entry.s

ARM 嵌入式 系统 设计与实例开发 实验教材 二源码

/* $Id: entry.S,v 1.38 2002/01/16 15:15:30 bjornw Exp $
 *
 *  linux/arch/cris/entry.S
 *
 *  Copyright (C) 2000, 2001 Axis Communications AB
 *
 *  Authors:	Bjorn Wesen ([e-mail])
 *
 *  $Log: entry.S,v $
 *  Revision 1.38  2002/01/16 15:15:30  bjornw
 *  Use a C-code compatible watchdog reset when NICE_DOGGY is enabled
 *
 *  Revision 1.37  2001/12/07 17:03:55  bjornw
 *  Call a c-hook called watchdog_bite_hook instead of show_registers directly
 *
 *  Revision 1.36  2001/11/22 13:36:36  bjornw
 *  * In ret_from_intr, check regs->dccr for usermode reentrance instead of
 *    DCCR explicitely (because the latter might not reflect current reality)
 *  * In mmu_bus_fault, set $r9 _after_ calling the C-code instead of before
 *    since $r9 is call-clobbered and is potentially needed afterwards
 *
 *  Revision 1.35  2001/10/30 17:10:15  bjornw
 *  Add some syscalls
 *
 *  Revision 1.34  2001/10/01 14:45:03  bjornw
 *  Removed underscores and added register prefixes
 *
 *  Revision 1.33  2001/08/21 13:48:01  jonashg
 *  Added fix by HP to avoid oops when doing a hard_reset_now.
 *
 *  Revision 1.32  2001/08/14 04:32:02  hp
 *  In _resume, add comment why R9 is saved; don't sound like it's call-saved.
 *
 *  Revision 1.31  2001/07/25 16:07:42  bjornw
 *  softirq_active/mask -> softirq_pending only
 *
 *  Revision 1.30  2001/07/05 01:03:32  hp
 *  - include asm/errno.h to get ENOSYS.
 *  - Use ENOSYS, not local constant LENOSYS; tweak comments.
 *  - Explain why .include, not #include is used.
 *  - Make oops-register-dump if watchdog bits and it's not expected.
 *  - Don't jsr, use jump _hard_reset_now, and skip spurious nop.
 *  - Use correct section attribute for section .rodata.
 *  - Adjust sys_ni_syscall fill number.
 *
 *  Revision 1.29  2001/06/25 14:07:00  hp
 *  	Fix review comment.
 *  	* head.S: Use IO_STATE, IO_FIELD and IO_MASK constructs instead of
 *  	magic numbers.  Add comment that -traditional must not be used.
 *  	* entry.S (SYMBOL_NAME): Change redefinition to use ## concatenation.
 *  	Correct and update comment.
 *  	* Makefile (.S.o): Don't use -traditional.  Add comment why the
 *  	toplevel rule can't be used (now that there's a reason).
 *
 *  Revision 1.28  2001/06/21 02:00:40  hp
 *  	* entry.S: Include asm/unistd.h.
 *  	(_sys_call_table): Use section .rodata, not .data.
 *  	(_kernel_thread): Move from...
 *  	* process.c: ... here.
 *  	* entryoffsets.c (VAL): Break out from...
 *  	(OF): Use VAL.
 *  	(LCLONE_VM): New asmified value from CLONE_VM.
 *
 *  Revision 1.27  2001/05/29 11:25:27  markusl
 *  In case of "spurious_interrupt", do hard_reset instead of hanging system in a loop...
 *
 *  Revision 1.26  2001/05/15 15:46:03  bjornw
 *  Include config.h now that we use some CONFIG_ options
 *
 *  Revision 1.25  2001/05/15 05:38:47  hp
 *  Tweaked code in _ret_from_sys_call
 *
 *  Revision 1.24  2001/05/15 05:27:49  hp
 *  Save r9 in r1 over function call rather than on stack.
 *
 *  Revision 1.23  2001/05/15 05:10:00  hp
 *  Generate entry.S structure offsets from C
 *
 *  Revision 1.22  2001/04/17 13:58:39  orjanf
 *  * Renamed CONFIG_KGDB to CONFIG_ETRAX_KGDB.
 *
 *  Revision 1.21  2001/04/17 11:33:29  orjanf
 *  Updated according to review:
 *  * Included asm/sv_addr_ag.h to get macro for internal register.
