[Buildroot] [RFC 0/6] Support 32-bit binaries on a 64-bit architecture

[Markus Mayer]

This series contains a proposal for supporting 32-bit libraries and
binaries on a 64-bit platform.

There are some limitations and prerequisites as to the scope this has
been tested.

- It has only been tested on ARM/ARM64.
- It has only been tested with an external toolchain
  (https://github.com/Broadcom/stbgcc-6.3/releases).
- It requires that the Aarch64 compiler be compiled with "multi-lib"
  enabled. This ensures that the sysroot doesn't contain a lib64 ->
  lib symlink. Instead, lib and lib64 are separate directories.
- It has only been tested with a fairly limited number of packages.
  There might be other packages that don't correctly pass --libdir,
  similar to bzip2 as mentioned below.

The patches in this series make the following changes, in this order:

- ensure that check-bin-arch allows Aarch32 binaries on Aarch64
- introduce some new BR2 configuration variables (primarily for the
  32-bit sysroot location on the host and where system libraries live
  by default on the target)
- tell the Buildroot core not to create lib32 or lib64 symlink when
  32-bit support is enabled
- tell the Buildroot core to copy the 32-bit sysroot when 32-bit support
  is enabled
- introduce the $(LIBDIR) variable to the bzip2 package, so we can tell
  it that libbz2.so should go in /usr/lib64 when that is desired
- modify the package core to pass /usr/lib (or /usr/lib64) as the library
  location for the system

The result is that all 64-bit shared libraries should be installed into
/usr/lib64. The 32-bit libraries are copied from the 32-bit sysroot on
the host into /usr/lib.

I am quite certain this submission will only be a first step, but it does
look like there are others who are faced with the same issue.

Markus Mayer (6):
  support/scripts/check-bin-arch: improve architecture check
  system/Config.in: add configuration options for 32-bit library support
  core: system and toolchain: 32-bit run-time support on 64-bit platform
  core/pkg-toolchain-external: copy external 32-bit libraries to staging
  bzip2: introduce make variable $(LIBDIR)
  package: use BR2_ROOTFS_LIB_DIR for all libraries we use

 package/bzip2/0003-add-libdir-to-makefile.patch    | 36 ++++++++++++++++++++++
 .../bzip2/0004-add-libdir-to-makefile-libbz2.patch | 31 +++++++++++++++++++
 package/bzip2/bzip2.mk                             |  4 ++-
 package/dmalloc/dmalloc.mk                         |  7 +++--
 package/e2fsprogs/e2fsprogs.mk                     |  2 ++
 package/libzlib/libzlib.mk                         |  3 +-
 package/linux-tools/linux-tool-cpupower.mk.in      |  7 ++++-
 package/pciutils/pciutils.mk                       |  2 ++
 package/pkg-autotools.mk                           |  1 +
 package/readline/readline.mk                       |  2 +-
 support/scripts/check-bin-arch                     | 15 +++++++++
 system/Config.in                                   | 34 ++++++++++++++++++++
 system/system.mk                                   | 11 ++++++-
 .../toolchain-external/pkg-toolchain-external.mk   | 13 +++++++-
 15 files changed, 161 insertions(+), 10 deletions(-)
 create mode 100644 package/bzip2/0003-add-libdir-to-makefile.patch
 create mode 100644 package/bzip2/0004-add-libdir-to-makefile-libbz2.patch

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2.7.4