How to get a crosscompile toolchain for aarch64 for use in poudriere[?]

[Meyer, Wolfgang]

> -----Original Message-----
> From: Meyer, Wolfgang
> Sent: Freitag, 10. Februar 2017 17:19
> To: Meyer, Wolfgang; 'freebsd-arm at FreeBSD.org'; 'freebsd-
> toolchain at FreeBSD.org'
> Subject: RE: How to get a crosscompile toolchain for aarch64 for use in
> poudriere[?]
>
> > Hello,
> >
> >
> > To make the long story short, after comparing the verbose output of my
> > compiling in the jails with that of a direct crosscompile I found out
> > that it was able to correctly link some object files when providing
> > absolute paths to the crt*.o files and correct library search path for the
> libgcc_something libraries.
> > Which of course doesn't help when the linker is implicitly called by
> > the compiler. Further research showed that I could crosscompile/link
> > when providing the --sysroot=/ flag to overwrite the sysroot
> > configuration from the build of the crosscompiler. Amending the lines
> >
> > CFLAGS+=--sysroot=/
> > CPPFLAGS+=--sysroot=/  (Don't know if needed)
> > CXXFLAGS+=--sysroot=/
> > LDFLAGS+=--sysroot=/
> >
> > to my poudriere make.conf file I finally was able to produce a working
> > cross- compiled package for aarch64 in poudriere. And the gains are
> > quite significant (around 21 minutes for building pkg package with
> > qemu-user emulation vs 5 minutes using cross-compilation, native amd64
> > build in poudriere finishes in less than a minute).
> >
> > Still the creation of the cross-compiling toolchain seems to be quite
> > cumbersome. Hence advice on getting such a toolchain in a cleaner way
> > (ideally probably a working build for the xdev target) are greatly
> appreciated.
> >
>
>
> After building some more packages besides of pkg it seems, I am still not
> there yet. There is quite some fallout mainly during configure due to not
> getting the right searchpath for the libraries. Maybe creating a symlink on the
> root directory at the path of the expected sysroot directory might heal this.


In the meantime I figured out how to tweak the jail to get it to cross-build the desired subset of ports without fallout. Some of the changes are merely cosmetic but lead to a cleaner overall configuration in my point of view. Changes to the previously described configuration include:

- before starting the kernel-toolchain build make two nullfs-mounts:
> mount -t nullfs /<root_of_poudriere_jail>/usr/src /usr/src
> mount -t nullfs /<root_of_poudriere_jail>/usr/obj /usr/obj
- after kernel-toolchain build and copying /<root_of_poudriere_jail>/usr/obj/usr/src/tmp/* to /<root_of_poudriere_jail>/usr/aarch64-freebsd delete /<root_of_poudriere_jail>/usr/obj/usr/src/tmp and create a symlink to / at /<root_of_poudriere_jail>/usr/obj/usr/src/tmp

Now all tested ports cross-build fine with varying speed gains compared to the qemu-user emulated (in the ballpark of two- to eightfold, but not analysed in detail).


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