/* 

   *  Copyright (C) 1999, 2000, 2002  Niibe Yutaka

   *  Copyright (C) 2003 - 2008  Paul Mundt

   *
   * This file is subject to the terms and conditions of the GNU General Public
   * License.  See the file "COPYING" in the main directory of this archive
   * for more details.
   *
   */
  
  ! NOTE:
  ! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
  ! to be jumped is too far, but it causes illegal slot exception.
  
  /*	
   * entry.S contains the system-call and fault low-level handling routines.
   * This also contains the timer-interrupt handler, as well as all interrupts
   * and faults that can result in a task-switch.
   *
   * NOTE: This code handles signal-recognition, which happens every time
   * after a timer-interrupt and after each system call.
   *
   * NOTE: This code uses a convention that instructions in the delay slot
   * of a transfer-control instruction are indented by an extra space, thus:
   *
   *    jmp	@k0	    ! control-transfer instruction
   *     ldc	k1, ssr     ! delay slot
   *
   * Stack layout in 'ret_from_syscall':
   * 	ptrace needs to have all regs on the stack.
   *	if the order here is changed, it needs to be
   *	updated in ptrace.c and ptrace.h
   *
   *	r0
   *      ...
   *	r15 = stack pointer
   *	spc
   *	pr
   *	ssr
   *	gbr
   *	mach
   *	macl
   *	syscall #
   *
   */

  #include <asm/dwarf.h>

  
  #if defined(CONFIG_PREEMPT)

  #  define preempt_stop()	cli ; TRACE_IRQS_OFF

  #else
  #  define preempt_stop()
  #  define resume_kernel		__restore_all
  #endif

  
  	.align	2
  ENTRY(exception_error)
  	!

  	TRACE_IRQS_ON

  	sti

  	mov.l	1f, r0

  	jmp	@r0
  	 nop

  	.align	2

  1:	.long	do_exception_error

  
  	.align	2
  ret_from_exception:

  	CFI_STARTPROC simple
  	CFI_DEF_CFA r14, 0
  	CFI_REL_OFFSET 17, 64

  	CFI_REL_OFFSET 15, 60

  	CFI_REL_OFFSET 14, 56

  	CFI_REL_OFFSET 13, 52
  	CFI_REL_OFFSET 12, 48
  	CFI_REL_OFFSET 11, 44
  	CFI_REL_OFFSET 10, 40
  	CFI_REL_OFFSET 9, 36
  	CFI_REL_OFFSET 8, 32

  	preempt_stop()
  ENTRY(ret_from_irq)
  	!
  	mov	#OFF_SR, r0
  	mov.l	@(r0,r15), r0	! get status register
  	shll	r0
  	shll	r0		! kernel space?
  	get_current_thread_info r8, r0
  	bt	resume_kernel	! Yes, it's from kernel, go back soon
  
  #ifdef CONFIG_PREEMPT
  	bra	resume_userspace
  	 nop
  ENTRY(resume_kernel)

  	cli

  	TRACE_IRQS_OFF

  	mov.l	@(TI_PRE_COUNT,r8), r0	! current_thread_info->preempt_count
  	tst	r0, r0
  	bf	noresched
  need_resched:
  	mov.l	@(TI_FLAGS,r8), r0	! current_thread_info->flags
  	tst	#_TIF_NEED_RESCHED, r0	! need_resched set?
  	bt	noresched
  
  	mov	#OFF_SR, r0
  	mov.l	@(r0,r15), r0		! get status register

  	shlr	r0
  	and	#(0xf0>>1), r0		! interrupts off (exception path)?
  	cmp/eq	#(0xf0>>1), r0

  	bt	noresched

  	mov.l	3f, r0

  	jsr	@r0			! call preempt_schedule_irq

  	 nop

  	bra	need_resched
  	 nop

  noresched:
  	bra	__restore_all
  	 nop
  
  	.align 2
  1:	.long	PREEMPT_ACTIVE
  2:	.long	schedule

  3:	.long	preempt_schedule_irq

  #endif
  
  ENTRY(resume_userspace)
  	! r8: current_thread_info
  	cli

  	TRACE_IRQS_OFF

  	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags

  	tst	#(_TIF_WORK_MASK & 0xff), r0

  	bt/s	__restore_all
  	 tst	#_TIF_NEED_RESCHED, r0
  
  	.align	2
  work_pending:
  	! r0: current_thread_info->flags
  	! r8: current_thread_info
  	! t:  result of "tst	#_TIF_NEED_RESCHED, r0"
  	bf/s	work_resched

