xref: /openbmc/linux/arch/nios2/kernel/entry.S (revision 94cdda6b)
1/*
2 * linux/arch/nios2/kernel/entry.S
3 *
4 * Copyright (C) 2013-2014  Altera Corporation
5 * Copyright (C) 2009, Wind River Systems Inc
6 *
7 * Implemented by fredrik.markstrom@gmail.com and ivarholmqvist@gmail.com
8 *
9 *  Copyright (C) 1999-2002, Greg Ungerer (gerg@snapgear.com)
10 *  Copyright (C) 1998  D. Jeff Dionne <jeff@lineo.ca>,
11 *                      Kenneth Albanowski <kjahds@kjahds.com>,
12 *  Copyright (C) 2000  Lineo Inc. (www.lineo.com)
13 *  Copyright (C) 2004  Microtronix Datacom Ltd.
14 *
15 * This file is subject to the terms and conditions of the GNU General Public
16 * License.  See the file "COPYING" in the main directory of this archive
17 * for more details.
18 *
19 * Linux/m68k support by Hamish Macdonald
20 *
21 * 68060 fixes by Jesper Skov
22 * ColdFire support by Greg Ungerer (gerg@snapgear.com)
23 * 5307 fixes by David W. Miller
24 * linux 2.4 support David McCullough <davidm@snapgear.com>
25 */
26
27#include <linux/sys.h>
28#include <linux/linkage.h>
29#include <asm/asm-offsets.h>
30#include <asm/asm-macros.h>
31#include <asm/thread_info.h>
32#include <asm/errno.h>
33#include <asm/setup.h>
34#include <asm/entry.h>
35#include <asm/unistd.h>
36#include <asm/processor.h>
37
38.macro GET_THREAD_INFO reg
39.if THREAD_SIZE & 0xffff0000
40	andhi	\reg, sp, %hi(~(THREAD_SIZE-1))
41.else
42	addi	\reg, r0, %lo(~(THREAD_SIZE-1))
43	and	\reg, \reg, sp
44.endif
45.endm
46
47.macro	kuser_cmpxchg_check
48	/*
49	 * Make sure our user space atomic helper is restarted if it was
50	 * interrupted in a critical region.
51	 * ea-4 = address of interrupted insn (ea must be preserved).
52	 * sp = saved regs.
53	 * cmpxchg_ldw = first critical insn, cmpxchg_stw = last critical insn.
54	 * If ea <= cmpxchg_stw and ea > cmpxchg_ldw then saved EA is set to
55	 * cmpxchg_ldw + 4.
56	*/
57	/* et = cmpxchg_stw + 4 */
58	movui   et, (KUSER_BASE + 4 + (cmpxchg_stw - __kuser_helper_start))
59	bgtu	ea, et, 1f
60
61	subi	et, et, (cmpxchg_stw - cmpxchg_ldw) /* et = cmpxchg_ldw + 4 */
62	bltu	ea, et, 1f
63	stw	et, PT_EA(sp)	/* fix up EA */
64	mov	ea, et
651:
66.endm
67
68.section .rodata
69.align 4
70exception_table:
71	.word unhandled_exception	/* 0 - Reset */
72	.word unhandled_exception	/* 1 - Processor-only Reset */
73	.word external_interrupt	/* 2 - Interrupt */
74	.word handle_trap		/* 3 - Trap Instruction */
75
76	.word instruction_trap		/* 4 - Unimplemented instruction */
77	.word handle_illegal		/* 5 - Illegal instruction */
78	.word handle_unaligned		/* 6 - Misaligned data access */
79	.word handle_unaligned		/* 7 - Misaligned destination address */
80
81	.word handle_diverror		/* 8 - Division error */
82	.word protection_exception_ba	/* 9 - Supervisor-only instr. address */
83	.word protection_exception_instr /* 10 - Supervisor only instruction */
84	.word protection_exception_ba	/* 11 - Supervisor only data address */
85
86	.word unhandled_exception	/* 12 - Double TLB miss (data) */
87	.word protection_exception_pte	/* 13 - TLB permission violation (x) */
88	.word protection_exception_pte	/* 14 - TLB permission violation (r) */
89	.word protection_exception_pte	/* 15 - TLB permission violation (w) */
90
91	.word unhandled_exception	/* 16 - MPU region violation */
92
93trap_table:
94	.word	handle_system_call	/* 0  */
95	.word	handle_trap_1		/* 1  */
96	.word	handle_trap_2		/* 2  */
