The naked attribute is known to confuse some old gcc versions when
function arguments aren't explicitly listed as inline assembly operands
despite the gcc documentation. That resulted in commit 9a40ac86
("ARM: 6164/1: Add kto and kfrom to input operands list.").

Yet that commit has problems of its own by having assembly operand
constraints completely wrong. If the generated code has been OK since
then, it is due to luck rather than correctness. So this patch also
provides proper assembly operand constraints, and removes two instances
of redundant register usages in the implementation while at it.

Inspection of the generated code with this patch doesn't show any
obvious quality degradation either, so not relying on __naked at all
will make the code less fragile, and avoid some issues with clang.

The only remaining __naked instances (excluding the kprobes test cases)
are exynos_pm_power_up_setup(), tc2_pm_power_up_setup() and

cci_enable_port_for_self(. But in the first two cases, only the function
address is used by the compiler with no chance of inlining it by
mistake, and the third case is called from assembly code only. And the
fact that no stack is available when the corresponding code is executed
does warrant the __naked usage in those cases.
Signed-off-by: NNicolas Pitre <nico@linaro.org>
Reviewed-by: NStefan Agner <stefan@agner.ch>
Tested-by: NStefan Agner <stefan@agner.ch>
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>