  	 tst	#_TIF_SIGPENDING, r0

  work_notifysig:
  	bt/s	__restore_all
  	 mov	r15, r4
  	mov	r12, r5		! set arg1(save_r0)
  	mov	r0, r6

  	sti

  	mov.l	2f, r1
  	mov.l	3f, r0
  	jmp	@r1
  	 lds	r0, pr
  work_resched:

  	mov.l	1f, r1
  	jsr	@r1				! schedule
  	 nop
  	cli

  	TRACE_IRQS_OFF

  	!
  	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags

  	tst	#(_TIF_WORK_MASK & 0xff), r0

  	bt	__restore_all
  	bra	work_pending
  	 tst	#_TIF_NEED_RESCHED, r0
  
  	.align	2
  1:	.long	schedule
  2:	.long	do_notify_resume

  3:	.long	resume_userspace

  
  	.align	2
  syscall_exit_work:
  	! r0: current_thread_info->flags
  	! r8: current_thread_info

  	tst	#(_TIF_WORK_SYSCALL_MASK & 0xff), r0

  	bt/s	work_pending
  	 tst	#_TIF_NEED_RESCHED, r0

  	TRACE_IRQS_ON

  	sti

  	mov	r15, r4

  	mov.l	8f, r0			! do_syscall_trace_leave

  	jsr	@r0
  	 nop
  	bra	resume_userspace
  	 nop
  
  	.align	2
  syscall_trace_entry:
  	!                     	Yes it is traced.

  	mov     r15, r4

  	mov.l	7f, r11		! Call do_syscall_trace_enter which notifies

  	jsr	@r11	    	! superior (will chomp R[0-7])
  	 nop

  	mov.l	r0, @(OFF_R0,r15)	! Save return value

  	!			Reload R0-R4 from kernel stack, where the
  	!   	    	    	parent may have modified them using
  	!   	    	    	ptrace(POKEUSR).  (Note that R0-R2 are
  	!   	    	    	used by the system call handler directly
  	!   	    	    	from the kernel stack anyway, so don't need
  	!   	    	    	to be reloaded here.)  This allows the parent
  	!   	    	    	to rewrite system calls and args on the fly.
  	mov.l	@(OFF_R4,r15), r4   ! arg0
  	mov.l	@(OFF_R5,r15), r5
  	mov.l	@(OFF_R6,r15), r6
  	mov.l	@(OFF_R7,r15), r7   ! arg3
  	mov.l	@(OFF_R3,r15), r3   ! syscall_nr

  	!

  	mov.l	2f, r10			! Number of syscalls
  	cmp/hs	r10, r3
  	bf	syscall_call
  	mov	#-ENOSYS, r0
  	bra	syscall_exit
  	 mov.l	r0, @(OFF_R0,r15)	! Return value
  
  __restore_all:

  	mov	#OFF_SR, r0
  	mov.l	@(r0,r15), r0	! get status register
  
  	shlr2	r0
  	and	#0x3c, r0
  	cmp/eq	#0x3c, r0
  	bt	1f
  	TRACE_IRQS_ON
  	bra	2f
  	 nop
  1:
  	TRACE_IRQS_OFF
  2:
  	mov.l	3f, r0

  	jmp	@r0
  	 nop
  
  	.align	2

  3:	.long	restore_all

  	.align	2

  syscall_badsys:			! Bad syscall number

  	get_current_thread_info r8, r0

  	mov	#-ENOSYS, r0
  	bra	resume_userspace
  	 mov.l	r0, @(OFF_R0,r15)	! Return value