97	.word	handle_trap_3		/* 3  */
98	.word	handle_trap_reserved	/* 4  */
99	.word	handle_trap_reserved	/* 5  */
100	.word	handle_trap_reserved	/* 6  */
101	.word	handle_trap_reserved	/* 7  */
102	.word	handle_trap_reserved	/* 8  */
103	.word	handle_trap_reserved	/* 9  */
104	.word	handle_trap_reserved	/* 10 */
105	.word	handle_trap_reserved	/* 11 */
106	.word	handle_trap_reserved	/* 12 */
107	.word	handle_trap_reserved	/* 13 */
108	.word	handle_trap_reserved	/* 14 */
109	.word	handle_trap_reserved	/* 15 */
110	.word	handle_trap_reserved	/* 16 */
111	.word	handle_trap_reserved	/* 17 */
112	.word	handle_trap_reserved	/* 18 */
113	.word	handle_trap_reserved	/* 19 */
114	.word	handle_trap_reserved	/* 20 */
115	.word	handle_trap_reserved	/* 21 */
116	.word	handle_trap_reserved	/* 22 */
117	.word	handle_trap_reserved	/* 23 */
118	.word	handle_trap_reserved	/* 24 */
119	.word	handle_trap_reserved	/* 25 */
120	.word	handle_trap_reserved	/* 26 */
121	.word	handle_trap_reserved	/* 27 */
122	.word	handle_trap_reserved	/* 28 */
123	.word	handle_trap_reserved	/* 29 */
124#ifdef CONFIG_KGDB
125	.word	handle_kgdb_breakpoint	/* 30 KGDB breakpoint */
126#else
127	.word	instruction_trap		/* 30 */
128#endif
129	.word	handle_breakpoint	/* 31 */
130
131.text
132.set noat
133.set nobreak
134
135ENTRY(inthandler)
136	SAVE_ALL
137
138	kuser_cmpxchg_check
139
140	/* Clear EH bit before we get a new excpetion in the kernel
141	 * and after we have saved it to the exception frame. This is done
142	 * whether it's trap, tlb-miss or interrupt. If we don't do this
143	 * estatus is not updated the next exception.
144	 */
145	rdctl	r24, status
146	movi	r9, %lo(~STATUS_EH)
147	and	r24, r24, r9
148	wrctl	status, r24
149
150	/* Read cause and vector and branch to the associated handler */
151	mov	r4, sp
152	rdctl	r5, exception
153	movia	r9, exception_table
154	add	r24, r9, r5
155	ldw	r24, 0(r24)
156	jmp	r24
157
158
159/***********************************************************************
160 * Handle traps
161 ***********************************************************************
162 */
163ENTRY(handle_trap)
164	ldwio	r24, -4(ea)	/* instruction that caused the exception */
165	srli	r24, r24, 4
166	andi	r24, r24, 0x7c
167	movia	r9,trap_table
168	add	r24, r24, r9
169	ldw	r24, 0(r24)
170	jmp	r24
171
172
173/***********************************************************************
174 * Handle system calls
175 ***********************************************************************
176 */
177ENTRY(handle_system_call)
178	/* Enable interrupts */
179	rdctl	r10, status
180	ori	r10, r10, STATUS_PIE
181	wrctl	status, r10
182
183	/* Reload registers destroyed by common code. */
184	ldw	r4, PT_R4(sp)
185	ldw	r5, PT_R5(sp)
186
187local_restart:
188	/* Check that the requested system call is within limits */
189	movui	r1, __NR_syscalls
190	bgeu	r2, r1, ret_invsyscall
191	slli	r1, r2, 2
192	movhi	r11, %hiadj(sys_call_table)
193	add	r1, r1, r11
194	ldw	r1, %lo(sys_call_table)(r1)
195	beq	r1, r0, ret_invsyscall
196
197	/* Check if we are being traced */
198	GET_THREAD_INFO r11
199	ldw	r11,TI_FLAGS(r11)
200	BTBNZ   r11,r11,TIF_SYSCALL_TRACE,traced_system_call
201
202	/* Execute the system call */
203	callr	r1
204
205	/* If the syscall returns a negative result:
206	 *   Set r7 to 1 to indicate error,
207	 *   Negate r2 to get a positive error code
208	 * If the syscall returns zero or a positive value:
209	 *   Set r7 to 0.
