entry.s

linux 内核源代码

/*
 *  linux/arch/m68knommu/platform/5307/entry.S
 *
 *  Copyright (C) 1999-2007, Greg Ungerer ([e-mail])
 *  Copyright (C) 1998  D. Jeff Dionne <[e-mail]>,
 *                      Kenneth Albanowski <[e-mail]>,
 *  Copyright (C) 2000  Lineo Inc. (www.lineo.com)
 *  Copyright (C) 2004-2006  Macq Electronique SA. (www.macqel.com)
 *
 * Based on:
 *
 *  linux/arch/m68k/kernel/entry.S
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file README.legal in the main directory of this archive
 * for more details.
 *
 * Linux/m68k support by Hamish Macdonald
 *
 * 68060 fixes by Jesper Skov
 * ColdFire support by Greg Ungerer ([e-mail])
 * 5307 fixes by David W. Miller
 * linux 2.4 support David McCullough <[e-mail]>
 * Bug, speed and maintainability fixes by Philippe De Muyter <[e-mail]>
 */

#include <linux/sys.h>
#include <linux/linkage.h>
#include <asm/unistd.h>
#include <asm/thread_info.h>
#include <asm/errno.h>
#include <asm/setup.h>
#include <asm/segment.h>
#include <asm/asm-offsets.h>
#include <asm/entry.h>

.bss

sw_ksp:
.long	0

sw_usp:
.long	0

.text

.globl system_call
.globl resume
.globl ret_from_exception
.globl ret_from_signal
.globl sys_call_table
.globl ret_from_interrupt
.globl inthandler
.globl fasthandler

enosys:
	mov.l	#sys_ni_syscall,%d3
	bra	1f

ENTRY(system_call)
	SAVE_ALL
	move	#0x2000,%sr		/* enable intrs again */

	cmpl	#NR_syscalls,%d0
	jcc	enosys
	lea	sys_call_table,%a0
	lsll	#2,%d0			/* movel %a0@(%d0:l:4),%d3 */
	movel	%a0@(%d0),%d3
	jeq	enosys

1:
	movel	%sp,%d2			/* get thread_info pointer */
	andl	#-THREAD_SIZE,%d2	/* at start of kernel stack */
	movel	%d2,%a0
	movel	%a0@,%a1		/* save top of frame */
	movel	%sp,%a1@(TASK_THREAD+THREAD_ESP0)
	btst	#(TIF_SYSCALL_TRACE%8),%a0@(TI_FLAGS+(31-TIF_SYSCALL_TRACE)/8)
	bnes	1f

	movel	%d3,%a0
	jbsr	%a0@
	movel	%d0,%sp@(PT_D0)		/* save the return value */
	jra	ret_from_exception
1:
	movel	#-ENOSYS,%d2		/* strace needs -ENOSYS in PT_D0 */
	movel	%d2,PT_D0(%sp)		/* on syscall entry */
	subql	#4,%sp
	SAVE_SWITCH_STACK
	jbsr	syscall_trace
	RESTORE_SWITCH_STACK
	addql	#4,%sp
	movel	%d3,%a0
	jbsr	%a0@
	movel	%d0,%sp@(PT_D0)		/* save the return value */
	subql	#4,%sp			/* dummy return address */
	SAVE_SWITCH_STACK
	jbsr	syscall_trace

ret_from_signal:
	RESTORE_SWITCH_STACK
	addql	#4,%sp

ret_from_exception:
	btst	#5,%sp@(PT_SR)		/* check if returning to kernel */
	jeq	Luser_return		/* if so, skip resched, signals */

Lkernel_return:
	moveml	%sp@,%d1-%d5/%a0-%a2
	lea	%sp@(32),%sp		/* space for 8 regs */
	movel	%sp@+,%d0
	addql	#4,%sp			/* orig d0 */
	addl	%sp@+,%sp		/* stk adj */
	rte

Luser_return:
	movel	%sp,%d1			/* get thread_info pointer */
	andl	#-THREAD_SIZE,%d1	/* at base of kernel stack */
	movel	%d1,%a0
	movel	%a0@(TI_FLAGS),%d1	/* get thread_info->flags */
	andl	#_TIF_WORK_MASK,%d1
	jne	Lwork_to_do		/* still work to do */

