xref: /openbmc/linux/arch/sh/kernel/entry-common.S (revision 20e2fc42) 
1/* SPDX-License-Identifier: GPL-2.0
2 *
3 *  Copyright (C) 1999, 2000, 2002  Niibe Yutaka
4 *  Copyright (C) 2003 - 2008  Paul Mundt
5 */
6
7! NOTE:
8! GNU as (as of 2.9.1) changes bf/s into bt/s and bra, when the address
9! to be jumped is too far, but it causes illegal slot exception.
10
11/*
12 * entry.S contains the system-call and fault low-level handling routines.
13 * This also contains the timer-interrupt handler, as well as all interrupts
14 * and faults that can result in a task-switch.
15 *
16 * NOTE: This code handles signal-recognition, which happens every time
17 * after a timer-interrupt and after each system call.
18 *
19 * NOTE: This code uses a convention that instructions in the delay slot
20 * of a transfer-control instruction are indented by an extra space, thus:
21 *
22 *    jmp	@k0	    ! control-transfer instruction
23 *     ldc	k1, ssr     ! delay slot
24 *
25 * Stack layout in 'ret_from_syscall':
26 * 	ptrace needs to have all regs on the stack.
27 *	if the order here is changed, it needs to be
28 *	updated in ptrace.c and ptrace.h
29 *
30 *	r0
31 *      ...
32 *	r15 = stack pointer
33 *	spc
34 *	pr
35 *	ssr
36 *	gbr
37 *	mach
38 *	macl
39 *	syscall #
40 *
41 */
42#include <asm/dwarf.h>
43
44#if defined(CONFIG_PREEMPT)
45#  define preempt_stop()	cli ; TRACE_IRQS_OFF
46#else
47#  define preempt_stop()
48#  define resume_kernel		__restore_all
49#endif
50
51
52	.align	2
53ENTRY(exception_error)
54	!
55	TRACE_IRQS_ON
56	sti
57	mov.l	1f, r0
58	jmp	@r0
59	 nop
60
61	.align	2
621:	.long	do_exception_error
63
64	.align	2
65ret_from_exception:
66	CFI_STARTPROC simple
67	CFI_DEF_CFA r14, 0
68	CFI_REL_OFFSET 17, 64
69	CFI_REL_OFFSET 15, 60
70	CFI_REL_OFFSET 14, 56
71	CFI_REL_OFFSET 13, 52
72	CFI_REL_OFFSET 12, 48
73	CFI_REL_OFFSET 11, 44
74	CFI_REL_OFFSET 10, 40
75	CFI_REL_OFFSET 9, 36
76	CFI_REL_OFFSET 8, 32
77	preempt_stop()
78ENTRY(ret_from_irq)
79	!
80	mov	#OFF_SR, r0
81	mov.l	@(r0,r15), r0	! get status register
82	shll	r0
83	shll	r0		! kernel space?
84	get_current_thread_info r8, r0
85	bt	resume_kernel	! Yes, it's from kernel, go back soon
86
87#ifdef CONFIG_PREEMPT
88	bra	resume_userspace
89	 nop
90ENTRY(resume_kernel)
91	cli
92	TRACE_IRQS_OFF
93	mov.l	@(TI_PRE_COUNT,r8), r0	! current_thread_info->preempt_count
94	tst	r0, r0
95	bf	noresched
96need_resched:
97	mov.l	@(TI_FLAGS,r8), r0	! current_thread_info->flags
98	tst	#_TIF_NEED_RESCHED, r0	! need_resched set?
99	bt	noresched
100
101	mov	#OFF_SR, r0
102	mov.l	@(r0,r15), r0		! get status register
103	shlr	r0
104	and	#(0xf0>>1), r0		! interrupts off (exception path)?
105	cmp/eq	#(0xf0>>1), r0
106	bt	noresched
107	mov.l	1f, r0
108	jsr	@r0			! call preempt_schedule_irq
109	 nop
110	bra	need_resched
111	 nop
112
113noresched:
114	bra	__restore_all
115	 nop
116
117	.align 2
1181:	.long	preempt_schedule_irq
119#endif
120
121ENTRY(resume_userspace)
122	! r8: current_thread_info
123	cli
124	TRACE_IRQS_OFF
125	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
126	tst	#(_TIF_WORK_MASK & 0xff), r0
127	bt/s	__restore_all
128	 tst	#_TIF_NEED_RESCHED, r0
129
130	.align	2
131work_pending:
132	! r0: current_thread_info->flags
133	! r8: current_thread_info
134	! t:  result of "tst	#_TIF_NEED_RESCHED, r0"
135	bf/s	work_resched
136	 tst	#(_TIF_SIGPENDING | _TIF_NOTIFY_RESUME), r0
137work_notifysig:
138	bt/s	__restore_all
139	 mov	r15, r4
140	mov	r12, r5		! set arg1(save_r0)
141	mov	r0, r6
142	sti
143	mov.l	2f, r1
144	mov.l	3f, r0
145	jmp	@r1
146	 lds	r0, pr
147work_resched:
148	mov.l	1f, r1
149	jsr	@r1				! schedule
150	 nop
151	cli
152	TRACE_IRQS_OFF
153	!
