v4.19.13 snapshot.
diff --git a/arch/arc/kernel/entry.S b/arch/arc/kernel/entry.S
new file mode 100644
index 0000000..85d9ea4
--- /dev/null
+++ b/arch/arc/kernel/entry.S
@@ -0,0 +1,367 @@
+/*
+ * Common Low Level Interrupts/Traps/Exceptions(non-TLB) Handling for ARC
+ * (included from entry-<isa>.S
+ *
+ * Copyright (C) 2014-15 Synopsys, Inc. (www.synopsys.com)
+ * Copyright (C) 2004, 2007-2010, 2011-2012 Synopsys, Inc. (www.synopsys.com)
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+/*------------------------------------------------------------------
+ * Function ABI
+ *------------------------------------------------------------------
+ *
+ * Arguments r0 - r7
+ * Caller Saved Registers r0 - r12
+ * Callee Saved Registers r13- r25
+ * Global Pointer (gp) r26
+ * Frame Pointer (fp) r27
+ * Stack Pointer (sp) r28
+ * Branch link register (blink) r31
+ *------------------------------------------------------------------
+ */
+
+;################### Special Sys Call Wrappers ##########################
+
+ENTRY(sys_clone_wrapper)
+ SAVE_CALLEE_SAVED_USER
+ bl @sys_clone
+ DISCARD_CALLEE_SAVED_USER
+
+ GET_CURR_THR_INFO_FLAGS r10
+ btst r10, TIF_SYSCALL_TRACE
+ bnz tracesys_exit
+
+ b .Lret_from_system_call
+END(sys_clone_wrapper)
+
+ENTRY(ret_from_fork)
+ ; when the forked child comes here from the __switch_to function
+ ; r0 has the last task pointer.
+ ; put last task in scheduler queue
+ jl @schedule_tail
+
+ ld r9, [sp, PT_status32]
+ brne r9, 0, 1f
+
+ jl.d [r14] ; kernel thread entry point
+ mov r0, r13 ; (see PF_KTHREAD block in copy_thread)
+
+1:
+ ; Return to user space
+ ; 1. Any forked task (Reach here via BRne above)
+ ; 2. First ever init task (Reach here via return from JL above)
+ ; This is the historic "kernel_execve" use-case, to return to init
+ ; user mode, in a round about way since that is always done from
+ ; a kernel thread which is executed via JL above but always returns
+ ; out whenever kernel_execve (now inline do_fork()) is involved
+ b ret_from_exception
+END(ret_from_fork)
+
+;################### Non TLB Exception Handling #############################
+
+; ---------------------------------------------
+; Instruction Error Exception Handler
+; ---------------------------------------------
+
+ENTRY(instr_service)
+
+ EXCEPTION_PROLOGUE
+
+ lr r0, [efa]
+ mov r1, sp
+
+ FAKE_RET_FROM_EXCPN
+
+ bl do_insterror_or_kprobe
+ b ret_from_exception
+END(instr_service)
+
+; ---------------------------------------------
+; Machine Check Exception Handler
+; ---------------------------------------------
+
+ENTRY(EV_MachineCheck)
+
+ EXCEPTION_PROLOGUE
+
+ lr r2, [ecr]
+ lr r0, [efa]
+ mov r1, sp
+
+ ; hardware auto-disables MMU, re-enable it to allow kernel vaddr
+ ; access for say stack unwinding of modules for crash dumps
+ lr r3, [ARC_REG_PID]
+ or r3, r3, MMU_ENABLE
+ sr r3, [ARC_REG_PID]
+
+ lsr r3, r2, 8
+ bmsk r3, r3, 7
+ brne r3, ECR_C_MCHK_DUP_TLB, 1f
+
+ bl do_tlb_overlap_fault
+ b ret_from_exception
+
+1:
+ ; DEAD END: can't do much, display Regs and HALT
+ SAVE_CALLEE_SAVED_USER
+
+ GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10
+ st sp, [r10, THREAD_CALLEE_REG]
+
+ j do_machine_check_fault
+
+END(EV_MachineCheck)
+
+; ---------------------------------------------
+; Privilege Violation Exception Handler
+; ---------------------------------------------
+ENTRY(EV_PrivilegeV)
+
+ EXCEPTION_PROLOGUE
+
+ lr r0, [efa]
+ mov r1, sp
+
+ FAKE_RET_FROM_EXCPN
+
+ bl do_privilege_fault
+ b ret_from_exception
+END(EV_PrivilegeV)
+
+; ---------------------------------------------
+; Extension Instruction Exception Handler
+; ---------------------------------------------
+ENTRY(EV_Extension)
+
+ EXCEPTION_PROLOGUE
+
+ lr r0, [efa]
+ mov r1, sp
+
+ FAKE_RET_FROM_EXCPN
+
+ bl do_extension_fault
+ b ret_from_exception
+END(EV_Extension)
+
+;################ Trap Handling (Syscall, Breakpoint) ##################
+
+; ---------------------------------------------
+; syscall Tracing
+; ---------------------------------------------
+tracesys:
+ ; save EFA in case tracer wants the PC of traced task
+ ; using ERET won't work since next-PC has already committed
+ lr r12, [efa]
+ GET_CURR_TASK_FIELD_PTR TASK_THREAD, r11
+ st r12, [r11, THREAD_FAULT_ADDR] ; thread.fault_address
+
+ ; PRE Sys Call Ptrace hook
+ mov r0, sp ; pt_regs needed
+ bl @syscall_trace_entry
+
+ ; Tracing code now returns the syscall num (orig or modif)
+ mov r8, r0
+
+ ; Do the Sys Call as we normally would.
