From 461605cf0a6a1402a7fa5d4795305e4c9e55167a Mon Sep 17 00:00:00 2001
From: Amelia Coutard <eliottulio.coutard@gmail.com>
Date: Sun, 19 Mar 2023 02:04:17 +0100
Subject: [PATCH] Implemented memset and memcpy, to make some for loops clearer

---
 kernel/src/elf64.cpp        |  8 ++------
 kernel/src/lib/phys_ptr.hpp |  6 ++++++
 kernel/src/paging.cpp       |  8 ++------
 kernel/src/utils.hpp        | 16 ++++++++++++++++
 4 files changed, 26 insertions(+), 12 deletions(-)

diff --git a/kernel/src/elf64.cpp b/kernel/src/elf64.cpp
index a093f02..422d0ba 100644
--- a/kernel/src/elf64.cpp
+++ b/kernel/src/elf64.cpp
@@ -39,9 +39,7 @@ os::process os::elf::load_elf(void* start, std::size_t length, const paging::PML
 	};
 
 	// Copy kernel mappings to the new virtual address space.
-	for (size_t i = 0; i < 256; i++) {
-		result.PML4T->contents[256 + i] = original_PML4T.contents[256 + i];
-	}
+	memcpy(result.PML4T->contents + 256, original_PML4T.contents + 256, 256 * sizeof(os::paging::PML4E));
 
 	for (std::size_t i = 0; i < elf_header.entry_count_program_header_table; i++) {
 		const os::elf::program_header program_header = *(os::elf::program_header*)(
@@ -62,9 +60,7 @@ os::process os::elf::load_elf(void* start, std::size_t length, const paging::PML
 		for (std::size_t i = 0; i < nb_pages; i++) {
 			std::byte* const page =
 				os::paging::setup_page(*result.PML4T, program_header.p_vaddr + i * 0x1000, (program_header.flags & 2) >> 1, 1);
-			for (std::size_t j = 0; j < 0x1000 && j < program_header.p_filesz - i * 0x1000; j++) {
-				page[j] = ((std::byte*)start)[program_header.p_offset + j];
-			}
+			memcpy(page, (std::byte*)start + program_header.p_offset, clamp(0ul, program_header.p_filesz - i * 0x1000, 0x1000ul));
 		}
 	}
 
diff --git a/kernel/src/lib/phys_ptr.hpp b/kernel/src/lib/phys_ptr.hpp
index c736e5f..c42c47e 100644
--- a/kernel/src/lib/phys_ptr.hpp
+++ b/kernel/src/lib/phys_ptr.hpp
@@ -33,6 +33,12 @@ public:
 	T* operator->() const {
 		return get_virt_addr();
 	}
+	explicit operator T*() const {
+		return get_virt_addr();
+	}
+	explicit operator void*() const {
+		return get_virt_addr();
+	}
 
 	constexpr phys_ptr<T>& operator++() {
 		return *this += 1;
diff --git a/kernel/src/paging.cpp b/kernel/src/paging.cpp
index 07d0aec..610a5e9 100644
--- a/kernel/src/paging.cpp
+++ b/kernel/src/paging.cpp
@@ -123,18 +123,14 @@ os::paging::page_allocator_t::block os::paging::page_allocator_t::allocate(std::
 	for (auto it = begin(); it != end(); it = it->next) {
 		if (count == it->size) {
 			erase(it);
-			for (std::size_t i = 0; i < count * 0x1000; i++) {
-				phys_ptr<char>(it.get_phys_addr())[i] = 0;
-			}
+			memset((void*)it, 0, count * 0x1000);
 			return {
 				.ptr = phys_ptr<paging::page>(it.get_phys_addr()),
 				.size = count,
 			};
 		} else if (count < it->size) {
 			erase(split_at_offset(it, count));
-			for (std::size_t i = 0; i < count * 0x1000; i++) {
-				phys_ptr<char>(it.get_phys_addr())[i] = 0;
-			}
+			memset((void*)it, 0, count * 0x1000);
 			return {
 				.ptr = phys_ptr<paging::page>(it.get_phys_addr()),
 				.size = count,
diff --git a/kernel/src/utils.hpp b/kernel/src/utils.hpp
index df3f7db..c203c80 100644
--- a/kernel/src/utils.hpp
+++ b/kernel/src/utils.hpp
@@ -14,6 +14,7 @@
 #pragma once
 
 #include <cstdint>
+#include <cstddef>
 
 namespace os {
 
@@ -26,5 +27,20 @@ std::uint8_t inb(std::uint16_t port);
 bool cpu_has_msr();
 std::uint64_t get_msr(std::uint32_t msr);
 void set_msr(std::uint32_t msr, std::uint64_t v);
+template <typename T> T clamp(T min, T v, T max) {
+	return v < min ? min : max < v ? max : v;
+}
+inline void* memset(void* dest, int c, size_t n) {
+	while (n-- > 0) {
+		reinterpret_cast<std::byte*>(dest)[n] = std::byte(c);
+	}
+	return dest;
+}
+inline void* memcpy(void* dest, const void* src, size_t n) {
+	while (n-- > 0) {
+		reinterpret_cast<std::byte*>(dest)[n] = reinterpret_cast<const std::byte*>(src)[n];
+	}
+	return dest;
+}
 
 } // namespace os
-- 
2.47.0