User:Fabled

Bootstrapping new architectures

1. Create cross compiler
   • I decided to use crosstool-ng as build cross-compiler is tricky
     • Wrote patch to support musl as C-library
     • Wrote patch to enable building toolchains with PIE as default
   • Create crosstool-ng .config, My ARM config
     • NOTE: for some reason binutils gold linker crashes when compiling gcc, so needed to keep it disabled.
   • run 'ct-ng build' to build the new tool chain
2. Cross compile minimal system image
   • abuild and core APKBUILDs modified to support cross building
   • Wrote crossbuild-alpine-bootstrap.sh to invoke abuild with cross-compiler
   • Cross-building script uses abuild.conf overlay to define new target My ARM overlay
   • This produces all core .apk files for the target platform that can be used to boot qemu, qemu-user target or native hardware
3. Rebuild system and setup builder
   • Decided to use qemu-user for ARM as it the fastest option available for us (no fast native hardware yet)
   • Setup qemu-arm support for target chroot
     1. apk --arch x86 --root $chroot/qemu --initdb add qemu-arm
     2. cd $chroot/lib ; ln -s ../qemu/lib/ld-* .
     3. ldconfig -r $chroot /qemu/lib /qemu/usr/lib
     4. create binfmt_misc mapping
     5. seems qemu-user needs to access /proc/sys/vm/mmap_min_addr or it does not work
   • Setup target main chroot
     • apk --arch arm --root $chroot --initdb add alpine-base build-base
     • enter chroot