xref: /openbmc/linux/arch/arm/kernel/entry-common.S (revision ba61bb17) 
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#include <asm/memory.h>
16#ifdef CONFIG_AEABI
17#include <asm/unistd-oabi.h>
18#endif
19
20	.equ	NR_syscalls, __NR_syscalls
21
22#ifdef CONFIG_NEED_RET_TO_USER
23#include <mach/entry-macro.S>
24#else
25	.macro  arch_ret_to_user, tmp1, tmp2
26	.endm
27#endif
28
29#include "entry-header.S"
30
31saved_psr	.req	r8
32#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING)
33saved_pc	.req	r9
34#define TRACE(x...) x
35#else
36saved_pc	.req	lr
37#define TRACE(x...)
38#endif
39
40	.section .entry.text,"ax",%progbits
41	.align	5
42#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING) || \
43	IS_ENABLED(CONFIG_DEBUG_RSEQ))
44/*
45 * This is the fast syscall return path.  We do as little as possible here,
46 * such as avoiding writing r0 to the stack.  We only use this path if we
47 * have tracing, context tracking and rseq debug disabled - the overheads
48 * from those features make this path too inefficient.
49 */
50ret_fast_syscall:
51 UNWIND(.fnstart	)
52 UNWIND(.cantunwind	)
53	disable_irq_notrace			@ disable interrupts
54	ldr	r2, [tsk, #TI_ADDR_LIMIT]
55	cmp	r2, #TASK_SIZE
56	blne	addr_limit_check_failed
57	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
58	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
59	bne	fast_work_pending
60
61
62	/* perform architecture specific actions before user return */
63	arch_ret_to_user r1, lr
64
65	restore_user_regs fast = 1, offset = S_OFF
66 UNWIND(.fnend		)
67ENDPROC(ret_fast_syscall)
68
69	/* Ok, we need to do extra processing, enter the slow path. */
70fast_work_pending:
71	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
72	/* fall through to work_pending */
73#else
74/*
75 * The "replacement" ret_fast_syscall for when tracing, context tracking,
76 * or rseq debug is enabled.  As we will need to call out to some C functions,
77 * we save r0 first to avoid needing to save registers around each C function
78 * call.
79 */
80ret_fast_syscall:
81 UNWIND(.fnstart	)
82 UNWIND(.cantunwind	)
83	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
84#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
85	/* do_rseq_syscall needs interrupts enabled. */
86	mov	r0, sp				@ 'regs'
87	bl	do_rseq_syscall
88#endif
89	disable_irq_notrace			@ disable interrupts
90	ldr	r2, [tsk, #TI_ADDR_LIMIT]
91	cmp	r2, #TASK_SIZE
92	blne	addr_limit_check_failed
93	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
94	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK
95	beq	no_work_pending
96 UNWIND(.fnend		)
97ENDPROC(ret_fast_syscall)
98
99	/* Slower path - fall through to work_pending */
100#endif
101
102	tst	r1, #_TIF_SYSCALL_WORK
103	bne	__sys_trace_return_nosave
104slow_work_pending:
105	mov	r0, sp				@ 'regs'
106	mov	r2, why				@ 'syscall'
107	bl	do_work_pending
108	cmp	r0, #0
109	beq	no_work_pending
110	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
111	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
112	b	local_restart			@ ... and off we go
113ENDPROC(ret_fast_syscall)
114
115/*
116 * "slow" syscall return path.  "why" tells us if this was a real syscall.
117 * IRQs may be enabled here, so always disable them.  Note that we use the
118 * "notrace" version to avoid calling into the tracing code unnecessarily.
119 * do_work_pending() will update this state if necessary.
120 */
121ENTRY(ret_to_user)
122ret_slow_syscall:
123#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
124	/* do_rseq_syscall needs interrupts enabled. */
125	enable_irq_notrace			@ enable interrupts
126	mov	r0, sp				@ 'regs'
127	bl	do_rseq_syscall
128#endif
129	disable_irq_notrace			@ disable interrupts
130ENTRY(ret_to_user_from_irq)
131	ldr	r2, [tsk, #TI_ADDR_LIMIT]
132	cmp	r2, #TASK_SIZE
133	blne	addr_limit_check_failed
134	ldr	r1, [tsk, #TI_FLAGS]
135	tst	r1, #_TIF_WORK_MASK
136	bne	slow_work_pending
137no_work_pending:
138	asm_trace_hardirqs_on save = 0
139
140	/* perform architecture specific actions before user return */
141	arch_ret_to_user r1, lr
142	ct_user_enter save = 0
143
144	restore_user_regs fast = 0, offset = 0
145ENDPROC(ret_to_user_from_irq)
146ENDPROC(ret_to_user)
147
148/*
149 * This is how we return from a fork.