+ ; Validate the Sys Call number
+ cmp r8, NR_syscalls
+ mov.hi r0, -ENOSYS
+ bhi tracesys_exit
+
+ ; Restore the sys-call args. Mere invocation of the hook abv could have
+ ; clobbered them (since they are in scratch regs). The tracer could also
+ ; have deliberately changed the syscall args: r0-r7
+ ld r0, [sp, PT_r0]
+ ld r1, [sp, PT_r1]
+ ld r2, [sp, PT_r2]
+ ld r3, [sp, PT_r3]
+ ld r4, [sp, PT_r4]
+ ld r5, [sp, PT_r5]
+ ld r6, [sp, PT_r6]
+ ld r7, [sp, PT_r7]
+ ld.as r9, [sys_call_table, r8]
+ jl [r9] ; Entry into Sys Call Handler
+
+tracesys_exit:
+ st r0, [sp, PT_r0] ; sys call return value in pt_regs
+
+ ;POST Sys Call Ptrace Hook
+ bl @syscall_trace_exit
+ b ret_from_exception ; NOT ret_from_system_call at is saves r0 which
+ ; we'd done before calling post hook above
+
+; ---------------------------------------------
+; Breakpoint TRAP
+; ---------------------------------------------
+trap_with_param:
+
+ ; stop_pc info by gdb needs this info
+ lr r0, [efa]
+ mov r1, sp
+
+ ; Now that we have read EFA, it is safe to do "fake" rtie
+ ; and get out of CPU exception mode
+ FAKE_RET_FROM_EXCPN
+
+ ; Save callee regs in case gdb wants to have a look
+ ; SP will grow up by size of CALLEE Reg-File
+ ; NOTE: clobbers r12
+ SAVE_CALLEE_SAVED_USER
+
+ ; save location of saved Callee Regs @ thread_struct->pc
+ GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10
+ st sp, [r10, THREAD_CALLEE_REG]
+
+ ; Call the trap handler
+ bl do_non_swi_trap
+
+ ; unwind stack to discard Callee saved Regs
+ DISCARD_CALLEE_SAVED_USER
+
+ b ret_from_exception
+
+; ---------------------------------------------
+; syscall TRAP
+; ABI: (r0-r7) upto 8 args, (r8) syscall number
+; ---------------------------------------------
+
+ENTRY(EV_Trap)
+
+ EXCEPTION_PROLOGUE
+
+ ;============ TRAP 1 :breakpoints
+ ; Check ECR for trap with arg (PROLOGUE ensures r9 has ECR)
+ bmsk.f 0, r9, 7
+ bnz trap_with_param
+
+ ;============ TRAP (no param): syscall top level
+
+ ; First return from Exception to pure K mode (Exception/IRQs renabled)
+ FAKE_RET_FROM_EXCPN
+
+ ; If syscall tracing ongoing, invoke pre-post-hooks
+ GET_CURR_THR_INFO_FLAGS r10
+ btst r10, TIF_SYSCALL_TRACE
+ bnz tracesys ; this never comes back
+
+ ;============ Normal syscall case
+
+ ; syscall num shd not exceed the total system calls avail
+ cmp r8, NR_syscalls
+ mov.hi r0, -ENOSYS
+ bhi .Lret_from_system_call
+
+ ; Offset into the syscall_table and call handler
+ ld.as r9,[sys_call_table, r8]
+ jl [r9] ; Entry into Sys Call Handler
+
+.Lret_from_system_call:
+
+ st r0, [sp, PT_r0] ; sys call return value in pt_regs
+
+ ; fall through to ret_from_exception
+END(EV_Trap)
+
+;############# Return from Intr/Excp/Trap (Linux Specifics) ##############
+;
+; If ret to user mode do we need to handle signals, schedule() et al.
