From fc65d416dc0dbebf7c1bd599653cf22b70b60d06 Mon Sep 17 00:00:00 2001
From: Aren Elchinyan <a2.dev@yandex.ru>
Date: Thu, 9 Jan 2025 16:53:44 +0300
Subject: [PATCH 1/8] Transferring serial port functions to a separate file

---
 kernel/arch/amd64/serial.c | 13 +++++++++++++
 kernel/kernel.c            | 17 +++++------------
 2 files changed, 18 insertions(+), 12 deletions(-)
 create mode 100644 kernel/arch/amd64/serial.c

diff --git a/kernel/arch/amd64/serial.c b/kernel/arch/amd64/serial.c
new file mode 100644
index 0000000..2606e5e
--- /dev/null
+++ b/kernel/arch/amd64/serial.c
@@ -0,0 +1,13 @@
+#include <kstdint.h>
+
+static inline void outb(uint16_t port, uint8_t val) {
+	asm volatile("outb %0, %1" : : "a"(val), "Nd"(port));
+}
+
+void serial_write_byte(uint8_t byte) {
+	outb(0x3f8, byte);
+}
+
+int serial_init() {
+    return -1;
+}
\ No newline at end of file
diff --git a/kernel/kernel.c b/kernel/kernel.c
index d4ddc15..e0ce236 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -1,19 +1,12 @@
 #include <kstdint.h>
 
-uint64_t paging_main[3][512] __attribute__((aligned(4096))) = {0};
+extern void serial_write_byte(uint8_t byte);
 
-static inline void outb(uint16_t port, uint8_t val) {
-	asm volatile("outb %0, %1" : : "a"(val), "Nd"(port));
-}
-
-void hal_write_byte_manual(uint8_t byte) {
-	outb(0x3f8, byte);
-}
 
 void kernel_main64(uint64_t *multiboot, uint32_t magic, void *esp, uint64_t base) {
-    hal_write_byte_manual('[');
-    hal_write_byte_manual('O');
-    hal_write_byte_manual('K');
-    hal_write_byte_manual(']');
+    serial_write_byte('[');
+    serial_write_byte('O');
+    serial_write_byte('K');
+    serial_write_byte(']');
     for(;;) {}
 }
\ No newline at end of file

From ccc88bbd0ddf77085d1d39fb1d7a66a6b52cdca9 Mon Sep 17 00:00:00 2001
From: Aren Elchinyan <a2.dev@yandex.ru>
Date: Thu, 9 Jan 2025 16:54:39 +0300
Subject: [PATCH 2/8] Taking the paging to a separate file

---
 kernel/arch/amd64/paging.c | 8 ++++++++
 1 file changed, 8 insertions(+)
 create mode 100644 kernel/arch/amd64/paging.c

diff --git a/kernel/arch/amd64/paging.c b/kernel/arch/amd64/paging.c
new file mode 100644
index 0000000..9a83cd9
--- /dev/null
+++ b/kernel/arch/amd64/paging.c
@@ -0,0 +1,8 @@
+#include <kstdint.h>
+
+uint64_t paging_main[3][512] __attribute__((aligned(4096))) = {0};
+
+
+int paging_init() {
+    return -1;
+}
\ No newline at end of file

From 00dcc6f4aa6a487f38fbf1b202f5a567acbb92f8 Mon Sep 17 00:00:00 2001
From: Aren Elchinyan <a2.dev@yandex.ru>
Date: Thu, 9 Jan 2025 17:11:43 +0300
Subject: [PATCH 3/8] Fix qemu flags

---
 Makefile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Makefile b/Makefile
index 67561d9..c27cae3 100644
--- a/Makefile
+++ b/Makefile
@@ -27,7 +27,7 @@ kernel/kernel.elf: $(OBJS)
 	as $(ASFLAGS) -o $@ $<
 
 serial.log: cis-os.iso
-	timeout 10s qemu-system-x86_64 -nographic -m 256 -cdrom $< -d guest_errors -serial file:$@ --no-reboot -no-shutdown || true
+	timeout 10s qemu-system-x86_64 -display none -m 256 -cdrom $< -d guest_errors -serial file:$@ --no-reboot -no-shutdown || true
 
 test: serial.log
 	cat $<

From 9e077bf6c9ee48f25761be31a0f76000fbb90868 Mon Sep 17 00:00:00 2001
From: Aren Elchinyan <a2.dev@yandex.ru>
Date: Thu, 9 Jan 2025 17:12:33 +0300
Subject: [PATCH 4/8] Better serial port driver

But very raw!
---
 kernel/arch/amd64/serial.c | 33 ++++++++++++++++++++++++------
 kernel/include/kasm.h      | 41 ++++++++++++++++++++++++++++++++++++++
 kernel/include/khal.h      | 18 +++++++++++++++++
 kernel/kernel.c            |  4 ++--
 4 files changed, 88 insertions(+), 8 deletions(-)
 create mode 100644 kernel/include/kasm.h
 create mode 100644 kernel/include/khal.h

diff --git a/kernel/arch/amd64/serial.c b/kernel/arch/amd64/serial.c
index 2606e5e..4f52a9c 100644
--- a/kernel/arch/amd64/serial.c
+++ b/kernel/arch/amd64/serial.c
@@ -1,13 +1,34 @@
 #include <kstdint.h>
-
-static inline void outb(uint16_t port, uint8_t val) {
-	asm volatile("outb %0, %1" : : "a"(val), "Nd"(port));
-}
+#include <kasm.h>
 
