1,894 questions
3
votes
2
answers
97
views
Why Bits declare instruction in nasm x86 assembly languages have no effect When I write code to use big unreal mode?
I am a beginner in x86 assembly language. I heard that Bios have a technology called big mode for executing or accessing other BIOS code or data in the range exceeding 64KB and far beyond the 0-1M ...
- 33
1
vote
0
answers
81
views
x64 Bootloader with C-Kernel
I'm currently working on an x64 Bootloader for a school project, but can't get it to run my Kernel.
Bootloader.asm
;###################################
; Real Mode
;##########################...
- 1
0
votes
0
answers
88
views
Floppy disk read from stage 2 bootloader is failing consistently
Maybe this question has already been answered before, but I couldn't find one with my exact issue.
I am consistently running into issues when trying to read my kernel from my stage2 bootloader which ...
- 740
Advice
1
vote
1
replies
68
views
How does UEFI pass RAM information from bootloader (like GRUB) to different operating systems?
I have a question regarding the UEFI boot process and how it handles memory information:
UEFI reads the Serial Presence Detect (SPD) data from RAM chips and "knows" the available physical ...
- 465
3
votes
1
answer
109
views
NASM bootloader: Protected mode jump to kernel at 0x00010000 shows nothing in VirtualBox
I’m writing a small text‑based operating system in NASM to learn how bootloaders, protected mode and kernels work. The system is called AtomOS and the kernel is called the Nucleus.
My problem is that ...
- 33
2
votes
1
answer
145
views
Should I redefine GDT in the kernel if I already did in the bootloader
I have a simple bootloader where I have GDT and switch to protected mode Now I want just to play and experiment with interruptions my initial idea was to do everything in bootloader but at the end it ...
- 129
5
votes
0
answers
161
views
how to get IDT handler address in assembly
I am experiencing with OS programming I wrote a simple bootloader in assembly and I switched to protected mode. I want just to test interruption (keyboard) I did not want to do it with C but just in ...
- 129
2
votes
0
answers
136
views
x86 long mode setup issue
I am currently trying to make the second stage of a bootloader in order to enable 64 bit long mode. I have written some x86 assembly for the NASM assembler to do so, but when I compiled and ran the ...
0
votes
0
answers
71
views
Bootloader stopped working after I changed the syntax from gas to nasm
I have this bootloader I made a while ago and I would like it to be in nasm:
.intel_syntax noprefix
.code16
.equ STACK_TOP, 0x7C00
.equ SELF_LOAD, 0x7C00
.equ ELF_HDR_LOAD, 0x7E00
.equ SECT_SIZE, ...
2
votes
1
answer
101
views
Assembly code fail when I add a jump before rept
I have the following assembled but when ever I uncomment the jmp or je it fail with 11: Error: bad or irreducible absolute expression
_start:
mov $0x0e, %ah
mov $'a', %al
_loop:
int $...
- 129
Advice
0
votes
0
replies
58
views
Understanding of the early stages in boot on STM32MP157F
I applied the ST FWU reference solution on our own platform based on the STM32MP157F.
I have a few questions to clarify the default behavior:
What is the default behavior in the early boot stage? Do ...
- 330
2
votes
2
answers
147
views
Printing to VGA in protected mode crashes system
As you can see down at bottom on my stage 2 boot loader, I have a VGA write thing (Prints out "Starting kernel...", but when I use it, the system starts to boot loop, I have no idea why this ...
5
votes
1
answer
120
views
Bootloader crashing when jumping to 0x100000
I am having a problem with a bootloader I made. Mostly used code snippets from wiki.osdev.org, and screeck (on Github and Youtube) . The issue is: the bootloader cannot jump farther than 0xFFFFF, and ...
- 53
3
votes
2
answers
149
views
How can I correctly load the kernel to its canonical high address space
I am working on a small os with a custom boot loader targeting BIOS. For this, I need to map the kernel to its canonical high address space (0xFFFFFFFF80000000) and jump to its entry point.
For this, ...
- 133
3
votes
1
answer
135
views
nasm bios int 13h read sector issue [duplicate]
im trying to make a simple bootloader that loads a simple kernel and the problem is that the kernel code doesnt run i do see prints from the bootloader but not from the kernel here is my code:
boot....
- 61