  
  /*
   * The main debug trap handler.
   *
   * r8=TRA (not the trap number!)
   *
   * Note: This assumes that the trapa value is left in its original
   * form (without the shlr2 shift) so the calculation for the jump
   * call table offset remains a simple in place mask.
   */
  debug_trap:
  	mov	r8, r0
  	and	#(0xf << 2), r0
  	mov.l	1f, r8
  	add	r0, r8
  	mov.l	@r8, r8

  	jsr	@r8
  	 nop
  	bra	__restore_all

  	 nop

  	CFI_ENDPROC

  
  	.align	2
  1:	.long	debug_trap_table

  /*
   * Syscall interface:
   *
   *	Syscall #: R3
   *	Arguments #0 to #3: R4--R7
   *	Arguments #4 to #6: R0, R1, R2

   *	TRA: (number of arguments + ABI revision) x 4

   *
   * This code also handles delegating other traps to the BIOS/gdb stub
   * according to:
   *
   * Trap number

   * (TRA>>2)	Purpose
   * --------	-------
   * 0x00-0x0f	original SH-3/4 syscall ABI (not in general use).
   * 0x10-0x1f	general SH-3/4 syscall ABI.
   * 0x20-0x2f	syscall ABI for SH-2 parts.
   * 0x30-0x3f	debug traps used by the kernel.
   * 0x40-0xff	Not supported by all parts, so left unhandled.

   *
   * Note: When we're first called, the TRA value must be shifted
   * right 2 bits in order to get the value that was used as the "trapa"
   * argument.
   */
  
  	.align	2
  	.globl	ret_from_fork
  ret_from_fork:
  	mov.l	1f, r8
  	jsr	@r8
  	 mov	r0, r4
  	bra	syscall_exit
  	 nop
  	.align	2
  1:	.long	schedule_tail

  
  /*
   * The poorly named main trapa decode and dispatch routine, for
   * system calls and debug traps through their respective jump tables.
   */

  ENTRY(system_call)

  	setup_frame_reg

  #if !defined(CONFIG_CPU_SH2)
  	mov.l	1f, r9
  	mov.l	@r9, r8		! Read from TRA (Trap Address) Register
  #endif

  
  	mov	#OFF_TRA, r10
  	add	r15, r10
  	mov.l	r8, @r10		! set TRA value to tra

  	/*
  	 * Check the trap type
  	 */
  	mov	#((0x20 << 2) - 1), r9

  	cmp/hi	r9, r8

  	bt/s	debug_trap		! it's a debug trap..

  	 nop

  	TRACE_IRQS_ON

  	sti

  	!

  	get_current_thread_info r8, r10

  	mov.l	@(TI_FLAGS,r8), r8

  	mov	#(_TIF_WORK_SYSCALL_MASK & 0xff), r10
  	mov	#(_TIF_WORK_SYSCALL_MASK >> 8), r9

  	tst	r10, r8

  	shll8	r9
  	bf	syscall_trace_entry
  	tst	r9, r8

  	bf	syscall_trace_entry
  	!

  	mov.l	2f, r8			! Number of syscalls
  	cmp/hs	r8, r3
  	bt	syscall_badsys
  	!

  syscall_call:

  	shll2	r3		! x4

  	mov.l	3f, r8		! Load the address of sys_call_table

  	add	r8, r3
  	mov.l	@r3, r8

  	jsr	@r8	    	! jump to specific syscall handler
  	 nop
  	mov.l	@(OFF_R0,r15), r12		! save r0
  	mov.l	r0, @(OFF_R0,r15)		! save the return value
  	!
  syscall_exit:
  	cli

  	TRACE_IRQS_OFF

  	!
  	get_current_thread_info r8, r0
  	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags

  	tst	#(_TIF_ALLWORK_MASK & 0xff), r0
  	mov	#(_TIF_ALLWORK_MASK >> 8), r1
  	bf	syscall_exit_work
  	shlr8	r0
  	tst	r0, r1

  	bf	syscall_exit_work
  	bra	__restore_all
  	 nop
  	.align	2
  #if !defined(CONFIG_CPU_SH2)
  1:	.long	TRA
  #endif
  2:	.long	NR_syscalls
  3:	.long	sys_call_table

  7:	.long	do_syscall_trace_enter
  8:	.long	do_syscall_trace_leave