summaryrefslogtreecommitdiffstats
path: root/arch/nios2/kernel/entry.S
blob: 7729bd3f2e79d48937e7dbead303640610ca24ae (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
/*
 * linux/arch/nios2/kernel/entry.S
 *
 * Copyright (C) 2013-2014  Altera Corporation
 * Copyright (C) 2009, Wind River Systems Inc
 *
 * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
 *
 *  Copyright (C) 1999-2002, Greg Ungerer (gerg@snapgear.com)
 *  Copyright (C) 1998  D. Jeff Dionne <jeff@lineo.ca>,
 *                      Kenneth Albanowski <kjahds@kjahds.com>,
 *  Copyright (C) 2000  Lineo Inc. (www.lineo.com)
 *  Copyright (C) 2004  Microtronix Datacom Ltd.
 *
 * This file is subject to the terms and conditions of the GNU General Public
 * License.  See the file "COPYING" in the main directory of this archive
 * for more details.
 *
 * Linux/m68k support by Hamish Macdonald
 *
 * 68060 fixes by Jesper Skov
 * ColdFire support by Greg Ungerer (gerg@snapgear.com)
 * 5307 fixes by David W. Miller
 * linux 2.4 support David McCullough <davidm@snapgear.com>
 */

#include <linux/sys.h>
#include <linux/linkage.h>
#include <asm/asm-offsets.h>
#include <asm/asm-macros.h>
#include <asm/thread_info.h>
#include <asm/errno.h>
#include <asm/setup.h>
#include <asm/entry.h>
#include <asm/unistd.h>
#include <asm/processor.h>

.macro GET_THREAD_INFO reg
.if THREAD_SIZE & 0xffff0000
	andhi	\reg, sp, %hi(~(THREAD_SIZE-1))
.else
	addi	\reg, r0, %lo(~(THREAD_SIZE-1))
	and	\reg, \reg, sp
.endif
.endm

.macro	kuser_cmpxchg_check
	/*
	 * Make sure our user space atomic helper is restarted if it was
	 * interrupted in a critical region.
	 * ea-4 = address of interrupted insn (ea must be preserved).
	 * sp = saved regs.
	 * cmpxchg_ldw = first critical insn, cmpxchg_stw = last critical insn.
	 * If ea <= cmpxchg_stw and ea > cmpxchg_ldw then saved EA is set to
	 * cmpxchg_ldw + 4.
	*/
	/* et = cmpxchg_stw + 4 */
	movui   et, (KUSER_BASE + 4 + (cmpxchg_stw - __kuser_helper_start))
	bgtu	ea, et, 1f

	subi	et, et, (cmpxchg_stw - cmpxchg_ldw) /* et = cmpxchg_ldw + 4 */
	bltu	ea, et, 1f
	stw	et, PT_EA(sp)	/* fix up EA */
	mov	ea, et
1:
.endm

.section .rodata
.align 4
exception_table:
	.word unhandled_exception	/* 0 - Reset */
	.word unhandled_exception	/* 1 - Processor-only Reset */
	.word external_interrupt	/* 2 - Interrupt */
	.word handle_trap		/* 3 - Trap Instruction */

	.word instruction_trap		/* 4 - Unimplemented instruction */
	.word handle_illegal		/* 5 - Illegal instruction */
	.word handle_unaligned		/* 6 - Misaligned data access */
	.word handle_unaligned		/* 7 - Misaligned destination address */

	.word handle_diverror		/* 8 - Division error */
	.word protection_exception_ba	/* 9 - Supervisor-only instr. address */
	.word protection_exception_instr /* 10 - Supervisor only instruction */
	.word protection_exception_ba	/* 11 - Supervisor only data address */

	.word unhandled_exception	/* 12 - Double TLB miss (data) */
	.word protection_exception_pte	/* 13 - TLB permission violation (x) */
	.word protection_exception_pte	/* 14 - TLB permission violation (r) */
	.word protection_exception_pte	/* 15 - TLB permission violation (w) */

