xref: /openbmc/linux/arch/sh/kernel/entry-common.S (revision 732a675a)
1/*
2 *  Copyright (C) 1999, 2000, 2002  Niibe Yutaka
3 *  Copyright (C) 2003 - 2008  Paul Mundt
4 *
5 * This file is subject to the terms and conditions of the GNU General Public
6 * License.  See the file "COPYING" in the main directory of this archive
7 * for more details.
8 *
9 */
10
11! NOTE:
12! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
13! to be jumped is too far, but it causes illegal slot exception.
14
15/*
16 * entry.S contains the system-call and fault low-level handling routines.
17 * This also contains the timer-interrupt handler, as well as all interrupts
18 * and faults that can result in a task-switch.
19 *
20 * NOTE: This code handles signal-recognition, which happens every time
21 * after a timer-interrupt and after each system call.
22 *
23 * NOTE: This code uses a convention that instructions in the delay slot
24 * of a transfer-control instruction are indented by an extra space, thus:
25 *
26 *    jmp	@k0	    ! control-transfer instruction
27 *     ldc	k1, ssr     ! delay slot
28 *
29 * Stack layout in 'ret_from_syscall':
30 * 	ptrace needs to have all regs on the stack.
31 *	if the order here is changed, it needs to be
32 *	updated in ptrace.c and ptrace.h
33 *
34 *	r0
35 *      ...
36 *	r15 = stack pointer
37 *	spc
38 *	pr
39 *	ssr
40 *	gbr
41 *	mach
42 *	macl
43 *	syscall #
44 *
45 */
46
47#if defined(CONFIG_PREEMPT)
48#  define preempt_stop()	cli
49#else
50#  define preempt_stop()
51#  define resume_kernel		__restore_all
52#endif
53
54
55	.align	2
56ENTRY(exception_error)
57	!
58#ifdef CONFIG_TRACE_IRQFLAGS
59	mov.l	2f, r0
60	jsr	@r0
61	 nop
62#endif
63	sti
64	mov.l	1f, r0
65	jmp	@r0
66	 nop
67
68	.align	2
691:	.long	do_exception_error
70#ifdef CONFIG_TRACE_IRQFLAGS
712:	.long	trace_hardirqs_on
72#endif
73
74	.align	2
75ret_from_exception:
76	preempt_stop()
77#ifdef CONFIG_TRACE_IRQFLAGS
78	mov.l	4f, r0
79	jsr	@r0
80	 nop
81#endif
82ENTRY(ret_from_irq)
83	!
84	mov	#OFF_SR, r0
85	mov.l	@(r0,r15), r0	! get status register
86	shll	r0
87	shll	r0		! kernel space?
88	get_current_thread_info r8, r0
89	bt	resume_kernel	! Yes, it's from kernel, go back soon
90
91#ifdef CONFIG_PREEMPT
92	bra	resume_userspace
93	 nop
94ENTRY(resume_kernel)
95	mov.l	@(TI_PRE_COUNT,r8), r0	! current_thread_info->preempt_count
96	tst	r0, r0
97	bf	noresched
98need_resched:
99	mov.l	@(TI_FLAGS,r8), r0	! current_thread_info->flags
100	tst	#_TIF_NEED_RESCHED, r0	! need_resched set?
101	bt	noresched
102
103	mov	#OFF_SR, r0
104	mov.l	@(r0,r15), r0		! get status register
105	and	#0xf0, r0		! interrupts off (exception path)?