+
+ENTRY(ret_from_exception)
+
+ ; Pre-{IRQ,Trap,Exception} K/U mode from pt_regs->status32
+ ld r8, [sp, PT_status32] ; returning to User/Kernel Mode
+
+ bbit0 r8, STATUS_U_BIT, resume_kernel_mode
+
+ ; Before returning to User mode check-for-and-complete any pending work
+ ; such as rescheduling/signal-delivery etc.
+resume_user_mode_begin:
+
+ ; Disable IRQs to ensures that chk for pending work itself is atomic
+ ; (and we don't end up missing a NEED_RESCHED/SIGPENDING due to an
+ ; interim IRQ).
+ IRQ_DISABLE r10
+
+ ; Fast Path return to user mode if no pending work
+ GET_CURR_THR_INFO_FLAGS r9
+ and.f 0, r9, _TIF_WORK_MASK
+ bz .Lrestore_regs
+
+ ; --- (Slow Path #1) task preemption ---
+ bbit0 r9, TIF_NEED_RESCHED, .Lchk_pend_signals
+ mov blink, resume_user_mode_begin ; tail-call to U mode ret chks
+ j @schedule ; BTST+Bnz causes relo error in link
+
+.Lchk_pend_signals:
+ IRQ_ENABLE r10
+
+ ; --- (Slow Path #2) pending signal ---
+ mov r0, sp ; pt_regs for arg to do_signal()/do_notify_resume()
+
+ GET_CURR_THR_INFO_FLAGS r9
+ bbit0 r9, TIF_SIGPENDING, .Lchk_notify_resume
+
+ ; Normal Trap/IRQ entry only saves Scratch (caller-saved) regs
+ ; in pt_reg since the "C" ABI (kernel code) will automatically
+ ; save/restore callee-saved regs.
+ ;
+ ; However, here we need to explicitly save callee regs because
+ ; (i) If this signal causes coredump - full regfile needed
+ ; (ii) If signal is SIGTRAP/SIGSTOP, task is being traced thus
+ ; tracer might call PEEKUSR(CALLEE reg)
+ ;
+ ; NOTE: SP will grow up by size of CALLEE Reg-File
+ SAVE_CALLEE_SAVED_USER ; clobbers r12
+
+ ; save location of saved Callee Regs @ thread_struct->callee
+ GET_CURR_TASK_FIELD_PTR TASK_THREAD, r10
+ st sp, [r10, THREAD_CALLEE_REG]
+
+ bl @do_signal
+
+ ; Ideally we want to discard the Callee reg above, however if this was
+ ; a tracing signal, tracer could have done a POKEUSR(CALLEE reg)
+ RESTORE_CALLEE_SAVED_USER
+
+ b resume_user_mode_begin ; loop back to start of U mode ret
+
+ ; --- (Slow Path #3) notify_resume ---
+.Lchk_notify_resume:
+ btst r9, TIF_NOTIFY_RESUME
+ blnz @do_notify_resume
+ b resume_user_mode_begin ; unconditionally back to U mode ret chks
+ ; for single exit point from this block
+
+resume_kernel_mode:
+
+ ; Disable Interrupts from this point on
+ ; CONFIG_PREEMPT: This is a must for preempt_schedule_irq()
+ ; !CONFIG_PREEMPT: To ensure restore_regs is intr safe
+ IRQ_DISABLE r9
+
+#ifdef CONFIG_PREEMPT
+
+ ; Can't preempt if preemption disabled
+ GET_CURR_THR_INFO_FROM_SP r10
+ ld r8, [r10, THREAD_INFO_PREEMPT_COUNT]
+ brne r8, 0, .Lrestore_regs
+
+ ; check if this task's NEED_RESCHED flag set
+ ld r9, [r10, THREAD_INFO_FLAGS]
+ bbit0 r9, TIF_NEED_RESCHED, .Lrestore_regs
+
+ ; Invoke PREEMPTION
+ jl preempt_schedule_irq
+
+ ; preempt_schedule_irq() always returns with IRQ disabled
+#endif
+
+ b .Lrestore_regs
+
+##### DONT ADD CODE HERE - .Lrestore_regs actually follows in entry-<isa>.S
+