This reverts commit 14f0aa35.

That commit was needed earlier because system call restarting for
OABI (compat) required an executable stack and thus had problems
with NX.  Since ab72b007 ("ARM: Fix signal restart issues
with NX and OABI compat") has reworked the code to not require an
executable stack anymore, we can re-enable NX support for kernels
with OABI (compat) support.
Signed-off-by: NRabin Vincent <rabin@rab.in>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Our signal syscall restart handling for these kernels still uses
the userspace stack to build code for restarting the syscall.
Unfortunately, fixing this is non-trivial, and so for the time
being, we resolve the problem by disabling NX support.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

READ_IMPLIES_EXEC must be set when:
o binary _is_ an executable stack (i.e. not EXSTACK_DISABLE_X)
o processor architecture is _under_ ARMv6 (XN bit is supported from ARMv6)
Signed-off-by: NMakito SHIOKAWA <lkhmkt@gmail.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

2.6.28-rc tightened up the ELF architecture checks on ARM.  For
non-EABI it only allows VFP if the hardware supports it.  However,
the kernel fails to also inspect the soft-float flag, so it
incorrectly rejects binaries using soft-VFP.

The fix is simple: also check that EF_ARM_SOFT_FLOAT isn't set
before rejecting VFP binaries on non-VFP hardware.
Acked-by: NMikael Pettersson <mikpe@it.uu.se>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>

Add support for detecting non-executable stack binaries, and adjust
permissions to prevent execution from data and stack areas.  Also,
ensure that READ_IMPLIES_EXEC is enabled for older CPUs where that
is true, and for any executable-stack binary.
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>