interpreters/python: create Python's config files dynamically and other tweaks

[tmedicci]

Summary

• interpreters/python: add wrapper to initialize Python

  • This wrapper application checks if the Python's modules are already mounted (and mounts them, if not), sets the necessary environment variables and, then, runs the Python interpreter.

• interpreters/python: create Python's config files dynamically

  • The Setup.local and the config.site files are used by Python's build system to, respectively, enable or disable Python's modules and set/unset available functions in the target system. These files are now set according to NuttX's configs, enabling or disabling Python's features according to the configs set on NuttX.

• interpreters/python: set ROMFS-generated data to const char

  • This allows the data to be placed in the .rodata section, which can be allocated in the flash or other read-only storage, freeing the
    internal memory.

• interpreters/python: add patch to set _PyRuntime section

  • By setting a specific region for the _PyRuntime structure, it is possible to move it to the external memory, for instance, freeing the internal memory (this structure occupies around 140KiB).

Impact

This PR provides a set of improvements that allow running Python on NuttX easily: it provides a wrapper that enables running the Python interpreter directly with python and enables it to be built by architectures other than the RISC-V QEMU. Documentation will be updated on NuttX's OS repository as soon as we merge this PR.

Testing

Internal CI testing + rv-virt:python:

Building

$ make -j distclean && ./tools/configure.sh rv-virt:python && make -j$(nproc)

Running

$ qemu-system-riscv32 -semihosting -M virt,aclint=on -cpu rv32 -smp 8 \ 
   -global virtio-mmio.force-legacy=false \
   -device virtio-serial-device,bus=virtio-mmio-bus.0 \
   -chardev socket,telnet=on,host=127.0.0.1,port=3450,server=on,wait=off,id=foo \
   -device virtconsole,chardev=foo \
   -device virtio-rng-device,bus=virtio-mmio-bus.1 \
   -netdev user,id=u1,hostfwd=tcp:127.0.0.1:10023-10.0.2.15:23,hostfwd=tcp:127.0.0.1:15001-10.0.2.15:5001 \
   -device virtio-net-device,netdev=u1,bus=virtio-mmio-bus.2 \
   -drive file=./mydisk-1gb.img,if=none,format=raw,id=hd \
   -device virtio-blk-device,bus=virtio-mmio-bus.3,drive=hd \
   -bios none -kernel ./nuttx -nographic
ABC[    0.041394] board_userled: LED 1 set to 0
[    0.042074] board_userled: LED 2 set to 0
[    0.042178] board_userled: LED 3 set to 0
telnetd [4:100]

NuttShell (NSH) NuttX-10.4.0
nsh> python
[    2.321624] check_and_mount_romfs: Mounting ROMFS filesystem at target=/usr/local/lib with source=/dev/ram1
Python 3.13.0 (main, Jan 31 2025, 12:41:21) [GCC 13.2.0] on nuttx
Type "help", "copyright", "credits" or "license" for more information.
>>>

[nuttxpr]

[Experimental Bot, please feedback here]

Yes, this PR appears to meet the NuttX requirements. It provides a clear summary of the changes, their purpose, and how they work. The impact section is well-detailed, covering various aspects including user experience, build process, hardware, documentation, security, and compatibility. The testing section demonstrates verification on a relevant target (rv-virt:python) and provides build and run instructions along with example output, confirming the functionality.

[tmedicci]

@lupyuen , rv-virt: python is being tested on the NuttX build farm (accessible through nuttx-dashboard.org). Is it possible to trigger a test with a specific apps version (to test this PR, for instance)?

[cederom]

Thank you @tmedicci amazing work!! :-)

[lupyuen]

rv-virt: python is being tested on the NuttX build farm (accessible through nuttx-dashboard.org). Is it possible to trigger a test with a specific apps version (to test this PR, for instance)?

@tmedicci Sorry NuttX Build Farm doesn't support on-demand builds because:
(1) Build Farm is designed to plough through all builds as quickly as possible (to catch build problems earlier)
(2) So supporting on-demand builds might slow down the other builds
(3) Also: Build Farm runs on Home PCs. We have to think about Security when allowing on-demand builds on unmerged code

If NuttX has extra funding, we could probably:
(1) Set up (and maintain) a proper Build Farm with Security-Hardened Servers in a proper Data Centre
(2) Then we can allow on-demand build jobs for unmerged code
(3) Security Setup will probably look like this