error: no multiboot header found - bare-metal

Question

This day found something that caught my attention. is build a simple bare OS
i read how to make multiboot compliant, I'm using NASM and GCC, i need make a loader that has the multiboot header and call the main point of my system for that i have two files loader.asm and loader.ld
loader.asm
[BITS 32]
global start
start:
mov esp, _sys_stack
jmp stublet
ALIGN 4
mboot:
MBOOT_PAGE_ALIGN equ 1<<0
MBOOT_MEMORY_INFO equ 1<<1
MBOOT_HEADER_MAGIC equ 0x1BADB002
MBOOT_HEADER_FLAGS equ MBOOT_PAGE_ALIGN | MBOOT_MEMORY_INFO
MBOOT_CHECKSUM equ -(MBOOT_HEADER_MAGIC + MBOOT_HEADER_FLAGS)
; This is the GRUB Multiboot header. A boot signature
dd MBOOT_HEADER_MAGIC
dd MBOOT_HEADER_FLAGS
dd MBOOT_CHECKSUM
stublet:
EXTERN cmain
call cmain
jmp $
SECTION .bss
resb 8192
_sys_stack:
loader.ld
ENTRY(start)
phys = 0x00100000;
SECTIONS
{
.text phys : AT(phys) {
code = .;
*(.text)
*(.rodata)
. = ALIGN(4096);
}
.data : AT(phys + (data - code))
{
data = .;
*(.data)
. = ALIGN(4096);
}
.bss : AT(phys + (bss - code))
{
bss = .;
*(.bss)
. = ALIGN(4096);
}
end = .;
}
main.c
int GenyKernel_Main()
{
char *str = "Hello world!", *ch;
unsigned short *vidmem = (unsigned short*) VIDEO_MEMORY;
unsigned i;
for (ch = str, i = 0; *ch; ch++, i++) {
vidmem[i] = (unsigned char) *ch | 0x0700;
}
return 0;
}
for build i'm using
# loader.o
nasm -f elf64 -o loader.o loader.asm
# main.o
gcc -fno-stack-protector -fno-builtin -nostdinc -O -g -Wall -I. -c -o main.o main.c
and the finally link
ld -T loader.ld -o kernel loader.o main.o
I've built a simple iso with grub-mkrescue and run with qemu but always I get
I think the problem is in the file loader.ld but i can't found where

Answer 1

After read lots about the same .asm file i finally understood the problem, the following snippet
align 4
multiboot_header:
dd MBOOT_MAGIC
dd MBOOT_FLAGS
dd MBOOT_CHECKSUM
must exist below a section to include appropriately with the linker
section .text ; .multiboot o whatever
align 4
multiboot_header:
dd MBOOT_MAGIC
dd MBOOT_FLAGS
dd MBOOT_CHECKSUM
and in the linker script
ENTRY(your_entry_point)
SECTIONS
{
. = 0x00100000;
.text ALIGN(0x1000) :
{
*(.multiboot)
*(.text)
}
// rest of sections
}