Multiboot2 bootloader not passing the elf sections tag

[forgetme11]

making me unable to remap the kernel's code and data in the new pagetable.
I found this "SORT_BY_NAME" modifier for ld

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        .text BLOCK(4K) : ALIGN(4K)
        {
                SORT_BY_NAME*(.00000multiboot)
                SORT_BY_NAME*(.text)
                SORT_BY_NAME*(.ZZZZZTEXT_END_ADDRESS)   # Needed because GRUB does not pass the elf headers tag.
        }

but it does not behave as expected (cant even load the multiboot header, though in ld's sections map (-M option) it shows up as the first section in .text, ZZZZZ... is confirmed to not work though)

Ideas?

[MichaelPetch]

I'm not sure I understand the problem or what this solution you show is trying to fix. Part of me feels like this is an XY problem. Do you have a repository of your code online somewhere where we can see your project, code make files/build scripts etc so we can try to reproduce what the problem is?

[forgetme11]

This is the function where I am having trouble, grub only ever gives me one tag (no clue which one it is since gdb cant access the memory in the virtual machine) but it is not the efi symbols one (which is needed for me to remap the kernel's code and data in the new pagetable), apic_INIT_sipi() (supposedly) is what causes a bootloop (intended behaviour) on -enable-kvm but doesn't work in the emulator (made a thread about that)

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static void kernel_configure_memory(generic_memory_map_t* absmap, mb_elf_symbols_t* mb_section_headers){
	mb_elf_section_info_t ported_sections[5] = {0};
	char* section_names[] = {".text",".rodata",".bss",".data"};
	void* physical_memory_management_array = NULL;

	reposition_memory_map(absmap);

	_memory_manager_.amount = get_memory_size(absmap);
	physical_memory_management_array = boot_alloc(absmap,_memory_manager_.amount/8);

	if (elf_symbols == 0){
		outb(0x80,BOOTERR_BOOTLOADER_LEFT_UNBOOTABLE);
		apic_INIT_sipi();
	}else{
		elf_get_section_info_by_name(section_names[0],&ported_sections[0],(mb_elf_section_header_table_header_t*)mb_section_headers);
		elf_get_section_info_by_name(section_names[1],&ported_sections[1],(mb_elf_section_header_table_header_t*)mb_section_headers);
		elf_get_section_info_by_name(section_names[2],&ported_sections[2],(mb_elf_section_header_table_header_t*)mb_section_headers);
		elf_get_section_info_by_name(section_names[3],&ported_sections[3],(mb_elf_section_header_table_header_t*)mb_section_headers);
	}

	ported_sections[4].physaddr = physical_memory_management_array;
	ported_sections[4].size = _memory_manager_.amount/8;

	fill_memory_manager(absmap);

	x64_desc_table_pointer_t desctab_whore_pointer = {0};
	desctab_whore_pointer.address = &bsp_tmp_gdt;

	lgdt(&desctab_whore_pointer);
	desctab_whore_pointer.address = &interrupt_descriptor_table;
	lidt(&desctab_whore_pointer);

	if (_memory_manager_.amount > (1<<(4*9))/2){
		_mmu_.pagetree_levels = 5;
	}else{	_mmu_.pagetree_levels = 4;}

	pagetable_t* ghosttree = boot_alloc(absmap,4096);

	boot_identity_map(ghosttree,ported_sections[0].physaddr,ported_sections[0].size,DEFAULT_CACHE);
	boot_identity_map(ghosttree,ported_sections[1].physaddr,ported_sections[1].size,DEFAULT_CACHE);
	boot_identity_map(ghosttree,ported_sections[2].physaddr,ported_sections[2].size,DEFAULT_CACHE);
	boot_identity_map(ghosttree,ported_sections[3].physaddr,ported_sections[3].size,DEFAULT_CACHE);
	boot_identity_map(ghosttree,ported_sections[4].physaddr,ported_sections[4].size,DEFAULT_CACHE);
	boot_identity_map(ghosttree,get_local_apic(),4096,CACHE_MMIO);

	__asm__ volatile(
	".p2align 6		\n\t"	/* Telling the assembler to align the code to 2^6 bytes */
	"mov	%%cr3,%%rax	\n\t"
	"or	%0,%%rax	\n\t"
	"mov	%%rax,%%cr3	\n\t"	/* Not serializing until cr4 has been dealt with */
	"mov	%%cr4,%%rax	\n\t"	/* Setting the pagetree to 4 levels */
	"and	%1,%%rax	\n\t"
	"mov	%%rax,%%cr4	\n\t"
	"jmp	0		\n\t"
	::"r"((uint64_t)ghosttree),"r"(UINT64_MAX^(_mmu_.pagetree_levels==4?1<<12:0)):"%rax");

	_KERNELSPACE_.address_space.pagetree = ghosttree;

	_memory_manager_.pointer = physical_memory_management_array;
}

Though I don't really care anymore, I am going to make a small bootloader in a windows iso, I don't want to hear "multiboot" ever again in my life, we are like monkeys to grub developers, the spelling errors in the "Standard" should have been enough of a warning, alas here we are.

I don't have a repository on the web

edit: talk about spelling mistakes

[Octocontrabass]

(no clue which one it is since gdb cant access the memory in the virtual machine)

How are you attaching GDB to your virtual machine?

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	"mov	%%cr4,%%rax	\n\t"	/* Setting the pagetree to 4 levels */

You can't switch between 4-level and 5-level paging while paging is enabled.

I am going to make a small bootloader in a windows iso

Maybe Limine is closer to what you want? It'll save you the trouble of writing a bootloader.

[iansjack]

Are you sure that you are not making the same mistake that you did with the magic number when interpreting multi-byte values?

I don’t understand what your problem with gdb is - it would be pretty useless if it couldn’t access virtual addresses. But, if you use qemu it has a built-in monitor which can provide a load of information. Use it to inspect a range of memory as bytes, words, integers, and longs to be sure that you understand how memory layout works.

Multiboot really isn’t as difficult as you think. If it was it would never have become so popular.

A public repository is highly recommended if you want to ask others for help. People invariably post the wrong section of code when asking for help with errors.