qemu-rom

Simple QEMU -bios ROM that initializes PCI and dispi framebuffers on all attached PCI-VGA

A cross compiler should be used to build this. The "elf" target cross compiler would work. Anything except system compilers. System compilers are patched by distributions to force some security related things into the compilation process, which interfere with programs that need precise control over the compilation and linking process.

Instructions

you@yourcomputer:~/somewhere-good
$ mkdir qemu-rom

you@yourcomputer:~/somewhere-good
$ cd qemu-rom

you@yourcomputer:~/somewhere-good/qemu-rom
$ git clone https://github.com/doug65536/qemu-rom.git src

you@yourcomputer:~/somewhere-good/qemu-rom
$ cd qemu-rom

Source now at ~/somewhere-good/qemu-rom/src/

If you need toolchain(s)

Get a script you can use to quickly build a cross toolchain

you@yourcomputer:~/somewhere-good/qemu-rom
git clone https://github.com/travisg/toolchains.git

you@yourcomputer:~/somewhere-good/qemu-rom
$ cd toolchains

you@yourcomputer:~/somewhere-good/qemu-rom/toolchains
$

Build an architecture, many architecture names work. The example command line creates ~/somewhere-good/qemu-rom/tools/aarch64-elf-Linux_x86_64 or something like that (read on below).

you@yourcomputer:~/somewhere-good/qemu-rom/toolchains
$ mkdir -p $PWD/../tools && ./doit -a aarch64 -f -o $PWD/../tools

Notice how vague I was? We just dynamically detect it

you@yourcomputer:~/somewhere-good/qemu-rom/toolchains
$ cd ..

you@yourcomputer:~/somewhere-good/qemu-rom/
$ toolchain=$(find tools -maxdepth 1 -name aarch64-\*)

you@yourcomputer:~/somewhere-good/qemu-rom/
$ toolchain_bin=$toolchain/bin

you@yourcomputer:~/somewhere-good/qemu-rom/
$ PATH=$toolchain_bin:$PATH

You have a toolchain

you@yourcomputer:~/somewhere-good/qemu-rom/
$ mkdir build-aarch64

you@yourcomputer:~/somewhere-good/qemu-rom/
$ cd build-aarch64

you@yourcomputer:~/somewhere-good/qemu-rom/build-aarch64
$ ../src/configure --host=aarch64-elf

you@yourcomputer:~/somewhere-good/qemu-rom/build-aarch64
$ make run -j$(nproc)

To launch vm with debugging completely disabled (no fighting over port 1234)

you@yourcomputer:~/somewhere-good/qemu-rom/build-aarch64
$ make run-nogdb -j$(nproc)

To launch vm for debugging

you@yourcomputer:~/somewhere-good/qemu-rom/build-aarch64
$ make debug -j$(nproc)

To launch toolchain gdb attached to qemu (presumably the one from make debug)

you@yourcomputer:~/somewhere-good/qemu-rom/build-aarch64
$ make attach

QEMU configuration

You can pass additional arguments to qemu by adding QEMUEXTRAFLAGS='-flags...' to the make command line arguments.