 void serial_write_byte(uint8_t byte) {
-	outb(0x3f8, byte);
+    // Wait until the transmit holding register is empty
+    while ((inb(0x3f8 + 5) & 0x20) == 0);
+    outb(0x3f8, byte);
 }
 
 int serial_init() {
-    return -1;
+    // Disable all interrupts
+    outb(0x3f8 + 1, 0x00);
+
+    // Set divisor latch access bit (DLAB) to set baud rate
+    outb(0x3f8 + 3, 0x80);
+
+    // Set divisor to 12 for 9600 baud (115200 / 9600 = 12)
+    outb(0x3f8, 0x0C); // Low byte of divisor
+    outb(0x3f8 + 1, 0x00); // High byte of divisor (0 for divisor < 256)
+
+    // Disable DLAB and set communication parameters: 8n1 (8 bits, no parity, 1 stop bit)
+    outb(0x3f8 + 3, 0x03);
+
+    // Enable FIFOs
+    outb(0x3f8 + 2, 0xC7); // Enable FIFO, clear Rx and Tx FIFOs
+
+    // Set default line control
+    outb(0x3f8 + 4, 0x0B); // Enable FIFO, RTS, DTR
+
+    // Read Line Status Register to clear any pending errors
+    inb(0x3f8 + 5);
+
+    return 0;
 }
\ No newline at end of file
diff --git a/kernel/include/kasm.h b/kernel/include/kasm.h
new file mode 100644
index 0000000..45dac97
--- /dev/null
+++ b/kernel/include/kasm.h
@@ -0,0 +1,41 @@
+#ifndef __K_ASM
+#define __K_ASM
+
+#include <kstdint.h>
+
+#if defined(__x86_64__)
+static inline void outb(uint16_t port, uint8_t val) {
+    asm volatile("outb %0, %1" : : "a"(val), "Nd"(port));
+}
+
+static inline uint8_t inb(uint16_t port) {
+	uint8_t ret;
+	asm volatile("inb %1, %0" : "=a"(ret) : "Nd"(port));
+	return ret;
+}
+
+static inline void outw(uint16_t port, uint16_t val) {
+	asm volatile("outw %0, %1" : : "a"(val), "Nd"(port));
+}
+
+static inline uint16_t inw(uint16_t port) {
+	uint16_t ret;
+	asm volatile("inw %1, %0" : "=a"(ret) : "Nd"(port));
+	return ret;
+}
+
+static inline void outl(uint16_t port, uint32_t val) {
+	asm volatile("outl %%eax, %%dx" : : "dN"(port), "a"(val));
+}
+
+static inline unsigned int inl(uint16_t port) {
+	uint32_t ret;
+	asm volatile("inl %%dx, %%eax" : "=a"(ret) : "dN"(port));
+	return ret;
+}
+
+#else
+#error "Only AMD64 is supported"
+#endif
+
+#endif
\ No newline at end of file
diff --git a/kernel/include/khal.h b/kernel/include/khal.h
new file mode 100644
index 0000000..8cf606a
--- /dev/null
+++ b/kernel/include/khal.h
@@ -0,0 +1,18 @@
+#ifndef __K_HAL
+#define __K_HAL
+
+#include <kstdint.h>
+#include <kasm.h>
+
+#if defined(__x86_64__)
+
+extern uint64_t paging_main[3][512] __attribute__((aligned(4096)));
+
+void serial_write_byte(uint8_t byte);
+int serial_init();
+
+#else
+#error "Only AMD64 is supported"
+#endif
+
+#endif
\ No newline at end of file
diff --git a/kernel/kernel.c b/kernel/kernel.c
index e0ce236..010f9b2 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -1,9 +1,9 @@
 #include <kstdint.h>
-
-extern void serial_write_byte(uint8_t byte);
+#include <khal.h>
 
 
 void kernel_main64(uint64_t *multiboot, uint32_t magic, void *esp, uint64_t base) {
+    serial_init();
     serial_write_byte('[');
     serial_write_byte('O');
     serial_write_byte('K');

From 0f2781ce89ca6258ba36a5784b53a6389b4e5462 Mon Sep 17 00:00:00 2001
From: Aren Elchinyan <a2.dev@yandex.ru>
Date: Thu, 9 Jan 2025 17:23:05 +0300
Subject: [PATCH 5/8] Add some inline stuff

---
 kernel/include/kasm.h | 42 ++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 42 insertions(+)

diff --git a/kernel/include/kasm.h b/kernel/include/kasm.h
index 45dac97..dd7cbe0 100644
--- a/kernel/include/kasm.h
+++ b/kernel/include/kasm.h
@@ -34,6 +34,48 @@ static inline unsigned int inl(uint16_t port) {
 	return ret;
 }
 
+// https://wiki.osdev.org/Inline_Assembly/Examples
+static inline void io_wait() {
+    outb(0x80, 0);
+}
+
+static inline void lidt(void* base, uint16_t size) {
+    // This function works in 32 and 64bit mode
+    struct {
+        uint16_t length;
+        void*    base;
+    } __attribute__((packed)) IDTR = { size, base };
+
+    asm ( "lidt %0" : : "m"(IDTR) );  // let the compiler choose an addressing mode
+}
+
+uint64_t rdtsc() {
+    uint32_t low, high;
+    asm volatile("rdtsc":"=a"(low),"=d"(high));
+    return ((uint64_t)high << 32) | low;
+}
+
+static inline void wrmsr(uint64_t msr, uint64_t value) {
+    uint32_t low = value & 0xFFFFFFFF;
+    uint32_t high = value >> 32;
+    asm volatile (
+        "wrmsr"
+        :
+        : "c"(msr), "a"(low), "d"(high)
+    );
+}
+
+static inline uint64_t rdmsr(uint64_t msr) {
+    uint32_t low, high;
+    asm volatile (
+        "rdmsr"
+        : "=a"(low), "=d"(high)
+        : "c"(msr)
+    );
+	return ((uint64_t)high << 32) | low;
+}
+
+
 #else
 #error "Only AMD64 is supported"
 #endif

