_start - 2)});
+		os::paging::page_allocator.deallocate({.ptr = info_start + 1, .size = std::uint64_t(info_end - info_start - 2)});
 	}
 
 	os::print("RAM:\n");
-	page_allocator.print_all();
+	os::paging::page_allocator.print_all();
 
 	{
 		os::isr_info isr_info[32];
diff --git a/src/paging.cpp b/src/paging.cpp
index e73cfb2..a09639c 100644
--- a/src/paging.cpp
+++ b/src/paging.cpp
@@ -1,12 +1,15 @@
 #include "paging.hpp"
 
-os::paging::page_allocator::page_allocator(phys_ptr<paging::page> one_past_end): begin_(one_past_end.get_phys_addr()), end_(begin_) {
+os::paging::page one_past_end_page_for_page_allocator;
+os::paging::page_allocator_t os::paging::page_allocator(os::phys_ptr<os::paging::page>(reinterpret_cast<uintptr_t>(&one_past_end_page_for_page_allocator) - 0xFFFFFFFF80000000));
+
+os::paging::page_allocator_t::page_allocator_t(phys_ptr<paging::page> one_past_end): begin_(one_past_end.get_phys_addr()), end_(begin_) {
 	end_->prev = nullptr;
 	end_->next = nullptr;
 	end_->size = 1;
 }
 
-void os::paging::page_allocator::print_all() const {
+void os::paging::page_allocator_t::print_all() const {
 	if (is_empty()) {
 		os::println("No RAM left.");
 	} else for (auto it = begin(); it != end(); it = it->next) {
@@ -17,7 +20,7 @@ void os::paging::page_allocator::print_all() const {
 	}
 }
 
-os::paging::page_allocator::block os::paging::page_allocator::allocate(std::uint64_t count) {
+os::paging::page_allocator_t::block os::paging::page_allocator_t::allocate(std::uint64_t count) {
 	for (auto it = begin(); it != end(); it = it->next) {
 		if (count == it->size) {
 			erase(it);
@@ -35,7 +38,7 @@ os::paging::page_allocator::block os::paging::page_allocator::allocate(std::uint
 	}
 	return { .ptr = nullptr, .size = count };
 }
-void os::paging::page_allocator::deallocate(block b) {
+void os::paging::page_allocator_t::deallocate(block b) {
 	if (b.ptr == nullptr) { return; }
 	if (b.size == 0) { return; }
 	const phys_ptr<page> b_it{b.ptr.get_phys_addr()};
@@ -44,13 +47,13 @@ void os::paging::page_allocator::deallocate(block b) {
 	try_merge_next(try_merge_prev(insert(it, b)));
 }
 
-bool os::paging::page_allocator::is_empty() const { return begin() == end(); }
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::begin() { return begin_; }
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::end()   { return end_;   }
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::begin() const { return begin_; }
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::end()   const { return end_;   }
+bool os::paging::page_allocator_t::is_empty() const { return begin() == end(); }
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::begin() { return begin_; }
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::end()   { return end_;   }
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::begin() const { return begin_; }
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::end()   const { return end_;   }
 
