Commit ee03353b authored Jan 05, 2016 by Mark Rutland Committed by Will Deacon Jan 06, 2016

arm64: entry: remove pointless SPSR mode check



In work_pending, we may skip work if the stacked SPSR value represents
anything other than an EL0 context. We then immediately invoke the
kernel_exit 0 macro as part of ret_to_user, assuming a return to EL0.
This is somewhat confusing.

We use work_pending as part of the ret_to_user/ret_fast_syscall state
machine. We only use ret_fast_syscall in the return from an SVC issued
from EL0. We use ret_to_user for return from EL0 exception handlers and
also for return from ret_from_fork in the case the task was not a kernel
thread (i.e. it is a user task).

Thus in all cases the stacked SPSR value must represent an EL0 context,
and the check is redundant. This patch removes it, along with the now
unused no_work_pending label.

Cc: Chris Metcalf <cmetcalf@ezchip.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent 39b5be9b

arch/arm64/kernel/entry.S

+0 −4

Original line number	Diff line number	Diff line
		@@ -676,10 +676,7 @@ ret_fast_syscall_trace:
		work_pending:
		tbnz x1, #TIF_NEED_RESCHED, work_resched
		/* TIF_SIGPENDING, TIF_NOTIFY_RESUME or TIF_FOREIGN_FPSTATE case */
		ldr x2, [sp, #S_PSTATE]
		mov x0, sp // 'regs'
		tst x2, #PSR_MODE_MASK // user mode regs?
		b.ne no_work_pending // returning to kernel
		enable_irq // enable interrupts for do_notify_resume()
		bl do_notify_resume
		b ret_to_user
		@@ -698,7 +695,6 @@ ret_to_user:
		and x2, x1, #_TIF_WORK_MASK
		cbnz x2, work_pending
		enable_step_tsk x1, x2
		no_work_pending:
		kernel_exit 0
		ENDPROC(ret_to_user)