TinyEMU with patches to work with (patched) Linux 6.10.11 and Buildroot 2024.02.06

TinyEMU code by Fabrice Bellard taken from https://bellard.org/tinyemu/
riscv-pk patches by Fabrice Bellard, taken from https://bellard.org/tinyemu/diskimage-linux-riscv-2018-09-23.tar.gz (see patches/riscv-pk.diff)

Some changes might have been also taken from the following repositories:

• https://github.com/drorgl/buildroot-tinyemu, https://github.com/drorgl/esp32-tinyemu (https://blog.drorgluska.com/2022/07/risc-v-linux-on-esp32.html)
• https://github.com/fernandotcl/TinyEMU
• https://github.com/michaelforney/tinyemu

fixed issues

• kernel hang during boot - see notes/linux-bisect-unaligned-access, unaligned_access.patch, check_unaligned_access_all_cpus is either too slow, or causes a hang
• kernel hang after boot - see tinyemu/riscv_machine.c:649, notes/linux-bisect-mm-hang, linux probably started overwriting firmware, fixed by adding more memory to reserved-memory in dtb
• system hang after boot - some applications were waiting for higher entropy, fixed after adding haveged to system from buildroot
• sleep hangs, time does not progress - fixed by implementing rdtime csr read in emulator. probably should've been handled by bbl/pk, but for some reason isn't. clock is still too slow, but at least it progresses
• emscripten issues - -O0 adds asserts, js functions called from c needed __sig entries

setup notes (WIP)

buildroot

Place contents of buildroot in unpacked buildroot-2024.02.06. Then run:

make -j8
. ./output/host/environment-setup

To make the kernel image compatible with TinyEMU:

riscv64-buildroot-linux-gnu-objcopy ./output/images/vmlinux  -O binary ./kernel-riscv64.bin

The following may be required if you change filesystem size:

e2fsck -f ./buildroot/output/images/rootfs.ext2
resize2fs -M ./buildroot/output/images/rootfs.ext2

riscv-pk

Version in this repo was patched with patches from https://bellard.org/tinyemu/diskimage-linux-riscv-2018-09-23.tar.gz (see patches/riscv-pk.diff)

git clone https://github.com/riscv-software-src/riscv-pk
git checkout ac2c910b18c3e36cfd85080472e78ad2fe484325

(now apply patches written by Fabrice Bellard on the repository)

Buildroot should build or download RISC-V toolchain after make, the environment-setup script adds it to PATH. Assuming buildroot is in ../buildroot and PWD is riscv-pk:

. ../buildroot/output/host/environment-setup
mkdir build
cd build
../configure --host=riscv64-unknown-elf --prefix=`realpath ../buildroot/output/host/`/
CFLAGS="-fno-stack-protector" make -j8

To make bbl image compatible with TinyEMU:

riscv64-buildroot-linux-gnu-objcopy -O binary bbl bbl.bin

tinyemu

To convert rootfs created by buildroot to format compatible with TinyEMU:

./splitimg ../../buildroot-2024.02.6/output/images/rootfs.ext2 ./root-riscv64

In TinyEMU config, drive0.file should be set to root-riscv64/blk.txt (same directory as above).

x11

• fbdev module - not required?
• xterm - mount devpts /dev/pts -t devpts -o mode=620