WIP: Apache NuttX RTOS for RISC-V QEMU (Initial RAM Disk)

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• "Star64 JH7110 + NuttX RTOS: RISC-V Semihosting and Initial RAM Disk"

See below for the Build Outputs. We built NuttX with these steps...

## Install the Build Prerequisites and Toolchain:
## https://lupyuen.github.io/articles/nuttx#install-prerequisites
## https://lupyuen.github.io/articles/riscv#appendix-download-toolchain-for-64-bit-risc-v

## Download the `ramdisk` branch of our WIP NuttX Repos
mkdir nuttx
cd nuttx
git clone --branch ramdisk https://github.com/lupyuen2/wip-pinephone-nuttx nuttx
git clone --branch ramdisk https://github.com/lupyuen2/wip-pinephone-nuttx-apps apps

## Configure and build NuttX
cd nuttx
tools/configure.sh rv-virt:knsh64
make

## Build Apps Filesystem
make export V=1
pushd ../apps
./tools/mkimport.sh -z -x ../nuttx/nuttx-export-*.tar.gz
make import V=1
popd

## Generate Initial RAM Disk
genromfs -f initrd -d ../apps/bin -V "NuttXBootVol"

## We assume that `nuttx` contains the NuttX ELF Image.
## Export the NuttX Binary Image to `nuttx.bin`
riscv64-unknown-elf-objcopy \
  -O binary \
  nuttx \
  nuttx.bin

## Dump the disassembly to nuttx.S
riscv64-unknown-elf-objdump \
  -t -S --demangle --line-numbers --wide \
  nuttx \
  >nuttx.S \
  2>&1

## Dump the init disassembly to init.S
riscv64-unknown-elf-objdump \
  -t -S --demangle --line-numbers --wide \
  ../apps/bin/init \
  >init.S \
  2>&1

## Copy the config to nuttx.config
cp .config nuttx.config

## Start QEMU with Initial RAM Disk
 qemu-system-riscv64 \
    -semihosting \
    -M virt,aclint=on \
    -cpu rv64 \
    -smp 8 \
    -bios none \
    -kernel nuttx \
    -initrd initrd \
    -nographic

(See the Build Log)

Here's the QEMU Output Log...

→   qemu-system-riscv64 \
    -semihosting \
    -M virt,aclint=on \
    -cpu rv64 \
    -smp 8 \
    -bios none \
    -kernel nuttx \
    -initrd initrd \
    -nographic \

ABCnx_start: Entry
uart_register: Registering /dev/console
uart_register: Registering /dev/ttyS0
work_start_lowpri: Starting low-priority kernel worker thread(s)
board_late_initialize:
nx_start_application: Starting init task: /system/bin/init
elf_symname: Symbol has no name
elf_symvalue: SHN_UNDEF: Failed to get symbol name: -3
elf_relocateadd: Section 2 reloc 2: Undefined symbol[0] has no name: -3
up_exit: TCB=0x802088d0 exiting

NuttShell (NSH) NuttX-12.0.3
nsh> nx_start: CPU0: Beginning Idle Loop

nsh> ls -l /system/bin/init
posix_spawn: pid=0xc0202978 path=ls file_actions=0xc0202980 attr=0xc0202988 argv=0xc0202a28
exec_spawn: ERROR: Failed to load program 'ls': -2
nxposix_spawn_exec: ERROR: exec failed: 2
 -r-xr-xr-x 3278720 /system/bin/init
nsh>

(See the Detailed Run Log)