210	 * The sigreturn system calls will skip the code below by
211	 * adding to register ra. To avoid destroying registers
212	 */
213translate_rc_and_ret:
214	movi	r1, 0
215	bge	r2, zero, 3f
216	sub	r2, zero, r2
217	movi	r1, 1
2183:
219	stw	r2, PT_R2(sp)
220	stw	r1, PT_R7(sp)
221end_translate_rc_and_ret:
222
223ret_from_exception:
224	ldw	r1, PT_ESTATUS(sp)
225	/* if so, skip resched, signals */
226	TSTBNZ	r1, r1, ESTATUS_EU, Luser_return
227
228restore_all:
229	rdctl	r10, status			/* disable intrs */
230	andi	r10, r10, %lo(~STATUS_PIE)
231	wrctl	status, r10
232	RESTORE_ALL
233	eret
234
235	/* If the syscall number was invalid return ENOSYS */
236ret_invsyscall:
237	movi	r2, -ENOSYS
238	br	translate_rc_and_ret
239
240	/* This implements the same as above, except it calls
241	 * do_syscall_trace_enter and do_syscall_trace_exit before and after the
242	 * syscall in order for utilities like strace and gdb to work.
243	 */
244traced_system_call:
245	SAVE_SWITCH_STACK
246	call	do_syscall_trace_enter
247	RESTORE_SWITCH_STACK
248
249	/* Create system call register arguments. The 5th and 6th
250	   arguments on stack are already in place at the beginning
251	   of pt_regs. */
252	ldw	r2, PT_R2(sp)
253	ldw	r4, PT_R4(sp)
254	ldw	r5, PT_R5(sp)
255	ldw	r6, PT_R6(sp)
256	ldw	r7, PT_R7(sp)
257
258	/* Fetch the syscall function, we don't need to check the boundaries
259	 * since this is already done.
260	 */
261	slli	r1, r2, 2
262	movhi	r11,%hiadj(sys_call_table)
263	add	r1, r1, r11
264	ldw	r1, %lo(sys_call_table)(r1)
265
266	callr	r1
267
268	/* If the syscall returns a negative result:
269	 *   Set r7 to 1 to indicate error,
270	 *   Negate r2 to get a positive error code
271	 * If the syscall returns zero or a positive value:
272	 *   Set r7 to 0.
273	 * The sigreturn system calls will skip the code below by
274	 * adding to register ra. To avoid destroying registers
275	 */
276translate_rc_and_ret2:
277	movi	r1, 0
278	bge	r2, zero, 4f
279	sub	r2, zero, r2
280	movi	r1, 1
2814:
282	stw	r2, PT_R2(sp)
283	stw	r1, PT_R7(sp)
284end_translate_rc_and_ret2:
285	SAVE_SWITCH_STACK
286	call	do_syscall_trace_exit
287	RESTORE_SWITCH_STACK
288	br	ret_from_exception
289
290Luser_return:
291	GET_THREAD_INFO	r11			/* get thread_info pointer */
292	ldw	r10, TI_FLAGS(r11)		/* get thread_info->flags */
293	ANDI32	r11, r10, _TIF_WORK_MASK
294	beq	r11, r0, restore_all		/* Nothing to do */
295	BTBZ	r1, r10, TIF_NEED_RESCHED, Lsignal_return
296
297	/* Reschedule work */
298	call	schedule
299	br	ret_from_exception
300
301Lsignal_return:
302	ANDI32	r1, r10, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME
303	beq	r1, r0, restore_all
304	mov	r4, sp			/* pt_regs */
305	SAVE_SWITCH_STACK
306	call	do_notify_resume
307	beq	r2, r0, no_work_pending
308	RESTORE_SWITCH_STACK
309	/* prepare restart syscall here without leaving kernel */
310	ldw	r2, PT_R2(sp)	/* reload syscall number in r2 */
311	ldw 	r4, PT_R4(sp)	/* reload syscall arguments r4-r9 */
312	ldw 	r5, PT_R5(sp)
313	ldw 	r6, PT_R6(sp)
314	ldw 	r7, PT_R7(sp)
315	ldw 	r8, PT_R8(sp)
316	ldw 	r9, PT_R9(sp)
317	br	local_restart	/* restart syscall */
318
319no_work_pending:
320	RESTORE_SWITCH_STACK
321	br	ret_from_exception
322
323/***********************************************************************
324 * Handle external interrupts.
