xref: /openbmc/linux/arch/arm/kernel/entry-common.S (revision 6774def6) 
1/*
2 *  linux/arch/arm/kernel/entry-common.S
3 *
4 *  Copyright (C) 2000 Russell King
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11#include <asm/assembler.h>
12#include <asm/unistd.h>
13#include <asm/ftrace.h>
14#include <asm/unwind.h>
15
16#ifdef CONFIG_NEED_RET_TO_USER
17#include <mach/entry-macro.S>
18#else
19	.macro  arch_ret_to_user, tmp1, tmp2
20	.endm
21#endif
22
23#include "entry-header.S"
24
25
26	.align	5
27/*
28 * This is the fast syscall return path.  We do as little as
29 * possible here, and this includes saving r0 back into the SVC
30 * stack.
31 */
32ret_fast_syscall:
33 UNWIND(.fnstart	)
34 UNWIND(.cantunwind	)
35	disable_irq				@ disable interrupts
36	ldr	r1, [tsk, #TI_FLAGS]
37	tst	r1, #_TIF_WORK_MASK
38	bne	fast_work_pending
39	asm_trace_hardirqs_on
40
41	/* perform architecture specific actions before user return */
42	arch_ret_to_user r1, lr
43	ct_user_enter
44
45	restore_user_regs fast = 1, offset = S_OFF
46 UNWIND(.fnend		)
47
48/*
49 * Ok, we need to do extra processing, enter the slow path.
50 */
51fast_work_pending:
52	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
53work_pending:
54	mov	r0, sp				@ 'regs'
55	mov	r2, why				@ 'syscall'
56	bl	do_work_pending
57	cmp	r0, #0
58	beq	no_work_pending
59	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
60	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
61	b	local_restart			@ ... and off we go
62
63/*
64 * "slow" syscall return path.  "why" tells us if this was a real syscall.
65 */
66ENTRY(ret_to_user)
67ret_slow_syscall:
68	disable_irq				@ disable interrupts
69ENTRY(ret_to_user_from_irq)
70	ldr	r1, [tsk, #TI_FLAGS]
71	tst	r1, #_TIF_WORK_MASK
72	bne	work_pending
73no_work_pending:
74	asm_trace_hardirqs_on
75
76	/* perform architecture specific actions before user return */
77	arch_ret_to_user r1, lr
78	ct_user_enter save = 0
79
80	restore_user_regs fast = 0, offset = 0
81ENDPROC(ret_to_user_from_irq)
82ENDPROC(ret_to_user)
83
84/*
85 * This is how we return from a fork.
86 */
87ENTRY(ret_from_fork)
88	bl	schedule_tail
89	cmp	r5, #0
90	movne	r0, r4
91	adrne	lr, BSYM(1f)
92	retne	r5
931:	get_thread_info tsk
94	b	ret_slow_syscall
95ENDPROC(ret_from_fork)
96
97	.equ NR_syscalls,0
98#define CALL(x) .equ NR_syscalls,NR_syscalls+1
99#include "calls.S"
100
101/*
102 * Ensure that the system call table is equal to __NR_syscalls,
103 * which is the value the rest of the system sees
104 */
105.ifne NR_syscalls - __NR_syscalls
106.error "__NR_syscalls is not equal to the size of the syscall table"
107.endif
108
109#undef CALL
110#define CALL(x) .long x
111
112#ifdef CONFIG_FUNCTION_TRACER
113/*
114 * When compiling with -pg, gcc inserts a call to the mcount routine at the
115 * start of every function.  In mcount, apart from the function's address (in
116 * lr), we need to get hold of the function's caller's address.
117 *
118 * Older GCCs (pre-4.4) inserted a call to a routine called mcount like this:
119 *
120 *	bl	mcount
121 *
122 * These versions have the limitation that in order for the mcount routine to
123 * be able to determine the function's caller's address, an APCS-style frame
124 * pointer (which is set up with something like the code below) is required.