	.word unhandled_exception	/* 16 - MPU region violation */

trap_table:
	.word	handle_system_call	/* 0  */
	.word	instruction_trap	/* 1  */
	.word	instruction_trap	/* 2  */
	.word	instruction_trap	/* 3  */
	.word	instruction_trap	/* 4  */
	.word	instruction_trap	/* 5  */
	.word	instruction_trap	/* 6  */
	.word	instruction_trap	/* 7  */
	.word	instruction_trap	/* 8  */
	.word	instruction_trap	/* 9  */
	.word	instruction_trap	/* 10 */
	.word	instruction_trap	/* 11 */
	.word	instruction_trap	/* 12 */
	.word	instruction_trap	/* 13 */
	.word	instruction_trap	/* 14 */
	.word	instruction_trap	/* 15 */
	.word	instruction_trap	/* 16 */
	.word	instruction_trap	/* 17 */
	.word	instruction_trap	/* 18 */
	.word	instruction_trap	/* 19 */
	.word	instruction_trap	/* 20 */
	.word	instruction_trap	/* 21 */
	.word	instruction_trap	/* 22 */
	.word	instruction_trap	/* 23 */
	.word	instruction_trap	/* 24 */
	.word	instruction_trap	/* 25 */
	.word	instruction_trap	/* 26 */
	.word	instruction_trap	/* 27 */
	.word	instruction_trap	/* 28 */
	.word	instruction_trap	/* 29 */
#ifdef CONFIG_KGDB
	.word	handle_kgdb_breakpoint	/* 30 KGDB breakpoint */
#else
	.word	instruction_trap		/* 30 */
#endif
	.word	handle_breakpoint	/* 31 */

.text
.set noat
.set nobreak

ENTRY(inthandler)
	SAVE_ALL

	kuser_cmpxchg_check

	/* Clear EH bit before we get a new excpetion in the kernel
	 * and after we have saved it to the exception frame. This is done
	 * whether it's trap, tlb-miss or interrupt. If we don't do this
	 * estatus is not updated the next exception.
	 */
	rdctl	r24, status
	movi	r9, %lo(~STATUS_EH)
	and	r24, r24, r9
	wrctl	status, r24

	/* Read cause and vector and branch to the associated handler */
	mov	r4, sp
	rdctl	r5, exception
	movia	r9, exception_table
	add	r24, r9, r5
	ldw	r24, 0(r24)
	jmp	r24


/***********************************************************************
 * Handle traps
 ***********************************************************************
 */
ENTRY(handle_trap)
	ldw	r24, -4(ea)	/* instruction that caused the exception */
	srli	r24, r24, 4
	andi	r24, r24, 0x7c
	movia	r9,trap_table
	add	r24, r24, r9
	ldw	r24, 0(r24)
	jmp	r24


/***********************************************************************
 * Handle system calls
 ***********************************************************************
 */
ENTRY(handle_system_call)
	/* Enable interrupts */
	rdctl	r10, status
	ori	r10, r10, STATUS_PIE
	wrctl	status, r10

	/* Reload registers destroyed by common code. */
	ldw	r4, PT_R4(sp)
	ldw	r5, PT_R5(sp)

local_restart:
	/* Check that the requested system call is within limits */
	movui	r1, __NR_syscalls
	bgeu	r2, r1, ret_invsyscall
	slli	r1, r2, 2
	movhi	r11, %hiadj(sys_call_table)
	add	r1, r1, r11
	ldw	r1, %lo(sys_call_table)(r1)
	beq	r1, r0, ret_invsyscall

	/* Check if we are being traced */
	GET_THREAD_INFO r11
	ldw	r11,TI_FLAGS(r11)
	BTBNZ   r11,r11,TIF_SYSCALL_TRACE,traced_system_call

	/* Execute the system call */
	callr	r1

	/* If the syscall returns a negative result:
	 *   Set r7 to 1 to indicate error,
	 *   Negate r2 to get a positive error code
	 * If the syscall returns zero or a positive value:
	 *   Set r7 to 0.
	 * The sigreturn system calls will skip the code below by
	 * adding to register ra. To avoid destroying registers
	 */
translate_rc_and_ret:
	movi	r1, 0
	bge	r2, zero, 3f
	sub	r2, zero, r2
	movi	r1, 1
3:
	stw	r2, PT_R2(sp)
	stw	r1, PT_R7(sp)
end_translate_rc_and_ret:

ret_from_exception:
	ldw	r1, PT_ESTATUS(sp)
	/* if so, skip resched, signals */
	TSTBNZ	r1, r1, ESTATUS_EU, Luser_return

restore_all:
	rdctl	r10, status			/* disable intrs */
	andi	r10, r10, %lo(~STATUS_PIE)
	wrctl	status, r10
	RESTORE_ALL
	eret

	/* If the syscall number was invalid return ENOSYS */
ret_invsyscall:
	movi	r2, -ENOSYS
	br	translate_rc_and_ret

	/* This implements the same as above, except it calls
	 * do_syscall_trace_enter and do_syscall_trace_exit before and after the
	 * syscall in order for utilities like strace and gdb to work.
	 */
traced_system_call:
	SAVE_SWITCH_STACK
	call	do_syscall_trace_enter
	RESTORE_SWITCH_STACK

	/* Create system call register arguments. The 5th and 6th
	   arguments on stack are already in place at the beginning
	   of pt_regs. */
	ldw	r2, PT_R2(sp)
	ldw	r4, PT_R4(sp)
	ldw	r5, PT_R5(sp)
	ldw	r6, PT_R6(sp)
	ldw	r7, PT_R7(sp)