154	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
155	tst	#(_TIF_WORK_MASK & 0xff), r0
156	bt	__restore_all
157	bra	work_pending
158	 tst	#_TIF_NEED_RESCHED, r0
159
160	.align	2
1611:	.long	schedule
1622:	.long	do_notify_resume
1633:	.long	resume_userspace
164
165	.align	2
166syscall_exit_work:
167	! r0: current_thread_info->flags
168	! r8: current_thread_info
169	tst	#(_TIF_WORK_SYSCALL_MASK & 0xff), r0
170	bt/s	work_pending
171	 tst	#_TIF_NEED_RESCHED, r0
172	TRACE_IRQS_ON
173	sti
174	mov	r15, r4
175	mov.l	8f, r0			! do_syscall_trace_leave
176	jsr	@r0
177	 nop
178	bra	resume_userspace
179	 nop
180
181	.align	2
182syscall_trace_entry:
183	!                     	Yes it is traced.
184	mov     r15, r4
185	mov.l	7f, r11		! Call do_syscall_trace_enter which notifies
186	jsr	@r11	    	! superior (will chomp R[0-7])
187	 nop
188	mov.l	r0, @(OFF_R0,r15)	! Save return value
189	!			Reload R0-R4 from kernel stack, where the
190	!   	    	    	parent may have modified them using
191	!   	    	    	ptrace(POKEUSR).  (Note that R0-R2 are
192	!   	    	    	reloaded from the kernel stack by syscall_call
193	!   	    	    	below, so don't need to be reloaded here.)
194	!   	    	    	This allows the parent to rewrite system calls
195	!   	    	    	and args on the fly.
196	mov.l	@(OFF_R4,r15), r4   ! arg0
197	mov.l	@(OFF_R5,r15), r5
198	mov.l	@(OFF_R6,r15), r6
199	mov.l	@(OFF_R7,r15), r7   ! arg3
200	mov.l	@(OFF_R3,r15), r3   ! syscall_nr
201	!
202	mov.l	2f, r10			! Number of syscalls
203	cmp/hs	r10, r3
204	bf	syscall_call
205	mov	#-ENOSYS, r0
206	bra	syscall_exit
207	 mov.l	r0, @(OFF_R0,r15)	! Return value
208
209__restore_all:
210	mov	#OFF_SR, r0
211	mov.l	@(r0,r15), r0	! get status register
212
213	shlr2	r0
214	and	#0x3c, r0
215	cmp/eq	#0x3c, r0
216	bt	1f
217	TRACE_IRQS_ON
218	bra	2f
219	 nop
2201:
221	TRACE_IRQS_OFF
2222:
223	mov.l	3f, r0
224	jmp	@r0
225	 nop
226
227	.align	2
2283:	.long	restore_all
229
230	.align	2
231syscall_badsys:			! Bad syscall number
232	get_current_thread_info r8, r0
233	mov	#-ENOSYS, r0
234	bra	resume_userspace
235	 mov.l	r0, @(OFF_R0,r15)	! Return value
236
237/*
238 * The main debug trap handler.
239 *
240 * r8=TRA (not the trap number!)
241 *
242 * Note: This assumes that the trapa value is left in its original
243 * form (without the shlr2 shift) so the calculation for the jump
244 * call table offset remains a simple in place mask.
245 */
246debug_trap:
247	mov	r8, r0
248	and	#(0xf << 2), r0
249	mov.l	1f, r8
250	add	r0, r8
251	mov.l	@r8, r8
252	jsr	@r8
253	 nop
254	bra	ret_from_exception
255	 nop
256	CFI_ENDPROC
257
258	.align	2
2591:	.long	debug_trap_table
260
261/*
262 * Syscall interface:
263 *
264 *	Syscall #: R3
265 *	Arguments #0 to #3: R4--R7
266 *	Arguments #4 to #6: R0, R1, R2
267 *	TRA: See following table.
268 *
269 * (TRA>>2)	Purpose
270 * --------	-------
271 * 0x00-0x0f	original SH-3/4 syscall ABI (not in general use).