125 *
126 *	mov     ip, sp
127 *	push    {fp, ip, lr, pc}
128 *	sub     fp, ip, #4
129 *
130 * With EABI, these frame pointers are not available unless -mapcs-frame is
131 * specified, and if building as Thumb-2, not even then.
132 *
133 * Newer GCCs (4.4+) solve this problem by introducing a new version of mcount,
134 * with call sites like:
135 *
136 *	push	{lr}
137 *	bl	__gnu_mcount_nc
138 *
139 * With these compilers, frame pointers are not necessary.
140 *
141 * mcount can be thought of as a function called in the middle of a subroutine
142 * call.  As such, it needs to be transparent for both the caller and the
143 * callee: the original lr needs to be restored when leaving mcount, and no
144 * registers should be clobbered.  (In the __gnu_mcount_nc implementation, we
145 * clobber the ip register.  This is OK because the ARM calling convention
146 * allows it to be clobbered in subroutines and doesn't use it to hold
147 * parameters.)
148 *
149 * When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0"
150 * for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see
151 * arch/arm/kernel/ftrace.c).
152 */
153
154#ifndef CONFIG_OLD_MCOUNT
155#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
156#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
157#endif
158#endif
159
160.macro mcount_adjust_addr rd, rn
161	bic	\rd, \rn, #1		@ clear the Thumb bit if present
162	sub	\rd, \rd, #MCOUNT_INSN_SIZE
163.endm
164
165.macro __mcount suffix
166	mcount_enter
167	ldr	r0, =ftrace_trace_function
168	ldr	r2, [r0]
169	adr	r0, .Lftrace_stub
170	cmp	r0, r2
171	bne	1f
172
173#ifdef CONFIG_FUNCTION_GRAPH_TRACER
174	ldr     r1, =ftrace_graph_return
175	ldr     r2, [r1]
176	cmp     r0, r2
177	bne     ftrace_graph_caller\suffix
178
179	ldr     r1, =ftrace_graph_entry
180	ldr     r2, [r1]
181	ldr     r0, =ftrace_graph_entry_stub
182	cmp     r0, r2
183	bne     ftrace_graph_caller\suffix
184#endif
185
186	mcount_exit
187
1881: 	mcount_get_lr	r1			@ lr of instrumented func
189	mcount_adjust_addr	r0, lr		@ instrumented function
190	adr	lr, BSYM(2f)
191	mov	pc, r2
1922:	mcount_exit
193.endm
194
195.macro __ftrace_caller suffix
196	mcount_enter
197
198	mcount_get_lr	r1			@ lr of instrumented func
199	mcount_adjust_addr	r0, lr		@ instrumented function
200
201	.globl ftrace_call\suffix
202ftrace_call\suffix:
203	bl	ftrace_stub
204
205#ifdef CONFIG_FUNCTION_GRAPH_TRACER
206	.globl ftrace_graph_call\suffix
207ftrace_graph_call\suffix:
208	mov	r0, r0
209#endif
210
211	mcount_exit
212.endm
213
214.macro __ftrace_graph_caller
215	sub	r0, fp, #4		@ &lr of instrumented routine (&parent)
216#ifdef CONFIG_DYNAMIC_FTRACE
217	@ called from __ftrace_caller, saved in mcount_enter
218	ldr	r1, [sp, #16]		@ instrumented routine (func)
219	mcount_adjust_addr	r1, r1
220#else
221	@ called from __mcount, untouched in lr
222	mcount_adjust_addr	r1, lr	@ instrumented routine (func)
223#endif
224	mov	r2, fp			@ frame pointer
225	bl	prepare_ftrace_return
226	mcount_exit
227.endm
228
229#ifdef CONFIG_OLD_MCOUNT
230/*
231 * mcount
232 */
233
234.macro mcount_enter
235	stmdb	sp!, {r0-r3, lr}
236.endm
237
238.macro mcount_get_lr reg
239	ldr	\reg, [fp, #-4]
240.endm
241
242.macro mcount_exit
243	ldr	lr, [fp, #-4]
244	ldmia	sp!, {r0-r3, pc}
245.endm
246
247ENTRY(mcount)
248#ifdef CONFIG_DYNAMIC_FTRACE
249	stmdb	sp!, {lr}
250	ldr	lr, [fp, #-4]
251	ldmia	sp!, {pc}
252#else
253	__mcount _old
254#endif
255ENDPROC(mcount)
256
257#ifdef CONFIG_DYNAMIC_FTRACE
258ENTRY(ftrace_caller_old)
259	__ftrace_caller _old
260ENDPROC(ftrace_caller_old)
261#endif
262
263#ifdef CONFIG_FUNCTION_GRAPH_TRACER
264ENTRY(ftrace_graph_caller_old)
265	__ftrace_graph_caller
266ENDPROC(ftrace_graph_caller_old)
267#endif
268
269.purgem mcount_enter
270.purgem mcount_get_lr
271.purgem mcount_exit
272#endif
273
274/*
275 * __gnu_mcount_nc
276 */
277
278.macro mcount_enter
279/*
280 * This pad compensates for the push {lr} at the call site.  Note that we are
281 * unable to unwind through a function which does not otherwise save its lr.
