Kernel: Start using multiboot2 instead of multiboot

This allows better compatibility with (U)EFI and gives RSDP location
instead of me having to scan ram to find it.

kernel/arch/x86_64/PageTable.cpp

@@ -4,6 +4,7 @@
 #include <kernel/LockGuard.h>
 #include <kernel/Memory/kmalloc.h>
 #include <kernel/Memory/PageTable.h>
+#include <kernel/multiboot2.h>
 
 extern uint8_t g_kernel_start[];
 extern uint8_t g_kernel_end[];
@@ -138,6 +139,16 @@ namespace Kernel
 		// Map (0 -> phys_kernel_end) to (KERNEL_OFFSET -> virt_kernel_end)
 		map_range_at(0, KERNEL_OFFSET, (uintptr_t)g_kernel_end - KERNEL_OFFSET, Flags::ReadWrite | Flags::Present);
 		
+		// Map multiboot info
+		vaddr_t multiboot_data_start = (vaddr_t)g_multiboot2_info & PAGE_ADDR_MASK;
+		vaddr_t multiboot_data_end = (vaddr_t)g_multiboot2_info + g_multiboot2_info->total_size;
+		map_range_at(
+			V2P(multiboot_data_start),
+			multiboot_data_start,
+			multiboot_data_end - multiboot_data_start,
+			Flags::ReadWrite | Flags::Present
+		);
+
 		// Map executable kernel memory as executable
 		map_range_at(
 			V2P(g_kernel_execute_start),

kernel/arch/x86_64/boot.S

@@ -1,11 +1,3 @@
-# Declare constants for the multiboot header
-.set ALIGN,			1<<0						# align loaded modules on page boundaries
-.set MEMINFO,		1<<1						# provide memory map
-.set VIDEOINFO,		1<<2						# provide video info
-.set MB_FLAGS,		ALIGN | MEMINFO | VIDEOINFO # this is the Multiboot 'flag' field
-.set MB_MAGIC,		0x1BADB002					# 'magic number' lets bootloader find the header
-.set MB_CHECKSUM,	-(MB_MAGIC + MB_FLAGS)		#checksum of above, to prove we are multiboot
-
 .set PG_PRESENT,	1<<0
 .set PG_READ_WRITE,	1<<1
 .set PG_PAGE_SIZE,	1<<7
@@ -15,19 +7,37 @@
 
 .code32
 
-# Multiboot header
+# multiboot2 header
 .section .multiboot, "aw"
-	.align 4
+multiboot2_start:
-	.long MB_MAGIC
+	.align 8
-	.long MB_FLAGS
+	.long 0xE85250D6
-	.long MB_CHECKSUM
-	.skip 20
-
 	.long 0
-	.long 800
+	.long multiboot2_end - multiboot2_start
-	.long 600
+	.long -(0xE85250D6 + (multiboot2_end - multiboot2_start))
+
+	# framebuffer tag
+	.align 8
+	.short 5
+	.short 0
+	.long 20
+	.long 1920
+	.long 1080
 	.long 32
 
+	# legacy start
+	.align 8
+	.short 3
+	.short 0
+	.long 12
+	.long V2P(_start)
+
+	.align 8
+	.short 0
+	.short 0
+	.long 8
+multiboot2_end:
+
 .section .bss, "aw", @nobits
  	# Create stack
 	.global g_boot_stack_bottom
@@ -40,11 +50,11 @@
 	g_kernel_cmdline:
 		.skip 4096
 
-	.global g_multiboot_info
+	.global g_multiboot2_info
-	g_multiboot_info:
+	g_multiboot2_info:
 		.skip 8
-	.global g_multiboot_magic
+	.global g_multiboot2_magic
-	g_multiboot_magic:
+	g_multiboot2_magic:
 		.skip 8
 
 .section .data
@@ -119,19 +129,6 @@ check_requirements:
 .exit:
 	jmp system_halt
 
