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	stw	r2, PT_ORIG_R2(sp)
189	/* Check that the requested system call is within limits */
190	movui	r1, __NR_syscalls
191	bgeu	r2, r1, ret_invsyscall
192	slli	r1, r2, 2
193	movhi	r11, %hiadj(sys_call_table)
194	add	r1, r1, r11
195	ldw	r1, %lo(sys_call_table)(r1)
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	ldw	r1, PT_ORIG_R2(sp)
217	addi	r1, r1, 1
218	beq	r1, zero, 3f
219	sub	r2, zero, r2
220	movi	r1, 1
2213:
222	stw	r2, PT_R2(sp)
223	stw	r1, PT_R7(sp)
224end_translate_rc_and_ret:
225
226ret_from_exception:
227	ldw	r1, PT_ESTATUS(sp)
228	/* if so, skip resched, signals */
229	TSTBNZ	r1, r1, ESTATUS_EU, Luser_return
230
231restore_all:
232	rdctl	r10, status			/* disable intrs */
233	andi	r10, r10, %lo(~STATUS_PIE)
234	wrctl	status, r10
235	RESTORE_ALL
236	eret
237
238	/* If the syscall number was invalid return ENOSYS */
239ret_invsyscall:
240	movi	r2, -ENOSYS
241	br	translate_rc_and_ret
242
243	/* This implements the same as above, except it calls
244	 * do_syscall_trace_enter and do_syscall_trace_exit before and after the
245	 * syscall in order for utilities like strace and gdb to work.
246	 */
247traced_system_call:
248	SAVE_SWITCH_STACK
249	call	do_syscall_trace_enter
250	RESTORE_SWITCH_STACK
251
252	/* Create system call register arguments. The 5th and 6th
253	   arguments on stack are already in place at the beginning
254	   of pt_regs. */
255	ldw	r2, PT_R2(sp)
256	ldw	r4, PT_R4(sp)
257	ldw	r5, PT_R5(sp)
258	ldw	r6, PT_R6(sp)
259	ldw	r7, PT_R7(sp)
260
261	/* Fetch the syscall function. */
262	movui	r1, __NR_syscalls
263	bgeu	r2, r1, traced_invsyscall
264	slli	r1, r2, 2
265	movhi	r11,%hiadj(sys_call_table)
266	add	r1, r1, r11
267	ldw	r1, %lo(sys_call_table)(r1)
268
269	callr	r1
270
271	/* If the syscall returns a negative result:
272	 *   Set r7 to 1 to indicate error,
273	 *   Negate r2 to get a positive error code
274	 * If the syscall returns zero or a positive value:
275	 *   Set r7 to 0.
276	 * The sigreturn system calls will skip the code below by
277	 * adding to register ra. To avoid destroying registers
278	 */
279translate_rc_and_ret2:
280	movi	r1, 0
281	bge	r2, zero, 4f
282	ldw	r1, PT_ORIG_R2(sp)
283	addi	r1, r1, 1
284	beq	r1, zero, 4f
285	sub	r2, zero, r2
286	movi	r1, 1
2874:
288	stw	r2, PT_R2(sp)
289	stw	r1, PT_R7(sp)
290end_translate_rc_and_ret2:
291	SAVE_SWITCH_STACK
292	call	do_syscall_trace_exit
293	RESTORE_SWITCH_STACK
294	br	ret_from_exception
295
296	/* If the syscall number was invalid return ENOSYS */
297traced_invsyscall:
298	movi	r2, -ENOSYS
299	br	translate_rc_and_ret2
300
301Luser_return:
302	GET_THREAD_INFO	r11			/* get thread_info pointer */
303	ldw	r10, TI_FLAGS(r11)		/* get thread_info->flags */
304	ANDI32	r11, r10, _TIF_WORK_MASK
305	beq	r11, r0, restore_all		/* Nothing to do */
306	BTBZ	r1, r10, TIF_NEED_RESCHED, Lsignal_return
307
308	/* Reschedule work */
309	call	schedule
310	br	ret_from_exception
311
312Lsignal_return:
313	ANDI32	r1, r10, _TIF_SIGPENDING | _TIF_NOTIFY_RESUME
314	beq	r1, r0, restore_all
315	mov	r4, sp			/* pt_regs */
316	SAVE_SWITCH_STACK
317	call	do_notify_resume
318	beq	r2, r0, no_work_pending
319	RESTORE_SWITCH_STACK
320	/* prepare restart syscall here without leaving kernel */
321	ldw	r2, PT_R2(sp)	/* reload syscall number in r2 */
322	ldw 	r4, PT_R4(sp)	/* reload syscall arguments r4-r9 */
323	ldw 	r5, PT_R5(sp)
324	ldw 	r6, PT_R6(sp)
325	ldw 	r7, PT_R7(sp)
326	ldw 	r8, PT_R8(sp)
327	ldw 	r9, PT_R9(sp)
328	br	local_restart	/* restart syscall */
329
330no_work_pending:
331	RESTORE_SWITCH_STACK
332	br	ret_from_exception
333
334/***********************************************************************
335 * Handle external interrupts.