 *  * Corrected comment regarding system call argument passing.
 *  * Removed comment about instruction being in a delay slot.
 *  * Added comment about SYMBOL_NAME macro.
 *
 *  Revision 1.20  2001/04/12 08:51:07  hp
 *  - Add entry for sys_fcntl64.  In fact copy last piece from i386 including ...
 *  - .rept to fill table to safe state with sys_ni_syscall.
 *
 *  Revision 1.19  2001/04/04 09:43:32  orjanf
 *  * Moved do_sigtrap from traps.c to entry.S.
 *  * LTASK_PID need not be global anymore.
 *
 *  Revision 1.18  2001/03/26 09:25:02  markusl
 *  Updated after review, should now handle USB interrupts correctly.
 *
 *  Revision 1.17  2001/03/21 16:12:55  bjornw
 *  * Always make room for the cpu status record in the frame, in order to
 *    use the same framelength and layout for both mmu busfaults and normal
 *    irqs. No need to check for the explicit CRIS_FRAME_FIXUP type anymore.
 *  * Fixed bug with using addq for popping the stack in the epilogue - it
 *    destroyed the flag register. Use instructions that don't affect the
 *    flag register instead.
 *  * Removed write to R_PORT_PA_DATA during spurious_interrupt
 *
 *  Revision 1.16  2001/03/20 19:43:02  bjornw
 *  * Get rid of esp0 setting
 *  * Give a 7th argument to a systemcall - the stackframe
 *
 *  Revision 1.15  2001/03/05 13:14:30  bjornw
 *  Spelling fix
 *
 *  Revision 1.14  2001/02/23 08:36:36  perf
 *  New ABI; syscallnr=r9, arg5=mof, arg6=srp.
 *  Corrected tracesys call check.
 *
 *  Revision 1.13  2001/02/15 08:40:55  perf
 *  H-P by way of perf;
 *  - (_system_call): Don't read system call function address into r1.
 *  - (RBFExit): There is no such thing as a null pop.  Adjust sp by addq.
 *  - (_system_call): Don't use r10 and don't save and restore it.
 *  - (THREAD_ESP0): New constant.
 *  - (_system_call): Inline set_esp0.
 *
 *  Revision 1.12  2001/01/31 17:56:25  orjanf
 *  Added definition of LTASK_PID and made it global.
 *
 *  Revision 1.11  2001/01/10 21:13:29  bjornw
 *  SYMBOL_NAME is defined incorrectly for the compiler options we currently use
 *
 *  Revision 1.10  2000/12/18 23:47:56  bjornw
 *  * Added syscall trace support (ptrace), completely untested of course
 *  * Removed redundant check for NULL entries in syscall_table
 *
 *  Revision 1.9  2000/11/21 16:40:51  bjornw
 *  * New frame type used when an SBFS frame needs to be popped without
 *    actually restarting the instruction
 *  * Enable interrupts in signal_return (they did so in x86, I hope it's a good
 *    idea)
 *
 *  Revision 1.8  2000/11/17 16:53:35  bjornw
 *  Added detection of frame-type in Rexit, so that mmu_bus_fault can
 *  use ret_from_intr in the return-path to check for signals (like SEGV)
 *  and other foul things that might have occurred during the fault.
 *
 *  Revision 1.7  2000/10/06 15:04:28  bjornw
 *  Include mof in register savings
 *
 *  Revision 1.6  2000/09/12 16:02:44  bjornw
 *  Linux-2.4.0-test7 derived updates
 *
 *  Revision 1.5  2000/08/17 15:35:15  bjornw
 *  2.4.0-test6 changed local_irq_count and friends API
 *
 *  Revision 1.4  2000/08/02 13:59:30  bjornw
 *  Removed olduname and uname from the syscall list
 *
 *  Revision 1.3  2000/07/31 13:32:58  bjornw
 *  * Export ret_from_intr
 *  * _resume updated (prev/last tjohejsan)
 *  * timer_interrupt obsolete
 *  * SIGSEGV detection in mmu_bus_fault temporarily disabled
 *
 *
 */