-copy_kernel_commandline:
-	pushl %esi
-	pushl %edi
-	movl V2P(g_multiboot_info), %esi
-	addl $16, %esi
-	movl (%esi), %esi
-	movl $1024, %ecx
-	movl $V2P(g_kernel_cmdline), %edi
-	rep movsl
-	popl %edi
-	popl %esi
-	ret
-
 enable_sse:
 	movl %cr0, %eax
 	andw $0xFFFB, %ax
@@ -170,10 +167,9 @@ initialize_paging:
 _start:
 	# Initialize stack and multiboot info
 	movl $V2P(g_boot_stack_top), %esp
-	movl %eax, V2P(g_multiboot_magic)
+	movl %eax, V2P(g_multiboot2_magic)
-	movl %ebx, V2P(g_multiboot_info)
+	movl %ebx, V2P(g_multiboot2_info)
 
-	call copy_kernel_commandline
 	call check_requirements
 	call enable_sse
 
@@ -201,7 +197,7 @@ long_mode:
 	jmp *%rcx
 
 higher_half:
-	addq $KERNEL_OFFSET, g_multiboot_info
+	addq $KERNEL_OFFSET, g_multiboot2_info
 
 	# call global constuctors
 	call _init

kernel/include/kernel/multiboot.h

@@ -1,57 +0,0 @@
-#pragma once
-
-#include <stdint.h>
-
-#define MULTIBOOT_FLAGS_FRAMEBUFFER (1 << 12)
-
-#define MULTIBOOT_FRAMEBUFFER_TYPE_GRAPHICS 1
-#define MULTIBOOT_FRAMEBUFFER_TYPE_TEXT 2
-
-struct framebuffer_info_t
-{
-	uint64_t addr;
-	uint32_t pitch;
-	uint32_t width;
-	uint32_t height;
-	uint8_t  bpp;
-	uint8_t  type;
-	uint8_t  color_info[6];
-};
-
-struct multiboot_memory_map_t
-{
-	uint32_t size;
-	uint64_t base_addr;
-	uint64_t length;
-	uint32_t type;
-} __attribute__((packed));
-
-// https://www.gnu.org/software/grub/manual/multiboot/multiboot.html#Boot-information-format
-struct multiboot_info_t
-{
-	uint32_t flags;
-	uint32_t mem_lower;
-	uint32_t mem_upper;
-	uint32_t boot_device;
-	uint32_t cmdline;
-	uint32_t mods_count;
-	uint32_t mods_addr;
-	uint32_t syms[4];
-	uint32_t mmap_length;
-	uint32_t mmap_addr;
-	uint32_t drives_length;
-	uint32_t drives_addr;
-	uint32_t config_table;
-	uint32_t boot_loader_name;
-	uint32_t apm_table;
-	uint32_t vbe_control_info;
-	uint32_t vbe_mode_info;
-	uint16_t vbe_mode;
-	uint16_t vbe_interface_seg;
-	uint16_t vbe_interface_off;
-	uint16_t vbe_interface_len;
-	framebuffer_info_t framebuffer;
-};
-
-extern "C" multiboot_info_t*	g_multiboot_info;
-extern "C" uint32_t				g_multiboot_magic;

kernel/include/kernel/multiboot2.h

@@ -0,0 +1,75 @@
+#pragma once
+
+#include <stdint.h>
+
+// https://www.gnu.org/software/grub/manual/multiboot2/multiboot.html#Boot-information
+
+#define MULTIBOOT2_TAG_END			0
+#define MULTIBOOT2_TAG_CMDLINE		1
+#define MULTIBOOT2_TAG_MMAP			6
+#define MULTIBOOT2_TAG_FRAMEBUFFER	8
+#define MULTIBOOT2_TAG_OLD_RSDP		14
+#define MULTIBOOT2_TAG_NEW_RSDP		15
+
+#define MULTIBOOT2_FRAMEBUFFER_TYPE_RGB	1
+
+struct multiboot2_tag_t
+{
+	uint32_t type;
+	uint32_t size;
+	multiboot2_tag_t* next() { return (multiboot2_tag_t*)((uintptr_t)this + ((size + 7) & ~7)); }
+} __attribute__((packed));
+
+struct multiboot2_cmdline_tag_t : public multiboot2_tag_t
+{
+	char cmdline[];
+} __attribute__((packed));
+
+struct multiboot2_mmap_entry_t
+{
+	uint64_t base_addr;
+	uint64_t length;
+	uint32_t type;
+	uint32_t reserved;
+} __attribute__((packed));
+
+struct multiboot2_mmap_tag_t : public multiboot2_tag_t
+{
+	uint32_t entry_size;
+	uint32_t entry_version;
+	multiboot2_mmap_entry_t entries[];
+} __attribute__((packed));
+
+struct multiboot2_framebuffer_tag_t : public multiboot2_tag_t
+{
+	uint64_t framebuffer_addr;
+	uint32_t framebuffer_pitch;
+	uint32_t framebuffer_width;
+	uint32_t framebuffer_height;
+	uint8_t framebuffer_bpp;
+	uint8_t framebuffer_type;
+	uint8_t reserved;
+} __attribute__((packed));
+
+struct multiboot2_rsdp_tag_t : public multiboot2_tag_t
+{
+	uint8_t data[];
+} __attribute__((packed));
+
+struct multiboot2_info_t
+{
+	uint32_t total_size;
+	uint32_t reserved;
+	multiboot2_tag_t tags[];
+} __attribute__((packed));
+
+extern "C" multiboot2_info_t* g_multiboot2_info;
+extern "C" uint32_t g_multiboot2_magic;
+
+inline multiboot2_tag_t* multiboot2_find_tag(uint32_t type)
+{
+	for (auto* tag = g_multiboot2_info->tags; tag->type != MULTIBOOT2_TAG_END; tag = tag->next())
+		if (tag->type == type)
+			return tag;
+	return nullptr;
+}

