xref: /openbmc/linux/arch/arm/kernel/entry-common.S (revision eb9fe179) 
1/* SPDX-License-Identifier: GPL-2.0-only */
2/*
3 *  linux/arch/arm/kernel/entry-common.S
4 *
5 *  Copyright (C) 2000 Russell King
6 */
7
8#include <asm/assembler.h>
9#include <asm/unistd.h>
10#include <asm/ftrace.h>
11#include <asm/unwind.h>
12#include <asm/page.h>
13#ifdef CONFIG_AEABI
14#include <asm/unistd-oabi.h>
15#endif
16
17	.equ	NR_syscalls, __NR_syscalls
18
19#include "entry-header.S"
20
21saved_psr	.req	r8
22#if defined(CONFIG_TRACE_IRQFLAGS) || defined(CONFIG_CONTEXT_TRACKING_USER)
23saved_pc	.req	r9
24#define TRACE(x...) x
25#else
26saved_pc	.req	lr
27#define TRACE(x...)
28#endif
29
30	.section .entry.text,"ax",%progbits
31	.align	5
32#if !(IS_ENABLED(CONFIG_TRACE_IRQFLAGS) || IS_ENABLED(CONFIG_CONTEXT_TRACKING_USER) || \
33	IS_ENABLED(CONFIG_DEBUG_RSEQ))
34/*
35 * This is the fast syscall return path.  We do as little as possible here,
36 * such as avoiding writing r0 to the stack.  We only use this path if we
37 * have tracing, context tracking and rseq debug disabled - the overheads
38 * from those features make this path too inefficient.
39 */
40ret_fast_syscall:
41__ret_fast_syscall:
42 UNWIND(.fnstart	)
43 UNWIND(.cantunwind	)
44	disable_irq_notrace			@ disable interrupts
45	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
46	movs	r1, r1, lsl #16
47	bne	fast_work_pending
48
49	restore_user_regs fast = 1, offset = S_OFF
50 UNWIND(.fnend		)
51ENDPROC(ret_fast_syscall)
52
53	/* Ok, we need to do extra processing, enter the slow path. */
54fast_work_pending:
55	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
56	/* fall through to work_pending */
57#else
58/*
59 * The "replacement" ret_fast_syscall for when tracing, context tracking,
60 * or rseq debug is enabled.  As we will need to call out to some C functions,
61 * we save r0 first to avoid needing to save registers around each C function
62 * call.
63 */
64ret_fast_syscall:
65__ret_fast_syscall:
66 UNWIND(.fnstart	)
67 UNWIND(.cantunwind	)
68	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
69#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
70	/* do_rseq_syscall needs interrupts enabled. */
71	mov	r0, sp				@ 'regs'
72	bl	do_rseq_syscall
73#endif
74	disable_irq_notrace			@ disable interrupts
75	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing
76	movs	r1, r1, lsl #16
77	beq	no_work_pending
78 UNWIND(.fnend		)
79ENDPROC(ret_fast_syscall)
80
81	/* Slower path - fall through to work_pending */
82#endif
83
84	tst	r1, #_TIF_SYSCALL_WORK
85	bne	__sys_trace_return_nosave
86slow_work_pending:
87	mov	r0, sp				@ 'regs'
88	mov	r2, why				@ 'syscall'
89	bl	do_work_pending
90	cmp	r0, #0
91	beq	no_work_pending
92	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
93	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
94	b	local_restart			@ ... and off we go
95ENDPROC(ret_fast_syscall)
96
97/*
98 * "slow" syscall return path.  "why" tells us if this was a real syscall.
99 * IRQs may be enabled here, so always disable them.  Note that we use the
100 * "notrace" version to avoid calling into the tracing code unnecessarily.
101 * do_work_pending() will update this state if necessary.
102 */
103ENTRY(ret_to_user)
104ret_slow_syscall:
105#if IS_ENABLED(CONFIG_DEBUG_RSEQ)
106	/* do_rseq_syscall needs interrupts enabled. */
107	enable_irq_notrace			@ enable interrupts
108	mov	r0, sp				@ 'regs'
109	bl	do_rseq_syscall
110#endif
111	disable_irq_notrace			@ disable interrupts
112ENTRY(ret_to_user_from_irq)
113	ldr	r1, [tsk, #TI_FLAGS]
114	movs	r1, r1, lsl #16
115	bne	slow_work_pending
116no_work_pending:
117	asm_trace_hardirqs_on save = 0
118
119	ct_user_enter save = 0
120
121	restore_user_regs fast = 0, offset = 0
122ENDPROC(ret_to_user_from_irq)
123ENDPROC(ret_to_user)
124
125/*
126 * This is how we return from a fork.
