Questions tagged [bootloader]
Bootloader is a program that loads the operating system into the computer's memory and set it into execution. When a computer is powered-up or restarted, the basic input/output system (BIOS) performs some initial tests, and then transfers control to the Bootloader.
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How to run a program without an operating system?
How do you run a program all by itself without an operating system running?
Can you create assembly programs that the computer can load and run at startup, e.g. boot the computer from a flash drive ...
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What is the booting process for ARM?
As we know, for X86 architecture: After we press the power button, machine starts to execute code at 0xFFFFFFF0, then it starts to execute code in BIOS in order to do hardware initialization. After ...
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Why does the general program usually start at 0x8000?
I am not new to bootloader and system SW, but I don't know the origin of the reason why the general program starts at 0x8000. I already know the address 0x8000 has been used as start address in normal ...
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What is the difference between a Bootrom vs bootloader on ARM systems
I primarily come from an x86 system background where BIOS (Firmware) is responsible for loading a bootloader (like GRUB) from PowerON which in turn loads the OS. I now have been reading the equivalent ...
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Arduino Bootloader
Can someone please explain how the Arduino bootloader works? I'm not looking for a high level answer here, I've read the code and I get the gist of it.
There's a bunch of protocol interaction that ...
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bootloader - switching processor to protected mode
I'm having difficulties understanding how a simple boot loader works. The boot loader I'm talking about is the one from MITs course "Operating Systems Engineering".
First, let me show you a piece of ...
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Why do we need a bootloader in an embedded device?
I'm working with ELinux kernel on ARM cortex-A8.
I know how the bootloader works and what job it's doing. But i've got a question - why do we need bootloader, why was the bootloader born?
Why we ...
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How does UEFI work?
I was studying about bootloaders when exactly came upon the term UEFI. I can understand some things about UEFI. But still, In what mode(Real,Protected,Long) does a system with UEFI start? If normal ...
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Bootloader in C won't compile
I am a newbie in writing bootloaders. I have written a helloworld bootloader in asm, and
I am now trying to write one in C. I have written a helloworld bootloader in C, but I cannot compile it.
This ...
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What is significance of memory at 0000:7c00 to booting sequence?
Why does bios read at partition's boot record at 0000:7c00 ? What is special about that address ? what ':' doing in referencing an address ?
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Bootloader in C/C++?
Is it possible to create a bootloader in C or C++ without using some type of Assembler (and preferably without using __asm)? I'm writing an Operating System and would like it to be completely written ...
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To write a bootloader in C or C++?
I am writing a program, more specifically a bootloader, for an embedded system. I am going to use a C library to interact with some of the hardware components and I have the choice of writing it ...
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x86 NASM 'org' directive meaning
I am following this tutorial as a first foray into bootloader/OS development for x86 using NASM:
http://joelgompert.com/OS/TableOfContents.htm
And I'm on Lesson 4, which is making my bootloader ...
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Legacy BIOS bootloader to bootstrap real-mode code in second stage
I am working on writing my own operating system. So far, my code exceeds 512 bytes, which is too large to fit in a simple boot sector.
I understand that I now have to write a bootloader that reads ...
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Boot loader doesn't jump to kernel code
I'm writing small operation system - for practice. I started with bootloader. I want to create small command system that runs in 16 bit real mode (for now).
I've created bootloader that resets drive, ...
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Is there any documentation about how Minix 3.2 (latest) boot?
I found this site: http://www.os-forum.com/minix/boot/
which claims to document the boot sequence of Minix.
But in the source tree of Minix 3.2 I just get from Git, the files described in the above ...
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How does Raspberry Pi's boot loader work?
Recently I started to study about Embedded System and Embedded Linux. I know that in an embedded system, the operating system is stored on Flash or ROM. When it's turned on, the bootloader loads the ...
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Debugging bootloader with gdb in qemu
There seems to be a problem with the Freedos bootloader. (It appears that the bootcode can't find the kernel in certain circumstances.)
So I'm trying to debug the bootloader in qemu with gdb. ...
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ADB Fastboot error when flasing rom 'FAILED remote unknown command'
I'm trying to flash Google factory image file on nexus 6P but it always stops at the same point. USB debugging is enabled, MTP mode also. Bootloader is unlocked and communicating with ADB Fastboot etc,...
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Difference between bootloader and bootstrap loader?
how boot loader is different from bootstrap loader. According to me bootstrap loaders are stored in ROM and boot loaders are in hard disk in MBR (please correct me if I am wrong). bootstrap loader is ...
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Custom bootloader booted via USB drive produces incorrect output on some computers
I am fairly new to assembly, but I'm trying to dive into the world of low level computing. I'm trying to learn how to write assembly code that would run as bootloader code; so independent of any other ...
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ARM bootloader: Interrupt Vector Table Understanding
The code following is the first part of u-boot to define interrupt vector table, and my question is how every line will be used. I understand the first 2 lines which is the starting point and the ...
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How can i put a compiled boot sector onto a USB stick or disk?
I'm actually interested in how an OS works, from the POST over the Boot process to the Kernel, GUI, etc.
Well I have to start at the beginning: The bootsector
Most tutorials only specify how to get ...
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Why 55 AA is used as the boot signature on IBM PCs? [closed]
Why does the IBM PC architecture use 55 AA magic numbers in the last two bytes of a bootsector for the boot signature?
I suspect that has something to do with the bit patterns they are: 01010101 ...
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Far jump in gdt in bootloader
flush_gdt:
lgdt [gdtr]
jmp 0x08:complete_flush
complete_flush:
mov ax, 0x10
mov ds, ax
mov es, ax
mov fs, ax
mov gs, ax
mov ss, ax
ret
I am unable to understand ...