282 */
283 UNWIND(.pad	#4)
284	stmdb	sp!, {r0-r3, lr}
285 UNWIND(.save	{r0-r3, lr})
286.endm
287
288.macro mcount_get_lr reg
289	ldr	\reg, [sp, #20]
290.endm
291
292.macro mcount_exit
293	ldmia	sp!, {r0-r3, ip, lr}
294	ret	ip
295.endm
296
297ENTRY(__gnu_mcount_nc)
298UNWIND(.fnstart)
299#ifdef CONFIG_DYNAMIC_FTRACE
300	mov	ip, lr
301	ldmia	sp!, {lr}
302	ret	ip
303#else
304	__mcount
305#endif
306UNWIND(.fnend)
307ENDPROC(__gnu_mcount_nc)
308
309#ifdef CONFIG_DYNAMIC_FTRACE
310ENTRY(ftrace_caller)
311UNWIND(.fnstart)
312	__ftrace_caller
313UNWIND(.fnend)
314ENDPROC(ftrace_caller)
315#endif
316
317#ifdef CONFIG_FUNCTION_GRAPH_TRACER
318ENTRY(ftrace_graph_caller)
319UNWIND(.fnstart)
320	__ftrace_graph_caller
321UNWIND(.fnend)
322ENDPROC(ftrace_graph_caller)
323#endif
324
325.purgem mcount_enter
326.purgem mcount_get_lr
327.purgem mcount_exit
328
329#ifdef CONFIG_FUNCTION_GRAPH_TRACER
330	.globl return_to_handler
331return_to_handler:
332	stmdb	sp!, {r0-r3}
333	mov	r0, fp			@ frame pointer
334	bl	ftrace_return_to_handler
335	mov	lr, r0			@ r0 has real ret addr
336	ldmia	sp!, {r0-r3}
337	ret	lr
338#endif
339
340ENTRY(ftrace_stub)
341.Lftrace_stub:
342	ret	lr
343ENDPROC(ftrace_stub)
344
345#endif /* CONFIG_FUNCTION_TRACER */
346
347/*=============================================================================
348 * SWI handler
349 *-----------------------------------------------------------------------------
350 */
351
352	.align	5
353ENTRY(vector_swi)
354#ifdef CONFIG_CPU_V7M
355	v7m_exception_entry
356#else
357	sub	sp, sp, #S_FRAME_SIZE
358	stmia	sp, {r0 - r12}			@ Calling r0 - r12
359 ARM(	add	r8, sp, #S_PC		)
360 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
361 THUMB(	mov	r8, sp			)
362 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
363	mrs	r8, spsr			@ called from non-FIQ mode, so ok.
364	str	lr, [sp, #S_PC]			@ Save calling PC
365	str	r8, [sp, #S_PSR]		@ Save CPSR
366	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
367#endif
368	zero_fp
369	alignment_trap r10, ip, __cr_alignment
370	enable_irq
371	ct_user_exit
372	get_thread_info tsk
373
374	/*
375	 * Get the system call number.
