WIP: architectures: added cortex-a72 architecture.

[diogogithub]

Tried this for compilation/testing: diogogithub@727baa9

Read the following to better understand what flags would make sense:

https://developer.arm.com/documentation/ihi0056/g/
https://github.com/bminor/binutils-gdb/blob/master/gas/config/tc-aarch64.c#L32
https://embeddedartistry.com/blog/2017/10/11/demystifying-arm-floating-point-compiler-options/
https://www.mail-archive.com/[email protected]/msg218644.html
https://gist.github.com/fm4dd/c663217935dc17f0fc73c9c81b0aa845
https://en.wikipedia.org/wiki/ARM_Cortex-A72
https://www.raspberrypi.org/documentation/hardware/raspberrypi/bcm2711/rpi_DATA_2711_1p0.pdf

I'm a bit unsure if the right target_ar argument is aarch64-elf, I kinda feel elf64-little would make sense as well?
And there's also floating point that, from ARM docs, I ended settling on this...

[diogogithub]

Read some more things and tried a bit more:

https://gcc.gnu.org/gcc-5/changes.html
https://en.wikichip.org/wiki/arm_holdings/microarchitectures/cortex-a72
https://github.com/raspberrypi/userland/blob/master/makefiles/cmake/toolchains/aarch64-linux-gnu.cmake
https://www.raspberrypi.org/documentation/configuration/config-txt/
https://en.wikipedia.org/wiki/ARM11
https://community.arm.com/developer/tools-software/oss-platforms/w/docs/473/arm-reference-platforms-deliverables

[diogogithub]

To actually compile this testbed vehicle it's needed a more recent version of gcc, kernel, etc. I tried doing such maintenance with diogogithub@88dd2cf but I was going through a very long hellish experience and stopped trying when I finally got stuck with libssl-dev.

Hence, I think we're just going to use another distro and compile Dune on it. The impression this repo's code gives is that it isn't seriously maintained since 2015~2017. I really don't understand why everything is compiled from source with the rules, why not simply use a package manager?

Being that said, I hope some of this code turns out to be helpful contributions and I'm sorry if I'm misunderstanding and confusing things, did learn something from trying to make this work so, at least there's that.

[tsmarques]

The way I see it package managers are very compelling for being easy to use but they can quickly clutter the OS with packages. Most of our needs with this distro have been more or less static for each system in terms of packages so they are compiled at build time and that's it. On the rare occasion we need a new package you re-compile and do a quick a field-upgrade over the air.

From you patches I see that you set cfg_architecture wrong. The architecture is armv8 and micro-architecture is cortex-a72 and is used in -mcpu option on GCC as -mcpu=cortex-a72

[diogogithub]

Alpine has a package manager and doesn't get all that cluttered but I get your point. I think I only got a bit annoyed with the versions that are set in the rules as I was expecting this to be as trivial as adding the architecture, the system and bada bim bada bum, things work :')

Okay, so these flags aren't as right as I thought they were, hm...

[pmfg]

Currently for RPI4 we only have the 32Bit version (feature/rpi4), the 64Bit version is not yet created.
In the branch feature/rpi4 we have the gcc is 5.4 and the kernel is 4.19.
For the compilation of glued it is necessary to use the existing docker in glued.

[tsmarques]

Alpine has a package manager and doesn't get all that cluttered but I get your point. I think I only got a bit annoyed with the versions that are set in the rules as I was expecting this to be as trivial as adding the architecture, the system and bada bim bada bum, things work :')

Okay, so these flags aren't as right as I thought they were, hm...

I meant for our specific use case. Alpine's a bit more generic