272 * 0x10-0x1f	general SH-3/4 syscall ABI.
273 *      0x1f	unified SH-2/3/4 syscall ABI (preferred).
274 * 0x20-0x2f	original SH-2 syscall ABI.
275 * 0x30-0x3f	debug traps used by the kernel.
276 * 0x40-0xff	Not supported by all parts, so left unhandled.
277 *
278 * For making system calls, any trap number in the range for the
279 * given cpu model may be used, but the unified trap number 0x1f is
280 * preferred for compatibility with all models.
281 *
282 * The low bits of the trap number were once documented as matching
283 * the number of arguments, but they were never actually used as such
284 * by the kernel. SH-2 originally used its own separate trap range
285 * because several hardware exceptions fell in the range used for the
286 * SH-3/4 syscall ABI.
287 *
288 * This code also handles delegating other traps to the BIOS/gdb stub.
289 *
290 * Note: When we're first called, the TRA value must be shifted
291 * right 2 bits in order to get the value that was used as the "trapa"
292 * argument.
293 */
294
295	.align	2
296	.globl	ret_from_fork
297ret_from_fork:
298	mov.l	1f, r8
299	jsr	@r8
300	 mov	r0, r4
301	bra	syscall_exit
302	 nop
303
304	.align	2
305	.globl	ret_from_kernel_thread
306ret_from_kernel_thread:
307	mov.l	1f, r8
308	jsr	@r8
309	 mov	r0, r4
310	mov.l	@(OFF_R5,r15), r5   ! fn
311	jsr	@r5
312	 mov.l	@(OFF_R4,r15), r4   ! arg
313	bra	syscall_exit
314	 nop
315
316	.align	2
3171:	.long	schedule_tail
318
319/*
320 * The poorly named main trapa decode and dispatch routine, for
321 * system calls and debug traps through their respective jump tables.
322 */
323ENTRY(system_call)
324	setup_frame_reg
325#if !defined(CONFIG_CPU_SH2)
326	mov.l	1f, r9
327	mov.l	@r9, r8		! Read from TRA (Trap Address) Register
328#endif
329
330	mov	#OFF_TRA, r10
331	add	r15, r10
332	mov.l	r8, @r10		! set TRA value to tra
333
334	/*
335	 * Check the trap type
336	 */
337	mov	#((0x20 << 2) - 1), r9
338	cmp/hi	r9, r8
339	bt/s	debug_trap		! it's a debug trap..
340	 nop
341
342	TRACE_IRQS_ON
343	sti
344
345	!
346	get_current_thread_info r8, r10
347	mov.l	@(TI_FLAGS,r8), r8
348	mov	#(_TIF_WORK_SYSCALL_MASK & 0xff), r10
349	mov	#(_TIF_WORK_SYSCALL_MASK >> 8), r9
350	tst	r10, r8
351	shll8	r9
352	bf	syscall_trace_entry
353	tst	r9, r8
354	bf	syscall_trace_entry
355	!
356	mov.l	2f, r8			! Number of syscalls
357	cmp/hs	r8, r3
358	bt	syscall_badsys
359	!
360syscall_call:
361	shll2	r3		! x4
362	mov.l	3f, r8		! Load the address of sys_call_table
363	add	r8, r3
364	mov.l	@r3, r8
365	mov.l	@(OFF_R2,r15), r2
366	mov.l	@(OFF_R1,r15), r1
367	mov.l	@(OFF_R0,r15), r0
368	mov.l	r2, @-r15
369	mov.l	r1, @-r15
370	mov.l	r0, @-r15
371	jsr	@r8	    	! jump to specific syscall handler
372	 nop
373	add	#12, r15
374	mov.l	@(OFF_R0,r15), r12		! save r0
375	mov.l	r0, @(OFF_R0,r15)		! save the return value
376	!
377syscall_exit:
378	cli
379	TRACE_IRQS_OFF
380	!
381	get_current_thread_info r8, r0
382	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
383	tst	#(_TIF_ALLWORK_MASK & 0xff), r0
384	mov	#(_TIF_ALLWORK_MASK >> 8), r1
385	bf	syscall_exit_work
386	shlr8	r0
387	tst	r0, r1
388	bf	syscall_exit_work
389	bra	__restore_all
390	 nop
391	.align	2
392#if !defined(CONFIG_CPU_SH2)
3931:	.long	TRA
394#endif
3952:	.long	NR_syscalls
3963:	.long	sys_call_table
3977:	.long	do_syscall_trace_enter
3988:	.long	do_syscall_trace_leave
399