arm64: entry: sdei: Make 'tsk' available

For regular entry/exit sequences, we use 'tsk' (x28) to hold the current
task pointer, allowing this to be used by various assembly macros. The
SDEI entry/exit sequence uses x28 to hold the value of the interrupted
sp_el0, and doesn't retain the current task pointer in a register.

These differences makes it awkward to share assembly macros across
regular entry/exit and SDEI entry/exit, and risk surprises.

Align the SDEI entry/exit sequence with regular entry/exit, keeping the
current task pointer in 'tsk', and preserving the interrupted sp_el0 in
another (callee-saved) register. I've used x20 as x19 was already in
used for the relevant sdei_registered_event, and these are the
lowest-numbered registers above x18 (which we must preserve for shadow
call stack).

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Muhammad Usama Anjum <usama.anjum@arm.com>
Cc: Ada Couprie Diaz <ada.coupriediaz@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Jinjie Ruan <ruanjinjie@huawei.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Vladimir Murzin <vladimir.murzin@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Yang Shi <yang@os.amperecomputing.com>
Reviewed-by: Vladimir Murzin <vladimir.murzin@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

0 files changed, 0 insertions, 0 deletions