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>

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index c0db321..1f7f5a2 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -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)