106	cmp/eq	#0xf0, r0
107	bt	noresched
108
109	mov.l	1f, r0
110	mov.l	r0, @(TI_PRE_COUNT,r8)
111
112#ifdef CONFIG_TRACE_IRQFLAGS
113	mov.l	3f, r0
114	jsr	@r0
115	 nop
116#endif
117	sti
118	mov.l	2f, r0
119	jsr	@r0
120	 nop
121	mov	#0, r0
122	mov.l	r0, @(TI_PRE_COUNT,r8)
123	cli
124#ifdef CONFIG_TRACE_IRQFLAGS
125	mov.l	4f, r0
126	jsr	@r0
127	 nop
128#endif
129
130	bra	need_resched
131	 nop
132
133noresched:
134	bra	__restore_all
135	 nop
136
137	.align 2
1381:	.long	PREEMPT_ACTIVE
1392:	.long	schedule
140#ifdef CONFIG_TRACE_IRQFLAGS
1413:	.long	trace_hardirqs_on
1424:	.long	trace_hardirqs_off
143#endif
144#endif
145
146ENTRY(resume_userspace)
147	! r8: current_thread_info
148	cli
149#ifdef CONFIG_TRACE_IRQFLAGS
150	mov.l	5f, r0
151	jsr	@r0
152	 nop
153#endif
154	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
155	tst	#_TIF_WORK_MASK, r0
156	bt/s	__restore_all
157	 tst	#_TIF_NEED_RESCHED, r0
158
159	.align	2
160work_pending:
161	! r0: current_thread_info->flags
162	! r8: current_thread_info
163	! t:  result of "tst	#_TIF_NEED_RESCHED, r0"
164	bf/s	work_resched
165	 tst	#(_TIF_SIGPENDING | _TIF_RESTORE_SIGMASK), r0
166work_notifysig:
167	bt/s	__restore_all
168	 mov	r15, r4
169	mov	r12, r5		! set arg1(save_r0)
170	mov	r0, r6
171	mov.l	2f, r1
172	mov.l	3f, r0
173	jmp	@r1
174	 lds	r0, pr
175work_resched:
176	mov.l	1f, r1
177	jsr	@r1				! schedule
178	 nop
179	cli
180#ifdef CONFIG_TRACE_IRQFLAGS
181	mov.l	5f, r0
182	jsr	@r0
183	 nop
184#endif
185	!
186	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
187	tst	#_TIF_WORK_MASK, r0
188	bt	__restore_all
189	bra	work_pending
190	 tst	#_TIF_NEED_RESCHED, r0
191
192	.align	2
1931:	.long	schedule
1942:	.long	do_notify_resume
1953:	.long	restore_all
196#ifdef CONFIG_TRACE_IRQFLAGS
1974:	.long	trace_hardirqs_on
1985:	.long	trace_hardirqs_off
199#endif
200
201	.align	2
202syscall_exit_work:
203	! r0: current_thread_info->flags
204	! r8: current_thread_info
205	tst	#_TIF_SYSCALL_TRACE | _TIF_SINGLESTEP | _TIF_SYSCALL_AUDIT, r0
206	bt/s	work_pending
207	 tst	#_TIF_NEED_RESCHED, r0
208#ifdef CONFIG_TRACE_IRQFLAGS
209	mov.l	5f, r0
210	jsr	@r0
211	 nop
212#endif
213	sti
214	! XXX setup arguments...
215	mov	r15, r4
216	mov	#1, r5
217	mov.l	4f, r0			! do_syscall_trace
218	jsr	@r0
219	 nop
220	bra	resume_userspace
221	 nop
222
223	.align	2
224syscall_trace_entry:
225	!                     	Yes it is traced.
226	! XXX setup arguments...
227	mov     r15, r4
228	mov     #0, r5
229	mov.l	4f, r11		! Call do_syscall_trace which notifies
230	jsr	@r11	    	! superior (will chomp R[0-7])
231	 nop
232	!			Reload R0-R4 from kernel stack, where the
233	!   	    	    	parent may have modified them using
234	!   	    	    	ptrace(POKEUSR).  (Note that R0-R2 are
235	!   	    	    	used by the system call handler directly
236	!   	    	    	from the kernel stack anyway, so don't need
237	!   	    	    	to be reloaded here.)  This allows the parent
238	!   	    	    	to rewrite system calls and args on the fly.
239	mov.l	@(OFF_R4,r15), r4   ! arg0
240	mov.l	@(OFF_R5,r15), r5
241	mov.l	@(OFF_R6,r15), r6
242	mov.l	@(OFF_R7,r15), r7   ! arg3
243	mov.l	@(OFF_R3,r15), r3   ! syscall_nr
244	!
245	mov.l	2f, r10			! Number of syscalls
246	cmp/hs	r10, r3
247	bf	syscall_call
248	mov	#-ENOSYS, r0
249	bra	syscall_exit
250	 mov.l	r0, @(OFF_R0,r15)	! Return value
251
252__restore_all:
253	mov.l	1f, r0
254	jmp	@r0
255	 nop
256
257	.align	2
2581:	.long	restore_all
259
260	.align	2
261syscall_badsys:			! Bad syscall number
262	get_current_thread_info r8, r0
263	mov	#-ENOSYS, r0
264	bra	resume_userspace
265	 mov.l	r0, @(OFF_R0,r15)	! Return value
266
267/*
268 * The main debug trap handler.
