xref: /linux/arch/arm/kernel/entry-common.S (revision 26b433d0da062d6e19d75350c0171d3cf8ff560d) 
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#ifdef CONFIG_AEABI
16#include <asm/unistd-oabi.h>
17#endif
18
19	.equ	NR_syscalls, __NR_syscalls
20
21#ifdef CONFIG_NEED_RET_TO_USER
22#include <mach/entry-macro.S>
23#else
24	.macro  arch_ret_to_user, tmp1, tmp2
25	.endm
26#endif
27
28#include "entry-header.S"
29
30
31	.align	5
32#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING))
33/*
34 * This is the fast syscall return path.  We do as little as possible here,
35 * such as avoiding writing r0 to the stack.  We only use this path if we
36 * have tracing and context tracking disabled - the overheads from those
37 * features make this path too inefficient.
38 */
39ret_fast_syscall:
40 UNWIND(.fnstart	)
41 UNWIND(.cantunwind	)
42	disable_irq_notrace			@ disable interrupts
43	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
44	tst	r1, #_TIF_SYSCALL_WORK
45	bne	fast_work_pending
46	tst	r1, #_TIF_WORK_MASK
47	bne	fast_work_pending
48
49	/* perform architecture specific actions before user return */
50	arch_ret_to_user r1, lr
51
52	restore_user_regs fast = 1, offset = S_OFF
53 UNWIND(.fnend		)
54ENDPROC(ret_fast_syscall)
55
56	/* Ok, we need to do extra processing, enter the slow path. */
57fast_work_pending:
58	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
59	/* fall through to work_pending */
60#else
61/*
62 * The "replacement" ret_fast_syscall for when tracing or context tracking
63 * is enabled.  As we will need to call out to some C functions, we save
64 * r0 first to avoid needing to save registers around each C function call.
65 */
66ret_fast_syscall:
67 UNWIND(.fnstart	)
68 UNWIND(.cantunwind	)
69	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
70	disable_irq_notrace			@ disable interrupts
71	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
72	tst	r1, #_TIF_SYSCALL_WORK
73	bne	fast_work_pending
74	tst	r1, #_TIF_WORK_MASK
75	beq	no_work_pending
76 UNWIND(.fnend		)
77ENDPROC(ret_fast_syscall)
78
79	/* Slower path - fall through to work_pending */
80fast_work_pending:
81#endif
82
83	tst	r1, #_TIF_SYSCALL_WORK
84	bne	__sys_trace_return_nosave
85slow_work_pending:
86	mov	r0, sp				@ 'regs'
87	mov	r2, why				@ 'syscall'
88	bl	do_work_pending
89	cmp	r0, #0
90	beq	no_work_pending
91	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
92	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
93	b	local_restart			@ ... and off we go
94ENDPROC(ret_fast_syscall)
95
96/*
97 * "slow" syscall return path.  "why" tells us if this was a real syscall.
98 * IRQs may be enabled here, so always disable them.  Note that we use the
99 * "notrace" version to avoid calling into the tracing code unnecessarily.
100 * do_work_pending() will update this state if necessary.
101 */
102ENTRY(ret_to_user)
103ret_slow_syscall:
104	disable_irq_notrace			@ disable interrupts
105ENTRY(ret_to_user_from_irq)
106	ldr	r1, [tsk, #TI_FLAGS]
107	tst	r1, #_TIF_WORK_MASK
108	bne	slow_work_pending
109no_work_pending:
110	asm_trace_hardirqs_on save = 0
111
112	/* perform architecture specific actions before user return */
113	arch_ret_to_user r1, lr
114	ct_user_enter save = 0
115
116	restore_user_regs fast = 0, offset = 0
117ENDPROC(ret_to_user_from_irq)
118ENDPROC(ret_to_user)
119
120/*
121 * This is how we return from a fork.
122 */
123ENTRY(ret_from_fork)
124	bl	schedule_tail
125	cmp	r5, #0
126	movne	r0, r4
127	badrne	lr, 1f
128	retne	r5
1291:	get_thread_info tsk
130	b	ret_slow_syscall
131ENDPROC(ret_from_fork)
132
133/*=============================================================================
134 * SWI handler
135 *-----------------------------------------------------------------------------
136 */
137
138	.align	5
139ENTRY(vector_swi)
140#ifdef CONFIG_CPU_V7M
141	v7m_exception_entry
142#else
143	sub	sp, sp, #PT_REGS_SIZE
144	stmia	sp, {r0 - r12}			@ Calling r0 - r12
145 ARM(	add	r8, sp, #S_PC		)
146 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
147 THUMB(	mov	r8, sp			)
148 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
149	mrs	r8, spsr			@ called from non-FIQ mode, so ok.