kernel/kernel/ACPI.cpp

@@ -2,6 +2,7 @@
 #include <BAN/StringView.h>
 #include <kernel/ACPI.h>
 #include <kernel/Memory/PageTable.h>
+#include <kernel/multiboot2.h>
 
 #include <lai/core.h>
 
@@ -84,6 +85,12 @@ namespace Kernel
 
 	static const RSDP* locate_rsdp()
 	{
+		// Check the multiboot headers
+		if (auto* rsdp_new = (multiboot2_rsdp_tag_t*)multiboot2_find_tag(MULTIBOOT2_TAG_NEW_RSDP))
+			return (const RSDP*)rsdp_new->data;
+		if (auto* rsdp_old = (multiboot2_rsdp_tag_t*)multiboot2_find_tag(MULTIBOOT2_TAG_OLD_RSDP))
+			return (const RSDP*)rsdp_old->data;
+
 		// Look in main BIOS area below 1 MB
 		for (uintptr_t addr = P2V(0x000E0000); addr < P2V(0x000FFFFF); addr += 16)
 			if (is_rsdp(addr))

kernel/kernel/Memory/Heap.cpp

@@ -1,7 +1,7 @@
 #include <kernel/LockGuard.h>
 #include <kernel/Memory/Heap.h>
 #include <kernel/Memory/PageTable.h>
-#include <kernel/multiboot.h>
+#include <kernel/multiboot2.h>
 
 extern uint8_t g_kernel_end[];
 
@@ -26,21 +26,23 @@ namespace Kernel
 
 	void Heap::initialize_impl()
 	{
-		if (!(g_multiboot_info->flags & (1 << 6)))
+		auto* mmap_tag = (multiboot2_mmap_tag_t*)multiboot2_find_tag(MULTIBOOT2_TAG_MMAP);
+		if (mmap_tag == nullptr)
 			Kernel::panic("Bootloader did not provide a memory map");
 
-		for (size_t i = 0; i < g_multiboot_info->mmap_length;)
+		for (size_t offset = sizeof(*mmap_tag); offset < mmap_tag->size; offset += mmap_tag->entry_size)
 		{
-			multiboot_memory_map_t* mmmt = (multiboot_memory_map_t*)P2V(g_multiboot_info->mmap_addr + i);
+			auto* mmap_entry = (multiboot2_mmap_entry_t*)((uintptr_t)mmap_tag + offset);
-			if (mmmt->type == 1)
+
+			if (mmap_entry->type == 1)
 			{				
-				paddr_t start = mmmt->base_addr;
+				paddr_t start = mmap_entry->base_addr;
 				if (start < V2P(g_kernel_end))
 					start = V2P(g_kernel_end);
 				if (auto rem = start % PAGE_SIZE)
 					start += PAGE_SIZE - rem;
 
-				paddr_t end = mmmt->base_addr + mmmt->length;
+				paddr_t end = mmap_entry->base_addr + mmap_entry->length;
 				if (auto rem = end % PAGE_SIZE)
 					end -= rem;
 
@@ -48,7 +50,6 @@ namespace Kernel
 				if (end > start + PAGE_SIZE)
 					MUST(m_physical_ranges.emplace_back(start, end - start));
 			}
-			i += mmmt->size + sizeof(uint32_t);
 		}
 
 		size_t total = 0;

kernel/kernel/Terminal/VesaTerminalDriver.cpp

@@ -1,55 +1,54 @@
 #include <BAN/Errors.h>
 #include <kernel/Debug.h>
 #include <kernel/Memory/PageTable.h>
-#include <kernel/multiboot.h>
+#include <kernel/multiboot2.h>
 #include <kernel/Terminal/VesaTerminalDriver.h>
 
 using namespace Kernel;
 
 VesaTerminalDriver* VesaTerminalDriver::create()
 {
-	if (!(g_multiboot_info->flags & MULTIBOOT_FLAGS_FRAMEBUFFER))
+	auto* framebuffer_tag = (multiboot2_framebuffer_tag_t*)multiboot2_find_tag(MULTIBOOT2_TAG_FRAMEBUFFER);
+	if (framebuffer_tag == nullptr)	
 	{
 		dprintln("Bootloader did not provide framebuffer");
 		return nullptr;
 	}
 
-	auto& framebuffer = g_multiboot_info->framebuffer;
+	if (framebuffer_tag->framebuffer_type != MULTIBOOT2_FRAMEBUFFER_TYPE_RGB)
-
-	if (framebuffer.type == MULTIBOOT_FRAMEBUFFER_TYPE_GRAPHICS)
 	{
-		if (framebuffer.bpp != 24 && framebuffer.bpp != 32)
+		dprintln("unsupported framebuffer type {}", framebuffer_tag->framebuffer_type);
-		{
-			dprintln("Unsupported bpp {}", framebuffer.bpp);
-			return nullptr;
-		}
-		dprintln("Graphics Mode {}x{} ({} bpp)", framebuffer.width, framebuffer.height, framebuffer.bpp);
-	}
-	else if (framebuffer.type == MULTIBOOT_FRAMEBUFFER_TYPE_TEXT)
-	{
-		dprintln("Text Mode is currently not supported");
-		return nullptr;
-	}
-	else
-	{
-		dprintln("Unknown framebuffer type {}", framebuffer.type);
 		return nullptr;
 	}
 
-	uint64_t first_page = framebuffer.addr / PAGE_SIZE;
+	if (framebuffer_tag->framebuffer_bpp != 24 && framebuffer_tag->framebuffer_bpp != 32)
-	uint64_t last_page = BAN::Math::div_round_up<uint64_t>(framebuffer.addr + framebuffer.pitch * framebuffer.height, PAGE_SIZE);
+	{
-	uint64_t needed_pages = last_page - first_page + 1;
+		dprintln("Unsupported bpp {}", framebuffer_tag->framebuffer_bpp);
+		return nullptr;
+	}
+
+	dprintln("Graphics Mode {}x{} ({} bpp)",
+		(uint32_t)framebuffer_tag->framebuffer_width,
+		(uint32_t)framebuffer_tag->framebuffer_height,
+		(uint8_t)framebuffer_tag->framebuffer_bpp
+	);
+
+	paddr_t paddr = framebuffer_tag->framebuffer_addr & PAGE_ADDR_MASK;
+	size_t needed_pages = range_page_count(
+		framebuffer_tag->framebuffer_addr,
+		framebuffer_tag->framebuffer_pitch * framebuffer_tag->framebuffer_height
+	);
 
 	vaddr_t vaddr = PageTable::kernel().reserve_free_contiguous_pages(needed_pages, KERNEL_OFFSET);
 	ASSERT(vaddr);
 