269 *
270 * r8=TRA (not the trap number!)
271 *
272 * Note: This assumes that the trapa value is left in its original
273 * form (without the shlr2 shift) so the calculation for the jump
274 * call table offset remains a simple in place mask.
275 */
276debug_trap:
277	mov	r8, r0
278	and	#(0xf << 2), r0
279	mov.l	1f, r8
280	add	r0, r8
281	mov.l	@r8, r8
282	jsr	@r8
283	 nop
284	bra	__restore_all
285	 nop
286
287	.align	2
2881:	.long	debug_trap_table
289
290/*
291 * Syscall interface:
292 *
293 *	Syscall #: R3
294 *	Arguments #0 to #3: R4--R7
295 *	Arguments #4 to #6: R0, R1, R2
296 *	TRA: (number of arguments + ABI revision) x 4
297 *
298 * This code also handles delegating other traps to the BIOS/gdb stub
299 * according to:
300 *
301 * Trap number
302 * (TRA>>2)	Purpose
303 * --------	-------
304 * 0x00-0x0f	original SH-3/4 syscall ABI (not in general use).
305 * 0x10-0x1f	general SH-3/4 syscall ABI.
306 * 0x20-0x2f	syscall ABI for SH-2 parts.
307 * 0x30-0x3f	debug traps used by the kernel.
308 * 0x40-0xff	Not supported by all parts, so left unhandled.
309 *
310 * Note: When we're first called, the TRA value must be shifted
311 * right 2 bits in order to get the value that was used as the "trapa"
312 * argument.
313 */
314
315	.align	2
316	.globl	ret_from_fork
317ret_from_fork:
318	mov.l	1f, r8
319	jsr	@r8
320	 mov	r0, r4
321	bra	syscall_exit
322	 nop
323	.align	2
3241:	.long	schedule_tail
325
326/*
327 * The poorly named main trapa decode and dispatch routine, for
328 * system calls and debug traps through their respective jump tables.
329 */
330ENTRY(system_call)
331#if !defined(CONFIG_CPU_SH2)
332	mov.l	1f, r9
333	mov.l	@r9, r8		! Read from TRA (Trap Address) Register
334#endif
335	/*
336	 * Check the trap type
337	 */
338	mov	#((0x20 << 2) - 1), r9
339	cmp/hi	r9, r8
340	bt/s	debug_trap		! it's a debug trap..
341	 mov	#OFF_TRA, r9
342	add	r15, r9
343	mov.l	r8, @r9			! set TRA value to tra
344#ifdef CONFIG_TRACE_IRQFLAGS
345	mov.l	5f, r10
346	jsr	@r10
347	 nop
348#endif
349	sti
350
351	!
352	get_current_thread_info r8, r10
353	mov.l	@(TI_FLAGS,r8), r8
354	mov	#(_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT), r10
355	tst	r10, r8
356	bf	syscall_trace_entry
357	!
358	mov.l	2f, r8			! Number of syscalls
359	cmp/hs	r8, r3
360	bt	syscall_badsys
361	!
362syscall_call:
363	shll2	r3		! x4
364	mov.l	3f, r8		! Load the address of sys_call_table
365	add	r8, r3
366	mov.l	@r3, r8
367	jsr	@r8	    	! jump to specific syscall handler
368	 nop
369	mov.l	@(OFF_R0,r15), r12		! save r0
370	mov.l	r0, @(OFF_R0,r15)		! save the return value
371	!
372syscall_exit:
373	cli
374#ifdef CONFIG_TRACE_IRQFLAGS
375	mov.l	6f, r0
376	jsr	@r0
377	 nop
378#endif
379	!
380	get_current_thread_info r8, r0
381	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
382	tst	#_TIF_ALLWORK_MASK, r0
383	bf	syscall_exit_work
384	bra	__restore_all
385	 nop
386	.align	2
387#if !defined(CONFIG_CPU_SH2)
3881:	.long	TRA
389#endif
3902:	.long	NR_syscalls
3913:	.long	sys_call_table
3924:	.long	do_syscall_trace
393#ifdef CONFIG_TRACE_IRQFLAGS
3945:	.long	trace_hardirqs_on
3956:	.long	trace_hardirqs_off
396#endif
397