Add strip support to esp-lp-hal

[Szybet]

When trying to:

[profile.release]
strip = true 

The program that tries to load the binary complains that it's not a ULP program. That's because strip removes the __ULP_MAGIC_ symbol. I was not able to keep it via linker script magic. The work around I was able to do is removing argument support:

main...Szybet:esp-hal:esp-lp-hal-strip

I don't know if it's possible to remain the symbol with strip, but it's worth it. For a simple blinky program it saves 1-2 Kb. Also everything seems to work fine, I just need to:

let pin: Output<3> = Output {};

I don't know the perfect solution for this, maybe a feature but I have no idea if they would work with those macros.

Any thoughts?

[MabezDev]

For a simple blinky program it saves 1-2 Kb

How did you measure this?

iirc strip does nothing on embedded programs. strip is only useful for reducing the size of an elf by stripping the debug symbols etc. For an embedded system, only the loadable sections of an ELF are actually flashed to the board.

[Szybet]

Huh, stat -c %s
So how do I measure the size then? How do I get a binary of the lp program that could be loaded from esp-idf? (Because I think it would be an awesome way to start using rust in esp-idf projects who want to use the lp core)

[MabezDev]

stat -c %s

On which file are you running this command, on the ELF, i.e esp-lp-hal/target/riscv32imc-unknown-none-elf/release/examples/blinky or something else?

How do I get a binary of the lp program that could be loaded from esp-idf? (Because I think it would be an awesome way to start using rust in esp-idf projects who want to use the lp core)

I'm not sure I follow this bit, but maybe @bjoernQ knows what you mean?

[bjoernQ]

If you want to see the size of code/data in memory you could use something like riscv32-esp-elf-size esp-lp-hal\target\riscv32imc-unknown-none-elf\release\examples\blinky

This outputs e.g.

   text    data     bss     dec     hex filename
   1392       4       0    1396     574 esp-lp-hal\target\riscv32imc-unknown-none-elf\release\examples\blinky

i.e. 1396 bytes

ESP-IDF uses its own mechanism to build and include LP-core code - see https://github.com/espressif/esp-idf/blob/59e18382702b6986be3d3f55e9ac7763c1397cf7/components/ulp/cmake/IDFULPProject.cmake#L194-L198 - TL;DR it's using objcpy

[Szybet]

I'm running it on target/riscv32imac-unknown-none-elf/release/yatchy-lp-program so it's good, and this binary gets smaller by applying strip

I got confused at this point, how do I get the bare memory which will be putted to rtc memory and executed? I think it's the file I wrote the path above?

[bjoernQ]

I got confused at this point, how do I get the bare memory which will be putted to rtc memory and executed? I think it's the file I wrote the path above?

No - that's the elf - running size on it will show text and data size (i.e. what gets into LP/RTC memory)

[Szybet]

Oh... Yea, now strip doesn't do anything... Nevermind

cargo objcopy --release -- -O binary out/yatchy-lp-program-new.bin and I have the pure binary

Thanks for clearing out my confusion 😄