336 ***********************************************************************
337 */
338/*
339 * This is the generic interrupt handler (for all hardware interrupt
340 * sources). It figures out the vector number and calls the appropriate
341 * interrupt service routine directly.
342 */
343external_interrupt:
344	rdctl	r12, ipending
345	rdctl	r9, ienable
346	and	r12, r12, r9
347	/* skip if no interrupt is pending */
348	beq	r12, r0, ret_from_interrupt
349
350	/*
351	 * Process an external hardware interrupt.
352	 */
353
354	addi	ea, ea, -4	/* re-issue the interrupted instruction */
355	stw	ea, PT_EA(sp)
3562:	movi	r4, %lo(-1)	/* Start from bit position 0,
357					highest priority */
358				/* This is the IRQ # for handler call */
3591:	andi	r10, r12, 1	/* Isolate bit we are interested in */
360	srli	r12, r12, 1	/* shift count is costly without hardware
361					multiplier */
362	addi	r4, r4, 1
363	beq	r10, r0, 1b
364	mov	r5, sp		/* Setup pt_regs pointer for handler call */
365	call	do_IRQ
366	rdctl	r12, ipending	/* check again if irq still pending */
367	rdctl	r9, ienable	/* Isolate possible interrupts */
368	and	r12, r12, r9
369	bne	r12, r0, 2b
370	/* br	ret_from_interrupt */ /* fall through to ret_from_interrupt */
371
372ENTRY(ret_from_interrupt)
373	ldw	r1, PT_ESTATUS(sp)	/* check if returning to kernel */
374	TSTBNZ	r1, r1, ESTATUS_EU, Luser_return
375
376#ifdef CONFIG_PREEMPTION
377	GET_THREAD_INFO	r1
378	ldw	r4, TI_PREEMPT_COUNT(r1)
379	bne	r4, r0, restore_all
380	ldw	r4, TI_FLAGS(r1)		/* ? Need resched set */
381	BTBZ	r10, r4, TIF_NEED_RESCHED, restore_all
382	ldw	r4, PT_ESTATUS(sp)	/* ? Interrupts off */
383	andi	r10, r4, ESTATUS_EPIE
384	beq	r10, r0, restore_all
385	call	preempt_schedule_irq
386#endif
387	br	restore_all
388
389/***********************************************************************
390 * A few syscall wrappers
391 ***********************************************************************
392 */
393/*
394 * int clone(unsigned long clone_flags, unsigned long newsp,
395 *		int __user * parent_tidptr, int __user * child_tidptr,
396 *		int tls_val)
397 */
398ENTRY(sys_clone)
399	SAVE_SWITCH_STACK
400	subi    sp, sp, 4 /* make space for tls pointer */
401	stw     r8, 0(sp) /* pass tls pointer (r8) via stack (5th argument) */
402	call	nios2_clone
403	addi    sp, sp, 4
404	RESTORE_SWITCH_STACK
405	ret
406
407ENTRY(sys_rt_sigreturn)
408	SAVE_SWITCH_STACK
409	mov	r4, sp
410	call	do_rt_sigreturn
411	RESTORE_SWITCH_STACK
412	addi	ra, ra, (end_translate_rc_and_ret - translate_rc_and_ret)
413	ret
414
415/***********************************************************************
416 * A few other wrappers and stubs
417 ***********************************************************************
418 */
419protection_exception_pte:
420	rdctl	r6, pteaddr
421	slli	r6, r6, 10
422	call	do_page_fault
423	br	ret_from_exception
424
425protection_exception_ba:
426	rdctl	r6, badaddr
427	call	do_page_fault
428	br	ret_from_exception
429
430protection_exception_instr:
431	call	handle_supervisor_instr
432	br	ret_from_exception
433
434handle_breakpoint:
435	call	breakpoint_c
436	br	ret_from_exception
