[PATCH v4 00/12] allow BFLT executables on systems with a MMU

From: Nicolas Pitre
Date: Wed Jul 20 2016 - 15:25:22 EST

This series provides the necessary changes to allow "flat" executable
binaries meant for no-MMU systems to actually run on systems with a MMU.
Also thrown in are various cleanups to binfmt_flat.c.

This can also be found in the following git repo:

git://git.linaro.org/people/nicolas.pitre/linux binfmt_flat_with_mmu


Because developing and testing natively on a large system with lots of
RAM makes it so much more convenient to use all the existing profiling
tools and debugging facilities that a kernel with lots of RAM can give.
And incidentally, those systems with lots of RAM all have a MMU.

*Why not use elf_fdpic?*

The flat executable format is simple with very small footprint
overhead, either in the executables themselves or kernel support.
This makes the flat format more suitable than elf_fdpic for very small
single-user-app embedded systems.

And while elf_fdpic binaries can run on MMU systems, flat binaries still
couldn't, which just felt wrong.

So here it is. The no-MMU support should remain unaffected, confirmed by
Greg Ungerer. Tested on ARM with MMU only with a busybox build.

Please consider for merging.

Changes since v3:

- Small cosmetic changes to pr_*().

- Addressed most important checkpatch complaints on the whole source file
and patches in this seris.

Changes since v2:

- Added protection against a corrupted header that could have caused nasty
overflows etc. Suggested by Alan Cox.

- printk() modernization. Suggested by Greg Ungerer / Geert Uytterhoeven.

- Added Greg Ungerer's reviewed-by tag.

Changes since v1:

- Removed SuperH and Xtensa from the Kconfig rule as they fail to build
due to lack of get/put_unaligned_user().

- Clarified some commit logs a bit.

arch/arm/include/asm/flat.h | 5 +-
arch/m68k/include/asm/flat.h | 5 +-
fs/Kconfig.binfmt | 3 +-
fs/binfmt_elf_fdpic.c | 38 +--
fs/binfmt_flat.c | 525 +++++++++++++++++++++----------------
fs/exec.c | 33 +++
include/linux/binfmts.h | 2 +
7 files changed, 339 insertions(+), 272 deletions(-)