xref: /openbmc/linux/arch/arm/kernel/entry-common.S (revision b96fc2f3) 
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#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING))
28/*
29 * This is the fast syscall return path.  We do as little as possible here,
30 * such as avoiding writing r0 to the stack.  We only use this path if we
31 * have tracing and context tracking disabled - the overheads from those
32 * features make this path too inefficient.
33 */
34ret_fast_syscall:
35 UNWIND(.fnstart	)
36 UNWIND(.cantunwind	)
37	disable_irq_notrace			@ disable interrupts
38	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
39	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
40	bne	fast_work_pending
41
42	/* perform architecture specific actions before user return */
43	arch_ret_to_user r1, lr
44
45	restore_user_regs fast = 1, offset = S_OFF
46 UNWIND(.fnend		)
47ENDPROC(ret_fast_syscall)
48
49	/* Ok, we need to do extra processing, enter the slow path. */
50fast_work_pending:
51	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
52	/* fall through to work_pending */
53#else
54/*
55 * The "replacement" ret_fast_syscall for when tracing or context tracking
56 * is enabled.  As we will need to call out to some C functions, we save
57 * r0 first to avoid needing to save registers around each C function call.
58 */
59ret_fast_syscall:
60 UNWIND(.fnstart	)
61 UNWIND(.cantunwind	)
62	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
63	disable_irq_notrace			@ disable interrupts
64	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
65	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
66	beq	no_work_pending
67 UNWIND(.fnend		)
68ENDPROC(ret_fast_syscall)
69
70	/* Slower path - fall through to work_pending */
71#endif
72
73	tst	r1, #_TIF_SYSCALL_WORK
74	bne	__sys_trace_return_nosave
75slow_work_pending:
76	mov	r0, sp				@ 'regs'
77	mov	r2, why				@ 'syscall'
78	bl	do_work_pending
79	cmp	r0, #0
80	beq	no_work_pending
81	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
82	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
83	b	local_restart			@ ... and off we go
84ENDPROC(ret_fast_syscall)
85
86/*
87 * "slow" syscall return path.  "why" tells us if this was a real syscall.
88 * IRQs may be enabled here, so always disable them.  Note that we use the
89 * "notrace" version to avoid calling into the tracing code unnecessarily.
90 * do_work_pending() will update this state if necessary.
91 */
92ENTRY(ret_to_user)
93ret_slow_syscall:
94	disable_irq_notrace			@ disable interrupts
95ENTRY(ret_to_user_from_irq)
96	ldr	r1, [tsk, #TI_FLAGS]
97	tst	r1, #_TIF_WORK_MASK
98	bne	slow_work_pending
99no_work_pending:
100	asm_trace_hardirqs_on save = 0
101
102	/* perform architecture specific actions before user return */
103	arch_ret_to_user r1, lr
104	ct_user_enter save = 0
105
106	restore_user_regs fast = 0, offset = 0
107ENDPROC(ret_to_user_from_irq)
108ENDPROC(ret_to_user)
109
110/*
111 * This is how we return from a fork.
112 */
113ENTRY(ret_from_fork)
114	bl	schedule_tail
115	cmp	r5, #0
116	movne	r0, r4
117	badrne	lr, 1f
118	retne	r5
1191:	get_thread_info tsk
120	b	ret_slow_syscall
121ENDPROC(ret_from_fork)
122
123	.equ NR_syscalls,0
124#define CALL(x) .equ NR_syscalls,NR_syscalls+1
125#include "calls.S"
126
127/*
128 * Ensure that the system call table is equal to __NR_syscalls,
129 * which is the value the rest of the system sees
130 */
131.ifne NR_syscalls - __NR_syscalls
132.error "__NR_syscalls is not equal to the size of the syscall table"
133.endif
134
135#undef CALL
136#define CALL(x) .long x
137
138/*=============================================================================
139 * SWI handler
140 *-----------------------------------------------------------------------------
141 */
142
143	.align	5
144ENTRY(vector_swi)
145#ifdef CONFIG_CPU_V7M
146	v7m_exception_entry
147#else
148	sub	sp, sp, #S_FRAME_SIZE
149	stmia	sp, {r0 - r12}			@ Calling r0 - r12
150 ARM(	add	r8, sp, #S_PC		)
151 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
152 THUMB(	mov	r8, sp			)
153 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
154	mrs	r8, spsr			@ called from non-FIQ mode, so ok.
