linux-kernel - [PATCH v3 00/12] allow BFLT executables on systems with a MMU

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Message-Id: <1468988424-32671-1-git-send-email-nicolas.pitre@linaro.org>
Date:	Wed, 20 Jul 2016 00:20:12 -0400
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:	Alexander Viro <viro@...iv.linux.org.uk>,
	David Howells <dhowells@...hat.com>,
	Greg Ungerer <gerg@...ux-m68k.org>
Subject: [PATCH v3 00/12] allow BFLT executables on systems with a MMU

This series provides the necessary changes to allow "flat" executable
binaries meant for no-MMU systems to actually run on systems with a MMU.

This can also be found in the following git repo:

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

*Why?*

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  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.

diffstat:

 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             | 453 +++++++++++++++++++++----------------
 fs/exec.c                    |  33 +++
 include/linux/binfmts.h      |   2 +
 7 files changed, 306 insertions(+), 233 deletions(-)