QEMU AArch64 Virt Bare Bones: Difference between revisions
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=== boot.s === |
=== boot.s === |
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<source lang=" |
<source lang="asm"> |
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.global _start |
.global _start |
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_start: |
_start: |
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== Compiling the kernel == |
== Compiling the kernel == |
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Now, we'll need to compile our kernel so we can boot it. |
Now, we'll need to compile our kernel so we can boot it. |
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<source lang=" |
<source lang="bash"> |
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$ aarch64-elf-as boot.s -o boot.o |
$ aarch64-elf-as boot.s -o boot.o |
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$ aarch64-elf-gcc -ffreestanding -c kernel.c -o kernel.o |
$ aarch64-elf-gcc -ffreestanding -c kernel.c -o kernel.o |
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== Booting our kernel == |
== Booting our kernel == |
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Since our kernel is now compiled, we'll boot it with QEMU |
Since our kernel is now compiled, we'll boot it with QEMU |
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<source lang=" |
<source lang="bash"> |
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$ qemu-system-aarch64 -machine virt -cpu cortex-a57 -kernel kernel.elf -nographic |
$ qemu-system-aarch64 -machine virt -cpu cortex-a57 -kernel kernel.elf -nographic |
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Hello world! |
Hello world! |
Revision as of 08:02, 20 October 2021
QEMU is a free and open source hardware emulator that supports multiple architecture, including ARM. QEMU has it's own board with PCI support, called virt. virt supports ARM and RISC-V architecture.
In this tutorial, we'll write a basic kernel for QEMU virt board, specifically Aarch64.
Prerequisites
For this tutorial, you'll need
- An ARM cross-compiler toolchain
- QEMU, of course you'll need QEMU because this tutorial designed for QEMU virt.
Code
Now we'll need to write some code for our little kernel.
boot.s
.global _start
_start:
ldr x30, =stack_top
mov sp, x30
bl kmain
b .
kernel.c
#include <stdint.h>
volatile uint32_t *UART = (uint32_t *) 0x09000000;
void print(const char *s) {
while(*s != '\0') {
*UART = (uint8_t)(*s);
s++;
}
}
void kmain(void) {
print("Hello world!\n");
}
linker.ld
ENTRY(_start)
SECTIONS {
. = 0x40000000;
.startup . : { boot.o(.text) }
.text : { *(.text) }
.data : { *(.data) }
.bss : { *(.bss COMMON) }
. = ALIGN(8);
. = . + 0x1000; /* 4kB of stack memory */
stack_top = .;
}
Compiling the kernel
Now, we'll need to compile our kernel so we can boot it.
$ aarch64-elf-as boot.s -o boot.o
$ aarch64-elf-gcc -ffreestanding -c kernel.c -o kernel.o
$ aarch64-elf-ld -nostdlib -Tlinker.ld boot.o kernel.o -o kernel.elf
Booting our kernel
Since our kernel is now compiled, we'll boot it with QEMU
$ qemu-system-aarch64 -machine virt -cpu cortex-a57 -kernel kernel.elf -nographic
Hello world!