arch/sh/kernel/entry-common.S - maze/linux - Git at Google

 /*
  *  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 #
  *
  */

 #if defined(CONFIG_PREEMPT)
 #  define preempt_stop()	cli
 #else
 #  define preempt_stop()
 #  define resume_kernel		__restore_all
 #endif


 	.align	2
 ENTRY(exception_error)
 	!
 #ifdef CONFIG_TRACE_IRQFLAGS
 	mov.l	2f, r0
 	jsr	@r0
 	 nop
 #endif
 	sti
 	mov.l	1f, r0
 	jmp	@r0
 	 nop

 	.align	2
 1:	.long	do_exception_error
 #ifdef CONFIG_TRACE_IRQFLAGS
 2:	.long	trace_hardirqs_on
 #endif

 	.align	2
 ret_from_exception:
 	preempt_stop()
 #ifdef CONFIG_TRACE_IRQFLAGS
 	mov.l	4f, r0
 	jsr	@r0
 	 nop
 #endif
 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
 	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
 	and	#0xf0, r0		! interrupts off (exception path)?
 	cmp/eq	#0xf0, 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
 #ifdef CONFIG_TRACE_IRQFLAGS
 	mov.l	5f, r0
 	jsr	@r0
 	 nop
 #endif
 	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
 	tst	#_TIF_WORK_MASK, 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 | _TIF_RESTORE_SIGMASK), r0
 work_notifysig:
 	bt/s	__restore_all
 	 mov	r15, r4
 	mov	r12, r5		! set arg1(save_r0)
 	mov	r0, r6
 	mov.l	2f, r1
 	mov.l	3f, r0
 	jmp	@r1
 	 lds	r0, pr
 work_resched:
 	mov.l	1f, r1
 	jsr	@r1				! schedule
 	 nop
 	cli
 #ifdef CONFIG_TRACE_IRQFLAGS
 	mov.l	5f, r0
 	jsr	@r0
 	 nop
 #endif
 	!
 	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
 	tst	#_TIF_WORK_MASK, 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
 #ifdef CONFIG_TRACE_IRQFLAGS
 4:	.long	trace_hardirqs_on
 5:	.long	trace_hardirqs_off
 #endif

 	.align	2
 syscall_exit_work:
 	! r0: current_thread_info->flags
 	! r8: current_thread_info
 	tst	#_TIF_WORK_SYSCALL_MASK, r0
 	bt/s	work_pending
 	 tst	#_TIF_NEED_RESCHED, r0
 #ifdef CONFIG_TRACE_IRQFLAGS
 	mov.l	5f, r0
 	jsr	@r0
 	 nop
 #endif
 	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.l	1f, r0
 	jmp	@r0
 	 nop

 	.align	2
 1:	.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

 	.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)
 #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

 #ifdef CONFIG_TRACE_IRQFLAGS
 	mov.l	5f, r10
 	jsr	@r10
 	 nop
 #endif
 	sti

 	!
 	get_current_thread_info r8, r10
 	mov.l	@(TI_FLAGS,r8), r8
 	mov	#_TIF_WORK_SYSCALL_MASK, r10
 	tst	r10, 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
 #ifdef CONFIG_TRACE_IRQFLAGS
 	mov.l	6f, r0
 	jsr	@r0
 	 nop
 #endif
 	!
 	get_current_thread_info r8, r0
 	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
 	tst	#_TIF_ALLWORK_MASK, r0
 	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
 #ifdef CONFIG_TRACE_IRQFLAGS
 5:	.long	trace_hardirqs_on
 6:	.long	trace_hardirqs_off
 #endif
 7:	.long	do_syscall_trace_enter
 8:	.long	do_syscall_trace_leave
	/*
	* 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 #
	*
	*/

	#if defined(CONFIG_PREEMPT)
	# define preempt_stop() cli
	#else
	# define preempt_stop()
	# define resume_kernel __restore_all
	#endif


	.align 2
	ENTRY(exception_error)
	!
	#ifdef CONFIG_TRACE_IRQFLAGS
	mov.l 2f, r0
	jsr @r0
	nop
	#endif
	sti
	mov.l 1f, r0
	jmp @r0
	nop

	.align 2
	1: .long do_exception_error
	#ifdef CONFIG_TRACE_IRQFLAGS
	2: .long trace_hardirqs_on
	#endif

	.align 2
	ret_from_exception:
	preempt_stop()
	#ifdef CONFIG_TRACE_IRQFLAGS
	mov.l 4f, r0
	jsr @r0
	nop
	#endif
	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
	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
	and #0xf0, r0 ! interrupts off (exception path)?
	cmp/eq #0xf0, 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
	#ifdef CONFIG_TRACE_IRQFLAGS
	mov.l 5f, r0
	jsr @r0
	nop
	#endif
	mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
	tst #_TIF_WORK_MASK, 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 \| _TIF_RESTORE_SIGMASK), r0
	work_notifysig:
	bt/s __restore_all
	mov r15, r4
	mov r12, r5 ! set arg1(save_r0)
	mov r0, r6
	mov.l 2f, r1
	mov.l 3f, r0
	jmp @r1
	lds r0, pr
	work_resched:
	mov.l 1f, r1
	jsr @r1 ! schedule
	nop
	cli
	#ifdef CONFIG_TRACE_IRQFLAGS
	mov.l 5f, r0
	jsr @r0
	nop
	#endif
	!
	mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
	tst #_TIF_WORK_MASK, 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
	#ifdef CONFIG_TRACE_IRQFLAGS
	4: .long trace_hardirqs_on
	5: .long trace_hardirqs_off
	#endif

	.align 2
	syscall_exit_work:
	! r0: current_thread_info->flags
	! r8: current_thread_info
	tst #_TIF_WORK_SYSCALL_MASK, r0
	bt/s work_pending
	tst #_TIF_NEED_RESCHED, r0
	#ifdef CONFIG_TRACE_IRQFLAGS
	mov.l 5f, r0
	jsr @r0
	nop
	#endif
	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.l 1f, r0
	jmp @r0
	nop

	.align 2
	1: .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

	.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)
	#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

	#ifdef CONFIG_TRACE_IRQFLAGS
	mov.l 5f, r10
	jsr @r10
	nop
	#endif
	sti

	!
	get_current_thread_info r8, r10
	mov.l @(TI_FLAGS,r8), r8
	mov #_TIF_WORK_SYSCALL_MASK, r10
	tst r10, 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
	#ifdef CONFIG_TRACE_IRQFLAGS
	mov.l 6f, r0
	jsr @r0
	nop
	#endif
	!
	get_current_thread_info r8, r0
	mov.l @(TI_FLAGS,r8), r0 ! current_thread_info->flags
	tst #_TIF_ALLWORK_MASK, r0
	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
	#ifdef CONFIG_TRACE_IRQFLAGS
	5: .long trace_hardirqs_on
	6: .long trace_hardirqs_off
	#endif
	7: .long do_syscall_trace_enter
	8: .long do_syscall_trace_leave