Fedora 41 : assembly fasm with cat command and qemu test.

I tested the basic direct binary concatenation where the second file is appended to the end of the first file, preserving all bytes exactly as they are without any linking metadata or relocations with the cat command.

Let's see how can do this.

You need to create two files: kernel.fasm and kernel2.fasm.

First will like this:

org 7C00h

; First stage bootloader
start:
    mov [bootdrive], dl
    mov ax, 0x2000  ; Load kernel at 0x2000:0
    mov es, ax
    xor bx, bx      ; ES:BX = buffer
    
    mov ah, 02h     ; Read sectors
    mov al, 6       ; Number of sectors to read
    mov ch, 0       ; Cylinder 0
    mov cl, 2       ; Start from sector 2
    mov dh, 0       ; Head 0
    mov dl, [bootdrive]
    int 13h
    
    jmp 0x2000:0    ; Jump to second stage

bootdrive db 0
times 510-($-$$) db 0
dw 0xAA55

The second one named kernel2.fasm will come with new features:

org 0

COLS equ 80
ROWS equ 25
VIDEO_MEM equ 0xB800

; Box drawing characters
BOX_DR    equ 201  ; ╔
BOX_HL    equ 205  ; ═
BOX_DL    equ 187  ; ╗
BOX_VL    equ 186  ; ║
BOX_UR    equ 200  ; ╚
BOX_UL    equ 188  ; ╝
BOX_BLOCK equ 219  ; █
...

Use fasm and cat commands to create the bin files and the result file for qemu:

mythcat@localhost:~/fasm$ ./fasm.x64 kernel.fasm kernel.bin
flat assembler  version 1.73.32  (16384 kilobytes memory, x64)
2 passes, 512 bytes.
mythcat@localhost:~/fasm$ ./fasm.x64 kernel2.fasm kernel2.bin
flat assembler  version 1.73.32  (16384 kilobytes memory, x64)
2 passes, 132 bytes.
mythcat@localhost:~/fasm$ cat kernel.bin kernel2.bin > os.img

The last step is to run qemu-system-i386 to test the result

mythcat@localhost:~/fasm$ qemu-system-i386 -fda os.img

The result is this:

Fedora 34 : Testing the new Fedora 34 beta.

Approaching the release date for Fedora Linux 34, the development team has included a number of testing steps.

For each test stage, some events were set up in which users participate and test the new Fedora distribution. Here are these see events.

Here is a screenshot with the virtualization test step for the ISO file called Fedora 34: x86_64 DVD ISO Beta! from the official page:

Fedora 28 : ARM programming and testing .

This is a simple tutorial about ARM programming and QEMU:
The test.c program is this :

volatile unsigned int * const UART0DR = (unsigned int *)0x101f1000;
 
void print_uart0(const char *s) {
 while(*s != '\0') { /* Loop until end of string */
 *UART0DR = (unsigned int)(*s); /* Transmit char */
 s++; /* Next char */
 }
}
 
void c_entry() {
 print_uart0("Hello world!\n");
}

Using volatile keyword is necessary to instruct the compiler that the memory pointed.
The unsigned int type enforces 32-bits read and write access.
The QEMU model like in a real system on chip the Transmit FIFO Full flag must be checked in the UARTFR register before writing on the UARTDR register.
Create the startup.s assembler file:

.global _Reset
_Reset:
 LDR sp, =stack_top
 BL c_entry
 B .

Create the script linker named test.ld:

ENTRY(_Reset)
SECTIONS
{
 . = 0x10000;
 .startup . : { startup.o(.text) }
 .text : { *(.text) }
 .data : { *(.data) }
 .bss : { *(.bss COMMON) }
 . = ALIGN(8);
 . = . + 0x1000; /* 4kB of stack memory */
 stack_top = .;
}

Next step is the install of arm-none-eabi x86_64 tools :

[root@desk arm-source]# dnf install arm-none-eabi-gcc-cs-c++.x86_64 
Last metadata expiration check: 1:54:04 ago on Fri 15 Jun 2018 06:55:54 PM EEST.
Package arm-none-eabi-gcc-cs-c++-1:7.1.0-5.fc27.x86_64 is already installed, skipping.
Dependencies resolved.
Nothing to do.
Complete!
[root@desk arm-source]# dnf install arm-none-eabi-gdb.x86_64 
Last metadata expiration check: 1:54:48 ago on Fri 15 Jun 2018 06:55:54 PM EEST.
Package arm-none-eabi-gdb-7.6.2-4.fc24.x86_64 is already installed, skipping.
Dependencies resolved.
Nothing to do.
Complete!
[mythcat@desk arm-source]$ ll
total 12
-rw-rw-r--. 1 mythcat mythcat  60 Jun 15 20:28 startup.s
-rw-rw-r--. 1 mythcat mythcat 288 Jun 15 20:26 test.c
-rw-rw-r--. 1 mythcat mythcat 223 Jun 15 20:29 test.ld

Let's test this with qemu virtual tool ( use Ctr+A and X keys to stop qemu) :

[mythcat@desk arm-source]$ qemu-system-arm -M versatilepb -m 64M -nographic -kernel test.bin
pulseaudio: set_sink_input_volume() failed
pulseaudio: Reason: Invalid argument
pulseaudio: set_sink_input_mute() failed
pulseaudio: Reason: Invalid argument
Hello world!
QEMU: Terminated

QEMU - Devil Linux on Fedora 25.

QEMU (short for Quick Emulator) is a free and open-source hosted hypervisor that performs hardware virtualization QEMU is a hosted virtual machine monitor. You can install this software using dnf tool.

dnf install qemu.x86_64 

You can use any iso image from internet to run and test your distro linux. Just use this command:
I tested with Devil Linux iso without network ( the main reason was the settings of Devil Linux distro).

qemu-system-x86_64 -boot d -cdrom ~/devil-linux-1.8.0-rc2-x86_64/bootcd.iso --enable-kvm -m 2048
 -netdev user,id=user.0

Some args of qemu tool:
- qemu-system-x86_64 is the option for x86 architecture (64 bit);
- boot and -d set options for booting and debug;
- the -cdrom option set the iso file path and file;
- the --enable-kvm enable Kernel Virtual Machine;
- the -m 2048 set memory;
- the -netdev user,id=user.0 that tells us about qemu to use the user mode network stack which requires no administrator privilege to run;  
About QEMU VLAN.
QEMU networking uses a networking technology that is like VLAN. The QEMU forward packets to guest operating systems that are on the same VLAN. Examples with qemu-kvm options:

-net nic,model=virtio,vlan=0,macaddr=00:16:3e:00:01:01 
-net tap,vlan=0,script=/root/ifup-br0,downscript=/root/ifdown-br0 
-net nic,model=virtio,vlan=1,macaddr=00:16:3e:00:01:02 
-net tap,vlan=1,script=/root/ifup-br1,downscript=/root/ifdown-br1

- net nic command defines a network adapter in the guest operating system. - net tap command defines how QEMU configures the host. You can disabling networking entirely:

-net none