127 */
128ENTRY(ret_from_fork)
129	bl	schedule_tail
130	cmp	r5, #0
131	movne	r0, r4
132	badrne	lr, 1f
133	retne	r5
1341:	get_thread_info tsk
135	b	ret_slow_syscall
136ENDPROC(ret_from_fork)
137
138/*=============================================================================
139 * SWI handler
140 *-----------------------------------------------------------------------------
141 */
142
143	.align	5
144#ifdef CONFIG_HARDEN_BRANCH_HISTORY
145ENTRY(vector_bhb_loop8_swi)
146	sub	sp, sp, #PT_REGS_SIZE
147	stmia	sp, {r0 - r12}
148	mov	r8, #8
1491:	b	2f
1502:	subs	r8, r8, #1
151	bne	1b
152	dsb	nsh
153	isb
154	b	3f
155ENDPROC(vector_bhb_loop8_swi)
156
157	.align	5
158ENTRY(vector_bhb_bpiall_swi)
159	sub	sp, sp, #PT_REGS_SIZE
160	stmia	sp, {r0 - r12}
161	mcr	p15, 0, r8, c7, c5, 6	@ BPIALL
162	isb
163	b	3f
164ENDPROC(vector_bhb_bpiall_swi)
165#endif
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
1733:
174 ARM(	add	r8, sp, #S_PC		)
175 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
176 THUMB(	mov	r8, sp			)
177 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
178	mrs	saved_psr, spsr			@ called from non-FIQ mode, so ok.
179 TRACE(	mov	saved_pc, lr		)
180	str	saved_pc, [sp, #S_PC]		@ Save calling PC
181	str	saved_psr, [sp, #S_PSR]		@ Save CPSR
182	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
183#endif
184	reload_current r10, ip
185	zero_fp
186	alignment_trap r10, ip, cr_alignment
187	asm_trace_hardirqs_on save=0
188	enable_irq_notrace
189	ct_user_exit save=0
190
191	/*
192	 * Get the system call number.
193	 */
194
195#if defined(CONFIG_OABI_COMPAT)
196
197	/*
198	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
199	 * value to determine if it is an EABI or an old ABI call.
200	 */
201#ifdef CONFIG_ARM_THUMB
202	tst	saved_psr, #PSR_T_BIT
203	movne	r10, #0				@ no thumb OABI emulation
204 USER(	ldreq	r10, [saved_pc, #-4]	)	@ get SWI instruction
205#else
206 USER(	ldr	r10, [saved_pc, #-4]	)	@ get SWI instruction
207#endif
208 ARM_BE8(rev	r10, r10)			@ little endian instruction
209
210#elif defined(CONFIG_AEABI)
211
212	/*
213	 * Pure EABI user space always put syscall number into scno (r7).
214	 */
215#elif defined(CONFIG_ARM_THUMB)
216	/* Legacy ABI only, possibly thumb mode. */
217	tst	saved_psr, #PSR_T_BIT		@ this is SPSR from save_user_regs
218	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
219 USER(	ldreq	scno, [saved_pc, #-4]	)
220
221#else
222	/* Legacy ABI only. */
223 USER(	ldr	scno, [saved_pc, #-4]	)	@ get SWI instruction
224#endif
225
226	/* saved_psr and saved_pc are now dead */
227
228	uaccess_disable tbl
229	get_thread_info tsk
230
231	adr	tbl, sys_call_table		@ load syscall table pointer
232
233#if defined(CONFIG_OABI_COMPAT)
234	/*
235	 * If the swi argument is zero, this is an EABI call and we do nothing.
236	 *
237	 * If this is an old ABI call, get the syscall number into scno and
238	 * get the old ABI syscall table address.
239	 */
240	bics	r10, r10, #0xff000000
241	strne	r10, [tsk, #TI_ABI_SYSCALL]
242	streq	scno, [tsk, #TI_ABI_SYSCALL]
243	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
244	ldrne	tbl, =sys_oabi_call_table
245#elif !defined(CONFIG_AEABI)
246	bic	scno, scno, #0xff000000		@ mask off SWI op-code
247	str	scno, [tsk, #TI_ABI_SYSCALL]
248	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
249#else
250	str	scno, [tsk, #TI_ABI_SYSCALL]
251#endif
252	/*
253	 * Reload the registers that may have been corrupted on entry to
254	 * the syscall assembly (by tracing or context tracking.)
255	 */
256 TRACE(	ldmia	sp, {r0 - r3}		)
257
258local_restart:
259	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
260	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
261
262	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
263	bne	__sys_trace
264
265	invoke_syscall tbl, scno, r10, __ret_fast_syscall
266
267	add	r1, sp, #S_OFF
2682:	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
269	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
270	bcs	arm_syscall
271	mov	why, #0				@ no longer a real syscall
272	b	sys_ni_syscall			@ not private func
273
274#if defined(CONFIG_OABI_COMPAT) || !defined(CONFIG_AEABI)
275	/*
276	 * We failed to handle a fault trying to access the page
277	 * containing the swi instruction, but we're not really in a
278	 * position to return -EFAULT. Instead, return back to the
279	 * instruction and re-enter the user fault handling path trying
280	 * to page it in. This will likely result in sending SEGV to the
281	 * current task.
282	 */
2839001:
284	sub	lr, saved_pc, #4
285	str	lr, [sp, #S_PC]
286	get_thread_info tsk
287	b	ret_fast_syscall
288#endif
289ENDPROC(vector_swi)
290	.ltorg
291
292	/*
293	 * This is the really slow path.  We're going to be doing
294	 * context switches, and waiting for our parent to respond.