376	 */
377
378#if defined(CONFIG_OABI_COMPAT)
379
380	/*
381	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
382	 * value to determine if it is an EABI or an old ABI call.
383	 */
384#ifdef CONFIG_ARM_THUMB
385	tst	r8, #PSR_T_BIT
386	movne	r10, #0				@ no thumb OABI emulation
387 USER(	ldreq	r10, [lr, #-4]		)	@ get SWI instruction
388#else
389 USER(	ldr	r10, [lr, #-4]		)	@ get SWI instruction
390#endif
391 ARM_BE8(rev	r10, r10)			@ little endian instruction
392
393#elif defined(CONFIG_AEABI)
394
395	/*
396	 * Pure EABI user space always put syscall number into scno (r7).
397	 */
398#elif defined(CONFIG_ARM_THUMB)
399	/* Legacy ABI only, possibly thumb mode. */
400	tst	r8, #PSR_T_BIT			@ this is SPSR from save_user_regs
401	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
402 USER(	ldreq	scno, [lr, #-4]		)
403
404#else
405	/* Legacy ABI only. */
406 USER(	ldr	scno, [lr, #-4]		)	@ get SWI instruction
407#endif
408
409	adr	tbl, sys_call_table		@ load syscall table pointer
410
411#if defined(CONFIG_OABI_COMPAT)
412	/*
413	 * If the swi argument is zero, this is an EABI call and we do nothing.
414	 *
415	 * If this is an old ABI call, get the syscall number into scno and
416	 * get the old ABI syscall table address.
417	 */
418	bics	r10, r10, #0xff000000
419	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
420	ldrne	tbl, =sys_oabi_call_table
421#elif !defined(CONFIG_AEABI)
422	bic	scno, scno, #0xff000000		@ mask off SWI op-code
423	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
424#endif
425
426local_restart:
427	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
428	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
429
430	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
431	bne	__sys_trace
432
433	cmp	scno, #NR_syscalls		@ check upper syscall limit
434	adr	lr, BSYM(ret_fast_syscall)	@ return address
435	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
436
437	add	r1, sp, #S_OFF
4382:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
439	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
440	bcs	arm_syscall
441	mov	why, #0				@ no longer a real syscall
442	b	sys_ni_syscall			@ not private func
443
444#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
445	/*
446	 * We failed to handle a fault trying to access the page
447	 * containing the swi instruction, but we're not really in a
448	 * position to return -EFAULT. Instead, return back to the
449	 * instruction and re-enter the user fault handling path trying
450	 * to page it in. This will likely result in sending SEGV to the
451	 * current task.
452	 */
4539001:
454	sub	lr, lr, #4
455	str	lr, [sp, #S_PC]
456	b	ret_fast_syscall
457#endif
458ENDPROC(vector_swi)
459
460	/*
461	 * This is the really slow path.  We're going to be doing
462	 * context switches, and waiting for our parent to respond.
463	 */
464__sys_trace:
465	mov	r1, scno
466	add	r0, sp, #S_OFF
467	bl	syscall_trace_enter
468
469	adr	lr, BSYM(__sys_trace_return)	@ return address
470	mov	scno, r0			@ syscall number (possibly new)
471	add	r1, sp, #S_R0 + S_OFF		@ pointer to regs
472	cmp	scno, #NR_syscalls		@ check upper syscall limit
473	ldmccia	r1, {r0 - r6}			@ have to reload r0 - r6
474	stmccia	sp, {r4, r5}			@ and update the stack args
475	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
476	cmp	scno, #-1			@ skip the syscall?
477	bne	2b
478	add	sp, sp, #S_OFF			@ restore stack
479	b	ret_slow_syscall
480
481__sys_trace_return:
482	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
483	mov	r0, sp
484	bl	syscall_trace_exit
485	b	ret_slow_syscall
486
487	.align	5
488#ifdef CONFIG_ALIGNMENT_TRAP
489	.type	__cr_alignment, #object
490__cr_alignment:
491	.word	cr_alignment
492#endif
493	.ltorg
494
495/*
496 * This is the syscall table declaration for native ABI syscalls.