-	PageTable::kernel().map_range_at(framebuffer.addr, vaddr, needed_pages * PAGE_SIZE, PageTable::Flags::UserSupervisor | PageTable::Flags::ReadWrite | PageTable::Flags::Present);
+	PageTable::kernel().map_range_at(paddr, vaddr, needed_pages * PAGE_SIZE, PageTable::Flags::UserSupervisor | PageTable::Flags::ReadWrite | PageTable::Flags::Present);
 
 	auto* driver = new VesaTerminalDriver(
-		framebuffer.width,
+		framebuffer_tag->framebuffer_width,
-		framebuffer.height,
+		framebuffer_tag->framebuffer_height,
-		framebuffer.pitch,
+		framebuffer_tag->framebuffer_pitch,
-		framebuffer.bpp,
+		framebuffer_tag->framebuffer_bpp,
 		vaddr
 	);
 	driver->set_cursor_position(0, 0);

kernel/kernel/kernel.cpp

@@ -12,7 +12,7 @@
 #include <kernel/Memory/Heap.h>
 #include <kernel/Memory/kmalloc.h>
 #include <kernel/Memory/PageTable.h>
-#include <kernel/multiboot.h>
+#include <kernel/multiboot2.h>
 #include <kernel/PCI.h>
 #include <kernel/PIC.h>
 #include <kernel/Process.h>
@@ -23,8 +23,6 @@
 #include <kernel/Terminal/VesaTerminalDriver.h>
 #include <kernel/Timer/Timer.h>
 
-extern "C" const char g_kernel_cmdline[];
-
 struct ParsedCommandLine
 {
 	bool force_pic		= false;
@@ -35,11 +33,12 @@ struct ParsedCommandLine
 
 static bool should_disable_serial()
 {
-	if (!(g_multiboot_info->flags & 0x02))
+	auto* cmdline_tag = (multiboot2_cmdline_tag_t*)multiboot2_find_tag(MULTIBOOT2_TAG_CMDLINE);
+	if (cmdline_tag == nullptr)
 		return false;
 
-	const char* start = g_kernel_cmdline;
+	const char* start = cmdline_tag->cmdline;
-	const char* current = g_kernel_cmdline;
+	const char* current = start;
 	while (true)
 	{
 		if (!*current || *current == ' ' || *current == '\t')
@@ -60,10 +59,11 @@ static ParsedCommandLine cmdline;
 
 static void parse_command_line()
 {
-	if (!(g_multiboot_info->flags & 0x02))
+	auto* cmdline_tag = (multiboot2_cmdline_tag_t*)multiboot2_find_tag(MULTIBOOT2_TAG_CMDLINE);
+	if (cmdline_tag == nullptr)
 		return;
 
-	BAN::StringView full_command_line(g_kernel_cmdline);
+	BAN::StringView full_command_line(cmdline_tag->cmdline);
 	auto arguments = MUST(full_command_line.split(' '));
 
 	for (auto argument : arguments)
@@ -98,7 +98,7 @@ extern "C" void kernel_main()
 		dprintln("Serial output initialized");
 	}
 
-	if (g_multiboot_magic != 0x2BADB002)
+	if (g_multiboot2_magic != 0x36d76289)
 	{
 		dprintln("Invalid multiboot magic number");
 		return;

toolchain/local/grub-legacy-boot.cfg

@@ -1,23 +1,23 @@
 menuentry "banan-os" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2
 }
 
 menuentry "banan-os (no serial)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 noserial
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 noserial
 }
 
 menuentry "banan-os (only serial)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 console=ttyS0
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 console=ttyS0
 }
 
 menuentry "banan-os (no apic)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 noapic
 }
 
 menuentry "banan-os (no apic, no serial)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic noserial
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 noapic noserial
 }
 
 menuentry "banan-os (no apic, only serial)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic console=ttyS0
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 noapic console=ttyS0
 }

toolchain/local/grub-uefi.cfg

@@ -2,25 +2,25 @@ insmod part_gpt
 set root=(hd0,gpt2)
 
 menuentry "banan-os" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2
 }
 
 menuentry "banan-os (no serial)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 noserial
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 noserial
 }
 
 menuentry "banan-os (only serial)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 console=ttyS0
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 console=ttyS0
 }
 
 menuentry "banan-os (no apic)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 noapic
 }
 
 menuentry "banan-os (no apic, no serial)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic noserial
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 noapic noserial
 }
 
 menuentry "banan-os (no apic, only serial)" {
-	multiboot /boot/banan-os.kernel root=/dev/sda2 noapic console=ttyS0
+	multiboot2 /boot/banan-os.kernel root=/dev/sda2 noapic console=ttyS0
 }