entry.s

ARM 嵌入式 系统 设计与实例开发 实验教材 二源码

	bne	_reschedule
	nop

	;; see if we need to run signal checks (important that r9 is intact here)

	test.d	[$r0+LTASK_SIGPENDING]
	bne	_signal_return
	nop
	
_Rexit:
	;; this epilogue MUST match the prologues in multiple_interrupt, irq.h and ptregs.h
	pop	$r10		; frametype
	bne	_RBFexit	; was not CRIS_FRAME_NORMAL, handle otherwise
	addq	4, $sp		; skip orig_r10, in delayslot
	movem	[$sp+], $r13	; registers r0-r13
	pop	$mof		; multiply overflow register 
	pop	$dccr		; condition codes
	pop	$srp		; subroutine return pointer
	;; now we have a 4-word SBFS frame which we do not want to restore
	;; using RBF since it was not stacked with SBFS. instead we would like to
	;; just get the PC value to restart it with, and skip the rest of
	;; the frame.
	;; Also notice that it's important to use instructions here that
	;; keep the interrupts disabled (since we've already popped DCCR)
	move	[$sp=$sp+16], $p8; pop the SBFS frame from the sp
	jmpu	[$sp-16]	; return through the irp field in the sbfs frame

_RBFexit:
	movem	[$sp+], $r13	; registers r0-r13, in delay slot
	pop	$mof		; multiply overflow register 
	pop	$dccr		; condition codes
	pop	$srp		; subroutine return pointer
	rbf	[$sp+]		; return by popping the CPU status

_tracesys:
	;; this first invocation of syscall_trace _requires_ that
	;; LR10 in the frame contains -ENOSYS (as is set in the beginning
	;; of system_call).

	jsr	syscall_trace

	;; now we should more or less do the same things as in the system_call
	;; but since our argument regs got clobbered during syscall_trace and
	;; because syscall_trace might want to alter them, we need to reload them
	;; from the stack-frame as we use them.

	;; check for sanity in the requested syscall number

	move.d	[$sp+LR9], $r9
	movs.w	-ENOSYS, $r10
	cmpu.w	NR_syscalls, $r9	
	bcc	1f
	lslq	2, $r9		;  multiply by 4, in the delay slot

	;; read the system call vector entry into r9
	
	move.d	[$r9+sys_call_table], $r9

	;; restore r10, r11, r12, r13, mof and srp into the needed registers

	move.d	[$sp+LORIG_R10], $r10  ; LR10 is already filled with -ENOSYS.
	move.d	[$sp+LR11],      $r11
	move.d	[$sp+LR12],      $r12
	move.d	[$sp+LR13],      $r13
	move	[$sp+LMOF],      $mof
	move	[$sp+LSRP],      $srp

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

	push	$sp
	
	;; the fifth and sixth parameters needs to be put on the stack for
	;; the system call to find them

	push	$srp
	push	$mof

	jsr	$r9		; actually call the system-call
	addq	3*4, $sp	; pop the srp, mof and regs parameters

1:	move.d	$r10, [$sp+LR10]; save the return value

	;; second call of syscall_trace, to let it grab the results
		
	jsr	syscall_trace

	moveq	1, $r9		; "parameter" to ret_from_sys_call to show it was a sys call
	ba	ret_from_sys_call
	nop
		
	;; resume performs the actual task-switching, by switching stack pointers
	;; input arguments: r10 = prev, r11 = next, r12 = thread offset in task struct
	;; returns old current in r10
	;;
	;; TODO:  see the i386 version. The switch_to which calls resume in our version
	;;        could really be an inline asm of this.

resume:	
	push	$srp		         ; we keep the old/new PC on the stack 
	add.d	$r12, $r10		 ; r10 = current tasks tss
	move	$dccr, [$r10+LTHREAD_DCCR] ; save irq enable state
	di

	move	$usp, [$r10+LTHREAD_USP] ; save user-mode stackpointer
	
	;; See copy_thread for the reason why register R9 is saved.
	subq	10*4, $sp
	movem	$r9, [$sp]		 ; save non-scratch registers and R9.
	
	move.d	$sp, [$r10+LTHREAD_KSP]	 ; save the kernel stack pointer for the old task
	move.d	$sp, $r10		 ; return last running task in r10
	and.d   -8192, $r10	         ; get task ptr from stackpointer
	add.d	$r12, $r11		 ; find the new tasks tss
	move.d	[$r11+LTHREAD_KSP], $sp	 ; switch into the new stackframe by restoring kernel sp

	movem	[$sp+], $r9		 ; restore non-scratch registers and R9.

	move	[$r11+LTHREAD_USP], $usp ; restore user-mode stackpointer
	
	move	[$r11+LTHREAD_DCCR], $dccr ; restore irq enable status
	jump	[$sp+]		         ; restore PC

	;; This is the MMU bus fault handler.
	;; It needs to stack the CPU status and overall is different
	;; from the other interrupt handlers.

mmu_bus_fault:	
	sbfs	[$sp=$sp-16]	; push the internal CPU status
	;; the first longword in the sbfs frame was the interrupted PC
	;; which fits nicely with the "IRP" slot in pt_regs normally used to
	;; contain the return address. used by Oops to print kernel errors..
	push	$srp		; make a stackframe similar to pt_regs
	push	$dccr
	push	$mof
	di
	subq	14*4, $sp
	movem	$r13, [$sp]
	push	$r10		; dummy orig_r10
	moveq	1, $r10
	push	$r10		; frametype == 1, BUSFAULT frame type

	move.d	$sp, $r10	; pt_regs argument to handle_mmu_bus_fault
		
	jsr	handle_mmu_bus_fault  ; in arch/cris/mm/fault.c

	;; now we need to return through the normal path, we cannot just
	;; do the RBFexit since we might have killed off the running
	;; process due to a SEGV, scheduled due to a page blocking or
	;; whatever.

	moveq	0, $r9		; busfault is equivalent to an irq
		
	ba	ret_from_intr
	nop
		
	;; special handlers for breakpoint and NMI
#if 0			
hwbreakpoint:
	push	$dccr
	di
	push	$r10
	push	$r11
	push	$r12
	push	$r13
	clearf	b
	move	$brp,$r11
	move.d	[hw_bp_msg],$r10
	jsr	printk
	setf	b
	pop	$r13
	pop	$r12
	pop	$r11
	pop	$r10
	pop	$dccr
	retb
	nop
#else
hwbreakpoint:
	push	$dccr
	di
#if 1
	push	$r10
	push	$r11
	move.d	[hw_bp_trig_ptr],$r10
	move.d	[$r10],$r11
	cmp.d	42,$r11
	beq	1f
	nop
	move	$brp,$r11
	move.d	$r11,[$r10+]
	move.d	$r10,[hw_bp_trig_ptr]
1:	pop	$r11
	pop	$r10
#endif
	pop	$dccr
	retb
	nop
#endif
	
IRQ1_interrupt:

#if defined(CONFIG_ETRAX_WATCHDOG) && !defined(CONFIG_SVINTO_SIM)
;; If we receive a watchdog interrupt while it is not expected, then set
;; up a canonical frame and dump register contents before dying.

	;; this prologue MUST match the one in irq.h and the struct in ptregs.h!!!
	move	$brp,[$sp=$sp-16]; instruction pointer and room for a fake SBFS frame
	push	$srp
	push	$dccr
	push	$mof
	di
	subq	14*4, $sp
	movem	$r13, [$sp]
	push	$r10		; push orig_r10
	clear.d [$sp=$sp-4]	; frametype == 0, normal frame

;; We don't check that we actually were bit by the watchdog as opposed to
;; an external NMI, since there is currently no handler for external NMI.

;; Check if we're waiting for reset to happen, as signalled by
;; hard_reset_now setting cause_of_death to a magic value.  If so, just
;; get stuck until reset happens.
	.comm	cause_of_death, 4	;; Don't declare this anywhere.
	move.d	[cause_of_death], $r10
	cmp.d	0xbedead, $r10
_killed_by_death:
	beq	_killed_by_death
	nop

;; We'll see this in ksymoops dumps.
Watchdog_bite:

#ifdef CONFIG_ETRAX_WATCHDOG_NICE_DOGGY
	;; We just restart the watchdog here to be sure we dont get
	;; hit while printing the watchdogmsg below
	;; This restart is compatible with the rest of the C-code, so
	;; the C-code can keep restarting the watchdog after this point.
	;; The non-NICE_DOGGY code below though, disables the possibility
	;; to restart since it changes the watchdog key, to avoid any
	;; buggy loops etc. keeping the watchdog alive after this.
	jsr	reset_watchdog
#else
;; We need to extend the 3.3ms after the NMI at watchdog bite, so we have
;; time for an oops-dump over a 115k2 serial wire.  Another 100ms should do.