150	str	lr, [sp, #S_PC]			@ Save calling PC
151	str	r8, [sp, #S_PSR]		@ Save CPSR
152	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
153#endif
154	zero_fp
155	alignment_trap r10, ip, __cr_alignment
156	enable_irq
157	ct_user_exit
158	get_thread_info tsk
159
160	/*
161	 * Get the system call number.
162	 */
163
164#if defined(CONFIG_OABI_COMPAT)
165
166	/*
167	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
168	 * value to determine if it is an EABI or an old ABI call.
169	 */
170#ifdef CONFIG_ARM_THUMB
171	tst	r8, #PSR_T_BIT
172	movne	r10, #0				@ no thumb OABI emulation
173 USER(	ldreq	r10, [lr, #-4]		)	@ get SWI instruction
174#else
175 USER(	ldr	r10, [lr, #-4]		)	@ get SWI instruction
176#endif
177 ARM_BE8(rev	r10, r10)			@ little endian instruction
178
179#elif defined(CONFIG_AEABI)
180
181	/*
182	 * Pure EABI user space always put syscall number into scno (r7).
183	 */
184#elif defined(CONFIG_ARM_THUMB)
185	/* Legacy ABI only, possibly thumb mode. */
186	tst	r8, #PSR_T_BIT			@ this is SPSR from save_user_regs
187	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
188 USER(	ldreq	scno, [lr, #-4]		)
189
190#else
191	/* Legacy ABI only. */
192 USER(	ldr	scno, [lr, #-4]		)	@ get SWI instruction
193#endif
194
195	uaccess_disable tbl
196
197	adr	tbl, sys_call_table		@ load syscall table pointer
198
199#if defined(CONFIG_OABI_COMPAT)
200	/*
201	 * If the swi argument is zero, this is an EABI call and we do nothing.
202	 *
203	 * If this is an old ABI call, get the syscall number into scno and
204	 * get the old ABI syscall table address.
205	 */
206	bics	r10, r10, #0xff000000
207	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
208	ldrne	tbl, =sys_oabi_call_table
209#elif !defined(CONFIG_AEABI)
210	bic	scno, scno, #0xff000000		@ mask off SWI op-code
211	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
212#endif
213
214local_restart:
215	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
216	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
217
218	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
219	bne	__sys_trace
220
221	cmp	scno, #NR_syscalls		@ check upper syscall limit
222	badr	lr, ret_fast_syscall		@ return address
223	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
224
225	add	r1, sp, #S_OFF
2262:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
227	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
228	bcs	arm_syscall
229	mov	why, #0				@ no longer a real syscall
230	b	sys_ni_syscall			@ not private func
231
232#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
233	/*
234	 * We failed to handle a fault trying to access the page
235	 * containing the swi instruction, but we're not really in a
236	 * position to return -EFAULT. Instead, return back to the
237	 * instruction and re-enter the user fault handling path trying
238	 * to page it in. This will likely result in sending SEGV to the
239	 * current task.
240	 */
2419001:
242	sub	lr, lr, #4
243	str	lr, [sp, #S_PC]
244	b	ret_fast_syscall
245#endif
246ENDPROC(vector_swi)
247
248	/*
249	 * This is the really slow path.  We're going to be doing
250	 * context switches, and waiting for our parent to respond.
251	 */
252__sys_trace:
253	mov	r1, scno
254	add	r0, sp, #S_OFF
255	bl	syscall_trace_enter
256
257	badr	lr, __sys_trace_return		@ return address
258	mov	scno, r0			@ syscall number (possibly new)
259	add	r1, sp, #S_R0 + S_OFF		@ pointer to regs
260	cmp	scno, #NR_syscalls		@ check upper syscall limit
261	ldmccia	r1, {r0 - r6}			@ have to reload r0 - r6
262	stmccia	sp, {r4, r5}			@ and update the stack args
263	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
264	cmp	scno, #-1			@ skip the syscall?
