ARM: 7803/1: Fix deadlock scenario with smp_send_stop()
If one process calls sys_reboot and that process then stops other
CPUs while those CPUs are within a spin_lock() region we can
potentially encounter a deadlock scenario like below.

CPU 0                   CPU 1
-----                   -----
                        spin_lock(my_lock)
smp_send_stop()
 <send IPI>             handle_IPI()
                         disable_preemption/irqs
                          while(1);
 <PREEMPT>
spin_lock(my_lock) <--- Waits forever

We shouldn't attempt to run any other tasks after we send a stop
IPI to a CPU so disable preemption so that this task runs to
completion. We use local_irq_disable() here for cross-arch
consistency with x86.

Reported-by: Sundarajan Srinivasan <sundaraj@codeaurora.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

adapted from Linux 3.11-rc4 by mrg666
ARM: 7791/1: a.out: remove partial a.out support
a.out support on ARM requires that argc, argv and envp are passed in
r0-r2 respectively, which requires hacking load_aout_binary to
prevent argc being clobbered by the return code. Whilst mainline kernels
do set the registers up in start_thread, the aout loader has never
carried the hack in mainline.

Initialising the registers in this way actually goes against the libc
expectations for ELF binaries, where argc, argv and envp are passed on
the stack, with r0 being used to hold a pointer to an exit function for
cleaning up after the dynamic linker if required. If the pointer is
NULL, then it is ignored. When execing an ELF binary, Linux currently
zeroes r0, then sets it to argc and then finally clobbers it with the
return value of the execve syscall, so we actually end up with:

	r0 = 0
	stack[0] = argc
	r1 = stack[1] = argv
	r2 = stack[2] = envp

libc treats r1 and r2 as undefined. The clobbering of r0 by sys_execve
works for user-spawned threads, but when executing an ELF binary from a
kernel thread (via call_usermodehelper), the execve is performed on the
ret_from_fork path, which restores r0 from the saved pt_regs, resulting
in argc being presented to the C library. This has horrible consequences
when the application exits, since we have an exit function registered
using argc, resulting in a jump to hyperspace.

This patch solves the problem by removing the partial a.out support from
arch/arm/ altogether.

Cc: <stable@vger.kernel.org>
Cc: Ashish Sangwan <ashishsangwan2@gmail.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

adapted from Linux 3.11-rc4 by mrg666
ARM: 7755/1: handle user space mapped pages in flush_kernel_dcache_page
commit 1bc39742aab09248169ef9d3727c9def3528b3f3 upstream.

Commit f8b63c1 made flush_kernel_dcache_page a no-op assuming that
the pages it needs to handle are kernel mapped only.  However, for
example when doing direct I/O, pages with user space mappings may
occur.

Thus, continue to do lazy flushing if there are no user space
mappings.  Otherwise, flush the kernel cache lines directly.

Signed-off-by: Simon Baatz <gmbnomis@gmail.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

adapted from Linux 3.9.9 by mrg666