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::insert(phys_ptr<page> it, block b) {
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::insert(phys_ptr<page> it, block b) {
 	const phys_ptr<page> b_it{b.ptr.get_phys_addr()};
 	if (it->prev == nullptr) {
 		begin_ = b_it;
@@ -63,21 +66,21 @@ os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::inser
 	b_it->size = b.size;
 	return b_it;
 }
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::try_merge_prev(phys_ptr<page> it) {
-	os::assert(it != end(), "end() passed to page_allocator::try_merge_prev(phys_ptr<page>).");
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::try_merge_prev(phys_ptr<page> it) {
+	os::assert(it != end(), "end() passed to page_allocator_t::try_merge_prev(phys_ptr<page>).");
 	if (it->prev == nullptr) { return it; }
 	if (it->prev + it->prev->size != it) { return it; }
 	it->prev->size += it->size;
 	return erase(it)->prev;
 }
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::try_merge_next(phys_ptr<page> it) {
-	os::assert(it != end(), "end() passed to page_allocator::try_merge_next(phys_ptr<page>).");
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::try_merge_next(phys_ptr<page> it) {
+	os::assert(it != end(), "end() passed to page_allocator_t::try_merge_next(phys_ptr<page>).");
 	if (it->next == end()) return it;
 	try_merge_prev(it->next);
 	return it;
 }
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::erase(phys_ptr<page> it) {
-	os::assert(it != end(), "end() passed to page_allocator::remove(phys_ptr<page>).");
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::erase(phys_ptr<page> it) {
+	os::assert(it != end(), "end() passed to page_allocator_t::remove(phys_ptr<page>).");
 	if (it->prev == nullptr) {
 		begin_ = it->next;
 	} else {
@@ -86,10 +89,10 @@ os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::erase
 	it->next->prev = it->prev;
 	return it->next;
 }
-os::phys_ptr<os::paging::page_allocator::page> os::paging::page_allocator::split_at_offset(phys_ptr<page> it, std::size_t offset) {
-	os::assert(it != end(), "end() passed to page_allocator::split_at_offset(phys_ptr<page>, std::size_t).");
-	os::assert(offset < it->size, "offset passed to page_allocator::split_at_offset(phys_ptr<page>, std::size_t) was too big.");
-	os::assert(offset != 0, "offset 0 passed to page_allocator::split_at_offset(phys_ptr<page>, std::size_t).");
+os::phys_ptr<os::paging::page_allocator_t::page> os::paging::page_allocator_t::split_at_offset(phys_ptr<page> it, std::size_t offset) {
+	os::assert(it != end(), "end() passed to page_allocator_t::split_at_offset(phys_ptr<page>, std::size_t).");
+	os::assert(offset < it->size, "offset passed to page_allocator_t::split_at_offset(phys_ptr<page>, std::size_t) was too big.");
+	os::assert(offset != 0, "offset 0 passed to page_allocator_t::split_at_offset(phys_ptr<page>, std::size_t).");
 	phys_ptr<page> after_split = it + offset;
 	insert(it->next, block{ .ptr = phys_ptr<paging::page>{after_split.get_phys_addr()}, .size = it->size - offset });
 	it->size = offset;
diff --git a/src/paging.hpp b/src/paging.hpp
index dcd3cee..9bc9f25 100644
--- a/src/paging.hpp
+++ b/src/paging.hpp
@@ -131,11 +131,14 @@ struct __attribute__((aligned(0x1000))) paging_table {
 	static_assert(order >= 0, "Paging table of negative order.");
 	paging_entry<order> contents[512];
 };
+static_assert(sizeof(paging_table<0>) == 0x1000);
+static_assert(alignof(paging_table<0>) == 0x1000);
 
 template<>
-struct paging_table<-1> {
-	std::uint8_t contents[0x1000] = {0};
+struct __attribute__((aligned(0x1000))) paging_table<-1> {
 };
+static_assert(sizeof(paging_table<-1>) == 0x1000);
+static_assert(alignof(paging_table<-1>) == 0x1000);
 
 using PML4T = paging_table<3>;
 using PML4E = paging_entry<3>;
@@ -147,14 +150,17 @@ using PT = paging_table<0>;
 using PE = paging_entry<0>;
 using page = paging_table<-1>;
 
-class page_allocator {
+class page_allocator_t;
+extern page_allocator_t page_allocator;
+
+class page_allocator_t {
 public:
 	struct block {
 		phys_ptr<paging::page> ptr = nullptr;
 		std::uint64_t size;
 	};
 
-	page_allocator(phys_ptr<paging::page> one_past_end_page);
+	page_allocator_t(phys_ptr<paging::page> one_past_end_page);
 	void print_all() const;
 
 	block allocate(std::uint64_t page_count);
-- 
2.47.0