Building ARM ports (was Re: Globalscale Dreamplug and 8.3 RELEASE)

[Warner Losh]

On Aug 15, 2012, at 12:30 PM, Mattia Rossi wrote:

> 
>> The biggest problem we have is build versus run dependencies. When crossbuilding port foo to run on arm, that port decides it needs the compile_a_foo port to build the code, so it goes off and cross-builds compile_a_foo, then wants to run the resulting arm binaries on the x86 host. The only way I know of to fix that is to tediously identify and pre-build all the build-time requirements needed by any port you intend to cross-build. Ports that have their own build systems and custom tools are essentially impossible to work with.
> 
> Those are exactly the issues I've run into when attempting to cross build. See my story here:
> 
> http://matrossi.blogspot.it/2011/08/cross-compiling-ports-for-arm-under.html

Yes.  That's why you need something more than the hackish thing that I did that groks BUILD vs RUN depends and builds the BUILD depends native and the RUN depends cross.  I looked at this back in the day and found it was easier to do the following hackish thing:

(1) Create a chroot for building (we were doing this anyway)
(2) Create a port that described all the build depends.  Build and install it in the chroot.
(3) Then build the runtime ports with the cross compilers in the same chroot, but I needed hacks to install the packages into a different place, that was groked for chained dependencies and such.

A bit of a PITA, and I never filed the rough edges off of this enough to even commit it to the TSC tree.  It is a very time-intensive investigation to look into this stuff too, but maybe machines are fast enough that it isn't too horrible for the general case.

> My Qemu experience:
> 
> http://matrossi.blogspot.it/2011/09/freebsd-arm-on-qemu-in-virtualbox.html
> 
> but it didn't prove useful for building ports as there wasn't enough virtual memory to build them, because it fully emulates the 32M of RAM of a gumstix board as well..

There's hacks that make qemu emulate the boards with 2GB of RAM floating about...

Warner