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Page number in BIOS interrupts
I'm building a small bootloader for x86 as a project. For the moment I'm writing several functions to handle the screen, since it's a bit tedious. Most BIOS interrupt functions involve a page number ...
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How does the bootloader pick up the command after a "restarting system with command"?
Looking in the android source for the reboot command we find the following line:
__reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, \
LINUX_REBOOT_CMD_RESTART2, argv[optind]);
Which is the ...
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How to make the kernel for my bootloader?
I'm trying to make my own custom OS and I need some help with my code.
This is my bootloader.asm:
[ORG 0x7c00]
start:
cli
xor ax, ax
mov ds, ax
mov ss, ax
mov es, ax
mov [...
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Grub bootloader with shared library support
I'd like to load a shared library (closed-source binary user-space library) at boot stage with grub boot-loader. Are there any chances for this or I must write a custom-elf-loader (grub module) to do ...
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How do I run linux on an ARM Cortex M3 board?
I have a Luminary LM3s8962 ARM Cortex M3 development board, and while I've been able to program for it using the Keil RTOS, I'd much prefer to develop on top of linux and an embedded libc. What I ...
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Disk Read Error while loading sectors into memory
I tried to develop a bootloader using this, but when it is run it shows:
disk read error!
If I ignore it, in a later part, it shows me wrong memory mapping. I also followed some other sources too ...
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how to build grub2 bootloader from it's source and test it with qemu emulator
I want to know how to build grub 2 bootloader from it's source in ubuntu and test it with qemu emulator.
I would also like to change the default background image of grub2 bootloader in the new build?...
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Bootloader for Cortex M3
I am using a LPC 1768 board from mbed, (with cortex M3 cpu) and I am trying to achieve something here, mainly upgrade the user application from the SD Card, I am writing two programs, first a ...
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My bootloader can't be compiled with gcc 4.6 and 4.7 ... only 4.5
I created my bootloader before 2 years under debian squeeze/stable with gcc 4.5. Now in debian wheezy/sid can't be compiled with 4.6 and 4.7 because creates bigger sections from these i expecting to ...
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what is the need of second stage boot loader ? why different bootloaders like first stage and second stage?
I know the first stage boot loader will make basic hardware initializations and calls the second stage boot loader like u-boot. But I still do not understand for why we need multiple stages of boot ...
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Run a UEFI shell command from inside UEFI application
I'm new to UEFI application development.
My requirement is that,
I need to run an UEFI shell command from my UEFI application (app.efi) source code.
Need guidance on how I can do this.
Example,
...
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How to load second stage boot loader from first stage?
I have written simple first stage bootloader which displays "Hello world" using interrupt to bios. Now as a next obvious step to write a second stage, but where code for that should exist and how to ...
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Intel hex format and position independent code using gcc
I'm not sure if this is specific to the processor I'm using, so for what it's worth I'm using a Cortex M0+. I was wondering: if I generate a hex file through gcc using -fPIC, I produce...Position ...
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Where is there good information about low level PC booting?
I'm interested in writing a boot loader for USB sticks that looks for a directory of ISOs and gives you the option to boot one of them as if it were a bootable CD. This is basically so I have a menu ...
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How do I write a bin file (512 bytes) to the first sector (sector 0) of a floppy disk?
How do I write a .bin file to be in the first sector of a floppy disk/virtual floppy disk/floppy image?
I'm trying to boot a simple 512-byte bootloader. The size on everywhere says "512 bytes" so I ...
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which core initializes first when a system boots?
I want to know which core of a multicore processor initializes first when the cpu boots ? ( i mean at the bootloader level ) is the first core ? or random core ?
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How to step over interrupt calls when debugging a bootloader/bios with gdb and QEMU?
For educational purposes, I have adapted this bootloader from mikeos.berlios.de/write-your-own-os.html rewriting it to specifically load at address 0x7c00.
The final code is this:
[BITS 16] ...
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Using db to declare a string in assembly NASM
I am following a tutorial to write a hello world bootloader in assembly and I am using the NASM assembler for an x-86 machine. This is the code I am using :
[BITS 16] ;Tells the assembler that its ...
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How would I write a bootloader to load a c kernel?
I am learning NASM as I write bootloaders. So far I have a hello world bootloader. I want to know how to link a c program to it and have the bootloader load it into memory and start executing it's ...
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Stack segment in the MikeOS bootloader
I don't understand this piece of code:
mov ax, 07C0h ; Set up 4K of stack space above buffer
add ax, 544 ; 8k buffer = 512 paragraphs + 32 paragraphs (loader)
cli ; Disable ...
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PC boot: dl register and drive number
I read somewhere in the internet that, before jumping to 0x7c00, the BIOS loads into %dl the "drive number" of the booted device. But what is this "drive number"? Each device attached to the computer ...
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Read a write a sector from hard drive with int 13h
I have a simple program. It must read first sector from hard drive (not mbr), and write it to the 0 sector (mbr). But it doesnt work. I think it is connected with wrong DAP. Thanks.
[bits 16]
...
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understanding nasm assembly for outputting characters in teletype mode
I am reading this wonderful skript on operating system programming
http://www.cs.bham.ac.uk/~exr/lectures/opsys/10_11/lectures/os-dev.pdf
On Page 12 there is a simple bootloader.
If I understand ...
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How to switch from real mode to protected mode after bootloader?
I just finished up a very bare-bones bootloader for my OS and now I'm trying to switch to protected mode and jump to the kernel.
The kernel exists on the second sector (right after the bootloader) ...
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Near call/jump tables don't always work in a bootloader
General Problem
I've been developing a simple bootloader and have stumbled on a problem on some environments where instructions like these don't work:
mov si, call_tbl ; SI=Call table pointer
...
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