295	 */
296__sys_trace:
297	add	r0, sp, #S_OFF
298	bl	syscall_trace_enter
299	mov	scno, r0
300	invoke_syscall tbl, scno, r10, __sys_trace_return, reload=1
301	cmp	scno, #-1			@ skip the syscall?
302	bne	2b
303	add	sp, sp, #S_OFF			@ restore stack
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__sys_trace_return:
312	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
313	mov	r0, sp
314	bl	syscall_trace_exit
315	b	ret_slow_syscall
316
317	.macro	syscall_table_start, sym
318	.equ	__sys_nr, 0
319	.type	\sym, #object
320ENTRY(\sym)
321	.endm
322
323	.macro	syscall, nr, func
324	.ifgt	__sys_nr - \nr
325	.error	"Duplicated/unorded system call entry"
326	.endif
327	.rept	\nr - __sys_nr
328	.long	sys_ni_syscall
329	.endr
330	.long	\func
331	.equ	__sys_nr, \nr + 1
332	.endm
333
334	.macro	syscall_table_end, sym
335	.ifgt	__sys_nr - __NR_syscalls
336	.error	"System call table too big"
337	.endif
338	.rept	__NR_syscalls - __sys_nr
339	.long	sys_ni_syscall
340	.endr
341	.size	\sym, . - \sym
342	.endm
343
344#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, native)
345#define __SYSCALL(nr, func) syscall nr, func
346
347/*
348 * This is the syscall table declaration for native ABI syscalls.
349 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
350 */
351	syscall_table_start sys_call_table
352#ifdef CONFIG_AEABI
353#include <calls-eabi.S>
354#else
355#include <calls-oabi.S>
356#endif
357	syscall_table_end sys_call_table
358
359/*============================================================================
360 * Special system call wrappers
361 */
362@ r0 = syscall number
363@ r8 = syscall table
364sys_syscall:
365		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
366		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
367		cmpne	scno, #NR_syscalls	@ check range
368#ifdef CONFIG_CPU_SPECTRE
369		movhs	scno, #0
370		csdb
371#endif
372		stmialo	sp, {r5, r6}		@ shuffle args
373		movlo	r0, r1
374		movlo	r1, r2
375		movlo	r2, r3
376		movlo	r3, r4
377		ldrlo	pc, [tbl, scno, lsl #2]
378		b	sys_ni_syscall
379ENDPROC(sys_syscall)
380
381sys_sigreturn_wrapper:
382		add	r0, sp, #S_OFF
383		mov	why, #0		@ prevent syscall restart handling
384		b	sys_sigreturn
385ENDPROC(sys_sigreturn_wrapper)
386
387sys_rt_sigreturn_wrapper:
388		add	r0, sp, #S_OFF
389		mov	why, #0		@ prevent syscall restart handling
390		b	sys_rt_sigreturn
391ENDPROC(sys_rt_sigreturn_wrapper)
392
393sys_statfs64_wrapper:
394		teq	r1, #88
395		moveq	r1, #84
396		b	sys_statfs64
397ENDPROC(sys_statfs64_wrapper)
398
399sys_fstatfs64_wrapper:
400		teq	r1, #88
401		moveq	r1, #84
402		b	sys_fstatfs64
403ENDPROC(sys_fstatfs64_wrapper)
404
405/*
406 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
407 * offset, we return EINVAL.
408 */
409sys_mmap2:
410		str	r5, [sp, #4]
411		b	sys_mmap_pgoff
412ENDPROC(sys_mmap2)
413
414#ifdef CONFIG_OABI_COMPAT
415
416/*
417 * These are syscalls with argument register differences
418 */
419
420sys_oabi_pread64:
421		stmia	sp, {r3, r4}
422		b	sys_pread64
423ENDPROC(sys_oabi_pread64)
424
425sys_oabi_pwrite64:
426		stmia	sp, {r3, r4}
427		b	sys_pwrite64
428ENDPROC(sys_oabi_pwrite64)
429
430sys_oabi_truncate64:
431		mov	r3, r2
432		mov	r2, r1
433		b	sys_truncate64
434ENDPROC(sys_oabi_truncate64)
435
436sys_oabi_ftruncate64:
437		mov	r3, r2
438		mov	r2, r1
439		b	sys_ftruncate64
440ENDPROC(sys_oabi_ftruncate64)
441
442sys_oabi_readahead:
443		str	r3, [sp]
444		mov	r3, r2
445		mov	r2, r1
446		b	sys_readahead
447ENDPROC(sys_oabi_readahead)
448
449/*
450 * Let's declare a second syscall table for old ABI binaries
451 * using the compatibility syscall entries.
452 */
453	syscall_table_start sys_oabi_call_table
454#undef __SYSCALL_WITH_COMPAT
455#define __SYSCALL_WITH_COMPAT(nr, native, compat)	__SYSCALL(nr, compat)
456#include <calls-oabi.S>
457	syscall_table_end sys_oabi_call_table
458
459#endif
460
461