xref: /openbmc/linux/arch/arm/kernel/entry-common.S (revision 6b5fc336) 
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 | _TIF_WORK_MASK
45	bne	fast_work_pending
46
47	/* perform architecture specific actions before user return */
48	arch_ret_to_user r1, lr
49
50	restore_user_regs fast = 1, offset = S_OFF
51 UNWIND(.fnend		)
52ENDPROC(ret_fast_syscall)
53
54	/* Ok, we need to do extra processing, enter the slow path. */
55fast_work_pending:
56	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
57	/* fall through to work_pending */
58#else
59/*
60 * The "replacement" ret_fast_syscall for when tracing or context tracking
61 * is enabled.  As we will need to call out to some C functions, we save
62 * r0 first to avoid needing to save registers around each C function call.
63 */
64ret_fast_syscall:
65 UNWIND(.fnstart	)
66 UNWIND(.cantunwind	)
67	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
68	disable_irq_notrace			@ disable interrupts
69	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
70	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
71	beq	no_work_pending
72 UNWIND(.fnend		)
73ENDPROC(ret_fast_syscall)
74
75	/* Slower path - fall through to work_pending */
76#endif
77
78	tst	r1, #_TIF_SYSCALL_WORK
79	bne	__sys_trace_return_nosave
80slow_work_pending:
81	mov	r0, sp				@ 'regs'
82	mov	r2, why				@ 'syscall'
83	bl	do_work_pending
84	cmp	r0, #0
85	beq	no_work_pending
86	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
87	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
88	b	local_restart			@ ... and off we go
89ENDPROC(ret_fast_syscall)
90
91/*
92 * "slow" syscall return path.  "why" tells us if this was a real syscall.
93 * IRQs may be enabled here, so always disable them.  Note that we use the
94 * "notrace" version to avoid calling into the tracing code unnecessarily.
95 * do_work_pending() will update this state if necessary.
96 */
97ENTRY(ret_to_user)
98ret_slow_syscall:
99	disable_irq_notrace			@ disable interrupts
100ENTRY(ret_to_user_from_irq)
101	ldr	r1, [tsk, #TI_FLAGS]
102	tst	r1, #_TIF_WORK_MASK
103	bne	slow_work_pending
104no_work_pending:
105	asm_trace_hardirqs_on save = 0
106
107	/* perform architecture specific actions before user return */
108	arch_ret_to_user r1, lr
109	ct_user_enter save = 0
110
111	restore_user_regs fast = 0, offset = 0
112ENDPROC(ret_to_user_from_irq)
113ENDPROC(ret_to_user)
114
115/*
116 * This is how we return from a fork.
117 */
118ENTRY(ret_from_fork)
119	bl	schedule_tail
120	cmp	r5, #0
121	movne	r0, r4
122	badrne	lr, 1f
123	retne	r5
1241:	get_thread_info tsk
125	b	ret_slow_syscall
126ENDPROC(ret_from_fork)
127
128/*=============================================================================
129 * SWI handler
130 *-----------------------------------------------------------------------------
131 */
132
133	.align	5
134ENTRY(vector_swi)
135#ifdef CONFIG_CPU_V7M
136	v7m_exception_entry
137#else
138	sub	sp, sp, #PT_REGS_SIZE
139	stmia	sp, {r0 - r12}			@ Calling r0 - r12
140 ARM(	add	r8, sp, #S_PC		)
141 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
142 THUMB(	mov	r8, sp			)
143 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
144	mrs	r8, spsr			@ called from non-FIQ mode, so ok.
145	str	lr, [sp, #S_PC]			@ Save calling PC
146	str	r8, [sp, #S_PSR]		@ Save CPSR
147	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
148#endif
149	zero_fp
150	alignment_trap r10, ip, __cr_alignment
151	enable_irq
152	ct_user_exit
153	get_thread_info tsk
154
155	/*
156	 * Get the system call number.
157	 */
158
159#if defined(CONFIG_OABI_COMPAT)
160
161	/*
162	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
163	 * value to determine if it is an EABI or an old ABI call.
164	 */
165#ifdef CONFIG_ARM_THUMB
166	tst	r8, #PSR_T_BIT
167	movne	r10, #0				@ no thumb OABI emulation
168 USER(	ldreq	r10, [lr, #-4]		)	@ get SWI instruction
169#else
170 USER(	ldr	r10, [lr, #-4]		)	@ get SWI instruction
171#endif
172 ARM_BE8(rev	r10, r10)			@ little endian instruction
173
174#elif defined(CONFIG_AEABI)
175
176	/*
177	 * Pure EABI user space always put syscall number into scno (r7).
178	 */
179#elif defined(CONFIG_ARM_THUMB)
180	/* Legacy ABI only, possibly thumb mode. */
181	tst	r8, #PSR_T_BIT			@ this is SPSR from save_user_regs
182	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
183 USER(	ldreq	scno, [lr, #-4]		)
184
185#else
186	/* Legacy ABI only. */
187 USER(	ldr	scno, [lr, #-4]		)	@ get SWI instruction
188#endif
189
190	uaccess_disable tbl
191
192	adr	tbl, sys_call_table		@ load syscall table pointer
193
194#if defined(CONFIG_OABI_COMPAT)
195	/*
196	 * If the swi argument is zero, this is an EABI call and we do nothing.
197	 *
198	 * If this is an old ABI call, get the syscall number into scno and
199	 * get the old ABI syscall table address.
200	 */
201	bics	r10, r10, #0xff000000
202	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
203	ldrne	tbl, =sys_oabi_call_table
204#elif !defined(CONFIG_AEABI)
205	bic	scno, scno, #0xff000000		@ mask off SWI op-code
206	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
207#endif
208
209local_restart:
210	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
211	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
212
213	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
214	bne	__sys_trace
215
216	cmp	scno, #NR_syscalls		@ check upper syscall limit
217	badr	lr, ret_fast_syscall		@ return address
218	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
219
220	add	r1, sp, #S_OFF
2212:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
222	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
223	bcs	arm_syscall
224	mov	why, #0				@ no longer a real syscall
225	b	sys_ni_syscall			@ not private func
226
227#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
228	/*
229	 * We failed to handle a fault trying to access the page
230	 * containing the swi instruction, but we're not really in a
231	 * position to return -EFAULT. Instead, return back to the
232	 * instruction and re-enter the user fault handling path trying
233	 * to page it in. This will likely result in sending SEGV to the
234	 * current task.
235	 */
2369001:
237	sub	lr, lr, #4
238	str	lr, [sp, #S_PC]
239	b	ret_fast_syscall
240#endif
241ENDPROC(vector_swi)
242
243	/*
244	 * This is the really slow path.  We're going to be doing
245	 * context switches, and waiting for our parent to respond.
246	 */
247__sys_trace:
248	mov	r1, scno
249	add	r0, sp, #S_OFF
250	bl	syscall_trace_enter
251
252	badr	lr, __sys_trace_return		@ return address
253	mov	scno, r0			@ syscall number (possibly new)
254	add	r1, sp, #S_R0 + S_OFF		@ pointer to regs
255	cmp	scno, #NR_syscalls		@ check upper syscall limit
256	ldmccia	r1, {r0 - r6}			@ have to reload r0 - r6
257	stmccia	sp, {r4, r5}			@ and update the stack args
258	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
259	cmp	scno, #-1			@ skip the syscall?
260	bne	2b
261	add	sp, sp, #S_OFF			@ restore stack
262	b	ret_slow_syscall
263
264__sys_trace_return:
265	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
266	mov	r0, sp
267	bl	syscall_trace_exit
268	b	ret_slow_syscall
269
270__sys_trace_return_nosave:
271	enable_irq_notrace
272	mov	r0, sp
273	bl	syscall_trace_exit
274	b	ret_slow_syscall
275
276	.align	5
277#ifdef CONFIG_ALIGNMENT_TRAP
278	.type	__cr_alignment, #object
279__cr_alignment:
280	.word	cr_alignment
281#endif
282	.ltorg
283
284	.macro	syscall_table_start, sym
285	.equ	__sys_nr, 0
286	.type	\sym, #object
287ENTRY(\sym)
288	.endm
289
290	.macro	syscall, nr, func
291	.ifgt	__sys_nr - \nr
292	.error	"Duplicated/unorded system call entry"
293	.endif
294	.rept	\nr - __sys_nr
295	.long	sys_ni_syscall
296	.endr
297	.long	\func
298	.equ	__sys_nr, \nr + 1
299	.endm
300
301	.macro	syscall_table_end, sym
302	.ifgt	__sys_nr - __NR_syscalls
303	.error	"System call table too big"
304	.endif
305	.rept	__NR_syscalls - __sys_nr
306	.long	sys_ni_syscall
307	.endr
308	.size	\sym, . - \sym
309	.endm
310
311#define NATIVE(nr, func) syscall nr, func
312
313/*
314 * This is the syscall table declaration for native ABI syscalls.
315 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
316 */
317	syscall_table_start sys_call_table
318#define COMPAT(nr, native, compat) syscall nr, native
319#ifdef CONFIG_AEABI
320#include <calls-eabi.S>
321#else
322#include <calls-oabi.S>
323#endif
324#undef COMPAT
325	syscall_table_end sys_call_table
326
327/*============================================================================
328 * Special system call wrappers
329 */
330@ r0 = syscall number
331@ r8 = syscall table
332sys_syscall:
333		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
334		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
335		cmpne	scno, #NR_syscalls	@ check range
336		stmloia	sp, {r5, r6}		@ shuffle args
337		movlo	r0, r1
338		movlo	r1, r2
339		movlo	r2, r3
340		movlo	r3, r4
341		ldrlo	pc, [tbl, scno, lsl #2]
342		b	sys_ni_syscall
343ENDPROC(sys_syscall)
344
345sys_sigreturn_wrapper:
346		add	r0, sp, #S_OFF
347		mov	why, #0		@ prevent syscall restart handling
348		b	sys_sigreturn
349ENDPROC(sys_sigreturn_wrapper)
350
351sys_rt_sigreturn_wrapper:
352		add	r0, sp, #S_OFF
353		mov	why, #0		@ prevent syscall restart handling
354		b	sys_rt_sigreturn
355ENDPROC(sys_rt_sigreturn_wrapper)
356
357sys_statfs64_wrapper:
358		teq	r1, #88
359		moveq	r1, #84
360		b	sys_statfs64
361ENDPROC(sys_statfs64_wrapper)
362
363sys_fstatfs64_wrapper:
364		teq	r1, #88
365		moveq	r1, #84
366		b	sys_fstatfs64
367ENDPROC(sys_fstatfs64_wrapper)
368
369/*
370 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
371 * offset, we return EINVAL.
372 */
373sys_mmap2:
374#if PAGE_SHIFT > 12
375		tst	r5, #PGOFF_MASK
376		moveq	r5, r5, lsr #PAGE_SHIFT - 12
377		streq	r5, [sp, #4]
378		beq	sys_mmap_pgoff
379		mov	r0, #-EINVAL
380		ret	lr
381#else
382		str	r5, [sp, #4]
383		b	sys_mmap_pgoff
384#endif
385ENDPROC(sys_mmap2)
386
387#ifdef CONFIG_OABI_COMPAT
388
389/*
390 * These are syscalls with argument register differences
391 */
392
393sys_oabi_pread64:
394		stmia	sp, {r3, r4}
395		b	sys_pread64
396ENDPROC(sys_oabi_pread64)
397
398sys_oabi_pwrite64:
399		stmia	sp, {r3, r4}
400		b	sys_pwrite64
401ENDPROC(sys_oabi_pwrite64)
402
403sys_oabi_truncate64:
404		mov	r3, r2
405		mov	r2, r1
406		b	sys_truncate64
407ENDPROC(sys_oabi_truncate64)
408
409sys_oabi_ftruncate64:
410		mov	r3, r2
411		mov	r2, r1
412		b	sys_ftruncate64
413ENDPROC(sys_oabi_ftruncate64)
414
415sys_oabi_readahead:
416		str	r3, [sp]
417		mov	r3, r2
418		mov	r2, r1
419		b	sys_readahead
420ENDPROC(sys_oabi_readahead)
421
422/*
423 * Let's declare a second syscall table for old ABI binaries
424 * using the compatibility syscall entries.
425 */
426	syscall_table_start sys_oabi_call_table
427#define COMPAT(nr, native, compat) syscall nr, compat
428#include <calls-oabi.S>
429	syscall_table_end sys_oabi_call_table
430
431#endif
432
433