150 */
151ENTRY(ret_from_fork)
152	bl	schedule_tail
153	cmp	r5, #0
154	movne	r0, r4
155	badrne	lr, 1f
156	retne	r5
1571:	get_thread_info tsk
158	b	ret_slow_syscall
159ENDPROC(ret_from_fork)
160
161/*=============================================================================
162 * SWI handler
163 *-----------------------------------------------------------------------------
164 */
165
166	.align	5
167ENTRY(vector_swi)
168#ifdef CONFIG_CPU_V7M
169	v7m_exception_entry
170#else
171	sub	sp, sp, #PT_REGS_SIZE
172	stmia	sp, {r0 - r12}			@ Calling r0 - r12
173 ARM(	add	r8, sp, #S_PC		)
174 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
175 THUMB(	mov	r8, sp			)
176 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
177	mrs	saved_psr, spsr			@ called from non-FIQ mode, so ok.
178 TRACE(	mov	saved_pc, lr		)
179	str	saved_pc, [sp, #S_PC]		@ Save calling PC
180	str	saved_psr, [sp, #S_PSR]		@ Save CPSR
181	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
182#endif
183	zero_fp
184	alignment_trap r10, ip, __cr_alignment
185	asm_trace_hardirqs_on save=0
186	enable_irq_notrace
187	ct_user_exit save=0
188
189	/*
190	 * Get the system call number.
191	 */
192
193#if defined(CONFIG_OABI_COMPAT)
194
195	/*
196	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
197	 * value to determine if it is an EABI or an old ABI call.
198	 */
199#ifdef CONFIG_ARM_THUMB
200	tst	saved_psr, #PSR_T_BIT
201	movne	r10, #0				@ no thumb OABI emulation
202 USER(	ldreq	r10, [saved_pc, #-4]	)	@ get SWI instruction
203#else
204 USER(	ldr	r10, [saved_pc, #-4]	)	@ get SWI instruction
205#endif
206 ARM_BE8(rev	r10, r10)			@ little endian instruction
207
208#elif defined(CONFIG_AEABI)
209
210	/*
211	 * Pure EABI user space always put syscall number into scno (r7).
212	 */
213#elif defined(CONFIG_ARM_THUMB)
214	/* Legacy ABI only, possibly thumb mode. */
215	tst	saved_psr, #PSR_T_BIT		@ this is SPSR from save_user_regs
216	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
217 USER(	ldreq	scno, [saved_pc, #-4]	)
218
219#else
220	/* Legacy ABI only. */
221 USER(	ldr	scno, [saved_pc, #-4]	)	@ get SWI instruction
222#endif
223
224	/* saved_psr and saved_pc are now dead */
225
226	uaccess_disable tbl
227
228	adr	tbl, sys_call_table		@ load syscall table pointer
229
230#if defined(CONFIG_OABI_COMPAT)
231	/*
232	 * If the swi argument is zero, this is an EABI call and we do nothing.
233	 *
234	 * If this is an old ABI call, get the syscall number into scno and
235	 * get the old ABI syscall table address.
236	 */
237	bics	r10, r10, #0xff000000
238	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
239	ldrne	tbl, =sys_oabi_call_table
240#elif !defined(CONFIG_AEABI)
241	bic	scno, scno, #0xff000000		@ mask off SWI op-code
242	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
243#endif
244	get_thread_info tsk
245	/*
246	 * Reload the registers that may have been corrupted on entry to
247	 * the syscall assembly (by tracing or context tracking.)
248	 */
249 TRACE(	ldmia	sp, {r0 - r3}		)
250
251local_restart:
252	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
253	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
254
255	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
256	bne	__sys_trace
257
258	invoke_syscall tbl, scno, r10, ret_fast_syscall
259
260	add	r1, sp, #S_OFF
2612:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
262	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
263	bcs	arm_syscall
264	mov	why, #0				@ no longer a real syscall
265	b	sys_ni_syscall			@ not private func
266
267#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
268	/*
269	 * We failed to handle a fault trying to access the page
270	 * containing the swi instruction, but we're not really in a
271	 * position to return -EFAULT. Instead, return back to the
272	 * instruction and re-enter the user fault handling path trying
273	 * to page it in. This will likely result in sending SEGV to the
274	 * current task.
275	 */
2769001:
277	sub	lr, saved_pc, #4
278	str	lr, [sp, #S_PC]
279	get_thread_info tsk
280	b	ret_fast_syscall
281#endif
282ENDPROC(vector_swi)
283
284	/*
285	 * This is the really slow path.  We're going to be doing
286	 * context switches, and waiting for our parent to respond.
287	 */
288__sys_trace:
289	mov	r1, scno
290	add	r0, sp, #S_OFF
291	bl	syscall_trace_enter
292	mov	scno, r0
293	invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
294	cmp	scno, #-1			@ skip the syscall?
