xref: /openbmc/linux/arch/sh/kernel/entry-common.S (revision 48cc39c3) 
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_PREEMPTION)
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_PREEMPTION
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__restore_all:
182	mov	#OFF_SR, r0
183	mov.l	@(r0,r15), r0	! get status register
184
185	shlr2	r0
186	and	#0x3c, r0
187	cmp/eq	#0x3c, r0
188	bt	1f
189	TRACE_IRQS_ON
190	bra	2f
191	 nop
1921:
193	TRACE_IRQS_OFF
1942:
195	mov.l	3f, r0
196	jmp	@r0
197	 nop
198
199	.align	2
2003:	.long	restore_all
201
202	.align	2
203syscall_badsys:			! Bad syscall number
204	get_current_thread_info r8, r0
205	mov	#-ENOSYS, r0
206	bra	resume_userspace
207	 mov.l	r0, @(OFF_R0,r15)	! Return value
208
209/*
210 * The main debug trap handler.
211 *
212 * r8=TRA (not the trap number!)
213 *
214 * Note: This assumes that the trapa value is left in its original
215 * form (without the shlr2 shift) so the calculation for the jump
216 * call table offset remains a simple in place mask.
217 */
218debug_trap:
219	mov	r8, r0
220	and	#(0xf << 2), r0
221	mov.l	1f, r8
222	add	r0, r8
223	mov.l	@r8, r8
224	jsr	@r8
225	 nop
226	bra	ret_from_exception
227	 nop
228	CFI_ENDPROC
229
230	.align	2
2311:	.long	debug_trap_table
232
233/*
234 * Syscall interface:
235 *
236 *	Syscall #: R3
237 *	Arguments #0 to #3: R4--R7
238 *	Arguments #4 to #6: R0, R1, R2
239 *	TRA: See following table.
240 *
241 * (TRA>>2)	Purpose
242 * --------	-------
243 * 0x00-0x0f	original SH-3/4 syscall ABI (not in general use).
244 * 0x10-0x1f	general SH-3/4 syscall ABI.
245 *      0x1f	unified SH-2/3/4 syscall ABI (preferred).
246 * 0x20-0x2f	original SH-2 syscall ABI.
247 * 0x30-0x3f	debug traps used by the kernel.
248 * 0x40-0xff	Not supported by all parts, so left unhandled.
249 *
250 * For making system calls, any trap number in the range for the
251 * given cpu model may be used, but the unified trap number 0x1f is
252 * preferred for compatibility with all models.
253 *
254 * The low bits of the trap number were once documented as matching
255 * the number of arguments, but they were never actually used as such
256 * by the kernel. SH-2 originally used its own separate trap range
257 * because several hardware exceptions fell in the range used for the
258 * SH-3/4 syscall ABI.
259 *
260 * This code also handles delegating other traps to the BIOS/gdb stub.
261 *
262 * Note: When we're first called, the TRA value must be shifted
263 * right 2 bits in order to get the value that was used as the "trapa"
264 * argument.
265 */
266
267	.align	2
268	.globl	ret_from_fork
269ret_from_fork:
270	mov.l	1f, r8
271	jsr	@r8
272	 mov	r0, r4
273	bra	syscall_exit
274	 nop
275
276	.align	2
277	.globl	ret_from_kernel_thread
278ret_from_kernel_thread:
279	mov.l	1f, r8
280	jsr	@r8
281	 mov	r0, r4
282	mov.l	@(OFF_R5,r15), r5   ! fn
283	jsr	@r5
284	 mov.l	@(OFF_R4,r15), r4   ! arg
285	bra	syscall_exit
286	 nop
287
288	.align	2
2891:	.long	schedule_tail
290
291/*
292 * The poorly named main trapa decode and dispatch routine, for
293 * system calls and debug traps through their respective jump tables.
