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>

1 files changed, 0 insertions, 4 deletions

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index c0db321db7e1..1f7f5a2b61bf 100644
--- 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)