295	bne	2b
296	add	sp, sp, #S_OFF			@ restore stack
297	b	ret_slow_syscall
298
299__sys_trace_return:
300	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
301	mov	r0, sp
302	bl	syscall_trace_exit
303	b	ret_slow_syscall
304
305__sys_trace_return_nosave:
306	enable_irq_notrace
307	mov	r0, sp
308	bl	syscall_trace_exit
309	b	ret_slow_syscall
310
311	.align	5
312#ifdef CONFIG_ALIGNMENT_TRAP
313	.type	__cr_alignment, #object
314__cr_alignment:
315	.word	cr_alignment
316#endif
317	.ltorg
318
319	.macro	syscall_table_start, sym
320	.equ	__sys_nr, 0
321	.type	\sym, #object
322ENTRY(\sym)
323	.endm
324
325	.macro	syscall, nr, func
326	.ifgt	__sys_nr - \nr
327	.error	"Duplicated/unorded system call entry"
328	.endif
329	.rept	\nr - __sys_nr
330	.long	sys_ni_syscall
331	.endr
332	.long	\func
333	.equ	__sys_nr, \nr + 1
334	.endm
335
336	.macro	syscall_table_end, sym
337	.ifgt	__sys_nr - __NR_syscalls
338	.error	"System call table too big"
339	.endif
340	.rept	__NR_syscalls - __sys_nr
341	.long	sys_ni_syscall
342	.endr
343	.size	\sym, . - \sym
344	.endm
345
346#define NATIVE(nr, func) syscall nr, func
347
348/*
349 * This is the syscall table declaration for native ABI syscalls.
350 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
351 */
352	syscall_table_start sys_call_table
353#define COMPAT(nr, native, compat) syscall nr, native
354#ifdef CONFIG_AEABI
355#include <calls-eabi.S>
356#else
357#include <calls-oabi.S>
358#endif
359#undef COMPAT
360	syscall_table_end sys_call_table
361
362/*============================================================================
363 * Special system call wrappers
364 */
365@ r0 = syscall number
366@ r8 = syscall table
367sys_syscall:
368		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
369		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
370		cmpne	scno, #NR_syscalls	@ check range
371#ifdef CONFIG_CPU_SPECTRE
372		movhs	scno, #0
373		csdb
374#endif
375		stmloia	sp, {r5, r6}		@ shuffle args
376		movlo	r0, r1
377		movlo	r1, r2
378		movlo	r2, r3
379		movlo	r3, r4
380		ldrlo	pc, [tbl, scno, lsl #2]
381		b	sys_ni_syscall
382ENDPROC(sys_syscall)
383
384sys_sigreturn_wrapper:
385		add	r0, sp, #S_OFF
386		mov	why, #0		@ prevent syscall restart handling
387		b	sys_sigreturn
388ENDPROC(sys_sigreturn_wrapper)
389
390sys_rt_sigreturn_wrapper:
391		add	r0, sp, #S_OFF
392		mov	why, #0		@ prevent syscall restart handling
393		b	sys_rt_sigreturn
394ENDPROC(sys_rt_sigreturn_wrapper)
395
396sys_statfs64_wrapper:
397		teq	r1, #88
398		moveq	r1, #84
399		b	sys_statfs64
400ENDPROC(sys_statfs64_wrapper)
401
402sys_fstatfs64_wrapper:
403		teq	r1, #88
404		moveq	r1, #84
405		b	sys_fstatfs64
406ENDPROC(sys_fstatfs64_wrapper)
407
408/*
409 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
410 * offset, we return EINVAL.
411 */
412sys_mmap2:
413		str	r5, [sp, #4]
414		b	sys_mmap_pgoff
415ENDPROC(sys_mmap2)
416
417#ifdef CONFIG_OABI_COMPAT
418
419/*
420 * These are syscalls with argument register differences
421 */
422
423sys_oabi_pread64:
424		stmia	sp, {r3, r4}
425		b	sys_pread64
426ENDPROC(sys_oabi_pread64)
427
428sys_oabi_pwrite64:
429		stmia	sp, {r3, r4}
430		b	sys_pwrite64
431ENDPROC(sys_oabi_pwrite64)
432
433sys_oabi_truncate64:
434		mov	r3, r2
435		mov	r2, r1
436		b	sys_truncate64
437ENDPROC(sys_oabi_truncate64)
438
439sys_oabi_ftruncate64:
440		mov	r3, r2
441		mov	r2, r1
442		b	sys_ftruncate64
443ENDPROC(sys_oabi_ftruncate64)
444
445sys_oabi_readahead:
446		str	r3, [sp]
447		mov	r3, r2
448		mov	r2, r1
449		b	sys_readahead
450ENDPROC(sys_oabi_readahead)
451
452/*
453 * Let's declare a second syscall table for old ABI binaries
454 * using the compatibility syscall entries.
455 */
456	syscall_table_start sys_oabi_call_table
457#define COMPAT(nr, native, compat) syscall nr, compat
458#include <calls-oabi.S>
459	syscall_table_end sys_oabi_call_table
460
461#endif
462
463