437
438#ifdef CONFIG_NIOS2_ALIGNMENT_TRAP
439handle_unaligned:
440	SAVE_SWITCH_STACK
441	call	handle_unaligned_c
442	RESTORE_SWITCH_STACK
443	br	ret_from_exception
444#else
445handle_unaligned:
446	call	handle_unaligned_c
447	br	ret_from_exception
448#endif
449
450handle_illegal:
451	call	handle_illegal_c
452	br	ret_from_exception
453
454handle_diverror:
455	call	handle_diverror_c
456	br	ret_from_exception
457
458#ifdef CONFIG_KGDB
459handle_kgdb_breakpoint:
460	call	kgdb_breakpoint_c
461	br	ret_from_exception
462#endif
463
464handle_trap_1:
465	call	handle_trap_1_c
466	br	ret_from_exception
467
468handle_trap_2:
469	call	handle_trap_2_c
470	br	ret_from_exception
471
472handle_trap_3:
473handle_trap_reserved:
474	call	handle_trap_3_c
475	br	ret_from_exception
476
477/*
478 * Beware - when entering resume, prev (the current task) is
479 * in r4, next (the new task) is in r5, don't change these
480 * registers.
481 */
482ENTRY(resume)
483
484	rdctl	r7, status			/* save thread status reg */
485	stw	r7, TASK_THREAD + THREAD_KPSR(r4)
486
487	andi	r7, r7, %lo(~STATUS_PIE)	/* disable interrupts */
488	wrctl	status, r7
489
490	SAVE_SWITCH_STACK
491	stw	sp, TASK_THREAD + THREAD_KSP(r4)/* save kernel stack pointer */
492	ldw	sp, TASK_THREAD + THREAD_KSP(r5)/* restore new thread stack */
493	movia	r24, _current_thread		/* save thread */
494	GET_THREAD_INFO r1
495	stw	r1, 0(r24)
496	RESTORE_SWITCH_STACK
497
498	ldw	r7, TASK_THREAD + THREAD_KPSR(r5)/* restore thread status reg */
499	wrctl	status, r7
500	ret
501
502ENTRY(ret_from_fork)
503	call	schedule_tail
504	br	ret_from_exception
505
506ENTRY(ret_from_kernel_thread)
507	call	schedule_tail
508	mov	r4,r17	/* arg */
509	callr	r16	/* function */
510	br	ret_from_exception
511
512/*
513 * Kernel user helpers.
514 *
515 * Each segment is 64-byte aligned and will be mapped to the <User space>.
516 * New segments (if ever needed) must be added after the existing ones.
517 * This mechanism should be used only for things that are really small and
518 * justified, and not be abused freely.
519 *
520 */
521
522 /* Filling pads with undefined instructions. */
523.macro	kuser_pad sym size
524	.if	((. - \sym) & 3)
525	.rept	(4 - (. - \sym) & 3)
526	.byte	0
527	.endr
528	.endif
529	.rept	((\size - (. - \sym)) / 4)
530	.word	0xdeadbeef
531	.endr
532.endm
533
534	.align	6
535	.globl	__kuser_helper_start
536__kuser_helper_start:
537
538__kuser_helper_version:				/* @ 0x1000 */
539	.word	((__kuser_helper_end - __kuser_helper_start) >> 6)
540
541__kuser_cmpxchg:				/* @ 0x1004 */
542	/*
543	 * r4 pointer to exchange variable
544	 * r5 old value
545	 * r6 new value
546	 */
547cmpxchg_ldw:
548	ldw	r2, 0(r4)			/* load current value */
549	sub	r2, r2, r5			/* compare with old value */
550	bne	r2, zero, cmpxchg_ret
551
552	/* We had a match, store the new value */
553cmpxchg_stw:
554	stw	r6, 0(r4)
555cmpxchg_ret:
556	ret
557
558	kuser_pad __kuser_cmpxchg, 64
559
560	.globl	__kuser_sigtramp
561__kuser_sigtramp:
562	movi	r2, __NR_rt_sigreturn
563	trap
564
565	kuser_pad __kuser_sigtramp, 64
566
567	.globl	__kuser_helper_end
568__kuser_helper_end:
569