From f2cc441d5dabc397db2c727fc397c4e29b09942b Mon Sep 17 00:00:00 2001
From: Aren Elchinyan <a2.dev@yandex.ru>
Date: Thu, 9 Jan 2025 17:32:56 +0300
Subject: [PATCH 6/8] Add clang-format

---
 .clang-format | 30 ++++++++++++++++++++++++++++++
 Makefile      |  5 ++++-
 README.md     |  2 +-
 3 files changed, 35 insertions(+), 2 deletions(-)
 create mode 100644 .clang-format

diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..2896996
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,30 @@
+ColumnLimit: 100
+IndentWidth: 4
+UseTab: ForIndentation
+TabWidth: 4
+SpacesBeforeTrailingComments: 1
+NamespaceIndentation: None
+AlignConsecutiveAssignments: false
+AllowAllParametersOfDeclarationOnNextLine: true
+AllowShortBlocksOnASingleLine: true
+AllowShortFunctionsOnASingleLine: Inline
+AllowShortCaseLabelsOnASingleLine: true
+AllowShortIfStatementsOnASingleLine: true
+AllowShortLoopsOnASingleLine: true
+BreakBeforeBinaryOperators: None
+BreakBeforeTernaryOperators: true
+BreakConstructorInitializersBeforeComma: false
+ConstructorInitializerAllOnOneLineOrOnePerLine: true
+DerivePointerAlignment: true
+IndentCaseLabels: true
+KeepEmptyLinesAtTheStartOfBlocks: false
+PointerAlignment: Right
+ContinuationIndentWidth: 4
+SpacesInParentheses: false
+SpacesInSquareBrackets: false
+SpacesInAngles: false
+SpaceInEmptyParentheses: true
+IndentPPDirectives: None
+IncludeBlocks: Preserve
+Cpp11BracedListStyle: false
+Standard: Cpp11
\ No newline at end of file
diff --git a/Makefile b/Makefile
index c27cae3..c11dc17 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@ $(shell mkdir -p $(dir $(OBJS)))
 CFLAGS = -m64 -Wall -Werror -std=gnu11 -Ikernel/include -ffreestanding -O0 -fno-stack-protector 
 ASFLAGS = -64
 
-.PHONY: all run test clean
+.PHONY: all run test clean format
 
 all: cis-os.iso
 
@@ -42,3 +42,6 @@ clean:
 	rm -rf kernel/kernel.elf cis-os.iso
 	find kernel/ -name "*.o" -delete
 	rm -f serial.log
+
+format:
+	find . -type d -name "3rd" -prune -o -type f \( -name "*.c" -o -name "*.h" \) -print0 | xargs -0 clang-format -i -style=file
diff --git a/README.md b/README.md
index 5a7c655..93a4a9a 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,7 @@ Users: 0
 
 1. Установите необходимые инструменты:
 ```bash
-sudo apt install gcc build-essential grub2-common qemu-system-x86 xorriso mtools
+sudo apt install gcc build-essential grub2-common qemu-system-x86 xorriso mtools clang-format
 ```
 
 2. Соберите проект:

From d9382449b57caf5a8457a51ca56ca8941e026dd4 Mon Sep 17 00:00:00 2001
From: Aren Elchinyan <a2.dev@yandex.ru>
Date: Thu, 9 Jan 2025 17:49:16 +0300
Subject: [PATCH 7/8] Fix "missing .note.GNU-stack section implies executable
 stack"

---
 Makefile                 | 2 +-
 kernel/arch/amd64/boot.s | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/Makefile b/Makefile
index c11dc17..273f612 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,7 @@ cis-os.iso: kernel/kernel.elf boot/grub.cfg
 	grub-mkrescue -o cis-os.iso isodir
 
 kernel/kernel.elf: $(OBJS)
-	ld -nostdlib -o $@ -T scripts/linker.ld $(OBJS)
+	ld -z noexecstack -nostdlib -o $@ -T scripts/linker.ld $(OBJS)
 
 %.o: %.c
 	gcc $(CFLAGS) -c -o $@ $<
diff --git a/kernel/arch/amd64/boot.s b/kernel/arch/amd64/boot.s
index 77d3f69..3493246 100644
--- a/kernel/arch/amd64/boot.s
+++ b/kernel/arch/amd64/boot.s
@@ -180,4 +180,4 @@ amd64:
 halt:
     cli
     hlt
-    jmp halt
\ No newline at end of file
+    jmp halt

From 26d69bb1de50e72c09c89c201bca2a71129feafa Mon Sep 17 00:00:00 2001
From: Aren Elchinyan <a2.dev@yandex.ru>
Date: Thu, 9 Jan 2025 17:49:33 +0300
Subject: [PATCH 8/8] Add multiboot bones