497 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
498 */
499#define ABI(native, compat) native
500#ifdef CONFIG_AEABI
501#define OBSOLETE(syscall) sys_ni_syscall
502#else
503#define OBSOLETE(syscall) syscall
504#endif
505
506	.type	sys_call_table, #object
507ENTRY(sys_call_table)
508#include "calls.S"
509#undef ABI
510#undef OBSOLETE
511
512/*============================================================================
513 * Special system call wrappers
514 */
515@ r0 = syscall number
516@ r8 = syscall table
517sys_syscall:
518		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
519		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
520		cmpne	scno, #NR_syscalls	@ check range
521		stmloia	sp, {r5, r6}		@ shuffle args
522		movlo	r0, r1
523		movlo	r1, r2
524		movlo	r2, r3
525		movlo	r3, r4
526		ldrlo	pc, [tbl, scno, lsl #2]
527		b	sys_ni_syscall
528ENDPROC(sys_syscall)
529
530sys_sigreturn_wrapper:
531		add	r0, sp, #S_OFF
532		mov	why, #0		@ prevent syscall restart handling
533		b	sys_sigreturn
534ENDPROC(sys_sigreturn_wrapper)
535
536sys_rt_sigreturn_wrapper:
537		add	r0, sp, #S_OFF
538		mov	why, #0		@ prevent syscall restart handling
539		b	sys_rt_sigreturn
540ENDPROC(sys_rt_sigreturn_wrapper)
541
542sys_statfs64_wrapper:
543		teq	r1, #88
544		moveq	r1, #84
545		b	sys_statfs64
546ENDPROC(sys_statfs64_wrapper)
547
548sys_fstatfs64_wrapper:
549		teq	r1, #88
550		moveq	r1, #84
551		b	sys_fstatfs64
552ENDPROC(sys_fstatfs64_wrapper)
553
554/*
555 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
556 * offset, we return EINVAL.
557 */
558sys_mmap2:
559#if PAGE_SHIFT > 12
560		tst	r5, #PGOFF_MASK
561		moveq	r5, r5, lsr #PAGE_SHIFT - 12
562		streq	r5, [sp, #4]
563		beq	sys_mmap_pgoff
564		mov	r0, #-EINVAL
565		ret	lr
566#else
567		str	r5, [sp, #4]
568		b	sys_mmap_pgoff
569#endif
570ENDPROC(sys_mmap2)
571
572#ifdef CONFIG_OABI_COMPAT
573
574/*
575 * These are syscalls with argument register differences
576 */
577
578sys_oabi_pread64:
579		stmia	sp, {r3, r4}
580		b	sys_pread64
581ENDPROC(sys_oabi_pread64)
582
583sys_oabi_pwrite64:
584		stmia	sp, {r3, r4}
585		b	sys_pwrite64
586ENDPROC(sys_oabi_pwrite64)
587
588sys_oabi_truncate64:
589		mov	r3, r2
590		mov	r2, r1
591		b	sys_truncate64
592ENDPROC(sys_oabi_truncate64)
593
594sys_oabi_ftruncate64:
595		mov	r3, r2
596		mov	r2, r1
597		b	sys_ftruncate64
598ENDPROC(sys_oabi_ftruncate64)
599
600sys_oabi_readahead:
601		str	r3, [sp]
602		mov	r3, r2
603		mov	r2, r1
604		b	sys_readahead
605ENDPROC(sys_oabi_readahead)
606
607/*
608 * Let's declare a second syscall table for old ABI binaries
609 * using the compatibility syscall entries.
610 */
611#define ABI(native, compat) compat
612#define OBSOLETE(syscall) syscall
613
614	.type	sys_oabi_call_table, #object
615ENTRY(sys_oabi_call_table)
616#include "calls.S"
617#undef ABI
618#undef OBSOLETE
619
620#endif
621
622