Debugging Baremetal Applications Using QEMU

Building QEMU

Install all necessary prerequisites which are necessary for building QEMU: https://wiki.qemu.org/Hosts/Linux. Then prepare sources and a build directory:

git clone https://github.com/foss-for-synopsys-dwc-arc-processors/qemu
mkdir -p qemu/build
cd qemu/build

Configure QEMU (use your own --prefix value):

../configure --target-list=arc-softmmu,arc64-softmmu,arc-linux-user,arc64-linux-user \
             --enable-debug --enable-debug-tcg --prefix=/tools/qemu

Build an install:

make
make install

Configure your environment:

export QEMU_HOME="/tools/qemu"
export PATH="${QEMU_HOME}/bin:$PATH"

Building and Debugging Applications

CPU family	Toolchain	QEMU binary	ARC-specific QEMU options
ARC HS3x/HS4x	arc-elf32-gcc	qemu-system-arc	-M arc-sim -cpu archs
ARC HS5x	arc64-elf-gcc	qemu-system-arc	-M arc-sim -cpu hs5x
ARC HS6x	arc64-elf-gcc	qemu-system-arc64	-M arc-sim -cpu hs6x

Building and Running "Hello, World!"

Consider a simple example code (save it as main.c):

#include <stdio.h>

int main()
{
    printf("Hello, World!\n");
    return 0;
}

You need to use -specs=qemu.specs to use input/output features and pass -serial stdio to link a virtual character device with host's stdio:

$ arc-elf32-gcc -mcpu=archs -specs=qemu.specs main.c -o main.elf
$ qemu-system-arc -M arc-sim -cpu archs -monitor none -display none -nographic \
                  -no-reboot -serial stdio -kernel main.elf
Hello, World!

By default, QEMU creates a character device for arc-sim board on hard coded 0x90000000 address. A program built with -specs=qemu.specs uses this address for all input/output operations. However, if -semihosting option is passed to QEMU, then it uses the same input/output interface as nSIM with -on nsim_emt option. It allows to use the same binary for running both on QEMU and nSIM:

$ arc-elf32-gcc -mcpu=archs -specs=nsim.specs main.c -o main.elf
$ qemu-system-arc -M arc-sim -cpu archs -monitor none -display none -nographic \
                  -no-reboot -serial stdio -semihosting -kernel main.elf
Hello, World!