---
 boot/grub.cfg                  |   1 +
 kernel/arch/amd64/idt.c        |  12 ++
 kernel/arch/amd64/paging.c     |   7 +-
 kernel/arch/amd64/serial.c     |  43 +++---
 kernel/include/3rd/multiboot.h | 274 +++++++++++++++++++++++++++++++++
 kernel/include/kasm.h          |  45 +++---
 kernel/include/khal.h          |   4 +-
 kernel/kernel.c                |  16 +-
 kernel/multiboot.c             | 147 ++++++++++++++++++
 9 files changed, 488 insertions(+), 61 deletions(-)
 create mode 100644 kernel/arch/amd64/idt.c
 create mode 100644 kernel/include/3rd/multiboot.h
 create mode 100644 kernel/multiboot.c

diff --git a/boot/grub.cfg b/boot/grub.cfg
index 5cd3676..59e04b5 100644
--- a/boot/grub.cfg
+++ b/boot/grub.cfg
@@ -3,4 +3,5 @@ set default=0
 
 menuentry "CIS-OS" {
     multiboot /boot/kernel.elf
+    module  /initrd.cpio
 }
\ No newline at end of file
diff --git a/kernel/arch/amd64/idt.c b/kernel/arch/amd64/idt.c
new file mode 100644
index 0000000..8748efe
--- /dev/null
+++ b/kernel/arch/amd64/idt.c
@@ -0,0 +1,12 @@
+#include <kstdint.h>
+
+// From https://wiki.osdev.org/Interrupt_Descriptor_Table#Structure_on_x86-64
+struct idt_64 {
+	uint16_t offset_1;       // offset bits 0..15
+	uint16_t selector;       // a code segment selector in GDT or LDT
+	uint8_t ist;             // bits 0..2 holds Interrupt Stack Table offset, rest of bits zero.
+	uint8_t type_attributes; // gate type, dpl, and p fields
+	uint16_t offset_2;       // offset bits 16..31
+	uint32_t offset_3;       // offset bits 32..63
+	uint32_t zero;           // reserved
+};
\ No newline at end of file
diff --git a/kernel/arch/amd64/paging.c b/kernel/arch/amd64/paging.c
index 9a83cd9..2ca544d 100644
--- a/kernel/arch/amd64/paging.c
+++ b/kernel/arch/amd64/paging.c
@@ -1,8 +1,7 @@
 #include <kstdint.h>
 
-uint64_t paging_main[3][512] __attribute__((aligned(4096))) = {0};
+uint64_t paging_main[3][512] __attribute__((aligned(4096))) = { 0 };
 
-
-int paging_init() {
-    return -1;
+int paging_init( ) {
+	return -1;
 }
\ No newline at end of file
diff --git a/kernel/arch/amd64/serial.c b/kernel/arch/amd64/serial.c
index 4f52a9c..d22c49a 100644
--- a/kernel/arch/amd64/serial.c
+++ b/kernel/arch/amd64/serial.c
@@ -1,34 +1,35 @@
-#include <kstdint.h>
 #include <kasm.h>
+#include <kstdint.h>
 
 void serial_write_byte(uint8_t byte) {
-    // Wait until the transmit holding register is empty
-    while ((inb(0x3f8 + 5) & 0x20) == 0);
-    outb(0x3f8, byte);
+	// Wait until the transmit holding register is empty
+	while ((inb(0x3f8 + 5) & 0x20) == 0)
+		;
+	outb(0x3f8, byte);
 }
 
-int serial_init() {
-    // Disable all interrupts
-    outb(0x3f8 + 1, 0x00);
+int serial_init( ) {
+	// Disable all interrupts
+	outb(0x3f8 + 1, 0x00);
 
-    // Set divisor latch access bit (DLAB) to set baud rate
-    outb(0x3f8 + 3, 0x80);
+	// Set divisor latch access bit (DLAB) to set baud rate
+	outb(0x3f8 + 3, 0x80);
 
-    // Set divisor to 12 for 9600 baud (115200 / 9600 = 12)
-    outb(0x3f8, 0x0C); // Low byte of divisor
-    outb(0x3f8 + 1, 0x00); // High byte of divisor (0 for divisor < 256)
+	// Set divisor to 12 for 9600 baud (115200 / 9600 = 12)
+	outb(0x3f8, 0x0C);     // Low byte of divisor
+	outb(0x3f8 + 1, 0x00); // High byte of divisor (0 for divisor < 256)
 
-    // Disable DLAB and set communication parameters: 8n1 (8 bits, no parity, 1 stop bit)
-    outb(0x3f8 + 3, 0x03);
+	// Disable DLAB and set communication parameters: 8n1 (8 bits, no parity, 1 stop bit)
+	outb(0x3f8 + 3, 0x03);
 
-    // Enable FIFOs
-    outb(0x3f8 + 2, 0xC7); // Enable FIFO, clear Rx and Tx FIFOs
+	// Enable FIFOs
+	outb(0x3f8 + 2, 0xC7); // Enable FIFO, clear Rx and Tx FIFOs
 
-    // Set default line control
-    outb(0x3f8 + 4, 0x0B); // Enable FIFO, RTS, DTR
+	// Set default line control
+	outb(0x3f8 + 4, 0x0B); // Enable FIFO, RTS, DTR
 
-    // Read Line Status Register to clear any pending errors
-    inb(0x3f8 + 5);
+	// Read Line Status Register to clear any pending errors
+	inb(0x3f8 + 5);
 