265	bne	2b
266	add	sp, sp, #S_OFF			@ restore stack
267	b	ret_slow_syscall
268
269__sys_trace_return:
270	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
271	mov	r0, sp
272	bl	syscall_trace_exit
273	b	ret_slow_syscall
274
275__sys_trace_return_nosave:
276	enable_irq_notrace
277	mov	r0, sp
278	bl	syscall_trace_exit
279	b	ret_slow_syscall
280
281	.align	5
282#ifdef CONFIG_ALIGNMENT_TRAP
283	.type	__cr_alignment, #object
284__cr_alignment:
285	.word	cr_alignment
286#endif
287	.ltorg
288
289	.macro	syscall_table_start, sym
290	.equ	__sys_nr, 0
291	.type	\sym, #object
292ENTRY(\sym)
293	.endm
294
295	.macro	syscall, nr, func
296	.ifgt	__sys_nr - \nr
297	.error	"Duplicated/unorded system call entry"
298	.endif
299	.rept	\nr - __sys_nr
300	.long	sys_ni_syscall
301	.endr
302	.long	\func
303	.equ	__sys_nr, \nr + 1
304	.endm
305
306	.macro	syscall_table_end, sym
307	.ifgt	__sys_nr - __NR_syscalls
308	.error	"System call table too big"
309	.endif
310	.rept	__NR_syscalls - __sys_nr
311	.long	sys_ni_syscall
312	.endr
313	.size	\sym, . - \sym
314	.endm
315
316#define NATIVE(nr, func) syscall nr, func
317
318/*
319 * This is the syscall table declaration for native ABI syscalls.
320 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
321 */
322	syscall_table_start sys_call_table
323#define COMPAT(nr, native, compat) syscall nr, native
324#ifdef CONFIG_AEABI
325#include <calls-eabi.S>
326#else
327#include <calls-oabi.S>
328#endif
329#undef COMPAT
330	syscall_table_end sys_call_table
331
332/*============================================================================
333 * Special system call wrappers
334 */
335@ r0 = syscall number
336@ r8 = syscall table
337sys_syscall:
338		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
339		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
340		cmpne	scno, #NR_syscalls	@ check range
341		stmloia	sp, {r5, r6}		@ shuffle args
342		movlo	r0, r1
343		movlo	r1, r2
344		movlo	r2, r3
345		movlo	r3, r4
346		ldrlo	pc, [tbl, scno, lsl #2]
347		b	sys_ni_syscall
348ENDPROC(sys_syscall)
349
350sys_sigreturn_wrapper:
351		add	r0, sp, #S_OFF
352		mov	why, #0		@ prevent syscall restart handling
353		b	sys_sigreturn
354ENDPROC(sys_sigreturn_wrapper)
355
356sys_rt_sigreturn_wrapper:
357		add	r0, sp, #S_OFF
358		mov	why, #0		@ prevent syscall restart handling
359		b	sys_rt_sigreturn
360ENDPROC(sys_rt_sigreturn_wrapper)
361
362sys_statfs64_wrapper:
363		teq	r1, #88
364		moveq	r1, #84
365		b	sys_statfs64
366ENDPROC(sys_statfs64_wrapper)
367
368sys_fstatfs64_wrapper:
369		teq	r1, #88
370		moveq	r1, #84
371		b	sys_fstatfs64
372ENDPROC(sys_fstatfs64_wrapper)
373
374/*
375 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
376 * offset, we return EINVAL.
377 */
378sys_mmap2:
379#if PAGE_SHIFT > 12
380		tst	r5, #PGOFF_MASK
381		moveq	r5, r5, lsr #PAGE_SHIFT - 12
382		streq	r5, [sp, #4]
383		beq	sys_mmap_pgoff
384		mov	r0, #-EINVAL
385		ret	lr
386#else
387		str	r5, [sp, #4]
388		b	sys_mmap_pgoff
389#endif
390ENDPROC(sys_mmap2)
391
392#ifdef CONFIG_OABI_COMPAT
393
394/*
395 * These are syscalls with argument register differences
396 */
397
398sys_oabi_pread64:
399		stmia	sp, {r3, r4}
400		b	sys_pread64
401ENDPROC(sys_oabi_pread64)
402
403sys_oabi_pwrite64:
404		stmia	sp, {r3, r4}
405		b	sys_pwrite64
406ENDPROC(sys_oabi_pwrite64)
407
408sys_oabi_truncate64:
409		mov	r3, r2
410		mov	r2, r1
411		b	sys_truncate64
412ENDPROC(sys_oabi_truncate64)
413
414sys_oabi_ftruncate64:
415		mov	r3, r2
416		mov	r2, r1
417		b	sys_ftruncate64
418ENDPROC(sys_oabi_ftruncate64)
419
420sys_oabi_readahead:
421		str	r3, [sp]
422		mov	r3, r2
423		mov	r2, r1
424		b	sys_readahead
425ENDPROC(sys_oabi_readahead)
426
427/*
428 * Let's declare a second syscall table for old ABI binaries
429 * using the compatibility syscall entries.
430 */
431	syscall_table_start sys_oabi_call_table
432#define COMPAT(nr, native, compat) syscall nr, compat
433#include <calls-oabi.S>
434	syscall_table_end sys_oabi_call_table
435
436#endif
437
438