	/* Fetch the syscall function, we don't need to check the boundaries
	 * since this is already done.
	 */
	slli	r1, r2, 2
	movhi	r11,%hiadj(sys_call_table)
	add	r1, r1, r11
	ldw	r1, %lo(sys_call_table)(r1)

	callr	r1

	/* If the syscall returns a negative result:
	 *   Set r7 to 1 to indicate error,
	 *   Negate r2 to get a positive error code
	 * If the syscall returns zero or a positive value:
	 *   Set r7 to 0.
	 * The sigreturn system calls will skip the code below by
	 * adding to register ra. To avoid destroying registers
	 */
translate_rc_and_ret2:
	movi	r1, 0
	bge	r2, zero, 4f
	sub	r2, zero, r2
	movi	r1, 1
4:
	stw	r2, PT_R2(sp)
	stw	r1, PT_R7(sp)
end_translate_rc_and_ret2:
	SAVE_SWITCH_STACK
	call	do_syscall_trace_exit
	RESTORE_SWITCH_STACK
	br	ret_from_exception

Luser_return:
	GET_THREAD_INFO	r11			/* get thread_info pointer */
	ldw	r10, TI_FLAGS(r11)		/* get thread_info->flags */
	ANDI32	r11, r10, _TIF_WORK_MASK
	beq	r11, r0, restore_all		/* Nothing to do */
	BTBZ	r1, r10, TIF_NEED_RESCHED, Lsignal_return

	/* Reschedule work */
	call	schedule
	br	ret_from_exception

Lsignal_return:
	ANDI32	r1, r10, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME
	beq	r1, r0, restore_all
	mov	r4, sp			/* pt_regs */
	SAVE_SWITCH_STACK
	call	do_notify_resume
	beq	r2, r0, no_work_pending
	RESTORE_SWITCH_STACK
	/* prepare restart syscall here without leaving kernel */
	ldw	r2, PT_R2(sp)	/* reload syscall number in r2 */
	ldw 	r4, PT_R4(sp)	/* reload syscall arguments r4-r9 */
	ldw 	r5, PT_R5(sp)
	ldw 	r6, PT_R6(sp)
	ldw 	r7, PT_R7(sp)
	ldw 	r8, PT_R8(sp)
	ldw 	r9, PT_R9(sp)
	br	local_restart	/* restart syscall */

no_work_pending:
	RESTORE_SWITCH_STACK
	br	ret_from_exception

/***********************************************************************
 * Handle external interrupts.
 ***********************************************************************
 */
/*
 * This is the generic interrupt handler (for all hardware interrupt
 * sources). It figures out the vector number and calls the appropriate
 * interrupt service routine directly.
 */
external_interrupt:
	rdctl	r12, ipending
	rdctl	r9, ienable
	and	r12, r12, r9
	/* skip if no interrupt is pending */
	beq	r12, r0, ret_from_interrupt

	movi	r24, -1
	stw	r24, PT_ORIG_R2(sp)

	/*
	 * Process an external hardware interrupt.
	 */

	addi	ea, ea, -4	/* re-issue the interrupted instruction */
	stw	ea, PT_EA(sp)
2:	movi	r4, %lo(-1)	/* Start from bit position 0,
					highest priority */
				/* This is the IRQ # for handler call */
1:	andi	r10, r12, 1	/* Isolate bit we are interested in */
	srli	r12, r12, 1	/* shift count is costly without hardware
					multiplier */
	addi	r4, r4, 1
	beq	r10, r0, 1b
	mov	r5, sp		/* Setup pt_regs pointer for handler call */
	call	do_IRQ
	rdctl	r12, ipending	/* check again if irq still pending */
	rdctl	r9, ienable	/* Isolate possible interrupts */
	and	r12, r12, r9
	bne	r12, r0, 2b
	/* br	ret_from_interrupt */ /* fall through to ret_from_interrupt */

ENTRY(ret_from_interrupt)
	ldw	r1, PT_ESTATUS(sp)	/* check if returning to kernel */
	TSTBNZ	r1, r1, ESTATUS_EU, Luser_return

#ifdef CONFIG_PREEMPT
	GET_THREAD_INFO	r1
	ldw	r4, TI_PREEMPT_COUNT(r1)
	bne	r4, r0, restore_all
	ldw	r4, TI_FLAGS(r1)		/* ? Need resched set */
	BTBZ	r10, r4, TIF_NEED_RESCHED, restore_all
	ldw	r4, PT_ESTATUS(sp)	/* ? Interrupts off */
	andi	r10, r4, ESTATUS_EPIE
	beq	r10, r0, restore_all
	call	preempt_schedule_irq
#endif
	br	restore_all