-    return 0;
+	return 0;
 }
\ No newline at end of file
diff --git a/kernel/include/3rd/multiboot.h b/kernel/include/3rd/multiboot.h
new file mode 100644
index 0000000..269cf9b
--- /dev/null
+++ b/kernel/include/3rd/multiboot.h
@@ -0,0 +1,274 @@
+/* multiboot.h - Multiboot header file. */
+/* Copyright (C) 1999,2003,2007,2008,2009,2010  Free Software Foundation, Inc.
+ *
+ *  Permission is hereby granted, free of charge, to any person obtaining a copy
+ *  of this software and associated documentation files (the "Software"), to
+ *  deal in the Software without restriction, including without limitation the
+ *  rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ *  sell copies of the Software, and to permit persons to whom the Software is
+ *  furnished to do so, subject to the following conditions:
+ *
+ *  The above copyright notice and this permission notice shall be included in
+ *  all copies or substantial portions of the Software.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL ANY
+ *  DEVELOPER OR DISTRIBUTOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+ *  WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR
+ *  IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef MULTIBOOT_HEADER
+#define MULTIBOOT_HEADER 1
+
+/* How many bytes from the start of the file we search for the header. */
+#define MULTIBOOT_SEARCH                        8192
+#define MULTIBOOT_HEADER_ALIGN                  4
+
+/* The magic field should contain this. */
+#define MULTIBOOT_HEADER_MAGIC                  0x1BADB002
+
+/* This should be in %eax. */
+#define MULTIBOOT_BOOTLOADER_MAGIC              0x2BADB002
+
+/* Alignment of multiboot modules. */
+#define MULTIBOOT_MOD_ALIGN                     0x00001000
+
+/* Alignment of the multiboot info structure. */
+#define MULTIBOOT_INFO_ALIGN                    0x00000004
+
+/* Flags set in the ’flags’ member of the multiboot header. */
+
+/* Align all boot modules on i386 page (4KB) boundaries. */
+#define MULTIBOOT_PAGE_ALIGN                    0x00000001
+
+/* Must pass memory information to OS. */
+#define MULTIBOOT_MEMORY_INFO                   0x00000002
+
+/* Must pass video information to OS. */
+#define MULTIBOOT_VIDEO_MODE                    0x00000004
+
+/* This flag indicates the use of the address fields in the header. */
+#define MULTIBOOT_AOUT_KLUDGE                   0x00010000
+
+/* Flags to be set in the ’flags’ member of the multiboot info structure. */
+
+/* is there basic lower/upper memory information? */
+#define MULTIBOOT_INFO_MEMORY                   0x00000001
+/* is there a boot device set? */
+#define MULTIBOOT_INFO_BOOTDEV                  0x00000002
+/* is the command-line defined? */
+#define MULTIBOOT_INFO_CMDLINE                  0x00000004
+/* are there modules to do something with? */
+#define MULTIBOOT_INFO_MODS                     0x00000008
+
+/* These next two are mutually exclusive */
+
+/* is there a symbol table loaded? */
+#define MULTIBOOT_INFO_AOUT_SYMS                0x00000010
+/* is there an ELF section header table? */
+#define MULTIBOOT_INFO_ELF_SHDR                 0X00000020
+
+/* is there a full memory map? */
+#define MULTIBOOT_INFO_MEM_MAP                  0x00000040
+
+/* Is there drive info? */
+#define MULTIBOOT_INFO_DRIVE_INFO               0x00000080
+
+/* Is there a config table? */
+#define MULTIBOOT_INFO_CONFIG_TABLE             0x00000100
+
+/* Is there a boot loader name? */
+#define MULTIBOOT_INFO_BOOT_LOADER_NAME         0x00000200
+
+/* Is there a APM table? */
+#define MULTIBOOT_INFO_APM_TABLE                0x00000400
+
+/* Is there video information? */
+#define MULTIBOOT_INFO_VBE_INFO                 0x00000800
+#define MULTIBOOT_INFO_FRAMEBUFFER_INFO         0x00001000
+
+#ifndef ASM_FILE
+
+typedef unsigned char           multiboot_uint8_t;
+typedef unsigned short          multiboot_uint16_t;
+typedef unsigned int            multiboot_uint32_t;
+typedef unsigned long long      multiboot_uint64_t;
+
+struct multiboot_header
+{
+  /* Must be MULTIBOOT_MAGIC - see above. */
+  multiboot_uint32_t magic;
+
+  /* Feature flags. */
+  multiboot_uint32_t flags;
+
+  /* The above fields plus this one must equal 0 mod 2^32. */
+  multiboot_uint32_t checksum;
+
+  /* These are only valid if MULTIBOOT_AOUT_KLUDGE is set. */
+  multiboot_uint32_t header_addr;
+  multiboot_uint32_t load_addr;
+  multiboot_uint32_t load_end_addr;
+  multiboot_uint32_t bss_end_addr;