294 */
295ENTRY(system_call)
296	setup_frame_reg
297#if !defined(CONFIG_CPU_SH2)
298	mov.l	1f, r9
299	mov.l	@r9, r8		! Read from TRA (Trap Address) Register
300#endif
301
302	mov	#OFF_TRA, r10
303	add	r15, r10
304	mov.l	r8, @r10		! set TRA value to tra
305
306	/*
307	 * Check the trap type
308	 */
309	mov	#((0x20 << 2) - 1), r9
310	cmp/hi	r9, r8
311	bt/s	debug_trap		! it's a debug trap..
312	 nop
313
314	TRACE_IRQS_ON
315	sti
316
317	!
318	get_current_thread_info r8, r10
319	mov.l	@(TI_FLAGS,r8), r8
320	mov	#(_TIF_WORK_SYSCALL_MASK & 0xff), r10
321	mov	#(_TIF_WORK_SYSCALL_MASK >> 8), r9
322	tst	r10, r8
323	shll8	r9
324	bf	syscall_trace_entry
325	tst	r9, r8
326	bf	syscall_trace_entry
327	!
328	mov.l	6f, r8			! Number of syscalls
329	cmp/hs	r8, r3
330	bt	syscall_badsys
331	!
332syscall_call:
333	shll2	r3		! x4
334	mov.l	3f, r8		! Load the address of sys_call_table
335	add	r8, r3
336	mov.l	@r3, r8
337	mov.l	@(OFF_R2,r15), r2
338	mov.l	@(OFF_R1,r15), r1
339	mov.l	@(OFF_R0,r15), r0
340	mov.l	r2, @-r15
341	mov.l	r1, @-r15
342	mov.l	r0, @-r15
343	jsr	@r8	    	! jump to specific syscall handler
344	 nop
345	add	#12, r15
346	mov.l	@(OFF_R0,r15), r12		! save r0
347	mov.l	r0, @(OFF_R0,r15)		! save the return value
348	!
349syscall_exit:
350	cli
351	TRACE_IRQS_OFF
352	!
353	get_current_thread_info r8, r0
354	mov.l	@(TI_FLAGS,r8), r0		! current_thread_info->flags
355	tst	#(_TIF_ALLWORK_MASK & 0xff), r0
356	mov	#(_TIF_ALLWORK_MASK >> 8), r1
357	bf	syscall_exit_work
358	shlr8	r0
359	tst	r0, r1
360	bf	syscall_exit_work
361	bra	__restore_all
362	 nop
363
364	.align	2
365syscall_trace_entry:
366	!                     	Yes it is traced.
367	mov     r15, r4
368	mov.l	7f, r11		! Call do_syscall_trace_enter which notifies
369	jsr	@r11	    	! superior (will chomp R[0-7])
370	 nop
371	cmp/eq	#-1, r0
372	bt	syscall_exit
373	!			Reload R0-R4 from kernel stack, where the
374	!   	    	    	parent may have modified them using
375	!   	    	    	ptrace(POKEUSR).  (Note that R0-R2 are
376	!   	    	    	reloaded from the kernel stack by syscall_call
377	!   	    	    	below, so don't need to be reloaded here.)
378	!   	    	    	This allows the parent to rewrite system calls
379	!   	    	    	and args on the fly.
380	mov.l	@(OFF_R4,r15), r4   ! arg0
381	mov.l	@(OFF_R5,r15), r5
382	mov.l	@(OFF_R6,r15), r6
383	mov.l	@(OFF_R7,r15), r7   ! arg3
384	mov.l	@(OFF_R3,r15), r3   ! syscall_nr
385	!
386	mov.l	6f, r10			! Number of syscalls
387	cmp/hs	r10, r3
388	bf	syscall_call
389	mov	#-ENOSYS, r0
390	bra	syscall_exit
391	 mov.l	r0, @(OFF_R0,r15)	! Return value
392
393	.align	2
394#if !defined(CONFIG_CPU_SH2)
3951:	.long	TRA
396#endif
3976:	.long	NR_syscalls
3983:	.long	sys_call_table
3997:	.long	do_syscall_trace_enter
4008:	.long	do_syscall_trace_leave
401