155	str	lr, [sp, #S_PC]			@ Save calling PC
156	str	r8, [sp, #S_PSR]		@ Save CPSR
157	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
158#endif
159	zero_fp
160	alignment_trap r10, ip, __cr_alignment
161	enable_irq
162	ct_user_exit
163	get_thread_info tsk
164
165	/*
166	 * Get the system call number.
167	 */
168
169#if defined(CONFIG_OABI_COMPAT)
170
171	/*
172	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
173	 * value to determine if it is an EABI or an old ABI call.
174	 */
175#ifdef CONFIG_ARM_THUMB
176	tst	r8, #PSR_T_BIT
177	movne	r10, #0				@ no thumb OABI emulation
178 USER(	ldreq	r10, [lr, #-4]		)	@ get SWI instruction
179#else
180 USER(	ldr	r10, [lr, #-4]		)	@ get SWI instruction
181#endif
182 ARM_BE8(rev	r10, r10)			@ little endian instruction
183
184#elif defined(CONFIG_AEABI)
185
186	/*
187	 * Pure EABI user space always put syscall number into scno (r7).
188	 */
189#elif defined(CONFIG_ARM_THUMB)
190	/* Legacy ABI only, possibly thumb mode. */
191	tst	r8, #PSR_T_BIT			@ this is SPSR from save_user_regs
192	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
193 USER(	ldreq	scno, [lr, #-4]		)
194
195#else
196	/* Legacy ABI only. */
197 USER(	ldr	scno, [lr, #-4]		)	@ get SWI instruction
198#endif
199
200	uaccess_disable tbl
201
202	adr	tbl, sys_call_table		@ load syscall table pointer
203
204#if defined(CONFIG_OABI_COMPAT)
205	/*
206	 * If the swi argument is zero, this is an EABI call and we do nothing.
207	 *
208	 * If this is an old ABI call, get the syscall number into scno and
209	 * get the old ABI syscall table address.
210	 */
211	bics	r10, r10, #0xff000000
212	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
213	ldrne	tbl, =sys_oabi_call_table
214#elif !defined(CONFIG_AEABI)
215	bic	scno, scno, #0xff000000		@ mask off SWI op-code
216	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
217#endif
218
219local_restart:
220	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
221	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
222
223	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
224	bne	__sys_trace
225
226	cmp	scno, #NR_syscalls		@ check upper syscall limit
227	badr	lr, ret_fast_syscall		@ return address
228	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
229
230	add	r1, sp, #S_OFF
2312:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
232	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
233	bcs	arm_syscall
234	mov	why, #0				@ no longer a real syscall
235	b	sys_ni_syscall			@ not private func
236
237#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
238	/*
239	 * We failed to handle a fault trying to access the page
240	 * containing the swi instruction, but we're not really in a
241	 * position to return -EFAULT. Instead, return back to the
242	 * instruction and re-enter the user fault handling path trying
243	 * to page it in. This will likely result in sending SEGV to the
244	 * current task.
245	 */
2469001:
247	sub	lr, lr, #4
248	str	lr, [sp, #S_PC]
249	b	ret_fast_syscall
250#endif
251ENDPROC(vector_swi)
252
253	/*
254	 * This is the really slow path.  We're going to be doing
255	 * context switches, and waiting for our parent to respond.
256	 */
257__sys_trace:
258	mov	r1, scno
259	add	r0, sp, #S_OFF
260	bl	syscall_trace_enter
261
262	badr	lr, __sys_trace_return		@ return address
263	mov	scno, r0			@ syscall number (possibly new)
264	add	r1, sp, #S_R0 + S_OFF		@ pointer to regs
265	cmp	scno, #NR_syscalls		@ check upper syscall limit
266	ldmccia	r1, {r0 - r6}			@ have to reload r0 - r6
267	stmccia	sp, {r4, r5}			@ and update the stack args
268	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
269	cmp	scno, #-1			@ skip the syscall?