+  multiboot_uint32_t entry_addr;
+
+  /* These are only valid if MULTIBOOT_VIDEO_MODE is set. */
+  multiboot_uint32_t mode_type;
+  multiboot_uint32_t width;
+  multiboot_uint32_t height;
+  multiboot_uint32_t depth;
+};
+
+/* The symbol table for a.out. */
+struct multiboot_aout_symbol_table
+{
+  multiboot_uint32_t tabsize;
+  multiboot_uint32_t strsize;
+  multiboot_uint32_t addr;
+  multiboot_uint32_t reserved;
+};
+typedef struct multiboot_aout_symbol_table multiboot_aout_symbol_table_t;
+
+/* The section header table for ELF. */
+struct multiboot_elf_section_header_table
+{
+  multiboot_uint32_t num;
+  multiboot_uint32_t size;
+  multiboot_uint32_t addr;
+  multiboot_uint32_t shndx;
+};
+typedef struct multiboot_elf_section_header_table multiboot_elf_section_header_table_t;
+
+struct multiboot_info
+{
+  /* Multiboot info version number */
+  multiboot_uint32_t flags;
+
+  /* Available memory from BIOS */
+  multiboot_uint32_t mem_lower;
+  multiboot_uint32_t mem_upper;
+
+  /* "root" partition */
+  multiboot_uint32_t boot_device;
+
+  /* Kernel command line */
+  multiboot_uint32_t cmdline;
+
+  /* Boot-Module list */
+  multiboot_uint32_t mods_count;
+  multiboot_uint32_t mods_addr;
+
+  union
+  {
+    multiboot_aout_symbol_table_t aout_sym;
+    multiboot_elf_section_header_table_t elf_sec;
+  } u;
+
+  /* Memory Mapping buffer */
+  multiboot_uint32_t mmap_length;
+  multiboot_uint32_t mmap_addr;
+
+  /* Drive Info buffer */
+  multiboot_uint32_t drives_length;
+  multiboot_uint32_t drives_addr;
+
+  /* ROM configuration table */
+  multiboot_uint32_t config_table;
+
+  /* Boot Loader Name */
+  multiboot_uint32_t boot_loader_name;
+
+  /* APM table */
+  multiboot_uint32_t apm_table;
+
+  /* Video */
+  multiboot_uint32_t vbe_control_info;
+  multiboot_uint32_t vbe_mode_info;
+  multiboot_uint16_t vbe_mode;
+  multiboot_uint16_t vbe_interface_seg;
+  multiboot_uint16_t vbe_interface_off;
+  multiboot_uint16_t vbe_interface_len;
+
+  multiboot_uint64_t framebuffer_addr;
+  multiboot_uint32_t framebuffer_pitch;
+  multiboot_uint32_t framebuffer_width;
+  multiboot_uint32_t framebuffer_height;
+  multiboot_uint8_t framebuffer_bpp;
+#define MULTIBOOT_FRAMEBUFFER_TYPE_INDEXED 0
+#define MULTIBOOT_FRAMEBUFFER_TYPE_RGB     1
+#define MULTIBOOT_FRAMEBUFFER_TYPE_EGA_TEXT     2
+  multiboot_uint8_t framebuffer_type;
+  union
+  {
+    struct
+    {
+      multiboot_uint32_t framebuffer_palette_addr;
+      multiboot_uint16_t framebuffer_palette_num_colors;
+    };
+    struct
+    {
+      multiboot_uint8_t framebuffer_red_field_position;
+      multiboot_uint8_t framebuffer_red_mask_size;
+      multiboot_uint8_t framebuffer_green_field_position;
+      multiboot_uint8_t framebuffer_green_mask_size;
+      multiboot_uint8_t framebuffer_blue_field_position;
+      multiboot_uint8_t framebuffer_blue_mask_size;
+    };
+  };
+};
+typedef struct multiboot_info multiboot_info_t;
+
+struct multiboot_color
+{
+  multiboot_uint8_t red;
+  multiboot_uint8_t green;
+  multiboot_uint8_t blue;
+};
+
+struct multiboot_mmap_entry
+{
+  multiboot_uint32_t size;
+  multiboot_uint64_t addr;
+  multiboot_uint64_t len;
+#define MULTIBOOT_MEMORY_AVAILABLE              1
+#define MULTIBOOT_MEMORY_RESERVED               2
+#define MULTIBOOT_MEMORY_ACPI_RECLAIMABLE       3
+#define MULTIBOOT_MEMORY_NVS                    4
+#define MULTIBOOT_MEMORY_BADRAM                 5
+  multiboot_uint32_t type;
+} __attribute__((packed));
+typedef struct multiboot_mmap_entry multiboot_memory_map_t;
+
+struct multiboot_mod_list
+{
+  /* the memory used goes from bytes ’mod_start’ to ’mod_end-1’ inclusive */
+  multiboot_uint32_t mod_start;
+  multiboot_uint32_t mod_end;
+
+  /* Module command line */
+  multiboot_uint32_t cmdline;
+
+  /* padding to take it to 16 bytes (must be zero) */
+  multiboot_uint32_t pad;
+};
+typedef struct multiboot_mod_list multiboot_module_t;
+
+/* APM BIOS info. */
+struct multiboot_apm_info
+{
+  multiboot_uint16_t version;
+  multiboot_uint16_t cseg;
+  multiboot_uint32_t offset;
+  multiboot_uint16_t cseg_16;
+  multiboot_uint16_t dseg;
+  multiboot_uint16_t flags;
+  multiboot_uint16_t cseg_len;
+  multiboot_uint16_t cseg_16_len;
+  multiboot_uint16_t dseg_len;
+};
+
+#endif /* ! ASM_FILE */
+
+#endif /* ! MULTIBOOT_HEADER */
diff --git a/kernel/include/kasm.h b/kernel/include/kasm.h
index dd7cbe0..0dba1b8 100644
--- a/kernel/include/kasm.h
+++ b/kernel/include/kasm.h
@@ -5,7 +5,7 @@
 
