grub does nothing after "multiboot /boot/kernel.bin"

Question

Im trying to boot custom kernel with help of grub and qemu.

If i start it with "qemu -kernel -m 64 ./kernel.bin" it works fine.

Bud if i create iso with "grub-mkrescue -o os.iso ./os/"

It start to load grub and screen stay black

directories tree:

------
./os/boot/
    kernel.bin
    grub/
        grub.cfg

------

content of grub.cfg

set default="0"
set timeout="3"

    ### BEGIN 10 ###
    menuentry "tmx.os" {


        multiboot /boot/kernel.bin
        echo " LOADING KERNEL: done"
    }

    ### END 10 ###

the line "LOADING KERNEL: done" is displayed on the screen.

Have somebody idea what can be wrong ? Any advise is welcome

======================================================= UPD: i have kernel_main() in "C" file, and as i can see in GDB kernel_main gets never called. Strange ?

assembly code 

bits    32

section .text
    align   4                       ; align at 4 byte
    dd      0x1BADB002              ; MAGIC
    dd      0x00
    dd      - (0x1BADB002 + 0x00)

global start
extern kernel_main

start:

    cli                     ; Clear interrupt flag [IF = 0]; 0xFA
    mov esp, kernel_stack   ; set stack pointer
    ;push eax               ; multiboot structure
    ;push ebx               ; MAGIC
    call kernel_main        ; controll to kernel_main(); in kernelc.c 
    hlt                     ; HLT   Enter halt state 0xF4

end:
    cli
    hlt
    jmp end

section .bss
    resb 1024*256           ; *Kb for stack

kernel_stack:           ; <= stack_space

I cant understand, what happens to "call kernel_main" instruction ?

this is "kernel.c", there is like nothing, just clear vid.mem. buffer

#include "kernel.h" // <<< extern void kernel_main();
void kernel_main() {

    char * BUFF = (char*) 0xb8000;

    int i=0;
    int ii=0;

    while ( i < 80*25) {
        BUFF[ ii++ ] = '#';
        BUFF[ ii++ ] = 0x7;
        i++;
    }

}

also "grub-file --is-x86-multiboot kernel.bin" is "multiboot confirmed"

[SOLVED] I do not know how it cat be, bud it works now. Its MAGIC | 0x1BADB002

I wrote kernel is AT&T syntax, sub could not implement all things i need. GDT, and IDT keeps crashing, so i test one more time with kernel.s [NASM]

And MAGIC, it works now. Yeeeeeeeeeeyyy :p