325 ***********************************************************************
326 */
327/*
328 * This is the generic interrupt handler (for all hardware interrupt
329 * sources). It figures out the vector number and calls the appropriate
330 * interrupt service routine directly.
331 */
332external_interrupt:
333	rdctl	r12, ipending
334	rdctl	r9, ienable
335	and	r12, r12, r9
336	/* skip if no interrupt is pending */
337	beq	r12, r0, ret_from_interrupt
338
339	movi	r24, -1
340	stw	r24, PT_ORIG_R2(sp)
341
342	/*
343	 * Process an external hardware interrupt.
344	 */
345
346	addi	ea, ea, -4	/* re-issue the interrupted instruction */
347	stw	ea, PT_EA(sp)
3482:	movi	r4, %lo(-1)	/* Start from bit position 0,
349					highest priority */
350				/* This is the IRQ # for handler call */
3511:	andi	r10, r12, 1	/* Isolate bit we are interested in */
352	srli	r12, r12, 1	/* shift count is costly without hardware
353					multiplier */
354	addi	r4, r4, 1
355	beq	r10, r0, 1b
356	mov	r5, sp		/* Setup pt_regs pointer for handler call */
357	call	do_IRQ
358	rdctl	r12, ipending	/* check again if irq still pending */
359	rdctl	r9, ienable	/* Isolate possible interrupts */
360	and	r12, r12, r9
361	bne	r12, r0, 2b
362	/* br	ret_from_interrupt */ /* fall through to ret_from_interrupt */
363
364ENTRY(ret_from_interrupt)
365	ldw	r1, PT_ESTATUS(sp)	/* check if returning to kernel */
366	TSTBNZ	r1, r1, ESTATUS_EU, Luser_return
367
368#ifdef CONFIG_PREEMPT
369	GET_THREAD_INFO	r1
370	ldw	r4, TI_PREEMPT_COUNT(r1)
371	bne	r4, r0, restore_all
372	ldw	r4, TI_FLAGS(r1)		/* ? Need resched set */
373	BTBZ	r10, r4, TIF_NEED_RESCHED, restore_all
374	ldw	r4, PT_ESTATUS(sp)	/* ? Interrupts off */
375	andi	r10, r4, ESTATUS_EPIE
376	beq	r10, r0, restore_all
377	call	preempt_schedule_irq
378#endif
379	br	restore_all
380
381/***********************************************************************
382 * A few syscall wrappers
383 ***********************************************************************
384 */
385/*
386 * int clone(unsigned long clone_flags, unsigned long newsp,
387 *		int __user * parent_tidptr, int __user * child_tidptr,
388 *		int tls_val)
389 */
390ENTRY(sys_clone)
391	SAVE_SWITCH_STACK
392	addi	sp, sp, -4
393	stw	r7, 0(sp)	/* Pass 5th arg thru stack */
394	mov	r7, r6		/* 4th arg is 3rd of clone() */
395	mov	r6, zero	/* 3rd arg always 0 */
396	call	do_fork
397	addi	sp, sp, 4
398	RESTORE_SWITCH_STACK
399	ret
400
401ENTRY(sys_rt_sigreturn)
402	SAVE_SWITCH_STACK
403	mov	r4, sp
404	call	do_rt_sigreturn
405	RESTORE_SWITCH_STACK
406	addi	ra, ra, (end_translate_rc_and_ret - translate_rc_and_ret)
407	ret
408
409/***********************************************************************
410 * A few other wrappers and stubs
411 ***********************************************************************
412 */
413protection_exception_pte:
414	rdctl	r6, pteaddr
415	slli	r6, r6, 10
416	call	do_page_fault
417	br	ret_from_exception
418
419protection_exception_ba:
420	rdctl	r6, badaddr
421	call	do_page_fault
422	br	ret_from_exception
423
424protection_exception_instr:
425	call	handle_supervisor_instr
426	br	ret_from_exception
427
428handle_breakpoint:
429	call	breakpoint_c
430	br	ret_from_exception
431
432#ifdef CONFIG_NIOS2_ALIGNMENT_TRAP
433handle_unaligned:
434	SAVE_SWITCH_STACK
435	call	handle_unaligned_c
436	RESTORE_SWITCH_STACK
437	br	ret_from_exception
438#else
439handle_unaligned:
440	call	handle_unaligned_c
441	br	ret_from_exception
442#endif
443
444handle_illegal:
445	call	handle_illegal_c
446	br	ret_from_exception
447
448handle_diverror:
449	call	handle_diverror_c
450	br	ret_from_exception
451
452#ifdef CONFIG_KGDB
453handle_kgdb_breakpoint:
454	call	kgdb_breakpoint_c
455	br	ret_from_exception
456#endif
457
458handle_trap_1:
459	call	handle_trap_1_c
460	br	ret_from_exception
461
462handle_trap_2:
463	call	handle_trap_2_c
464	br	ret_from_exception
465
466handle_trap_3:
467handle_trap_reserved:
468	call	handle_trap_3_c
469	br	ret_from_exception
470
471/*
472 * Beware - when entering resume, prev (the current task) is
473 * in r4, next (the new task) is in r5, don't change these
474 * registers.
475 */
476ENTRY(resume)
477
478	rdctl	r7, status			/* save thread status reg */
479	stw	r7, TASK_THREAD + THREAD_KPSR(r4)
480
481	andi	r7, r7, %lo(~STATUS_PIE)	/* disable interrupts */
482	wrctl	status, r7
483
484	SAVE_SWITCH_STACK
485	stw	sp, TASK_THREAD + THREAD_KSP(r4)/* save kernel stack pointer */
486	ldw	sp, TASK_THREAD + THREAD_KSP(r5)/* restore new thread stack */
487	movia	r24, _current_thread		/* save thread */
488	GET_THREAD_INFO r1
489	stw	r1, 0(r24)
490	RESTORE_SWITCH_STACK
491
492	ldw	r7, TASK_THREAD + THREAD_KPSR(r5)/* restore thread status reg */
493	wrctl	status, r7
494	ret
495
496ENTRY(ret_from_fork)
497	call	schedule_tail
498	br	ret_from_exception
499
500ENTRY(ret_from_kernel_thread)
501	call	schedule_tail
502	mov	r4,r17	/* arg */
503	callr	r16	/* function */
504	br	ret_from_exception
505
506/*
507 * Kernel user helpers.
508 *
509 * Each segment is 64-byte aligned and will be mapped to the <User space>.
510 * New segments (if ever needed) must be added after the existing ones.
511 * This mechanism should be used only for things that are really small and
512 * justified, and not be abused freely.
513 *
514 */
515
516 /* Filling pads with undefined instructions. */
517.macro	kuser_pad sym size
518	.if	((. - \sym) & 3)
519	.rept	(4 - (. - \sym) & 3)
520	.byte	0
521	.endr
522	.endif
523	.rept	((\size - (. - \sym)) / 4)
524	.word	0xdeadbeef
525	.endr
526.endm
527
528	.align	6
529	.globl	__kuser_helper_start
530__kuser_helper_start:
531
532__kuser_helper_version:				/* @ 0x1000 */
533	.word	((__kuser_helper_end - __kuser_helper_start) >> 6)
534
535__kuser_cmpxchg:				/* @ 0x1004 */
536	/*
537	 * r4 pointer to exchange variable
538	 * r5 old value
539	 * r6 new value
540	 */
541cmpxchg_ldw:
542	ldw	r2, 0(r4)			/* load current value */
543	sub	r2, r2, r5			/* compare with old value */
544	bne	r2, zero, cmpxchg_ret
545
546	/* We had a match, store the new value */
547cmpxchg_stw:
548	stw	r6, 0(r4)
549cmpxchg_ret:
550	ret
551
552	kuser_pad __kuser_cmpxchg, 64
553
554	.globl	__kuser_sigtramp
555__kuser_sigtramp:
556	movi	r2, __NR_rt_sigreturn
557	trap
558
559	kuser_pad __kuser_sigtramp, 64
560
561	.globl	__kuser_helper_end
562__kuser_helper_end:
563