 #if defined(__x86_64__)
 static inline void outb(uint16_t port, uint8_t val) {
-    asm volatile("outb %0, %1" : : "a"(val), "Nd"(port));
+	asm volatile("outb %0, %1" : : "a"(val), "Nd"(port));
 }
 
 static inline uint8_t inb(uint16_t port) {
@@ -35,47 +35,38 @@ static inline unsigned int inl(uint16_t port) {
 }
 
 // https://wiki.osdev.org/Inline_Assembly/Examples
-static inline void io_wait() {
-    outb(0x80, 0);
+static inline void io_wait( ) {
+	outb(0x80, 0);
 }
 
 static inline void lidt(void* base, uint16_t size) {
-    // This function works in 32 and 64bit mode
-    struct {
-        uint16_t length;
-        void*    base;
-    } __attribute__((packed)) IDTR = { size, base };
+	// This function works in 32 and 64bit mode
+	struct {
+		uint16_t length;
+		void* base;
+	} __attribute__((packed)) IDTR = { size, base };
 
-    asm ( "lidt %0" : : "m"(IDTR) );  // let the compiler choose an addressing mode
+	asm("lidt %0" : : "m"(IDTR)); // let the compiler choose an addressing mode
 }
 
-uint64_t rdtsc() {
-    uint32_t low, high;
-    asm volatile("rdtsc":"=a"(low),"=d"(high));
-    return ((uint64_t)high << 32) | low;
+static inline uint64_t rdtsc( ) {
+	uint32_t low, high;
+	asm volatile("rdtsc" : "=a"(low), "=d"(high));
+	return ((uint64_t)high << 32) | low;
 }
 
 static inline void wrmsr(uint64_t msr, uint64_t value) {
-    uint32_t low = value & 0xFFFFFFFF;
-    uint32_t high = value >> 32;
-    asm volatile (
-        "wrmsr"
-        :
-        : "c"(msr), "a"(low), "d"(high)
-    );
+	uint32_t low = value & 0xFFFFFFFF;
+	uint32_t high = value >> 32;
+	asm volatile("wrmsr" : : "c"(msr), "a"(low), "d"(high));
 }
 
 static inline uint64_t rdmsr(uint64_t msr) {
-    uint32_t low, high;
-    asm volatile (
-        "rdmsr"
-        : "=a"(low), "=d"(high)
-        : "c"(msr)
-    );
+	uint32_t low, high;
+	asm volatile("rdmsr" : "=a"(low), "=d"(high) : "c"(msr));
 	return ((uint64_t)high << 32) | low;
 }
 
-
 #else
 #error "Only AMD64 is supported"
 #endif
diff --git a/kernel/include/khal.h b/kernel/include/khal.h
index 8cf606a..c1837b6 100644
--- a/kernel/include/khal.h
+++ b/kernel/include/khal.h
@@ -1,15 +1,15 @@
 #ifndef __K_HAL
 #define __K_HAL
 
-#include <kstdint.h>
 #include <kasm.h>
+#include <kstdint.h>
 
 #if defined(__x86_64__)
 
 extern uint64_t paging_main[3][512] __attribute__((aligned(4096)));
 
 void serial_write_byte(uint8_t byte);
-int serial_init();
+int serial_init( );
 
 #else
 #error "Only AMD64 is supported"
diff --git a/kernel/kernel.c b/kernel/kernel.c
index 010f9b2..874afe0 100644
--- a/kernel/kernel.c
+++ b/kernel/kernel.c
@@ -1,12 +1,14 @@
-#include <kstdint.h>
 #include <khal.h>
+#include <kstdint.h>
 
+int multiboot_init(uint64_t *addr, uint32_t magic);
 
 void kernel_main64(uint64_t *multiboot, uint32_t magic, void *esp, uint64_t base) {
-    serial_init();
-    serial_write_byte('[');
-    serial_write_byte('O');
-    serial_write_byte('K');
-    serial_write_byte(']');
-    for(;;) {}
+	serial_init( );
+	multiboot_init(multiboot, magic);
+	serial_write_byte('[');
+	serial_write_byte('O');
+	serial_write_byte('K');
+	serial_write_byte(']');
+	for (;;) {}
 }
\ No newline at end of file
diff --git a/kernel/multiboot.c b/kernel/multiboot.c
new file mode 100644
index 0000000..485ed25
--- /dev/null
+++ b/kernel/multiboot.c
@@ -0,0 +1,147 @@
+#include <3rd/multiboot.h>
+#include <kstdint.h>
+
+#define CHECK_FLAG(flags, bit) ((flags) & (1 << (bit)))
+#define printf(...)
+
+int multiboot_init(uint64_t *addr, uint32_t magic) {
+	multiboot_info_t *mbi;
+
+	/* Am I booted by a Multiboot-compliant boot loader? */
+	if (magic != MULTIBOOT_BOOTLOADER_MAGIC) {
+		printf("Invalid magic number: 0x%x\n", (unsigned)magic);
+		return -1;
+	}
+
+	/* Set MBI to the address of the Multiboot information structure. */
+	mbi = (multiboot_info_t *)addr;
+
+	/* Print out the flags. */
+	printf("flags = 0x%x\n", (unsigned)mbi->flags);
+
+	/* Are mem_* valid? */
+	if (CHECK_FLAG(mbi->flags, 0))
+		printf("mem_lower = %uKB, mem_upper = %uKB\n", (unsigned)mbi->mem_lower,
+		       (unsigned)mbi->mem_upper);
+
+	/* Is boot_device valid? */
+	if (CHECK_FLAG(mbi->flags, 1)) printf("boot_device = 0x%x\n", (unsigned)mbi->boot_device);
+
+	/* Is the command line passed? */
+	if (CHECK_FLAG(mbi->flags, 2)) printf("cmdline = %s\n", (char *)mbi->cmdline);
+
+	/* Are mods_* valid? */
+	if (CHECK_FLAG(mbi->flags, 3)) {
+		multiboot_module_t *mod = (multiboot_module_t *)(uint64_t)mbi->mods_addr;
+		printf("mods_count = %d, mods_addr = 0x%x\n", (int)mbi->mods_count, (int)mbi->mods_addr);
+		for (int i = 0; i < mbi->mods_count; i++, mod++)
+			printf(" mod_start = 0x%x, mod_end = 0x%x, cmdline = %s\n", (unsigned)mod->mod_start,
+			       (unsigned)mod->mod_end, (char *)mod->cmdline);
+	}
+
+	/* Bits 4 and 5 are mutually exclusive! */
+	if (CHECK_FLAG(mbi->flags, 4) && CHECK_FLAG(mbi->flags, 5)) {
+		printf("Both bits 4 and 5 are set.\n");
+		return -1;
+	}
+
+	/* Is the symbol table of a.out valid? */
+	if (CHECK_FLAG(mbi->flags, 4)) {
+		multiboot_aout_symbol_table_t *multiboot_aout_sym __attribute__((unused)) =
+		    &(mbi->u.aout_sym);
+
+		printf("multiboot_aout_symbol_table: tabsize = 0x%0x, "
+		       "strsize = 0x%x, addr = 0x%x\n",
+		       (unsigned)multiboot_aout_sym->tabsize, (unsigned)multiboot_aout_sym->strsize,
+		       (unsigned)multiboot_aout_sym->addr);
+	}
+
+	/* Is the section header table of ELF valid? */
+	if (CHECK_FLAG(mbi->flags, 5)) {
+		multiboot_elf_section_header_table_t *multiboot_elf_sec __attribute__((unused)) =
+		    &(mbi->u.elf_sec);
+
+		printf("multiboot_elf_sec: num = %u, size = 0x%x,"
+		       " addr = 0x%x, shndx = 0x%x\n",
+		       (unsigned)multiboot_elf_sec->num, (unsigned)multiboot_elf_sec->size,
+		       (unsigned)multiboot_elf_sec->addr, (unsigned)multiboot_elf_sec->shndx);
+	}
+
+	/* Are mmap_* valid? */
+	if (CHECK_FLAG(mbi->flags, 6)) {
+		multiboot_memory_map_t *mmap;
+
+		printf("mmap_addr = 0x%x, mmap_length = 0x%x\n", (unsigned)mbi->mmap_addr,
+		       (unsigned)mbi->mmap_length);
+		for (mmap = (multiboot_memory_map_t *)(uint64_t)mbi->mmap_addr;
+		     (unsigned long)mmap < mbi->mmap_addr + mbi->mmap_length;
+		     mmap =
+		         (multiboot_memory_map_t *)((unsigned long)mmap + mmap->size + sizeof(mmap->size)))
+			printf(" size = 0x%x, base_addr = 0x%x%08x,"
+			       " length = 0x%x%08x, type = 0x%x\n",
+			       (unsigned)mmap->size, (unsigned)(mmap->addr >> 32),
+			       (unsigned)(mmap->addr & 0xffffffff), (unsigned)(mmap->len >> 32),
+			       (unsigned)(mmap->len & 0xffffffff), (unsigned)mmap->type);
+	}
+
+	/* Draw diagonal blue line. */
+	if (CHECK_FLAG(mbi->flags, 12)) {
+		multiboot_uint32_t color;
+		unsigned i;
+		void *fb = (void *)(unsigned long)mbi->framebuffer_addr;
+
+		switch (mbi->framebuffer_type) {
+			case MULTIBOOT_FRAMEBUFFER_TYPE_INDEXED: {
+				unsigned best_distance, distance;
+				struct multiboot_color *palette;
+
+				palette = (struct multiboot_color *)(uint64_t)mbi->framebuffer_palette_addr;
+
+				color = 0;
+				best_distance = 4 * 256 * 256;
+
+				for (i = 0; i < mbi->framebuffer_palette_num_colors; i++) {
+					distance = (0xff - palette[i].blue) * (0xff - palette[i].blue) +
+					           palette[i].red * palette[i].red +
+					           palette[i].green * palette[i].green;
+					if (distance < best_distance) {
+						color = i;
+						best_distance = distance;
+					}
+				}
+			} break;
+
+			case MULTIBOOT_FRAMEBUFFER_TYPE_RGB:
+				color = ((1 << mbi->framebuffer_blue_mask_size) - 1)
+				        << mbi->framebuffer_blue_field_position;
+				break;
+
+			case MULTIBOOT_FRAMEBUFFER_TYPE_EGA_TEXT: color = '\\' | 0x0100; break;
+
+			default: color = 0xffffffff; break;
+		}
+		for (i = 0; i < mbi->framebuffer_width && i < mbi->framebuffer_height; i++) {
+			switch (mbi->framebuffer_bpp) {
+				case 8: {
+					multiboot_uint8_t *pixel = fb + mbi->framebuffer_pitch * i + i;
+					*pixel = color;
+				} break;
+				case 15:
+				case 16: {
+					multiboot_uint16_t *pixel = fb + mbi->framebuffer_pitch * i + 2 * i;
+					*pixel = color;
+				} break;
+				case 24: {
+					multiboot_uint32_t *pixel = fb + mbi->framebuffer_pitch * i + 3 * i;
+					*pixel = (color & 0xffffff) | (*pixel & 0xff000000);
+				} break;
+
+				case 32: {
+					multiboot_uint32_t *pixel = fb + mbi->framebuffer_pitch * i + 4 * i;
+					*pixel = color;
+				} break;
+			}
+		}
+	}
+	return 1;
+}
\ No newline at end of file