5 ms·

So uh, who's gonna be first to get it running on a Pi Pico?

vardump 3y ago
No one, unless you’re using a CPU emulator or a JIT with an SPI RAM. RP2040 doesn't have memory protection / virtual memory capability and has only 264 kB (or so) RAM.
em3rgent0rdr 3y ago
Pico is a microcontroller whose Cortex-M0+ cores lack a memory management unit for virtual memory (considered essential for a full-fledged OS like Linux). But can run FreeRTOS on it...memory usages are 236 bytes for the scheduler, 76 bytes + queue storage area for each queue, and 64 bytes plus task stack size for each task, plus 5 to 10 KBytes of ROM.[1] [1] https://freertos.org/FAQMem.html https://freertos.org/FAQMem.html
- moffkalast 3y ago
  Yeah I figured there might be a rub somewhere otherwise it would already be a thing, but since it's technically an ARM it sounded vaguely promising. What about a 32 bit build? I think those used to be able to work with without virtual addresses.
  - NegativeLatency 3y ago
    https://unix.stackexchange.com/questions/190350/mmu-less-kernel https://unix.stackexchange.com/questions/190350/mmu-less-ker...
    - em3rgent0rdr 3y ago
      aha, and this reminds me about μClinux [1] which targets microcontrollers without a MMU. I installing it on 2005 iPod Classic 5G, and was able to then put a gameboy emulator on it. https://en.wikipedia.org/wiki/%CE%9CClinux https://en.wikipedia.org/wiki/%CE%9CClinux
      - em3rgent0rdr 3y ago
        Though μClinux project seems dead, however the key component of that is a ELF to bFLT (binary flat) converter [1] for no-mmu Linux targets, which is alive on github [2]. [1] https://web.archive.org/web/20120301074213/https://retired.beyondlogic.org/uClinux/bflt.htm https://web.archive.org/web/20120301074213/https://retired.b... [2] https://github.com/uclinux-dev/elf2flt https://github.com/uclinux-dev/elf2flt
- yjftsjthsd-h 3y ago
  There's also inferno, which is more or less a full unix-like that can run on the pico ( https://news.ycombinator.com/item?id=37393993 https://news.ycombinator.com/item?id=37393993 ) and on the Teensy and some other microcontrollers ( https://dboddie.gitlab.io/inferno-diary/index.html https://dboddie.gitlab.io/inferno-diary/index.html )
- rzzzt 3y ago
  ELKS supported MMU-less operation on 8088 and 80286 machines, but I don't think an ARM port exists: https://github.com/ghaerr/elks https://github.com/ghaerr/elks
- gorkish 3y ago
  The popular way to shorehorn modern linux onto a MMU-less microcontroller is to build a a RISC V system emulator and run uClinux on that; you can also emulate the MMU and run regular kernels if you have sufficient resources. It has been done on ESP32 with sufficient RAM; Pico would need additional hardware though in the form of something like QSPI RAM, and of course it would be very slow.
mathiasgredal 3y ago
Not possible, unless you want to do it using an emulator and external memory. The lowest you can go for Linux is probably an ESP32: https://web.archive.org/web/20230515075935/http://wiki.osll.ru/doku.php/etc:users:jcmvbkbc:linux-xtensa:esp32s3 https://web.archive.org/web/20230515075935/http://wiki.osll.... https://github.com/jcmvbkbc/linux-xtensa/commits/xtensa-6.4-esp32/ https://github.com/jcmvbkbc/linux-xtensa/commits/xtensa-6.4-...
- jrockway 3y ago
  You don't need an ESP32. Someone made an AVR port: https://bit-tech.net/news/tech/cpus/linux-atmel-microcontrollers/1/ https://bit-tech.net/news/tech/cpus/linux-atmel-microcontrol... https://bit-tech.net/news/tech/cpus/linux-atmel-microcontrollers/1/ https://bit-tech.net/news/tech/cpus/linux-atmel-microcontrol... https://news.ycombinator.com/item?id=12537653 https://news.ycombinator.com/item?id=12537653

