arm64: report correct stack pointer in KSTK_ESP for compat tasks
arm64: report correct stack pointer in KSTK_ESP for compat tasks

The KSTK_ESP macro is used to determine the user stack pointer for a
given task. In particular, this is used to to report the '[stack]' VMA
in /proc/self/maps, which is used by Android to determine the stack
location for children of the main thread.

This patch fixes the macro to use user_stack_pointer instead of directly
returning sp. This means that we report w13 instead of sp, since the
former is used as the stack pointer when executing in AArch32 state.

Cc: <4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org>
Reported-by: Serban Constantinescu <9d35620722eae2b9cae3965128b3ab4db01c55f9@arm.com>
Signed-off-by: Will Deacon <b913f13ef92ac157955c954ccaaff7be065faba4@arm.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs