path: root/arch/cris/arch-v10/kernel/entry.S

/*
 *  linux/arch/cris/entry.S
 *
 *  Copyright (C) 2000, 2001, 2002 Axis Communications AB
 *
 *  Authors:	Bjorn Wesen (bjornw@axis.com)
 */

/*
 * entry.S contains the system-call and fault low-level handling routines.
 *
 * NOTE: This code handles signal-recognition, which happens every time
 * after a timer-interrupt and after each system call.
 *
 * Stack layout in 'ret_from_system_call':
 * 	ptrace needs to have all regs on the stack.
 *	if the order here is changed, it needs to be 
 *	updated in fork.c:copy_process, signal.c:do_signal,
 *	ptrace.c and ptrace.h
 *
 */

#include <linux/linkage.h>
#include <linux/sys.h>
#include <asm/unistd.h>
#include <arch/sv_addr_ag.h>
#include <asm/errno.h>
#include <asm/thread_info.h>
#include <asm/asm-offsets.h>
#include <asm/page.h>
#include <asm/pgtable.h>

	;; functions exported from this file
	
	.globl system_call
	.globl ret_from_intr
	.globl ret_from_fork
	.globl resume
	.globl multiple_interrupt
	.globl hwbreakpoint
	.globl IRQ1_interrupt
	.globl spurious_interrupt
	.globl hw_bp_trigs
	.globl mmu_bus_fault
	.globl do_sigtrap
	.globl gdb_handle_breakpoint
	.globl sys_call_table
	
	;; below are various parts of system_call which are not in the fast-path
	
#ifdef CONFIG_PREEMPT	
	; Check if preemptive kernel scheduling should be done
_resume_kernel:
	di
	; Load current task struct
	movs.w	-8192, $r0	;  THREAD_SIZE = 8192
	and.d	$sp, $r0
	move.d	[$r0+TI_preempt_count], $r10	;  Preemption disabled?
	bne	_Rexit
	nop
_need_resched:
	move.d	[$r0+TI_flags], $r10
	btstq	TIF_NEED_RESCHED, $r10	; Check if need_resched is set
	bpl	_Rexit
	nop
	; Ok, lets's do some preemptive kernel scheduling
	jsr	preempt_schedule_irq
	; Load new task struct
	movs.w	-8192, $r0	;  THREAD_SIZE = 8192
	and.d	$sp, $r0
	; One more time (with new task)
	ba	_need_resched
	nop
#else
#define _resume_kernel _Rexit
#endif	

	; Called at exit from fork. schedule_tail must be called to drop
	; spinlock if CONFIG_PREEMPT
ret_from_fork:
	jsr schedule_tail
	ba  ret_from_sys_call
	nop
		
ret_from_intr:
	;; check for resched if preemptive kernel or if we're going back to user-mode 
	;; this test matches the user_regs(regs) macro
	;; we cannot simply test $dccr, because that does not necessarily
	;; reflect what mode we'll return into.
	
	move.d	[$sp + PT_dccr], $r0; regs->dccr
	btstq	8, $r0		; U-flag
	bpl     _resume_kernel
	; Note that di below is in delay slot 
	
_resume_userspace:
	di			; so need_resched and sigpending don't change

	movs.w	-8192, $r0	; THREAD_SIZE == 8192
	and.d	$sp, $r0

	move.d	[$r0+TI_flags], $r10	; current->work
	and.d	_TIF_WORK_MASK, $r10	; is there any work to be done on return
	bne	_work_pending
	nop
	ba	_Rexit
	nop
	
	;; The system_call is called by a BREAK instruction, which works like
	;; an interrupt call but it stores the return PC in BRP instead of IRP.
	;; Since we dont really want to have two epilogues (one for system calls
	;; and one for interrupts) we push the contents of BRP instead of IRP in the
	;; system call prologue, to make it look like an ordinary interrupt on the
	;; stackframe.
	;;
	;; Since we can't have system calls inside interrupts, it should not matter
	;; that we don't stack IRP.
	;; 
	;; In r9 we have the wanted syscall number. Arguments come in r10,r11,r12,r13,mof,srp
	;;
	;; This function looks on the _surface_ like spaghetti programming, but it's
	;; really designed so that the fast-path does not force cache-loading of non-used
	;; instructions. Only the non-common cases cause the outlined code to run..

system_call:
	;; stack-frame similar to the irq heads, which is reversed in ret_from_sys_call
	move	$brp,[$sp=$sp-16]; instruction pointer and room for a fake SBFS frame
	push	$srp
	push	$dccr
	push	$mof
	subq	14*4, $sp		; make room for r0-r13
	movem	$r13, [$sp]	; push r0-r13
	push	$r10		; push orig_r10
	clear.d [$sp=$sp-4]	; frametype == 0, normal stackframe
	
	movs.w	-ENOSYS, $r0
	move.d	$r0, [$sp+PT_r10]	; put the default return value in r10 in the frame

	;; check if this process is syscall-traced

	movs.w	-8192, $r0	; THREAD_SIZE == 8192
	and.d	$sp, $r0
	
	move.d	[$r0+TI_flags], $r0
	btstq   TIF_SYSCALL_TRACE, $r0
	bmi	_syscall_trace_entry
	nop	

_syscall_traced:	

	;; check for sanity i