I've recently been getting into bare metal development for the Raspberry Pi 2, and having some success. Admittedly I've hesitated to buy an actual physical device until I feel I can do something useful with it, for the time being I've been emulating the device using qemu 2.11.0. So far I've developed multicore capabilities for my kernel, as well as simple Serial I/O, but I feel I'd like to get much further before working with a physical device.
My issue right now is that I'm trying to learn how to place my kernel onto an SD card image and boot qemu-system-arm from that SD card image, so I can properly emulate a kernel loaded from the raspberry pi 2 bootloader.
I've gotten as far as grabbing the SD card contents from https://github.com/raspberrypi/firmware ... aster/boot, and using the following script to create the image and load my kernel into it. I've seen that people have figured out how to load Raspbian from an emulated SD card, so I figure I can do the same.
#!/bin/bash
OUTPUT_IMG=os.img
OUTPUT_IMG_SIZE=40
TEMP_MOUNT_DIR="$(mktemp -d)"
# the SD card boot partition contents are in this folder...
OUTPUT_IMG_CONTENTS_DIR="./sd"
OS_DIR="${HOME}/os"
OS_BINARY="${OS_DIR}/kernel.bin"
dd if=/dev/null of=${OUTPUT_IMG} bs=1M seek=${OUTPUT_IMG_SIZE}
mkfs.fat -F 32 ${OUTPUT_IMG}
sudo mount -t vfat -o loop ${OUTPUT_IMG} ${TEMP_MOUNT_DIR}
make -C ${OS_DIR} clean
make -C ${OS_DIR}
sudo cp -r ${OUTPUT_IMG_CONTENTS_DIR} ${TEMP_MOUNT_DIR}
sudo cp ${OS_BINARY} "${TEMP_MOUNT_DIR}/kernel.img"
The only issue is that qemu doesn't seem to boot from this image using the following command:
qemu-system-arm -machine raspi2 -serial file:serial.log -sd ./dev/os.img
I've tried a few different combinations, but to no avail.
I can see from hooking GDB that the kernel is simply not booting from this card image. Loading the kernel directly into qemu with the -kernel argument works otherwise perfectly.
I was wondering if anyone here had any insight on how to accomplish this! Any help here would be greatly appreciated!