270	bne	2b
271	add	sp, sp, #S_OFF			@ restore stack
272	b	ret_slow_syscall
273
274__sys_trace_return:
275	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
276	mov	r0, sp
277	bl	syscall_trace_exit
278	b	ret_slow_syscall
279
280__sys_trace_return_nosave:
281	enable_irq_notrace
282	mov	r0, sp
283	bl	syscall_trace_exit
284	b	ret_slow_syscall
285
286	.align	5
287#ifdef CONFIG_ALIGNMENT_TRAP
288	.type	__cr_alignment, #object
289__cr_alignment:
290	.word	cr_alignment
291#endif
292	.ltorg
293
294/*
295 * This is the syscall table declaration for native ABI syscalls.
296 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
297 */
298#define ABI(native, compat) native
299#ifdef CONFIG_AEABI
300#define OBSOLETE(syscall) sys_ni_syscall
301#else
302#define OBSOLETE(syscall) syscall
303#endif
304
305	.type	sys_call_table, #object
306ENTRY(sys_call_table)
307#include "calls.S"
308#undef ABI
309#undef OBSOLETE
310
311/*============================================================================
312 * Special system call wrappers
313 */
314@ r0 = syscall number
315@ r8 = syscall table
316sys_syscall:
317		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
318		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
319		cmpne	scno, #NR_syscalls	@ check range
320		stmloia	sp, {r5, r6}		@ shuffle args
321		movlo	r0, r1
322		movlo	r1, r2
323		movlo	r2, r3
324		movlo	r3, r4
325		ldrlo	pc, [tbl, scno, lsl #2]
326		b	sys_ni_syscall
327ENDPROC(sys_syscall)
328
329sys_sigreturn_wrapper:
330		add	r0, sp, #S_OFF
331		mov	why, #0		@ prevent syscall restart handling
332		b	sys_sigreturn
333ENDPROC(sys_sigreturn_wrapper)
334
335sys_rt_sigreturn_wrapper:
336		add	r0, sp, #S_OFF
337		mov	why, #0		@ prevent syscall restart handling
338		b	sys_rt_sigreturn
339ENDPROC(sys_rt_sigreturn_wrapper)
340
341sys_statfs64_wrapper:
342		teq	r1, #88
343		moveq	r1, #84
344		b	sys_statfs64
345ENDPROC(sys_statfs64_wrapper)
346
347sys_fstatfs64_wrapper:
348		teq	r1, #88
349		moveq	r1, #84
350		b	sys_fstatfs64
351ENDPROC(sys_fstatfs64_wrapper)
352
353/*
354 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
355 * offset, we return EINVAL.
356 */
357sys_mmap2:
358#if PAGE_SHIFT > 12
359		tst	r5, #PGOFF_MASK
360		moveq	r5, r5, lsr #PAGE_SHIFT - 12
361		streq	r5, [sp, #4]
362		beq	sys_mmap_pgoff
363		mov	r0, #-EINVAL
364		ret	lr
365#else
366		str	r5, [sp, #4]
367		b	sys_mmap_pgoff
368#endif
369ENDPROC(sys_mmap2)
370
371#ifdef CONFIG_OABI_COMPAT
372
373/*
374 * These are syscalls with argument register differences
375 */
376
377sys_oabi_pread64:
378		stmia	sp, {r3, r4}
379		b	sys_pread64
380ENDPROC(sys_oabi_pread64)
381
382sys_oabi_pwrite64:
383		stmia	sp, {r3, r4}
384		b	sys_pwrite64
385ENDPROC(sys_oabi_pwrite64)
386
387sys_oabi_truncate64:
388		mov	r3, r2
389		mov	r2, r1
390		b	sys_truncate64
391ENDPROC(sys_oabi_truncate64)
392
393sys_oabi_ftruncate64:
394		mov	r3, r2
395		mov	r2, r1
396		b	sys_ftruncate64
397ENDPROC(sys_oabi_ftruncate64)
398
399sys_oabi_readahead:
400		str	r3, [sp]
401		mov	r3, r2
402		mov	r2, r1
403		b	sys_readahead
404ENDPROC(sys_oabi_readahead)
405
406/*
407 * Let's declare a second syscall table for old ABI binaries
408 * using the compatibility syscall entries.
409 */
410#define ABI(native, compat) compat
411#define OBSOLETE(syscall) syscall
412
413	.type	sys_oabi_call_table, #object
414ENTRY(sys_oabi_call_table)
415#include "calls.S"
416#undef ABI
417#undef OBSOLETE
418
419#endif
420
421