/***********************************************************************
 * A few syscall wrappers
 ***********************************************************************
 */
/*
 * int clone(unsigned long clone_flags, unsigned long newsp,
 *		int __user * parent_tidptr, int __user * child_tidptr,
 *		int tls_val)
 */
ENTRY(sys_clone)
	SAVE_SWITCH_STACK
	addi	sp, sp, -4
	stw	r7, 0(sp)	/* Pass 5th arg thru stack */
	mov	r7, r6		/* 4th arg is 3rd of clone() */
	mov	r6, zero	/* 3rd arg always 0 */
	call	do_fork
	addi	sp, sp, 4
	RESTORE_SWITCH_STACK
	ret

ENTRY(sys_rt_sigreturn)
	SAVE_SWITCH_STACK
	mov	r4, sp
	call	do_rt_sigreturn
	RESTORE_SWITCH_STACK
	addi	ra, ra, (end_translate_rc_and_ret - translate_rc_and_ret)
	ret

/***********************************************************************
 * A few other wrappers and stubs
 ***********************************************************************
 */
protection_exception_pte:
	rdctl	r6, pteaddr
	slli	r6, r6, 10
	call	do_page_fault
	br	ret_from_exception

protection_exception_ba:
	rdctl	r6, badaddr
	call	do_page_fault
	br	ret_from_exception

protection_exception_instr:
	call	handle_supervisor_instr
	br	ret_from_exception

handle_breakpoint:
	call	breakpoint_c
	br	ret_from_exception

#ifdef CONFIG_NIOS2_ALIGNMENT_TRAP
handle_unaligned:
	SAVE_SWITCH_STACK
	call	handle_unaligned_c
	RESTORE_SWITCH_STACK
	br	ret_from_exception
#else
handle_unaligned:
	call	handle_unaligned_c
	br	ret_from_exception
#endif

handle_illegal:
	call	handle_illegal_c
	br	ret_from_exception

handle_diverror:
	call	handle_diverror_c
	br	ret_from_exception

#ifdef CONFIG_KGDB
handle_kgdb_breakpoint:
	call	kgdb_breakpoint_c
	br	ret_from_exception
#endif

/*
 * Beware - when entering resume, prev (the current task) is
 * in r4, next (the new task) is in r5, don't change these
 * registers.
 */
ENTRY(resume)

	rdctl	r7, status			/* save thread status reg */
	stw	r7, TASK_THREAD + THREAD_KPSR(r4)

	andi	r7, r7, %lo(~STATUS_PIE)	/* disable interrupts */
	wrctl	status, r7

	SAVE_SWITCH_STACK
	stw	sp, TASK_THREAD + THREAD_KSP(r4)/* save kernel stack pointer */
	ldw	sp, TASK_THREAD + THREAD_KSP(r5)/* restore new thread stack */
	movia	r24, _current_thread		/* save thread */
	GET_THREAD_INFO r1
	stw	r1, 0(r24)
	RESTORE_SWITCH_STACK

	ldw	r7, TASK_THREAD + THREAD_KPSR(r5)/* restore thread status reg */
	wrctl	status, r7
	ret

ENTRY(ret_from_fork)
	call	schedule_tail
	br	ret_from_exception

ENTRY(ret_from_kernel_thread)
	call	schedule_tail
	mov	r4,r17	/* arg */
	callr	r16	/* function */
	br	ret_from_exception

/*
 * Kernel user helpers.
 *
 * Each segment is 64-byte aligned and will be mapped to the <User space>.
 * New segments (if ever needed) must be added after the existing ones.
 * This mechanism should be used only for things that are really small and
 * justified, and not be abused freely.
 *
 */

 /* Filling pads with undefined instructions. */
.macro	kuser_pad sym size
	.if	((. - \sym) & 3)
	.rept	(4 - (. - \sym) & 3)
	.byte	0
	.endr
	.endif
	.rept	((\size - (. - \sym)) / 4)
	.word	0xdeadbeef
	.endr
.endm

	.align	6
	.globl	__kuser_helper_start
__kuser_helper_start:

__kuser_helper_version:				/* @ 0x1000 */
	.word	((__kuser_helper_end - __kuser_helper_start) >> 6)

__kuser_cmpxchg:				/* @ 0x1004 */
	/*
	 * r4 pointer to exchange variable
	 * r5 old value
	 * r6 new value
	 */
cmpxchg_ldw:
	ldw	r2, 0(r4)			/* load current value */
	sub	r2, r2, r5			/* compare with old value */
	bne	r2, zero, cmpxchg_ret

	/* We had a match, store the new value */
cmpxchg_stw:
	stw	r6, 0(r4)
cmpxchg_ret:
	ret

	kuser_pad __kuser_cmpxchg, 64

	.globl	__kuser_sigtramp
__kuser_sigtramp:
	movi	r2, __NR_rt_sigreturn
	trap

	kuser_pad __kuser_sigtramp, 64

	.globl	__kuser_helper_end
__kuser_helper_end: