1/* $Id: entry-common.S,v 1.1.1.1 2007/08/03 18:52:16 Exp $
2 *
3 *  linux/arch/sh/entry.S
4 *
5 *  Copyright (C) 1999, 2000, 2002  Niibe Yutaka
6 *  Copyright (C) 2003  Paul Mundt
7 *
8 * This file is subject to the terms and conditions of the GNU General Public
9 * License.  See the file "COPYING" in the main directory of this archive
10 * for more details.
11 *
12 */
13
14! NOTE:
15! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
16! to be jumped is too far, but it causes illegal slot exception.
17
18/*
19 * entry.S contains the system-call and fault low-level handling routines.
20 * This also contains the timer-interrupt handler, as well as all interrupts
21 * and faults that can result in a task-switch.
22 *
23 * NOTE: This code handles signal-recognition, which happens every time
24 * after a timer-interrupt and after each system call.
25 *
26 * NOTE: This code uses a convention that instructions in the delay slot
27 * of a transfer-control instruction are indented by an extra space, thus:
28 *
29 *    jmp	@k0	    ! control-transfer instruction
30 *     ldc	k1, ssr     ! delay slot
31 *
32 * Stack layout in 'ret_from_syscall':
33 * 	ptrace needs to have all regs on the stack.
34 *	if the order here is changed, it needs to be
35 *	updated in ptrace.c and ptrace.h
36 *
37 *	r0
38 *      ...
39 *	r15 = stack pointer
40 *	spc
41 *	pr
42 *	ssr
43 *	gbr
44 *	mach
45 *	macl
46 *	syscall #
47 *
48 */
49
50#if defined(CONFIG_PREEMPT)
51#  define preempt_stop()	cli
52#else
53#  define preempt_stop()
54#  define resume_kernel		__restore_all
55#endif
56
57
58	.align	2
59ENTRY(exception_error)
60	!
61#ifdef CONFIG_TRACE_IRQFLAGS
62	mov.l	2f, r0
63	jsr	@r0
64	 nop
65#endif
66	sti
67	mov.l	1f, r0
68	jmp	@r0
69	 nop
70
71	.align	2
721:	.long	do_exception_error
73#ifdef CONFIG_TRACE_IRQFLAGS
742:	.long	trace_hardirqs_on
75#endif
76
77	.align	2
78ret_from_exception:
79	preempt_stop()
80#ifdef CONFIG_TRACE_IRQFLAGS
81	mov.l	4f, r0
82	jsr	@r0
83	 nop
84#endif
85ENTRY(ret_from_irq)
86	!
87	mov	#OFF_SR, r0
88	mov.l	@(r0,r15), r0	! get status register
89	shll	r0
90	shll	r0		! kernel space?
91	get_current_thread_info r8, r0
92	bt	resume_kernel	! Yes, it's from kernel, go back soon
93
94#ifdef CONFIG_PREEMPT
95	bra	resume_userspace
96	 nop
97ENTRY(resume_kernel)
98	mov.l	@(TI_PRE_COUNT,r8), r0	! current_thread_info->preempt_count
99	tst	r0, r0
100	bf	noresched
101need_resched:
102	mov.l	@(TI_FLAGS,r8), r0	! current_thread_info->flags
103	tst	#_TIF_NEED_RESCHED, r0	! need_resched set?
104	bt	noresched
105
106	mov	#OFF_SR, r0
107	mov.l	@(r0,r15), r0		! get status register
108	and	#0xf0, r0		! interrupts off (exception path)?
109	cmp/eq	#0xf0, r0
110	bt	noresched
111
112	mov.l	1f, r0
113	mov.l	r0, @(TI_PRE_COUNT,r8)
114
115#ifdef CONFIG_TRACE_IRQFLAGS
116	mov.l	3f, r0
117	jsr	@r0
118	 nop
119#endif
120	sti
121	mov.l	2f, r0
122	jsr	@r0
123	 nop
124	mov	#0, r0
125	mov.l	r0, @(TI_PRE_COUNT,r8)
126	cli
127#ifdef CONFIG_TRACE_IRQFLAGS
128	mov.l	4f, r0
129	jsr	@r0
130	 nop
131#endif
132
133	bra	need_resched
134	 nop
135
136noresched:
137	bra	__restore_all
138	 nop
139
140	.align 2
1411:	.long	PREEMPT_ACTIVE
1422:	.long	schedule
143#ifdef CONFIG_TRACE_IRQFLAGS
1443:	.long	trace_hardirqs_on
1454:	.long	trace_hardirqs_off
146#endif
147#endif
148
149ENTRY(resume_userspace)
150	! r8: current_thread_info
151	cli
152#ifdef CONFIG_TRACE_IRQFLAGS
153	mov.l	5f, r0
154	jsr	@r0
155	 nop
156#endif
157	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
158	tst	#_TIF_WORK_MASK, r0
159	bt/s	__restore_all
160	 tst	#_TIF_NEED_RESCHED, r0
161
162	.align	2
163work_pending:
164	! r0: current_thread_info->flags
165	! r8: current_thread_info
166	! t:  result of "tst	#_TIF_NEED_RESCHED, r0"
167	bf/s	work_resched
168	 tst	#(_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK), r0
169work_notifysig:
170	bt/s	__restore_all
171	 mov	r15, r4
172	mov	r12, r5		! set arg1(save_r0)
173	mov	r0, r6
174	mov.l	2f, r1
175	mov.l	3f, r0
176	jmp	@r1
177	 lds	r0, pr
178work_resched:
179#ifndef CONFIG_PREEMPT
180	! gUSA handling
181	mov.l	@(OFF_SP,r15), r0	! get user space stack pointer
182	mov	r0, r1
183	shll	r0
184	bf/s	1f
185	 shll	r0
186	bf/s	1f
187	 mov	#OFF_PC, r0
188	! 				  SP >= 0xc0000000 : gUSA mark
189	mov.l	@(r0,r15), r2		! get user space PC (program counter)
190	mov.l	@(OFF_R0,r15), r3	! end point
191	cmp/hs	r3, r2			! r2 >= r3?
192	bt	1f
193	add	r3, r1			! rewind point #2
194	mov.l	r1, @(r0,r15)		! reset PC to rewind point #2
195	!
1961:
197#endif
198	mov.l	1f, r1
199	jsr	@r1				! schedule
200	 nop
201	cli
202#ifdef CONFIG_TRACE_IRQFLAGS
203	mov.l	5f, r0
204	jsr	@r0
205	 nop
206#endif
207	!
208	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
209	tst	#_TIF_WORK_MASK, r0
210	bt	__restore_all
211	bra	work_pending
212	 tst	#_TIF_NEED_RESCHED, r0
213
214	.align	2
2151:	.long	schedule
2162:	.long	do_notify_resume
2173:	.long	restore_all
218#ifdef CONFIG_TRACE_IRQFLAGS
2194:	.long	trace_hardirqs_on
2205:	.long	trace_hardirqs_off
221#endif
222
223	.align	2
224syscall_exit_work:
225	! r0: current_thread_info->flags
226	! r8: current_thread_info
227	tst	#_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP, r0
228	bt/s	work_pending
229	 tst	#_TIF_NEED_RESCHED, r0
230#ifdef CONFIG_TRACE_IRQFLAGS
231	mov.l	5f, r0
232	jsr	@r0
233	 nop
234#endif
235	sti
236	! XXX setup arguments...
237	mov.l	4f, r0			! do_syscall_trace
238	jsr	@r0
239	 nop
240	bra	resume_userspace
241	 nop
242
243	.align	2
244syscall_trace_entry:
245	!                     	Yes it is traced.
246	! XXX setup arguments...
247	mov.l	4f, r11		! Call do_syscall_trace which notifies
248	jsr	@r11	    	! superior (will chomp R[0-7])
249	 nop
250	!			Reload R0-R4 from kernel stack, where the
251	!   	    	    	parent may have modified them using
252	!   	    	    	ptrace(POKEUSR).  (Note that R0-R2 are
253	!   	    	    	used by the system call handler directly
254	!   	    	    	from the kernel stack anyway, so don't need
255	!   	    	    	to be reloaded here.)  This allows the parent
256	!   	    	    	to rewrite system calls and args on the fly.
257	mov.l	@(OFF_R4,r15), r4   ! arg0
258	mov.l	@(OFF_R5,r15), r5
259	mov.l	@(OFF_R6,r15), r6
260	mov.l	@(OFF_R7,r15), r7   ! arg3
261	mov.l	@(OFF_R3,r15), r3   ! syscall_nr
262	!
263	mov.l	2f, r10			! Number of syscalls
264	cmp/hs	r10, r3
265	bf	syscall_call
266	mov	#-ENOSYS, r0
267	bra	syscall_exit
268	 mov.l	r0, @(OFF_R0,r15)	! Return value
269
270__restore_all:
271	mov.l	1f, r0
272	jmp	@r0
273	 nop
274
275	.align	2
2761:	.long	restore_all
277
278	.align	2
279syscall_badsys:			! Bad syscall number
280	mov	#-ENOSYS, r0
281	bra	resume_userspace
282	 mov.l	r0, @(OFF_R0,r15)	! Return value
283
284/*
285 * The main debug trap handler.
286 *
287 * r8=TRA (not the trap number!)
288 *
289 * Note: This assumes that the trapa value is left in its original
290 * form (without the shlr2 shift) so the calculation for the jump
291 * call table offset remains a simple in place mask.
292 */
293debug_trap:
294	mov	r8, r0
295	and	#(0xf << 2), r0
296	mov.l	1f, r8
297	add	r0, r8
298	mov.l	@r8, r8
299	jmp	@r8
300	 nop
301
302	.align	2
3031:	.long	debug_trap_table
304
305/*
306 * Syscall interface:
307 *
308 *	Syscall #: R3
309 *	Arguments #0 to #3: R4--R7
310 *	Arguments #4 to #6: R0, R1, R2
311 *	TRA: (number of arguments + ABI revision) x 4
312 *
313 * This code also handles delegating other traps to the BIOS/gdb stub
314 * according to:
315 *
316 * Trap number
317 * (TRA>>2)	Purpose
318 * --------	-------
319 * 0x00-0x0f	original SH-3/4 syscall ABI (not in general use).
320 * 0x10-0x1f	general SH-3/4 syscall ABI.
321 * 0x20-0x2f	syscall ABI for SH-2 parts.
322 * 0x30-0x3f	debug traps used by the kernel.
323 * 0x40-0xff	Not supported by all parts, so left unhandled.
324 *
325 * Note: When we're first called, the TRA value must be shifted
326 * right 2 bits in order to get the value that was used as the "trapa"
327 * argument.
328 */
329
330	.align	2
331	.globl	ret_from_fork
332ret_from_fork:
333	mov.l	1f, r8
334	jsr	@r8
335	 mov	r0, r4
336	bra	syscall_exit
337	 nop
338	.align	2
3391:	.long	schedule_tail
340
341/*
342 * The poorly named main trapa decode and dispatch routine, for
343 * system calls and debug traps through their respective jump tables.
344 */
345ENTRY(system_call)
346#if !defined(CONFIG_CPU_SH2)
347	mov.l	1f, r9
348	mov.l	@r9, r8		! Read from TRA (Trap Address) Register
349#endif
350	/*
351	 * Check the trap type
352	 */
353	mov	#((0x20 << 2) - 1), r9
354	cmp/hi	r9, r8
355	bt/s	debug_trap		! it's a debug trap..
356	 mov	#OFF_TRA, r9
357	add	r15, r9
358	mov.l	r8, @r9			! set TRA value to tra
359#ifdef CONFIG_TRACE_IRQFLAGS
360	mov.l	5f, r10
361	jsr	@r10
362	 nop
363#endif
364	sti
365
366	!
367	get_current_thread_info r8, r10
368	mov.l	@(TI_FLAGS,r8), r8
369	mov	#_TIF_SYSCALL_TRACE, r10
370	tst	r10, r8
371	bf	syscall_trace_entry
372	!
373	mov.l	2f, r8			! Number of syscalls
374	cmp/hs	r8, r3
375	bt	syscall_badsys
376	!
377syscall_call:
378	shll2	r3		! x4
379	mov.l	3f, r8		! Load the address of sys_call_table
380	add	r8, r3
381	mov.l	@r3, r8
382	jsr	@r8	    	! jump to specific syscall handler
383	 nop
384	mov.l	@(OFF_R0,r15), r12		! save r0
385	mov.l	r0, @(OFF_R0,r15)		! save the return value
386	!
387syscall_exit:
388	cli
389#ifdef CONFIG_TRACE_IRQFLAGS
390	mov.l	6f, r0
391	jsr	@r0
392	 nop
393#endif
394	!
395	get_current_thread_info r8, r0
396	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
397	tst	#_TIF_ALLWORK_MASK, r0
398	bf	syscall_exit_work
399	bra	__restore_all
400	 nop
401	.align	2
402#if !defined(CONFIG_CPU_SH2)
4031:	.long	TRA
404#endif
4052:	.long	NR_syscalls
4063:	.long	sys_call_table
4074:	.long	do_syscall_trace
408#ifdef CONFIG_TRACE_IRQFLAGS
4095:	.long	trace_hardirqs_on
4106:	.long	trace_hardirqs_off
411#endif
412