;; Change the watchdog key to an arbitrary 3-bit value and restart the
;; watchdog.
#define WD_INIT 2
	moveq	  IO_FIELD (R_WATCHDOG, key, WD_INIT), $r10
	move.d	R_WATCHDOG, $r11

	move.d	$r10, [$r11]
	moveq	  IO_FIELD (R_WATCHDOG, key,				\
			    IO_EXTRACT (R_WATCHDOG, key,		\
					IO_MASK (R_WATCHDOG, key))	\
			    ^ WD_INIT)					\
		| IO_STATE (R_WATCHDOG, enable, start), $r10
	move.d	$r10, [$r11]
#endif
	
;; Note that we don't do "setf m" here (or after two necessary NOPs),
;; since *not* doing that saves us from re-entrancy checks.  We don't want
;; to get here again due to possible subsequent NMIs; we want the watchdog
;; to reset us.

	move.d	_watchdogmsg,$r10
	jsr	printk

	move.d	$sp, $r10
	jsr	watchdog_bite_hook

;; This nop is here so we see the "Watchdog_bite" label in ksymoops dumps
;; rather than "spurious_interrupt".
	nop
;; At this point we drop down into spurious_interrupt, which will do a
;; hard reset.

	.section .rodata,"a"
_watchdogmsg:
	.ascii	"Oops: bitten by watchdog\n\0"
	.previous

#endif /* CONFIG_ETRAX_WATCHDOG and not CONFIG_SVINTO_SIM */

spurious_interrupt:	
	di
	jump hard_reset_now

	;; this handles the case when multiple interrupts arrive at the same time
	;; we jump to the first set interrupt bit in a priority fashion
	;; the hardware will call the unserved interrupts after the handler finishes
	
multiple_interrupt:
	;; this prologue MUST match the one in irq.h and the struct in ptregs.h!!!
	move	$irp,[$sp=$sp-16]; instruction pointer and room for a fake SBFS frame
	push	$srp
	push	$dccr
	push	$mof
	di
	subq	14*4, $sp
	movem	$r13, [$sp]
	push	$r10		; push orig_r10
	clear.d [$sp=$sp-4]	; frametype == 0, normal frame
	
	move.d	irq_shortcuts + 8, $r1
	moveq	2, $r2		; first bit we care about is the timer0 irq
	move.d	[R_VECT_MASK_RD], $r0; read the irq bits that triggered the multiple irq
1:	
	btst	$r2, $r0	; check for the irq given by bit r2
	bmi	_do_shortcut	; actually do the shortcut
	nop
	addq	1, $r2		; next vector bit
	addq	4, $r1		; next vector
	cmp.b	32, $r2
	bne	1b	; process all irq's up to and including number 31
	nop
	
	;; strange, we didn't get any set vector bits.. oh well, just return
	
	ba	_Rexit
	nop

_do_shortcut:
	test.d	[$r1]
	beq	_Rexit
	nop
	jump	[$r1]		; jump to the irq handlers shortcut

do_sigtrap:
	;; 
	;; SIGTRAP the process that executed the break instruction.
	;; Make a frame that Rexit in entry.S expects.
	;;
	move	$brp, [$sp=$sp-16]	; Push BRP while faking a cpu status record.
	push	$srp			; Push subroutine return pointer.
	push	$dccr			; Push condition codes.
	push	$mof			; Push multiply overflow reg.
	di				; Need to disable irq's at this point.
	subq	14*4, $sp		; Make room for r0-r13.
	movem	$r13, [$sp]		; Push the r0-r13 registers.
	push	$r10			; Push orig_r10.
	clear.d	[$sp=$sp-4]		; Frametype - this is a normal stackframe.