/*
 * 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/config.h>
#include <linux/linkage.h>
#include <linux/sys.h>
#include <asm/unistd.h>
#include <asm/sv_addr_ag.h>
#include <asm/errno.h>
	
	;; functions exported from this file
	
	.globl system_call
	.globl ret_from_intr
	.globl ret_from_sys_call
	.globl resume
	.globl multiple_interrupt
	.globl hwbreakpoint
	.globl IRQ1_interrupt
	.globl timer_interrupt
	.globl timer_shortcut
	.globl spurious_interrupt
	.globl hw_bp_trigs
	.globl mmu_bus_fault
	.globl do_sigtrap
	.globl gdb_handle_breakpoint
			
	.globl sys_call_table
	
	;; Get values and offsets into various structs.  The file isn't
	;; suitable for consumption by the preprocessor, so don't use
	;; #include.
	.include "entryoffsets.s"

	;; process bits for ptrace.  FIXME: Should be in a header file.

PT_TRACESYS_BIT	  = 1

	;; below are various parts of system_call which are not in the fast-path
	
	;; handle software irqs
				
_handle_softirq:
	move.d	$r9, $r1
	jsr	do_softirq	; call the C routine for softirq handling
	move.d	$r1, $r9

	;; fall-through
	
ret_from_intr:
	;; check for resched only 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 + LDCCR], $r0; regs->dccr
	btstq	8, $r0		; U-flag
	bpl	_Rexit		; go back directly
	nop
	ba	_ret_with_reschedule  ; go back but check schedule and signals first 
	nop

_reschedule:
	;; keep r9 intact
	move.d	$r9, $r1
	jsr	schedule
	ba	ret_from_sys_call
	move.d	$r1, $r9

	;; return but call do_signal first
_signal_return:
	ei			; we can get here from an interrupt
	move.d	$r9, $r10	; do_signals syscall/irq param
	moveq	0, $r11		; oldset param - 0 in this case
	move.d	$sp, $r12	; another argument to do_signal (the regs param)
	jsr	do_signal	; arch/cris/kernel/signal.c
	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+LR10]	; 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+LTASK_PTRACE], $r0
	btstq	PT_TRACESYS_BIT, $r0
	bmi	_tracesys
	nop	

	;; check for sanity in the requested syscall number
	
	cmpu.w	NR_syscalls, $r9	
	bcc	ret_from_sys_call
	lslq	2, $r9		;  multiply by 4, in the delay slot

	;; as a bonus 7th parameter, we give the location on the stack
	;; of the register structure itself. some syscalls need this.

	push	$sp
	
	;; the parameter carrying registers r10, r11, r12 and 13 are intact.
	;; the fifth and sixth parameters (if any) was in mof and srp 
	;; respectively, and we need to put them on the stack.

	push	$srp
	push	$mof
	
	jsr	[$r9+sys_call_table]	; actually do the system call
	addq	3*4, $sp		; pop the mof, srp and regs parameters
	move.d	$r10, [$sp+LR10]	; save the return value

	moveq	1, $r9		; "parameter" to ret_from_sys_call to show it was a sys call
	
	;; fall through into ret_from_sys_call to return
	
ret_from_sys_call:
	;; r9 is a parameter - if 1, we came from a syscall, if 0, from an irq
		
	;; check if any bottom halves need service
	
	test.d	[irq_stat]	       ; softirq_pending
	bne	_handle_softirq
	nop

_ret_with_reschedule:
	;; first get the current task-struct pointer (see top for defs)

	move.d	$sp, $r0
	and.d	-8192, $r0	; THREAD_SIZE == 8192
	
	;; see if we want to reschedule into another process
	
	test.d	[$r0+LTASK_NEEDRESCHED]