No one, unless you’re using a CPU emulator or a JIT with an SPI RAM. RP2040 doesn't have memory protection / virtual memory capability and has only 264 kB (or so) RAM.

em3rgent0rdr 3y ago

Pico is a microcontroller whose Cortex-M0+ cores lack a memory management unit for virtual memory (considered essential for a full-fledged OS like Linux). But can run FreeRTOS on it...memory usages are 236 bytes for the scheduler, 76 bytes + queue storage area for each queue, and 64 bytes plus task stack size for each task, plus 5 to 10 KBytes of ROM.[1] [1] https://freertos.org/FAQMem.html https://freertos.org/FAQMem.html

moffkalast 3y ago
Yeah I figured there might be a rub somewhere otherwise it would already be a thing, but since it's technically an ARM it sounded vaguely promising. What about a 32 bit build? I think those used to be able to work with without virtual addresses.
- NegativeLatency 3y ago
  https://unix.stackexchange.com/questions/190350/mmu-less-kernel https://unix.stackexchange.com/questions/190350/mmu-less-ker...
  - em3rgent0rdr 3y ago
    aha, and this reminds me about μClinux [1] which targets microcontrollers without a MMU. I installing it on 2005 iPod Classic 5G, and was able to then put a gameboy emulator on it. https://en.wikipedia.org/wiki/%CE%9CClinux https://en.wikipedia.org/wiki/%CE%9CClinux
    - em3rgent0rdr 3y ago
      Though μClinux project seems dead, however the key component of that is a ELF to bFLT (binary flat) converter [1] for no-mmu Linux targets, which is alive on github [2]. [1] https://web.archive.org/web/20120301074213/https://retired.beyondlogic.org/uClinux/bflt.htm https://web.archive.org/web/20120301074213/https://retired.b... [2] https://github.com/uclinux-dev/elf2flt https://github.com/uclinux-dev/elf2flt
yjftsjthsd-h 3y ago
There's also inferno, which is more or less a full unix-like that can run on the pico ( https://news.ycombinator.com/item?id=37393993 https://news.ycombinator.com/item?id=37393993 ) and on the Teensy and some other microcontrollers ( https://dboddie.gitlab.io/inferno-diary/index.html https://dboddie.gitlab.io/inferno-diary/index.html )
rzzzt 3y ago
ELKS supported MMU-less operation on 8088 and 80286 machines, but I don't think an ARM port exists: https://github.com/ghaerr/elks https://github.com/ghaerr/elks
gorkish 3y ago
The popular way to shorehorn modern linux onto a MMU-less microcontroller is to build a a RISC V system emulator and run uClinux on that; you can also emulate the MMU and run regular kernels if you have sufficient resources. It has been done on ESP32 with sufficient RAM; Pico would need additional hardware though in the form of something like QSPI RAM, and of course it would be very slow.

mathiasgredal 3y ago

Not possible, unless you want to do it using an emulator and external memory. The lowest you can go for Linux is probably an ESP32: https://web.archive.org/web/20230515075935/http://wiki.osll.ru/doku.php/etc:users:jcmvbkbc:linux-xtensa:esp32s3 https://web.archive.org/web/20230515075935/http://wiki.osll.... https://github.com/jcmvbkbc/linux-xtensa/commits/xtensa-6.4-esp32/ https://github.com/jcmvbkbc/linux-xtensa/commits/xtensa-6.4-...

jrockway 3y ago
You don't need an ESP32. Someone made an AVR port: https://bit-tech.net/news/tech/cpus/linux-atmel-microcontrollers/1/ https://bit-tech.net/news/tech/cpus/linux-atmel-microcontrol... https://bit-tech.net/news/tech/cpus/linux-atmel-microcontrollers/1/ https://bit-tech.net/news/tech/cpus/linux-atmel-microcontrol... https://news.ycombinator.com/item?id=12537653 https://news.ycombinator.com/item?id=12537653