Lreturn:
	move	#0x2700,%sr		/* disable intrs */
	movel	sw_usp,%a0		/* get usp */
	movel	%sp@(PT_PC),%a0@-	/* copy exception program counter */
	movel	%sp@(PT_FORMATVEC),%a0@-/* copy exception format/vector/sr */
	moveml	%sp@,%d1-%d5/%a0-%a2
	lea	%sp@(32),%sp		/* space for 8 regs */
	movel	%sp@+,%d0
	addql	#4,%sp			/* orig d0 */
	addl	%sp@+,%sp		/* stk adj */
	addql	#8,%sp			/* remove exception */
	movel	%sp,sw_ksp		/* save ksp */
	subql	#8,sw_usp		/* set exception */
	movel	sw_usp,%sp		/* restore usp */
	rte

Lwork_to_do:
	movel	%a0@(TI_FLAGS),%d1	/* get thread_info->flags */
	btst	#TIF_NEED_RESCHED,%d1
	jne	reschedule

	/* GERG: do we need something here for TRACEing?? */

Lsignal_return:
	subql	#4,%sp			/* dummy return address */
	SAVE_SWITCH_STACK
	pea	%sp@(SWITCH_STACK_SIZE)
	clrl	%sp@-
	jsr	do_signal
	addql	#8,%sp
	RESTORE_SWITCH_STACK
	addql	#4,%sp
	jmp	Lreturn

/*
 * This is the generic interrupt handler (for all hardware interrupt
 * sources). Calls upto high level code to do all the work.
 */
ENTRY(inthandler)
	SAVE_ALL
	moveq	#-1,%d0
	movel	%d0,%sp@(PT_ORIG_D0)

	movew	%sp@(PT_FORMATVEC),%d0	/* put exception # in d0 */
	andl	#0x03fc,%d0		/* mask out vector only */

	movel	%sp,%sp@-		/* push regs arg */
	lsrl	#2,%d0			/* calculate real vector # */
	movel	%d0,%sp@-		/* push vector number */
	jbsr	do_IRQ			/* call high level irq handler */
	lea	%sp@(8),%sp		/* pop args off stack */

	bra	ret_from_interrupt	/* this was fallthrough */

/*
 * This is the fast interrupt handler (for certain hardware interrupt
 * sources). Unlike the normal interrupt handler it just uses the
 * current stack (doesn't care if it is user or kernel). It also
 * doesn't bother doing the bottom half handlers.
 */
ENTRY(fasthandler)
	SAVE_LOCAL

	movew	%sp@(PT_FORMATVEC),%d0
	andl	#0x03fc,%d0		/* mask out vector only */

	movel	%sp,%sp@-		/* push regs arg */
	lsrl	#2,%d0			/* calculate real vector # */
	movel	%d0,%sp@-		/* push vector number */
	jbsr	do_IRQ			/* call high level irq handler */
	lea	%sp@(8),%sp		/* pop args off stack */

	RESTORE_LOCAL

ENTRY(ret_from_interrupt)
	jeq	2f
1:
	RESTORE_ALL
2:
	moveb	%sp@(PT_SR),%d0
	andl	#0x7,%d0
	jhi	1b

	/* check if we need to do software interrupts */
	movel	irq_stat+CPUSTAT_SOFTIRQ_PENDING,%d0
	jeq	ret_from_exception

	pea	ret_from_exception
	jmp	do_softirq

/*
 * Beware - when entering resume, prev (the current task) is
 * in a0, next (the new task) is in a1,so don't change these
 * registers until their contents are no longer needed.
 * This is always called in supervisor mode, so don't bother to save
 * and restore sr; user's process sr is actually in the stack.
 */
ENTRY(resume)
	movel	%a0, %d1			/* get prev thread in d1 */

	movel	sw_usp,%d0			/* save usp */
	movel	%d0,%a0@(TASK_THREAD+THREAD_USP)

	SAVE_SWITCH_STACK
	movel	%sp,%a0@(TASK_THREAD+THREAD_KSP) /* save kernel stack pointer */
	movel	%a1@(TASK_THREAD+THREAD_KSP),%sp /* restore new thread stack */
	RESTORE_SWITCH_STACK

	movel	%a1@(TASK_THREAD+THREAD_USP),%a0 /* restore thread user stack */
	movel	%a0, sw_usp
	rts