Re: [RFC] [PATCH 0/9] Initial cross-compilation support

[Henning Schild <henning.schild@siemens.com>]

Am Thu, 14 Jun 2018 14:04:47 +0200
schrieb Claudius Heine <ch@denx.de>:

> Hi,
> 
> On Wed, 2018-06-13 at 15:07 +0200, Alexander Smirnov wrote:
> > Hi all,
> > 
> > this series introduces basic cross-compilation support for Isar. The
> > implementation
> > is based around new entity - buildchroot-cross, which is quite
> > similar to original
> > buildchroot, but has host architecture.  
> 
> Here is a crazy idea from me and Henning:
> Have you tried just installing an amd64-arm cross toolchain into the
> existing arm buildchroot, then switch to it from the 'native'
> toolchain using a combination of PATH variable entries, symlinks
> and/or wrapper scripts and let binfmt deal with calling the amd64
> binaries of the toolchain in the arm chroot environment?

Another idea that comes very close to the SDK series. How about the
cross_build_chroot contains just the compiler and whatever the compiler
needs. Then we mount buildchroot/rootfs into cross_build_chroot/sysroot
and smuggle in the "--sysroot /sysroot/" i.e. by putting wrapper
scripts for gcc and friends into /usr/local/bin/.

Similar approach, but we do not risk breaking the buildchroot by
forcing an alien compiler into it. And we use less binfmt magic ...
Both the cross-compile and the SDK are very similar and if cross builds
on top of SDK we should be on the right track.

Henning

> This way the arm system would think that you are compiling nativly
> while in fact you are using a cross compiler that is not emulated.
> 
> Would that work?
> 
> Cheers,
> Claudius
> 
> > 
> > This series tested for the following configuration only:
> > 
> >  $ bitbake multiconfig:qemui386
> > 
> > In this build:
> >  - libhello is cross-compiled
> >  - example-hello is compiled traditionally (but it's successfully
> > linked with libhello)
> > 
> > TODO list:
> >  - Depending on the target architecture, various host tools should
> > be installed. For example
> >    binutils package has the following names:
> >    * binutils
> >    * binutils-x86-64-linux-gnu
> >    * binutils-arm-linux-gnueabihf
> >  - Cross-dependency installation. This topic is still open for me
> > because 'mk-build-deps' tool
> >    doesn't work here correctly. For example package depends on
> > binutils, but instead of
> >    installation of 'binutils-arm-linux-gnueabihf' it tries to
> > install 'binutils:armhf' and ruins
> >    the rootfs.
> > 
> > So, as usually, comments and suggestions are welcome :-)
> > 
> > With best redgards,
> > Alex
> > 
> > Alexander Smirnov (9):
> >   isar-bootstrap: Add routin to determine host arch
> >   isar-bootstrap: Move common part to include
> >   isar-bootstrap: Add host architecture support
> >   isar-bootstrap-helper: Add parameter to set arch
> >   buildchroot-cross: Initial implementation
> >   classes/dpkg*: Relocate dependency from buildchroot
> >   classes/dpkg*: Drop hardcoded buildchroot blobs
> >   classes/dpkg-cross: Initial implementation
> >   [FOR TESTING] libhello: Switch to cross compilation
> > 
> >  meta-isar/recipes-app/libhello/libhello.bb         |   2 +-
> >  meta/classes/dpkg-base.bbclass                     |  17 +-
> >  meta/classes/dpkg-cross.bbclass                    |  15 ++
> >  meta/classes/dpkg-raw.bbclass                      |   7 +-
> >  meta/classes/dpkg.bbclass                          |   7 +-
> >  meta/classes/image.bbclass                         |   2 +-
> >  meta/classes/isar-bootstrap-helper.bbclass         |  13 +-
> >  meta/conf/isar-bitbake.conf                        |   1 +
> >  .../isar-bootstrap/isar-bootstrap-host.bb          |  44 ++++
> >  .../isar-bootstrap/isar-bootstrap-target.bb        |  44 ++++
> >  meta/recipes-core/isar-bootstrap/isar-bootstrap.bb | 259 ---------
> > ------------
> >  .../recipes-core/isar-bootstrap/isar-bootstrap.inc | 223
> > ++++++++++++++++++
> >  .../buildchroot/buildchroot-cross.bb               |  53 +++++
> >  meta/recipes-devtools/buildchroot/buildchroot.bb   |   2 +-
> >  .../buildchroot/files/build-cross.sh               |  29 +++
> >  15 files changed, 443 insertions(+), 275 deletions(-)
> >  create mode 100644 meta/classes/dpkg-cross.bbclass
> >  create mode 100644 meta/recipes-core/isar-bootstrap/isar-bootstrap-
> > host.bb
> >  create mode 100644 meta/recipes-core/isar-bootstrap/isar-bootstrap-
> > target.bb
> >  delete mode 100644 meta/recipes-core/isar-bootstrap/isar-
> > bootstrap.bb
> >  create mode 100644 meta/recipes-core/isar-bootstrap/isar-
> > bootstrap.inc
> >  create mode 100644 meta/recipes-devtools/buildchroot/buildchroot-
> > cross.bb
> >  create mode 100644 meta/recipes-devtools/buildchroot/files/build-
> > cross.sh
> > 
> > -- 
> > 2.1.4
> >